Graphite composite negative electrode active material, and preparation method and application thereof

Abstract

The application relates to the technical field of lithium ion battery electrode materials, and discloses a graphite composite negative electrode active material, a preparation method and application thereof, the graphite composite negative electrode active material comprises graphite and a coating layer coated on the surface of the graphite; the components of the coating layer include a polymer, a fluorine-containing organic lithium compound and porous carbon particles. Through the technical scheme, the problems of insufficient fast-charging performance and low-temperature performance of the graphite negative electrode material in the related art are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery electrode materials, in particular to a graphite composite negative electrode active material and a preparation method and application thereof. BACKGROUND

[0002] Currently, the fast-charging negative electrode material used in lithium ion batteries is mainly artificial graphite, which mainly improves the fast-charging and low-temperature performance by coating soft carbon or hard carbon on the surface of the material. However, there are problems such as low first efficiency, and under high-temperature storage conditions, repeated formation of SEI film consumes lithium ions and reduces high-temperature storage performance, resulting in low first efficiency. The reason for the poor fast-charging performance and low-temperature performance of graphite negative electrode material is that the consumption of lithium ions during charging and discharging slows down the diffusion speed of lithium ions. Although some researchers have improved the first efficiency and rate performance of the material by coating inorganic lithium salt compounds on the surface of the material, the improvement in the low-temperature performance of the material is not significant. The reason is that although the diffusion coefficient of lithium ions at low temperature is improved to some extent, the improvement is not significant.

[0003] For example, CN114335460A discloses a fast-charging graphite composite material and a preparation method thereof. The graphite composite material includes an inner shell and an outer shell. The outer shell includes an inorganic lithium salt, carbon nanotubes and the balance of amorphous carbon. The inner core includes porous graphite and a solid electrolyte. Although the fast-charging performance is improved, the improvement in the low-temperature performance and first efficiency of the material is not significant.

[0004] For another example, CN115954455A discloses a preparation method of a graphite composite negative electrode material. The method includes: performing a hydrothermal reaction on a silver-ammonia solution and a porous graphite solution to obtain a silver-doped graphite composite material; uniformly dispersing an aluminum salt solution and the silver-doped graphite composite material, filtering and then sintering to obtain an aluminum oxide-coated silver-doped graphite composite material; uniformly dispersing the aluminum oxide-coated silver-doped graphite composite material, an amorphous carbon source, an inorganic lithium compound and a conductive agent in an organic solvent, spray drying and then carbonizing to obtain the graphite composite negative electrode material.

[0005] Although there are many ways to modify graphite in the prior art, the fast-charging performance and low-temperature performance of graphite negative electrode material are still not fully researched, and there is still a lot of room for improvement in performance. SUMMARY

[0006] The present application provides a graphite composite negative electrode active material and a preparation method and application thereof, which solves the problem of insufficient fast-charging performance and low-temperature performance of graphite negative electrode material in the related art.

[0007] The technical scheme of the present application is as follows:

[0008] The graphite composite negative electrode active material comprises graphite and a coating layer coated on the surface of the graphite.

[0009] The components of the coating layer comprise a polymer, a fluorine-containing organic lithium compound and porous carbon particles.

[0010] The fluorine-containing organic lithium compound has the following structural formula:

[0011] ;

[0012] In the formula, R is a hydrocarbon group containing a F substituent.

[0013] As a further technical solution, R is a fluorine-substituted C1-C3 alkyl group, preferably, R is a perfluorinated C1-C3 alkyl group.

[0014] The polymer comprises one or more of an epoxy-based water-based resin, a polyurethane resin, a water-soluble phenolic resin and a water-soluble polyester resin.

[0015] As a further technical solution, the mass ratio of the porous carbon particles, the polymer, the fluorine-containing organic lithium compound and the graphite is 1-10:1-15:0.5-10:100.

[0016] Preferably, the mass ratio of the porous carbon particles, the polymer, the fluorine-containing organic lithium compound and the graphite is 3-5:5-10:0.5-6:100.

[0017] As a further technical solution, the porous carbon particles are lithium- and titanium-modified porous carbon particles.

[0018] As a further technical solution, the preparation method of the porous carbon particles comprises the following steps: mixing a carbon source, a coupling agent, an organic template and an organic lithium compound for pre-reaction, and carbonization treatment to obtain the porous carbon particles.

[0019] As a further technical solution, the mass ratio of the carbon source, the coupling agent, the organic template and the organic lithium compound is 100:1-5:1-5:1-5.

[0020] As a further technical solution, the carbon source comprises one or more of a sugar substance, sucrose, glucose, beta-dextrin or lactose.

[0021] The coupling agent is a titanium-based coupling agent.

[0022] The titanium-based coupling agent comprises one or more of isopropyl tri(dioctyl pyrophosphoryloxy) titanate, tetraisopropyl di(dioctyl phosphityloxy) titanate and bis(dioctyloxy phosphite) ethylene titanate thereof.

[0023] The organic template comprises one or more of polystyrene microspheres, sodium laurate, and polyvinylpyrrolidone.

[0024] The organic lithium compound is one or more of lithium stearate, lithium octadecanoate, lithium acetate, lithium acetate, lithium benzoate, lithium oxalate, and lithium oxalate.

[0025] The organic solvent is added during the pre-reaction.

[0026] The organic solvent comprises one or more of cyclohexane, n-hexane, carbon tetrachloride, or N-methylpyrrolidone.

[0027] As a further technical solution, the pre-reaction temperature is 25-150 DEG C, and the time is 1-6h.

[0028] Preferably, the pre-reaction temperature is 50-120 DEG C.

[0029] The carbonization treatment is carried out in nitrogen or inert gas.

[0030] The application also proposes a preparation method of the graphite composite negative electrode active material, comprising the following steps:

[0031] The porous carbon particles, the polymer, the fluorine-containing organic lithium compound, and the graphite are mixed in a liquid phase, dried, and a graphite composite negative electrode active material is obtained.

[0032] The solvent for the liquid phase mixing comprises water.

[0033] The drying comprises spray drying.

[0034] The application also proposes the application of the graphite composite negative electrode active material or the graphite composite negative electrode active material prepared by the preparation method in a lithium ion battery.

[0035] In the application, first, a carbon source, a coupling agent, an organic template, and an organic lithium compound are pre-reacted and carbonized, based on the lithium and TiO2 combined doped porous carbon particles formed by the pyrolysis of the organic lithium compound and the titanium-based coupling agent, a modified porous carbon particle is prepared, and further, the graphite is modified by components such as the fluorine-containing organic lithium compound, synergy is achieved, the physicochemical structure of the material is optimized, the ion and electron conduction path of the material is improved, the transmission network and efficiency are optimized, defects and expansion are reduced, the structural stability is improved, and the low-temperature and fast-charging performance of the graphite negative electrode material is further improved.

[0036] The working principle and beneficial effects of the application are as follows:

[0037] The graphite composite negative electrode active material provided in the present application comprises graphite and a coating layer coated on the surface of the graphite, and the components of the coating layer comprise a polymer, a fluorine-containing organic lithium compound and porous carbon particles. BRIEF DESCRIPTION OF DRAWINGS

[0038] The present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] Figure 1 SEM image of the graphite composite negative electrode active material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative work fall within the scope of protection of the present application.

[0041] Example 1

[0042] The preparation method of the graphite composite negative electrode active material comprises the following steps:

[0043] S1, 100g of sucrose, 3g of isopropyl tris(dioctyl pyrophosphoryloxy) titanate, 3g of polystyrene microspheres and 3g of lithium stearate are added into 800g of cyclohexane and uniformly dispersed, and then transferred into a high-pressure reaction kettle for reaction at a temperature of 80℃ for 3h, filtered, and the obtained filter residue is vacuum dried at 80℃ for 24h and carbonized at 1150℃ for 3h to obtain porous carbon particles;

[0044] S2, 8g of water-soluble epoxy resin and 300g of 2wt% lithium trifluoromethylsulfonate (LiSO3CF3) aqueous solution are mixed, 3g of the porous carbon particles and 100g of artificial graphite are uniformly dispersed by ultrasonic dispersion, and then spray dried to obtain the graphite composite negative electrode active material.

[0045] Example 2

[0046] The preparation method of the graphite composite negative electrode active material comprises the following steps:

[0047] S1, 100g of sucrose, 3g of isopropyl tris(dioctyl pyrophosphoryloxy) titanate, 3g of polystyrene microspheres and 3g of lithium stearate are added into 800g of cyclohexane and uniformly dispersed, and then transferred into a high-pressure reaction kettle for reaction at a temperature of 80℃ for 3h, filtered, and the obtained filter residue is vacuum dried at 80℃ for 24h and carbonized at 1150℃ for 3h to obtain porous carbon particles;

[0048] S2, 10 g of water-soluble phenol-formaldehyde resin, 40 g of a 5 wt% aqueous solution of lithium perfluorohexanesulfonate (LiSO3C6F13), 3 g of porous carbon particles, and 100 g of artificial graphite were mixed, uniformly dispersed by ultrasonic treatment, and then spray-dried to obtain a graphite composite negative electrode active material.

[0049] Example 3

[0050] A method for preparing a graphite composite negative electrode active material, comprising the following steps:

[0051] S1, 100 g of lactose, 5 g of bis(dioctyloxyphosphato)ethyl titanate, 5 g of polyvinylpyrrolidone, and 5 g of lithium acetate were added to 1000 g of carbon tetrachloride and uniformly dispersed, and then transferred to a high-pressure reaction kettle for reaction at a temperature of 120°C for 1 h. The obtained residue was filtered and dried at 80°C under vacuum for 24 h, and then carbonized at 1300°C for 1 h to obtain porous carbon particles;

[0052] S2, 10 g of water-soluble phenol-formaldehyde resin, 40 g of a 5 wt% aqueous solution of lithium perfluorohexanesulfonate (LiSO3C6F13), 3 g of porous carbon particles, and 100 g of artificial graphite were mixed, uniformly dispersed by ultrasonic treatment, and then spray-dried to obtain a graphite composite negative electrode active material. 13

[0053] Example 4

[0054] The difference between this example and Example 1 is that no isopropyl tris(dioctylphosphato) titanate or lithium stearate is added.

[0055] Example 5

[0056] The difference between this example and Example 1 is that the isopropyl tris(dioctylphosphato) titanate is replaced by titanium dioxide.

[0057] Example 6

[0058] The difference between this example and Example 1 is that the lithium stearate is replaced by lithium hydroxide.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that no lithium trifluoromethylsulfonate (LiSO3CF3) is added.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the lithium trifluoromethylsulfonate (LiSO3CF3) is replaced by Compound II.

[0063] The structural formula of Compound II is as follows:

[0064] ​ .

[0065] 1. SEM test

[0066] The graphite composite negative active material prepared in Example 1 was subjected to SEM test, and the results are shown in FIG. 1. As can be seen from FIG. 1, the material presents a partial spherical structure, and the particle size is between 8-12 pm. Figure 1 Figure 1

[0067] 2. Physicochemical property test

[0068] The tap density, specific surface area of the graphite composite negative active materials in Examples 1-6 and Comparative Examples 1-2 were tested according to the test method in the standard GB / T 24533-2019 “Graphite-based negative active material for lithium ion battery”, and the OI value of the powder material was tested by XRD, and the diffusion coefficient was tested by GITT. The test results are shown in Table 1.

[0069] Table 1. Physicochemical property test

[0070]

[0071] As can be seen from Table 1, the diffusion coefficient, tap density and OI value of the graphite composite negative active materials prepared in Examples 1-3 are significantly better than those of Examples 4-5 and Comparative Examples 1-2.

[0072] 3. Button cell test

[0073] The graphite composite negative active materials prepared in Examples 1-6 and Comparative Examples 1-2 were assembled into button cells according to the following method:

[0074] The negative electrode was prepared by mixing the graphite composite negative active material, CMC, SRR and SP (the mass ratio of the graphite composite negative active material, CMC, SRR and SP was 95:1.5:2.5:1), and the button cell was assembled with lithium sheet, electrolyte and separator in an argon glove box with water content less than 0.1 ppm. The separator was celegard 2400, and the electrolyte was a solution of LiPF6. In the electrolyte, the concentration of LiPF6 was 1 mol / L, and the solvent was a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) obtained by mixing them in a weight ratio of 1:1.

[0075] ​​The prepared button cell was tested by a blue tester to test the performance of the button cell, and the test conditions were as follows: 0.1C rate charge-discharge, voltage range was 0.05-2V, stopped after 3 cycles, then tested the discharge capacity under 1C condition, calculated the rate performance of 1C / 0.1C, cycle performance (25±3℃, 0.2C / 0.2C, 100 weeks) and low temperature capacity retention rate (-20℃ capacity / 25℃ capacity). The test results are shown in Table 2.

[0076] Table 2 Button cell test

[0077]

[0078] As can be seen from Table 2, the discharge capacity, initial efficiency and low temperature performance of the button cell prepared by using the graphite composite negative electrode material of Examples 1-3 are obviously higher than those of Comparative Examples 1-2. The experimental results show that the graphite composite active material of the application can make the battery have good discharge capacity and initial efficiency, low temperature performance, and the reason is that the graphite composite active material of Examples 1-3 has a high diffusion coefficient, which improves the low temperature performance.

[0079] 4. Performance test of soft package battery

[0080] The graphite composite negative electrode active material prepared in each case was used as a negative electrode active material to prepare a negative electrode (the mass ratio of active material, CMC, SRR and SP was 95:1.5:2.5:1, and a positive electrode (the mass ratio of active material, PVDF and SP was 95:5:5) was prepared with a positive electrode active material ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2), electrolyte and separator to assemble a 5Ah soft package battery.

[0081] Among them, the separator was celegard 2400, and the electrolyte was LiPF6 solution (the solvent was a mixed solution of EC and DEC in a volume ratio of 1:1, and the concentration of LiPF6 was 1.1 mol / L). The prepared soft package battery was tested for HPPC rate performance;

[0082] HPPC rate performance: charging with 3C pulse, discharging with 4C pulse, and testing the charging DCR under different SOC (5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%) conditions, and the test results are shown in Table 3.

[0083] Table 3 Performance test of soft package battery

[0084]

[0085] As can be seen from Table 3, the DCR of the soft-pack batteries of Examples 1 to 3 prepared using the obtained graphite composite is significantly lower than that of Comparative Examples 1 to 2.

[0086] The above only is the preferred embodiment of the present application, and does not limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. Graphite composite negative electrode active material, characterized by, The coating layer includes a polymer, a fluorine-containing organic lithium compound, and porous carbon particles. The coating layer includes a polymer, a fluorine-containing organic lithium compound, and porous carbon particles. The fluorine-containing organic lithium compound has a structure formula as follows: ； In the formula, R is a hydrocarbon group containing a F substituent. The polymer includes one or more of an epoxy water-based resin, a polyurethane resin, a water-soluble phenolic resin, and a water-soluble polyester resin. The preparation method of the porous carbon particles includes the following steps: mixing a carbon source, a coupling agent, an organic template, and an organic lithium compound for pre-reaction, and carbonization treatment to obtain the porous carbon particles. The coupling agent is a titanium-based coupling agent.

2. The graphite composite negative electrode active material according to claim 1, characterized in that, The R is a C1-C3 alkyl group substituted by fluorine.

3. The graphite composite negative electrode active material according to claim 2, characterized in that, The R is a C1-C3 alkyl group substituted by fluorine.

4. The graphite composite negative electrode active material according to claim 1, characterized by The mass ratio of the porous carbon particles, the polymer, the fluorine-containing organic lithium compound, and the graphite is 1-10:1-15:0.5-10:

100.

5. The graphite composite negative electrode active material according to claim 4, characterized in that, The mass ratio of the porous carbon particles, the polymer, the fluorine-containing organic lithium compound, and the graphite is 3-5:5-10:0.5-6:

100.

6. The graphite composite negative electrode active material according to claim 1, characterized in that, The mass ratio of the carbon source, the coupling agent, the organic template, and the organic lithium compound is 100:1-5:1-5:1-5.

7. The graphite composite negative electrode active material according to claim 1, characterized in that, The carbon source includes one or more of sucrose, glucose, beta-dextrin, or lactose. The titanium-based coupling agent includes one or more of isopropyl tris(dioctyl pyrophosphato) titanate, tetraisopropyl bis(dioctyl phosphito) titanate, and bis(dioctyl pyrophosphato) ethylene titanate. The organic template includes one or more of polystyrene microspheres, sodium laurate, and polyvinylpyrrolidone. The organic lithium compound is one or more of lithium stearate, lithium octadecanoate, lithium acetate, lithium acetate, lithium benzoate, lithium oxalate, and lithium oxalate. The pre-reaction is performed in the presence of an organic solvent. The organic solvent includes one or more of cyclohexane, n-hexane, carbon tetrachloride, and N-methyl pyrrolidone.

8. The graphite composite negative electrode active material according to claim 1, characterized in that, The pre-reaction is performed at a temperature of 25-150°C for 1-6 hours.

9. The graphite composite negative electrode active material according to claim 8, characterized in that, The pre-reaction is performed at a temperature of 50-120°C.

10. The method of producing a graphite composite negative electrode active material according to any one of claims 1 to 9, characterized by, The method includes the following steps: The porous carbon particles, the polymer, the fluorine-containing organic lithium compound, and the graphite are mixed in a liquid phase, dried, and then obtained as a graphite composite negative electrode active material.

11. The graphite composite negative electrode active material of any one of claims 1-9 or prepared by the method of claim 10, for use in a lithium ion battery.

Images