A negative electrode graphite material, graphite negative electrode and production method thereof

Abstract

The present application relates to the technical field of electrode materials, and specifically to a negative electrode graphite material, a graphite negative electrode and a production method thereof. The negative electrode graphite material comprises core-shell particles in which a shell layer covers a core layer. The shell layer is carbonized maleic anhydride grafted polyethylene. The core layer is graphite particles. Maleic anhydride grafted polyethylene has a rich branched structure, which can form a conductive carbon chain with a rich structure after carbonization, and increase the number of micropores inside the negative electrode, thereby increasing the capacity of the negative electrode to store lithium ions. In both aqueous and organic electrolytes, the negative electrode graphite material has good electrical conductivity, large capacity and good cycle performance, and good compatibility with a variety of electrolytes. The present application improves the compatibility of the graphite material with the electrolyte by surface modification of natural graphite, improves the electrochemical performance of the graphite negative electrode, and is suitable for use in high energy density lithium-ion batteries.

Description

Technical Field

[0001] The present application relates to the technical field of electrode materials, and more specifically, to a negative electrode graphite material, a graphite negative electrode and a production method thereof. Background Art

[0002] Lithium-ion batteries are widely used in electronics, automotive, energy storage, and other fields due to their high energy density, long cycle life, and high safety factor. With the continuous development of battery technology, various sub-sectors have increasingly demanding requirements for refined battery applications, especially in key indicators such as cycle life, rate capability, and capacity.

[0003] Today's lithium-ion battery structures are becoming increasingly compact, leaving less and less room for maneuver. Limited by the variety of existing battery materials, electrolytes containing different additives are now available on the market to suit different application scenarios. This means that electrode materials must also have better compatibility with the electrolyte to improve battery performance. Negative electrode artificial graphite materials have a market share of over 80%, and their electrolyte compatibility requirements are even more stringent. Conventional negative electrode graphite materials have low electrolyte compatibility, which significantly affects the battery's electrical performance and cannot meet the current growing demand. Summary of the Invention

[0004] In view of the low compatibility of general negative electrode graphite materials with electrolytes, which greatly affects the electrical performance of the battery and cannot meet the current growing demand for use, this application proposes a negative electrode graphite material with good electrolyte compatibility, a graphite negative electrode and its production method.

[0005] In the first aspect, the present application proposes a negative electrode graphite material and adopts the following technical solution.

[0006] A negative electrode graphite material comprises core-shell particles in which a shell layer covers a core layer; the shell layer is carbonized maleic anhydride grafted polyethylene; and the core layer is graphite particles.

[0007] By employing this technical solution, maleic anhydride-grafted polyethylene possesses a rich branched structure. Upon carbonization, this structure forms conductive carbon chains with a rich structure. This increases the number of micropores within the negative electrode, thereby enhancing the negative electrode's lithium ion storage capacity. This negative electrode graphite material exhibits excellent conductivity, high capacity, and good cycling performance in both aqueous and organic electrolytes, and is highly compatible with a variety of electrolytes.

[0008] As an improvement of the negative electrode graphite material, the mass ratio of uncarbonized maleic anhydride grafted polyethylene and graphite particles used to prepare the negative electrode graphite material is (2-10):100.

[0009] By adopting the above technical solution, the negative electrode graphite material prepared by the ratio of maleic anhydride grafted polyethylene and graphite particles has abundant lithium storage space and high structural strength.

[0010] As an improvement of the negative electrode graphite material, the particle size distribution of the graphite particles is: D10 is 5-13 μm, D50 is 13-17 μm, and D90 is 17-35 μm.

[0011] By adopting the above technical solution, the graphite particles with the particle size distribution are used to prepare the negative electrode graphite material, so that there are suitable gaps between the core-shell particles. The prepared negative electrode structure has higher strength, more lithium storage space and better conductivity.

[0012] Secondly, the present application also proposes a method for producing negative electrode graphite material, and adopts the following technical solution.

[0013] A method for producing a negative electrode graphite material comprises: mixing and grinding maleic anhydride-grafted polyethylene and graphite particles, heating to melt the maleic anhydride and coat the graphite particles, grinding again to disperse the graphite particles coated with the coating material, and then heating to 800-1500° C. in an oxygen-free atmosphere and keeping the temperature for 5-20 hours to obtain the negative electrode graphite material.

[0014] By adopting the above technical solution, maleic anhydride grafted polyethylene is coated on the outer surface of the graphite particles and carbonized, forming a multi-branched carbon chain conductive structure and pores on the surface of the graphite particles, thereby improving the conductivity and lithium storage performance of the material.

[0015] A preferred embodiment of the production method of the negative electrode graphite material is that the graphite particles are made from flake graphite and are pulverized and spheroidized to obtain spheroidized graphite.

[0016] By adopting the above technical solution, the spheroidized graphite is facilitated to be completely coated by the maleic anhydride grafted polyethylene.

[0017] A preferred embodiment of the production method of the negative electrode graphite material is that the sphericity of the spheroidized graphite is ≥80%.

[0018] By adopting the above technical solution, the sphericity of the spheroidized graphite meets the requirement of being completely coated by maleic anhydride grafted polyethylene.

[0019] On the third aspect, this application also proposes a graphite negative electrode and adopts the following technical solution.

[0020] A graphite negative electrode comprises the above-mentioned negative electrode graphite material, and also comprises stannous pyrophosphate, a conductive agent, a binder and a current collector; the negative electrode graphite material, the stannous pyrophosphate, the conductive agent and the binder are uniformly dispersed with each other in a mass ratio of 10: (0.3-0.5): (0.4-0.8): (1.0-1.5) and are solidified on the current collector.

[0021] By adopting the above technical solution, stannous pyrophosphate is added to the negative electrode, which has stable properties, is insoluble in general electrolytes, and has a certain protective effect on the negative electrode structure. Stannous pyrophosphate has a good dispersion effect in the negative electrode graphite material, conductive agent and binder, so that stannous pyrophosphate is dispersed in the negative electrode material to enrich the number of negative electrode micropores and improve the wetting efficiency of the electrolyte on the negative electrode, which is beneficial for the first charge and discharge of the battery. When lithium ions are embedded in the negative electrode surface, a relatively complete SEI film is grown. The complete SEI film can improve the efficiency of lithium ion embedding and detachment from the graphite negative electrode, and also provide a larger storage space for lithium ions to be embedded in the negative electrode, thereby improving the capacity and cycle performance of the negative electrode. The above makes it possible to add stannous pyrophosphate to the negative electrode to improve the compatibility of the negative electrode with a variety of electrolytes. The growth of lithium dendrites is mainly due to the fact that lithium ions cannot be efficiently embedded in the negative electrode and grow on the surface of the negative electrode. This solution grows a relatively complete SEI film on the surface of the negative electrode, which improves the efficiency of lithium ion embedding in the negative electrode, and thus can inhibit the growth of lithium dendrites on the surface of the negative electrode.

[0022] Fourthly, the present application also proposes a method for producing a graphite negative electrode, and adopts the following technical solution.

[0023] A method for producing a graphite negative electrode comprises mixing the negative electrode graphite material, stannous pyrophosphate, the conductive agent, the binder and a solvent into a slurry, coating the slurry on the current collector, and drying and solidifying the slurry to obtain the graphite negative electrode.

[0024] By adopting the above technical solution, the method is simple and has wide applicability, and the prepared graphite negative electrode has good compatibility with various electrolytes.

[0025] In summary, the negative electrode graphite material, graphite negative electrode and its production method of the present application have the following beneficial effects: maleic anhydride grafted polyethylene forms a structurally rich conductive carbon chain after carbonization on the surface of graphite particles, and increases the number of micropores inside the negative electrode, thereby increasing the capacity of the negative electrode to store lithium ions, and has good compatibility with a variety of electrolytes. In both aqueous and organic electrolytes, the negative electrode graphite material has good conductivity, large capacity and good cycle performance.

[0026] The addition of stannous pyrophosphate to the negative electrode has a certain protective effect on the negative electrode structure, enriches the number of negative electrode micropores, and improves the capacity and cycle performance of the negative electrode. The addition of stannous pyrophosphate to the negative electrode can improve the compatibility of the negative electrode with a variety of electrolytes and inhibit the growth of lithium dendrites on the surface of the negative electrode.

[0027] The negative electrode graphite material and the production method of the graphite negative electrode of the present application are simple and have wide applicability. The relatively low-cost maleic anhydride-grafted polyethylene and stannous pyrophosphate are used to improve the negative electrode performance, and the negative electrode has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 SEM image of the negative electrode graphite material of Example 1.

[0029] Figure 2 SEM image of the negative electrode graphite material of Example 2. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to specific examples and accompanying drawings. The advantages and features of the present invention will become more apparent as the description progresses. It should be noted that, in the following examples, where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer were used. Unless otherwise specified, the raw materials used in the following examples are commercially available.

[0031] Example 1: This example prepares a negative electrode graphite material, and the preparation steps are as follows.

[0032] Natural flake graphite is used as raw material and crushed.

[0033] The crushed graphite is spheroidized by graphite spheroidizing equipment to make the sphericity of the graphite reach 80%, and then screened to control the graphite particle size range of D10>5μm, D50=15±2μm, and D90<40μm.

[0034] Maleic anhydride grafted polyethylene is used as the coating material, and the coating material is mixed with spheroidized graphite particles in a mass ratio of 5:100; then ground for 5 hours to fully grind the coating material and evenly disperse it with the graphite particles; first heat to 150°C to melt the maleic anhydride grafted polyethylene and coat it on the surface of the graphite particles; grind again to disperse the graphite particles coated with the coating material; then heat to 1000°C under a nitrogen protective atmosphere and keep warm for 10 hours to achieve carbonization of the coating material on the surface of the graphite particles; finally, the coated graphite is demagnetized and sieved to obtain a negative electrode graphite material, whose microstructure is as follows Figure 1 shown.

[0035] Example 2: This example prepares a negative electrode graphite material, and the preparation steps are as follows.

[0036] Natural flake graphite is used as raw material and crushed.

[0037] The crushed graphite is spheroidized by graphite spheroidizing equipment to make the sphericity of the graphite reach 80%, and then screened to control the graphite particle size range of D10>5μm, D50=15±2μm, and D90<40μm.

[0038] Maleic anhydride grafted polyethylene is used as the coating material, and the coating material is mixed with spheroidized graphite particles in a mass ratio of 2:100; then ground for 5 hours to fully grind the coating material and evenly disperse it with the graphite particles; first heat to 150°C to melt the maleic anhydride grafted polyethylene and coat it on the surface of the graphite particles; grind again to disperse the graphite particles coated with the coating material; then heat to 1000°C under a nitrogen protective atmosphere and keep warm for 10 hours to achieve carbonization of the coating material on the surface of the graphite particles; finally, the coated graphite is demagnetized and sieved to obtain a negative electrode graphite material, whose microstructure is as follows Figure 2 shown.

[0039] Example 3: This example prepares a negative electrode graphite material, and the preparation steps are as follows.

[0040] Natural flake graphite is used as raw material and crushed.

[0041] The crushed graphite is spheroidized by graphite spheroidizing equipment to make the sphericity of the graphite reach 80%, and then screened to control the graphite particle size range of D10>5μm, D50=15±2μm, and D90<40μm.

[0042] Maleic anhydride grafted polyethylene is used as the coating material, and the coating material and spheroidized graphite particles are mixed in a mass ratio of 10:100; then ground for 5 hours to ensure that the coating material is fully ground and evenly dispersed with the graphite particles; first heat to 150°C to melt the maleic anhydride grafted polyethylene and coat the surface of the graphite particles, and then grind again to disperse the graphite particles coated with the coating material; then, under a nitrogen protective atmosphere, heat to 1500°C and keep warm for 20 hours to achieve carbonization of the coating material on the surface of the graphite particles; finally, the coated graphite is demagnetized and sieved to obtain a negative electrode graphite material.

[0043] Example 4: In this example, a graphite negative electrode is prepared, and the preparation steps are as follows.

[0044] The negative electrode graphite material prepared in Example 1 was mixed with stannous pyrophosphate, carbon black conductive agent and styrene-butadiene rubber binder in a mass ratio of 10:0.4:0.6:1.2 to form a powder mixture. N-methylpyrrolidone was used as a solvent, and the powder mixture and the solvent were mixed in a ratio of 1 g:1 mL. The mixture was stirred into a slurry, and the slurry was coated on a copper foil current collector with a thickness of 10 μm. The slurry coating thickness was 200 μm, and the mixture was dried and solidified to obtain a graphite negative electrode.

[0045] Example 5: In this example, a graphite negative electrode is prepared, and the preparation steps are as follows.

[0046] The negative electrode graphite material prepared in Example 2 was mixed with stannous pyrophosphate, carbon black conductive agent and styrene-butadiene rubber binder in a mass ratio of 10:0.3:0.4:1.5 to form a powder mixture. N-methylpyrrolidone was used as a solvent, and the powder mixture and the solvent were mixed in a ratio of 1 g:1 mL. The mixture was stirred into a slurry, and the slurry was coated on a copper foil current collector with a thickness of 10 μm. The slurry coating thickness was 200 μm, and the mixture was dried and solidified to obtain a graphite negative electrode.

[0047] Example 6: In this example, a graphite negative electrode is prepared, and the preparation steps are as follows.

[0048] The negative electrode graphite material prepared in Example 3 was mixed with stannous pyrophosphate, carbon black conductive agent and styrene-butadiene rubber binder in a mass ratio of 10:0.5:0.8:1.0 to form a powder mixture. N-methylpyrrolidone was used as a solvent, and the powder mixture and the solvent were mixed in a ratio of 1 g:1 mL. The mixture was stirred into a slurry, and the slurry was coated on a copper foil current collector with a thickness of 10 μm. The slurry coating thickness was 200 μm, and the mixture was dried and solidified to obtain a graphite negative electrode.

[0049] Comparative Example 1

[0050] This comparative example prepares a negative electrode graphite material. Compared with Example 1, this comparative example also uses maleic anhydride grafted polyethylene as the coating material, but does not carbonize it. The preparation steps of this comparative example are as follows.

[0051] Natural flake graphite is used as raw material and crushed.

[0052] The crushed graphite is spheroidized by graphite spheroidizing equipment to make the sphericity of the graphite reach 80%, and then screened to control the graphite particle size range of D10>5μm, D50=15±2μm, and D90<40μm.

[0053] Maleic anhydride grafted polyethylene is used as the coating material, and the coating material is mixed with spheroidized graphite particles in a mass ratio of 5:100; then it is ground for 5 hours to make the coating material fully ground and evenly dispersed with the graphite particles; then the temperature is raised to 150°C to melt the maleic anhydride grafted polyethylene and coat the surface of the graphite particles; it is ground again to disperse the graphite particles coated with the coating material, and finally the coated graphite is demagnetized and sieved to obtain the negative electrode graphite material.

[0054] Comparative Example 2

[0055] In this comparative example, a negative electrode graphite material is prepared. The only difference compared to Example 1 is that the maleic anhydride grafted polyethylene is replaced by polyethylene. In this comparative example, the polyethylene is also carbonized, and other conditions remain unchanged.

[0056] Comparative Example 3

[0057] In this comparative example, a negative electrode graphite material is prepared. Compared with Example 1, the difference is that the maleic anhydride grafted polyethylene is replaced with maleic anhydride grafted polypropylene, and the temperature at which the maleic anhydride grafted polypropylene is melted and coated on the surface of the graphite particles is changed to 200°C. In this comparative example, the maleic anhydride grafted polypropylene is also carbonized, and other conditions remain unchanged.

[0058] Comparative Example 4

[0059] In this comparative example, the negative electrode graphite material prepared in Comparative Example 1 was used to prepare a graphite negative electrode. The preparation steps were the same as those in Example 4, as follows.

[0060] Take comparative example 1 to prepare the negative electrode graphite material, and mix it with stannous pyrophosphate, carbon black conductive agent and styrene-butadiene rubber binder in a mass ratio of 10:0.4:0.6:1.2 to form a powder mixture. Use N-methylpyrrolidone as solvent, and mix the powder mixture and the solvent in a ratio of 1g:1mL. Stir into a slurry, and coat the slurry on a copper foil current collector with a thickness of 10μm. The slurry coating thickness is 200μm, and it is dried and cured to obtain a graphite negative electrode.

[0061] Comparative Example 5

[0062] In this comparative example, the negative electrode graphite material prepared in Comparative Example 2 was used to prepare a graphite negative electrode. The preparation steps were the same as those in Example 4, as follows.

[0063] Take comparative example 2 to prepare the negative electrode graphite material, and mix it with stannous pyrophosphate, carbon black conductive agent and styrene-butadiene rubber binder in a mass ratio of 10:0.4:0.6:1.2 to form a powder mixture. N-methylpyrrolidone is used as a solvent, and the powder mixture and the solvent are mixed in a ratio of 1g:1mL. Stir into a slurry, and apply the slurry on a copper foil current collector with a thickness of 10μm. The slurry coating thickness is 200μm, and it is dried and solidified to obtain a graphite negative electrode.

[0064] Comparative Example 6

[0065] In this comparative example, the negative electrode graphite material prepared in Comparative Example 3 was used to prepare a graphite negative electrode. The preparation steps were the same as those in Example 4, as follows.

[0066] Take comparative example 3 to prepare the negative electrode graphite material, and mix it with stannous pyrophosphate, carbon black conductive agent and styrene-butadiene rubber binder in a mass ratio of 10:0.4:0.6:1.2 to form a powder mixture. Use N-methylpyrrolidone as solvent, and mix the powder mixture and the solvent in a ratio of 1g:1mL. Stir into a slurry, and coat the slurry on a copper foil current collector with a thickness of 10μm. The slurry coating thickness is 200μm, and it is dried and cured to obtain a graphite negative electrode.

[0067] Comparative Example 7

[0068] In this comparative example, the negative electrode graphite material prepared in Example 1 is used to prepare a graphite negative electrode. Compared with Example 4, the preparation steps thereof are different from those in Example 4, except that stannous pyrophosphate is used. The preparation steps of this comparative example are as follows.

[0069] The negative electrode graphite material prepared in Example 1 was mixed with a carbon black conductive agent and a styrene-butadiene rubber binder in a mass ratio of 10:0.6:1.2 to form a powder mixture. N-methylpyrrolidone was used as a solvent, and the powder mixture and the solvent were mixed in a ratio of 1 g:1 mL. The mixture was stirred into a slurry, and the slurry was coated on a copper foil current collector with a thickness of 10 μm. The slurry coating thickness was 200 μm, and the mixture was dried and solidified to obtain a graphite negative electrode.

[0070] Test Example 1

[0071] The particle size, tap density, specific surface area, and fixed carbon of the negative electrode graphite materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested as follows: particle size was measured using a Malvern Mastersizer 3000; tap density was measured using a BT-300; specific surface area was measured using a JW-DX dynamic nitrogen adsorption tester; and fixed carbon was measured in accordance with GB / T 3521-2008.

[0072] Electrochemical performance test (including first discharge specific capacity and first discharge efficiency): Any of the graphite negative electrodes in Examples 4-6 and Comparative Examples 4-7 was used as the negative electrode. A metal lithium sheet was used as the positive electrode. A polypropylene porous membrane (Celgard 2300) was used as the separator. Three electrolytes were used to test the compatibility of the negative electrode with the three electrolytes. The first electrolyte used a solvent of DMC:DEC:EC in a volume ratio of 1:1:1, and a solute of 1 mol / L LiPF6, where DMC is dimethyl carbonate, DEC is diethyl carbonate, and EC is ethylene carbonate. The second electrolyte used a solvent of methanol and water in a volume ratio of 1:1, and a solute of 1 mol / L LiClO4. The third electrolyte used a solvent of methanol and water in a volume ratio of 1:1, and a solute of 1 mol / L LiBF4. Lithium-ion batteries with the same structure and usage as above were assembled and tested using a Blue Power battery testing system. The test range was 0.001-2.0V, and the charge and discharge were performed at a rate of 0.1C.

[0073] The compatibility of the negative electrode with the three electrolytes can be tested by referring to the test results of the K value. The K value indicates the penetration ability of the electrolyte into the material, and the test method of the K value is as follows. The compatibility of the negative electrode graphite material with the lithium hexafluorophosphate electrolyte is evaluated by the penetration ability of the electrolyte into the negative electrode graphite material. The specific test method is as follows: take a certain amount of any electrolyte configured in Test Example 1, and drip the electrolyte onto the negative electrode graphite material at a height of 5 mm vertically above the material. Read the time it takes for the electrolyte to be completely absorbed by the material (recorded as the penetration time t), calculate the trace area formed by the electrolyte when the material absorbs the electrolyte (recorded as the penetration area), and finally the calculation formula of the K value is:

[0074]

[0075] Where K represents the penetration ability of the electrolyte into the material; V represents the volume of the electrolyte that penetrates into the material; t represents the penetration time of the electrolyte with volume V into the material; S represents the trace area formed on the surface of the material due to the penetration of the electrolyte V within the time t; ρ represents the compaction density of the material; l represents the thickness of the material after compaction.

[0076] The test results of the above test items are shown in Tables 1 to 3.

[0077] Table 1 Statistics of some properties of negative electrode graphite materials

[0078]

[0079] Table 2 K value test statistics of negative electrode graphite materials

[0080]

[0081] Table 3 Electrical performance test statistics

[0082]

[0083] Table 2 shows that the K value of the negative electrode graphite materials of Examples 1-3 was measured to be 15.71-16.57 g / (cm 3 ·S), indicating that the negative electrode graphite material and the electrolyte have good compatibility. The K value of comparative example 1 is 11.39-12.20 g / (cm 3 ·S), indicating that the negative electrode graphite material of Comparative Example 1 has poor compatibility with the electrolyte. It can be seen that if the maleic anhydride grafted polyethylene is not carbonized, the compatibility of the negative electrode graphite material and the electrolyte will decrease. The K value of Comparative Example 2 is 12.72-13.38 g / (cm 3 ·S), indicating that the negative electrode graphite material of Comparative Example 2 has poor compatibility with the electrolyte. It can be seen that replacing maleic anhydride grafted polyethylene with polyethylene reduces the compatibility of the negative electrode graphite material with the electrolyte. The K value of Comparative Example 3 is 14.15-14.43 g / (cm 3 ·S), indicating that the negative electrode graphite material of Comparative Example 3 has poor compatibility with the electrolyte. It can be seen that if maleic anhydride grafted polyethylene is replaced by maleic anhydride grafted polypropylene, the compatibility of the negative electrode graphite material and the electrolyte decreases.

[0084] Table 3 shows that Example 4-6 has a higher first discharge specific capacity and first discharge efficiency than Comparative Example 4-7, indicating that the graphite negative electrode prepared in Example 4-6 has more lithium storage space and higher lithium ion embedding efficiency in the negative electrode, which can also inhibit the growth of lithium dendrites. The raw material of Comparative Example 4 did not carbonize the maleic acid grafted polyethylene, and the conductivity and lithium storage space of the negative electrode were reduced, which reduced the first discharge specific capacity and first discharge efficiency of the battery. The graphite negative electrode prepared in Comparative Example 5 uses polyethylene instead of maleic anhydride grafted polyethylene for carbonization. It has no grafting structure, and the conductivity and lithium storage space of the negative electrode are reduced, which reduces the first discharge specific capacity and first discharge efficiency of the battery. The graphite negative electrode prepared in Comparative Example 6 was carbonized using maleic anhydride grafted polypropylene instead of maleic anhydride grafted polyethylene. The grafting rate of maleic anhydride grafted polypropylene was approximately 1.4%, and the grafting rate of maleic anhydride grafted polyethylene was approximately 8%. The lower grafting rate of maleic anhydride grafted polypropylene resulted in a decrease in the conductivity and lithium storage space of the negative electrode, which reduced the battery's initial discharge capacity and initial discharge efficiency. Comparative Example 7 prepared the graphite negative electrode without adding stannous pyrophosphate. In addition to significantly reducing the lithium storage space and lowering the conductivity, it was also not conducive to the growth of a relatively complete SEI film, making the negative electrode less compatible with various electrolytes, reducing the battery's initial discharge capacity and initial discharge efficiency.

[0085] This application improves the compatibility of graphite with various electrolytes by surface modification of natural graphite and enhances the electrochemical performance of the graphite material. Furthermore, by adding stannous pyrophosphate when preparing the graphite negative electrode, it has a certain protective effect on the negative electrode structure, enriches the number of negative electrode micropores, improves the wetting efficiency of the electrolyte on the negative electrode, and improves the capacity and discharge efficiency of the negative electrode, that is, further improving the compatibility of the graphite negative electrode with various electrolytes. The negative electrode graphite material and graphite negative electrode of this application are suitable for use in high-energy-density lithium-ion batteries and can improve the electrical performance of the battery.

[0086] The above are only some embodiments of the present application. The scope of protection of the present application is not limited to the above embodiments. For those skilled in the art, several improvements and extensions made according to the above embodiments without departing from the creativity of the present application should also fall within the scope of protection of the present application.

Claims

1. A graphite negative electrode, characterized in that The invention comprises a negative electrode graphite material, stannous pyrophosphate, a conductive agent, a binder and a current collector; the negative electrode graphite material, the stannous pyrophosphate, the conductive agent and the binder are uniformly dispersed with each other in a mass ratio of 10: (0.3-0.5): (0.4-0.8): (1.0-1.5) and solidified on the current collector; The negative electrode graphite material comprises core-shell particles with a shell layer covering a core layer; the shell layer is carbonized maleic anhydride grafted polyethylene; and the core layer is graphite particles; The mass ratio of the uncarbonized maleic anhydride grafted polyethylene and the graphite particles used to prepare the negative electrode graphite material is (2-10):

100.

2. The graphite negative electrode according to claim 1, characterized in that The particle size distribution of the graphite particles is: D10 is 5-13 μm, D50 is 13-17 μm, and D90 is 17-35 μm.

3. The graphite negative electrode according to claim 1 or 2, characterized in that The production method of the negative electrode graphite material includes: mixing and grinding maleic anhydride grafted polyethylene and graphite particles, heating to melt the maleic anhydride grafted polyethylene and coat the surface of the graphite particles, grinding again to disperse the graphite particles coated with the coating material, and then heating to 800-1500°C in an oxygen-free atmosphere and keeping the temperature for 5-20 hours to obtain the negative electrode graphite material.

4. The graphite negative electrode according to claim 3, characterized in that The graphite particles are spheroidized graphite obtained by crushing and spheroidizing flake graphite as a raw material.

5. The graphite negative electrode according to claim 4, characterized in that The sphericity of the spheroidized graphite is ≥80%.

6. A method for producing a graphite negative electrode according to claim 1, characterized in that: The negative electrode graphite material, the stannous pyrophosphate, the conductive agent, the binder and a solvent are mixed into a slurry, the slurry is coated on the current collector, and the mixture is dried and solidified to obtain the graphite negative electrode.

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