U.S. patent application number 15/846869 was filed with the patent office on 2019-03-07 for lithium ion secondary battery.
This patent application is currently assigned to Contemporary Amperex Technology Co., Limited. The applicant listed for this patent is Contemporary Amperex Technology Co., Limited. Invention is credited to Libing He, Jianjun Ma, Rui Shen.
Application Number | 20190074539 15/846869 |
Document ID | / |
Family ID | 60629596 |
Filed Date | 2019-03-07 |
United States Patent
Application |
20190074539 |
Kind Code |
A1 |
Shen; Rui ; et al. |
March 7, 2019 |
LITHIUM ION SECONDARY BATTERY
Abstract
The present application relates to a lithium ion secondary
battery comprising a cathode, an anode, a separator and an
electrolyte; wherein the cathode comprises a positive current
collector and a positive material layer, wherein the positive
material layer comprises a positive active material with a formula
Li.sub.xNi.sub.aCo.sub.bM.sub.cO.sub.2, M is at least one selected
from Mn and Al, 0.95x1.2, 0<a<1,0<b<1,0<c<1 and
a+b+c=1; wherein the anode comprises a negative current collector
and a negative material layer, wherein the negative material layer
comprises graphite having a graphitization degree of 92% to 98% and
an average particle size D50 of 6 .mu.m to 18 .mu.m as negative
active material. The lithium ion secondary battery has long cycle
life and high energy density.
Inventors: |
Shen; Rui; (Ningde City,
CN) ; Ma; Jianjun; (Ningde City,, CN) ; He;
Libing; (Ningde City, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Contemporary Amperex Technology Co., Limited |
Ningde City |
|
CN |
|
|
Assignee: |
Contemporary Amperex Technology
Co., Limited
Ningde City,
CN
|
Family ID: |
60629596 |
Appl. No.: |
15/846869 |
Filed: |
December 19, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2004/027 20130101;
H01M 4/133 20130101; H01M 2004/021 20130101; H01M 10/0525 20130101;
Y02E 60/10 20130101; H01M 4/131 20130101; H01M 2004/028 20130101;
H01M 4/626 20130101; H01M 4/583 20130101; H01M 4/485 20130101; H01M
4/505 20130101; H01M 4/525 20130101; H01M 4/587 20130101 |
International
Class: |
H01M 10/0525 20060101
H01M010/0525; H01M 4/525 20060101 H01M004/525; H01M 4/485 20060101
H01M004/485; H01M 4/583 20060101 H01M004/583 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2017 |
CN |
201710795465.4 |
Claims
1. A lithium ion secondary battery comprising a cathode, an anode,
a separator and an electrolyte, the cathode comprises a positive
current collector and a positive material layer, wherein the
positive material layer comprises a positive active material with
formula Li.sub.xNi.sub.aCo.sub.bM.sub.cO.sub.2, M is at least one
selected from the group consisting of Mn and Al,
0.95x1.2,0<a<1,0<b<1,0<c<1 and a+b+c=1; wherein
the anode comprises a negative current collector and a negative
material layer, wherein the negative material layer comprises
graphite having a graphitization degree of 92% to 98% and an
average particle size D50 of 6 .mu.m to 18 .mu.m as negative active
material.
2. The lithium ion secondary battery according to claim 1, wherein
the positive active material is at least one selected from the
group consisting of LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2,
LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2,
LiNi.sub.0.5Co.sub.0.25Mn.sub.0.25O.sub.2,
LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2,
LiNi.sub.0.85Co.sub.0.1Mn.sub.0.05O.sub.2 and
LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2.
3. The lithium ion secondary battery according to claim 1, wherein
the positive active material has dopant element at least one
selected from the group consisting of Al, Zr, Ti, B, Mg, V, Cr, and
F.
4. The lithium ion secondary battery according to claim 1, wherein
the positive active material has coating layer and the coating
layer contains at least one of the elements selected from Al, Zr,
Ti, and B.
5. The lithium ion secondary battery according to claim 1, wherein
the average particle diameter D50 of the negative active material
is 6 .mu.m to 12 .mu.m.
6. The lithium ion secondary battery according to claim 1, wherein
the graphitization degree of the negative active material is 92% to
96%.
7. The lithium ion secondary battery according to claim 1, wherein
the negative active material has a coating layer and the coating
layer comprises amorphous carbon.
8. The lithium ion secondary battery according to claim 7, wherein
the amorphous carbon is obtained by the carbonization of at least
one material selected from the group consisting of polyvinyl
butyral, bitumen, furfural resin, epoxy resin or phenolic
resin.
9. The lithium ion secondary battery according to claim 7, wherein
the content of the amorphous carbon is 2% to 13%, based on the
total weight of the negative active material.
10. The lithium ion secondary battery according to claim 7, wherein
the content of the amorphous carbon is 5% to 10%, based on the
total weight of the negative active material.
11. The lithium ion secondary battery according to claim 1, wherein
the content of the positive active material is 92% to 98%, based on
the total weight of the positive material layer; and the content of
the negative active material is 92% to 98%, based on the total
weight of the negative material layer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims priority to Chinese
Patent Application No. 201710795465.4 filed on Sep. 6, 2017, which
is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present application relates to the field of batteries,
and more particularly, to a lithium ion secondary battery.
BACKGROUND
[0003] With the growing popularity of electric vehicles, the
requirements of the battery are stricter, such as the battery is
required to be both small and light and must also have high
capacity, long cycle and stable performance. To this end, the
technical persons have made a variety of efforts from the cathode
and anode, electrolytes of battery and so on.
[0004] For example, with respect to positive active material for a
battery, NCM has a higher capacity and density compared to lithium
ion phosphate (LFP). Therefore, a cell using NCM has a higher
energy density. However, unlike LFP that the volume thereof will
shrinkage when it charges, the volume of NCM will expand when it
charges; the expansion force will damage the interface between
anode and cathode, and cause the battery failure. Therefore,
despite the higher energy density, the cycle life of ternary
battery is often worse than that of lithium ion phosphate
battery.
[0005] Therefore, it is still a great challenge to match right
positive active material with right negative active material in
order to improve battery performance.
[0006] In view of this, it is necessary to provide a battery with
good performance.
SUMMARY
[0007] An object of the present application is to provide a lithium
ion secondary battery having comprehensive and balanced
performance.
[0008] A further object of the present application is to provide a
lithium ion secondary battery capable of providing both long cycle
life and high energy density without sacrificing the energy density
of the batteries.
[0009] The inventors have experimented with a large number of
experiments to surprisingly find that a particular type of positive
active material and negative active material for battery can be
combined to improve the cycle life and energy density of the
lithium ion secondary battery at the same time.
[0010] In particular, the present application provides a lithium
ion secondary battery comprising a cathode, an anode, a separator
and an electrolyte; [0011] wherein the cathode comprises a positive
current collector and a positive material layer, wherein the
positive material layer comprises a positive active material with
formula Li.sub.xNi.sub.aCo.sub.bM.sub.cO.sub.2, M is at least one
selected from the group consisting of Mn and Al,
0.95x1.2,0<a<1,0<b<1,0<c<1 and a+b+c=1; [0012]
wherein the anode comprises a negative current collector and a
negative material layer, wherein the negative material layer
comprises graphite having a graphitization degree of 92% to 98% and
an average particle size D50 of 6 .mu.m to 18 .mu.m as negative
active material.
[0013] Compared with the prior art, the lithium ion secondary
battery provided by the present application can have both long
cycle life and high energy density by using a specific positive and
negative active material.
[0014] The present application also relates to a method for
producing the lithium ion secondary battery, comprising: [0015] 1)
preparing a cathode by using a positive active material with
formula Li.sub.xNi.sub.aCo.sub.bM.sub.cO.sub.2, wherein M is at
least one selected from the group consisting of Mn and
Al,0.95x1.2,0<a<1,0<b<1,0<c<1 and a+b+c=1; [0016]
2) preparing an anode by using graphite having a graphitization
degree of 92% to 98% and an average particle size D50 of 6 .mu.m to
18 .mu.m as negative active material; and [0017] 3) assembling the
cathode prepared in step 1) and the anode prepared in step 2) into
a battery.
DETAILED DESCRIPTION
[0018] The present application will be described in further details
with reference to the embodiments and the accompanying drawings in
order to make the objects, the technical solutions and the
advantageous technical effects of the present application clearer.
It is to be understood, however, that the embodiments of the
application are merely for the purpose of explaining the
application and are not intended to be limiting the application,
and that the embodiments of the application are not limited to the
embodiments given in the specification. The experimental conditions
not specified in the examples are given according to conventional
conditions, or according to the conditions recommended by the
material supplier.
[0019] The present application provides a lithium ion secondary
battery comprising a cathode, an anode, a separator and an
electrolyte, [0020] wherein the cathode comprises a positive
current collector and a positive material layer, wherein the
positive material layer comprises a positive active material with
formula Li.sub.xNi.sub.aCo.sub.bM.sub.cO.sub.2, M is at least one
selected from the group consisting of Mn and Al,
0.95x1.2,0<a<1,0<b<1,0<c<1 and a+b+c=1; [0021]
wherein the anode comprises a negative current collector and a
negative material layer, wherein the negative material layer
comprises graphite having a graphitization degree of 92% to 98% and
an average particle size D50 of 6 .mu.m to 18 .mu.m as negative
active material.
[0022] The inventors believe that the graphite having a
graphitization degree of 92% to 98% and an average particle
diameter of D50 of 6 .mu.m to 18 .mu.m can form a high elastic
structure inside the material, and has a higher elasticity than the
conventional graphite material. When charging the positive active
material will expand, and this will result in that the extrusion
force to the anode increases. However, the use of the
above-mentioned high elastic graphite will make the anode has a
strong restoring ability after bearing a large pressure, so that
the contact surface between the anode material remains intact, to
avoid material interface damage and stripping phenomenon caused by
the expansion, which will improve the battery cycle performance
without loss of energy density. However, the above explanation is
provided for the purpose of facilitating to understand the
principles of the present application by those skilled in the art
and is not to be construed as limiting the application. The present
application does not preclude the possibility that other principles
may be made with the development of technology.
[0023] The inventors have further found that the higher the
graphitization degree of the graphite is, the higher the battery
capacity will be, but a too high graphitization degree will lead to
the narrowing of the interlayer distance of the graphite, and the
volume change caused by the lithium ion deintercalation during
charging and discharging will be great, which will impact the
stability of SEI layer. If the graphitization degree is too low,
the crystallinity of graphite is low, and lattice defects will be
more, thus in the process of cycling side effects are prone to
occur and it will lead to capacity attenuation. Through a large
number of experiments, the inventors found that the graphitization
degree from 92% to 98% is just right, preferably from 92% to
96%.
[0024] The inventors have further found that when the D50 of the
graphite is more than 18 .mu.m, it will cause the number of the
stacking layers of the particles less, and it is difficult to form
an elastic structure. When the D50 is less than 6 .mu.m, the
bonding force between materials is too weak, thus the adhesion to
the electrode plate will be poor, during the cycle stripping
phenomenon is prone to occur and it will lead to capacity
attenuation. Therefore, the graphite should have an average
particle size D50 of 6 .mu.m to 18 .mu.m, preferably 6 .mu.m to 12
.mu.m.
[0025] In order to further improve rate performance, the surface of
the graphite may also have a coating layer. The coating layer is
usually an amorphous carbon, for example, at least one selected
from the group consisting of carbon black, coke, soft carbon and
hard carbon. The content of the amorphous carbon relative to the
total weight of the electrode material is generally from 2% to 13%,
preferably from 5 to 10%. In some embodiments, the amorphous carbon
is obtained by (high temperature) carbonization of at least one
material selected from the group consisting of polyvinyl butyral,
bitumen, furfural resin, epoxy resin or phenolic resin.
[0026] The lithium ion secondary battery which comprises specific
positive material and specific negative material above-mentioned
can be prepared by a method known in the field, such as
following:
[0027] 1. Preparation of cathode
[0028] In general, the positive active material, the conductor, the
binder are mixed in a certain weight ratio, then the solvent is
added and the mixture is stirred under the action of a vacuum
stirrer into a uniform transparent state to obtain a positive
material slurry; coat the positive current collector with the
positive material slurry; then dry it and slit to obtain a
cathode.
[0029] The positive active material used in the present application
is Li.sub.xNi.sub.aCo.sub.bM.sub.cO.sub.2, wherein M is at least
one selected from the group consisting of Mn and Al, 0.95x1.2,
0<a<1,0<b<1,0<c<1 and a+b+c=1. When M is Mn, the
formula of the material is abbreviated as NCM; when M is Al, the
formula of the material is abbreviated as NCA. The materials can be
purchased from suppliers.
[0030] Specifically, the positive active material may be at least
one selected from the group consisting of
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2,
LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2,
LiNi.sub.0.5Co.sub.0.25Mn.sub.0.25O.sub.2,
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2,
LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2,
LiNi.sub.0.85Co.sub.0.1Mn.sub.0.05O.sub.2 and
LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2.
[0031] In a preferred embodiment of the present application, the
content of the positive active material is 92% to 98% by weight
based on the total weight of the positive material layer.
[0032] In some embodiments of the present application, the positive
active material may also be doped with at least one element
selected from the group consisting of Al, Zr, Ti, B, Mg, V, Cr, F,
in order to further improve the battery performance.
[0033] In some embodiments of the present application, forming a
coating layer on the outside of the crystal of the positive active
material may further improve the battery performance, and the
coating layer may contain for example at least one of Al, Zr, Ti
and B elements.
[0034] 2. Preparation of anode
[0035] 1) preparing the negative material
[0036] In the present application, a graphite having a
graphitization degree of 92% to 98% and an average particle size
D50 of 6 .mu.m to 18 .mu.m is used as the negative active material.
In the present application, the "graphite" has the meaning which is
well understood by those skilled in the art, and is a carbon
material suitable as the battery negative material which mainly has
the form of a graphite sheet in the interior. The graphite may be
natural graphite, artificial graphite, or a mixture thereof. The
graphite used in the present application having a graphitization
degree of 92% to 98% and an average particle size D50 of 6 .mu.m to
18 .mu.m can be prepared, for example, by the following method:
[0037] (A) crushing the calcined petroleum needle-coke or calcined
coal needle-coke to obtain the raw materials having an average
particle size of 5-20 .mu.m; [0038] (B) subjecting the raw material
obtained in step (A) to a shaping treatment and then subjecting to
a classification treatment to adjust the particle size distribution
of the raw material (preferably, large particles having a particle
size larger than D90 and small particles having a particle size
smaller than D10 are removed); [0039] (C) sieving the raw material
obtained in step (B) and then subjecting it to high-temperature
graphitization, for example, in an Acheson graphitizing furnace at
a temperature of, for example, 2800.degree. C. to 3250.degree. C.
(preferably 2850.degree. C. to 3200.degree. C.); [0040] (D) sieving
and demagnetizing the material obtained in step (C), to obtain the
desired negative material.
[0041] The shaping treatment in step (B) is a conventional
treatment method in the preparation process of artificial graphite,
which is well known to those skilled in the art and can be carried
out by using any shaping machine or other shaping device commonly
used in the art. The classification treatment in step (B) can be
carried out by using a classification screen (sieving method), a
gravity classifier, a centrifugal separator or the like.
Optionally, after step (C) the coating carbonization step may be
carried out prior to step (D), i.e. the product obtained in step
(C) is mixed with at least one material selected from the group
consisting of polyvinyl butyral, bitumen, furfural resin, epoxy
resin or phenolic resin and subjected to high-temperature
carbonization treatment. The temperature of the carbonization
treatment is, for example, 900-1500.degree. C., for example
1000-1400.degree. C. or 1100-1300.degree. C.
[0042] Alternatively, the present application may also use a
natural graphite or commercially available graphite having a
graphitization degree of 92% to 98% and an average particle size
D50 of 6 .mu.m to 18 .mu.m.
[0043] The graphitization degree of the graphite can be determined
by methods known in the field, for example by X-ray diffractometer
(reference, for example, Qian Chongliang et al., "Graphitization
Measurement of Carbon Material by X-ray Diffraction", Journal of
Central South University of Technology, Vol. 32, No. 3, Jun.
2001).
[0044] The average particle size D50 of the graphite can be
conveniently determined by using a laser particle size analyzer
(e.g., Malvern Master Size 2000).
[0045] 2) Assembly of the anode
[0046] In general, the negative active material, the thickener, the
binder are mixed at a certain weight ratio; then the solvent is
added to obtain the negative electrode slurry; then coat the
negative current collector with the negative electrode slurry; then
dry it and slit to obtain an anode.
[0047] In a preferred embodiment of the present application, the
content of the negative active material is 92% to 98% by weight
based on the total weight of the negative material layer.
[0048] 3. Preparation of electrolyte
[0049] As a non-aqueous electrolyte, a lithium salt solution
dissolved in an organic solvent is usually used. Lithium salts are,
for example, inorganic lithium salts such as LiClO.sub.4,
LiPF.sub.6, LiBF.sub.4, LiAsb.sub.6, LiSbF.sub.6; or organic
lithium salts such as LiCF.sub.3SO.sub.3, LiCF.sub.3CO.sub.2,
Li.sub.2C.sub.2F.sub.4(SO.sub.3).sub.2,
LiN(CF.sub.3SO.sub.2).sub.2, LiC(CF.sub.3SO.sub.2).sub.3,
LiC.sub.nF.sub.2n+1SO.sub.3(n2). The organic solvent used in the
non-aqueous electrolyte is, for example, a cyclic carbonate such as
ethylene carbonate, propylene carbonate, butylene carbonate and
vinylene carbonate; or a chain carbonate such as dimethyl
carbonate, diethyl carbonate and methyl ethyl carbonate; or a
cyclic ester such as methyl propionate; or a chain ester such as
.gamma.-butyrolactone; or a chain ether such as dimethoxyethane,
diethyl ether, diethylene glycol dimethyl ether and triethylene
glycol dimethyl ether; or a cyclic ether such as tetrahydrofuran
and 2-methyltetrahydrofuran; or nitriles such as acetonitrile and
propionitrile; or a mixture of these solvents.
[0050] For example, ethylene carbonate (EC), methyl ethyl carbonate
(EMC) and diethyl carbonate (DEC) were mixed according to a certain
volume ratio, and then the sufficiently dried lithium salt
LiPF.sub.6 was dissolved in a mixed organic solvent to prepare an
electrolyte.
[0051] 4. Separator
[0052] There is no special requirement for the separator. In
particularly, the separator may be selected from a polyethylene
film, a polypropylene film, a polyvinylidene fluoride film, and a
multilayer composite film thereof, depending on the actual
requirements.
[0053] 5. Preparation of battery
[0054] Put the separator between the cathode and anode, then
winding, jelly roll insertion, electrolyte injection and so on to
obtain the lithium ion battery.
[0055] The advantageous effects of the present application will be
further described below with reference to the following
examples.
[0056] 1. Material preparation and battery assembly
[0057] (1) The preparation of a cathode:
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2, SuperP (conductive agent), PVDF
(binder) were mixed at a mass ratio of 97:1:2, then a solvent was
added. The mixture was stirred in a vacuum mixer into a uniform and
transparent system, to obtain the positive electrode slurry. The
positive electrode slurry was uniformly coated on the positive
current collector aluminum foil; then the aluminum foil was dried
at room temperature and then transferred to the oven for drying,
and then the cathode was obtained by cold pressing and cutting.
[0058] (2) The preparation of an anode: artificial graphite anode
active material samples were taken, and the particle size of the
sample was measured by using Malvern Master Size 2000 laser
particle size analyze, and the graphitization degree of the sample
was measured by using X-ray diffractometer. The test results can be
found from Table 1. The artificial graphite negative active
material, sodium carboxymethyl cellulose (thickener) and SBR
(styrene-butadiene rubber binder) were mixed at a mass ratio of
97:1.2:1.8, and deionized water was added, then under the action of
a vacuum stirrer a negative electrode slurry was obtained. The
negative electrode slurry was uniformly coated on the negative
current collector copper foil; the copper foil was dried at room
temperature and then transferred to the oven for drying, and then
the anode was obtained by cold pressing and cutting.
[0059] (3) The preparation of an electrolyte: Ethylene carbonate
(EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) were
mixed at a volume ratio of 3:6:1, followed by dissolving the fully
dried lithium salt LiPF.sub.6 into a mixed organic solvent at a
concentration of 1 mol/L to prepare an electrolyte.
[0060] (4) Separator: 12 micron PP/PE composite isolation film was
used.
[0061] (5) The preparation of the full battery: the cathode, the
separator, the anode were stacked in order, so that the separator
was segregated between the cathode and anode, and then the stack
was wound to obtain a bare cell; the bare cells were placed in the
outer packaging shell. The prepared electrolyte was poured into
dried bare cells, and the lithium ion battery was obtained by
vacuum packaging, standing, chemical treatment, shaping and the
like.
[0062] 2. The cycle performance:
[0063] At 25.degree. C., the battery was firstly charged and
discharged as follows: constant current charging and constant
voltage charging with a constant current of 1C until the voltage
upper limit of 4.2V, then constant current discharging with a
constant current of 1 C until the final voltage of 2.8V, recording
the discharge capacity of the first cycle. Charging/discharging
cycles were done in such way.
Cycle capacity retention rate=(discharge capacity of the
n.sup.thcycle/discharge capacity at the first cycle)x100
[0064] Examples 2-12
[0065] Example 1 was repeated using different positive active
materials and negative active materials. The parameters of the
materials and the battery performance data were summarized in Table
1.
[0066] Comparative Examples 1-4
[0067] Example 1 was repeated using different positive active
materials and negative active materials. The parameters of the
materials and the battery performance data were summarized in Table
1.
TABLE-US-00001 TABLE 1 Average particle size Cycle Cycle
Graphitization of the Dopant Coating capacity life degree of
negative of the of the retention (attenuation Comparative negative
material positive positive rate of to example/Example electrode
(.mu.m) Positive material material material 500.sup.th cycle 80%)
Example 1 94% 6 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 No No
95.70% 2543 Example 2 94% 8 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2
No No 95.50% 2422 Example 3 94% 12
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 No No 95.10% 2193 Example 4
94% 18 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 No No 94.50% 1998
Example 5 92% 8 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 No No
95.80% 2594 Example 6 96% 8 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2
No No 95.20% 2234 Example 7 98% 8
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 No No 94.10% 1832 Example 8
94% 8 LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 No No 95.80% 2591
Example 9 94% 8 LiNi.sub.0.5Co.sub.0.25Mn.sub.0.25O.sub.2 No No
95.65% 2605 Example 10 94% 8
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 No No 96.40% 3052
Example 11 94% 8 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 B No
95.70% 2556 Example 12 94% 8
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 B Al 96.10% 2843
Comparative example 1 94% 4 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2
No No 92.10% 1105 Comparative example 2 94% 20
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 No No 89.10% 712
Comparative example 3 88% 8 LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2
No No 88.90% 1030 Comparative example 4 99% 18
LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O2 No No 88.30% 604
[0068] Test result analysis:
[0069] 1. As can be seen from the analysis of Examples 1-4 and
Comparative Examples 1-2:
[0070] When the D50 of the negative material was not within the
scope of the present application, the battery cycle performance was
remarkably reduced. In Examples 1-4, it was found that when the
graphitization degree was constant, the battery cycle performance
was gradually decreased with the increase of the average particle
size of the material, preferably in the range of 6-12 .mu.m.
[0071] 2. As can be seen from the analysis of Examples 2, 5-7 and
Comparative Examples 3-4:
[0072] When the graphitization degree of the negative material was
not within the scope of the present application, the battery cycle
performance was remarkably deteriorated. In Examples 2 and 5-7, it
can be seen that when the average particle size of the material was
constant, the battery cycle performance was gradually decreased
with the increase of graphitization degree, preferably in the range
of 92% to 96%.
[0073] 3. As can be seen from the analysis of Examples 2 and
11-12,
[0074] When the positive material was doped and/or coated, the
cycle performance of the battery can be further improved.
[0075] It will be apparent to those skilled in the art that the
present application may be modified and varied in accordance with
the above teachings. Accordingly, the present application is not
limited to the specific embodiments disclosed and described above,
and modifications and variations of the present application are
intended to be included within the scope of the claims of the
present application. In addition, although some specific
terminology is used in this specification, these terms are for
convenience of illustration only and are not intended to limit the
present application in any way.
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