Preparation method of silicon-carbon-based negative electrode material, prepared silicon-carbon-based negative electrode material and application of silicon-carbon-based negative electrode material

Abstract

The invention provides a preparation method of a silicon-carbon-based negative electrode material, the prepared silicon-carbon-based negative electrode material and application of the silicon-carbon-based negative electrode material. The preparation method of the silicon-carbon-based negative electrode material comprises the following steps: (1) mixing sodium silicate, a soluble carbon source and acid liquor to obtain a solution; (2) mixing the solution, silicon carbon and alkaline lithium salt to obtain a mixed solution; (3) drying the mixed solution to obtain powder, and mixing the powder with asphalt to obtain a mixture; and (4) reacting the mixture in an inert atmosphere at 600-800 DEG C for 1-3 hours, raising the temperature to 800-1000 DEG C, and reacting for 6-9 hours to obtain the silicon-carbon-based negative electrode material. According to the silicon-carbon-based negative electrode material provided by the invention, the coating layer is formed on the surface of the silicon-carbon material, can provide a stress buffer space for expansion of silicon particles, reduces the contact degree between the silicon-carbon material and an electrolyte, inhibits side reaction between the silicon-carbon material and the electrolyte, has a pre-lithiation effect, can reduce gas production, and improves the service life of the silicon-carbon-based negative electrode material. The expansion of silicon particles in the cell circulation process is inhibited, and the electrochemical performance is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for preparing a silicon-carbon based anode material, the prepared silicon-carbon based anode material, and its applications. Background Technology

[0002] Silicon-based materials, due to their high theoretical specific capacity, can significantly improve the energy density of batteries, leading to their increasing application in batteries. However, in practical applications, silicon-based anode materials also face some challenges. For example, silicon-based materials exhibit significant volume expansion; the lithium insertion / extraction process causes substantial changes in the volume of the anode material, severely impacting the battery's cycle capacity and lifespan. Furthermore, silicon-based materials react with the electrolyte and water during the homogenization process to generate gas, specifically: Si + 4H₂O = H₄SiO₄ + 2H₂↑, which may cause safety issues and also affect battery performance and lifespan.

[0003] In existing technologies, silicon-based materials are coated with carbon materials to form silicon-carbon materials, thereby improving their performance. However, current silicon-carbon materials have various problems that affect their use. For example, patent CN118825219B discloses a silicon-carbon anode material with a polymer coating, comprising silicon-carbon material and a coating layer covering the surface of the silicon-carbon material. The coating layer consists of an amphiphilic comb polymer and a crosslinking agent, wherein the amphiphilic comb polymer includes hydrophilic and hydrophobic side chains. Although coating the silicon surface with a coating layer can reduce the contact between the silicon-carbon material and water, suppress its side reactions with the electrolyte, and improve the dispersibility of the silicon-carbon material in water, this coating material is a polymer, which requires high solubility, has a complex synthesis process, and is costly. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention proposes a method for preparing a silicon-carbon-based anode material, the prepared silicon-carbon-based anode material, and its applications. When used in lithium-ion batteries, the silicon-carbon-based anode material provided by this invention exhibits low gas production and minimal volume expansion, effectively improving its electrochemical performance and safety.

[0005] In a first aspect, the present invention provides a method for preparing a silicon-carbon based anode material, comprising the following steps: (1) Mix sodium silicate, soluble carbon source and acid solution to obtain a solution; (2) The solution, silicon carbon, and alkaline lithium salt are mixed to obtain a mixed solution; (3) The mixture is dried to obtain a powder, and the powder is mixed with asphalt to obtain a mixture; (4) The mixture is reacted at 600~800℃ for 1~3h under an inert atmosphere, and then heated to 800~1000℃ for 6~9h to obtain the silicon-carbon based anode material.

[0006] The method for preparing silicon-carbon based anode materials provided in this invention involves coating a lithium-containing material layer and a carbon layer onto the surface of a silicon-carbon material. These layers form a coating material that provides stress buffering space for silicon particle expansion, reduces the contact between the silicon-carbon material and the electrolyte and water, and suppresses side reactions between the silicon-carbon material and the electrolyte and water. Simultaneously, the lithium-containing material in the coating material has a pre-lithiation effect on the silicon-carbon material. Therefore, the silicon-carbon based anode material prepared by this invention reduces gas generation while suppressing and buffering silicon particle expansion during cell cycling, thereby improving the cell's initial efficiency and capacity retention.

[0007] Meanwhile, this invention has found that as the amount of coating on the surface of silicon-carbon material increases, the gas production of silicon-carbon material decreases.

[0008] As a specific embodiment of the present invention, in step (1), the solid-liquid ratio of sodium silicate to acid solution is 0.0005~0.002g:mL.

[0009] As a specific embodiment of the present invention, in step (1), the acid solution is selected from any one or more of sulfuric acid, carbonic acid, hydrochloric acid or acetic acid.

[0010] As a specific embodiment of the present invention, in step (1), the hydrogen ion concentration in the acid solution is 0.05~5 mol / L, preferably 0.5~2 mol / L.

[0011] In a specific embodiment of the present invention, in step (1), the mass ratio of sodium silicate to the soluble carbon source is 1~5:1.

[0012] As a specific embodiment of the present invention, in step (1), the soluble carbon source is selected from any one or more of glucose, sucrose or fructose.

[0013] As a specific embodiment of the present invention, the molar ratio of sodium silicate in step (1) to alkaline lithium salt in step (2) is 1:2~5.

[0014] As a specific embodiment of the present invention, the alkaline lithium salt is selected from any one or more of lithium hydroxide, lithium bicarbonate, lithium carbonate, and lithium tetrafluoroborate.

[0015] As a specific embodiment of the present invention, the mass ratio of sodium silicate in step (1) to silicon carbon in step (2) is 1:10~50; preferably 1:10~30.

[0016] As a specific embodiment of the present invention, in step (2), the silicon carbon particle size is 5~15 mm, and the carbon content in the silicon carbon is 40wt%~60wt%.

[0017] As a specific embodiment of the present invention, the mass ratio of powder to asphalt in step (3) is 200~20:1; preferably 100~50:1.

[0018] As a specific embodiment of the present invention, the inert atmosphere in step (4) is selected from any one or more of nitrogen, helium, carbon dioxide or argon.

[0019] As a specific embodiment of the present invention, in step (4), the mixture is reacted at 600~800℃ for 1~3h under an inert atmosphere, then heated to 800~1000℃ for 6~9h, and the product is washed and dried to obtain the silicon-carbon based anode material.

[0020] Secondly, the present invention provides a silicon-carbon based anode material, which is prepared using the preparation method provided in the first aspect of the present invention.

[0021] Thirdly, the present invention provides an application of the silicon-carbon based anode material prepared by the preparation method provided in the second aspect of the present invention as a lithium-ion battery anode material. Preferably, when the silicon-carbon based anode material is used as a lithium-ion battery anode material, the gas production of the silicon-carbon based anode material is 2~4 cc / kg at 24h, 3~5 cc / kg at 48h, and 3.5~5.5 cc / kg at 72h. The initial efficiency of the silicon-carbon based anode material is 91%~92%, and the capacity retention rate after 200 charge-discharge cycles is 95%~98%.

[0022] Compared with the prior art, the present invention has the following beneficial effects.

[0023] The present invention provides a method for preparing silicon-carbon based anode materials by forming a coating layer on the surface of silicon-carbon materials. This coating layer provides stress buffering space for the expansion of silicon particles and reduces the contact between the silicon-carbon materials and the electrolyte and water, suppressing side reactions with the electrolyte and water. Simultaneously, the lithium-containing material in the coating layer has a pre-lithiation effect on the silicon-carbon materials. Based on these reasons, the silicon-carbon based anode material prepared by the present invention reduces gas production while suppressing and buffering the expansion of silicon particles during cell cycling, thereby improving the cell's first-time efficiency and cycle efficiency.

[0024] The silicon-carbon based anode material prepared by this invention is low in cost, simple to operate, and easy to industrialize. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0026] The silicon-carbon used in this invention was purchased from Sibao New Energy, model SC-02, with a particle size of 6-9 mm and a carbon content of 45wt%-55wt%.

[0027] Example 1: Step (1): Add 0.1g sodium silicate and 0.05g glucose to 100 mL of carbonic acid solution with a concentration of 0.5 mol / L (carbonic acid concentration) to obtain a solution; Step (2): Add 4g of silicon carbide and 0.0393g of lithium hydroxide to the solution, stir, and obtain a mixture; Step (3): Dry the mixture to obtain powder, and mix the powder and asphalt at a mass ratio of 80:1 to obtain a mixture; Step (4): In an inert gas atmosphere, the mixture is heated to 600°C and carbonized for 3 hours, then heated to 850°C and reacted for 6 hours to obtain the product. Step (5): The product is washed and dried by filtration with deionized water and ethanol in sequence to obtain silicon-carbon based anode material.

[0028] Example 2: A silicon-carbon based anode material differs from Example 1 in that the added silicon-carbon mass is 3g, while all other settings are the same as in Example 1.

[0029] Example 3: A silicon-carbon based anode material differs from Example 1 in that the added silicon-carbon mass is 2g, while all other settings are the same as in Example 1.

[0030] Example 4: A silicon-carbon based anode material differs from Example 1 in that the mass of added silicon-carbon is 1.5g, while all other settings are the same as in Example 1.

[0031] Example 5: A silicon-carbon based anode material differs from Example 1 in that the mass of added silicon-carbon is 1g, while all other settings are the same as in Example 1.

[0032] Comparative Example 1: A silicon-carbon based anode material differs from Example 1 in that 4g of silicon-carbon material is mixed with 100mL of water to obtain a mixed slurry, the mixed slurry is dried to obtain powder, the powder is heated to 600°C in an inert gas and carbonized for 3h, and then heated to 850°C and reacted for 6h to obtain the product.

[0033] Comparative Example 2: A silicon-carbon based anode material differs from Example 1 in that 4g of silicon-carbon material, 0.05g of glucose and 100mL of water are mixed to obtain a mixed slurry, the mixed slurry is dried to obtain powder, and the powder is heated to 600℃ for 3h in an inert gas atmosphere, and then heated to 850℃ for 6h to prepare the product.

[0034] Comparative Example 3: Step (1): Add 0.1g sodium silicate and 0.05g glucose to 100mL of a 0.5mol / L carbonic acid solution to obtain a solution; Step (2): Add 4g of silicon carbide and 0.0393g of lithium hydroxide to the solution, stir, and obtain a mixture; Step (3): Dry the mixture to obtain powder; Step (4): In an inert gas atmosphere, the powder is heated to 600°C and carbonized for 3 hours, then heated to 850°C and reacted for 6 hours to obtain the product. Step (5): The product is washed and dried by filtration with deionized water and ethanol in sequence to obtain silicon-carbon based anode material.

[0035] Comparative Example 4: Step (1): Add 0.1g sodium silicate and 0.05g glucose to 100mL of a 0.5mol / L carbonic acid solution to obtain a solution; Step (2): Add 4g of silicon carbon to the solution and stir to obtain a mixture; Step (3): Dry the mixture to obtain powder, and mix the powder and asphalt at a mass ratio of 80:1 to obtain a mixture; Step (4): In an inert gas atmosphere, the mixture is heated to 600°C and carbonized for 3 hours, then heated to 850°C and reacted for 6 hours to obtain the product. Step (5): The product is washed and dried by filtration with deionized water and ethanol in sequence to obtain silicon-carbon based anode material.

[0036] Gas production and electrochemical performance tests were performed on the materials prepared in the examples and comparative examples.

[0037] Gas production test: Take m=10g of the material prepared in the examples and comparative examples and 15g of water and add it to an aluminum-plastic bag. Keep the aluminum-plastic bag upright, vacuum seal it with a vacuum sealer, and then heat seal it. Shake the sealed aluminum-plastic bag by hand for 1 minute. In a constant temperature room at 25℃, use a solid density meter to measure the volume V0, V1, V2, and V3 of the aluminum-plastic bag after 0h, 24h, 48h, and 72h. Then, calculate the gas production R using the formula R=(Vx-V0) / m. The results are shown in Table 1, where Vx is V1, V2, or V3.

[0038] Table 1 Gas production of materials prepared in the examples and comparative examples.

[0039] A comparison of Examples 1-5 and Comparative Examples 1-4 in Table 1 shows that the silicon-carbon based anode material of the present invention can effectively reduce gas production. Furthermore, Examples 1-5 demonstrate that gas production decreases when the amount of silicon-carbon added is reduced.

[0040] Electrochemical performance testing: Using 90% doped artificial graphite as the negative electrode, the nickel-cobalt-manganese ternary material NCM111 as the positive electrode, LiPF6 as the lithium salt, and a 1:1 volume ratio of ethylene carbonate (EC) and diethyl carbonate (DEC) as the electrolyte solvent, a Celgard 2400 membrane was used as the separator to prepare a soft-pack lithium-ion battery. Cyclic testing (capacity retention after 200 cycles) was conducted under the following conditions: voltage range: 2.75V~4.25V, charge / discharge 1C / 1C. The cycle test results are shown in Table 2.

[0041] Table 2 Electrochemical performance of materials prepared in the examples and comparative examples

[0042] From Example 1 in Table 2 5 and Comparative Example 1 As can be seen from 4, the silicon-carbon based anode material of the present invention can effectively improve the first-cycle efficiency of the battery and improve the cycle stability.

[0043] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a silicon-carbon based anode material, characterized in that, Includes the following steps: (1) Mix sodium silicate, soluble carbon source and acid solution to obtain a solution; (2) The solution, silicon carbon, and alkaline lithium salt are mixed to obtain a mixed solution; (3) The mixture is dried to obtain a powder, and the powder is mixed with asphalt to obtain a mixture; (4) The mixture is reacted at 600~800℃ for 1~3h under an inert atmosphere, and then the temperature is raised to 800~1000℃ for 6~9h to obtain the silicon-carbon based anode material.

2. The preparation method according to claim 1, characterized in that, In step (1), the solid-liquid ratio of sodium silicate to acid solution is 0.0005~0.002 g:1 mL; And / or, in step (1), the acid solution is selected from any one or more of sulfuric acid, carbonic acid, hydrochloric acid or acetic acid; And / or, in step (1), the hydrogen ion concentration in the acid solution is 0.05~5 mol / L, preferably 0.5~2 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the mass ratio of sodium silicate to the soluble carbon source is 1~5:1; And / or, in step (1), the soluble carbon source is selected from any one or more of glucose, sucrose or fructose.

4. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of sodium silicate in step (1) to alkaline lithium salt in step (2) is 1:2~5; And / or, the alkaline lithium salt is selected from any one or more of lithium hydroxide, lithium bicarbonate, lithium carbonate, and lithium tetrafluoroborate.

5. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of sodium silicate in step (1) to silicon carbon in step (2) is 1:10~50; preferably 1:10~30.

6. The preparation method according to claim 1 or 2, characterized in that, In step (3), the mass ratio of powder to asphalt is 200~20:1; preferably 100~50:

1.

7. The preparation method according to claim 1 or 2, characterized in that, The inert atmosphere mentioned in step (4) is selected from any one or more of nitrogen, helium, carbon dioxide or argon.

8. The preparation method according to claim 1 or 2, characterized in that, In step (4), the mixture is reacted at 600~800℃ for 1~3h under an inert atmosphere, then heated to 800~1000℃ for 6~9h. The product is then washed and dried to obtain the silicon-carbon based anode material.

9. A silicon-carbon based anode material, characterized in that, Prepared using the preparation method described in any one of claims 1 to 8.

10. The application of the silicon-carbon based anode material according to claim 9 as a lithium-ion battery anode material, preferably, when the silicon-carbon based anode material is used as a lithium-ion battery anode material, the gas production of the silicon-carbon based anode material is 2~4CC / kg at 24h, the initial efficiency of the silicon-carbon based anode material is 91%~92%, and the capacity retention rate after 200 charge-discharge cycles is 95%~98%.

Images