Graphite negative electrode material with excellent high-temperature performance and preparation method thereof

Abstract

The application provides a graphite negative electrode material with excellent high-temperature performance and a preparation method thereof, and the preparation method comprises the following steps: mixing raw coke and a binder, granulating, graphitizing, and obtaining artificial graphite; mixing the artificial graphite with an acid solution and an aniline monomer, polymerizing, and coating polyaniline on the surface of the artificial graphite, namely the graphite negative electrode material. By coating a layer of polyaniline on the surface of the artificial graphite, the polyaniline has good thermal stability, and the introduction of the polyaniline into the graphite negative electrode material can significantly improve the high-temperature resistance of the artificial graphite, and solves the problem of rapid capacity attenuation of the graphite negative electrode material in high-temperature cycles and high-temperature storage.

Description

Technical Field

[0001] This invention belongs to the field of anode material technology, and particularly relates to a graphite anode material with excellent high-temperature performance and its preparation method. Background Technology

[0002] Lithium-ion batteries hold a crucial position in the power, consumer, and energy storage sectors due to their high energy density, long cycle life, and rapid charge / discharge capabilities. Although the manufacturing technology of power lithium-ion batteries is becoming increasingly mature, harsh operating environments still present numerous challenges. High-temperature operating scenarios, such as high temperatures in summer and prolonged high-load operation, accelerate the capacity degradation of power batteries and may even lead to thermal runaway risks. To address the performance degradation and safety issues caused by high temperatures, improving the high-temperature performance of anode materials has become a key consideration in the design of battery cell anode materials.

[0003] Both natural and synthetic graphite are currently the mainstream choices for lithium-ion battery anode materials, offering significant advantages such as low cost, excellent electrochemical performance, and environmental friendliness. However, natural graphite, purified from minerals, has a complete layered structure but high edge activity. At high temperatures, the electrolyte is prone to side reactions at these edges, leading to repeated rupture and regeneration of the SEI film and accelerating capacity decay. Furthermore, the small interlayer spacing of natural graphite can cause structural expansion due to lithium-ion intercalation / deintercalation at high temperatures. In contrast, synthetic graphite has fewer surface defects and a lower specific surface area, resulting in fewer high-temperature-induced side reactions. Therefore, in terms of high-temperature performance, synthetic graphite is a superior anode material for lithium-ion batteries.

[0004] Although synthetic graphite has a superior surface structure, further improvements to its high-temperature performance still require material modifications. A common method to enhance the high-temperature performance of graphite anode materials is surface modification and coating. The coating layer reduces direct contact between graphite and the electrolyte, inhibiting excessive growth and decomposition of the SEI film at high temperatures. Simultaneously, coating reduces the specific surface area of ​​the material, minimizing side reactions under high-temperature conditions, thereby improving the high-temperature storage and cycling performance of the anode material. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a graphite anode material with excellent high-temperature performance and its preparation method. By modifying the surface of artificial graphite by coating it with polyaniline, the high-temperature performance of artificial graphite can be effectively improved, and the high-temperature cycling stability of the graphite anode material can be greatly improved.

[0006] The present invention proposes a method for preparing a graphite anode material with excellent high-temperature performance, comprising the following steps: S1. Mix the raw coke with a binder, granulate, and graphitize to obtain artificial graphite; S2. Artificial graphite is mixed with acid solution and aniline monomer, and after polymerization, polyaniline is coated on the surface of artificial graphite to obtain the graphite anode material.

[0007] In this invention, by coating the surface of artificial graphite with a layer of polyaniline, which has good thermal stability, the introduction of polyaniline into the graphite anode material can significantly improve the high temperature resistance of artificial graphite and solve the problem of rapid capacity decay of graphite anode materials in high temperature cycling and high temperature storage.

[0008] Preferably, the raw material coke is at least one of needle coke, petroleum coke, pitch coke, spherical coke, sponge coke, or honeycomb coke; and the binder is at least one of coal tar pitch, petroleum pitch, coal tar, or natural pitch. Preferably, the mass ratio of the raw coke to the binder is 1:0.05-0.15.

[0009] Preferably, the granulation temperature is 600-700℃ and the time is 4-8h; the graphitization temperature is 2600-3000℃ and the time is 10-30h.

[0010] Preferably, the acid solution is at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, or glacial acetic acid; Preferably, the concentration of the acid solution is 0.5-2 mol / L.

[0011] Preferably, the mass ratio of the artificial graphite to the aniline monomer is 1:1.5-3; Preferably, the polymerization is carried out under initiator conditions, wherein the initiator is at least one of ammonium persulfate or potassium persulfate.

[0012] Preferably, before coating the surface of the artificial graphite with polyaniline, a sulfonate polyimide modification layer is further coated on the surface of the artificial graphite, specifically including: Artificial graphite is obtained by coupling it with an aminosilane coupling agent and then copolymerizing it with diamine and dianhydride containing sulfonic acid groups.

[0013] Preferably, the diamine containing a sulfonic acid group is at least one selected from 2,2'-benzidine disulfonic acid, 4,4-bis(4-aminophenoxy)biphenyl-3,3-disulfonic acid, 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, or 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid; and the dianhydride is at least one selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, or 1,2,3,4-cyclopentanetetracarboxylic dianhydride. Preferably, the mass ratio of the artificial graphite, aminosilane coupling agent, diamine containing sulfonic acid group and dianhydride is 1:0.02-0.1:0.01-0.05:0.02-0.1.

[0014] Preferably, the copolymerization reaction temperature is 160-200℃ and the time is 6-12h.

[0015] In this invention, artificial graphite is coupled to an aminosilane coupling agent, and then amino groups are grafted onto the surface. Following this, a copolymerization reaction is carried out with diamine and dianhydride containing sulfonic acid groups, resulting in the coating of sulfonic acid polyimide on the surface of the artificial graphite. On one hand, sulfonic acid polyimide possesses high-temperature resistance, which can further improve the high-temperature performance of artificial graphite. On the other hand, the introduction of sulfonic acid groups can bind with aniline monomers through ionic bonds, promoting the directional growth of polyaniline on the surface of artificial graphite. This improves the structural stability of the graphite anode material while also increasing the intermolecular forces, which is of great significance for maintaining the high-temperature performance of the anode material during long-term use.

[0016] This invention also proposes a graphite anode material with excellent high-temperature performance, which is prepared by the above-mentioned preparation method.

[0017] The present invention also proposes a lithium-ion battery anode, comprising the above-mentioned graphite anode material with excellent high-temperature performance.

[0018] Compared with the prior art, the present invention has the following technical effects: The graphite anode material prepared by this invention can significantly increase the high-temperature performance of artificial graphite and has excellent electrochemical performance, especially high-temperature cycling performance and high-temperature storage performance. Attached Figure Description

[0019] Figure 1 This is a SEM image of the graphite anode material described in Example 1. Detailed Implementation

[0020] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0021] Example 1 A graphite anode material with excellent high-temperature performance is prepared by the following method: (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed and ground to obtain needle coke powder with a particle size D50 of 10μm; the obtained needle coke powder was mixed with coal tar pitch (softening point of 150℃, residual carbon value of 56%) at a mass ratio of 1:0.1, and then added to a granulation kettle for granulation. Under N2 protection, the temperature was raised to 650℃ and kept for 6h. After cooling to room temperature, it was graphitized at 2800℃ for 16h. After cooling, ball milling and sieving, artificial graphite was obtained. (2) Artificial graphite was added to a 1 mol / L hydrochloric acid solution and sonicated for 30 min. After filtration, washing, and drying, it was added to a 1 mol / L hydrochloric acid solution containing aniline. The mass ratio of artificial graphite to aniline was 1:2. After stirring and mixing for 1 h, a 0.1 mol / L ammonium persulfate solution was slowly added dropwise. The mass ratio of aniline to ammonium persulfate was 1:0.05. The reaction was stirred at room temperature for 3 h. The reaction was terminated by adding ethanol. After filtration, the material was washed three times with deionized water and ethanol. After vacuum drying at 80 °C, it was treated at 150 °C for 2 h and then heated to 200 °C for 1 h to obtain the graphite anode material. Its microstructure is as shown in the figure. Figure 1 As shown.

[0022] Example 2 A graphite anode material with excellent high-temperature performance is prepared by the following method: (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed and ground to obtain needle coke powder with a particle size D50 of 10μm; the obtained needle coke powder was mixed with coal tar pitch (softening point of 150℃, residual carbon value of 56%) at a mass ratio of 1:0.05, and then added to a granulation kettle for granulation. Under N2 protection, the temperature was raised to 600℃ and kept for 8h. After cooling to room temperature, it was graphitized at 2600℃ for 24h. After cooling, ball milling and sieving, artificial graphite was obtained. (2) Add artificial graphite to a 0.5 mol / L hydrochloric acid solution and sonicate for 30 min. After filtration, washing, and drying, add artificial graphite to a 0.5 mol / L hydrochloric acid solution containing aniline. The mass ratio of artificial graphite to aniline is 1:1.5. After stirring and mixing for 1 h, slowly add 0.1 mol / L ammonium persulfate solution. The mass ratio of aniline to ammonium persulfate is 1:0.05. Stir and react at room temperature for 2 h. Add ethanol to terminate the reaction. Filter, wash three times with deionized water and ethanol, dry under vacuum at 80 °C, treat at 150 °C for 2 h, and then heat to 200 °C for 1 h to obtain the graphite anode material.

[0023] Example 3 A graphite anode material with excellent high-temperature performance is prepared by the following method: (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed and ground to obtain needle coke powder with a particle size D50 of 10μm; the obtained needle coke powder was mixed with coal tar pitch (softening point of 150℃, residual carbon value of 56%) at a mass ratio of 1:0.15, and then added to a granulation kettle for granulation. Under N2 protection, the temperature was raised to 700℃ and kept for 4h. After cooling to room temperature, it was graphitized at 3000℃ for 12h. After cooling, ball milling and sieving, artificial graphite was obtained. (2) Add artificial graphite to a 2 mol / L hydrochloric acid solution and sonicate for 30 min. After filtration, washing, and drying, add artificial graphite to a 2 mol / L hydrochloric acid solution containing aniline. The mass ratio of artificial graphite to aniline is 1:3. After stirring and mixing for 1 h, slowly add 0.1 mol / L ammonium persulfate solution. The mass ratio of aniline to ammonium persulfate is 1:0.05. Stir and react at room temperature for 4 h. Add ethanol to terminate the reaction. After filtration, wash three times with deionized water and ethanol. After vacuum drying at 80 °C, treat at 150 °C for 2 h and then heat to 200 °C for 1 h to obtain the graphite anode material.

[0024] Example 4 A graphite anode material with excellent high-temperature performance is prepared by the following method: (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed and ground to obtain needle coke powder with a particle size D50 of 10μm; the obtained needle coke powder was mixed with coal tar pitch (softening point of 150℃, residual carbon value of 56%) at a mass ratio of 1:0.1, and then added to a granulation kettle for granulation. Under N2 protection, the temperature was raised to 650℃ and kept for 6h. After cooling to room temperature, it was graphitized at 2800℃ for 16h. After cooling, ball milling and sieving, artificial graphite was obtained. (2) Add artificial graphite to anhydrous ethanol and stir to disperse evenly. Then add 3-aminopropyltrimethoxysilane, heat to 80℃ and stir for 1h. After filtration, add the intermediate product to N-methylpyrrolidone. Under nitrogen protection, add 2,2'-benzidine disulfonic acid and 3,3′, 4, 4′-biphenyltetracarboxylic dianhydride. The mass ratio of artificial graphite, 3-aminopropyltrimethoxysilane, 2,2'-benzidine disulfonic acid and 3,3′, 4, 4′-biphenyltetracarboxylic dianhydride is 1:0.05:0.03:0.05. After stirring for 1h, heat to 180℃ and stir for 9h to obtain artificial graphite with a sulfonic acid polyimide modified layer on the surface. (3) Add the artificial graphite with sulfonate polyimide modified layer to a 1 mol / L hydrochloric acid solution and sonicate for 30 min. After filtration, washing and drying, add it to a 1 mol / L hydrochloric acid solution containing aniline. The mass ratio of artificial graphite with sulfonate polyimide modified layer to aniline is 1:2. After stirring and mixing for 1 h, slowly add 0.1 mol / L ammonium persulfate solution. The mass ratio of aniline to ammonium persulfate is 1:0.05. Stir and react at room temperature for 3 h. Add ethanol to terminate the reaction. After filtration, wash three times with deionized water and ethanol. After vacuum drying at 80 °C, treat at 150 °C for 2 h and then heat to 200 °C for 1 h to obtain the graphite anode material.

[0025] Comparative Example 1 A graphite anode material with excellent high-temperature performance is prepared by the following method: (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed and ground to obtain needle coke powder with a particle size D50 of 10μm; the obtained needle coke powder was graphitized at 2800℃ for 16h, cooled, ball-milled and sieved to obtain artificial graphite. (2) Add artificial graphite to a 1 mol / L hydrochloric acid solution and sonicate for 30 min. After filtration, washing, and drying, add artificial graphite to a 1 mol / L hydrochloric acid solution containing aniline. The mass ratio of artificial graphite to aniline is 1:2. After stirring and mixing for 1 h, slowly add 0.1 mol / L ammonium persulfate solution. The mass ratio of aniline to ammonium persulfate is 1:0.05. Stir and react at room temperature for 3 h. Add ethanol to terminate the reaction. Filter, wash three times with deionized water and ethanol, dry under vacuum at 80 °C, treat at 150 °C for 2 h, and then heat to 200 °C for 1 h to obtain the graphite anode material.

[0026] Comparative Example 2 A graphite anode material with excellent high-temperature performance is prepared by the following method: Needle coke (volatile matter ≤10.0%) was used as raw material, crushed, and ground to obtain needle coke powder with a particle size D50 of 10μm. The obtained needle coke powder was mixed with coal tar pitch (softening point 150℃, residual carbon value 56%) at a mass ratio of 1:0.1, and then added to a granulation reactor for granulation. Under N2 protection, the temperature was raised to 650℃ and held for 6 hours. After cooling to room temperature, it was graphitized at 2800℃ for 16 hours. After cooling, ball milling, and sieving, artificial graphite was obtained, which is the graphite anode material.

[0027] Comparative Example 3 A graphite anode material with excellent high-temperature performance is prepared according to Example 4. Except for step (3), the artificial graphite with a sulfonate polyimide modified layer on the surface obtained in step (2) is directly treated at 150°C for 2 hours and then heated to 200°C for 1 hour to obtain the graphite anode material.

[0028] Comparative Example 4 A graphite anode material with excellent high-temperature performance was prepared according to Example 4, except that in step (2), artificial graphite was added to anhydrous ethanol and stirred to disperse evenly, then 3-aminopropyltrimethoxysilane was added, the temperature was raised to 80°C and stirred for 1 hour, and after filtration, the intermediate product was added to N-methylpyrrolidone, and 4,4'-diaminobiphenyl and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added under nitrogen protection. The mass ratio of artificial graphite, 3-aminopropyltrimethoxysilane, 4,4'-diaminobiphenyl and 3,3',4,4'-biphenyltetracarboxylic dianhydride was 1:0.05:0.03:0.05. After stirring for 1 hour, the temperature was raised to 180°C and stirred for 9 hours to obtain artificial graphite with a sulfonate polyimide modified layer on the surface.

[0029] The graphite anode materials described in the examples and comparative examples were respectively formulated into anode slurries with conductive agent (SuperP), binder (CMC), and binder (SBR) in a weight ratio of 96.5:0.5:2:1. These slurries were then coated onto the surface of copper foil, dried, and stamped to form the anode material. Conversely, the positive electrode active material (LFP) was formulated into anode slurries with conductive agent (SuperP) and binder (PVDF) in a weight ratio of 97:1.5:1.5. These slurries were then coated onto the surface of aluminum foil, dried, and stamped to form the anode material. As the positive electrode, a three-component mixture of EC:DMC:EMC = 1:1:1 (v / v / v) was used as the mixed solvent, and 1 mol / L LiPF6 was added as the electrolyte. A polypropylene microporous membrane was used as the separator. The full cell was assembled in this way. The capacity retention rate at 45℃ and 1000 cycles (1C rate charging / 1C rate discharging at 45℃) and the retention and recovery rate after seven days of high-temperature storage at 55℃ are all full-cell test performance data, as shown in Table 1 below.

[0030] Table 1. Performance comparison of the graphite anode materials described in the examples and comparative examples.

[0031] As shown in Table 1 above, the high-temperature cycling and high-temperature storage performance of Examples 1-3, which are coated with both asphalt and polyaniline, is significantly better than that of Comparative Example 1, which is coated with only polyaniline, and Comparative Example 2, which is coated with only asphalt. The high-temperature cycling and high-temperature storage performance of Example 4, which is coated with both sulfonate polyimide modification layer and polyaniline, is better than that of Comparative Example 3, which is coated with only sulfonate polyimide modification layer. The improvement effect of high-temperature performance of Comparative Example 4, which is modified with only polyimide modification layer, is obviously much weaker than that of Example 4, which is modified with sulfonate polyimide modification layer.

[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a graphite anode material with excellent high-temperature performance, characterized in that, Includes the following steps: S1. Mix the raw coke with a binder, granulate, and graphitize to obtain artificial graphite; S2. Mix artificial graphite with acid solution and aniline monomer, polymerize, and then coat the surface of artificial graphite with polyaniline to obtain the graphite anode material. Before coating the artificial graphite surface with polyaniline, the process also includes coating the artificial graphite surface with a sulfonate polyimide modification layer, specifically including: Artificial graphite is obtained by coupling it with an aminosilane coupling agent and then copolymerizing it with a diamine and dianhydride containing sulfonic acid groups. The mass ratio of the artificial graphite to the aniline monomer is 1:1.5-3; The mass ratio of the artificial graphite, aminosilane coupling agent, diamine containing sulfonic acid group and dianhydride is 1:0.02-0.1:0.01-0.05:0.02-0.

1.

2. The method for preparing the high-temperature performance graphite anode material according to claim 1, characterized in that, The raw material coke is at least one of needle coke, petroleum coke, pitch coke, spherical coke, sponge coke, or honeycomb coke; the binder is at least one of coal tar pitch, petroleum pitch, coal tar, or natural pitch.

3. The method for preparing the high-temperature performance graphite anode material according to claim 1 or 2, characterized in that, The mass ratio of the raw coke to the binder is 1:0.05-0.

15.

4. The method for preparing the high-temperature performance graphite anode material according to claim 1 or 2, characterized in that, The granulation temperature is 600-700℃ and the time is 4-8h; the graphitization temperature is 2600-3000℃ and the time is 10-30h.

5. The method for preparing the high-temperature performance graphite anode material according to claim 1 or 2, characterized in that, The acid solution is at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, or glacial acetic acid.

6. The method for preparing the high-temperature performance graphite anode material according to claim 1 or 2, characterized in that, The concentration of the acid solution is 0.5-2 mol / L.

7. The method for preparing the high-temperature performance graphite anode material according to claim 1 or 2, characterized in that, The polymerization is carried out under initiator conditions, wherein the initiator is at least one of ammonium persulfate or potassium persulfate.

8. The method for preparing the high-temperature performance graphite anode material according to claim 1, characterized in that, The diamine containing a sulfonic acid group is at least one of 2,2'-biphenylamine disulfonic acid, 4,4-bis(4-aminophenoxy)biphenyl-3,3-disulfonic acid, 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, or 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid; the dianhydride is at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, or 1,2,3,4-cyclopentanetetracarboxylic dianhydride.

9. The method for preparing the high-temperature performance graphite anode material according to claim 1, characterized in that, The copolymerization reaction temperature is 160-200℃, and the time is 6-12h.

10. A graphite anode material with excellent high-temperature performance, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

11. A lithium-ion battery negative electrode, characterized in that, Including the high-temperature performance graphite anode material as described in claim 10.

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