U.S. patent application number 16/992187 was filed with the patent office on 2020-11-26 for composite negative electrode material and method for preparing composite negative electrode material, negative electrode plate of lithium ion secondary battery, and lithium ion secondary battery.
The applicant listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Hui Li, Shengan Xia, Fengchao Xie.
Application Number | 20200373566 16/992187 |
Document ID | / |
Family ID | 1000005016382 |
Filed Date | 2020-11-26 |
United States Patent
Application |
20200373566 |
Kind Code |
A1 |
Xia; Shengan ; et
al. |
November 26, 2020 |
Composite Negative Electrode Material and Method for Preparing
Composite Negative Electrode Material, Negative Electrode Plate of
Lithium Ion Secondary Battery, and Lithium Ion Secondary
Battery
Abstract
A composite negative electrode material, a method for preparing
the composite negative electrode material, a negative electrode
plate of a lithium ion secondary battery containing the composite
negative electrode material, and a lithium ion secondary battery
containing a negative electrode active material of the lithium ion
secondary battery, where the composite negative electrode material
includes a carbon core and a carbon coating layer, where the carbon
coating layer is a carbon layer that coats a surface of the carbon
core, and both the carbon core and the carbon coating layer include
a doping element, where the doping element is at least one of
element N, P, B, S, O, F, Cl, or H.
Inventors: |
Xia; Shengan; (Shenzhen,
CN) ; Li; Hui; (Shenzhen, CN) ; Xie;
Fengchao; (Dongguan, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
|
CN |
|
|
Family ID: |
1000005016382 |
Appl. No.: |
16/992187 |
Filed: |
August 13, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15339081 |
Oct 31, 2016 |
10770720 |
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16992187 |
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PCT/CN2014/088167 |
Oct 9, 2014 |
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15339081 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/366 20130101;
H01M 4/62 20130101; H01M 4/0404 20130101; H01M 2004/027 20130101;
H01M 4/0471 20130101; H01M 10/0525 20130101; H01M 4/587 20130101;
H01M 4/133 20130101 |
International
Class: |
H01M 4/36 20060101
H01M004/36; H01M 4/133 20060101 H01M004/133; H01M 10/0525 20060101
H01M010/0525; H01M 4/587 20060101 H01M004/587; H01M 4/04 20060101
H01M004/04; H01M 4/62 20060101 H01M004/62 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2014 |
CN |
201410177200.4 |
Claims
1. A composite negative electrode, comprising: a carbon core
comprising a first doping element, wherein the first doping element
comprises nitrogen, wherein a nitrogen atom of the first doping
element and a carbon atom in the carbon core are bonded in at least
one form of pyridinic nitrogen, graphite nitrogen, or pyrrolic
nitrogen; and a carbon coating layer comprising a carbon layer that
coats a surface of the carbon core, wherein the carbon coating
layer comprises a second doping element that is Phosphorus (P),
Boron (B), Sulfur (S), Oxygen (O), Fluorine (F), Chlorine (Cl), or
Hydrogen (H), and wherein the first doping element is different
from the second doping element.
2. The composite negative electrode of claim 1, wherein a mass of
the carbon coating layer is 5 percent (%) to 30% of a total mass of
the carbon coating layer and the carbon core.
3. The composite negative electrode of claim 1, wherein a mass of
the first doping element and the second doping element in the
composite negative electrode is 0.1 percent (%) to 50%.
4. The composite negative electrode of claim 1, wherein the carbon
core comprises natural graphite.
5. The composite negative electrode of claim 1, wherein the carbon
core comprises artificial graphite.
6. The composite negative electrode of claim 1, wherein the carbon
core comprises expanded graphite.
7. The composite negative electrode of claim 1, wherein the carbon
core comprises graphite oxide.
8. The composite negative electrode of claim 1, wherein the carbon
core comprises hard carbon.
9. The composite negative electrode of claim 1, wherein the carbon
core comprises soft carbon.
10. The composite negative electrode of claim 1, wherein the carbon
core comprises at least one of graphene, carbon nanotube, or carbon
fiber.
11. A negative electrode plate of a lithium ion secondary battery,
comprising: a current collector; and a composite negative electrode
material that covers the current collector, wherein the composite
negative electrode material comprises: a carbon core comprising a
first doping element, wherein the first doping element comprises
nitrogen, wherein a nitrogen atom of the first doping element and a
carbon atom in the carbon core are bonded in at least one form of
pyridinic nitrogen, graphite nitrogen, or pyrrolic nitrogen; and a
carbon coating layer comprising a carbon layer that coats a surface
of the carbon core, wherein the carbon coating layer comprises a
second doping element that is Nitrogen (N), Phosphorus (P), Boron
(B), Sulfur (S), Oxygen (O), Fluorine (F), Chlorine (Cl), or
Hydrogen (H), and wherein the first doping element is different
from the second doping element.
12. The negative electrode plate of claim 11, wherein a mass of the
carbon coating layer is 5 percent (%) to 30% of a total mass of the
carbon coating layer and the carbon core.
13. The negative electrode plate of claim 11, wherein a mass of the
first doping element and the second doping element in the composite
negative electrode material is 0.1 percent (%) to 50%.
14. The negative electrode plate of claim 11, wherein the carbon
core comprises natural graphite.
15. The negative electrode plate of claim 11, wherein the carbon
core comprises at least one of graphene, carbon nanotube, or carbon
fiber.
16. A lithium ion secondary battery comprising: a negative
electrode plate comprising: a current collector; and a composite
negative electrode material covering the current collector and
comprising: a carbon core comprising a first doping element,
wherein the first doping element comprises nitrogen, wherein a
nitrogen atom of the first doping element and a carbon atom in the
carbon core are bonded in at least one form of pyridinic nitrogen,
graphite nitrogen, or pyrrolic nitrogen; and a carbon coating layer
comprising a carbon layer that coats a surface of the carbon core,
wherein the carbon coating layer comprises a second doping element
that is Nitrogen (N), Phosphorus (P), Boron (B), Sulfur (S), Oxygen
(O), Fluorine (F), Chlorine (Cl), or Hydrogen (H), and wherein the
first doping element is different from the second doping element; a
positive electrode; a separator separating the negative electrode
plate and positive electrode from each other; a non-aqueous
electrolyte; and a shell that houses the negative electrode plate,
the positive electrode, the separator, and the non-aqueous
electrolyte.
17. The lithium ion secondary battery of claim 16, wherein a mass
of the carbon coating layer is 5 percent (%) to 30% of a total mass
of the carbon coating layer and the carbon core.
18. The lithium ion secondary battery of claim 16, wherein a mass
of the first doping element and the second doping element in the
composite negative electrode material is 0.1 percent (%) to
50%.
19. The lithium ion secondary battery of claim 16, wherein the
carbon core comprises natural graphite.
20. The lithium ion secondary battery of claim 16, wherein the
carbon core comprises at least one of graphene, carbon nanotube, or
carbon fiber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/339,081, filed on Oct. 31, 2016, which is a
continuation of International Patent Application No.
PCT/CN2014/088167, filed on Oct. 9, 2014, which claims priority to
Chinese Patent Application No. 201410177200.4, filed on Apr. 29,
2014. All of the aforementioned patent applications are hereby
incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] The present disclosure relates to the field of lithium ion
secondary batteries, and in particular, to a composite negative
electrode material and a method for preparing the composite
negative electrode material, a negative electrode plate of a
lithium ion secondary battery, and a lithium ion secondary
battery.
BACKGROUND
[0003] A graphite negative electrode material of a lithium battery
has advantages such as a long cycle life, high initial efficiency,
low costs, environmentally friendliness, and ease of processing.
Therefore, this material has been widely applied in fields of
portable electronic devices, electric vehicles, and energy
storage.
[0004] However, a theoretical specific capacity of graphite is
relatively low (about 372 milliampere hours (mAh)/gram (g)), and
the graphite has poor compatibility with electrolyte and has poor
rate performance. Although compatibility between the graphite and
the electrolyte is improved using a carbon coating technology, the
rate performance of the graphite is still hard to be improved, and
a capacity of the graphite almost reaches a limit.
SUMMARY
[0005] In view of this, a first aspect of embodiments of the
present disclosure provides a composite negative electrode material
that features a high capacity, low costs, a long service life, and
high-rate charging and discharging, where the composite negative
electrode material can break through theoretical capacity and rate
limits of a graphite negative electrode.
[0006] According to the first aspect, an embodiment of the present
disclosure provides a composite negative electrode material, where
the composite negative electrode material includes a carbon core
and a carbon coating layer, where the carbon coating layer is a
carbon layer that coats a surface of the carbon core, and the
carbon core includes a first doping element, where the first doping
element is at least one of element N, P, B, S, O, F, Cl, or H.
[0007] With reference to the first aspect, in a first feasible
manner of the first aspect, the carbon coating layer includes a
second doping element, where the second doping element is at least
one of element N, P, B, S, O, F, Cl, or H, and the first doping
element and the second doping element may be the same or may be
different.
[0008] With reference to the first aspect or the first feasible
manner of the first aspect, in a second feasible manner of the
first aspect, a mass of the carbon coating layer is 5% to 30% a
total mass of the carbon coating layer and the carbon core.
[0009] With reference to the first aspect or the first feasible
manner of the first aspect or the second feasible manner of the
first aspect, in a third feasible manner of the first aspect, a
mass content of the doping elements in the composite negative
electrode material is 0.1% to 50%.
[0010] With reference to the first aspect or the first feasible
manner of the first aspect or the second feasible manner of the
first aspect or the third feasible manner of the first aspect, in a
fourth feasible manner of the first aspect, the carbon core
includes at least one type of natural graphite, artificial
graphite, expanded graphite, graphite oxide, hard carbon, soft
carbon, graphene, carbon nanotube, or carbon fiber.
[0011] According to a second aspect, an embodiment of the present
disclosure provides a method for preparing the composite negative
electrode material according to any one of the first aspect,
includes mixing and shaking ionic liquid (such as triphenyl boron,
3-methyl-butyl pyridinium dicyanamide, or
1-ethyl-3-methylimidazolium dicyanamide) and a carbon material, to
obtain a first compound, and placing the first compound in a tube
furnace, pumping in a gas mixture of inert carrier gas and hydride
containing a doping element, and performing calcination to obtain
the composite negative electrode material.
[0012] With reference to the second aspect, in a first possible
implementation manner of the second aspect, a time for mixing and
shaking the ionic liquid and the carbon material is 30 minutes to
120 minutes. The pumping in a gas mixture of inert carrier gas and
hydride containing a doping element includes pumping in the gas
mixture of the inert carrier gas and the hydride containing a
doping element at a rate of 5 milliliters (ml or mL)/minute (min)
to 100 ml/min, where a ratio of a volume of the hydride containing
a doping element to a volume of the inert gas is 1:1 to 1:10, and
performing calcination to obtain the composite negative electrode
material further includes heating up the tube furnace to 500
Celsius (.degree. C.) to 1000.degree. C. at a heating rate of
1.degree. C./min to 10.degree. C./min, and preserving heat for 0.5
hour to 12 hours, where the composite negative electrode material
can be obtained after the tube furnace cools to a room
temperature.
[0013] According to a third aspect, an embodiment of the present
disclosure provides a method for preparing the composite negative
electrode material according to any one of the first aspect,
includes placing a carbon material in a tube furnace, vacuumizing
the tube furnace, pumping a gas mixture of inert carrier gas and
hydride containing a doping element into the tube furnace, and
preserving heat at a temperature of 500.degree. C. to 1000.degree.
C. for 1 hour to 12 hours, and pumping a gas mixture of inert
carrier gas and a small organic molecule containing a doping
element into the tube furnace, and preserving heat at a temperature
of 500.degree. C. to 1000.degree. C. for 1 hour to 12 hours, to
obtain the composite negative electrode material, where the small
organic molecule includes one type of pyridinium, pyrrole, or
thiophene.
[0014] With reference to the third aspect, in a first possible
implementation manner of the third aspect, a ratio of a volume of
the hydride containing a doping element to a volume of the inert
carrier gas is 1:1 to 1:10, and a ratio of a volume of the small
organic molecule containing a doping element to a volume of the
inert carrier gas is 1:1 to 1:10.
[0015] According to a fourth aspect, an embodiment of the present
disclosure provides a method for preparing the composite negative
electrode material according to any one of the first aspect,
includes dissolving surfactant (such as cetyl trimethyl ammonium
bromide, sodium dodecyl benzene sulfonate, or sodium carboxy methyl
cellulose) in acid (such as hydrochloric acid (HCl), sulfuric acid,
nitric acid, or phosphoric acid), to obtain a first mixed solution,
using ultrasound to disperse a carbon material in the first mixed
solution, and adding in oxidant (such as ammonium persulfate,
ferric trichloride, or ferric sulfate), to obtain turbid liquid,
adding a pyrrole monomer to the turbid liquid, to obtain a second
mixed solution, performing heat reaction on the second mixed
solution, to obtain a black sediment, and washing the black
sediment until the black sediment becomes neutral and drying the
black sediment, placing the dried black sediment in a tube furnace,
pumping in a gas mixture of inert carrier gas and hydride
containing a doping element, and performing sintering, to obtain
the composite negative electrode material.
[0016] With reference to the fourth aspect, in a first possible
implementation manner of the fourth aspect, performing heat
reaction on the second mixed solution, to obtain a black sediment
further includes performing heat reaction on the second mixed
solution at a temperature of 0.degree. C. to 4.degree. C. for 1 h
to 24 h and then performing filtering, to obtain the black
sediment, and washing the black sediment until the black sediment
becomes neutral and drying the black sediment, placing the dried
black sediment in a tube furnace, pumping in a gas mixture of inert
carrier gas and hydride containing a doping element, and performing
sintering, to obtain the composite negative electrode material
further includes using a hydrogen chloride solution to wash the
black sediment until the black sediment becomes neutral and drying
the black sediment at 50.degree. C. to 100.degree. C. for 1 hour to
24 hours, placing the dried black sediment in the tube furnace,
pumping in the gas mixture of the inert carrier gas and the hydride
containing a doping element, and performing sintering at
500.degree. C. to 1000.degree. C. for 0.5 hour to 10 hours, to
obtain the composite negative electrode material.
[0017] According to a fifth aspect, an embodiment of the present
disclosure provides a negative electrode plate of a lithium ion
secondary battery, where the negative electrode plate of the
lithium ion secondary battery includes a current collector and a
composite negative electrode material that covers the current
collector.
[0018] According to a sixth aspect, an embodiment of the present
disclosure provides a lithium ion secondary battery, where the
lithium ion secondary battery includes a negative electrode plate
of the lithium ion secondary battery, a positive electrode, a
separator, a non-aqueous electrolyte, and a shell, and the negative
electrode plate of the lithium ion secondary battery includes a
current collector and a composite negative electrode material that
covers the current collector.
[0019] It can be learned from the foregoing description that, the
composite negative electrode material provided in the first aspect
of the embodiments of the present disclosure includes a graphite
core and a carbon coating layer, and both the graphite core and the
carbon coating layer are doped with an element. The doping element
is used to form a lattice defect at a carbon layer, which not only
can improve electron cloud mobility, but also can reduce energy
barriers of lithium storage, increase lithium storage binding
sites, increase a distance between graphite carbon layers, greatly
improve a migration speed of lithium ions, and break through a
theoretical capacity of 372 mAh/g of graphite, thereby improving a
capacity and rate performance of the composite negative electrode
material. The method, provided in the second aspect to the fourth
aspect of the embodiments of the present disclosure, for preparing
the composite negative electrode material according to any one of
the first aspect features simple and convenient processing and low
costs, and is easy for industrialized production. The negative
electrode plate, of the lithium ion secondary battery, provided in
the fifth aspect of the embodiments of the present disclosure and
the lithium ion secondary battery provided in the sixth aspect
feature a long service life and good electrical conductivity.
[0020] Advantages of the embodiments of the present disclosure are
partially described in the following specification, and some
advantages are obvious according to the specification, or may be
learned through implementation of the embodiments of the present
disclosure.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a scanning electron microscope (SEM) diagram of a
composite negative electrode material prepared in Embodiment 1 of
the present disclosure.
[0022] FIG. 2 is a diagram of charge and discharge cycles of a
button battery at different rates in Embodiment 1 of the present
disclosure.
[0023] FIG. 3 is an X-ray photoelectron spectroscopy (XPS) spectrum
of a composite negative electrode material at different charging
statuses in Embodiment 1 of the present disclosure.
DESCRIPTION OF EMBODIMENTS
[0024] The following descriptions are optional implementation
manners of embodiments of the present disclosure. It should be
noted that a person of ordinary skill in the art may make certain
improvements and polishing without departing from the principle of
the present disclosure and the improvements and polishing shall
fall within the protection scope of the present disclosure.
[0025] A first aspect of the embodiments of the present disclosure
provides a composite negative electrode material, which resolves a
problem that rate performance is hard to be improved and a capacity
almost reaches a limit. A second aspect to a fourth aspect of the
embodiments of the present disclosure provide a method for
preparing the composite negative electrode material according to
the first aspect. The method features simple and convenient
processing and low costs, and is easy for industrialized
production. A fifth aspect of the embodiments of the present
disclosure provides a negative electrode plate of a lithium ion
secondary battery that contains the composite negative electrode
material according to the first aspect, and a sixth aspect of the
embodiments of the present disclosure provides a lithium ion
secondary battery that contains the composite negative electrode
material according to the first aspect.
[0026] According to the first aspect, an embodiment of the present
disclosure provides a composite negative electrode material, where
the composite negative electrode material includes a carbon core
and a carbon coating layer, where the carbon coating layer is a
carbon layer that coats a surface of the carbon core, and the
carbon core includes a first doping element, where the first doping
element is at least one of element N, P, B, S, O, F, Cl, or H.
[0027] Optionally, the carbon coating layer includes a second
doping element, where the second doping element is at least one of
element N, P, B, S, O, F, Cl, or H, and the first doping element
and the second doping element may be the same or may be
different.
[0028] Optionally, a mass of the carbon coating layer is 5% to 30%
a total mass of the carbon coating layer and the carbon core.
[0029] Optionally, a mass content of the doping elements in the
composite negative electrode material is 0.1% to 50%.
[0030] Optionally, the carbon core includes at least one type of
natural graphite, artificial graphite, expanded graphite, graphite
oxide, hard carbon, soft carbon, graphene, carbon nanotube, or
carbon fiber.
[0031] The first aspect of the embodiments of the present
disclosure provides a composite negative electrode material, where
the composite negative electrode material includes a graphite core
and a carbon coating layer, and both the graphite core and the
carbon coating layer are doped with an element. The doping element
is used to form a lattice defect at a carbon layer, which not only
can improve electron cloud mobility, but also can reduce energy
barriers of lithium storage, increase lithium storage binding
sites, increase a distance between graphite carbon layers, greatly
improve a migration speed of lithium ions, and break through a
theoretical capacity of 372 mAh/g of graphite, thereby improving a
capacity and rate performance of the composite negative electrode
material.
[0032] According to the second aspect, an embodiment of the present
disclosure provides a method for preparing the composite negative
electrode material according to the first aspect, where the
composite negative electrode material is prepared according to one
of the following methods.
[0033] Method 1: Mixing and shaking ionic liquid (such as triphenyl
boron, 3-methyl-butyl pyridinium dicyanamide, or
1-ethyl-3-methylimidazolium dicyanamide) and a carbon material, to
obtain a first compound, and placing the first compound in a tube
furnace, pumping in a gas mixture of inert carrier gas and hydride
containing a doping element, and performing calcination to obtain
the composite negative electrode material.
[0034] Optionally, in method 1, a time for mixing and shaking the
ionic liquid and the carbon material is 30 minutes to 120 minutes,
the gas mixture of the inert carrier gas and the hydride containing
a doping element is pumped in at a rate of 5 ml/min to 100 ml/min,
and a ratio of a volume of the hydride containing a doping element
to a volume of the inert gas is 1:1 to 1:10, and performing
calcination to obtain the composite negative electrode material
further includes heating up the tube furnace to 500.degree. C. to
1000.degree. C. at a heating rate of 1.degree. C./min to 10.degree.
C./min, and preserving heat for 0.5 hour to 12 hours, where the
composite negative electrode material can be obtained after the
tube furnace cools to a room temperature.
[0035] Method 2: Placing a carbon material in a tube furnace,
vacuumizing the tube furnace, pumping a gas mixture of inert
carrier gas and hydride containing a doping element into the tube
furnace, and preserving heat at a temperature of 500.degree. C. to
1000.degree. C. for 1 hour to 12 hours, and pumping a gas mixture
of inert carrier gas and a small organic molecule containing a
doping element into the tube furnace, and preserving heat at a
temperature of 500.degree. C. to 1000.degree. C. for 1 hour to 12
hours, to obtain the composite negative electrode material, where
the small organic molecule includes one type of pyridinium,
pyrrole, or thiophene.
[0036] Optionally, in method 2, a ratio of a volume of the hydride
containing a doping element to a volume of the inert carrier gas is
1:1 to 1:10, and a ratio of a volume of the small organic molecule
containing a doping element to a volume of the inert carrier gas is
1:1 to 1:10.
[0037] Method 3: Dissolving surfactant (such as cetyl trimethyl
ammonium bromide, sodium dodecyl benzene sulfonate, or sodium
carboxy methyl cellulose) in acid (such as HCl, sulfuric acid,
nitric acid, or phosphoric acid), to obtain a first mixed solution,
using ultrasound to disperse a carbon material in the first mixed
solution, and adding in oxidant (such as ammonium persulfate,
ferric trichloride, or ferric sulfate), to obtain turbid liquid,
adding a pyrrole monomer to the turbid liquid, to obtain a second
mixed solution, performing heat reaction on the second mixed
solution, to obtain a black sediment, and washing the black
sediment until the black sediment becomes neutral and drying the
black sediment, placing the dried black sediment in a tube furnace,
pumping in a gas mixture of inert carrier gas and hydride
containing a doping element, and performing sintering, to obtain
the composite negative electrode material.
[0038] Optionally, in method 3, performing heat reaction on the
second mixed solution, to obtain a black sediment further includes
performing heat reaction on the second mixed solution at a
temperature of 0.degree. C. to 4.degree. C. for 1 h to 24 h and
then performing filtering, to obtain the black sediment, and
washing the black sediment until the black sediment becomes neutral
and drying the black sediment, placing the dried black sediment in
a tube furnace, pumping in a gas mixture of inert carrier gas and
hydride containing a doping element, and performing sintering, to
obtain the composite negative electrode material further includes
using a hydrogen chloride solution to wash the black sediment until
the black sediment becomes neutral and drying the black sediment at
50.degree. C. to 100.degree. C. for 1 hour to 24 hours, placing the
dried black sediment in the tube furnace, pumping in the gas
mixture of the inert carrier gas and the hydride containing a
doping element, and performing sintering at 500.degree. C. to
1000.degree. C. for 0.5 hour to 10 hours, to obtain the composite
negative electrode material.
[0039] A method, for preparing a negative electrode active material
of a lithium ion secondary battery, provided in the second aspect
of the embodiments of the present disclosure features simple and
convenient processing and low costs, and is easy for industrialized
production.
[0040] According to the third aspect, an embodiment of the present
disclosure provides a negative electrode plate of a lithium ion
secondary battery, where the negative electrode plate of the
lithium ion secondary battery includes a current collector and a
composite negative electrode material that covers the current
collector. The negative electrode plate of the lithium ion
secondary battery provided in the third aspect of the embodiments
of the present disclosure features a long service life and good
electrical conductivity, where the negative electrode active
material of the lithium ion secondary battery is described in the
first aspect.
[0041] According to a fourth aspect, an embodiment of the present
disclosure provides a lithium ion secondary battery, where the
lithium ion secondary battery includes a negative electrode plate
of the lithium ion secondary battery, a positive electrode, a
separator, a non-aqueous electrolyte, and a shell, and the negative
electrode plate of the lithium ion secondary battery includes a
current collector and a composite negative electrode material that
covers the current collector. The lithium ion secondary battery
provided in the fourth aspect of the embodiments of the present
disclosure features a long service life and good electrical
conductivity, where the negative electrode active material of the
lithium ion secondary battery is described in the first aspect.
[0042] The following uses multiple embodiments to further describe
the embodiments of the present disclosure. The embodiments of the
present disclosure are not limited to the following specific
embodiments, and can be properly modified for implementation
without changing a scope of independent claims.
Embodiment 1
[0043] A method for preparing a composite negative electrode
material, includes dissolving 7.3 g of cetyl trimethyl ammonium
bromide (CTAB, (C.sub.16H.sub.33)N(CH.sub.3).sub.3Br) in an
ice-water-bathed HCl (120 mL, 1 mole (mol)/liter (L)) solution,
adding in 10 g of natural graphite, performing ultrasonic
dispersion for 30 minutes, and then adding in ammonium persulfate
(APS) 13.7 g, where white turbid liquid is immediately obtained,
adding in 8.3 mL of a pyrrole monomer (Pyrrole) after stirring for
0.5 hour, performing heat reaction at 4.degree. C. for 24 h, and
then performing filtering, using an HCl solution of 1 mol/L to wash
an obtained black sediment three times and then using purified
water to wash the sediment until a solution becomes colorless and
neutral. After that, drying the sediment at 80.degree. C. for 24 h.
Finally, placing the dried sediment in a tube furnace, pumping in a
gas mixture of 10% N.sub.2H.sub.4/Ar, and performing sintering at
700.degree. C. for 5 hours, to obtain the composite negative
electrode material. FIG. 1 is an SEM diagram of the composite
negative electrode material.
[0044] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3 molar (M) LiPF6 in a solution of ethylene
carbonate (EC) and diethyl carbonate (DEC) (where a volume ratio is
3:7).
[0045] As shown in FIG. 2, FIG. 2 is a diagram of charge and
discharge cycles of the obtained button battery at different
currents, where a capacity reaches 460 mAh/g at 1.times.capacity of
the battery (1 C) and a capacity retention rate is 50% at 30 C.
[0046] As shown in FIG. 3, FIG. 3 is an XPS spectrum of the
composite negative electrode material at different charging
statuses. It can be seen from the figure that, N1s peaks before
lithium is inserted can be fit to three sub-peaks located at 398.2
electron volt (eV), 399.7 eV, and 401.2 eV, which belong to
pyridinium-N, pyrrole-N, and graphite-N, respectively. After
lithium is fully inserted to the electrode, a peak position of the
pyridinium-N is moved to 387.5 eV. This indicates that an oxidation
state of the pyridinium-N becomes more negative, and therefore,
bond energy is lowered. Position movement of this peak proves that
the pyridinium-N can bind with Li+ to form a bond. After lithium is
completely extracted, a peak position of the pyridinium-N is back
to the original position, which indicates that the Li+ almost
completely breaks away from the original position of the
pyridinium-N. The foregoing phenomena prove that the Li+ can
reversely bond with an N-activated site, especially a pyridinium-N
site.
Embodiment 2
[0047] A method for preparing a composite negative electrode
material, includes dissolving 7.3 g of CTAB in an ice-water-bathed
HCl (120 mL, 1 mol/L) solution, adding in 10 g of artificial
graphite, performing ultrasonic dispersion for 30 minutes, and then
adding in 13.7 g of APS, where white turbid liquid is immediately
obtained, adding in 8.3 mL of a Pyrrole after stirring for 0.5
hour, performing heat reaction at 4.degree. C. for 24 h, and then
performing filtering, using an HCl solution of 1 mol/L to wash an
obtained black sediment three times and then using purified water
to wash the sediment until a solution becomes colorless and
neutral. After that, drying the sediment at 80.degree. C. for 24 h.
Finally, placing the dried sediment in a tube furnace, pumping in a
gas mixture of 15% PH.sub.3/Ar at a rate of flow controlled at 20
ml/min, heating up the tube furnace to 700.degree. C. at a heating
rate of 2.degree. C./min, and preserving heat for 5 hours, to
obtain the composite negative electrode material.
[0048] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 3:7). A capacity of the obtained button battery
reaches 620 mAh/g at 1 C, and a capacity retention rate is 43% at
30 C.
Embodiment 3
[0049] A method for preparing a composite negative electrode
material, includes that in a dry atmosphere, after evenly mixing 5
g of triphenyl boron and 1 g of expanded graphite, performing
shaking and mixing, where the shaking takes 60 min, transferring
the compound to a crucible and placing the crucible to a tube
furnace, pumping in a gas mixture of 30% NH.sub.3/Ar at a rate of
flow controlled at 10 ml/min, heating up the tube furnace to
800.degree. C. at a heating rate of 2.degree. C./min, and
preserving heat for 6 hours, and then pumping in, as reaction gas,
a thiophene monomer gasified using Ar carrier gas (4:1 volume
(v)/v), where a rate of Ar flow is controlled at 250 ml/min, and
preserving heat for 3 hours, where the composite negative electrode
material can be obtained after the tube furnace cools to a room
temperature.
[0050] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 3:7). A capacity of the obtained button battery
reaches 510 mAh/g at 1 C, and a capacity retention rate is 44% at
30 C.
Embodiment 4
[0051] A method for preparing a composite negative electrode
material, includes that in a dry atmosphere, after evenly mixing 5
g of triphenyl boron and 1 g of expanded graphite, performing
shaking and mixing, where the shaking takes 60 min, transferring
the compound to a crucible and placing the crucible to a tube
furnace, pumping in a gas mixture of 30% NH.sub.3/Ar at a rate of
flow controlled at 10 ml/min, heating up the tube furnace to
800.degree. C. at a heating rate of 2.degree. C./min, and
preserving heat for 6 hours, where the composite negative electrode
material can be obtained after the tube furnace cools to a room
temperature.
[0052] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 37). A capacity of the obtained button battery
reaches 540 mAh/g at 1 C, and a capacity retention rate is 51% at
30 C.
Embodiment 5
[0053] A method for preparing a composite negative electrode
material, includes that in a dry atmosphere, after evenly mixing 5
g of triphenyl boron and 1 g of hard carbon, performing shaking and
mixing, where the shaking takes 60 min, transferring the compound
to a crucible and placing the crucible to a tube furnace, pumping
in a gas mixture of 10% H.sub.2S/Ar at a rate of flow controlled at
30 ml/min, heating up the tube furnace to 600.degree. C. at a
heating rate of 2.degree. C./min, and preserving heat for 4 hours,
where the composite negative electrode material can be obtained
after the tube furnace cools to a room temperature.
[0054] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 3:7). A capacity of the obtained button battery
reaches 420 mAh/g at 1 C, and a capacity retention rate is 42% at
30 C.
Embodiment 6
[0055] A method for preparing a composite negative electrode
material, includes placing 3 g of natural graphite in a tube
furnace, vacuumizing the tube furnace, first pumping in, as
reaction gas, BCl.sub.3 gasified using Ar carrier gas (4:1 v/v),
where a rate of Ar flow is controlled at 250 ml/min, heating up the
tube furnace to 800.degree. C. at a heating rate of 30.degree.
C./min, and preserving heat for 3 hours, and then pumping in, as
reaction gas, a pyridinium monomer gasified using Ar carrier gas
(5:1 v/v), where a rate of Ar flow is controlled at 50 ml/min, and
preserving heat for 6 hours, where the composite negative electrode
material can be obtained after the tube furnace cools to a room
temperature.
[0056] The prepared composite negative electrode active material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 3:7). A capacity of the obtained button battery
reaches 450 mAh/g at 1 C, and a capacity retention rate is 20% at
30 C.
Embodiment 7
[0057] A method for preparing a composite negative electrode
material, includes placing 3 g of artificial graphite in a tube
furnace, vacuumizing the tube furnace, first pumping in, as
reaction gas, a pyrrole monomer gasified using Ar carrier gas (5:1
v/v), where a rate of Ar flow is controlled at 50 ml/min, heating
up the tube furnace to 800.degree. C. at a heating rate of
30.degree. C./min, and preserving heat for 6 hours, and then
pumping in 25% PH.sub.3/Ar, where a rate of flow is controlled at
100 ml/min, and preserving heat for 4 hours, where the composite
negative electrode material can be obtained after the tube furnace
cools to a room temperature.
[0058] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 3:7). A capacity of the obtained button battery
reaches 430 mAh/g at 1 C, and a capacity retention rate is 25% at
30 C.
[0059] Comparison Example 1 placing 3 g of natural graphite in a
tube furnace, vacuumizing the tube furnace, pumping in Ar/methane
(where a volume ratio is 8:2) as reaction gas, where a rate of air
flow is controlled at 50 ml/min, heating up the tube furnace to
700.degree. C. at a heating rate of 30.degree. C./min, and
preserving heat for 6 hours, where a carbon-coated graphite
negative electrode material can be obtained after the tube furnace
cools to a room temperature.
[0060] The prepared composite negative electrode material,
conductive black, and polyvinylidene fluoride are mixed at a mass
ratio of 85:10:5 in N-Methylpyrrolidone, and are evenly smeared on
a copper foil current collector. The copper foil current collector
is dried in a vacuum at 120.degree. C., to obtain an electrode
plate. Then, the electrode plate is assembled, in a glove box, into
a button battery, and a test is performed. In the button battery,
an electrode uses lithium metal, a separator is celgard C2400, and
an electrolyte is 1.3M LiPF6 in a solution of EC and DEC (where a
volume ratio is 3:7). A capacity of the obtained button battery
reaches 365 mAh/g at 1 C, and a capacity retention rate is 5% at 30
C.
[0061] It can be learned, according to Embodiment 7 and Comparison
Example 1, that an actual capacity of the composite negative
electrode material breaks through a theoretical capacity (which is
372 mAh/g at present) of a conventional graphite negative electrode
material, and the composite negative electrode material greatly
improves rapid-charge and rapid-discharge capabilities of a
graphite material.
EFFECT EMBODIMENT
[0062] To strongly support beneficial effects of the embodiments of
the present disclosure, an effect embodiment is provided as follows
and is used to evaluate performance of a product provided in the
embodiments of the present disclosure.
[0063] It can be learned from Embodiment 1 to Embodiment 7 of the
present disclosure that when compared with a carbon-coating
graphite negative electrode material prepared at a same temperature
in Comparison Example 1, a prepared composite negative electrode
material has a high capacity and rapid-charge and rapid-discharge
capabilities. This is because a doping element forms a lattice
defect at a carbon layer, which not only can improve electron cloud
mobility, but also can reduce energy barriers of lithium storage,
increase lithium storage binding sites, increase a distance between
graphite carbon layers, greatly improve a migration speed of
lithium ions, and break through a theoretical capacity of 372 mAh/g
of graphite.
* * * * *