U.S. patent application number 14/798004 was filed with the patent office on 2016-05-05 for lithium ionic energy storage element and method for making the same.
The applicant listed for this patent is AMITA TECHNOLOGIES INC LTD.. Invention is credited to Jing-Yih CHERNG, Bing-Joe HWANG, Chao-Yen KUO, Wei-Nien SU, Hsuan-Fu WANG.
Application Number | 20160126540 14/798004 |
Document ID | / |
Family ID | 55853648 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160126540 |
Kind Code |
A1 |
CHERNG; Jing-Yih ; et
al. |
May 5, 2016 |
LITHIUM IONIC ENERGY STORAGE ELEMENT AND METHOD FOR MAKING THE
SAME
Abstract
A lithium ionic energy storage element comprises a positive
electrode having a first current collector and a positive electrode
active substance provided on the first current collector; a
negative electrode having a second current collector and a negative
electrode active substance provided on the second current
collector, wherein the negative electrode active substance is a
material selected from the group consisting of carbon-containing
materials, Si alloy and Sn alloy; and an electrolyte, wherein the
positive electrode active substance comprises a lithium ion donor
including lithium peroxide, lithium oxide or the mixture thereof
and a positive electrode frame active substance. The invention also
relates to a method for making a lithium ionic energy storage
element.
Inventors: |
CHERNG; Jing-Yih; (Taoyuan
County, TW) ; HWANG; Bing-Joe; (Taoyuan County,
TW) ; WANG; Hsuan-Fu; (Taoyuan County, TW) ;
SU; Wei-Nien; (Taoyuan County, TW) ; KUO;
Chao-Yen; (Taoyuan County, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AMITA TECHNOLOGIES INC LTD. |
Taoyuan County |
|
TW |
|
|
Family ID: |
55853648 |
Appl. No.: |
14/798004 |
Filed: |
July 13, 2015 |
Current U.S.
Class: |
429/231.4 ;
252/182.1; 427/58; 429/231.95 |
Current CPC
Class: |
H01M 4/386 20130101;
H01M 4/1391 20130101; H01M 4/5815 20130101; H01M 4/134 20130101;
H01M 10/0525 20130101; H01M 4/505 20130101; H01M 4/5835 20130101;
H01M 4/0471 20130101; H01M 4/131 20130101; H01M 4/133 20130101;
Y02E 60/10 20130101; H01M 4/525 20130101; H01M 4/1393 20130101;
H01M 4/485 20130101; H01M 4/587 20130101; H01M 4/1395 20130101 |
International
Class: |
H01M 4/36 20060101
H01M004/36; H01M 4/134 20060101 H01M004/134; H01M 10/0525 20060101
H01M010/0525; H01M 4/131 20060101 H01M004/131; H01M 4/04 20060101
H01M004/04; H01M 4/587 20060101 H01M004/587; H01M 4/38 20060101
H01M004/38; H01M 4/1391 20060101 H01M004/1391; H01M 4/1393 20060101
H01M004/1393; H01M 4/1395 20060101 H01M004/1395; H01M 4/133
20060101 H01M004/133; H01M 4/485 20060101 H01M004/485 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2014 |
TW |
103138190 |
Claims
1. A positive electrode active substance used in a lithium ionic
energy storage element, the positive electrode active substance
comprising a lithium ion donor and a positive electrode frame
active substance, wherein the lithium ion donor includes lithium
peroxide, lithium oxide or a combination of lithium peroxide and
lithium oxide; and the positive electrode frame active substance is
a material selected from the group consisting of anatase titanium
dioxide, carbon-sulfur composite, carbon-containing materials,
carbon fluoride and--is lithium metallic oxides.
2. A lithium ionic energy storage element comprising: a positive
electrode having a first current collector and a positive electrode
active substance provided on the first current collector; a
negative electrode having a second current collector and a negative
electrode active substance provided on the second current
collector, wherein the negative electrode active substance is a
material selected from the group consisting of carbon-containing
materials, Si alloy and Sn alloy; and an electrolyte interposed
between the positive electrode and the negative electrode, wherein
the positive electrode active substance comprises a lithium ion
donor including lithium peroxide, lithium oxide or a combination of
lithium peroxide and lithium oxide and a positive electrode frame
active substance.
3. The lithium ionic energy storage element as claimed in claim 2,
wherein the positive electrode frame active substance of the
positive electrode active substance is a material selected from the
group consisting of anatase titanium dioxide, carbon-sulfur
composite, carbon-containing materials, carbon fluoride and lithium
metallic oxides.
4. The lithium ionic energy storage element as claimed in claim 3,
wherein the carbon-sulfur composite of the positive electrode frame
active substance has a weight ratio of carbon with sulfur is
0.4-1.
5. The lithium ionic energy storage element as claimed in claim 2,
wherein the positive electrode frame active substance is lithium
metallic oxides.
6. The lithium ionic energy storage element as claimed in claim 2,
wherein the positive electrode active substance contains conductive
carbon comprising super P carbon black, KS6 graphite or a
combination thereof.
7. A method for making a lithium ionic energy storage element
comprising steps: (a) mixing a lithium ion donor, a positive
electrode frame active substance and a binder with a predetermined
weight ratio to form a mixture, and adding the mixture into a
dispersant to form a positive electrode active substance, wherein
the lithium ion donor includes lithium peroxide, lithium oxide or a
combination thereof; (b) coating the positive electrode active
substance on an aluminum foil to form a film, and baking the film
to form a positive electrode; and (c) forming a lithium ionic
energy storage element by assembling the positive electrode, a
negative electrode having a negative electrode active substance and
a porous separate strip interposed between the positive electrode
and the negative electrode, and filling an electrolyte into the
porous separate strip.
8. The method as claimed in claim 7, further comprising an oxygen
removal step for removing oxygen produced in a first cycle of
charge and discharge the lithium ionic energy storage element after
filling the electrolyte into the porous separate strip.
9. The method as claimed in claim 7, wherein the positive electrode
frame active substance of the step (a) is a material selected from
the group consisting of anatase titanium dioxide, carbon-sulfur
composite, carbon-containing materials and carbon fluoride.
10. The method as claimed in claim 7, wherein the positive
electrode frame active substance of the step (a) is lithium
metallic oxides.
11. The method as claimed in claim 7, further comprising adding a
conductive carbon into the mixture of the step (a), wherein the
conductive carbon is super P carbon black, KS6 graphite or a
combination thereof.
12. The method as claimed in claim 7, wherein the binder in the
step (a) is polyvinylidene fluoride or carboxymethyl cellulose.
13. The method as claimed in claim 7, wherein the negative
electrode active substance of the step (c) is a material selected
from the group consisting of graphitized mesocarbon microbeads,
hard carbon, Si alloy and Sn alloy.
14. The method as claimed in claim 7, wherein the electrolyte of
the step (c) is a concentration of 1M LiPF.sub.6dissolving in a
mixing solution of ethylene carbonate and diethyl carbonate; or a
concentration of 1M lithium bis(trifluoromethanesulfonly)imide
dissolving in a mixing solution of tetraethylene glycol dimethyl
ether and 1,3-dioxolane.
15. The method as claimed in claim 7, wherein the dispersant of the
step (a) is N-methyl-2-pyrrolidone.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a lithium ionic energy storage
element, in particular to a lithium ionic energy storage element
comprising a positive electrode active substance including a
lithium ion donor and a positive electrode frame active
substance.
[0003] 2. Description of the Related Art
[0004] In various energy storage technologies, lithium ionic
batteries are regarded as a portable chemical power source with a
high efficiency in next generation because they have advantages of
high energy density, light weight and less pollution. Nowadays, the
lithium ionic batteries are widely used in the fields of digital
cameras, smart phones and notebooks. As the energy density of the
lithium ionic battery is enhanced, the fields of use are extended.
There is a higher need for the performance of the lithium ionic
battery as the requirement of high capacity and long life of the
lithium ionic battery for the mobile electric equipment is
increased
[0005] Typically, a lithium ionic battery comprises a negative
electrode, a positive electrode and an electrolyte. The positive
electrode active substance is not only used as an electrode
material to take part in the chemical reaction, but also used as a
lithium source. The positive electrode active substance is
generally lithium metallic oxides which contain lithium atoms
intercalated therein. Currently, lithium metallic oxides such as
lithium cobalt oxide, lithium nickel oxide and lithium manganese
oxide are available commercially. However, the above lithium
metallic oxides cannot exhibit a proper combinative property of
high initial electrical capacity, high thermal stability and
excellent electrical capacity sustainability after a lithium ionic
battery is charged and discharged repeatedly.
[0006] The lithium ionic battery is limited by the capacity
capacity (mA/g) of the positive electrode of the lithium metallic
oxides, so that it cannot exhibit a higher capacitycapacity.
Therefore, the lithium sources have to be increased if it is
desired to increase the capacity of the lithium ionic battery.
Several methods were proposed, wherein one of the methods is
coating lithium metal used as lithium source on the negative
electrode, and another method is forming lithium metal as a third
electrode on the negative electrode by electroplating. However, the
above two methods are difficult to perform and the coating and
electroplating film are not uniform because the lithium metal is
very active.
[0007] Because lithium metal has disadvantages of safety and
stability, the current commercial lithium ion secondary battery is
used a working system having a positive electrode material
containing lithium ions and a negative electrode material for
intercalating lithium ions. In recent years, the energy density of
the lithium ion secondary battery has to be enhanced, because the
electric devices have a large energy demand. However, the stability
of the positive electrode material structure is not high and the
amount of lithium ions intercalation is not large, so that the
capacity per gram cannot be further enhanced.
[0008] Several materials, for example FeF.sub.3, FePO.sub.4 and
V.sub.2O.sub.5 were proposed. The above materials are preferable to
be the positive electrode material for a high energy density,
because they have good electrical capacity and a higher platform
voltage. However, the above materials do not contain lithium ions,
so they have to combine with lithium metal. As a result, they would
be only used in half cell tests but fail to be used in a full
cell.
[0009] Therefore, the inventor conducted researches according to
the scientific approach in order to improve and resolve the above
drawback, and finally proposed the present invention, which is
reasonable and effective.
SUMMARY OF THE INVENTION
[0010] It is an object of present invention to provide a lithium
ionic energy storage element. It can exhibit a high capacity by
using a positive electrode active substance which comprises a
lithium ion donor and a positive electrode frame active
substance.
[0011] In order to achieve the above object, the present invention
provides a lithium ionic energy storage element comprising a
positive electrode having a first current collector and a positive
electrode active substance provided on the first current collector;
a negative electrode having a second current collector and a
negative electrode active substance provided on the second current
collector, wherein the negative electrode active substance is a
material selected from the group consisting of carbon-containing
materials, Si alloy and Sn alloy; and an electrolyte, wherein the
positive electrode active substance comprises a lithium ion donor
including lithium peroxide, lithium oxide or the mixture thereof
and a positive electrode frame active substance.
[0012] The present invention also relates to a positive electrode
active substance used in a lithium ionic energy storage element,
the positive electrode active substance comprising a lithium ion
donor and a positive electrode frame active substance, wherein the
lithium ion donor includes lithium peroxide, lithium oxide or a
combination of lithium peroxide and lithium oxide; and the positive
electrode frame active substance is a material selected from the
group consisting of anatase titanium dioxide, carbon-sulfur
composite, carbon-containing materials and carbon fluoride or is
lithium metallic oxides.
[0013] The present invention also relates to a method for making a
lithium ionic energy storage element. At first, lithium peroxide, a
positive electrode frame active substance, e.g. anatase titanium
dioxide and a binder, e.g. PVDF are mixed with a predetermined
weight ratio to form a mixture, and the mixture is added into a
dispersant, e.g. N-methyl-2-pyrrolidone to form a slurry. Next, the
slurry is coating on an aluminum foil to form a film by a blade
coater. The film is baked in an oven at a temperature of
80-90.degree. C. to remove a solvent, and raise the temperature to
120-130.degree. C. for a period of time to form a positive
electrode with lithium peroxide/anatase titanium dioxide. In order
to increase conductivity of lithium peroxide, conductive carbon,
for example super P carbon black, KS6 graphite or a combination
thereof may be added.
[0014] A lithium ionic energy storage element is formed by
assembling the positive electrode with lithium peroxide/anatase
titanium dioxide, a negative electrode having a negative electrode
active substance, e.g. graphitized mesocarbon microbeads (MCMB) and
a porous separate strip interposed between the positive electrode
and the negative electrode, and an electrolyte, e.g. a
concentration of 1M LiPF.sub.6 dissolving in a mixing solution of
ethylene carbonate (EC) and diethyl carbonate (DEC) with mixing
ratio 1:1 by volume is filled into the porous separate strip.
[0015] Further, the present invention relates to a method for
making a lithium ionic energy storage element. At first, lithium
peroxide, a positive electrode frame active substance, e.g.
carbon-sulfur composite and a binder, e.g. carboxymethyl cellulose
(CMC) are mixed with a predetermined weight ratio to form a
mixture, and the mixture is added into a dispersant, e.g.
N-methyl-2-pyrrolidone to form a slurry. Next, the slurry is
coating on an aluminum foil to form a film by a blade coater. The
film is baked in an oven at a temperature of 80-90.degree. C. to
remove a solvent, and raise the temperature to 120-130.degree. C.
for a period of time to form a positive electrode with lithium
peroxide/carbon-sulfur composite. In order to increase conductivity
of lithium peroxide, conductive carbon, for example super P carbon
black, KS6 graphite or a combination thereof may be added.
[0016] A lithium ionic energy storage element is formed by
assembling the positive electrode with lithium
peroxide/carbon-sulfur composite, a negative electrode having a
negative electrode active substance, e.g. hard carbon and a porous
separate strip interposed between the positive electrode and the
negative electrode, and an electrolyte, e.g. a concentration of 1M
lithium bis(trifluoromethanesulfonly)imide dissolving in a mixing
solution of tetraethylene glycol dimethyl ether (TEGDME) and
1,3-dioxolane (DOL) with mixing ratio 1:1 by volume is filled into
the porous separate strip.
[0017] Compared to the conventional lithium ionic battery
comprising lithium metallic oxides, the lithium ionic energy
storage element of the present invention comprises a lithium ion
donor having lithium peroxide and/or lithium oxide and a positive
electrode frame active substance, wherein lithium peroxide and/or
lithium oxide can be decomposed to produce lithium ions by
electrochemical charging, and lithium ions intercalate repeatedly
in and out of the positive electrode frame active substance and the
negative electrode active substance in a full cell. The full cell
can exhibit a high capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a schematic view of a unit cell structure of a
lithium ionic energy storage element an embodiment according to the
invention.
[0019] FIG. 2 shows a first cycle curve of voltage against electric
capacity of a half cell of lithium peroxide charging/discharging of
the invention.
[0020] FIG. 3 shows a second cycle and a third cycle curves of
voltage against electric capacity of a half cell of lithium
peroxide charging/discharging of the invention.
[0021] FIG. 4 shows a first cycle curve of voltage against electric
capacity of a half cell of lithium peroxide charging/discharging
under various ratio of a conductive carbon of the invention.
[0022] FIG. 5 shows cyclic voltammetry response of lithium peroxide
charging/discharging under various ratio of a conductive carbon of
the invention.
[0023] FIG. 6 shows the influent of voltage against electric
capacity of lithium peroxide in the different current density.
[0024] FIG. 7(a) shows XRD pattern of TiO.sub.2 synthetized from
tetrabutyl titanate of the invention.
[0025] FIG. 7(b) shows XRD pattern of TiO.sub.2 by simulation.
[0026] FIG. 8 shows a charging/discharging curve of prelithiation
period of Li.sub.2O.sub.2/TiO.sub.2 half cell.
[0027] FIG. 9 shows a charging/discharging curve of subsequent
cycles of Li.sub.2O.sub.2/TiO.sub.2 half cell.
[0028] FIG. 10 shows a charging/discharging curve of prelithiation
period of Li.sub.2O.sub.2/TiO.sub.2 versus MCMB full cell.
[0029] FIG. 11 shows a charging/discharging curve of subsequent
cycles of Li.sub.2O.sub.2/TiO.sub.2 versus MCMB full cell.
[0030] FIG. 12 shows a charge/discharge curve of prelithiation
period of Li.sub.2O.sub.2/TiO.sub.2 versus MCMB with disassembling
process of coin cell.
[0031] FIG. 13 shows a charge/discharge curve of subsequent cycles
of Li.sub.2O.sub.2/TiO.sub.2 versus MCMB with disassembling process
of coin cell.
[0032] FIG. 14 shows a charging/discharging curve of
Li.sub.2O.sub.2 (30 wt. %) with current density of 100 mA/g
Li.sub.2O.sub.2 vs. Li metal of half cell.
[0033] FIG. 15 shows a charge/discharge curve of carbon-sulfur
composite of half cell.
[0034] FIG. 16 shows a charge/discharge curve of prelithiation
period of lithium peroxide/carbon-sulfur composite vs. Li/Li.sup.+
of half cell.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The technical content of invention will be explained in more
detail below with reference to a few figures. However, the figures
are intended solely for illustration and not to limit the inventive
concept.
[0036] FIG. 1 shows a schematic view of a unit cell structure of a
lithium ionic energy storage element an embodiment according to the
invention. In the embodiment, the lithium ionic energy storage
element comprises a plurality of unit cell structures 100, each
unit cell structure 100 comprises a porous separate strip 104
interposed between the positive electrode 106 and the negative
electrode 108. The porous separate strip 104 is coated with a
binder 105 to enhance the binding of the cell structure's 100
components to each other. The positive electrode 106 has a first
current collector 110 and a positive electrode active substance 114
provided on the first current collector 110 and the negative
electrode 108 has a second current collector 112 and a negative
electrode active substance 116 provided on the second current
collector 112. The positive electrode active substance 114
comprises a lithium ion donor including lithium peroxide, lithium
oxide or a combination thereof and a positive electrode frame
active substance, e.g. anatase titanium dioxide or carbon-sulfur
composite. The carbon-sulfur composite has a weight ratio of carbon
with sulfur is 0.4-1. In lithium peroxide/anatase titanium dioxide
system, the negative electrode active substance 116 may be
carbon-containing materials, e.g. graphitized mesocarbon microbeads
(MCMB). In lithium peroxide/carbon-sulfur composite system, the
negative electrode active substance 116 may be carbon-containing
materials, e.g. hard carbon.
[0037] In the embodiment, the positive electrode active substance
114 used in a lithium ionic energy storage element, the positive
electrode active substance 114 comprising a lithium ion donor and a
positive electrode frame active substance, wherein the lithium ion
donor includes lithium peroxide, lithium oxide or a combination of
lithium peroxide and lithium oxide; and the positive electrode
frame active substance is a material selected from the group
consisting of anatase titanium dioxide, carbon-sulfur composite,
carbon-containing materials and carbon fluoride or is lithium
metallic oxides.
[0038] The lithium ion donor of the invention may include but not
be limited to lithium peroxide. For example, lithium oxide is also
suitable to be the lithium ion donor. Alternative, lithium peroxide
and lithium oxide are mixed for the use. In addition, the positive
electrode frame active substance may use carbon-containing
material, and thus both of the positive electrode and negative
electrode use carbon-containing materials to form lithium ion
electric capacity accordingly. Carbon fluorides (CF.sub.x) that
have a high mass capacity ratio are suitable to be the positive
electrode frame active substance of the invention. Si alloy or Sn
alloy that has a very high theoretical electrical capacity is also
suitable to be negative electrode active substance 116 of the
invention.
[0039] An electrolyte that is suitable to a lithium ionic energy
storage element with lithium peroxide/anatase titanium dioxide
system comprises an inorganic compound such as LiPF.sub.6,
LiClO.sub.4 or LiBF.sub.4 and an organic solvent that is a material
selected from the group consisting of ethylene carbonate (EC) and
diethyl carbonate (DEC). In addition, an electrolyte comprises a
concentration of 1M lithium bis(trifluoromethanesulfonly)imide
dissolving in a mixing solution of tetraethylene glycol dimethyl
ether (EGDME) and 1,3-dioxolane (DOL) with mixing ratio 1:1 by
volume that is suitable to a lithium ionic energy storage element
with lithium peroxide/carbon-sulfur system.
[0040] In a charge/discharge mode of the unit cell structure 100 of
the embodiment, lithium peroxide of the positive electrode active
substance 114 is decomposed to lithium ions and oxygen to
intercalate into carbon-containing materials of the negative
electrode 108 when unit cell is charged, and the lithium ions
located in the negative electrode 108 diffuse to the positive
electrode 106 and intercalate in the positive electrode active
substance through the electrolyte when unit cell is discharged.
[0041] At first, electric property of lithium peroxide is
investigated. The lithium ionic energy storage element of the
present invention comprises a lithium ion donor having lithium
peroxide and/or lithium oxide and a positive electrode frame active
substance, wherein lithium peroxide and/or lithium oxide can be
decomposed to produce lithium ions by electrochemical charging, and
lithium ions intercalate repeatedly in and out of the positive
electrode frame active substance and the negative electrode active
substance in a full cell without containing Li ions. Because the
conductivity of lithium peroxide is not high, a conductive carbon
may be added to enhance the conductivity of lithium peroxide.
[0042] The present invention provides a method for making a lithium
ionic energy storage element. At first, lithium peroxide, a
positive electrode frame active substance, e.g. anatase titanium
dioxide, a conductive carbon, for example super P carbon black, KS6
graphite or a combination thereof and a binder, e.g. PVDF are mixed
with a predetermined weight ratio to form a mixture, and the
mixture is added into a dispersant, e.g. N-methyl-2-pyrrolidone
(NMP) to form a slurry. Next, the slurry is coating on an aluminum
foil to form a film by a blade coater. The film is baked in an oven
at a temperature of 80.degree. C. for 6 hours to remove a solvent,
and raise the temperature to 120.degree. C. for 4-6 hours to form a
positive electrode with lithium peroxide/anatase titanium
dioxide.
[0043] A lithium ionic energy storage element is formed by
assembling the positive electrode with lithium peroxide/anatase
titanium dioxide, a negative electrode having a negative electrode
active substance, e.g. graphitized mesocarbon microbeads (MCMB) and
a porous separate strip interposed between the positive electrode
and the negative electrode, and an electrolyte, e.g. a
concentration of 1M LiPF.sub.6 dissolving in a mixing solution of
ethylene carbonate (EC) and diethyl carbonate (DEC) with mixing
ratio 1:1 by volume is filled into the porous separate strip. The
lithium ion donor of the invention may include but not be limited
to lithium peroxide. For example, lithium oxide is also suitable to
be the lithium ion donor. Alternative, lithium peroxide and lithium
oxide are mixed for the use. In addition, the positive electrode
frame active substance may use carbon-containing material, and thus
both of the positive electrode and negative electrode use
carbon-containing materials to form a lithium ion electric capacity
accordingly. Carbon fluorides (CFx) that have a high mass capacity
ratio are suitable to be the positive electrode frame active
substance of the invention. Si alloy or Sn alloy that has a very
high theoretical electrical capacity is also suitable to be
negative electrode active substance 116 of the invention.
[0044] Further, the present invention relates to a method for
making a lithium ionic energy storage element. At first, lithium
peroxide, a positive electrode frame active substance, e.g.
carbon-sulfur composite, a conductive carbon, for example super P
carbon black, KS6 graphite or a combination thereof and a binder,
e.g. carboxymethyl cellulose (CMC) are mixed with a predetermined
weight ratio to form a mixture, and the mixture is added into a
dispersant, e.g. N-methyl-2-pyrrolidone to form a slurry. Next, the
slurry is coating on an aluminum foil to form a film by a blade
coater. The film is baked in an oven at a temperature of
80-90.degree. C. to remove a solvent, and raise the temperature to
120-130.degree. C. for a period of time to form a positive
electrode with lithium peroxide/carbon-sulfur composite.
[0045] The lithium ion donor of the invention may include but not
be limited to lithium peroxide. For example, lithium oxide is also
suitable to be the lithium ion donor. Alternative, lithium peroxide
and lithium oxide are mixed for the use. In addition, the positive
electrode frame active substance may use carbon-containing
material, and thus both of the positive electrode and negative
electrode use carbon-containing materials to form a lithium ion
electric capacity accordingly. Carbon fluorides (CFx) that have a
high mass capacity ratio are suitable to be the positive electrode
frame active substance of the invention. Si alloy or Sn alloy that
has a very high theoretical electrical capacity is also suitable to
be negative electrode active substance 116 of the invention.
[0046] A lithium ionic energy storage element is formed by
assembling the positive electrode with lithium
peroxide/carbon-sulfur composite, a negative electrode having a
negative electrode active substance, e.g. hard carbon and a porous
separate strip interposed between the positive electrode and the
negative electrode, and an electrolyte, e.g. a concentration of 1M
lithium bis(trifluoromethanesulfonly)imide dissolving in a mixing
solution of tetraethylene glycol dimethyl ether (TEGDME) and
1,3-dioxolane (DOL) with mixing ratio 1:1 by volume is filled into
the porous separate strip.
(Performance Determination)
[0047] FIG. 2 shows a first cycle curve of voltage against electric
capacity of a half cell of lithium peroxide charging/discharging of
the invention. FIG. 3 shows a second cycle and a third cycle curves
of voltage against electric capacity of a half cell of lithium
peroxide charging/discharging of the invention. A half cell that is
used for test is formed by assembling a positive electrode formed
with mixing lithium peroxide, super P carbon black and PVDF by
weight ratio of 10:80:10; and a porous separate strip filled with
an electrolyte, e.g. a concentration of 1M LiPF.sub.6 dissolving in
a mixing solution of ethylene carbonate (EC) and diethyl carbonate
(DEC) with mixing ratio 1:1 by volume. Conditions of operation
comprise charging/discharging current of 100 mA/g Li.sub.2O.sub.2
and charging/discharging voltage of 2-4.6V.
[0048] FIG. 4 shows a first cycle curve of voltage against electric
capacity of a half cell of lithium peroxide charging/discharging
under various ratio of a conductive carbon of the invention. A half
cell that is used for test is formed by assembling a positive
electrode formed with mixing lithium peroxide, a conductive carbon
(super P carbon black and KS6 graphite with mixing ratio 1:1 by
weight) and PVDF by weight ratio of X:Y:10, wherein X=80, 60, 45,
30 and 10, and Y=10, 30, 45, 60 and 80; and a porous separate strip
filled with an electrolyte, e.g. a concentration of 1M LiPF.sub.6
dissolving in a mixing solution of ethylene carbonate (EC) and
diethyl carbonate (DEC) with mixing ratio 1:1 by volume. Conditions
of operation comprise charging/discharging current of 10
mA/g.sub.Li2O2 and charging/discharging voltage of 2-4.8V.
[0049] FIG. 5 shows cyclic voltammetry response of lithium peroxide
charging/discharging under various ratio of a conductive carbon of
the invention. A half cell that is used for test is formed by
assembling a positive electrode formed with mixing lithium
peroxide, a conductive carbon (super P carbon black and KS6
graphite with mixing ratio 1:1 by weight) and PVDF by weight ratio
of X:Y:10, wherein X:Y=10:80 and 30:60; and a porous separate strip
filled with an electrolyte, e.g. a concentration of 1M LiPF.sub.6
dissolving in a mixing solution of ethylene carbonate (EC) and
diethyl carbonate (DEC) with mixing ratio 1:1 by volume. Condition
of operation comprises a scan rate of cyclic voltammetry of 0.4
mV/s. The resultant current is 0 mA in the different voltage.
[0050] FIG. 6 shows the influent of voltage against electric
capacity of lithium peroxide in the different current density. A
half cell that is used for test is formed by assembling a positive
electrode formed with mixing lithium peroxide, a conductive carbon
(super P carbon black and KS6 graphite with mixing ratio 1:1 by
weight) and PVDF by weight ratio of 30:60:10; and a porous separate
strip filled with an electrolyte, e.g. a concentration of 1M LiPF6
dissolving in a mixing solution of ethylene carbonate (EC) and
diethyl carbonate (DEC) with mixing ratio 1:1 by volume. Conditions
of operation comprise charging/discharging current of 10 mA/g
Li.sub.2O.sub.2, 30 mA/g Li.sub.2O.sub.2 and 50 mA/g
Li.sub.2O.sub.2 and charging/discharging voltage of 2-4.8V. FIG.
7(a) shows XRD pattern of TiO.sub.2 synthetized from tetrabutyl
titanate of the invention. FIG. 7(b) shows XRD pattern of TiO.sub.2
by simulation. An error of degree (2.theta.) of XRD pattern of
TiO.sub.2 of FIG. 7(a) is obtained within 3% compared with XRD
pattern of TiO.sub.2 of FIG. 7(b).
[0051] The above tests show the various combinations of lithium
peroxide, a conductive carbon and binder, and the influence of
charging and discharging of lithium peroxide in the different
current density. However, lithium peroxide of the positive
electrode is a functional material for use in one time, i.e. only
may be decomposed by charging in one time. Therefore, another
positive electrode active substance, for example anatase titanium
dioxide or carbon-sulfur composite is required to use for receiving
Li ions that may diffuse to the positive electrode from the
negative electrode in a discharging process.
[0052] The initial lithium peroxide may be decomposed to produce Li
ions by charging of the invention that is called as a charging
period of prelithiation, and Li ions diffuse to the positive
electrode from the negative electrode by discharging that is called
as a discharging period of prelithiation. The subsequent Li ions
intercalate in and out in the positive electrode and negative
electrode that is called as a regular working system.
[0053] Please refer to FIG. 8 and FIG. 9. FIG. 8 shows a
charging/discharging curve of prelithiation period of
Li.sub.2O.sub.2/TiO.sub.2 half cell. FIG. 9 shows a
charging/discharging curve of subsequent cycles of
Li.sub.2O.sub.2/TiO.sub.2 half cell. During charging period of
prelithiation, lithium peroxide may be charged to 4.8V against
Li/Li.sup.+ by applying the current density of 50
mA/gLi.sub.2O.sub.2. During discharging period of prelithiation and
subsequent charging/discharging, TiO.sub.2 may be charged and
discharged at 1V-3V against Li/Li.sup.+ by 0.1C (1C=335 mAh/g). The
resultant charging/discharging curves of half cells are shown in
FIG. 8 and FIG. 9. FIG. 8 shows a charging curve of Li.sub.2O.sub.2
with electric capacity of 365 mA/gLi.sub.2O.sub.2 during charging
period of prelithiation and a discharing curve of TiO.sub.2 with
two discharging platforms of 1.8V and 2.7V during discharging
period of prelithiation, wherein the discharging platform of 2.7V
has electric capacity of 100 mAh/gTiO.sub.2 that may be an
oxidation-reduction reaction or regeneration of lithium peroxide,
and it is regarded as a side reaction, i.e. the additional electric
capacity may not belong to TiO.sub.2. Moreover, the resultant
electric capacity may be about 280 mAh/gTiO.sub.2 after 100
mAh/gTiO.sub.2 of the electric capacity of the side reaction is
deducted from 380 mAh/gTiO.sub.2.
[0054] Next, please refer to FIG. 10 and FIG. 11. FIG. 10 shows a
charging/discharging curve of prelithiation period of
Li.sub.2O.sub.2/TiO.sub.2 versus MCMB full cell. FIG. 11 shows a
charging/discharging curve of subsequent cycles of
Li.sub.2O.sub.2/TiO.sub.2 versus MCMB full cell. In the embodiment,
a negative electrode is formed with mixing MCMB: super P carbon
black: KS graphite: binder=70:7.5:7.5:15 by weight; and a positive
electrode is formed with mixing lithium peroxide, a conductive
carbon, binder and titanium dioxide by A/C ratio=1 versus weight of
MCMB powder with calculation of A/C ratio between
Li.sub.2O.sub.2/TiO.sub.2 cathode and MCMB anode as formulas:
Li.sub.2O.sub.2 vs MCMB: (372 mAh/g*0.5 g*0.7)/(410 mAh/g*xg)=1
x=0.4219 g Li.sub.2O.sub.2
TiO.sub.2 vs MCMB: (350 mAh/g*0.5 g*0.7)/(335 mAh/g*yg)=1
y=0.4858 g TiO.sub.2
[0055] According to the formulas based on the electric capacity of
MCMB, the weight of each Li.sub.2O.sub.2, super P carbon black and
KS graphite is 0.4219 g (22%) and the weight of PVDF is 0.1406 g
(7%) and the weight of titanium dioxide is 0.4858 g (27%). During
charging period of prelithiation, lithium peroxide may be charged
to 4.8V against MCMB by applying the current density of 50
mA/gLi.sub.2O.sub.2. During discharging period of prelithiation and
subsequent charging/discharging, TiO.sub.2 may be charged and
discharged at 0-3V against MCMB by 0.1 C (1 C=335 mAh/g). The
resultant charging/discharging curves of half cells are shown in
FIG. 10 and FIG. 11.
[0056] It could be found from the above experiments that Li ions
prelithiation in the positive is successful. However, oxygen is
produced in the process, and will affect the electrochemical
performance. It is important to have an oxygen removal step for
removing oxygen produced in a first cycle of charge and discharge
the lithium ionic energy storage element. In manufacturing a large
scale of lithium ionic battery such as battery with aluminum foil
soft pack (pouch cell), a battery active step is performed in a
first cycle of charging and discharging the lithium ionic battery
after filling the electrolyte into the porous separate strip to
form a solid electrolyte interphase (SEI) on the negative
electrode, and the electrolyte decomposes in part at the same time.
Next, the original electrolyte is withdrawn by evacuation, and a
new electrolyte is filled. Accordingly, a regular charging and
discharging the lithium ionic battery can be performed. FIG. 12
shows a charge/discharge curve of prelithiation period of
Li.sub.2O.sub.2/TiO.sub.2 versus MCMB with disassembling process of
coin cell, and FIG. 13 shows a charge/discharge curve of subsequent
cycles of Li.sub.2O.sub.2/TiO.sub.2 versus MCMB with disassembling
process of coin cell. The effect of removing oxygen is not obvious
from FIG. 12. However, there is not an acute decease in electric
capacity during the subsequent charge/discharge of TiO.sub.2 that
can prove the subsequent charge/discharge of TiO.sub.2 is affected
by the side reaction of the prelithiation discharging period. The
source of the side reaction is the oxygen produced from the
decomposition of lithium peroxide during the prelithiation charging
period.
[0057] In another embodiment, carbon-sulfur composite may be used
for the positive electrode frame active substance of the positive
electrode active substance. Lithium peroxide is mixed with
carbon-sulfur composite to replace Li metal. A full cell is
assembled by the positive electrode having the positive electrode
active substance comprising lithium peroxide and carbon-sulfur
composite and the negative electrode having the negative electrode
active substance comprising hard carbon. Before assembling a full
cell, the electrochemical properties of lithium peroxide and
carbon-sulfur composite in ethers should be determined Because
Li-sulfur battery uses ethers as an electrolyte, a half cell that
is used for test is formed by assembling a positive electrode
formed with mixing lithium peroxide, a conductive carbon and binder
by weight ratio of 30:60:10; and a porous separate strip filled
with an electrolyte, e.g. a concentration of 1M lithium
bis(trifluoromethanesulfonly)imide dissolving in a mixing solution
of tetraethylene glycol dimethyl ether (TEGDME) and 1,3-dioxolane
(DOL) with mixing ratio 1:1 by volume. Conditions of operation
comprise charging/discharging current density of 100 mA/g
Li.sub.2O.sub.2 vs. Li metal and charging/discharging voltage of
2-4.3V in the embodiment, shown as FIG. 14. The cut off voltage of
charging is 4.3V. The half cell is charged for 9 hours by 100
mA/gLi.sub.2O.sub.2 after testing. It can be found the
decomposition of lithium peroxide in Li-sulfur battery electrolyte
system has the overpotential about 4.1V and the resultant electric
capacity about 980 mAh/gLi.sub.2O.sub.2.
[0058] FIG. 15 shows a charge/discharge curve of carbon-sulfur
composite of half cell. The carbon-sulfur composite of the half
cell has a weight ratio of carbon with sulfur is 0.4-1. Conditions
of operation comprise charging/discharging current density of 0.1 C
(1 C=1672 mAh/gs) vs. Li/Li.sup.+ and charging/discharging voltage
of 1.5V-3V in the embodiment, shown as FIG. 15.
[0059] FIG. 16 shows a charge/discharge curve of prelithiation
period of lithium peroxide/carbon-sulfur composite vs. Li/Li.sup.+
of half cell. In the embodiment, a half cell that is used for test
is formed by assembling a positive electrode formed with mixing
lithium peroxide/carbon-sulfur composite, a conductive carbon and a
binder dissolving in a dispersant of N-methyl-2-pyrrolidone; and a
porous separate strip filled with an electrolyte, e.g. a
concentration of 1M lithium bis(trifluoromethanesulfonly)imide
dissolving in a mixing solution of tetraethylene glycol dimethyl
ether (TEGDME) and 1,3-dioxolane (DOL) with mixing ratio 1:1 by
volume. During charging period of prelithiation, lithium peroxide
may be charged with current density of 100 mA/gLi.sub.2O.sub.2 to
4.3V against Li/Li.sup.+ by applying the current density of 50
mA/gLi.sub.2O.sub.2. During discharging period of prelithiation and
subsequent charging/discharging, carbon-sulfur composite may be
charged and discharged against Li/Li.sup.+ by 0.1 C (1 C=1672
mAh/gs). The resultant charging/discharging curves of half cells
are shown in FIG. 16.
[0060] The lithium ionic energy storage element of the present
invention comprises a lithium ion donor having lithium peroxide
and/or lithium oxide and a positive electrode frame active
substance, wherein lithium peroxide and/or lithium oxide can be
decomposed to produce lithium ions by electrochemical charging, and
lithium ions intercalate repeatedly in and out of the positive
electrode frame active substance and the negative electrode active
substance in a full cell. The full cell can exhibit a high
capacity. The positive electrode frame active substance of the
positive electrode active substance can be a material selected from
the group consisting of anatase titanium dioxide, carbon-sulfur
composite, carbon-containing materials and carbon fluoride, but not
limited to the above groups, as long as the materials that are
stable and have excellent electric capacity are suitable as the
positive electrode frame active substance. Even lithium metallic
oxides may be the positive electrode frame active substance to mix
with lithium peroxide and/or lithium oxide as the positive
electrode active substance that can exhibit a higher capacity than
the full cell using lithium metallic oxides only as the positive
electrode active substance.
[0061] The invention is not limited to these embodiments, but
various variations and modifications may be made without departing
from the scope of the invention.
* * * * *