A method for preparing in-situ carbon-coated lithium-ion battery materials

Abstract

This invention relates to an in-situ carbon-coated lithium-ion battery material and its preparation method. Belonging to the field of lithium-ion battery materials, the invention involves drying an electrode sheet to a thickness of 0.01–0.5 cm; obtaining a carbon source by dissolving or dispersing polyvinylpyrrolidone, polyoxymethylene, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, and carbon quantum dot powder in a solvent; immersing the dried electrode sheet in different carbon sources for further drying; placing the carbon-coated electrode sheet in an atmosphere furnace and heating it to 300–600°C at 1–5°C / min for 1–24 hours for thermal reduction and carbonization, forming a uniform and stable carbon coating layer on the material surface. After cooling to room temperature, the in-situ carbon-coated composite electrode is obtained. This invention employs a direct calcination electrode sheet process to form a uniform and stable carbon coating layer on the material surface, enhancing the material's conductivity, suppressing volume expansion, and improving the electrode material's lithium storage capacity and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials, and in particular to an in-situ carbon-coated lithium-ion battery material and its preparation method. Background Technology

[0002] Lithium-ion batteries (LIBs) possess advantages such as high energy density, long lifespan, and low self-discharge rate, making them one of the most attractive energy storage devices currently available. They are widely used in portable electronic products such as mobile phones, laptops, and digital cameras. They are also considered the preferred power source for electric vehicles and stationary energy storage systems. Graphite anodes have been widely used as anodes in commercially available lithium-ion batteries, but their theoretical specific capacity is relatively low (372 mAh g⁻¹), which cannot meet the market demand for future large-scale energy storage devices. Therefore, the development of novel lithium-ion battery anode materials with higher specific capacity and higher power density remains an urgent need. However, the unavoidable electrolyte side reactions and volume expansion effects of anode materials prevent the formation of a stable SEI film, further leading to a significant consumption of active material and a sharp decline in battery capacity.

[0003] Meanwhile, numerous studies have shown that coating with conductive carbon materials can effectively accommodate volume fluctuations during charging and discharging, mitigate side reactions between the electrolyte and active materials, maintain the stability of the electrode structure, and thus improve the cycle life of lithium-ion batteries. Currently, various amorphous carbon materials, including hollow nanostructured carbon, carbon nanospheres, carbon nanofibers, carbon nanosheets, porous carbon, hard carbon, graphene, and heteroatom-doped carbon materials, are the most popular coating materials.

[0004] CN117525326A discloses a method for preparing carbon-coated lithium-ion battery cathode materials, employing chemical vapor deposition (CVD) to react a carbon source with lithium-ion battery cathode materials in a reaction vessel to obtain the coating material. CN115763722A discloses a multi-dimensional, multi-scale carbon-coated lithium-ion battery cathode material and its preparation method, primarily using a grinding method. Resin and graphite are mixed, then exfoliated using a three-roll differential mill. After multiple cleanings, catalysts, dopants, and raw materials are added and mixed again using a three-roll differential mill, followed by freeze-drying and heat treatment to obtain the battery cathode material. CN108682828A discloses a method for preparing nitrogen-doped carbon-coated lithium-ion battery cathode materials. Using melamine as the nitrogen source, organic acid as the carbon source, and modified graphene as the conductive bridge, melamine, organic acid, and modified graphene are mixed evenly in a solvent, and then the positive electrode material is added, mixed evenly, and dried. The dried mixture is ground and sieved, then transferred to a rotary kiln, heated at 100–500°C under an inert atmosphere, and then carbonized at high temperature to obtain a nitrogen-doped carbon-coated positive electrode material. CN105742592A discloses a method for preparing a W / W2C / activated carbon-coated lithium-ion battery positive electrode material. The raw materials of the positive electrode material, carbon source, additives, and water are mixed, dispersed by a sand mill, and then spray-dried to obtain a composite precursor, which is then sintered at high temperature under reducing and inert gases.

[0005] Traditional coating methods such as chemical vapor deposition, ball milling, and spray drying require sophisticated production equipment. Therefore, finding a lower-cost coating method that achieves uniform coating results remains an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the above problems, the purpose of this invention is to provide a method for preparing in-situ carbon-coated lithium-ion battery materials.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] A method for preparing an in-situ carbon-coated lithium-ion battery material includes the following steps:

[0009] Step 1: Mix the dried lithium battery electrode material powder, conductive agent and binder in a mass ratio of 8:(0.1~3):(0.1~3) and stir evenly. Then coat the mixture onto a metal foil and dry it to make a lithium battery electrode sheet with a thickness of 0.01~0.5cm.

[0010] Step 2: Immerse the lithium battery electrode sheet obtained in Step 1 in a carbon source solution until the carbon source solution is completely evaporated to obtain an electrode sheet coated with carbon source.

[0011] Step 3: Place the carbon source-coated electrode sheet obtained in Step 2 into an atmosphere furnace, heat it to 300-600°C at a rate of 1-5°C / min, and hold it at that temperature for 1-24 hours for thermal reduction and carbonization. Then cool it to room temperature to form a uniform and stable carbon coating layer on the material surface, thus obtaining an in-situ carbon-coated lithium-ion battery material.

[0012] Furthermore, the lithium battery electrode material powder in step 1 is either lithium battery positive electrode material powder or lithium battery negative electrode material powder. The lithium battery positive electrode material includes any one or more of lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide. The lithium battery negative electrode material includes any one or more of silicon, silicon suboxide, tin, tin dioxide, stannate, manganese dioxide, and vanadate.

[0013] Furthermore, the metal foil in step 1 is either copper foil or aluminum foil. When the lithium battery electrode material is the negative electrode material of the lithium battery, copper foil is selected; when the lithium battery electrode material is the positive electrode material of the lithium battery, aluminum foil is selected.

[0014] Furthermore, the carbon source is any one or more of polyvinylpyrrolidone, polyoxymethylene, polyacrylonitrile, polyvinyl alcohol, and carbon quantum dot powder.

[0015] Furthermore, the solvent of the carbon source solution is any one of ethylene glycol, water, ethanol, and N,N-dimethylformamide.

[0016] Furthermore, the conductive agent includes any one or more of acetylene black, graphene, and carbon nanotubes.

[0017] Furthermore, the adhesive includes any one or more of polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, and styrene-butadiene rubber.

[0018] Furthermore, the mass ratio of the carbon source in the lithium battery electrode material powder and the carbon source solution is 1:(0.01~1).

[0019] Furthermore, the gas introduced into the atmosphere furnace is any one of argon, nitrogen, and an argon / hydrogen mixture.

[0020] An in-situ carbon-coated lithium-ion battery material is prepared by the method described above.

[0021] The beneficial effects of this invention are as follows: This invention uses a solution evaporation method to coat lithium battery electrode sheets with polyvinylpyrrolidone, polyoxymethylene, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, and carbon quantum dot powder as carbon sources. The carbon-coated electrode sheets are then placed in a flowing protective gas and heated for thermal reduction and carbonization, forming a uniform and stable carbon coating layer on the material surface. After cooling to room temperature, the above-mentioned in-situ carbon-coated composite material is obtained. This invention employs a direct calcination electrode sheet process to form a uniform and stable carbon coating layer on the material surface, enhancing the material's conductivity and, to a certain extent, suppressing material volume expansion, thereby improving the lithium storage capacity and cycle stability of the electrode material. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the cycling performance of carbon-coated silica-suboxide composite material;

[0023] Figure 2 This is a schematic diagram of the cycling performance of carbon-coated sodium vanadate composite material. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1:

[0026] (1) Dry silica powder is mixed with acetylene black and polyvinylidene fluoride in a ratio of 8:1:1 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.1 cm.

[0027] (2) Based on the mass ratio of silica powder to carbon quantum dots of 1:1, carbon quantum dot powder is dispersed in ethanol to form a carbon quantum dot ethanol solution.

[0028] (3) Immerse the silicon suboxide electrode sheet coated with carbon source obtained in step (1) in carbon quantum dot ethanol solution until the liquid evaporates completely;

[0029] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 400°C at 1°C / min under an argon atmosphere and kept at that temperature for 2 hours to obtain a silicon-based negative electrode in situ coated with carbon lithium-ion battery composite material.

[0030] Implementation Case 2:

[0031] (1) Dry sodium vanadate is mixed with one of graphene and carboxymethyl cellulose in a ratio of 8:1:1 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.2 cm.

[0032] (2) Based on the mass ratio of sodium vanadate powder to polyvinylpyrrolidone of 1:0.5, polyvinylpyrrolidone is dissolved in ethanol to form a polyvinylpyrrolidone ethanol solution.

[0033] (3) Immerse the sodium vanadate electrode sheet coated with carbon source obtained in step (1) in polyvinylpyrrolidone ethanol solution until the liquid evaporates completely;

[0034] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 500°C at 2°C / min under a nitrogen atmosphere and kept at that temperature for 2 hours to obtain a lithium-ion battery composite material with sodium vanadate in situ coated with carbon.

[0035] Implementation Case 3:

[0036] (1) Dry lithium manganese oxide powder is mixed with carbon nanotubes and polyacrylic acid in a ratio of 8:2:2 and coated on aluminum foil, and then dried to form an electrode sheet with a thickness of 0.05 cm.

[0037] (2) Based on the mass ratio of lithium manganese oxide powder to polyoxymethylene of 1:0.1, polyoxymethylene is dissolved in hot water to form a polyoxymethylene solution.

[0038] (3) Immerse the lithium manganese oxide electrode sheet coated with carbon source obtained in step (1) in polyoxymethylene solution until the liquid evaporates completely;

[0039] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 450°C at 1°C / min under an argon / hydrogen atmosphere and held for 1 hour to obtain a lithium-ion battery composite material with in-situ carbon coating of lithium manganese oxide.

[0040] Implementation Case 4:

[0041] (1) Dry silicon powder is mixed with acetylene black and polyvinylidene fluoride in a ratio of 8:1:1 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.1 cm.

[0042] (2) Based on the mass ratio of silicon powder to polyacrylonitrile of 1:0.5, polyacrylonitrile is dissolved in ethanol to form a polyacrylonitrile ethanol solution.

[0043] (3) Immerse the silicon wafer coated with carbon source obtained in step (1) in polyacrylonitrile ethanol solution until the liquid evaporates completely;

[0044] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 400°C at 5°C / min under an argon atmosphere and kept at that temperature for 1 hour to obtain a silicon-coated carbon lithium-ion battery composite material.

[0045] Implementation Case 5:

[0046] (1) Dry tin powder is mixed with acetylene black and polyvinylidene fluoride in a ratio of 8:1:1 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.1 cm.

[0047] (2) Based on the mass ratio of tin powder to polyacrylonitrile of 1:1, polyacrylonitrile is dissolved in ethanol to form a polyacrylonitrile ethanol solution.

[0048] (3) Immerse the tin electrode sheet coated with carbon source obtained in step (1) in polyacrylonitrile ethanol solution until the liquid evaporates completely;

[0049] (4) The material obtained in step (2) is placed in an atmosphere furnace and heated to 400°C at 5°C / min under an argon atmosphere and held for 1 hour to obtain a lithium-ion battery composite material with tin in situ coated carbon.

[0050] Implementation Case 6:

[0051] (1) Dry tin dioxide powder is mixed with carbon nanotubes and styrene-butadiene rubber in a ratio of 8:3:3 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.07 cm.

[0052] (2) Based on the mass ratio of tin dioxide powder to polyvinyl alcohol of 1:0.1, polyvinyl alcohol is dissolved in N,N-dimethylformamide to form a polyvinyl alcohol solution.

[0053] (3) Immerse the tin dioxide sheet coated with carbon source obtained in step (1) in polyvinyl alcohol solution until the liquid evaporates completely;

[0054] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 600°C at 5°C / min under an argon atmosphere and kept at that temperature for 1 hour to obtain a lithium-ion battery composite material with in-situ carbon coating of tin dioxide.

[0055] Implementation Case 7:

[0056] (1) Dry sodium stannate powder is mixed with acetylene black and carboxymethyl cellulose in a ratio of 8:1:1 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.3 cm.

[0057] (2) Based on the mass ratio of sodium stannate powder to carbon quantum dots of 1:0.1, carbon quantum dots are dispersed in ethanol to form a carbon quantum dot ethanol solution;

[0058] (3) Immerse the sodium stannate electrode sheet coated with carbon source obtained in step (1) in carbon quantum dot ethanol solution until the liquid evaporates completely;

[0059] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 400°C at 5°C / min under an argon atmosphere and kept at that temperature for 2 hours to obtain a lithium-ion battery composite material with sodium stannate in situ coated with carbon.

[0060] Implementation Case 8:

[0061] (1) Dry manganese dioxide powder is mixed with acetylene black and carboxymethyl cellulose in a ratio of 8:1:1 and coated onto copper foil, and then dried to form an electrode sheet with a thickness of 0.4 cm.

[0062] (2) Based on the mass ratio of manganese dioxide powder to carbon quantum dots of 1:1, carbon quantum dots are dispersed in ethanol to form a carbon quantum dot ethanol solution.

[0063] (3) Immerse the manganese dioxide electrode sheet coated with carbon source obtained in step (1) in carbon quantum dot ethanol solution until the liquid evaporates completely;

[0064] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 400°C at 5°C / min under an argon atmosphere and kept at that temperature for 2 hours to obtain a lithium-ion battery composite material with manganese dioxide in situ coated with carbon.

[0065] Implementation Case 9:

[0066] (1) Dry lithium iron phosphate powder is mixed with acetylene black and carboxymethyl cellulose in a ratio of 8:1:1 and coated onto aluminum foil, and then dried to form an electrode sheet with a thickness of 0.1 cm.

[0067] (2) Based on the mass ratio of lithium iron phosphate powder to carbon quantum dots of 1:0.1, carbon quantum dots are dispersed in ethanol to form a carbon quantum dot ethanol solution.

[0068] (3) Soak the manganese dioxide flakes obtained in step (1) in carbon quantum dot ethanol solution until the liquid evaporates completely;

[0069] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 400°C at 5°C / min under an argon atmosphere and kept at that temperature for 2 hours to obtain a lithium-ion battery composite material with in-situ carbon coating of lithium iron phosphate.

[0070] Implementation Case 10:

[0071] (1) Dry lithium cobalt oxide powder is mixed with acetylene black and polyvinylidene fluoride in a ratio of 8:1:1 and coated onto aluminum foil, and then dried to form an electrode sheet with a thickness of 0.1 cm.

[0072] (2) Based on the mass ratio of lithium cobalt oxide powder to polyacrylonitrile of 1:1, polyacrylonitrile is dissolved in ethanol to form a polyacrylonitrile ethanol solution.

[0073] (3) Immerse the lithium cobalt oxide electrode sheet coated with carbon source obtained in step (1) in polyacrylonitrile ethanol solution until the liquid evaporates completely.

[0074] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 400°C at 5°C / min under an argon atmosphere and kept at that temperature for 1 hour to obtain a lithium-ion battery composite material with in-situ carbon coating of lithium cobalt oxide.

[0075] Implementation Case 11:

[0076] (1) Dry lithium nickelate powder is mixed with acetylene black and polyvinylidene fluoride in a ratio of 8:1:1 and coated onto aluminum foil, and then dried to form an electrode sheet with a thickness of 0.1 cm.

[0077] (2) Based on the mass ratio of lithium nickelate powder to carbon quantum dots of 1:0.5, carbon quantum dots are dispersed in ethanol to form a carbon quantum dot ethanol solution;

[0078] (3) Immerse the lithium nickelate electrode sheet coated with carbon source obtained in step (1) in carbon quantum dot ethanol solution until the liquid evaporates completely;

[0079] (4) The material obtained in step (2) is placed in an atmosphere furnace and heated to 400°C at 1°C / min under an argon atmosphere and kept at that temperature for 2 hours to obtain a lithium-ion battery composite material with in-situ carbon coating on lithium nickelate.

[0080] Implementation Case 12:

[0081] (1) Dry lithium nickel cobalt manganese oxide is mixed with one of graphene and carboxymethyl cellulose in a ratio of 8:1:1 and coated onto aluminum foil, and then dried to form an electrode sheet with a thickness of 0.2 cm.

[0082] (2) Based on the mass ratio of lithium nickelate powder to polyvinylpyrrolidone of 1:1, polyvinylpyrrolidone is dissolved in ethanol to form a polyvinylpyrrolidone ethanol solution.

[0083] (3) Immerse the lithium nickel cobalt manganese oxygen electrode sheet coated with carbon source obtained in step (1) in polyvinylpyrrolidone ethanol solution until the liquid evaporates completely;

[0084] (4) The material obtained in step (3) is placed in an atmosphere furnace and heated to 500°C at 2°C / min under a nitrogen atmosphere and kept at that temperature for 2 hours to obtain a lithium-ion battery composite material with lithium nickel cobalt manganese oxygen in situ coated with carbon.

[0085] Figure 1 The graph shows the cycling performance of the carbon-coated silicon suboxide composite electrode. As can be seen from the graph, the cycling stability of the silicon suboxide electrode material is enhanced by the preparation method. This is because the carbon coating can suppress the volume expansion of the silicon suboxide electrode material to a certain extent. Figure 2 The graph shows the cycling performance of the carbon-coated sodium vanadate composite electrode. As can be seen from the graph, the cycling stability of the sodium vanadate electrode material is significantly improved, which is due to the enhanced conductivity of the sodium vanadate electrode material by the carbon coating. Therefore, the method of this invention can improve the lithium storage capacity and cycling stability of the electrode material. Furthermore, this method is applicable to all positive and negative electrode materials in the above embodiments, demonstrating a wide range of applicability.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an in-situ carbon-coated lithium-ion battery material, characterized in that, Includes the following steps: Step 1: Mix the dried lithium battery electrode material powder, conductive agent and binder in a mass ratio of 8:(0.1~3):(0.1~3) and stir evenly. Then coat the mixture onto a metal foil and dry it to make a lithium battery electrode sheet with a thickness of 0.01~0.5cm. Step 2: Immerse the lithium battery electrode sheet obtained in Step 1 in a carbon source solution until the carbon source solution is completely evaporated to obtain an electrode sheet coated with carbon source. Step 3: Place the carbon source-coated electrode sheet obtained in Step 2 into an atmosphere furnace, heat it to 300-600°C at a rate of 1-5°C / min, and hold it at that temperature for 1-24 hours for thermal reduction and carbonization. Then cool it to room temperature to form a uniform and stable carbon coating layer on the material surface, thus obtaining an in-situ carbon-coated lithium-ion battery material.

2. The method for preparing in-situ carbon-coated lithium-ion battery materials according to claim 1, characterized in that, The lithium battery electrode material powder in step 1 is either lithium battery positive electrode material powder or lithium battery negative electrode material powder. The lithium battery positive electrode material includes any one or more of lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide. The lithium battery negative electrode material includes any one or more of silicon, silicon suboxide, tin, tin dioxide, stannate, manganese dioxide, and vanadate.

3. The method for preparing in-situ carbon-coated lithium-ion battery materials according to claim 1, characterized in that, In step 1, the metal foil can be copper foil or aluminum foil. When the lithium battery electrode material is the negative electrode material, copper foil is selected; when the lithium battery electrode material is the positive electrode material, aluminum foil is selected.

4. The method for preparing in-situ carbon-coated lithium-ion battery materials according to claim 1, characterized in that, The carbon source is any one or more of polyvinylpyrrolidone, polyoxymethylene, polyacrylonitrile, polyvinyl alcohol, and carbon quantum dot powder.

5. The method for preparing in-situ carbon-coated lithium-ion battery material according to claim 1, characterized in that, The solvent for the carbon source solution is any one of ethylene glycol, water, ethanol, and N,N-dimethylformamide.

6. The method for preparing in-situ carbon-coated lithium-ion battery material according to claim 1, characterized in that, The conductive agent includes any one or more of acetylene black, graphene, and carbon nanotubes.

7. The method for preparing in-situ carbon-coated lithium-ion battery material according to claim 1, characterized in that, The adhesive includes any one or more of polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, and styrene-butadiene rubber.

8. The method for preparing in-situ carbon-coated lithium-ion battery material according to claim 1, characterized in that, The mass ratio of carbon source in the lithium battery electrode material powder and carbon source solution is 1:(0.01~1).

9. The method for preparing in-situ carbon-coated lithium-ion battery material according to claim 1, characterized in that, The gas introduced into the atmosphere furnace is any one of argon, nitrogen, or an argon / hydrogen mixture.

10. An in-situ carbon-coated lithium-ion battery material, characterized in that, Prepared by the method according to any one of claims 1-9.

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