Graphite composite material, method for preparing the same and use thereof

Abstract

This invention relates to the field of lithium-ion battery material preparation technology, specifically to a graphite composite material, its preparation method, and its application. The invention first synthesizes and coats titanium niobate on the graphite surface in situ using an organic niobium source and an organic titanium source via chemical deposition. Simultaneously, aluminum hydroxide is obtained in situ through the reaction of an organic base with an aluminum-based coupling agent. Subsequent carbonization treatment yields a porous alumina-doped titanium niobate-coated graphite composite material. Finally, a lithium titanium niobate and lithium aluminate dual-coated graphite composite material with good fast-charging performance, high initial efficiency, and high energy density is prepared through a chemical reaction between an organic lithium salt and the porous alumina-doped titanium niobate-coated graphite composite material, followed by sintering.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery material preparation technology, specifically to a graphite composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of lithium-ion battery technology, battery energy density has been greatly improved. Meanwhile, the market demand for shorter charging times is constantly increasing, requiring the anode materials used in lithium-ion batteries to possess fast-charging performance while also maintaining high energy density and high-temperature performance. The fast-charging performance of a battery primarily depends on the fast-charging capability of its anode material. Under charging conditions, the anode, as the lithium-ion acceptor, needs to be able to rapidly accept a large number of lithium-ions for insertion; otherwise, during fast charging, lithium ions will deposit and precipitate on the anode surface, forming lithium dendrites, which may puncture the separator, causing an internal short circuit and posing a safety hazard.

[0003] Currently, graphite is the most commonly used material for lithium battery anodes. The main measures to improve the fast-charging performance of graphite anode materials are: 1) coating the graphite surface with soft or hard carbon. However, soft / hard carbon itself has defects such as low specific capacity, low initial efficiency, and low compaction density. Coating the graphite surface will limit the initial efficiency and specific capacity of the material; 2) doping the graphite anode material with high specific capacity metal oxides or non-metal oxides (such as iron oxide or silicon oxide materials). However, there is a defect of large expansion when fully charged, which leads to a serious decline in the cycle performance of the material; 3) coating the graphite surface with inorganic lithium salts to improve the ionic conductivity of the material, thereby improving the fast-charging performance of the material. However, there are problems such as poor coating uniformity and limited improvement.

[0004] For example, existing technologies disclose a fast-charging graphite composite material and its preparation method, which mainly uses particle injection to deposit inorganic lithium salts on its surface. Although the fast-charging performance is improved to a certain extent, there are defects such as contact deviation between inorganic lithium salt and core, direct contact between inorganic lithium salt and electrolyte leading to more side reactions, reduced first-time efficiency and gas generation. Moreover, using a single lithium salt for coating has limited improvement on the material's fast-charging performance and first-time efficiency.

[0005] Therefore, existing graphite anode materials still need improvement. How to improve the electrochemical performance of graphite anode materials, especially fast charging performance and first-time efficiency, remains an urgent technical problem to be solved. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor electrochemical performance of existing carbon anode materials, thereby providing a graphite composite material, its preparation method and application to solve the above problem.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a graphite composite material, comprising:

[0009] A porous alumina-doped titanium niobate-coated graphite material was obtained by mixing graphite, organic niobium source solution, organic titanium source solution, organic base, and aluminum-based coupling agent for co-deposition reaction, followed by solid-liquid separation and carbonization treatment.

[0010] A graphite composite material was obtained by mixing porous alumina-doped titanium niobate-coated graphite material with an organic lithium salt, heating and reacting it in a liquid environment, and then performing solid-liquid separation and sintering.

[0011] Preferably, the mass ratio of the graphite, organoniobium source solution, organotitanium source solution, organic base, and aluminum-based coupling agent is 100:(100-500):(100-500):(10-30):(1-5);

[0012] And / or, the mass ratio of the organic niobium source to the solvent in the organic niobium source solution is (10-30):500;

[0013] And / or, the mass ratio of the organic titanium source to the solvent in the organic titanium source solution is (10-30):500.

[0014] Preferably, the organic niobium source solution further includes a first dispersant; optionally, the mass ratio of the first dispersant to the solvent in the organic niobium source solution is (1-5):500; optionally, the first dispersant includes at least one of polyvinylpyrrolidone, polyacrylonitrile, and sodium dodecyl sulfonate.

[0015] And / or, the organic titanium source solution further includes a second dispersant; optionally, the mass ratio of the second dispersant to the solvent in the organic titanium source solution is (1-5):500; optionally, the second dispersant includes at least one of polyvinylpyrrolidone, polyacrylonitrile, and sodium dodecyl sulfonate.

[0016] Preferably, the mass ratio of the porous alumina-doped titanium niobate-coated graphite material to the organic lithium salt is 100:(5-15).

[0017] Preferably, the mixing process of the porous alumina-doped titanium niobate-coated graphite material and the organic lithium salt includes: mixing the organic lithium salt with a solvent to obtain a lithium-containing solution; adding a third dispersant and the porous alumina-doped titanium niobate-coated graphite material to the lithium-containing solution and mixing them evenly;

[0018] Optionally, the mass percentage of the organic lithium salt in the lithium-containing solution is 1-10 wt%.

[0019] Optionally, the mass ratio of the third dispersant to the porous alumina-doped titanium niobate-coated graphite material is (1-5):100;

[0020] Optionally, the solvent in the lithium-containing solution includes N-methylpyrrolidone;

[0021] Optionally, the third dispersant includes polyvinyl alcohol.

[0022] Preferably, the temperature of the co-deposition reaction is 150-250℃; the duration of the co-deposition reaction is 2-12 hours.

[0023] And / or, the carbonization temperature is 500-1000℃; the carbonization duration is 1-6h;

[0024] And / or, the temperature of the heating reaction is 50-150°C; the duration of the heating reaction is 1-6 hours;

[0025] And / or, the sintering temperature is 500-900℃; the sintering time is 1-6h.

[0026] Preferably, the organic niobium source includes at least one of niobium ethanol, niobium oxalate, and ammonium niobium oxalate;

[0027] And / or, the solvent in the organic niobium source solution includes an organic alcohol; optionally, the organic alcohol includes at least one of ethanol, isopropanol, and glycerol;

[0028] And / or, the solvent in the organic titanium source solution includes an organic alcohol; optionally, the organic alcohol includes at least one of ethanol, isopropanol, and glycerol;

[0029] And / or, the organic titanium source includes at least one of titanium tetraisopropoxide, titanium tetrafluoride, and tetrabutyl titanate;

[0030] And / or, the organic base includes at least one of pyridine, imidazole, indole, pyrrole and their derivatives;

[0031] And / or, the aluminum-based coupling agent includes an aluminate coupling agent; optionally, the aluminate coupling agent includes at least one of aluminum triacetylacetonate, diisopropyl aluminate, isopropyl distearate, diisopropyl aluminate, diisopropyl acetylacetonate, diisopropyl aluminate complex, and isopropyldistearate.

[0032] And / or, the organic lithium salt includes at least one of lithium acetate, lithium pyruvate, and lithium stearate;

[0033] And / or, the solid-liquid separation includes filtration.

[0034] The present invention also provides a graphite composite material, which is prepared by the above-described method for preparing graphite composite materials.

[0035] The present invention also provides a negative electrode material, including the above-mentioned graphite composite material.

[0036] The present invention also provides a secondary battery comprising the above-described negative electrode material.

[0037] The present invention also provides an electrical device, including the aforementioned secondary battery.

[0038] The technical solution of this invention has the following advantages:

[0039] The method for preparing graphite composite materials provided by this invention includes: mixing graphite, an organic niobium source solution, an organic titanium source solution, an organic base, and an aluminum-based coupling agent for co-deposition reaction, followed by solid-liquid separation and carbonization to obtain a porous alumina-doped titanium niobate-coated graphite material; mixing the porous alumina-doped titanium niobate-coated graphite material with an organic lithium salt, heating and reacting in a liquid phase environment, followed by solid-liquid separation and sintering to obtain the graphite composite material. This invention first synthesizes and coats titanium niobate on the graphite surface in situ using an organic niobium source and an organic titanium source through chemical deposition; simultaneously, aluminum hydroxide is obtained in situ through the reaction of an organic base with an aluminum-based coupling agent; then, a porous alumina-doped titanium niobate-coated graphite composite material is obtained through subsequent carbonization; finally, a lithium titanium niobate and lithium aluminate double-coated graphite composite material with good fast-charging performance, high initial efficiency, high energy density, and good safety performance is prepared through a chemical reaction between the organic lithium salt and the porous alumina-doped titanium niobate-coated graphite composite material, followed by sintering. In the graphite composite material prepared by this invention, titanium lithium niobate has the characteristics of large interlayer spacing, moderate specific capacity, high ion diffusion rate and high voltage plateau. While porous lithium aluminate itself has no specific capacity, its interaction with titanium lithium niobate significantly improves the initial efficiency, rate performance and safety performance of the coating layer.

[0040] Furthermore, this invention coats organic niobium and organic titanium sources onto the graphite surface via chemical deposition and carbonization, offering advantages such as good uniformity, mild reaction conditions, and high reaction efficiency. Moreover, the carbonization of the organic compounds generates a porous structure, thereby improving the material's liquid retention properties and reducing expansion. Simultaneously, the organic base reacts with the aluminum-based coupling agent under alkaline conditions (Al... 3+ +OH - =Al(OH)3), Al(OH)3 generates porous alumina during subsequent high-temperature carbonization and is incorporated into the titanium niobate material. Its porous structure also enhances the liquid retention performance of the material. Secondly, the aluminum-based coupling agent in this invention, while reacting with organic bases, also provides a coupling effect to enhance the bonding force between the niobium source, titanium source, and graphite material, thereby further improving the initial efficiency and safety performance. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a SEM image of the graphite composite material prepared in Example 1 of this invention. Detailed Implementation

[0043] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0044] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0045] Example 1

[0046] This embodiment provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0047] 1) Weigh 20g of niobium ethanol and 3g of polyvinylpyrrolidone (CAS No.: 9003-39-8; Manufacturer: Boai Xinkaiyuan Pharmaceutical Co., Ltd.; Model: K17; Molecular weight: 10,000-16,000) and add them to 500g of ethanol organic solvent to disperse evenly and prepare an organic niobium source solution;

[0048] 2) Weigh 20g of tetraisopropoxide titanium and 3g of polyvinylpyrrolidone and add them to 500g of ethanol organic solvent to disperse evenly and prepare an organic titanium source solution;

[0049] 3) Mix 100g of artificial graphite, 300g of the organic niobium source solution from step 1), 300g of the organic titanium source solution from step 2), 20g of pyridine, and 3g of aluminum triacetylacetonate and disperse them evenly. Then, perform a co-deposition reaction at 200℃ for 7h. After filtration, the resulting filter residue is carbonized at 800℃ for 3h to obtain porous alumina-doped titanium niobate-coated graphite material.

[0050] 4) Weigh 10g of lithium acetate and add it to N-methylpyrrolidone to prepare a 5wt% lithium-containing solution. Then add 3g of polyvinyl alcohol (CAS: 9002-89-5; manufacturer: Sichuan Laitejuxin Pharmaceutical Excipients Co., Ltd.; model: 8805; molecular weight: 10,000-100,000) and 100g of the porous alumina-doped titanium niobate-coated graphite material from step 3) and disperse it evenly. Then react at 100℃ for 3h, filter, and sinter the resulting filter residue at 600℃ for 3h to obtain a double-coated graphite composite material of lithium titanium niobate and lithium aluminate.

[0051] Example 2

[0052] This embodiment provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0053] 1) Weigh 10g of niobium oxalate and 1g of polyacrylonitrile (CAS: 25014-41-9; manufacturer: Wuhan Rongcan Biotechnology Co., Ltd.; model: 89; molecular weight: 15,000) and add them to 500g of isopropanol organic solvent to disperse evenly and prepare an organic niobium source solution.

[0054] 2) Weigh 10g of titanium tetrafluoride and 1g of polyacrylonitrile and add them to 500g of isopropanol organic solvent to disperse evenly and prepare an organic titanium source solution.

[0055] 3) Mix and disperse 100g of artificial graphite, 100g of the organic niobium source solution from step 1), 100g of the organic titanium source solution from step 2), 10g of imidazole, and 1g of (acetylacetone) diisopropyl aluminate evenly. Then, perform a co-deposition reaction at 150℃ for 12h. After filtration, the resulting filter residue is carbonized at 500℃ for 6h to obtain porous alumina-doped titanium niobate-coated graphite material.

[0056] 4) Weigh 5g of lithium pyruvate and add it to N-methylpyrrolidone to prepare a 1wt% lithium-containing solution. Then add 1g of polyvinyl alcohol and 100g of the porous alumina-doped titanium niobate-coated graphite material from step 3) and disperse it evenly. Then react at 50℃ for 6h, filter, and sinter the resulting filter residue at 500℃ for 6h to obtain a double-coated graphite composite material of lithium titanium niobate and lithium aluminate.

[0057] Example 3

[0058] This embodiment provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0059] 1) Weigh 30g of ammonium niobate oxalate and 5g of sodium dodecyl sulfate and add them to 500g of glycerol organic solvent to disperse evenly and prepare an organic niobium source solution;

[0060] 2) Weigh 30g of tetrabutyl titanate and 5g of sodium dodecyl sulfonate and add them to 500g of isopropanol organic solvent to disperse evenly and prepare an organic titanium source solution;

[0061] 3) Mix and disperse 100g of artificial graphite, 500g of the organic niobium source solution from step 1), 500g of the organic titanium source solution from step 2), 30g of indole, and 5g of isopropyl distearate aluminate. Then, perform a co-deposition reaction at 250℃ for 2h. After filtration, the resulting filter residue is carbonized at 1000℃ for 1h to obtain porous alumina-doped titanium niobate-coated graphite material.

[0062] 4) Weigh 15g of lithium stearate and add it to N-methylpyrrolidone to prepare a 10wt% lithium-containing solution. Then add 5g of polyvinyl alcohol and 100g of the porous alumina-doped titanium niobate-coated graphite material from step 3) and disperse it evenly. Then react at 150℃ for 1h, filter, and sinter the resulting filter residue at 900℃ for 1h to obtain a double-coated graphite composite material of lithium titanium niobate and lithium aluminate.

[0063] Example 4

[0064] This embodiment provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0065] 1) Weigh 15g of niobium ethanol and 2g of polyvinylpyrrolidone and add them to 500g of ethanol organic solvent to disperse evenly and prepare an organic niobium source solution;

[0066] 2) Weigh 15g of tetraisopropoxide titanium and 2g of polyvinylpyrrolidone and add them to 500g of ethanol organic solvent to disperse evenly and prepare an organic titanium source solution.

[0067] 3) Mix and disperse 100g of artificial graphite, 200g of the organic niobium source solution from step 1), 200g of the organic titanium source solution from step 2), 15g of pyrrole, and 2g of isopropoxydistearate oxyaluminate. Then, perform a co-deposition reaction at 180℃ for 10h, and then filter the mixture. Carbonize the resulting filter residue at 600℃ for 2h to obtain porous alumina-doped titanium niobate-coated graphite material.

[0068] 4) Weigh 8g of lithium acetate and add it to N-methylpyrrolidone to prepare a 3wt% lithium-containing solution. Then add 2g of polyvinyl alcohol and 100g of the porous alumina-doped titanium niobate-coated graphite material from step 3) and disperse it evenly. Then react at 75℃ for 2h, filter, and sinter the resulting filter residue at 550℃ for 2h to obtain a double-coated graphite composite material of lithium titanium niobate and lithium aluminate.

[0069] Example 5

[0070] This embodiment provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0071] 1) Weigh 25g of niobium ethanol and 4g of polyvinylpyrrolidone and add them to 500g of ethanol organic solvent to disperse evenly and prepare an organic niobium source solution;

[0072] 2) Weigh 25g of tetraisopropoxide titanium and 4g of polyvinylpyrrolidone and add them to 500g of ethanol organic solvent to disperse evenly and prepare an organic titanium source solution.

[0073] 3) Mix and disperse 100g of artificial graphite, 400g of the organic niobium source solution from step 1), 400g of the organic titanium source solution from step 2), 25g of pyridine, and 4g of diisopropoxyacetoacetate oleate aluminate. Then, perform a co-deposition reaction at 230℃ for 5h. After filtration, the resulting filter residue is carbonized at 900℃ for 4h to obtain porous alumina-doped titanium niobate-coated graphite material.

[0074] 4) Weigh 13g of lithium acetate and add it to N-methylpyrrolidone to prepare an 8wt% lithium-containing solution. Then add 4g of polyvinyl alcohol and 100g of the porous alumina-doped titanium niobate-coated graphite material from step 3) and disperse it evenly. Then react at 125℃ for 4h, filter, and sinter the resulting filter residue at 800℃ for 4h to obtain a double-coated graphite composite material of lithium titanium niobate and lithium aluminate.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that step 4) is omitted, and the porous alumina-doped titanium niobate-coated graphite material obtained in step 3) is directly used as the negative electrode material.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0079] 10g of lithium acetate was added to 200g of N-methylpyrrolidone to prepare a 5wt% solution. Then, 3g of polyvinyl alcohol dispersant and 100g of graphite material were added and dispersed evenly. The mixture was reacted at 800℃ for 3h, filtered, and the resulting filter residue was sintered at 600℃ for 3h to obtain a lithium-doped amorphous carbon-coated graphite composite material.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 1 is that niobium ethanol, titanium tetraisopropoxide, and pyridine are replaced with niobium oxide, titanium oxide, and deionized water, while other conditions are the same as in Example 1.

[0082] Comparative Example 4

[0083] This comparative example provides a method for preparing graphite composite materials, the specific steps of which are as follows:

[0084] 1) Mix 100g of artificial graphite, 11.47g of niobium ethanol, 11.47g of titanium tetraisopropoxide, 3.44g of polyvinylpyrrolidone, 574g of ethanol, 20g of pyridine, and 3g of aluminum triacetylacetonate and disperse them evenly for co-deposition reaction. After filtration, the resulting filter residue is carbonized at 800℃ for 3h to obtain porous alumina-doped titanium niobate-coated graphite material.

[0085] 2) Weigh 10g of lithium acetate and add it to 200g of N-methylpyrrolidone to prepare a 5wt% lithium-containing solution. Then add 3g of polyvinyl alcohol and 100g of the porous alumina-doped titanium niobate-coated graphite material from step 1) and disperse it evenly. Then react at 100℃ for 3h, filter, and sinter the resulting filter residue at 600℃ for 3h to obtain a double-coated graphite composite material of lithium titanium niobate and lithium aluminate.

[0086] Comparative Example 5

[0087] The difference between this comparative example and Example 1 is that the organic base (pyridine) is replaced with an equal mass of inorganic base (sodium carbonate), while the other conditions are the same as in Example 1.

[0088] Comparative Example 6

[0089] The difference between this comparative example and Example 1 is that the aluminate coupling agent (aluminum triacetylacetonate) is replaced with an equal mass of titanate coupling agent (titanium acetylacetonate), while the other conditions are the same as in Example 1.

[0090] Test case

[0091] (1) SEM testing

[0092] The lithium titanium niobate and lithium aluminate double-coated graphite composite material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the obtained composite material is granular with an average particle size D50 of about 10 μm and a uniform size distribution.

[0093] (2) Diffusion coefficient and OI value test

[0094] The diffusion coefficient of the graphite composite powder materials prepared by the GITT test and the comparative example was tested, and the OI value of the powder materials was tested by XRD. The test results are shown in Table 1.

[0095] (3) Button cell battery test

[0096] The graphite composite materials prepared in the examples and comparative examples were assembled into coin cells according to the following methods:

[0097] Add binder, conductive agent, and solvent to the negative electrode material, stir and mix evenly to prepare a negative electrode slurry, and then coat the negative electrode slurry onto copper foil (single-sided areal density 6 mg / cm²). 2 The material is dried, rolled, and cut to obtain the negative electrode sheet. The binder is LA132 binder, the conductive agent is SP conductive agent, and the solvent is double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA132 binder, and double-distilled water is 95:1:4:220. Using lithium metal sheets as the counter electrode, polyethylene propylene (PEP) as the separator, and LiPF6 / EC+DEC (LiPF6 concentration 1.1 mol / L, EC and DEC volume ratio 1:1) as the electrolyte, the CR2032 coin cell is assembled in an argon-filled glove box.

[0098] The fabricated button cells were installed on a Wuhan Landian CT2001A battery tester and charged and discharged at a rate of 0.1C, with a charging and discharging voltage range of 0.005V to 2.0V. The initial discharge capacity and initial discharge efficiency were measured. The 2C rate discharge capacity was also tested, and the rate performance (2C / 0.1C) and cycle performance (0.2C / 0.2C, 100 cycles) were calculated. The test results are shown in Table 1.

[0099] Table 1

[0100]

[0101] As shown in Table 1, the discharge capacity, initial efficiency, and diffusion coefficient of the lithium titanium niobate and lithium aluminate-coated graphite composite materials prepared in Examples 1-5 are significantly higher than those in Comparative Examples 1-6. This is likely because the coating layer contains lithium aluminate, which itself has a high specific capacity and provides lithium ions during the initial charge-discharge process, reducing irreversible capacity and improving initial efficiency. Furthermore, the large interlayer spacing of niobate and titanium enhances the diffusion coefficient. Simultaneously, lithium aluminate exhibits inertness to the electrolyte, reducing irreversible capacity loss and improving initial efficiency.

[0102] (3) Pouch Battery Testing

[0103] Anodes were prepared using lithium titanium niobate and lithium aluminate-coated graphite composite materials prepared in Examples 1-5 and Comparative Examples 1-6, respectively, and ternary materials (LiMn) were used. 1 / 3 Co 1 / 3 Ni 1 / 3 A 2Ah pouch cell was prepared using O2 as the positive electrode, LiPF6 (solvent: EC+DEC (volume ratio 1:1), concentration 1.1mol / L) as the electrolyte, and Celegard 2400 as the separator.

[0104] During the preparation of the negative electrode, a binder, conductive agent, and solvent are added to the negative electrode material and stirred to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto copper foil (the single-sided areal density of the negative electrode is 9.5 mg / cm³). 2 Drying and roller pressing (compacted density 1.6 g / cm³) 3 The negative electrode sheet is prepared by cutting the material. The binder is LA136D binder, the conductive agent is SP conductive agent, and the solvent is double-distilled water. The weight ratio of the negative electrode material, SP conductive agent, LA136D binder and double-distilled water is 95:1:4:250.

[0105] In the preparation of the positive electrode, a binder solution is prepared, followed by the addition of a conductive agent and the positive electrode material. The mixture is stirred and stirred until homogeneous to form a positive electrode slurry. The positive electrode slurry is then coated onto aluminum foil (single-sided areal density 20 mg / cm²). 2 Drying, rolling (compacted density 3.4 g / cm³) 3 The positive electrode sheet is prepared by cutting and shaping, with PVDF as the binder, SP as the conductive agent, and N-methylpyrrolidone as the solvent. The weight ratio of the positive electrode material, conductive agent, binder, and solvent is 97:1:2:140.

[0106] 3.1 Cyclic performance:

[0107] The cycle performance of the battery was tested at a charge / discharge rate of 1C / 1C and a voltage range of 2.8V-4.2V at a temperature of 25±3℃. The test results are shown in Table 2.

[0108] 3.2x performance:

[0109] The battery was charged to 4.2V at constant current rates of 1C, 2C, 3C, or 5C, and then charged to 100% SOC using constant voltage mode (0.1C to 4.2V, 3h). The constant current ratio was then calculated as constant current capacity / (constant current capacity + constant voltage capacity). The test results are shown in Table 2.

[0110] Table 2

[0111]

[0112] A comparison of the cycle performance and fast-charging performance of the pouch cells prepared using the negative electrode materials obtained in Table 2 shows that the cycle performance and fast-charging performance (constant current ratio) of the cells in the example are significantly better than those in the comparative example. This is because the materials in the example have a lower OI value and an excellent diffusion coefficient (as shown in Table 1), which improves the fast-charging performance of the materials; simultaneously, the outer coating of lithium niobate titanium has an excellent large interlayer spacing, reducing expansion and improving the cycle performance of the battery.

[0113] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a graphite composite material, characterized in that, include: A porous alumina-doped titanium niobate-coated graphite material was obtained by mixing graphite, organic niobium source solution, organic titanium source solution, organic base, and aluminum-based coupling agent for co-deposition reaction, followed by solid-liquid separation and carbonization treatment. A graphite composite material was obtained by mixing porous alumina-doped titanium niobate-coated graphite with an organic lithium salt, heating the mixture in a liquid environment, and then performing solid-liquid separation and sintering. The mass ratio of the graphite, organic niobium source solution, organic titanium source solution, organic base, and aluminum-based coupling agent is 100:(100-500):(100-500):(10-30):(1-5); The carbonization treatment temperature is 500-1000℃; The temperature of the heating reaction is 50-150℃.

2. The method for preparing graphite composite material according to claim 1, characterized in that, The mass ratio of organic niobium source to solvent in the organic niobium source solution is (10-30):500; And / or, the mass ratio of the organic titanium source to the solvent in the organic titanium source solution is (10-30):

500.

3. The method for preparing the graphite composite material according to claim 1, characterized in that, The organic niobium source solution also includes a first dispersant; And / or, the organic titanium source solution also includes a second dispersant.

4. The method for preparing the graphite composite material according to claim 3, characterized in that, The mass ratio of the first dispersant to the solvent in the organic niobium source solution is (1-5):500; And / or, the first dispersant comprises at least one of polyvinylpyrrolidone, polyacrylonitrile, and sodium dodecyl sulfonate; And / or, the mass ratio of the second dispersant to the solvent in the organic titanium source solution is (1-5):500; And / or, the second dispersant includes at least one of polyvinylpyrrolidone, polyacrylonitrile, and sodium dodecyl sulfonate.

5. The method for preparing graphite composite material according to claim 1, characterized in that, The mass ratio of the porous alumina-doped titanium niobate-coated graphite material to the organic lithium salt is 100:(5-15).

6. The method for preparing graphite composite material according to claim 5, characterized in that, The mixing process of the porous alumina-doped titanium niobate-coated graphite material with the organic lithium salt includes: mixing the organic lithium salt with a solvent to obtain a lithium-containing solution; adding a third dispersant and the porous alumina-doped titanium niobate-coated graphite material to the lithium-containing solution and mixing them evenly.

7. The method for preparing the graphite composite material according to claim 6, characterized in that, The mass percentage of organic lithium salt in the lithium-containing solution is 1-10 wt%. And / or, the mass ratio of the third dispersant to the porous alumina-doped titanium niobate-coated graphite material is (1-5):100; And / or, the solvent in the lithium-containing solution includes N-methylpyrrolidone; And / or, the third dispersant includes polyvinyl alcohol.

8. The method for preparing graphite composite material according to claim 1, characterized in that, The temperature of the co-deposition reaction is 150-250℃; the duration of the co-deposition reaction is 2-12 hours. And / or, the carbonization treatment lasts for 1-6 hours; And / or, the duration of the heating reaction is 1-6 hours; And / or, the sintering temperature is 500-900℃; the sintering time is 1-6h.

9. The method for preparing the graphite composite material according to any one of claims 1-8, characterized in that, The organic niobium source includes at least one of niobium ethanol, niobium oxalate, and ammonium niobium oxalate. And / or, the solvent in the organic niobium source solution includes an organic alcohol; And / or, the solvent in the organic titanium source solution includes organic alcohols; And / or, the organic titanium source includes at least one of titanium tetraisopropoxide, titanium tetrafluoride, and tetrabutyl titanate; And / or, the organic base includes at least one of pyridine, imidazole, indole, pyrrole and their derivatives; And / or, the aluminum-based coupling agent includes an aluminate coupling agent; And / or, the organic lithium salt includes at least one of lithium acetate, lithium pyruvate, and lithium stearate; And / or, the solid-liquid separation includes filtration.

10. The method for preparing the graphite composite material according to claim 9, characterized in that, The organic alcohol includes at least one of ethanol, isopropanol, and glycerol; And / or, the aluminate coupling agent includes at least one of aluminum triacetylacetonate, diisopropyl aluminate (acetylacetonate), isopropyl distearate aluminate, diisopropyl aluminate (ethyl acetoacetate), diisopropyl aluminate acetylacetonate complex, and isopropyldistearate aluminate.

11. A graphite composite material, characterized in that, It is prepared by the method for preparing graphite composite material according to any one of claims 1-10.

12. A negative electrode material, characterized in that, Including the graphite composite material as described in claim 11.

13. A secondary battery, characterized in that, Includes the negative electrode material as described in claim 12.

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