CN111533120A - Negative electrode active material and lithium ion battery with improved high-voltage quick-charging cycle performance - Google Patents

Negative electrode active material and lithium ion battery with improved high-voltage quick-charging cycle performance Download PDF

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CN111533120A
CN111533120A CN202010383942.8A CN202010383942A CN111533120A CN 111533120 A CN111533120 A CN 111533120A CN 202010383942 A CN202010383942 A CN 202010383942A CN 111533120 A CN111533120 A CN 111533120A
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negative electrode
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贺伟
彭冲
施超
张保海
李俊义
徐延铭
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Zhuhai Cosmx Battery Co Ltd
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    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a negative active material and a lithium ion battery with improved high-voltage quick-charging cycle performance, wherein the negative active material comprises the following components: (a) 50-90 wt% of negative electrode graphite; (b) small particle size graphite; 10-50 wt%; the particle size distribution of the negative electrode graphite is as follows: d10＝8‑12μm，D50＝14‑18μm，D9025-30 μm; the particle size distribution of the small-particle-size graphite is as follows: d10＝3‑5μm，D50＝7‑9μm，D9015-20 μm; the negative electrode graphite is uncoated graphite, and the small-particle-size graphite is coated graphite. The negative electrode canThe use of the material can improve the rate capability of the high-voltage system lithium ion battery; the quick charge cycle life and the stability of the high-voltage system lithium ion battery at normal temperature can be improved; the quick charge cycle life and the stability of the high-voltage system lithium ion battery at high temperature can be improved; and the cycle performance requirement and other performance requirements of the lithium ion battery are realized by adjusting the mixing proportion (10-50 wt%) of the small-particle-size graphite.

Description

Negative electrode active material and lithium ion battery with improved high-voltage quick-charging cycle performance
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a negative electrode active material and a lithium ion battery comprising the same and having improved high-voltage quick-charging cycle performance.
Background
At present, researchers gradually increase the research investment on lithium ion batteries, and in order to realize higher energy density of lithium ion batteries, the research on the voltage system of the anode of the lithium ion battery gradually changes from 4.35V to higher voltage systems such as 4.4V and 4.45V. Meanwhile, with the popularization of 4G and 5G mobile phones, the mobile phone market puts higher and higher requirements on the quick charging capability of the mobile phone battery. Meanwhile, the requirement of the mobile phone battery on the cycle life is continuously improved, and the requirement of the mobile phone battery on the cycle life is gradually improved to a higher multiplying power and a longer cycle life (such as 1.0C/0.7C, 2C/0.7C charge-discharge cycle for 800 times or even higher multiplying power) from the previous requirement of meeting the 0.5C/0.5C charge-discharge cycle for 500 times. Compared with the low voltage, the fast charge cycle performance of the lithium ion battery under the high voltage system is greatly influenced, the cycle performance is extremely unstable, and the cycle life is difficult to ensure. These have all led to severe limitations in the application of high voltage, fast charging lithium ion batteries.
Along with the promotion of lithium ion battery energy density to and the continuous improvement of the anodal voltage system of lithium ion battery, the quick charge performance of cell-phone battery becomes more and more important moreover, and when the charge rate of battery accelerates, the polarization increase of battery inside, the destruction aggravation to anodal material leads to high voltage lithium ion battery to appear the normal atmospheric temperature circulation capacity decay easily and accelerates, the cycle life shortens, the problem aggravation etc. problem of cycle expansion, and this kind of phenomenon is further aggravated under high temperature moreover. These all severely limit the application of high voltage, fast-charging lithium ion batteries.
Disclosure of Invention
In order to overcome the defects of the prior art, the present invention aims to improve the fast charge (e.g., 1.5C and above) cycle performance of a high voltage system, that is, to provide a negative electrode active material and a lithium ion battery comprising the negative electrode active material, wherein the negative electrode active material is prepared by blending graphite with small particle size into negative electrode graphite, such that during fast charge (e.g., 1.5C and above) under high voltage, the negative electrode lithium intercalation capability is improved, the internal polarization of the battery is reduced, and the increase of the positive electrode potential is reduced, such that the fast charge cycle performance and cycle stability of the high voltage lithium ion battery are improved, and the prepared negative electrode active material also saves the graphite coating cost because the negative electrode graphite is of an uncoated graphite structure.
The purpose of the invention is realized by the following technical scheme:
an anode active material comprising the following components:
(a) 50-90 wt% of negative electrode graphite; (b) small particle size graphite; 10-50 wt%;
the particle size distribution of the negative electrode graphite is as follows: d10＝6-12μm，D50＝12-18μm，D9022-36 μm; the particle size distribution of the small-particle-size graphite is as follows: d10＝3-5μm，D50＝7-9μm，D90＝15-20μm；
The negative electrode graphite is uncoated graphite, and the small-particle-size graphite is coated graphite.
According to the invention, the small-particle-size graphite is small-particle-size graphite with an amorphous carbon layer coated on the surface.
According to the invention, the amorphous carbon layer has a thickness of 2-20 nm.
According to the invention, the small-particle graphiteD of (A)90And D of negative electrode graphite50The difference of (a) is-3 to 5 μm, for example-3 to 3 μm. For example, -3 μm, -2 μm, -1 μm, 0 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.
According to the present invention, the particle size distribution of the negative electrode graphite: d10＝8-10μm，D50＝12-15μm，D90＝22-25μm。
According to the invention, the particle size distribution of the small particle size graphite is: d10＝4-5μm，D50＝8-9μm，D90＝17-18μm。
According to the invention, the tap density of the small-particle graphite is 1.1-1.3g/cm3。
According to the invention, the limit compacted density of the small-particle graphite<1.65g/cm3。
According to the invention, the specific surface area of the small-particle graphite is 2.1-2.6m2/g。
According to the invention, the small-particle-size graphite is prepared by the following method:
average particle diameter (D)50) Coarse pulverizing and sieving 3-15 μm spheroidized natural graphite or artificial graphite, reshaping, graphitizing, and sieving to obtain average particle diameter (D)50) Graphite particles of 6-10 μm;
uniformly mixing graphite particles with the average particle size of 6-10 mu m and an amorphous carbon precursor, and then carrying out carbonization treatment to obtain small-particle-size graphite with the surface coated with an amorphous carbon layer, wherein the particle size distribution of the small-particle-size graphite is as follows: d10＝3-5μm，D50＝7-9μm，D90＝15-20μm。
The invention also provides a lithium ion battery which comprises a negative pole piece, wherein the negative pole piece comprises the negative active material.
According to the invention, the negative pole piece comprises a negative active material layer, wherein the negative active material layer comprises the following components in percentage by mass:
70-99 wt% of negative electrode active material, 0.5-15 wt% of conductive agent and 0.5-15 wt% of binder.
The invention has the beneficial effects that:
1. the multiplying power performance of the high-voltage system lithium ion battery can be improved;
2. the quick charge cycle life and the stability of the high-voltage system lithium ion battery at normal temperature can be improved; the quick charge cycle life and the stability of the high-voltage system lithium ion battery at high temperature can be improved;
3. by adjusting the mixing proportion (10-50 wt%) of the small-particle-size graphite, the cycle performance requirement and other performance requirements of the lithium ion battery are realized.
4. According to the mode provided by the patent, the cathode pole piece uses a conductive network combined by point lines, and the multiplying power performance of the prepared battery is further improved; meanwhile, the normal-temperature cycle performance of the battery is improved by more than 100T (according to 80% capacity retention rate) compared with the cycle frequency of the conventional scheme.
Drawings
FIG. 1 is a constant current charge ratio of the batteries of examples 1-3 and comparative example 1;
FIG. 2 is an ordinary temperature cycle curve of the batteries of examples 1 to 3 and comparative example 1;
fig. 3 is a high temperature cycling profile for the cells of examples 1-3 and comparative example 1.
Detailed Description
As described above, the present invention provides an anode active material comprising the following components:
(a) 50-90 wt% of negative electrode graphite; (b) small particle size graphite; 10-50 wt%;
the particle size distribution of the negative electrode graphite is as follows: d10＝6-12μm，D50＝12-18μm，D9022-36 μm; the particle size distribution of the small-particle-size graphite is as follows: d10＝3-5μm，D50＝7-9μm，D90＝15-20μm；
The negative electrode graphite is uncoated graphite, and the small-particle-size graphite is coated graphite.
In a preferred embodiment of the present invention, the small-particle-size graphite is a small-particle-size graphite whose surface is coated with an amorphous carbon layer. Specifically, the thickness of the amorphous carbon layer is 2-20 nm.
In a preferred embodiment of the present invention, D of the small-particle-size graphite90And D of negative electrode graphite50The difference of (a) is-3 to 5 μm, for example-3 to 3 μm. For example, -3 μm, -2 μm, -1 μm, 0 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.
In a preferred embodiment of the present invention, the negative electrode graphite has a particle size distribution of: d10＝8-10μm，D50＝12-15μm，D9022-25 μm; illustratively, the particle size distribution of the negative electrode graphite: d10＝8.39μm，D50＝13.9μm，D90＝23.5μm。
In a preferred embodiment of the present invention, the particle size distribution of the small particle size graphite is: d10＝4-5μm，D50＝8-9μm，D9017-18 μm. Illustratively, the particle size distribution of the small particle size graphite: d10＝4.77μm，D50＝8.95μm，D90＝17.5μm。
In a preferred embodiment of the present invention, the content of the small-particle graphite is 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%; the mass percentage of the negative electrode graphite is 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt% and 90 wt%.
In a preferred embodiment of the present invention, the tap density of the small-particle graphite is 1.1 to 1.3g/cm3For example, 1.18g/cm3。
In a preferred embodiment of the present invention, the specific surface area of the graphite having a small particle diameter is 2.1 to 2.6m2A/g, of, for example, 2.36m2/g。
In a preferred embodiment of the present invention, the minimum compacted density of the small-particle-size graphite<1.65g/cm3E.g. 1.55g/cm3。
In a preferred embodiment of the present invention, the small particle size graphite may be derived from a graphitized material, which may be, for example, one or more of artificial graphite and natural graphite.
In a preferred embodiment of the present invention, the small-particle graphite can be prepared by the following method:
average particle diameter (D)50) Coarse pulverizing and sieving 3-15 μm spheroidized natural graphite or artificial graphite, reshaping, graphitizing, and sieving to obtain average particle diameter (D)50) Graphite particles of 6-10 μm;
uniformly mixing graphite particles with the average particle size of 6-10 mu m and an amorphous carbon precursor, and then carrying out carbonization treatment to obtain small-particle-size graphite with the surface coated with an amorphous carbon layer, wherein the particle size distribution of the small-particle-size graphite is as follows: d10＝3-5μm，D50＝7-9μm，D90＝15-20μm。
Wherein, the amorphous carbon precursor can be selected from pitch or resin materials, such as phenolic resin and the like.
Wherein the mass ratio of the graphite particles with the average particle size of 6-10 mu m to the amorphous carbon precursor is 20:1-10: 1.
Wherein the thickness of the coated amorphous carbon layer is 2-20 nm.
Wherein the coarse sieving and shaping process is a method known in the art.
Wherein the temperature of the graphitization treatment is more than or equal to 2500 ℃ (such as 2500 ℃ and 3200 ℃), and the time of the graphitization treatment is more than or equal to 8 hours (such as 8-24 hours).
Wherein the temperature of the carbonization treatment is 1000-1600 ℃, and the time of the carbonization treatment is more than or equal to 5 hours (such as 5-10 hours).
In a preferred embodiment of the present invention, the negative electrode graphite is selected from untreated graphite for a negative electrode active material of a lithium ion battery, such as natural graphite, artificial graphite, and the like. Such negative electrode graphite has a general lithium ion deintercalation capability, which does not allow for large rate charging. The non-treatment includes non-coating treatment and the like.
In the present invention, the uncoated graphite means graphite whose graphite surface is not subjected to any coating treatment.
In a preferred embodiment of the present invention, the negative electrode graphite may be prepared by:
for average particle diameter (D)50) Performing magnetic separation on 5-30 mu m spheroidized natural graphite or artificial graphite, performing coarse crushing and sieving for the first time, and performing graphitization treatment to obtain graphite particles;
crushing graphite particles, and then carrying out secondary screening to prepare the negative electrode graphite, wherein the particle size distribution of the negative electrode graphite is as follows: d10＝6-12μm，D50＝12-18μm，D90＝22-36μm。
Wherein the coarse sieving and shaping process is a method known in the art.
Wherein the temperature of the graphitization treatment is more than or equal to 2500 ℃ (such as 2500 ℃ and 3200 ℃), and the time of the graphitization treatment is more than or equal to 8 hours (such as 8-24 hours).
The invention also provides a preparation method of the anode active material, which comprises the following steps:
and mixing the negative electrode graphite and the small-particle-size graphite to prepare the negative electrode active material.
The invention also provides a lithium ion battery, which comprises a negative pole piece, wherein the negative pole piece comprises a negative active material layer, and the negative active material layer comprises the negative active material, a conductive agent and a binder.
In a preferred embodiment of the present invention, the negative electrode active material layer comprises the following components in percentage by mass:
70-99 wt% of negative electrode active material, 0.5-15 wt% of conductive agent and 0.5-15 wt% of binder.
Preferably, the negative electrode active material layer comprises the following components in percentage by mass:
80-98 wt% of negative electrode active material, 1-10 wt% of conductive agent and 1-10 wt% of binder.
Still preferably, the negative electrode active material layer contains the following components in percentage by mass:
90-98 wt% of negative electrode active material, 1-5 wt% of conductive agent and 1-5 wt% of binder.
In a preferred embodiment of the present invention, the conductive agent is at least one selected from the group consisting of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber.
In a preferred embodiment of the present invention, the binder is at least one selected from the group consisting of sodium carboxymethylcellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
In a preferred embodiment of the present invention, the negative electrode tab includes a current collector and a negative active material layer coated on one or both surfaces of the current collector.
In a preferred scheme of the invention, because the particle size distribution of the negative electrode graphite and the small-particle-size graphite is different, the small-particle-size graphite can be filled in the gap inside the negative electrode graphite, so that the compacted density of the negative electrode active material is not influenced, namely the energy density of the lithium ion battery is not influenced, and the conductive capacity of the negative electrode active material is improved; meanwhile, the small-particle-size graphite has stronger capability of releasing and inserting lithium ions, and can realize the stability of the quick charge cycle performance of the lithium ion battery. Further, the negative electrode active material system of the negative electrode graphite mixed with the small-particle-size graphite is mainly used for conducting electricity by building a point-line combined conducting network mode, so that an electronic channel between the small-particle-size graphite and the negative electrode graphite can be further optimized, an important role is played in the later stage of the rapid charging cycle, particularly the improvement of the stability of the lithium ion battery after 500 cycles, and the negative electrode active material can remarkably improve the rapid charging performance and the accelerated capacity attenuation of the high-voltage lithium ion battery in the later stage of the cycle, particularly after 500 cycles.
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Preparation example 1
Average particle diameter (D)50) Coarse crushing, sieving and reshaping the natural graphite with sphericizing diameter of 3-15 μm, heating to 2600 deg.C, graphitizing the reshaped natural graphite at the temperature for 10 hr, and re-sieving the graphitized graphite particles to obtain average particle diameter (D)50) Graphite particles of 8-10 μm.
1000g of the above-mentioned graphitized average particle diameter (D)50) Graphite particles of 8-10 μm are uniformly mixed with 50g of amorphous carbon precursor (phenolic resin), and carbonization treatment is carried out for 6 hours at 1000 ℃ to finally obtain the product with the particle size distribution of D10＝4.77μm，D50＝8.95μm，D9017.5 μm of graphite with small particle size coated with amorphous carbon.
The tap density of the prepared small-particle-size graphite is 1.12g/cm3Specific surface area of 2.16m2(iv)/g, ultimate compacted density of 1.65g/cm3。
Preparation example 2
Average particle diameter (D)50) Performing primary magnetic separation on 5-30 mu m spheroidized natural graphite, performing primary coarse crushing and screening, heating to 2600 ℃, performing graphitization treatment for 10 hours at the temperature, crushing graphite particles, and performing secondary screening to obtain the product with the particle size distribution of D10＝8.39μm，D50＝13.9μm，D9023.5 μm negative electrode graphite.
The tap density of the prepared negative electrode graphite is 1.08g/cm3Specific surface area of 1.15m2(iv)/g, ultimate compacted density of 1.73g/cm3。
Examples 1 to 3 and comparative example 1
1. Preparation of cathode slurry
Weighing x wt% of the prepared negative electrode graphite and y wt% of the prepared small-particle-size graphite according to the material ratio shown in table 1:
TABLE 1 Material proportioning for examples 1-2 and comparative example 1
x wt% negative electrode graphite y wt% of small particle size graphite Conductive agent
Comparative example 1 96 0 1.5 wt% of carbon black conductive agent
Example 1 82 14 1.5 wt% of carbon black conductive agent
Example 2 64 32 1.5 wt% of carbon black conductive agent
Example 3 64 32 1.3 wt% of carbon black conductive agent and 0.2 wt% of carbon nano tube
And mixing the negative electrode graphite and the small-particle-size graphite to obtain the negative electrode active material. Adding the negative electrode active material (the total amount is 96 wt%), the conductive agent (the total amount is 1.5 wt%), the SBR binder (the total amount is 1.3 wt%), the carboxymethyl cellulose sodium CMC (the total amount is 1.2 wt%) and deionized water into a homogenizer according to the steps, mixing and stirring to obtain uniformly dispersed negative electrode slurry, wherein the solid content is 43-48 wt%; for example, the mixing method described in (i) or (ii) below is used for mixing:
adding small-particle-size graphite into a mixed system of conductive carbon black and negative electrode graphite, mixing and stirring, then adding part of deionized water and sodium carboxymethyl cellulose, stirring to obtain a stone-paste-shaped negative electrode graphite dough, continuously adding the rest of deionized water and sodium carboxymethyl cellulose, and finally adding an SBR binder, and stirring to obtain uniformly dispersed negative electrode slurry.
Adding small-particle-size graphite into a mixed system of conductive carbon black and negative electrode graphite, mixing and stirring, then adding part of deionized water and sodium carboxymethyl cellulose, stirring for a period of time to obtain a stone-paste-shaped negative electrode graphite dough, then adding the prepared and dispersed carbon nanotube slurry, stirring for an additional period of time, continuously adding the rest of deionized water and sodium carboxymethyl cellulose, and finally adding the SBR binder, and stirring to obtain the uniformly dispersed negative electrode slurry.
2. Preparation of positive electrode slurry
Taking a 4.45V system lithium cobaltate positive electrode active material, adding conductive carbon black and carbon nano tubes serving as a conductive agent, polyvinylidene fluoride serving as a binder and N-methyl pyrolidone serving as a solvent into a homogenizer, and stirring and mixing to obtain uniformly dispersed positive electrode slurry;
3. preparing the finished battery
The anode and cathode active material is prepared by the steps of coating, rolling and slitting, flaking, winding, packaging and baking, injecting liquid, forming and the like.
4. Performance testing
(1) The prepared battery is subjected to rate charge tests of 0.2C, 0.5C, 1C, 1.5C and 2C at the temperature of 25 ℃.
(2) The prepared battery is subjected to a charge-discharge cycle test of 2C/0.7C at the temperature of 25 ℃, and the prepared battery is subjected to a charge-discharge cycle test of 2C/0.7C at the temperature of 45 ℃.
The test results are shown in fig. 1-3.
The minimum volumetric energy densities of the cells obtained in comparative example 1 and examples 1 to 3 were found to be 660Wh/L, 658Wh/L, 661Wh/L, respectively, indicating that the volumetric energy density of the next cell was not significantly affected when the blending ratio of the small-particle-size graphite was within 15 wt%.
The energy density of the lower battery cell in example 2 is lower than that in example 1, which shows that the energy density of the lower battery cell is slightly influenced but not greatly influenced when the small-particle-size graphite is blended to reach 33 wt%; the energy density of example 3 was almost the same as that of example 1, indicating that the energy density was not affected by mixing carbon nanotubes in the conductive agent.
As can be seen from fig. 1, when the cells obtained in comparative example 1 and examples 1 to 3 were subjected to 3C rate charging, the ratio of the charging capacity in the constant current stage to the total charging capacity was: 42.71%, 44.24%, 46.51%, 47.53%.
Fig. 2 is a comparison of capacity retention rates of the batteries obtained in comparative example 1 and examples 1-3 at 25 ℃ and 2C charge/0.7C discharge cycles at room temperature, and it can be seen from fig. 2 that the battery obtained in comparative example 1 has a poor trend of cycling at room temperature, the capacity retention rates of the batteries obtained in comparative example 1 and examples 1-3 at 500 cycles (80% according to the capacity retention rate) according to the 2C/0.7C cycling schedule are 80%, 87.8%, 88.2% and 88.6% respectively. The capacity retention rates of the batteries prepared in examples 1 to 3 at 2C/0.7C cycle at 800 cycles at room temperature were 79%, 81.9% and 83.1%, respectively.
FIG. 3 is a comparison of the retention rates of comparative example 1 and examples 1-3 at 45 ℃ and 2C charge/0.7C discharge cycles, and it can be seen from FIG. 3 that the comparative example can only support 430 cycles of 2C/0.7C cycles (according to 80% capacity retention rate) at 45 ℃, while the capacity retention rates of the batteries prepared in examples 1-3 at 500 cycles of 2C/0.7C cycles at room temperature are 85.0%, 87.10% and 89.2%, respectively. The cycle lives of comparative example 1 and examples 1 to 3 were 430T, 570T, 660T, 770T, respectively, in terms of 80% capacity retention.
As can be seen from the results of figures 1, 2 and 3,
energy density: example 1 ≈ example 3 ≈ comparative > example 2; the energy density of the battery is slightly reduced when the blending proportion of the small-particle-size graphite is increased, the energy density is not influenced when the blending proportion of the small-particle-size graphite is 15%, and the energy density is reduced by 2Wh/L when the blending proportion of the small-particle-size graphite is increased to 33%; ② example 3 uses the conductive carbon black + carbon nanotube mixture, its energy density after blending is not affected.
Cycle performance: example 3> example 2> example 1> comparative example, illustrating: the blending proportion of the small-particle-size graphite is improved, and the quick charge and normal-temperature and high-temperature cycle performance of the lithium ion battery are improved to a certain extent; secondly, the negative electrode uses a mixed conductive agent of conductive carbon black and carbon nanotubes, the cycle life at normal temperature and high temperature is prolonged, and the negative electrode is matched with a conductive network combined by a point line, so that the blending test effect of the small-particle-size graphite is better.
Particularly, after a proper amount of small-particle-size graphite is blended, the small-particle-size graphite can be filled in large gaps in the negative electrode graphite, the compacted density of the negative electrode active material is not influenced, and the high energy density of the battery is ensured; because the lithium-intercalation ability of the small-particle-size graphite is stronger, and the small-particle-size graphite is filled in the gap of the negative electrode graphite, the conductive ability of the negative electrode active material can be improved, and the rapid charging is facilitated.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. An anode active material, wherein the anode active material comprises the following components:
(a) 50-90 wt% of negative electrode graphite; (b) small particle size graphite; 10-50 wt%;
the particle size distribution of the negative electrode graphite is as follows: d10＝6-12μm，D50＝12-18μm，D9022-36 μm; the particle size distribution of the small-particle-size graphite is as follows: d10＝3-5μm，D50＝7-9μm，D90＝15-20μm；
The negative electrode graphite is uncoated graphite, and the small-particle-size graphite is coated graphite.
2. The negative electrode active material according to claim 1, wherein D of the small-particle-diameter graphite90And D of negative electrode graphite50The difference of (a) is-3 to 5 μm.
3. The anode active material according to claim 1 or 2, wherein a particle size distribution of the anode graphite is: d10＝8-10μm，D50＝12-15μm，D90＝22-25μm。
4. The negative electrode active material according to any one of claims 1 to 3, wherein the small-particle graphite has a particle size distribution of: d10＝4-5μm，D50＝8-9μm，D90＝17-18μm。
5. The negative electrode active material according to any one of claims 1 to 4, wherein the tap density of the small-particle-diameter graphite is 1.1 to 1.3g/cm3(ii) a Ultimate compacted density of the small particle size graphite<1.65g/cm3。
6. The negative electrode active material according to any one of claims 1 to 5, wherein the small-particle graphite has a specific surface area of 2.1 to 2.6m2/g。
7. The negative electrode active material according to any one of claims 1 to 6, wherein the coated graphite is graphite having a surface coated with an amorphous carbon layer, and the thickness of the amorphous carbon layer is 2 to 20 nm.
8. The negative electrode active material according to any one of claims 1 to 7, wherein the small-particle graphite is prepared by:
average particle diameter (D)50) Coarse pulverizing and sieving 3-15 μm spheroidized natural graphite or artificial graphite, reshaping, graphitizing, and sieving to obtain average particle diameter (D)50) Graphite particles of 6-10 μm;
uniformly mixing graphite particles with the average particle size of 6-10 mu m and an amorphous carbon precursor, and then carrying out carbonization treatment to obtain small-particle-size graphite with the surface coated with amorphous carbon, wherein the particle size distribution of the small-particle-size graphite is as follows: d10＝3-5μm，D50＝7-9μm，D90＝15-20μm。
9. A lithium ion battery comprising a negative electrode tab comprising the negative active material of any one of claims 1-8.
10. The lithium ion battery of claim 9, wherein the negative electrode sheet comprises a negative electrode active material layer, wherein the negative electrode active material layer comprises the following components in percentage by mass:
70-99 wt% of the negative active material, 0.5-15 wt% of a conductive agent, and 0.5-15 wt% of a binder.
CN202010383942.8A 2020-05-08 2020-05-08 Negative electrode active material and lithium ion battery with improved high-voltage quick-charging cycle performance Pending CN111533120A (en)

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