U.S. patent application number 15/410749 was filed with the patent office on 2017-07-20 for method of preparing battery electrodes.
This patent application is currently assigned to GRST Energy Limited. The applicant listed for this patent is GRST Energy Limited. Invention is credited to Peihua Shen, Sing Hung Eric Wong.
Application Number | 20170207443 15/410749 |
Document ID | / |
Family ID | 59314233 |
Filed Date | 2017-07-20 |
United States Patent
Application |
20170207443 |
Kind Code |
A1 |
Shen; Peihua ; et
al. |
July 20, 2017 |
METHOD OF PREPARING BATTERY ELECTRODES
Abstract
Provided herein is a method for preparing a battery electrode
based on an aqueous slurry. The method disclosed herein has the
advantage that an aqueous solvent can be used in the manufacturing
process, which can save process time and facilities by avoiding the
need to handle or recycle hazardous organic solvents. Therefore,
costs are reduced by simplifying the total process. In addition,
the batteries having the electrodes prepared by the method
disclosed herein show impressive energy retention.
Inventors: |
Shen; Peihua; (Guangzhou,
CN) ; Wong; Sing Hung Eric; (Hong Kong, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GRST Energy Limited |
Hong Kong |
|
CN |
|
|
Assignee: |
GRST Energy Limited
Hong Kong
CN
|
Family ID: |
59314233 |
Appl. No.: |
15/410749 |
Filed: |
January 19, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/CN2016/109723 |
Dec 13, 2016 |
|
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15410749 |
|
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62279841 |
Jan 18, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/0409 20130101;
H01M 4/523 20130101; H01M 4/0419 20130101; H01M 4/131 20130101;
H01M 4/625 20130101; H01M 10/0525 20130101; H01M 4/483 20130101;
H01M 4/1397 20130101; H01M 4/1391 20130101; H01M 4/139 20130101;
Y02E 60/10 20130101; H01M 4/0404 20130101; H01M 4/0471 20130101;
H01M 4/5825 20130101; H01M 4/502 20130101; H01M 4/622 20130101;
H01M 2004/028 20130101; H01M 4/485 20130101; H01M 4/505 20130101;
H01M 4/525 20130101; H01M 4/1393 20130101; H01M 4/623 20130101 |
International
Class: |
H01M 4/04 20060101
H01M004/04; H01M 4/62 20060101 H01M004/62; H01M 10/0525 20060101
H01M010/0525; H01M 4/485 20060101 H01M004/485; H01M 4/131 20060101
H01M004/131; H01M 4/1391 20060101 H01M004/1391 |
Claims
1. A method of preparing a battery electrode, comprising the steps
of: 1) pre-treating a cathode material in a first aqueous solution
having a pH from about 7.0 to about 8.0 to form a first suspension;
2) drying the first suspension to obtain a pre-treated cathode
material; 3) dispersing the pre-treated cathode material, a
conductive agent, and a binder material in a second aqueous
solution to form a slurry; 4) homogenizing the slurry by a
homogenizer to obtain a homogenized slurry; 5) applying the
homogenized slurry on a current collector to form a coated film on
the current collector; and 6) drying the coated film on the current
collector to form the battery electrode; wherein the first aqueous
solution is water, alcohol, or a mixture of water and alcohol; and
wherein the cathode material is a lithium transition metal oxide or
a core-shell composite comprising a core comprising a lithium
transition metal oxide and a shell formed by coating the surface of
the core with a transition metal oxide or lithium transition metal
oxide; wherein each of the lithium transition metal oxides is
independently selected from the group consisting of LiCoO.sub.2,
LiNiO.sub.2, LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2,
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, LiV.sub.2O.sub.5, LiTiS.sub.2,
LiMoS.sub.2, LiMnO.sub.2, LiCrO.sub.2, LiMn.sub.2O.sub.4,
LiFeO.sub.2, LiFePO.sub.4, and combinations thereof; wherein each x
is independently from 0.3 to 0.8; each y is independently from 0.1
to 0.45; and each z is independently from 0 to 0.2; and wherein the
transition metal oxide is selected from the group consisting of
Fe.sub.2O.sub.3, MnO.sub.2, Al.sub.2O.sub.3, MgO, ZnO, TiO.sub.2,
La.sub.2O.sub.3, CeO.sub.2, SnO.sub.2, ZrO.sub.2, RuO.sub.2, and
combinations thereof.
2. The method of claim 1, wherein the cathode material is a
nickel-rich cathode material selected from NMC532, NMC622, NMC811,
or Li.sub.1.0Ni.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2.
3. The method of claim 1, wherein the first suspension is stirred
for a time period from about 2 minutes to about 12 hours.
4. The method of claim 1, wherein the first aqueous solution is
alcohol or a mixture of water and alcohol and wherein the alcohol
is selected from ethanol, isopropanol, methanol, n propanol,
t-butanol, or a combination thereof.
5. The method of claim 1, wherein the first suspension is dried by
a double-cone vacuum dryer, a microwave dryer, or a microwave
vacuum dryer.
6. The method of claim 1, wherein the conductive agent is selected
from the group consisting of carbon, carbon black, graphite,
expanded graphite, graphene, graphene nanoplatelets, carbon fibres,
carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon
nanotubes, activated carbon, mesoporous carbon, and combinations
thereof.
7. The method of claim 1, wherein the conductive agent is
pre-treated in a basic solution for a time period from about 30
minutes to about 2 hours and wherein the basic solution comprises a
base selected from the group consisting of H.sub.2O.sub.2, LiOH,
NaOH, KOH, NH.sub.3.H.sub.2O, Be(OH).sub.2, Mg(OH).sub.2,
Ca(OH).sub.2, Li.sub.2CO.sub.3, Na.sub.2CO.sub.3, NaHCO.sub.3,
K.sub.2CO.sub.3, KHCO.sub.3, and combinations thereof.
8. The method of claim 1, wherein the conductive agent is dispersed
in a third aqueous solution to form a second suspension prior to
step 3).
9. The method of claim 1, wherein the binder material is selected
from the group consisting of styrene-butadiene rubber (SBR),
carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF),
acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile,
poly(vinylidene fluoride)-hexafluoropropene (PVDF-HFP), latex, a
salt of alginic acid, and combinations thereof.
10. The method of claim 9, wherein the binder material is the salt
of alginic acid and wherein the salt of alginic acid comprises a
cation selected from Na, Li, K, Ca, NH.sub.4, Mg, Al, or a
combination thereof.
11. The method of claim 8, wherein the binder material is dissolved
in a fourth aqueous solution to form a resulting solution prior to
step 3).
12. The method of claim 11, wherein each of the first, the second,
third and fourth aqueous solutions independently is purified water,
pure water, de-ionized water, distilled water, or a combination
thereof.
13. The method of claim 1, wherein the homogenizer is a stirring
mixer, a planetary stirring mixer, a blender, a mill, an
ultrasonicator, a rotor-stator homogenizer, or a homogenizer.
14. The method of claim 13, wherein the ultrasonicator is a
probe-type ultrasonicator or an ultrasonic flow cell.
15. The method of claim 1, wherein the homogenized slurry is
applied on the current collector using a doctor blade coater, a
slot-die coater, a transfer coater, or a spray coater.
16. The method of claim 1, wherein the coated film is dried for a
time period from about 1 minute to about 30 minutes at a
temperature from about 45.degree. C. to about 100.degree. C.
17. The method of claim 1, wherein the cathode material is the
core-shell composite comprising the core comprising the lithium
transition metal oxide and the shell formed by coating the surface
of the core with the lithium transition metal oxide, and wherein
each of the lithium transition metal oxides in the core and the
shell is independently doped with a dopant selected from the group
consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si,
Ge, and combinations thereof.
18. The method of claim 1, wherein the cathode material is the
core-shell composite, and wherein the diameter of the core is from
about 5 .mu.m to about 45 .mu.m and the thickness of the shell is
from about 3 .mu.m to about 15 .mu.m
19. The method of claim 1, wherein the electrode is able to retain
at least about 83% of its initial storage capacity after 1,000
cycles at a rate of 1 C at room temperature in a full cell.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of the International Application No.
PCT/CN2016/109723, filed Dec. 13, 2016, which claims priority to
U.S. Provisional Patent Application No. 62/279,841, filed Jan. 18,
2016, all of which are incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0002] This invention relates to lithium-ion batteries in the
application of sustainable energy area. More particularly, this
invention relates to the use of aqueous-based slurries for
preparing battery electrodes.
BACKGROUND OF THE INVENTION
[0003] Lithium-ion batteries (LIBs) have attracted extensive
attention in the past two decades for a wide range of applications
in portable electronic devices such as cellular phones and laptop
computers. Due to rapid market development of electric vehicles
(EV) and grid energy storage, high-performance, low-cost LIBs are
currently offering one of the most promising options for
large-scale energy storage devices.
[0004] In general, a lithium ion battery includes a separator, a
cathode and an anode. Currently, electrodes are prepared by
dispersing fine powders of an active battery electrode material, a
conductive agent, and a binder material in an appropriate solvent.
The dispersion can be coated onto a current collector such as a
copper or aluminum metal foil, and then dried at an elevated
temperature to remove the solvent. Sheets of the cathode and anode
are subsequently stacked or rolled with the separator separating
the cathode and anode to form a battery.
[0005] Polyvinylidene fluoride (PVDF) has been the most widely used
binder materials for both cathode and anode electrodes. Compared to
non-PVDF binder materials, PVDF provides a good electrochemical
stability and high adhesion to the electrode materials and current
collectors. However, PVDF can only dissolve in some specific
organic solvents such as N-Methyl-2-pyrrolidone (NMP) which
requires specific handling, production standards and recycling of
the organic solvents in an environmentally-friendly way. This will
incur significant costs in the manufacturing process.
[0006] The use of aqueous solutions instead of organic solvents is
preferred for environmental and handling reasons and therefore
water-based slurries have been considered. Water soluble binders
such as carboxymethyl cellulose (CMC) and styrene-butadiene rubber
(SBR) have been attempted. However, CMC and SBR are generally
limited to anode applications.
[0007] U.S. Pat. No. 8,956,688 B2 describes a method of making a
battery electrode. The method comprises measuring the zeta
potential of the active electrode material and the conductive
additive material; selecting a cationic or anionic dispersant based
on the zeta potential; determining the isoelectric point (IEP) of
the active electrode material and the conductive additive material;
dispersing an active electrode material and a conductive additive
in water with at least one dispersant to create a mixed dispersion;
treating a surface of a current collector to raise the surface
energy of the surface to at least the surface tension of the mixed
dispersion; depositing the dispersed active electrode material and
conductive additive on a current collector; and heating the coated
surface to remove water from the coating. However, the method is
complicated, involving measurements of the zeta potential of the
active electrode material and the conductive additive material, and
isoelectric point (IEP) of the active electrode material and the
conductive additive material. Furthermore, an additional surface
treatment step for treating the surface of the current collector is
required in order to enhance the capacity retention.
[0008] U.S. Pat. No. 8,092,557 B2 describes a method of making an
electrode for a rechargeable lithium ion battery using a
water-based slurry having a pH between 7.0 and 11.7, wherein the
electrode includes an electro-active material, a
(polystyrenebutadiene rubber)-poly (acrylonitrile-co-acrylamide)
polymer, and a conductive additive. However, this method does not
provide any data for evaluating the electrochemical performance of
the electrodes prepared by this method.
[0009] U.S. Patent Application No. 2013/0034651 A1 describes a
slurry for the manufacture of an electrode, wherein the slurry
comprises a combination of at least three of polyacrylic acid
(PAA), carboxymethyl cellulose (CMC), styrene-butadiene rubber
(SBR) and polyvinylidene fluoride (PVDF) in an aqueous solution and
an electrochemically activateable compound. However, the slurry for
preparing the cathode electrode comprises acetone or other organic
solvents such as NMP and DMAC.
[0010] In view of the above, there is always a need to develop a
method for preparing cathode and anode electrodes for lithium-ion
battery using a simple, inexpensive and environmentally friendly
method.
SUMMARY OF THE INVENTION
[0011] The aforementioned needs are met by various aspects and
embodiments disclosed herein.
[0012] In one aspect, provided herein is a method of preparing a
battery electrode, comprising the steps of:
[0013] 1) pre-treating an active battery electrode material in a
first aqueous solution having a pH from about 2.0 to about 7.5 to
form a first suspension;
[0014] 2) drying the first suspension to obtain a pre-treated
active battery electrode material;
[0015] 3) dispersing the pre-treated active battery electrode
material, a conductive agent, and a binder material in a second
aqueous solution to form a slurry;
[0016] 4) homogenizing the slurry by a homogenizer to obtain a
homogenized slurry;
[0017] 5) applying the homogenized slurry on a current collector to
form a coated film on the current collector; and
[0018] 6) drying the coated film on the current collector to form
the battery electrode.
[0019] In certain embodiments, the active battery electrode
material is a cathode material, wherein the cathode material is
selected from the group consisting of LiCoO.sub.2, LiNiO.sub.2,
LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2,
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, LiV.sub.2O.sub.5, LiTiS.sub.2,
LiMoS.sub.2, LiMnO.sub.2, LiCrO.sub.2, LiMn.sub.2O.sub.4,
LiFeO.sub.2, LiFePO.sub.4, and combinations thereof, wherein each x
is independently from 0.3 to 0.8; each y is independently from 0.1
to 0.45; and each z is independently from 0 to 0.2.
[0020] In some embodiments, the pH of the first aqueous solution is
at a range from about 4 to about 7 and the first suspension is
stirred for a time period from about 2 minutes to about 12 hours.
In further embodiments, the first aqueous solution comprises one or
more acids selected from the group consisting of H.sub.2SO.sub.4,
HNO.sub.3, H.sub.3PO.sub.4, HCOOH, CH.sub.3COOH,
H.sub.3C.sub.6H.sub.5O.sub.7, H.sub.2C.sub.2O.sub.4,
C.sub.6H.sub.12O.sub.7, C.sub.4H.sub.6O.sub.5, and combinations
thereof.
[0021] In certain embodiments, the first aqueous solution further
comprises ethanol, isopropanol, methanol, acetone, n-propanol,
t-butanol, or a combination thereof.
[0022] In some embodiments, the first suspension is dried by a
double-cone vacuum dryer, a microwave dryer, or a microwave vacuum
dryer.
[0023] In certain embodiments, the conductive agent is selected
from the group consisting of carbon, carbon black, graphite,
expanded graphite, graphene, graphene nanoplatelets, carbon fibres,
carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon
nanotubes, activated carbon, mesoporous carbon, and combinations
thereof.
[0024] In some embodiments, the conductive agent is pre-treated in
an alkaline solution or a basic solution for a time period from
about 30 minutes to about 2 hours, wherein the alkaline solution or
basic solution comprises a base selected from the group consisting
of H.sub.2O.sub.2, LiOH, NaOH, KOH, NH.sub.3.H.sub.2O,
Be(OH).sub.2, Mg(OH).sub.2, Ca(OH).sub.2, Li.sub.2CO.sub.3,
Na.sub.2CO.sub.3, NaHCO.sub.3, K.sub.2CO.sub.3, KHCO.sub.3, and
combinations thereof.
[0025] In certain embodiments, the conductive agent is dispersed in
a third aqueous solution to form a second suspension prior to step
3).
[0026] In some embodiments, the binder material is selected from
the group consisting of styrene-butadiene rubber (SBR),
carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF),
acrylonitrile copolymer, polyacrylic acid (PAA), polyacrylonitrile,
poly(vinylidene fluoride)-hexafluoropropene (PVDF-HFP), latex, a
salt of alginic acid, and combinations thereof. In further
embodiments, the salt of alginic acid comprises a cation selected
from Na, Li, K, Ca, NH.sub.4, Mg, Al, or a combination thereof.
[0027] In some embodiments, the binder material is dissolved in a
fourth aqueous solution to form a resulting solution prior to step
3).
[0028] In certain embodiments, each of the first, second, third and
fourth aqueous solutions independently is purified water, pure
water, de-ionized water, distilled water, or a combination
thereof.
[0029] In some embodiments, the slurry or homogenized slurry
further comprises a dispersing agent selected from the group
consisting of ethanol, isopropanol, n-propanol, t-butanol,
n-butanol, lithium dodecyl sulfate, trimethylhexadecyl ammonium
chloride, alcohol ethoxylate, nonylphenol ethoxylate, sodium
dodecylbenzene sulfonate, sodium stearate, and combinations
thereof.
[0030] In certain embodiments, the homogenizer is a stirring mixer,
a blender, a mill, an ultrasonicator, a rotor-stator homogenizer,
or a high pressure homogenizer.
[0031] In some embodiments, the ultrasonicator is a probe-type
ultrasonicator or an ultrasonic flow cell.
[0032] In certain embodiments, the ultrasonicator is operated at a
power density from about 10 W/L to about 100 W/L, or from about 20
W/L to about 40 W/L.
[0033] In some embodiments, the homogenized slurry is applied on
the current collector using a doctor blade coater, a slot-die
coater, a transfer coater, or a spray coater.
[0034] In certain embodiments, each of the current collectors of
the positive and negative electrodes is independently stainless
steel, titanium, nickel, aluminum, copper or
electrically-conductive resin. In certain embodiments, the current
collector of the positive electrode is an aluminum thin film. In
some embodiments, the current collector of the negative electrode
is a copper thin film.
[0035] In some embodiments, the coated film is dried for a time
period from about 1 minute to about 30 minutes, or from about 2
minutes to about 10 minutes at a temperature from about 45.degree.
C. to about 100.degree. C., or from about 55.degree. C. to about
75.degree. C.
[0036] In certain embodiments, the coated film is dried by a
conveyor hot air drying oven, a conveyor resistance drying oven, a
conveyor inductive drying oven, or a conveyor microwave drying
oven.
[0037] In some embodiments, the conveyor moves at a speed from
about 2 meter/minute to about 30 meter/minute, from about 2
meter/minute to about 25 meter/minute, from about 2 meter/minute to
about 20 meter/minute, from about 2 meter/minute to about 16
meter/minute, from about 3 meter/minute to about 30 meter/minute,
from about 3 meter/minute to about 20 meter/minute, or from about 3
meter/minute to about 16 meter/minute.
[0038] In certain embodiments, the active battery electrode
material is an anode material, wherein the anode material is
selected from the group consisting of natural graphite particulate,
synthetic graphite particulate, Sn particulate,
Li.sub.4Ti.sub.5O.sub.12 particulate, Si particulate, Si--C
composite particulate, and combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 depicts an embodiment of the method disclosed
herein.
[0040] FIG. 2 depicts a SEM image of the surface morphology of
Example 1, an embodiment of the coated cathode electrode disclosed
herein.
[0041] FIG. 3 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 2.
[0042] FIG. 4 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 4.
[0043] FIG. 5 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 6.
[0044] FIG. 6 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 8.
[0045] FIG. 7 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 10.
[0046] FIG. 8 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 12.
[0047] FIG. 9 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 14.
[0048] FIG. 10 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 15.
[0049] FIG. 11 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 16.
[0050] FIG. 12 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 17.
[0051] FIG. 13 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Example 18.
[0052] FIG. 14 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 1.
[0053] FIG. 15 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 2.
[0054] FIG. 16 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 3.
[0055] FIG. 17 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 4.
[0056] FIG. 18 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 5.
[0057] FIG. 19 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 6.
[0058] FIG. 20 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 7.
[0059] FIG. 21 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 8.
[0060] FIG. 22 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 9.
[0061] FIG. 23 depicts cycling performance of an electrochemical
cell containing a cathode and an anode prepared by the method
described in Comparative Example 10.
DETAILED DESCRIPTION OF THE INVENTION
[0062] Provided herein is a method of preparing a battery
electrode, comprising the steps of:
[0063] 1) pre-treating an active battery electrode material in a
first aqueous solution having a pH from about 2.0 to about 7.5 to
form a first suspension;
[0064] 2) drying the first suspension to obtain a pre-treated
active battery electrode material;
[0065] 3) dispersing the pre-treated active battery electrode
material, a conductive agent, and a binder material in a second
aqueous solution to form a slurry;
[0066] 4) homogenizing the slurry by a homogenizer to obtain a
homogenized slurry;
[0067] 5) applying the homogenized slurry on a current collector to
form a coated film on the current collector; and
[0068] 6) drying the coated film on the current collector to form
the battery electrode.
[0069] The term "electrode" refers to a "cathode" or an
"anode."
[0070] The term "positive electrode" is used interchangeably with
cathode. Likewise, the term "negative electrode" is used
interchangeably with anode.
[0071] The term "acid" includes any molecule or ion that can donate
a hydrogen ion to another substance, and/or contain completely or
partially displaceable H.sup.+ ions. Some non-limiting examples of
suitable acids include inorganic acids and organic acids. Some
non-limiting examples of the inorganic acid include hydrochloric
acid, nitric acid, phosphoric acid, sulfuric acid, boric acid,
hydrofluoric acid, hydrobromic acid, perchloric acid, hydroiodic
acid, and combinations thereof. Some non-limiting examples of the
organic acids include acetic acid, lactic acid, oxalic acid, citric
acid, uric acid, trifluoroacetic acid, methanesulfonic acid, formic
acid, propionic acid, butyric acid, valeric acid, gluconic acid,
malic acid, caproic acid, and combinations thereof.
[0072] The term "acidic solution" refers to a solution of a soluble
acid, having a pH lower than 7.0, lower than 6.5, lower than 6.0,
lower than 5.0, lower than 4.0, lower than 3.0, or lower than 2.0.
In some embodiments, the pH is greater than 6.0, greater than 5.0,
greater than 4.0, greater than 3.0, or greater than 2.0.
[0073] The term "pre-treating" as used herein refers to an act of
improving or altering the properties of a material, or removing any
contaminants in a material by acting upon with some agents, or an
act of suspending a material in some solvents.
[0074] The term "dispersing" as used herein refers to an act of
distributing a chemical species or a solid more or less evenly
throughout a fluid.
[0075] The term "binder material" refers to a chemical or a
substance that can be used to hold the active battery electrode
material and conductive agent in place.
[0076] The term "homogenizer" refers to an equipment that can be
used for homogenization of materials. The term "homogenization"
refers to a process of reducing a substance or material to small
particles and distributing it uniformly throughout a fluid. Any
conventional homogenizers can be used for the method disclosed
herein. Some non-limiting examples of the homogenizer include
stirring mixers, blenders, mills (e.g., colloid mills and sand
mills), ultrasonicators, atomizers, rotor-stator homogenizers, and
high pressure homogenizers.
[0077] The term "ultrasonicator" refers to an equipment that can
apply ultrasound energy to agitate particles in a sample. Any
ultrasonicator that can disperse the slurry disclosed herein can be
used herein. Some non-limiting examples of the ultrasonicator
include an ultrasonic bath, a probe-type ultrasonicator, and an
ultrasonic flow cell.
[0078] The term "ultrasonic bath" refers to an apparatus through
which the ultrasonic energy is transmitted via the container's wall
of the ultrasonic bath into the liquid sample.
[0079] The term "probe-type ultrasonicator" refers to an ultrasonic
probe immersed into a medium for direct sonication. The term
"direct sonication" means that the ultrasound is directly coupled
into the processing liquid.
[0080] The term "ultrasonic flow cell" or "ultrasonic reactor
chamber" refers to an apparatus through which sonication processes
can be carried out in a flow-through mode. In some embodiments, the
ultrasonic flow cell is in a single-pass, multiple-pass or
recirculating configuration.
[0081] The term "planetary mixer" refers to an equipment that can
be used to mix or blend different materials for producing a
homogeneous mixture, which consists of a single or double blade
with a high speed dispersion blade. The rotational speed can be
expressed in unit of rotations per minute (rpm) which refers to the
number of rotations that a rotating body completes in one
minute.
[0082] The term "applying" as used herein in general refers to an
act of laying or spreading a substance on a surface.
[0083] The term "current collector" refers to a support for coating
the active battery electrode material and a chemically inactive
high electron conductor for keeping an electric current flowing to
electrodes during discharging or charging a secondary battery.
[0084] The term "room temperature" refers to indoor temperatures
from about 18.degree. C. to about 30.degree. C., e.g., 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.degree. C. In some
embodiments, room temperature refers to a temperature of about
20.degree. C. +/-1.degree. C. or +/-2.degree. C. or +/-3.degree. C.
In other embodiments, room temperature refers to a temperature of
about 22.degree. C. or about 25.degree. C.
[0085] The term "C rate" refers to the charging or discharging rate
of a cell or battery, expressed in terms of its total storage
capacity in Ah or mAh. For example, a rate of 1 C means utilization
of all of the stored energy in one hour; a 0.1 C means utilization
of 10% of the energy in one hour and the full energy in 10 hours;
and a 5 C means utilization of the full energy in 12 minutes.
[0086] The term "ampere-hour (Ah)" refers to a unit used in
specifying the storage capacity of a battery. For example, a
battery with 1 Ah capacity can supply a current of one ampere for
one hour or 0.5 A for two hours, etc. Therefore, 1 Ampere-hour (Ah)
is the equivalent of 3600 coulombs of electrical charge. Similarly,
the term "miniampere-hour (mAh)" also refers to a unit of the
storage capacity of a battery and is 1/1,000 of an ampere-hour.
[0087] The term "doctor blading" refers to a process for
fabrication of large area films on rigid or flexible substrates. A
coating thickness can be controlled by an adjustable gap width
between a coating blade and a coating surface, which allows the
deposition of variable wet layer thicknesses.
[0088] The term "transfer coating" or "roll coating" refers to a
process for fabrication of large area films on rigid or flexible
substrates. A slurry is applied on the substrate by transferring a
coating from the surface of a coating roller with pressure. A
coating thickness can be controlled by an adjustable gap width
between a metering blade and a surface of the coating roller, which
allows the deposition of variable wet layer thicknesses. In a
metering roll system, the thickness of the coating is controlled by
adjusting the gap between a metering roller and a coating
roller.
[0089] The term "battery cycle life" refers to the number of
complete charge/discharge cycles a battery can perform before its
nominal capacity falls below 80% of its initial rated capacity.
[0090] The term "major component" of a composition refers to the
component that is more than 50%, more than 55%, more than 60%, more
than 65%, more than 70%, more than 75%, more than 80%, more than
85%, more than 90%, or more than 95% by weight or volume, based on
the total weight or volume of the composition.
[0091] The term "minor component" of a composition refers to the
component that is less than 50%, less than 45%, less than 40%, less
than 35%, less than 30%, less than 25%, less than 20%, less than
15%, less than 10%, or less than 5% by weight or volume, based on
the total weight or volume of the composition.
[0092] The term "relatively slow rate" as used herein refers to the
loss of solvent from the wet solid in the coated film over a
relatively long period of time. In some embodiments, the time
required for drying the coated film of a designated coating
composition at a relatively slow rate is from about 5 minutes to
about 20 minutes.
[0093] The term "relatively quick drying rate" as used herein
refers to the loss of solvent from the wet solid in the coated film
over a relatively short period of time. In some embodiments, the
time required for drying the coated film of a designated coating
composition at a relatively quick drying rate is from about 1
minute to about 5 minutes.
[0094] In the following description, all numbers disclosed herein
are approximate values, regardless whether the word "about" or
"approximate" is used in connection therewith. They may vary by 1
percent, 2 percent, 5 percent, or, sometimes, 10 to 20 percent.
Whenever a numerical range with a lower limit, R.sup.L, and an
upper limit, R.sup.U, is disclosed, any number falling within the
range is specifically disclosed. In particular, the following
numbers within the range are specifically disclosed:
R=R.sup.L+k*(R.sup.U-R.sup.L), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50
percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed.
[0095] FIG. 1 shows an embodiment of the method disclosed herein,
in which a first suspension is prepared by pre-treating an active
battery electrode material in a first aqueous solution having a pH
from about 2.0 to about 7.5 to form a first suspension. The first
suspension is then dried to obtain a pre-treated active battery
electrode material. A slurry is prepared by mixing the pre-treated
active battery electrode material, a conductive agent, and a binder
material in a second aqueous solution. Further components may be
added. The slurry is then homogenized by a homogenizer to obtain a
homogenized slurry. A current collector is coated with the
homogenized slurry, and the coated collector is then dried to form
the battery electrode.
[0096] In certain embodiments, the first suspension is prepared by
pre-treating an active battery electrode material in a first
aqueous solution having a pH from about 2.0 to about 7.5.
[0097] Any temperature that can pre-treat the active battery
electrode material can be used herein. In some embodiments, the
active battery electrode material can be added to the stirring
first aqueous solution at about 14.degree. C., about 16.degree. C.,
about 18.degree. C., about 20.degree. C., about 22.degree. C.,
about 24.degree. C., or about 26.degree. C. In certain embodiments,
the pre-treating process can be performed with heating at a
temperature from about 30.degree. C. to about 80.degree. C., from
about 35.degree. C. to about 80.degree. C., from about 40.degree.
C. to about 80.degree. C., from about 45.degree. C. to about
80.degree. C., from about 50.degree. C. to about 80.degree. C.,
from about 55.degree. C. to about 80.degree. C., from about
55.degree. C. to about 70.degree. C., from about 45.degree. C. to
about 85.degree. C., or from about 45.degree. C. to about
90.degree. C. In some embodiments, the pre-treating process can be
performed at a temperature below 30.degree. C., below 25.degree.
C., below 22.degree. C., below 20.degree. C., below 15.degree. C.,
or below 10.degree. C.
[0098] In some embodiments, the active battery electrode material
is a cathode material, wherein the cathode material is selected
from the group consisting of LiCoO.sub.2, LiNiO.sub.2,
LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2,
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, LiV.sub.2O.sub.5, LiTiS.sub.2,
LiMoS.sub.2, LiMnO.sub.2, LiCrO.sub.2, LiMn.sub.2O.sub.4,
LiFeO.sub.2, LiFePO.sub.4, and combinations thereof, wherein each x
is independently from 0.3 to 0.8; each y is independently from 0.1
to 0.45; and each z is independently from 0 to 0.2. In certain
embodiments, the cathode material is selected from the group
consisting of LiCoO.sub.2, LiNiO.sub.2, LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2 (NMC),
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, LiV.sub.2O.sub.5, LiTiS.sub.2,
LiMoS.sub.2, LiMnO.sub.2, LiCrO.sub.2, LiMn.sub.2O.sub.4,
LiFeO.sub.2, LiFePO.sub.4, and combinations thereof, wherein each x
is independently from 0.4 to 0.6; each y is independently from 0.2
to 0.4; and each z is independently from 0 to 0.1. In other
embodiments, the cathode material is not LiCoO.sub.2, LiNiO.sub.2,
LiV.sub.2O.sub.5, LiTiS.sub.2, LiMoS.sub.2, LiMnO.sub.2,
LiCrO.sub.2, LiMn.sub.2O.sub.4, LiFeO.sub.2, or LiFePO.sub.4. In
further embodiments, the cathode material is not
LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2, or
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, wherein each x is independently
from 0.3 to 0.8; each y is independently from 0.1 to 0.45; and each
z is independently from 0 to 0.2.
[0099] In certain embodiments, the cathode material is doped with a
dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg,
Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In
some embodiments, the dopant is not Fe, Ni, Mn, Mg, Zn, Ti, La, Ce,
Ru, Si, or Ge. In certain embodiments, the dopant is not Al, Sn, or
Zr.
[0100] In some embodiments, the cathode material comprises or is a
core-shell composite comprising a core comprising a lithium
transition metal oxide and a shell formed by coating the surface of
the core with a transition metal oxide. In certain embodiments, the
lithium transition metal oxide is selected from the group
consisting of LiCoO.sub.2, LiNiO.sub.2, LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2,
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, LiV.sub.2O.sub.5, LiTiS.sub.2,
LiMoS.sub.2, LiMnO.sub.2, LiCrO.sub.2, LiMn.sub.2O.sub.4,
LiFeO.sub.2, LiFePO.sub.4, and combinations thereof, wherein each x
is independently from 0.3 to 0.8; each y is independently from 0.1
to 0.45; and each z is independently from 0 to 0.2. In some
embodiments, the transition metal oxide is selected from the group
consisting of Fe.sub.2O.sub.3, MnO.sub.2, Al.sub.2O.sub.3, MgO,
ZnO, TiO.sub.2, La.sub.2O.sub.3, CeO.sub.2, SnO.sub.2, ZrO.sub.2,
RuO.sub.2, and combinations thereof.
[0101] In certain embodiments, the cathode material comprises or is
a core-shell composite having a core and shell structure, wherein
the core and the shell each independently comprise a lithium
transition metal oxide selected from the group consisting of
LiCoO.sub.2, LiNiO.sub.2, LiNi.sub.xMn.sub.yO.sub.2,
Li.sub.1+zNi.sub.xMn.sub.yCo.sub.1-x-yO.sub.2,
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, LiV.sub.2O.sub.5, LiTiS.sub.2,
LiMoS.sub.2, LiMnO.sub.2, LiCrO.sub.2, LiMn.sub.2O.sub.4,
LiFeO.sub.2, LiFePO.sub.4, and combinations thereof, wherein each x
is independently from 0.3 to 0.8; each y is independently from 0.1
to 0.45; and each z is independently from 0 to 0.2. In other
embodiments, the core and the shell each independently comprise two
or more lithium transition metal oxides. The two or more lithium
transition metal oxides in the core and the shell may be the same,
or may be different or partially different. In some embodiments,
the two or more lithium transition metal oxides are uniformly
distributed over the core. In certain embodiments, the two or more
lithium transition metal oxides are not uniformly distributed over
the core.
[0102] In some embodiments, each of the lithium transition metal
oxides in the core and the shell is independently doped with a
dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg,
Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In
certain embodiments, the core and the shell each independently
comprise two or more doped lithium transition metal oxides. In some
embodiments, the two or more doped lithium transition metal oxides
are uniformly distributed over the core. In certain embodiments,
the two or more doped lithium transition metal oxides are not
uniformly distributed over the core.
[0103] In some embodiments, the diameter of the core is from about
5 .mu.m to about 45 .mu.m, from about 5 .mu.m to about 35 .mu.m,
from about 5 .mu.m to about 25 .mu.m, from about 10 .mu.m to about
40 .mu.m, or from about 10 .mu.m to about 35 .mu.m. In certain
embodiments, the thickness of the shell is from about 3 .mu.m to
about 15 .mu.m, from about 15 .mu.m to about 45 .mu.m, from about
15 .mu.m to about 30 .mu.m, from about 15 .mu.m to about 25 .mu.m,
from about 20 .mu.m to about 30 .mu.m, or from about 20 .mu.m to
about 35 .mu.m. In certain embodiments, the diameter or thickness
ratio of the core and the shell are in the range of 15:85 to 85:15,
25:75 to 75:25, 30:70 to 70:30, or 40:60 to 60:40. In certain
embodiments, the volume or weight ratio of the core and the shell
is 80:20, 70:30, 60:40, 50:50, 40:60, or 30:70.
[0104] In certain embodiments, the first aqueous solution is a
solution containing water as the major component and a volatile
solvent, such as alcohols, lower aliphatic ketones, lower alkyl
acetates or the like, as the minor component in addition to water.
In certain embodiments, the amount of water is at least 50%, at
least 55%, at least 60%, at least 65%, at least 70%, at least 75%,
at least 80%, at least 85%, at least 90%, or at least 95% to the
total amount of water and solvents other than water. In some
embodiments, the amount of water is at most 55%, at most 60%, at
most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at
most 90%, or at most 95% to the total amount of water and solvents
other than water. In some embodiments, the first aqueous solution
consists solely of water, that is, the proportion of water in the
first aqueous solution is 100 vol. %.
[0105] Any water-miscible solvents can be used as the minor
component. Some non-limiting examples of the minor component (i.e.,
solvents other than water) include alcohols, lower aliphatic
ketones, lower alkyl acetates and combinations thereof. Some
non-limiting examples of the alcohol include C.sub.2-C.sub.4
alcohols, such as methanol, ethanol, isopropanol, n-propanol,
butanol, and combinations thereof. Some non-limiting examples of
the lower aliphatic ketones include acetone, dimethyl ketone, and
methyl ethyl ketone. Some non-limiting examples of the lower alkyl
acetates include ethyl acetate, isopropyl acetate, and propyl
acetate.
[0106] In certain embodiments, the volatile solvent or the minor
component is methyl ethyl ketone, ethanol, ethyl acetate or a
combination thereof.
[0107] In some embodiments, the first aqueous solution is a mixture
of water and one or more water-miscible minor component. In certain
embodiments, the first aqueous solution is a mixture of water and a
minor component selected from ethanol, isopropanol, n-propanol,
t-butanol, n-butanol, and combinations thereof. In some
embodiments, the volume ratio of water and the minor component is
from about 51:49 to about 100:1.
[0108] In certain embodiments, the first aqueous solution is water.
Some non-limiting examples of water include tap water, bottled
water, purified water, pure water, distilled water, de-ionized
water, D.sub.2O, or a combination thereof. In some embodiments, the
first aqueous solution is de-ionized water. In certain embodiments,
the first aqueous solution is free of alcohol, aliphatic ketone,
alkyl acetate, or a combination thereof.
[0109] In some embodiments, the first aqueous solution is acidic,
slightly alkaline, or neutral, and has a pH anywhere within the
range of about 2.0 to about 8.0. In certain embodiments, the pH of
the first aqueous solution is from about 2.0 to about 7.5, from
about 3.0 to about 7.5, from about 4.0 to about 7.5, from about 4.0
to about 7.0, from about 5.0 to about 7.5, from about 6.0 to about
7.5, or from about 6.0 to about 7.0. In some embodiments, the pH of
the first aqueous solution is about 7.0, about 6.5, about 6.0,
about 5.5, about 5.0, or about 4.0. In other embodiments, the pH of
the first aqueous solution is from about 2 to about 7, from about 2
to about 6, from about 2 to about 5, or from about 2 to about 4. In
some embodiments, the pH of the first aqueous solution is less than
about 7, less than about 6, less than about 5, less than about 4,
or less than about 3.
[0110] In certain embodiments, the first aqueous solution comprises
one or more acids selected from the group consisting of inorganic
acids, organic acids, and combinations thereof.
[0111] In some embodiments, the acid is a mixture of one or more
inorganic acids and one or more organic acids, wherein a weight
ratio of the one or more inorganic acids to the one or more organic
acids is from about 10/1 to about 1/10, from about 8/1 to about
1/8, from about 6/1 to about 1/6, or from about 4/1 to about
1/4.
[0112] In certain embodiments, the one or more inorganic acids are
selected from the group consisting of hydrochloric acid, nitric
acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric
acid, hydrobromic acid, perchloric acid, hydroiodic acid, and
combinations thereof. In further embodiments, the one or more
inorganic acids are sulfuric acid, hydrochloric acid, hydrobromic
acid, nitric acid, phosphoric acid, and combinations thereof. In
still further embodiments, the inorganic acid is hydrochloric acid.
In some embodiments, the acid is free of inorganic acid such as
hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid,
boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid,
or hydroiodic acid.
[0113] In some embodiments, the one or more organic acids are
selected from the group consisting of acetic acid, lactic acid,
oxalic acid, citric acid, uric acid, trifluoroacetic acid,
methanesulfonic acid, formic acid, propionic acid, butyric acid,
valeric acid, gluconic acid, malic acid, caproic acid, and
combinations thereof. In further embodiments, the one or more
organic acids are formic acid, acetic acid, propionic acid, and
combinations thereof. In still further embodiments, the organic
acid is acetic acid. In some embodiments, the acid is free of
organic acid such as acetic acid, lactic acid, oxalic acid, citric
acid, uric acid, trifluoroacetic acid, methanesulfonic acid, formic
acid, propionic acid, butyric acid, valeric acid, gluconic acid,
malic acid, or caproic acid.
[0114] The pH of the first aqueous solution is maintained during
the addition of the active battery electrode material at a range
from about 4.0 to about 7.5 by addition of one or more acids as a
pH adjuster. The choice of the pH adjuster is not critical. Any
suitable organic or inorganic acid may be used. In some
embodiments, the pH adjuster is an acid selected from the group
consisting of an inorganic acid, an organic acid, and combinations
thereof. The pH can be monitored by a pH measuring device such as
pH sensors. In some embodiments, more than one pH sensors are used
for monitoring the pH value.
[0115] When the cathode material having a core-shell structure is
exposed to an aqueous acidic solution, the shell of the core-shell
composite will be damaged by the acidic environment, thereby
affecting the performance of the cathode material. In some
embodiments, the shell of the core-shell composite is very thin and
has a thickness from about 3 .mu.m to about 15 .mu.m. The thin
layer is very fragile and can therefore easily be damaged. In
certain embodiments, the first aqueous solution is slightly
alkaline or neutral, and has a pH anywhere within the range from
about 7.0 to about 7.5 or from about 7.0 to about 8.0. In some
embodiments, the core-shell composite is pre-treated in water,
alcohol, or a mixture of water and alcohol. In one embodiment, the
first aqueous solution is water and contaminants such as dirt and
water-soluble impurities can be removed from the surface of the
core-shell composite without damaging the shell. In another
embodiment, the first aqueous solution is an alcohol or a mixture
of water and alcohol, and contaminants such as dirt, organic
compounds such as grease and oil, and water-soluble impurities can
be removed from the surface of the core-shell composite without
damaging the shell. In further embodiments, the alcohol is selected
from the group consisting of methanol, ethanol, propanol, butanol,
pentanol, and isomers and combinations thereof.
[0116] The use of the aqueous acidic solution for pre-treating the
Ni-rich cathode material such as NMC532, NMC622, or NMC811 may
result in defects on the surface of the cathode material. These
defects in turn cause mild to severe degradation of electrochemical
performance of an electrochemical cell. Acid pretreatment may also
lead to surface irregularities of the cathode material, which in
turn cause reduced cell performance or even cell failure. In some
embodiments, the Ni-rich cathode material is pre-treated in a
slightly alkaline or neutral environment. In certain embodiments,
the first aqueous solution has a pH anywhere within the range from
about 7.0 to about 7.5 or from about 7.0 to about 8.0. In some
embodiments, the Ni-rich cathode material is pre-treated in water,
alcohol or a mixture of water and alcohol. In other embodiments,
the Ni-rich cathode material is pre-treated in a slightly acidic
environment having a pH from about 6.0 to about 7.0. In further
embodiments, the first aqueous solution comprises an acid in an
amount from about 0.001 wt. % to about 0.01 wt. %. In other
embodiments, the first aqueous solution comprises an acid in an
amount of less than about 0.01 wt. %. Therefore, contaminants can
be removed from the surface of the Ni-rich cathode material without
creating surface defects for the cathode material.
[0117] In some embodiments, after adding the active battery
electrode material to the first aqueous solution, the mixture can
be further stirred for a time period sufficient for forming the
first suspension. In certain embodiments, the time period is from
about 5 minutes to about 2 hours, from about 5 minutes to about 1.5
hours, from about 5 minutes to about 1 hour, from about 5 minutes
to about 30 minutes, from about 5 minutes to about 15 minutes, from
about 10 minutes to about 2 hours, from about 10 minutes to about
1.5 hours, from about 10 minutes to about 1 hour, from about 10
minutes to about 30 minutes, from about 15 minutes to about 1 hour,
or from about 30 minutes to about 1 hour.
[0118] In certain embodiments, the active battery electrode
material is an anode material, wherein the anode material is
selected from the group consisting of natural graphite particulate,
synthetic graphite particulate, Sn (tin) particulate,
Li.sub.4Ti.sub.5O.sub.12 particulate, Si (silicon) particulate,
Si--C composite particulate, and combinations thereof.
[0119] In some embodiments, the first suspension can be dried to
obtain a pre-treated active battery electrode material. Any dryer
that can dry a suspension can be used herein. In some embodiments,
the drying process is performed by a double-cone vacuum dryer, a
microwave dryer, or a microwave vacuum dryer.
[0120] Conventionally, metal material is not suggested to use
microwave dryer to dry as the characteristic of metal material can
reflect microwave frequency. To our surprise, when drying is
performed by a microwave dryer or microwave vacuum dryer, the
cathode material can be effectively dried and drying time can be
significantly shortened, thereby lowering operational costs. In
some embodiments, the drying time is from about 3 minutes to about
25 minutes. Furthermore, drying the cathode material at high
temperatures for long time may result in undesirable decomposition
of the cathode material, and alter oxidation states of the cathode
material. The cathode material having high nickel and/or manganese
content is particularly temperature sensitive. As such, the
positive electrode may have reduced performance. Therefore,
decreased drying times significantly reduce or eliminate
degradation of the cathode material. In certain embodiments, the
dryer is a microwave dryer or a microwave vacuum dryer. In some
embodiments, the microwave dryer or microwave vacuum dryer is
operated at a power from about 500 W to about 3 kW, from about 5 kW
to about 15 kW, from about 6 kW to about 20 kW, from about 7 kW to
about 20 kW, from about 15 kW to about 70 kW, from about 20 kW to
about 90 kW, from about 30 kW to about 100 kW, or from about 50 kW
to about 100 kW.
[0121] In some embodiments, the drying step can be carried out for
a time period that is sufficient for drying the first suspension.
In certain embodiments, the drying time is from about 3 minutes to
about 2 hours, from about 5 minutes to about 2 hours, from about 10
minutes to about 3 hours, from about 10 minutes to about 4 hours,
from about 15 minutes to about 4 hours, or from about 20 minutes to
about 5 hours.
[0122] After formation of the pre-treated active battery electrode
material by drying the first suspension, a slurry can be formed by
dispersing the pre-treated active battery electrode material, a
conductive agent, and a binder material in a second aqueous
solution.
[0123] In certain embodiments, the amount of the pre-treated active
battery electrode material is at least 1%, at least 2%, at least
3%, at least 4%, at least 5%, at least 10%, at least 15%, at least
20%, at least 25%, at least 30%, at least 35%, at least 40%, at
least 45%, at least 50%, at least 55%, at least 60%, at least 65%,
at least 70%, at least 75%, at least 80%, at least 85%, at least
90%, or at least 95% by weight or volume, based on the total weight
or volume of the slurry. In some embodiments, the amount of the
pre-treated active battery electrode material is at most 1%, at
most 2%, at most 3%, at most 4%, at most 5%, at most 10%, at most
15%, at most 20%, at most 25%, at most 30%, at most 35%, at most
40%, at most 45%, at most 50%, at most 55%, at most 60%, at most
65%, at most 70%, at most 75%, at most 80%, at most 85%, at most
90%, or at most 95% by weight or volume, based on the total weight
or volume of the slurry.
[0124] In some embodiments, the pre-treated active battery
electrode material is the major component of the slurry. In some
embodiments, the pre-treated active battery electrode material is
present in an amount from about 50% to about 95% by weight or
volume, from about 55% to about 95% by weight or volume, from about
60% to about 95% by weight or volume, from about 65% to about 95%
by weight or volume, from about 70% to about 95% by weight or
volume, from about 75% to about 95% by weight or volume, from about
80% to about 95% by weight or volume, from about 85% to about 95%
by weight or volume, from about 55% to about 85% by weight or
volume, from about 60% to about 85% by weight or volume, from about
65% to about 85% by weight or volume, from about 70% to about 85%
by weight or volume, from about 65% to about 80% by weight or
volume, or from about 70% to about 80% by weight or volume, based
on the total weight or volume of the slurry.
[0125] The conductive agent in the slurry is for enhancing the
electrically-conducting property of an electrode. In some
embodiments, the conductive agent is selected from the group
consisting of carbon, carbon black, graphite, expanded graphite,
graphene, graphene nanoplatelets, carbon fibres, carbon
nano-fibers, graphitized carbon flake, carbon tubes, carbon
nanotubes, activated carbon, mesoporous carbon, and combinations
thereof. In certain embodiments, the conductive agent is not
carbon, carbon black, graphite, expanded graphite, graphene,
graphene nanoplatelets, carbon fibres, carbon nano-fibers,
graphitized carbon flake, carbon tubes, carbon nanotubes, activated
carbon, or mesoporous carbon.
[0126] The binder material in the slurry performs a role of binding
the active battery electrode material and conductive agent together
on the current collector. In some embodiments, the binder material
is selected from the group consisting of styrene-butadiene rubber
(SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride
(PVDF), acrylonitrile copolymer, polyacrylic acid (PAA),
polyacrylonitrile, poly(vinylidene fluoride)-hexafluoropropene
(PVDF-HFP), latex, a salt of alginic acid, and combinations
thereof. In certain embodiments, the salt of alginic acid comprises
a cation selected from Na, Li, K, Ca, NH.sub.4, Mg, Al, or a
combination thereof.
[0127] In some embodiments, the binder material is SBR, CMC, PAA, a
salt of alginic acid, or a combination thereof. In certain
embodiments, the binder material is acrylonitrile copolymer. In
some embodiments, the binder material is polyacrylonitrile. In
certain embodiments, the binder material is free of
styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC),
polyvinylidene fluoride (PVDF), acrylonitrile copolymer,
polyacrylic acid (PAA), polyacrylonitrile, poly(vinylidene
fluoride)-hexafluoropropene (PVDF-HFP), latex, or a salt of alginic
acid.
[0128] In certain embodiments, the amount of each of the conductive
agent and binder material is independently at least 1%, at least
2%, at least 3%, at least 4%, at least 5%, at least 10%, at least
15%, at least 20%, at least 25%, at least 30%, at least 35%, at
least 40%, at least 45%, or at least 50% by weight or volume, based
on based on the total weight or volume of the slurry. In some
embodiments, the amount of each of the conductive agent and binder
material is independently at most 1%, at most 2%, at most 3%, at
most 4%, at most 5%, at most 10%, at most 15%, at most 20%, at most
25%, at most 30%, at most 35%, at most 40%, at most 45%, or at most
50% by weight or volume, based on the total weight or volume of the
slurry.
[0129] In some embodiments, the conductive agent is pre-treated in
an alkaline or basic solution prior to step 3). Pre-treating the
conductive agent before the slurry preparation can enhance
wettability and dispersing capability of the conductive agent in
the slurry, thus allowing homogeneous distribution of the
conductive agent within the dried composite electrode. If
particulates of the conductive agent are dispersed heterogeneously
in the electrode, the battery performance, life, and safety will be
affected.
[0130] In certain embodiments, the conductive agent can be
pre-treated for a time period from about 30 minutes to about 2
hours, from about 30 minutes to about 1.5 hours, from about 30
minutes to about 1 hour, from about 45 minutes to about 2 hours,
from about 45 minutes to about 1.5 hours, or from about 45 minutes
to about 1 hour. In some embodiments, the alkaline or basic
solution comprises a base selected from the group consisting of
H.sub.2O.sub.2, LiOH, NaOH, KOH, NH.sub.3.H.sub.2O, Be(OH).sub.2,
Mg(OH).sub.2, Ca(OH).sub.2, Li.sub.2CO.sub.3, Na.sub.2CO.sub.3,
NaHCO.sub.3, K.sub.2CO.sub.3, KHCO.sub.3, and combinations thereof.
In certain embodiments, the basic solution comprises an organic
base. In some embodiments, the basic solution is free of organic
base. In certain embodiments, the basic solution is free of
H.sub.2O.sub.2, LiOH, NaOH, KOH, NH.sub.3.H.sub.2O, Be(OH).sub.2,
Mg(OH).sub.2, Ca(OH).sub.2, Li.sub.2CO.sub.3, Na.sub.2CO.sub.3,
NaHCO.sub.3, K.sub.2CO.sub.3 or KHCO.sub.3. It is desired to keep
the particulate dispersed uniformly within a slurry. Pretreating
the conductive agent with an alkaline solution can wash away
impurity such as oil and grease, promote more uniform distribution
of particles of the conductive agent and improve its dispensability
in the slurry without accumulating the alkaline impurity which has
negative impact on battery performance. Compared to adding
dispersing agent, the dispersing agent will stay in the slurry and
may negatively impact battery performance.
[0131] In some embodiments, the pH of the alkaline or basic
solution is greater than 7, greater than 8, greater than 9, greater
than 10, greater than 11, greater than 12, or greater than 13. In
some embodiments, the pH of the alkaline or basic solution is less
than 8, less than 9, less than 10, less than 11, less than 12, or
less than 13.
[0132] In certain embodiments, the conductive agent is dispersed in
a third aqueous solution to form a second suspension prior to step
3).
[0133] Compared to an active battery electrode material, a
conductive agent has a relatively high specific surface area.
Therefore, the conductive agent has a tendency to agglomerate due
to its relatively high specific surface area, especially when the
particulates of the conductive agent must be dispersed in a highly
dense suspension of the active battery electrode material.
Dispersing the conductive agent before the slurry preparation can
minimize the particles from agglomerating, thus allowing more
homogeneous distribution of the conductive agent within the dried
composite electrode. This could reduce internal resistance and
enhance electrochemical performance of electrode materials.
[0134] Each of the pre-treated active battery electrode material,
conductive agent, and binder material can be independently added to
the second aqueous solution in one portion, thereby greatly
simplifying the method of the present invention.
[0135] In some embodiments, the amount of the conductive agent in
the second suspension is from about 0.05 wt. % to about 0.5 wt. %,
from about 0.1 wt. % to about 1 wt. %, from about 0.25 wt. % to
about 2.5 wt. %, from about 0.5 wt. % to about 5 wt. %, from about
2 wt. % to about 5 wt. %, from about 3 wt. % to about 7 wt. %, or
from about 5 wt. % to about 10 wt. %, based on the total weight of
the mixture of the conductive agent and the third aqueous
solution.
[0136] In certain embodiments, the binder material is dissolved in
a fourth aqueous solution to form a resulting solution or a binder
solution prior to step 3).
[0137] Dispersing the solid binder material before the slurry
preparation can prevent adhesion of the solid binder material to
the surface of other materials, thus allowing the binder material
to disperse homogeneously into the slurry. If the binder material
is dispersed heterogeneously in the electrode, the performance of
the battery may deteriorate.
[0138] In some embodiments, the amount of the binder material in
the binder solution is from about 3 wt. % to about 6 wt. %, from
about 5 wt. % to about 10 wt. %, from about 7.5 wt. % to about 15
wt. %, from about 10 wt. % to about 20 wt. %, from about 15 wt. %
to about 25 wt. %, from about 20 wt. % to about 40 wt. %, or from
about 35 wt. % to about 50 wt. %, based on the total weight of the
mixture of the binder material and the fourth aqueous solution.
[0139] In certain embodiments, each of the second, third and fourth
aqueous solutions independently is a solution containing water as
the major component and a volatile solvent, such as alcohols, lower
aliphatic ketones, lower alkyl acetates or the like, as the minor
component in addition to water. In certain embodiments, the amount
of water in each solution is independently at least 55%, at least
60%, at least 65%, at least 70%, at least 75%, at least 80%, at
least 85%, at least 90%, or at least 95% to the total amount of
water and solvents other than water. In some embodiments, the
amount of water is at most 55%, at most 60%, at most 65%, at most
70%, at most 75%, at most 80%, at most 85%, at most 90%, or at most
95% to the total amount of water and solvents other than water. In
some embodiments, each of the second, third and fourth aqueous
solutions independently consists solely of water, that is, the
proportion of water in each solution is 100 vol. %.
[0140] Any water-miscible solvents can be used as the minor
component of the second, third or fourth aqueous solution. Some
non-limiting examples of the minor component include alcohols,
lower aliphatic ketones, lower alkyl acetates and combinations
thereof. Some non-limiting examples of the alcohol include
C.sub.2-C.sub.4 alcohols, such as methanol, ethanol, isopropanol,
n-propanol, butanol, and combinations thereof. Some non-limiting
examples of the lower aliphatic ketones include acetone, dimethyl
ketone, and methyl ethyl ketone. Some non-limiting examples of the
lower alkyl acetates include ethyl acetate, isopropyl acetate, and
propyl acetate.
[0141] In some embodiments, the volatile solvent or minor component
is methyl ethyl ketone, ethanol, ethyl acetate or a combination
thereof.
[0142] In some embodiments, the composition of the slurry does not
require organic solvents. In certain embodiments, each of the
second, third and fourth aqueous solutions independently is water.
Some non-limiting examples of water include tap water, bottled
water, purified water, pure water, distilled water, de-ionized
water, D.sub.2O, or a combination thereof. In some embodiments,
each of the second, third and fourth aqueous solutions
independently is purified water, pure water, de-ionized water,
distilled water, or a combination thereof. In certain embodiments,
each of the second, third and fourth aqueous solutions is free of
an organic solvent such as alcohols, lower aliphatic ketones, lower
alkyl acetates. Since the composition of the slurry does not
contain any organic solvent, expensive, restrictive and complicated
handling of organic solvents is avoided during the manufacture of
the slurry.
[0143] Any temperature that can be used in the dispersing step to
form the slurry can be used herein. In some embodiments, the
pre-treated active battery electrode material, conductive agent and
binder material are added to the stirring second aqueous solution
at about 14.degree. C., about 16.degree. C., about 18.degree. C.,
about 20.degree. C., about 22.degree. C., about 24.degree. C., or
about 26.degree. C. In certain embodiments, the dispersing process
can be performed with heating at a temperature from about
30.degree. C. to about 80.degree. C., from about 35.degree. C. to
about 80.degree. C., from about 40.degree. C. to about 80.degree.
C., from about 45.degree. C. to about 80.degree. C., from about
50.degree. C. to about 80.degree. C., from about 55.degree. C. to
about 80.degree. C., from about 55.degree. C. to about 70.degree.
C., from about 45.degree. C. to about 85.degree. C., or from about
45.degree. C. to about 90.degree. C. In some embodiments, the
dispersing process can be performed at a temperature below
30.degree. C., below 25.degree. C., below 22.degree. C., below
20.degree. C., below 15.degree. C., or below 10.degree. C.
[0144] Optional components may be used to assist in dispersing the
pre-treated active battery electrode material, conductive agent and
binder material in the slurry. In some embodiments, the optional
component is a dispersing agent. Any dispersing agent that can
enhance the dispersion may be added to the slurry disclosed herein.
In certain embodiments, the dispersing agent is selected from the
group consisting of ethanol, isopropanol, n-propanol, t-butanol,
n-butanol, lithium dodecyl sulfate, trimethylhexadecyl ammonium
chloride, polyethylene ethoxylate, sodium dodecylbenzene sulfonate,
sodium stearate, and combinations thereof.
[0145] In some embodiments, the total amount of the dispersing
agent is from about 0.1% to about 10%, from about 0.1% to about 8%,
from about 0.1% to about 6%, from about 0.1% to about 5%, from
about 0.1% to about 4%, from about 0.1% to about 3%, from about
0.1% to about 2%, or from about 0.1% to about 1% by weight, based
on the total weight of the slurry.
[0146] In some embodiments, each of the second, third and fourth
aqueous solutions independently comprises a dispersing agent for
promoting the separation of particles and/or preventing
agglomeration of the particles. Any surfactant that can lower the
surface tension between a liquid and a solid can be used as the
dispersing agent.
[0147] In certain embodiments, the dispersing agent is a nonionic
surfactant, an anionic surfactant, a cationic surfactant, an
amphoteric surfactant, or a combination thereof.
[0148] Some non-limiting examples of suitable nonionic surfactant
include an alkoxylated alcohol, a carboxylic ester, a polyethylene
glycol ester, and combinations thereof. Some non-limiting examples
of suitable alkoxylated alcohol include ethoxylated and
propoxylated alcohols. In some embodiments, the slurry disclosed
herein is free of nonionic surfactant.
[0149] Some non-limiting examples of suitable anionic surfactant
include a salt of an alkyl sulfate, an alkyl polyethoxylate ether
sulfate, an alkyl benzene sulfonate, an alkyl ether sulfate, a
sulfonate, a sulfosuccinate, a sarcosinate, and combinations
thereof. In some embodiments, the anionic surfactant comprises a
cation selected from the group consisting of sodium, potassium,
ammonium, and combinations thereof. In some embodiments, the slurry
disclosed herein is free of anionic surfactant.
[0150] Some non-limiting examples of suitable cationic surfactant
include an ammonium salt, a phosphonium salt, an imidazolium salt,
a sulfonium salt, and combinations thereof. Some non-limiting
examples of suitable ammonium salt include stearyl
trimethylammonium bromide (STAB), cetyl trimethylammonium bromide
(CTAB), and myristyl trimethylammonium bromide (MTAB), and
combinations thereof. In some embodiments, the slurry disclosed
herein is free of cationic surfactant.
[0151] Some non-limiting examples of suitable amphoteric surfactant
are surfactants that contain both cationic and anionic groups. The
cationic group is ammonium, phosphonium, imidazolium, sulfonium, or
a combination thereof. The anionic hydrophilic group is
carboxylate, sulfonate, sulfate, phosphonate, or a combination
thereof. In some embodiments, the slurry disclosed herein is free
of amphoteric surfactant.
[0152] The slurry can be homogenized by a homogenizer. Any
equipment that can homogenize the slurry can be used. In some
embodiments, the homogenizer is a stirring mixer, a blender, a
mill, an ultrasonicator, a rotor-stator homogenizer, an atomizer,
or a high pressure homogenizer.
[0153] In some embodiments, the homogenizer is an ultrasonicator.
Any ultrasonicator that can apply ultrasound energy to agitate and
disperse particles in a sample can be used herein. In some
embodiments, the ultrasonicator is a probe-type ultrasonicator or
an ultrasonic flow cell.
[0154] In certain embodiments, the slurry is homogenized by
mechanical stirring for a time period from about 2 hours to about 8
hours. In some embodiments, the stirring mixer is a planetary mixer
consisting of planetary and high speed dispersion blades. In
certain embodiments, the rotational speed of the planetary blade is
from about 20 rpm to about 200 rpm and rotational speed of the
dispersion blade is from about 1,000 rpm to about 3,500 rpm. In
further embodiments, the rotational speed of the planetary blade is
from about 20 rpm to about 150 rpm or from about 30 rpm to about
100 rpm, and rotational speed of the dispersion blade is from about
1,000 rpm to about 3,000 rpm or from about 1,500 rpm to about 2,500
rpm. When the homogenizer is a stirring mixer, the slurry is
stirred for at least two hours to ensure sufficient dispersion. If
the dispersion is not sufficient, the battery performance such as
cycle life may be seriously affected. In further embodiments, the
stirring time is from about 2 hours to about 6 hours, from about 3
hours to about 8 hours, from about 3 hours to about 6 hours, or
from about 4 hours to about 8 hours.
[0155] In certain embodiments, the ultrasonic flow cell can be
operated in a one-pass, multiple-pass or recirculating mode. In
some embodiments, the ultrasonic flow cell can include a
water-cooling jacket to help maintain the required temperature.
Alternatively, a separate heat exchanger may be used. In certain
embodiments, the flow cell can be made from stainless steel or
glass.
[0156] In some embodiments, the slurry is homogenized for a time
period from about 1 hour to about 10 hours, from about 2 hours to
about 4 hours, from about 15 minutes to about 4 hours, from about
30 minutes to about 4 hours, from about 1 hour to about 4 hours,
from about 2 hours to about 5 hours, from about 3 hours to about 5
hours, or from about 2 hours to about 6 hours.
[0157] In certain embodiments, the ultrasonicator is operated at a
power density from about 10 W/L to about 100 W/L, from about 20 W/L
to about 100 W/L, from about 30 W/L to about 100 W/L, from about 40
W/L to about 80 W/L, from about 40 W/L to about 70 W/L, from about
40 W/L to about 50 W/L, from about 40 W/L to about 60 W/L, from
about 50 W/L to about 60 W/L, from about 20 W/L to about 80 W/L,
from about 20 W/L to about 60 W/L, or from about 20 W/L to about 40
W/L.
[0158] The continuous flow through system has several advantages
over the batch-type processing. By sonication via ultrasonic flow
cell, the processing capacity becomes significantly higher. The
retention time of the material in the flow cell can be adjusted by
adjusting the flow rate.
[0159] By sonication via recirculating mode, the material is
recirculated many times through the flow cell in a recirculating
configuration. Recirculation increases the cumulative exposure time
because liquid passes through the ultrasonic flow cell only once in
a single-pass configuration.
[0160] The multiple-pass mode has a multiple flow cell
configuration. This arrangement allows for a single-pass processing
without the need for recirculation or multiple passes through the
system. This arrangement provides an additional productivity
scale-up factor equal to the number of utilized flow cells.
[0161] The homogenizing step disclosed herein reduces or eliminates
the potential aggregation of the active battery electrode material
and the conductive agent and enhances dispersion of each ingredient
in the slurry.
[0162] When the slurry is homogenized by a mill, a media such as
balls, pebbles, small rock, sand or other media is used in a
stirred mixture along with the sample material to be mixed. The
particles in the mixture are mixed and reduced in size by impact
with rapidly moving surfaces in a mill. In some embodiments, the
ball is made of hard materials such as steel, stainless steel,
ceramic or zirconium dioxide (ZrO.sub.2). However, it is observed
that the mechanical stress during the milling process causes
damages to the structure of the cathode material resulting in
distortion or major structural damage such as cracks. The cathode
material may also be abraded by the ball causing structural damage
and irregularly-shaped surface. These defects in turn cause mild to
severe degradation of electrochemical performance of an
electrochemical cell. The cathode material having a core-shell
structure is even more susceptible to mechanical damages due to
vulnerability of the shell.
[0163] The homogenized slurry can be applied on a current collector
to form a coated film on the current collector. The current
collector acts to collect electrons generated by electrochemical
reactions of the active battery electrode material or to supply
electrons required for the electrochemical reactions. In some
embodiments, each of the current collectors of the positive and
negative electrodes, which can be in the form of a foil, sheet or
film, is independently stainless steel, titanium, nickel, aluminum,
copper or electrically-conductive resin. In certain embodiments,
the current collector of the positive electrode is an aluminum thin
film. In some embodiments, the current collector of the negative
electrode is a copper thin film.
[0164] In some embodiments, the current collector has a thickness
from about 6 .mu.m to about 100 .mu.m since thickness will affect
the volume occupied by the current collector within a battery and
the amount of the active battery electrode material and hence the
capacity in the battery.
[0165] In certain embodiments, the coating process is performed
using a doctor blade coater, a slot-die coater, a transfer coater,
a spray coater, a roll coater, a gravure coater, a dip coater, or a
curtain coater. In some embodiments, the thickness of the coated
film on the current collector is from about 10 .mu.to about 300
.mu.m, or from about 20 .mu.m to about 100 .mu.m.
[0166] After applying the homogenized slurry on a current
collector, the coated film on the current collector can be dried by
a dryer to obtain the battery electrode. Any dryer that can dry the
coated film on the current collector can be used herein. Some
non-limiting examples of the dryer are a batch drying oven, a
conveyor drying oven, and a microwave drying oven. Some
non-limiting examples of the conveyor drying oven include a
conveyor hot air drying oven, a conveyor resistance drying oven, a
conveyor inductive drying oven, and a conveyor microwave drying
oven.
[0167] In some embodiments, the conveyor drying oven for drying the
coated film on the current collector includes one or more heating
sections, wherein each of the heating sections is individually
temperature controlled, and wherein each of the heating sections
may include independently controlled heating zones.
[0168] In certain embodiments, the conveyor drying oven comprises a
first heating section positioned on one side of the conveyor and a
second heating section positioned on an opposing side of the
conveyor from the first heating section, wherein each of the first
and second heating sections independently comprises one or more
heating elements and a temperature control system connected to the
heating elements of the first heating section and the second
heating section in a manner to monitor and selectively control the
temperature of each heating section.
[0169] In some embodiments, the conveyor drying oven comprises a
plurality of heating sections, wherein each heating section
includes independent heating elements that are operated to maintain
a constant temperature within the heating section.
[0170] In certain embodiments, each of the first and second heating
sections independently has an inlet heating zone and an outlet
heating zone, wherein each of the inlet and outlet heating zones
independently comprises one or more heating elements and a
temperature control system connected to the heating elements of the
inlet heating zone and the outlet heating zone in a manner to
monitor and selectively control the temperature of each heating
zone separately from the temperature control of the other heating
zones.
[0171] In some embodiments, the coated film on the current
collector can be dried at a temperature from about 50.degree. C. to
about 80.degree. C. The temperature range means a controllable
temperature gradient in which the temperature gradually rises from
the inlet temperature of 50.degree. C. to the outlet temperature of
80.degree. C. The controllable temperature gradient avoids the
coated film on the current collector from drying too rapidly.
Drying the coated film too quickly can degrade materials in the
slurry. Drying the coated film too quickly can also cause stress
defects in the electrode because the solvent can be removed from
the coated film more quickly than the film can relax or adjust to
the resulting volume changes, which can cause defects such as
cracks. It is believed that avoiding such defects can generally
enhance performance of the electrode. Furthermore, drying the
coated film too quickly can cause the binder material to migrate
and form a layer of the binder material on the surface of the
electrode.
[0172] In certain embodiments, the coated film on the current
collector is dried at a relatively slow rate. In certain
embodiments, the coated film on the current collector is dried
relatively slowly at a constant rate, followed by a relatively
quick drying rate.
[0173] In some embodiments, the coated film on the current
collector can be dried at a temperature from about 45.degree. C. to
about 100.degree. C., from about 50.degree. C. to about 100.degree.
C., from about 55.degree. C. to about 100.degree. C., from about
50.degree. C. to about 90.degree. C., from about 55.degree. C. to
about 80.degree. C., from about 55.degree. C. to about 75.degree.
C., from about 55.degree. C. to about 70.degree. C., from about
50.degree. C. to about 80.degree. C., or from about 50.degree. C.
to about 70.degree. C. In one embodiment, the coated film on the
current collector may be dried at a temperature from about
40.degree. C. to about 55.degree. C. for a time period from about 5
minutes to about 10 minutes. The lower drying temperatures may
avoid the undesirable decomposition of cathode material having high
nickel and/or manganese content.
[0174] In certain embodiments, the conveyor moves at a speed from
about 2 meter/minute to about 30 meter/minute, from about 2
meter/minute to about 25 meter/minute, from about 2 meter/minute to
about 20 meter/minute, from about 2 meter/minute to about 16
meter/minute, from about 3 meter/minute to about 30 meter/minute,
from about 3 meter/minute to about 20 meter/minute, or from about 3
meter/minute to about 16 meter/minute.
[0175] Controlling the conveyor length and speed can regulate the
drying time of the coated film. Therefore, the drying time can be
increased without increasing the length of the conveyor. In some
embodiments, the coated film on the current collector can be dried
for a time period from about 1 minute to about 30 minutes, from
about 1 minute to about 25 minutes, from about 1 minute to about 20
minutes, from about 1 minute to about 15 minutes, from about 1
minute to about 10 minutes, from about 2 minutes to about 15
minutes, or from about 2 minutes to about 10 minutes.
[0176] After the coated film on the current collector is dried, the
battery electrode is formed. In some embodiments, the battery
electrode is compressed mechanically in order to enhance the
density of the electrode.
[0177] The method disclosed herein has the advantage that an
aqueous solvent is used in the manufacturing process, which can
save process time and facilities by avoiding the need to handle or
recycle hazardous organic solvents. In addition, costs are reduced
by simplifying the total process. Therefore, this method is
especially suited for industrial processes because of its low cost
and ease of handling.
[0178] In some embodiments, batteries comprising the electrodes
prepared by the method disclosed herein show a capacity retention
of at least about 89%, about 94%, about 95%, about 97%, or about
98% after 500 cycles when discharged at a rate of 1 C. In certain
embodiments, batteries show a capacity retention of at least about
83%, about 88%, about 90%, about 92%, about 94% about 95% or about
96% after 1,000 cycles when discharged at a rate of 1 C. In some
embodiments, batteries show a capacity retention of at least about
73%, about 77%, about 80%, about 81%, about 88%, about 90%, or
about 92% after 2,000 cycles when discharged at a rate of 1 C.
[0179] The following examples are presented to exemplify
embodiments of the invention but are not intended to limit the
invention to the specific embodiments set forth. Unless indicated
to the contrary, all parts and percentages are by weight. All
numerical values are approximate. When numerical ranges are given,
it should be understood that embodiments outside the stated ranges
may still fall within the scope of the invention. Specific details
described in each example should not be construed as necessary
features of the invention.
EXAMPLES
Example 1
A) Pre-treatment of Active Battery Electrode Material
[0180] A particulate cathode material
LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2 (NMC333) (obtained from
Xiamen Tungsten CO. Ltd., China) was added to a stirring solution
containing 50% deionized water and 50% ethanol at room temperature
to form a suspension having a solid content of about 35% by weight.
The pH of the suspension was measured using a pH meter and the pH
was about 7. The suspension was further stirred at room temperature
for 5 hours. Then the suspension was separated and dried by a 2.45
GHz microwave dryer (ZY-4HO, obtained from Zhiya Industrial
Microwave Equipment Co., Ltd., Guangdong, China) at 750 W for 5
minutes to obtain a pre-treated active battery electrode
material.
B) Preparation of Positive Electrode Slurry
[0181] A positive electrode slurry was prepared by mixing 91 wt. %
pre-treated active battery electrode material, 4 wt. % carbon black
(SuperP; Timcal Ltd, Bodio, Switzerland), 4 wt. % polyacrylonitrile
(PAN) (LA 132, Chengdu Indigo Power Sources Co., Ltd., China) and
1% isopropanol (obtained from Aladdin Industries Corporation,
China) in deionized water to form a slurry having a solid content
of 70 wt. %. The slurry was homogenized by a planetary stirring
mixer (200 L mixer, Chienemei Industry Co. Ltd., China) for 6 hours
operated at a stirring speed of 20 rpm and a dispersing speed of
1500 rpm to obtain a homogenized slurry. The formulation of Example
1 is shown in Table 1 below.
C) Preparation of Positive Electrode
[0182] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 20 .mu.m using a transfer
coater (ZY-TSF6-6518, obtained from Jin Fan Zhanyu New Energy
Technology Co. Ltd., China) with an area density of about 26
mg/cm.sup.2. The coated films on the aluminum foil were dried for 3
minutes by a 24-meter-long conveyor hot air drying oven as a
sub-module of the transfer coater operated at a conveyor speed of
about 8 meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 55.degree. C. to the outlet temperature of
80.degree. C.
D) Preparation of Negative Electrode
[0183] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. %
polyacrylonitrile in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was coated onto both sides of
a copper foil having a thickness of 9 .mu.m using a transfer coater
with an area density of about 15 mg/cm.sup.2. The coated films on
the copper foil were dried at about 50.degree. C. for 2.4 minute by
a 24-meter-long conveyor hot air dryer operated at a conveyor speed
of about 10 meter/minute to obtain a negative electrode.
Morphological Measurement of Example 1
[0184] FIG. 2 shows the SEM image of the surface morphology of the
coated cathode electrode after drying. The morphology of the coated
cathode electrode was characterized by a scanning electron
microscope (JEOL-6300, obtained from JEOL, Ltd., Japan). The SEM
image clearly shows a uniform, crack-free and stable coating
throughout the electrode surface. Furthermore, the electrode shows
a homogeneous distribution of the pre-treated active battery
electrode material and conductive agent without large
agglomerates.
Example 2
Assembling of Pouch-Type Battery
[0185] After drying, the resulting cathode film and anode film of
Example 1 were used to prepare the cathode and anode respectively
by cutting into individual electrode plates. A pouch cell was
assembled by stacking the cathode and anode electrode plates
alternatively and then packaged in a case made of an
aluminum-plastic laminated film. The cathode and anode electrode
plates were kept apart by separators and the case was pre-formed.
An electrolyte was then filled into the case holding the packed
electrodes in high-purity argon atmosphere with moisture and oxygen
content<1 ppm. The electrolyte was a solution of LiPF.sub.6 (1
M) in a mixture of ethylene carbonate (EC), ethyl methyl carbonate
(EMC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1.
After electrolyte filling, the pouch cells were vacuum sealed and
then mechanically pressed using a punch tooling with standard
square shape.
Electrochemical Measurements of Example 2
I) Nominal Capacity
[0186] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester (BTS-5V20A, obtained
from Neware Electronics Co. Ltd, China) between 3.0 V and 4.3 V.
The nominal capacity was about 10 Ah.
II) Cyclability Performance
[0187] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.3 V. Test result of cyclability performance is shown in
FIG. 3. The capacity retention after 450 cycles was about 95.6% of
the initial value. The test result is shown in Table 2 below.
Example 3
A) Pre-Treatment of Active Battery Electrode Material
[0188] A particulate cathode material LiMn.sub.2O.sub.4 (LMO)
(obtained from HuaGuan HengYuan LiTech Co. Ltd., Qingdao, China)
was added to a stirring 7 wt. % solution of acetic acid in water
(obtained from Aladdin Industries Corporation, China) at room
temperature to form a suspension having a solid content of about
50% by weight. The pH of the suspension was measured using a pH
meter and the pH was about 6. The suspension was further stirred at
room temperature for 2.5 hours. Then the suspension was separated
and dried by a 2.45 GHz microwave dryer at 750 W for 5 minutes to
obtain a pre-treated active battery electrode material.
B) Preparation of Positive Electrode Slurry
[0189] Carbon nanotube (NTP2003; Shenzhen Nanotech Port Co., Ltd.,
China) (25 g) was pretreated in 2 L of an alkaline solution
containing 0.5 wt. % NaOH for about 15 minutes and then washed by
deionized water (5 L). The treated carbon nanotube was then
dispersed in deionized water to form a suspension having a solid
content of 6.25 wt. %.
[0190] A positive electrode slurry was prepared by mixing 92 wt. %
pre-treated active battery electrode material, 3 wt. % carbon
black, 1 wt. % suspension of the treated carbon nanotube and 4 wt.
% polyacrylonitrile in deionized water to form a slurry having a
solid content of 65 wt. %. The slurry was homogenized by a
circulating ultrasonic flow cell (NP8000, obtained from Guangzhou
Newpower Ultrasonic Electronic Equipment Co., Ltd., China) for 8
hours operated at 1000 W to obtain a homogenized slurry. The
formulation of Example 3 is shown in Table 1 below.
C) Preparation of Positive Electrode
[0191] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 20 .mu.m using a transfer
coater with an area density of about 40 mg/cm.sup.2. The coated
films on the aluminum foil were dried for 6 minutes by a
24-meter-long conveyor hot air drying oven as a sub-module of the
transfer coater operated at a conveyor speed of about 4
meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 65.degree. C. to the outlet temperature of
90.degree. C.
D) Preparation of Negative Electrode
[0192] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. %
polyacrylonitrile in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was coated onto both sides of
a copper foil having a thickness of 9 .mu.m using a transfer coater
with an area density of about 15 mg/cm.sup.2. The coated films on
the copper foil were dried at about 50.degree. C. for 2.4 minutes
by a 24-meter-long conveyor hot air dryer operated at a conveyor
speed of about 10 meter/minute to obtain a negative electrode.
Example 4
Assembling of Pouch-Type Battery
[0193] A pouch cell was prepared in the same manner as in Example
2.
Electrochemical Measurements of Example 4
I) Nominal Capacity
[0194] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.3
V. The nominal capacity was about 10 Ah.
II) Cyclability Performance
[0195] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.3 V. Test result of cyclability performance is shown in
FIG. 4. The capacity retention after 2000 cycles was about 77% of
the initial value. The test result is shown in Table 2 below.
Example 5
A) Pre-Treatment of Active Battery Electrode Material
[0196] A particulate cathode material
LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2 (NMC333) (obtained from
Shenzhen Tianjiao Technology Co. Ltd., China) was added to a
stirring deionized water at room temperature to form a suspension
having a solid content of about 65% by weight. The pH of the
suspension was measured using a pH meter and the pH was about 7.
The suspension was further stirred at room temperature for 10
hours. Then the suspension was separated and dried by a 2.45 GHz
microwave dryer at 750 W for 5 minutes to obtain a pre-treated
active battery electrode material.
B) Preparation of Positive Electrode Slurry
[0197] A positive electrode slurry was prepared by mixing 93 wt. %
pre-treated active battery electrode material, 3 wt. % carbon
black, 0.5 wt. % nonylphenol ethoxylate (TERGITOL.TM. NP-6, DOW
Chemical, US) and 3.5 wt. % polyacrylonitrile in deionized water to
form a slurry having a solid content of 75 wt. %. The slurry was
homogenized by a circulating ultrasonic flow cell for 8 hours
operated at 1000 W to obtain a homogenized slurry. The formulation
of Example 5 is shown in Table 1 below.
C) Preparation of Positive Electrode
[0198] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 20 .mu.m using a transfer
coater with an area density of about 32 mg/cm.sup.2. The coated
films on the aluminum foil were dried for 4 minutes by a
24-meter-long conveyor hot air drying oven as a sub-module of the
transfer coater operated at a conveyor speed of about 6
meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 50.degree. C. to the outlet temperature of
75.degree. C.
D) Preparation of Negative Electrode
[0199] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon, 5 wt. % carbon black and 5 wt. % polyacrylonitrile in
deionized water to form a slurry having a solid content of 50 wt.
%. The slurry was coated onto both sides of a copper foil having a
thickness of 9 .mu.m using a transfer coater with an area density
of about 15 mg/cm.sup.2. The coated films on the copper foil were
dried at about 50.degree. C. for 2.4 minutes by a 24-meter-long
conveyor hot air dryer operated at a conveyor speed of about 10
meter/minute to obtain a negative electrode.
Example 6
Assembling of Pouch-Type Battery
[0200] A pouch cell was prepared in the same manner as in Example
2.
Electrochemical Measurements of Example 6
I) Nominal Capacity
[0201] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.3
V. The nominal capacity was about 10 Ah.
II) Cyclability Performance
[0202] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.3 V. Test result of cyclability performance is shown in
FIG. 5. The capacity retention after 560 cycles was about 94.8% of
the initial value. The test result is shown in Table 2 below.
Example 7
A) Pre-Treatment of Active Battery Electrode Material
[0203] A particulate cathode material LiFePO.sub.4 (obtained from
Xiamen Tungsten Co. Ltd., China) was added to a stirring 3 wt. %
solution of acetic acid in water (obtained from Aladdin Industries
Corporation, China) at room temperature to form a suspension having
a solid content of about 50% by weight. The pH of the suspension
was measured using a pH meter and the pH was about 3.8. The
suspension was further stirred at room temperature for 2.5 hours.
Then the suspension was separated and dried by a 2.45 GHz microwave
dryer at 700 W for 5 minutes to obtain a pre-treated active battery
electrode material.
B) Preparation of Positive Electrode Slurry
[0204] A positive electrode slurry was prepared by mixing 88 wt. %
pre-treated active battery electrode material, 5.5 wt. % carbon
black, 0.5 wt. % nonylphenol ethoxylate (TERGITOL.TM. NP-6, DOW
Chemical, US) and 6 wt. % polyacrylonitrile in deionized water to
form a slurry having a solid content of 70 wt. %. The slurry was
homogenized by a circulating ultrasonic flow cell for 6 hours
operated at 1000 W to obtain a homogenized slurry. The formulation
of Example 7 is shown in Table 1 below.
C) Preparation of Positive Electrode
[0205] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 30 .mu.m using a transfer
coater with an area density of about 56 mg/cm.sup.2. The coated
films on the aluminum foil were then dried for 6 minutes by a
24-meter-long conveyor hot air drying oven as a sub-module of the
transfer coater operated at a conveyor speed of about 4
meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 75.degree. C. to the outlet temperature of
90.degree. C.
D) Preparation of Negative Electrode
[0206] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. %
polyacrylonitrile in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was coated onto both sides of
a copper foil having a thickness of 9 .mu.m using a transfer coater
with an area density of about 15 mg/cm.sup.2. The coated films on
the copper foil were then dried at about 50.degree. C. for 2.4
minutes by a 24-meter-long conveyor hot air dryer operated at a
conveyor speed of about 10 meter/minute to obtain a negative
electrode.
Example 8
Assembling of Pouch-Type Battery
[0207] A pouch cell was prepared in the same manner as in Example
2.
Electrochemical Measurements of Example 8
I) Nominal Capacity
[0208] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 2.5 V and 3.6
V. The nominal capacity was about 3.6 Ah.
II) Cyclability Performance
[0209] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
2.5 V and 3.6 V. Test result of cyclability performance is shown in
FIG. 6. The capacity retention after 3000 cycles was about 82.6% of
the initial value. The test result is shown in Table 2 below.
Example 9
[0210] A) Preparation of an Active Cathode Material with Core-Shell
Structure
[0211] The core of the core-shell cathode material was
Li.sub.1.03Ni.sub.0.51Mn.sub.0.32Co.sub.0.17O.sub.2 and was
prepared by a co-precipitation method. The shell of the core-shell
cathode material was
Li.sub.0.95Ni.sub.0.53Mn.sub.0.29Co.sub.0.15Al.sub.0.03O.sub.2 and
was prepared by forming a precipitate of Al(OH).sub.3 on the
surface of the core to form a precursor, mixing the precursor with
Li.sub.2CO.sub.3 (obtained from Tianqi Lithium, Shenzhen, China) to
obtain a mixture, and calcinating the mixture at 900.degree. C. The
calcinated product was crushed by a jet mill (LNJ-6A, obtained from
Mianyang Liuneng Powder Equipment Co., Ltd., Sichuan, China) for
about 1 hour, followed by passing the crushed product through a
270-mesh sieve to obtain a cathode material having a particle size
D50 of about 38 .mu.m. The content of aluminium in the core-shell
cathode material gradiently decreased from the outer surface of the
shell to the inner core. The thickness of the shell was about 3
.mu.m.
B) Pre-Treatment of the Active Battery Electrode Material
[0212] The core-shell cathode material (C-S NMC532) prepared above
was added to a stirring solution containing 50% deionized water and
50% methanol at room temperature to form a suspension having a
solid content of about 50% by weight. The pH of the suspension was
measured using a pH meter and the pH was about 7.5. The suspension
was further stirred at room temperature for 3.5 hours. Then the
suspension was separated and dried by a 2.45 GHz microwave dryer at
750 W for 5 minutes to obtain a pre-treated active battery
electrode material.
C) Preparation of Positive Electrode Slurry
[0213] A positive electrode slurry was prepared by mixing 90 wt. %
pre-treated active battery electrode material, 5 wt. % carbon black
(SuperP; obtained from Timcal Ltd, Bodio, Switzerland) as a
conductive agent, and 5 wt. % polyacrylonitrile (LA 132, Chengdu
Indigo Power Sources Co., Ltd., China) as a binder, which were
dispersed in deionized water to form a slurry with a solid content
of 50 wt. %. The slurry was homogenized by a planetary stirring
mixer for 6 hours operated at a stirring speed of 20 rpm and a
dispersing speed of 1500 rpm to obtain a homogenized slurry. The
formulation of Example 9 is shown in Table 1 below.
D) Preparation of Positive Electrode
[0214] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 30 .mu.m using a transfer
coater with an area density of about 44 mg/cm.sup.2. The coated
films on the aluminum foil were then dried for 5 minutes by a
24-meter-long conveyor hot air drying oven as a sub-module of the
transfer coater operated at a conveyor speed of about 4
meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 67.degree. C. to the outlet temperature of
78.degree. C.
E) Preparation of Negative Electrode
[0215] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. %
polyacrylonitrile in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was coated onto both sides of
a copper foil having a thickness of 9 .mu.m using a transfer coater
with an area density of about 15 mg/cm.sup.2. The coated films on
the copper foil were then dried at about 50.degree. C. for 2.4
minutes by a 24-meter-long conveyor hot air dryer operated at a
conveyor speed of about 10 meter/minute to obtain a negative
electrode.
Example 10
Assembling of Pouch-Type Battery
[0216] A pouch cell was prepared in the same manner as in Example
2.
Electrochemical Measurements of Example 10
I) Nominal Capacity
[0217] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.46 Ah.
II) Cyclability Performance
[0218] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
FIG. 7. The capacity retention after 361 cycles was about 98.6% of
the initial value. The test result is shown in Table 2 below.
Example 11
[0219] A) Preparation of an Active Cathode Material with Core-Shell
Structure
[0220] The core of the core-shell cathode material was
Li.sub.1.01Ni.sub.0.96Mg.sub.0.04O.sub.2 (C--S LNMgO) and was
prepared by solid state reaction in which MgO and NiO.sub.x (x=1 to
2) were mixed with LiOH followed by calcination at 850.degree. C.
The shell of the core-shell cathode material was
Li.sub.0.95Co.sub.1.1O.sub.2 and was prepared by forming a
precipitate of Co(OH).sub.2 on the surface of the core to form a
precursor, mixing the precursor with Li.sub.2CO.sub.3 (obtained
from Tianqi Lithium, Shenzhen, China) to obtain a mixture, and
calcinating the mixture at 800.degree. C. The calcinated product
was crushed by a jet mill (LNJ-6A, obtained from Mianyang Liuneng
Powder Equipment Co., Ltd., Sichuan, China) for about 1 hour,
followed by passing the crushed product through a 270-mesh sieve to
obtain a cathode material having a particle size D50 of about 33
.mu.m. The content of cobalt in the core-shell cathode material
gradiently decreased from the outer surface of the shell to the
inner core. The thickness of the shell was about 5 .mu.m.
B) Pre-Treatment of the Active Battery Electrode Material
[0221] The core-shell cathode material prepared above was added to
a stirring solution containing 70% deionized water and 30%
iso-propanol at room temperature to form a suspension having a
solid content of about 60% by weight. The pH of the suspension was
measured using a pH meter and the pH was about 8.0. The suspension
was further stirred at room temperature for 6.5 hours. Then the
suspension was separated and dried by a 2.45 GHz microwave dryer at
750 W for 5 minutes to obtain a pre-treated active battery
electrode material.
C) Preparation of Positive Electrode Slurry
[0222] A positive electrode slurry was prepared by mixing 89 wt. %
pre-treated active battery electrode material, 5.5 wt. % carbon
black (SuperP; obtained from Timcal Ltd, Bodio, Switzerland) as a
conductive agent, and 5.5 wt. % polyacrylonitrile (LA 132, Chengdu
Indigo Power Sources Co., Ltd., China) as a binder, which were
dispersed in deionized water to form a slurry with a solid content
of 50 wt. %. The slurry was homogenized by a planetary stirring
mixer for 6 hours operated at a stirring speed of 20 rpm and a
dispersing speed of 1500 rpm to obtain a homogenized slurry. The
formulation of Example 11 is shown in Table 1 below.
D) Preparation of Positive Electrode
[0223] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 30 .mu.m using a transfer
coater with an area density of about 42 mg/cm.sup.2. The coated
films on the aluminum foil were then dried for 5.5 minutes by a
24-meter-long conveyor hot air drying oven as a sub-module of the
transfer coater operated at a conveyor speed of about 4.2
meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 62.degree. C. to the outlet temperature of
75.degree. C.
E) Preparation of Negative Electrode
[0224] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. %
polyacrylonitrile in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was coated onto both sides of
a copper foil having a thickness of 9 .mu.m using a transfer coater
with an area density of about 15 mg/cm.sup.2. The coated films on
the copper foil were then dried at about 50.degree. C. for 2.4
minutes by a 24-meter-long conveyor hot air dryer operated at a
conveyor speed of about 10 meter/minute to obtain a negative
electrode.
Example 12
Assembling of Pouch-Type Battery
[0225] A pouch cell was prepared in the same manner as in Example
2.
Electrochemical Measurements of Example 12
I) Nominal Capacity
[0226] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.4 Ah.
II) Cyclability Performance
[0227] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
FIG. 8. The capacity retention after 385 cycles was about 98.1% of
the initial value. The test result is shown in Table 2 below.
Example 13
A) Pre-Treatment of Active Battery Electrode Material
[0228] A particulate cathode material LiCoO.sub.2 (obtained from
Xiamen Tungsten CO. Ltd., China) was added to a stirring solution
containing 50% deionized water and 50% ethanol at room temperature
to form a suspension having a solid content of about 2% by weight.
The pH of the suspension was measured using a pH meter and the pH
was about 7.0. The suspension was further stirred at room
temperature for 1 hour. Then the suspension was separated and dried
by a 2.45 GHz microwave dryer (ZY-4HO, obtained from Zhiya
Industrial Microwave Equipment Co., Ltd., Guangdong, China) at 750
W for 5 minutes to obtain a pre-treated active battery electrode
material.
B) Preparation of Positive Electrode Slurry
[0229] A positive electrode slurry was prepared by mixing 90 wt. %
pre-treated active battery electrode material, 5 wt. % carbon black
(SuperP; obtained from Timcal Ltd, Bodio, Switzerland) as a
conductive agent, and 5 wt. % polyacrylonitrile (LA 132, Chengdu
Indigo Power Sources Co., Ltd., China) as a binder, which were
dispersed in deionized water to form a slurry with a solid content
of 50 wt. %. The slurry was homogenized by a planetary stirring
mixer for 6 hours operated at a rotation speed of 30 rpm and a
dispersing speed of 1500 rpm to obtain a homogenized slurry. The
formulation of Example 13 is shown in Table 1 below.
C) Preparation of Positive Electrode
[0230] The homogenized slurry was coated onto both sides of an
aluminum foil having a thickness of 20 .mu.m using a transfer
coater (ZY-TSF6-6518, obtained from Jin Fan Zhanyu New Energy
Technology Co. Ltd., China) with an area density of about 26
mg/cm.sup.2. The coated films on the aluminum foil were dried for
3.4 minutes by a 24-meter-long conveyor hot air drying oven as a
sub-module of the transfer coater operated at a conveyor speed of
about 7 meter/minute to obtain a positive electrode. The
temperature-programmed oven allowed a controllable temperature
gradient in which the temperature gradually rose from the inlet
temperature of 70.degree. C. to the outlet temperature of
80.degree. C.
D) Preparation of Negative Electrode
[0231] A negative electrode slurry was prepared by mixing 90 wt. %
hard carbon (HC; 99.5% purity, Ruifute Technology Ltd., Shenzhen,
Guangdong, China), 5 wt. % carbon black and 5 wt. %
polyacrylonitrile in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was coated onto both sides of
a copper foil having a thickness of 9 .mu.m using a transfer coater
with an area density of about 15 mg/cm.sup.2. The coated films on
the copper foil were dried at about 50.degree. C. for 2.4 minute by
a 24-meter-long conveyor hot air dryer operated at a conveyor speed
of about 10 meter/minute to obtain a negative electrode.
Example 14
Assembling of Pouch-Type Battery
[0232] A pouch cell was prepared in the same manner as in Example
2.
Electrochemical Measurements of Example 14
[0233] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.7 Ah.
[0234] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 9.
Example 15
[0235] A pouch cell was prepared in the same manner as in Examples
1 and 2, except that cathode material
LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2 (NMC811) (obtained from
Henan Kelong NewEnergy Co., Ltd., Xinxiang, China) was used instead
of NMC333, and additive was not added. A positive electrode slurry
was prepared by mixing 91 wt. % pre-treated active battery
electrode material, 5 wt. % carbon black (SuperP; Timcal Ltd,
Bodio, Switzerland), and 4 wt. % polyacrylonitrile (PAN) (LA 132,
Chengdu Indigo Power Sources Co., Ltd., China) in deionized water
to form a slurry having a solid content of 55 wt. %. The slurry was
homogenized by a planetary stirring mixer (200 L mixer, Chienemei
Industry Co. Ltd., China) for 6 hours operated at a stirring speed
of 20 rpm and a dispersing speed of 1500 rpm to obtain a
homogenized slurry. The formulation of Example 15 is shown in Table
1 below.
[0236] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 12.7 Ah. Test result of
cyclability performance is shown in Table 2 below and FIG. 10.
Example 16
[0237] A pouch cell was prepared in the same manner as in Examples
1 and 2, except that cathode material
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2 (NMC622) (obtained from
Hunan Rui Xiang New Material Co., Ltd., Changsha, China) was used
instead of NMC333, and additive was not added. A positive electrode
slurry was prepared by mixing 90 wt. % pre-treated active battery
electrode material, 5 wt. % carbon black (SuperP; Timcal Ltd,
Bodio, Switzerland), and 5 wt. % polyacrylonitrile (PAN) (LA 132,
Chengdu Indigo Power Sources Co., Ltd., China) in deionized water
to form a slurry having a solid content of 60 wt. %. The slurry was
homogenized by a planetary stirring mixer (200 L mixer, Chienemei
Industry Co. Ltd., China) for 6 hours operated at a stirring speed
of 20 rpm and a dispersing speed of 1500 rpm to obtain a
homogenized slurry. The formulation of Example 16 is shown in Table
1 below.
[0238] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10 Ah. Test result of cyclability
performance is shown in Table 2 below and FIG. 11.
Example 17
[0239] A pouch cell was prepared in the same manner as in Examples
1 and 2, except that cathode material
Li.sub.1.0Ni.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2 (NCA) (obtained
from Hunan Rui Xiang New Material Co., Ltd., Changsha, China) was
used instead of NMC333, and additive was not added. A positive
electrode slurry was prepared by mixing 91 wt. % pre-treated active
battery electrode material, 5 wt. % carbon black (SuperP; Timcal
Ltd, Bodio, Switzerland), and 4 wt. % polyacrylonitrile (PAN) (LA
132, Chengdu Indigo Power Sources Co., Ltd., China) in deionized
water to form a slurry having a solid content of 55 wt. %. The
slurry was homogenized by a planetary stirring mixer (200 L mixer,
Chienemei Industry Co. Ltd., China) for 6 hours operated at a
stirring speed of 20 rpm and a dispersing speed of 1500 rpm to
obtain a homogenized slurry. The formulation of Example 17 is shown
in Table 1 below.
[0240] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10 Ah. Test result of cyclability
performance is shown in Table 2 below and FIG. 12.
Example 18
[0241] A pouch cell was prepared in the same manner as in Examples
13 and 14, except that cathode material
LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2 (NMC532) (obtained from
Hunan Rui Xiang New Material Co. Ltd., Changsha, China) was used
instead of LiCoO.sub.2; alginic acid sodium salt (sodium alginate,
obtained from Aladdin Industries Corporation, China) and
polyacrylonitrile were used instead of polyacrylonitrile as a
cathode binder material; and additive was not added. A positive
electrode slurry was prepared by mixing 88 wt. % pre-treated active
battery electrode material, 6 wt. % carbon black (SuperP; Timcal
Ltd, Bodio, Switzerland), 2.5 wt. % alginic acid sodium salt, and
3.5 wt. % polyacrylonitrile (LA 132, Chengdu Indigo Power Sources
Co., Ltd., China) in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was homogenized by a
planetary stirring mixer (200 L mixer, Chienemei Industry Co. Ltd.,
China) for 6 hours operated at a stirring speed of 20 rpm and a
dispersing speed of 1500 rpm to obtain a homogenized slurry. The
formulation of Example 18 is shown in Table 1 below.
[0242] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.7 Ah. Test result of
cyclability performance is shown in Table 2 below and FIG. 13.
Comparative Example 1
[0243] A pouch cell was prepared in the same manner as in Examples
13 and 14, except that 1.5 wt. % carboxymethyl cellulose (CMC,
BSH-12, DKS Co. Ltd., Japan) and 3.5 wt. % SBR (AL-2001, NIPPON
A&L INC., Japan) were used instead of 5 wt. % polyacrylonitrile
as a cathode binder material, and 0.01 wt. % solution of acetic
acid in water was used instead of a mixture of H.sub.2O and ethanol
when pre-treating the cathode material. A particulate cathode
material LiCoO.sub.2 (obtained from Xiamen Tungsten CO. Ltd.,
China) was added to a stirring 0.01 wt. % solution of acetic acid
in water (obtained from Aladdin Industries Corporation, China) at
room temperature to form a suspension having a solid content of
about 2% by weight. The pH of the suspension was measured using a
pH meter and the pH was about 3.4. The suspension was further
stirred at room temperature for 1 hour. Then the suspension was
separated and dried by a 2.45 GHz microwave dryer (ZY-4HO, obtained
from Zhiya Industrial Microwave Equipment Co., Ltd., Guangdong,
China) at 750 W for 5 minutes to obtain a pre-treated active
battery electrode material. A positive electrode slurry was
prepared by mixing 90 wt. % pre-treated active battery electrode
material, 5 wt. % carbon black, 1.5 wt. % carboxymethyl cellulose
and 3.5 wt. % SBR in deionized water to form a slurry having a
solid content of 50 wt. %. The slurry was homogenized by a
planetary stirring mixer (200 L mixer, Chienemei Industry Co. Ltd.,
China) for 6 hours operated at a stirring speed of 30 rpm and a
dispersing speed of 1500 rpm to obtain a homogenized slurry. The
formulation of Comparative Example 1 is shown in Table 1 below.
[0244] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 9.1 Ah.
[0245] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 14.
Comparative Example 2
[0246] A pouch cell was prepared in the same manner as in
Comparative Example 1, except that 2 wt. % carboxymethyl cellulose
(CMC, BSH-12, DKS Co. Ltd., Japan) and 3 wt. % polyvinyl alcohol
(PVA) (obtained from The Nippon Synthetic Chemical Industry Co.,
Ltd., Japan) were used instead of 1.5 wt. % carboxymethyl cellulose
and 3.5 wt. % SBR as a cathode binder material. A positive
electrode slurry was prepared by mixing 90 wt. % pre-treated active
battery electrode material, 5 wt. % carbon black, 2 wt. %
carboxymethyl cellulose and 3 wt. % PVA in deionized water to form
a slurry having a solid content of 50 wt. %. The slurry was
homogenized by a planetary stirring mixer (200 L mixer, Chienemei
Industry Co. Ltd., China) for 6 hours operated at a stirring speed
of 30 rpm and a dispersing speed of 1500 rpm to obtain a
homogenized slurry. The formulation of Comparative Example 2 is
shown in Table 1 below.
[0247] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 8.2 Ah.
[0248] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 15.
Comparative Example 3
[0249] A pouch cell was prepared in the same manner as in Examples
13 and 14, except that ball mill was used instead of planetary
mixer as a homogenizer when preparing the positive electrode
slurry, and 0.01 wt. % solution of acetic acid in water was used
instead of a mixture of H.sub.2O and ethanol when pre-treating the
cathode material. A particulate cathode material LiCoO.sub.2
(obtained from Xiamen Tungsten CO. Ltd., China) was added to a
stirring 0.01 wt. % solution of acetic acid in water (obtained from
Aladdin Industries Corporation, China) at room temperature to form
a suspension having a solid content of about 2% by weight. The pH
of the suspension was measured using a pH meter and the pH was
about 3.4. The suspension was further stirred at room temperature
for 1 hour. Then the suspension was separated and dried by a 2.45
GHz microwave dryer (ZY-4HO, obtained from Zhiya Industrial
Microwave Equipment Co., Ltd., Guangdong, China) at 750 W for 5
minutes to obtain a pre-treated active battery electrode material.
A positive electrode slurry was prepared by mixing 90 wt. %
pre-treated active battery electrode material, 5 wt. % carbon black
(SuperP; Timcal Ltd, Bodio, Switzerland), and 5 wt. %
polyacrylonitrile (PAN) (LA 132, Chengdu Indigo Power Sources Co.,
Ltd., China) in deionized water to form a slurry having a solid
content of 50 wt. %. The slurry was homogenized in a 500 mL
container in a planetary-type ball mill (Changsha MITR Instrument
& Equipment Co. Ltd., China) with thirty (too many?) zirconium
oxide (ZrO.sub.2) balls (fifteen 5 mm and fifteen 15 mm) for 3
hours operated at a rotation speed of 150 rpm and spinning speed of
250 rpm to obtain a homogenized slurry. The formulation of
Comparative Example 3 is shown in Table 1 below.
[0250] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 9.9 Ah.
[0251] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 16.
Comparative Example 4
[0252] A pouch cell was prepared in the same manner as in
Comparative Example 1, except that 5 wt. % polyacrylonitrile were
used instead of 1.5 wt. % carboxymethyl cellulose and 3.5 wt. % SBR
as a cathode binder material. The formulation of Comparative
Example 4 is shown in Table 1 below.
[0253] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.1 Ah.
[0254] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 17.
Comparative Example 5
[0255] A pouch cell was prepared in the same manner as in Example
15, except that 0.01 wt. % solution of citric acid in water was
used instead of a mixture of H.sub.2O and ethanol when pre-treating
the cathode material. A particulate cathode material NMC811 was
added to a stirring 0.01 wt. % solution of citric acid in water
(obtained from Aladdin Industries Corporation, China) at room
temperature to form a suspension having a solid content of about 2%
by weight. The pH of the suspension was measured using a pH meter
and the pH was about 3.4. The suspension was further stirred at
room temperature for 1 hour. Then the suspension was separated and
dried by a 2.45 GHz microwave dryer (ZY-4HO, obtained from Zhiya
Industrial Microwave Equipment Co., Ltd., Guangdong, China) at 750
W for 5 minutes to obtain a pre-treated active battery electrode
material. The formulation of Comparative Example 5 is shown in
Table 1 below.
[0256] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 11.4 Ah.
[0257] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 18.
Comparative Example 6
[0258] A pouch cell was prepared in the same manner as in Example
15, except that the cathode material was not pre-treated. The
formulation of Comparative Example 6 is shown in Table 1 below.
[0259] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 12.5 Ah.
[0260] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 19.
Comparative Example 7
[0261] A pouch cell was prepared in the same manner as in Example
11, except that 0.01 wt. % solution of citric acid in water was
used instead of a mixture of H.sub.2O and iso-propanol when
pre-treating the cathode material. A particulate cathode material
C-S LNMgO was added to a stirring 0.01 wt. % solution of citric
acid in water (obtained from Aladdin Industries Corporation, China)
at room temperature to form a suspension having a solid content of
about 2% by weight. The pH of the suspension was measured using a
pH meter and the pH was about 3.6. The suspension was further
stirred at room temperature for 1 hour. Then the suspension was
separated and dried by a 2.45 GHz microwave dryer (ZY-4HO, obtained
from Zhiya Industrial Microwave Equipment Co., Ltd., Guangdong,
China) at 750 W for 5 minutes to obtain a pre-treated active
battery electrode material. The formulation of Comparative Example
7 is shown in Table 1 below.
[0262] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10 Ah.
[0263] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 20.
Comparative Example 8
[0264] A pouch cell was prepared in the same manner as in Example
13, except that 1.5 wt. % carboxymethyl cellulose (CMC, BSH-12, DKS
Co. Ltd., Japan) and 3.5 wt. % SBR (AL-2001, NIPPON A&L INC.,
Japan) were used instead of 5 wt. % polyacrylonitrile as an anode
binder material. The formulation of Comparative Example 8 is shown
in Table 1 below.
[0265] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 11.2 Ah.
[0266] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 21.
Comparative Example 9
[0267] A pouch cell was prepared in the same manner as in Example
13, except that 5 wt. % polyvinylidene fluoride (PVDF; Solef.RTM.
5130, obtained from Solvay S.A., Belgium) was used instead of 5 wt.
% polyacrylonitrile as an anode binder material; and
N-methyl-2-pyrrolidone (NMP; purity of .gtoreq.99%, Sigma-Aldrich,
USA) was used instead of deionized water as a solvent. A negative
electrode slurry was prepared by mixing 90 wt. % hard carbon (HC;
99.5% purity, Ruifute Technology Ltd., Shenzhen, Guangdong, China),
5 wt. % carbon black and 5 wt. % PVDF in NMP to form a slurry
having a solid content of 50 wt. %. The slurry was coated onto both
sides of a copper foil having a thickness of 9 .mu.m using a
transfer coater with an area density of about 15 mg/cm.sup.2. The
coated films on the copper foil were dried at about 87.degree. C.
for 8 minute by a 24-meter-long conveyor hot air dryer operated at
a conveyor speed of about 3 meter/minute to obtain a negative
electrode. The formulation of Comparative Example 9 is shown in
Table 1 below.
[0268] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.4 Ah.
[0269] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 22.
Comparative Example 10
[0270] A pouch cell was prepared in the same manner as in Example
13, except that a vacuum oven (HSZK-6050, Shanghai Hasuc Instrument
Manufacture Co., Ltd., China) was used instead of a microwave dryer
for drying the pre-treated cathode material. The pre-treated
cathode material was dried in a vacuum oven at 88.degree. C. for 8
hours. The formulation of Comparative Example 10 is shown in Table
1 below.
[0271] The cell was tested galvanostatically at a current density
of C/2 at 25.degree. C. on a battery tester between 3.0 V and 4.2
V. The nominal capacity was about 10.3 Ah.
[0272] The cyclability performance of the pouch cell was tested by
charging and discharging at a constant current rate of 1 C between
3.0 V and 4.2 V. Test result of cyclability performance is shown in
Table 2 below and FIG. 23.
TABLE-US-00001 TABLE 1 Cathode Pre- Cathode slurry Anode slurry
Example material treatment Binder Solvent Homogenizer Binder
Solvent Example 1 NMC333 H.sub.2O/ PAN H.sub.2O Planetary PAN
H.sub.2O ethanol mixer Example 3 LMO Acetic PAN H.sub.2O Ultrasonic
PAN H.sub.2O acid flow cell Example 5 NMC333 H.sub.2O PAN H.sub.2O
Ultrasonic PAN H.sub.2O flow cell Example 7 LiFePO.sub.4 Acetic PAN
H.sub.2O Ultrasonic PAN H.sub.2O acid flow cell Example 9 C--S
NMC532 H.sub.2O/ PAN H.sub.2O Planetary PAN H.sub.2O methanol mixer
Example 11 C--S LNMgO H.sub.2O/iso- PAN H.sub.2O Planetary PAN
H.sub.2O propanol mixer Example 13 LiCoO.sub.2 H.sub.2O/ PAN
H.sub.2O Planetary PAN H.sub.2O ethanol mixer Example 15 NMC811
H.sub.2O/ PAN H.sub.2O Planetary PAN H.sub.2O ethanol mixer Example
16 NMC622 H.sub.2O/ PAN H.sub.2O Planetary PAN H.sub.2O ethanol
mixer Example 17 NCA H.sub.2O/ PAN H.sub.2O Planetary PAN H.sub.2O
ethanol mixer Example 18 NMC532 H.sub.2O/ Alginic H.sub.2O
Planetary PAN H.sub.2O ethanol acid + mixer PAN Comparative
LiCoO.sub.2 Acetic CMC + H.sub.2O Planetary PAN H.sub.2O Example 1
acid SBR mixer Comparative LiCoO.sub.2 Acetic CMC + H.sub.2O
Planetary PAN H.sub.2O Example 2 acid PVA mixer Comparative
LiCoO.sub.2 Acetic PAN H.sub.2O Ball mill PAN H.sub.2O Example 3
acid Comparative LiCoO.sub.2 Acetic PAN H.sub.2O Planetary PAN
H.sub.2O Example 4 acid mixer Comparative NMC811 Citric PAN
H.sub.2O Planetary PAN H.sub.2O Example 5 acid mixer Comparative
NMC811 / PAN H.sub.2O Planetary PAN H.sub.2O Example 6 mixer
Comparative C--S LNMgO Citric PAN H.sub.2O Planetary PAN H.sub.2O
Example 7 acid mixer Comparative LiCoO.sub.2 H.sub.2O/ PAN H.sub.2O
Planetary CMC + H.sub.2O Example 8 ethanol mixer SBR Comparative
LiCoO.sub.2 H.sub.2O/ PAN H.sub.2O Planetary PVDF NMP Example 9
ethanol mixer .sup.1Comparative LiCoO.sub.2 H.sub.2O/ PAN H.sub.2O
Planetary PAN H.sub.2O Example 10 ethanol mixer Note: .sup.1The
pre-treated cathode material was dried in a vacuum oven.
[0273] The cyclability performance of the pouch cells of Examples
1-18 and Comparative Examples 1-10 was tested by charging and
discharging at a constant current rate of 1 C. The capacity
retentions of the cells were measured during cycling and estimated
by extrapolation based on the plotted results. The measured and
estimated values are shown in Table 2 below.
TABLE-US-00002 TABLE 2 Estimated values Measured values by
extrapolation Capacity Capacity Example No. of Cycle retention (%)
No. of Cycle retention (%) Example 2 450 95.6 2,000 80.4 Example 4
2,000 77 / / Example 6 560 94.8 2,000 81.4 Example 8 3,000 82.6 / /
Example 10 361 98.6 2,000 92.2 Example 12 385 98.1 2,000 90.1
Example 14 576 94.4 2,000 80.6 Example 15 476 95.7 2,000 81.9
Example 16 497 94.4 2,000 77.5 Example 17 553 93.9 2,000 77.9
Example 18 522 93.1 2,000 73.6 Comparative 85 78.7 / / Example 1
Comparative 113 70.4 / / Example 2 Comparative 506 92.1 2000 70.0
Example 3 Comparative 514 93.4 2,000 74.3 Example 4 Comparative 466
90.1 2,000 57.5 Example 5 Comparative 485 93.8 2,000 74.4 Example 6
Comparative 413 92.6 2,000 64.2 Example 7 Comparative 508 95.1
2,000 80.7 Example 8 Comparative 606 94.3 2,000 81.2 Example 9
Comparative 472 94.8 2,000 78.0 Example 10
[0274] The comparison battery cells had a discharge capacity
retention less than 80% after only less than 100 cycles when
water-soluble binders such as CMC, SBR and PVA were used for
preparing the aqueous slurry. In contrast, the batteries of
Examples 1-18 had a discharge capacity retention of at least 86%
after 1000 cycles.
[0275] This excellent cyclability indicates that battery cell made
of cathode and anode electrodes prepared by the method disclosed
herein can achieve comparable or even better stability compared to
battery cell made of cathode and anode electrodes prepared by
conventional method involving the use of organic solvents.
[0276] While the invention has been described with respect to a
limited number of embodiments, the specific features of one
embodiment should not be attributed to other embodiments of the
invention. In some embodiments, the methods may include numerous
steps not mentioned herein. In other embodiments, the methods do
not include, or are substantially free of, any steps not enumerated
herein. Variations and modifications from the described embodiments
exist. The appended claims intend to cover all those modifications
and variations as falling within the scope of the invention.
* * * * *