Silicon-carbon negative electrode material, preparation method thereof and lithium ion battery

Abstract

The application relates to the technical field of lithium ion battery negative electrode materials, and discloses a silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps: (1) mixing an oxidized graphene dispersion liquid with an alkali, adjusting the pH to 8-12 to obtain an oxidized graphene slurry; (2) mixing the oxidized graphene slurry, silicon powder and graphite, and then drying to obtain a precursor; taking the total amount of the oxidized graphene, the silicon powder and the graphite as a reference, the content of the oxidized graphene is 0.1-5 wt%, the content of the silicon powder is 20-65 wt%, and the content of the graphite is 35-75 wt%; (3) performing heat treatment on the precursor under an inert atmosphere. The silicon-carbon negative electrode prepared by the preparation method has obvious excellent cycle stability while maintaining a relatively high capacity.

Description

Technical Field

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

[0002] Lithium-ion batteries, due to their superior performance, have been widely used in portable consumer electronics, power tools, medical electronics, and other fields, and are currently the most widely used power batteries. Graphite-based materials, due to their small volume change (<10%) during lithiation, high specific capacity (372 mAh / g), low potential, stable structure, and low cost, have long held a dominant market share in anode materials. Currently, with battery technology development reaching its limits and cathode material capacity improvement encountering bottlenecks, developing and applying silicon-based anode materials with higher specific capacity (theoretical specific capacity 4200 mAh / g) has become an important means to further improve the energy density of lithium-ion batteries.

[0003] However, the severe volume expansion effect of silicon during battery charging and discharging restricts the application of high-capacity silicon-carbon anodes. Nano-sizing of silicon helps to mitigate this volume expansion, but the small particle size, large specific surface area, and high surface activity of nano-silicon make it prone to agglomeration during preparation and dispersion, thus affecting material utilization and electrochemical performance. Therefore, improving the dispersibility of nano-silicon powder is crucial.

[0004] Existing processes for preparing nano-silicon powder include chemical vapor deposition (CVD) and ball milling. CVD produces nano-silicon with uniform particle size and good electrochemical performance, but the silanes used are flammable and explosive, and byproducts include hydrogen and oligomeric silanes, posing high barriers to industrialization due to the demanding requirements of the equipment. In contrast, ball milling and sand milling methods have lower equipment requirements and simpler processes, making them more suitable for large-scale industrialization at present. However, the problem of uniform dispersion of silicon powder still needs to be solved during the preparation process.

[0005] CN118122164A discloses a dispersion process for nano-silicon powder, which modifies the nano-silicon powder with hydrophilic groups using a quaternary ammonium salt solution and a dispersant with electronegative groups, thereby enabling the nano-silicon to be stably dispersed in an aqueous system. However, if an aqueous solvent is used to prepare nano-silicon, the hydrogen production problem during the preparation process cannot be solved, and the reaction is too vigorous, which is not conducive to scale-up production.

[0006] CN112645333A discloses a method for preparing nano-silicon anodes. This method is simple and can produce nano-silicon particles with a diameter of up to 50 μm. However, for application in silicon-carbon anodes, the additive content is too high, which significantly affects the electrochemical performance during subsequent applications and is detrimental to maximizing the electrical performance of silicon-carbon anodes. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem of poor cycle performance of silicon-based anode materials in the prior art, and to provide a silicon-carbon anode material, its preparation method, and a lithium-ion battery. This silicon-carbon anode material can have both high charge specific capacity and excellent cycle stability.

[0008] To achieve the above objectives, the present invention provides a method for preparing a silicon-carbon anode material, comprising the following steps:

[0009] (1) Mix the graphene oxide dispersion with alkali and adjust the pH to 8-12 to obtain graphene oxide slurry;

[0010] (2) Mix graphene oxide slurry, silicon powder and graphite, and then dry them to obtain the precursor;

[0011] Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.1-5 wt%, the content of silicon powder is 20-65 wt%, and the content of graphite is 35-75 wt%.

[0012] (3) The precursor is heat-treated in an inert atmosphere.

[0013] A second aspect of the present invention provides a silicon-carbon anode material prepared by the above-described preparation method.

[0014] A third aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery includes a positive electrode and a negative electrode, wherein the negative electrode includes the silicon-carbon negative electrode material described in the second aspect.

[0015] Through the above technical solutions, the method for preparing silicon-carbon anode materials provided by this invention introduces an appropriate amount of alkali-treated graphene oxide during the preparation process. The resulting silicon-carbon anode exhibits significantly superior cycle stability while maintaining a high capacity. This is likely because the introduction of alkali-treated graphene oxide provides numerous active sites that bind to the silicon powder surface through electrostatic forces, promoting uniform dispersion of silicon powder on the graphite particle surface. Simultaneously, the introduction of graphene oxide slurry helps stabilize the dispersion of nano-silicon and graphite slurry, reducing silicon agglomeration and thus improving the electrochemical performance of the high-specific-capacity silicon-carbon anode. Attached Figure Description

[0016] Figure 1 This is a SEM image (815x magnification) of the silicon-carbon anode material in Example 1 of this invention;

[0017] Figure 2 This is a SEM image (428x) of the silicon-carbon anode material in Example 1 of this invention;

[0018] Figure 3This is a cycle performance diagram of the negative electrode material in Embodiment 1 of the present invention at a rate of 0.2C;

[0019] Figure 4 This is a graph showing the cycling performance of the negative electrode material in Comparative Example 1 of this invention at a rate of 0.2C. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of this invention provides a method for preparing a silicon-carbon anode material, comprising the following steps:

[0022] (1) Mix the graphene oxide dispersion with alkali and adjust the pH to 8-12 to obtain graphene oxide slurry;

[0023] (2) Mix graphene oxide slurry, silicon powder and graphite, and then dry them to obtain the precursor;

[0024] Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.1-5 wt%, the content of silicon powder is 20-65 wt%, and the content of graphite is 35-75 wt%.

[0025] (3) The precursor is heat-treated in an inert atmosphere.

[0026] The inventors of this invention discovered in their research that introducing an appropriate amount of alkali-treated graphene oxide during the preparation of silicon-carbon anode materials utilizes the large number of active sites it provides to bond with the silicon powder surface through electrostatic forces, promoting the uniform dispersion of silicon powder on the surface of graphite particles. At the same time, the introduction of graphene oxide slurry helps to stabilize the dispersion of nano-silicon and graphite slurry, reducing silicon agglomeration, thereby improving the electrochemical performance of high-specific-capacity silicon-carbon anodes.

[0027] In this invention, the pH of the graphene oxide slurry is adjusted by using an alkali, controlling the pH of the graphene oxide slurry to be 8-12, preferably 10-12. Under these preferred conditions, it is beneficial to further improve the dispersibility of graphene oxide in the solvent, reduce the stacking of graphene sheets, and help to further improve the electrochemical performance of the prepared silicon-carbon anode material.

[0028] In this invention, preferably, the graphene oxide dispersion comprises graphene oxide and a solvent. Preferably, the solvent is water. Graphene oxide has high viscosity in an aqueous system, which, in the above-mentioned preferred embodiment, further facilitates the stable dispersion of silicon powder and graphite.

[0029] Preferably, in the graphene oxide dispersion, the mass ratio of graphene oxide to solvent is (0.01-0.09):1, more preferably (0.01-0.04):1. Using the graphene oxide dispersion with the above-mentioned preferred composition is beneficial for further improving the electrochemical performance of the prepared silicon-carbon anode material.

[0030] In this invention, a wide range of alkaline types can be selected, and any alkaline compounds conventionally used in the art for adjusting pH can be applied. Preferably, the alkaline is selected from at least one of ammonia, sodium hydroxide, and lithium hydroxide, and more preferably ammonia with a mass concentration of 25%-28%.

[0031] The present invention does not impose any particular limitation on the mixing method. Those skilled in the art can choose according to actual needs, as long as the graphene oxide dispersion and the alkali are mixed into a uniform slurry.

[0032] According to some preferred embodiments of the present invention, the mixing method in step (1) is high-pressure homogenization, which can be carried out in a homogenizer.

[0033] Preferably, the pressure of the high-pressure homogenization treatment is 500-1000 MPa, more preferably 700-900 MPa; the treatment time is 10-60 min, more preferably 20-40 min.

[0034] According to the present invention, the silicon powder is micron-sized silicon powder, preferably, the median particle size of the silicon powder is 50-400 μm, more preferably 50-200 μm.

[0035] According to the present invention, preferably, the median particle size of the graphite is 5-25 μm, more preferably 10-20 μm.

[0036] In this invention, the median particle size of the material is obtained by testing with a Malvern laser particle size analyzer.

[0037] The present invention does not have any particular limitation on the source of the silicon powder and graphite, which can be commercially available. Preferably, the graphite is selected from artificial graphite and / or natural graphite.

[0038] In this invention, by introducing a small amount of graphene oxide through the above preparation method, it is possible to promote the stable dispersion of silicon powder and graphite slurry, reduce silicon agglomeration, and make silicon powder uniformly dispersed on the surface of graphite particles, thereby improving the electrochemical performance of high specific capacity silicon-carbon anode.

[0039] According to the present invention, the amounts of graphene oxide slurry, silicon powder and graphite are such that, based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.1-5 wt%, the content of silicon powder is 20-65 wt%, and the content of graphite is 35-75 wt%.

[0040] Preferably, based on the total amount of graphene oxide, silicon powder, and graphite, the content of graphene oxide is 0.5-1 wt%, the content of silicon powder is 40-62 wt%, and the content of graphite is 35-55 wt%. Controlling the content of each component within the above-mentioned preferred range is beneficial to improving the first-efficiency and cycle stability of the material while achieving a high specific capacity.

[0041] To further improve the stability of the prepared silicon-carbon anode material, preferably, the silicon powder in step (2) is provided by a silicon powder slurry containing silicon powder, solvent and optional dispersant.

[0042] Preferably, the dispersant is selected from at least one of polyacrylic acid, carboxymethyl cellulose, polyether, polymethacrylic acid, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium alginate, lithium alginate, styrene-butadiene rubber, polyvinyl butyral, phytic acid, and phosphoric acid, and more preferably at least one of polyether, polyacrylic acid, and phytic acid. Introducing the above-mentioned preferred dispersant into the silicon powder slurry is beneficial for modifying the silicon powder surface, improving the dispersibility of the silicon powder, reducing the surface tension of the slurry, reducing powder floating, and further improving the electrochemical performance of the obtained silicon-carbon anode material.

[0043] According to the present invention, preferably, the content of dispersant is 0.1-5 wt%, more preferably 0.3-1 wt%, based on the total amount of the silicon powder slurry.

[0044] Preferably, the solvent is an alcohol and / or water, and the alcohol may be, for example, ethanol.

[0045] According to some preferred embodiments of the present invention, the solvent comprises alcohol and water, wherein the mass ratio of alcohol to water is 0.5-4:1.

[0046] According to some particularly preferred embodiments of the present invention, the silicon powder is provided by a silicon powder slurry, the silicon powder slurry comprising silicon powder, ethanol and / or water, and a dispersant selected from at least one of polyether, polyacrylic acid, and phytic acid. Using the above preferred embodiments facilitates further modification of the silicon powder surface and improves silicon powder dispersibility.

[0047] The present invention does not have a particular limitation on the mixing order described in step (2), as long as the graphene oxide slurry, silicon powder (or silicon powder slurry) and graphite are mixed evenly.

[0048] According to some preferred embodiments of the present invention, the mixing in step (2) includes:

[0049] (2-1) The silicon powder, solvent and optional dispersant are first mixed to obtain silicon powder slurry;

[0050] (2-2) The silicon powder slurry and the graphene oxide slurry are mixed for the second time;

[0051] (2-3) Mix the mixture obtained in step (2-2) with graphite for a third time.

[0052] The preferred embodiments described above facilitate thorough mixing of materials, prevent powder agglomeration that could lead to uneven dispersion of silicon and graphite, and help to further improve the electrochemical performance of the prepared silicon-carbon anode material.

[0053] The terms "first," "second," and "third" in the aforementioned "first mixing," "second mixing," and "third mixing" are used only to distinguish mixing in different steps. The mixing methods and conditions can be the same or different, and all can be carried out using conventional mixing methods in the art, such as stirring, ball milling, sand milling, high-pressure homogenization, etc. Preferably, the mixing methods for the first, second, and third mixing are each independently selected from ball milling or sand milling, and the mixing time is 0.5-6 hours.

[0054] According to the preparation method of the present invention, step (2) further includes performing solid-liquid separation and washing on the obtained mixture, followed by drying to obtain the precursor. The present invention does not particularly limit the method of solid-liquid separation and washing; conventional methods in the art can be used, with the aim of removing the solvent to obtain a solid product. The solid-liquid separation can be performed, for example, by vacuum filtration.

[0055] In this invention, there are no particular limitations on the drying method and conditions described in step (2), and vacuum drying or spray drying can be used. Preferably, the drying temperature is 80-140°C.

[0056] According to the present invention, preferably, the preparation method further includes: optionally pulverizing the precursor and then subjecting it to heat treatment. Preferably, the pulverization conditions are such that the median particle size of the obtained silicon-carbon anode material is 10-19 μm.

[0057] According to the present invention, the precursor is carbonized by the heat treatment described in step (3). Preferably, the heat treatment temperature is 400-1000℃, the time is 10min-6h, and the heating rate is 1-20℃ / min.

[0058] In a further preferred embodiment, the heat treatment is performed using a gradient heating method. Preferably, the heat treatment method includes: heating the precursor to 200-400°C at a heating rate of 1-20°C / min, holding at that temperature for 10 min-6 h, and then heating to 650-1000°C and holding at that temperature for 10 min-6 h. Using the above preferred embodiment facilitates the removal of oxygen-containing functional groups from graphene oxide at a lower temperature, improving the conductivity of graphene; high-temperature calcination facilitates the carbonization of the carbon source in the precursor, forming a coating layer on the material surface, thereby improving the electrochemical performance of the material.

[0059] In this invention, the inert atmosphere refers to any non-reactive gas that does not participate in the reaction; preferably, the inert atmosphere is provided by nitrogen.

[0060] A second aspect of the present invention provides a silicon-carbon anode material prepared by the above-described preparation method.

[0061] A third aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery includes a positive electrode and a negative electrode, wherein the negative electrode includes the silicon-carbon negative electrode material described in the second aspect.

[0062] The present invention does not particularly limit the active material in the positive electrode of the lithium-ion battery, and can be any lithium-containing compound that is conventional in the art and can be used as a positive electrode active material.

[0063] This invention does not impose any particular limitation on the other components of the lithium-ion battery; all can be conventional choices in the art, as long as they include the aforementioned silicon-carbon anode material. For example, the lithium-ion battery may also include a separator and an electrolyte. The lithium-ion battery can also be any type of lithium-ion battery in the art, such as any one of a liquid lithium-ion battery, a semi-solid lithium-ion battery, or an all-solid lithium-ion battery.

[0064] The present invention will be described in detail below through embodiments.

[0065] Example 1

[0066] (1) 80g of micron-sized silicon powder (median particle size of 100μm) and 5.47g of phytic acid were dispersed in 1600g of ethanol and treated with a sand mill for 2h to obtain silicon powder slurry;

[0067] (2) Disperse 1.08g of graphene oxide powder in 54g of water, add ammonia (concentration of 25wt%) dropwise until pH is 12, then use a high pressure homogenizer to homogenize at 800MPa pressure for 30min to obtain a paste-like graphene oxide slurry, then add the graphene oxide slurry to the silicon powder slurry and continue sand milling for 2h;

[0068] (3) Add 50g of natural graphite (median particle size of 15μm) to the mixed slurry obtained in step (2), wherein, based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.8wt%, the content of silicon powder is 61wt%, and the content of graphite is 38.2wt%. Grind for 30min, filter, wash, dry at 80℃, and pulverize to obtain the precursor;

[0069] (4) Under nitrogen conditions, the temperature is increased to 200℃ at a rate of 5℃ / min and held for 2 hours, and then increased to 800℃ at a rate of 5℃ / min and held for 30 minutes to obtain silicon-carbon anode material.

[0070] The median particle size of the silicon-carbon anode material is 16.8 μm.

[0071] The morphology of the silicon-carbon anode material was observed using scanning electron microscopy. The SEM images at magnifications of 815x and 428x are shown below. Figure 1 and Figure 2 As shown, silicon powder is uniformly dispersed on the surface of graphite particles.

[0072] Example 2

[0073] (1) 55g of micron-sized silicon powder (median particle size of 80μm) and 6g of phytic acid were dispersed in 1600g of ethanol and treated with a sand mill for 2h to obtain silicon powder slurry;

[0074] (2) Disperse 0.69g of graphene oxide powder in 60g of water, add ammonia (concentration of 25wt%) dropwise until pH is 10, then use a high pressure homogenizer to homogenize at 700MPa pressure for 30min to obtain a paste-like graphene oxide slurry, then add the graphene oxide slurry to the silicon powder slurry and continue sand milling for 2h.

[0075] (3) Add 75g of natural graphite (median particle size of 10μm) to the mixed slurry obtained in step (2), and mill for 30min. Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.5wt%, the content of silicon powder is 42.1wt%, and the content of graphite is 57.4wt%. After filtration and washing, dry at 80℃, and pulverize to obtain the precursor;

[0076] (4) Under nitrogen conditions, the temperature was increased to 400℃ at a rate of 5℃ / min and held for 2 hours, and then increased to 1000℃ at a rate of 5℃ / min and held for 10 minutes to obtain silicon-carbon anode material.

[0077] The median particle size of the silicon-carbon anode material is 12.8 μm.

[0078] Example 3

[0079] (1) 60g of micron-sized silicon powder (median particle size of 200μm) and 8.47g of phytic acid were dispersed in 1600g of ethanol and treated with a sand mill for 2h to obtain silicon powder slurry;

[0080] (2) Disperse 1.1g of graphene oxide powder in 36g of water, add ammonia (concentration of 25wt%) dropwise until pH is 11, then use a high pressure homogenizer to homogenize at 900MPa pressure for 30min to obtain a paste-like graphene oxide slurry, then add the graphene oxide slurry to the silicon powder slurry and continue sand milling for 2h.

[0081] (3) Add 38g of natural graphite (median particle size of 20μm) to the mixed slurry obtained in step (2), and mill for 30min. Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 1.1wt%, the content of silicon powder is 60.6wt%, and the content of graphite is 38.3wt%. After filtration and washing, dry at 80℃, and pulverize to obtain the precursor;

[0082] (4) Under nitrogen conditions, the temperature was increased to 400℃ at a rate of 5℃ / min and held for 2 hours, and then increased to 650℃ at a rate of 5℃ / min and held for 6 hours to obtain silicon-carbon anode material.

[0083] The median particle size of the silicon-carbon anode material is 20.5 μm.

[0084] Example 4

[0085] The method is the same as in Example 1, except that in step (2), the amount of graphene oxide powder used is 5g. Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 3.7wt%, the content of silicon powder is 59.3wt%, and the content of graphite is 37wt%.

[0086] Example 5

[0087] The method is the same as in Example 1, except that in step (1), ammonia is added dropwise to adjust the pH to 8.

[0088] Silicon-carbon anode material was obtained.

[0089] Example 6

[0090] The method of Example 1 is followed, except that phytic acid is not added in step (1). A silicon-carbon anode material is obtained.

[0091] Example 7

[0092] The method of Example 1 is followed, except that in step (4), the temperature is increased to 800°C at a rate of 5°C / min under nitrogen atmosphere and held for 30 hours to obtain silicon-carbon anode material.

[0093] Comparative Example 1

[0094] (1) Disperse 80g of micron-sized silicon and 5.47g of phytic acid in 1600g of ethanol and treat with a sand mill for 4h;

[0095] (2) Add 50g of natural graphite to the slurry obtained in (1), mill for 30min, filter, wash, dry, and pulverize to obtain silicon-carbon anode precursor.

[0096] (3) Under nitrogen conditions, the temperature was increased to 800℃ at a rate of 5℃ / min and held for 30min to obtain silicon-carbon anode material.

[0097] Comparative Example 2

[0098] (1) 80g of micron-sized silicon powder (median particle size of 100μm) and 5.47g of phytic acid were dispersed in 1600g of ethanol and treated with a sand mill for 2h to obtain silicon powder slurry;

[0099] (2) Disperse 1.08g of graphene oxide powder in 54g of water, then add the graphene oxide dispersion into the silicon powder slurry and continue sand milling for 2 hours.

[0100] (3) Add 50g of natural graphite (median particle size of 15μm) to the mixed slurry obtained in step (2), mill for 30min, filter and wash, dry at 80℃, and pulverize to obtain the precursor.

[0101] (4) Under nitrogen conditions, the temperature is increased to 200℃ at a rate of 5℃ / min and held for 2 hours, and then increased to 800℃ at a rate of 5℃ / min and held for 30 minutes to obtain silicon-carbon anode material.

[0102] Comparative Example 3

[0103] The method is the same as in Example 1, except that in step (2), the amount of graphene oxide powder used is 9g. Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 6.5wt%, the content of silicon powder is 57.5wt%, and the content of graphite is 36wt%.

[0104] Test case

[0105] A slurry was prepared by mixing hydroxymethyl cellulose (CMC), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR) in a mass ratio of 1:1:1 as binders, Super P conductive carbon black as a conductive agent, and water as a solvent with the negative electrode materials prepared in the above examples and comparative examples. The mass ratio of negative electrode material, conductive agent, and binder was 80:10:10. After stirring evenly, a slurry was prepared. The solid content of the slurry was controlled to be 30%. The slurry was coated on copper foil with a thickness of 100 μm and then vacuum dried at 80 °C to obtain the negative electrode sheet.

[0106] Using the electrode sheet prepared above as the positive electrode, the lithium metal sheet as the negative electrode, a 1 mol / L LiPF6 solution as the electrolyte, and a polypropylene microporous membrane as the separator, a CR2016 button cell was assembled.

[0107] The electrical performance was characterized using the Wuhan Landian Battery Testing System (CT2001B). Test conditions included a voltage range of 0.005V-3V and a current range of 0.05A-2A. Ten coin cells were assembled for each sample, and battery performance, as well as cycle performance at 0.2C, were tested under the same voltage and current conditions. The results were averaged. The results are shown in Table 1.

[0108] A set of cycle performance diagrams for the silicon-carbon anode materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 3 and Figure 4 As shown.

[0109] Table 1

[0110]

[0111] As can be seen from the results in Table 1, the silicon-carbon anode material prepared in the embodiments of the present invention has a higher capacity retention rate and good cycle performance while ensuring a high specific capacity.

[0112] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a silicon-carbon anode material, characterized in that, Includes the following steps: (1) Mix the graphene oxide dispersion with alkali and adjust the pH to 8-12 to obtain graphene oxide slurry; (2) Mix graphene oxide slurry, silicon powder and graphite, and then dry them to obtain the precursor; Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.1-5 wt%, the content of silicon powder is 20-65 wt%, and the content of graphite is 35-75 wt%. (3) The precursor is heat-treated under an inert atmosphere.

2. The preparation method according to claim 1, wherein, The pH of the graphene oxide slurry is 10-12; Preferably, the alkali is selected from at least one of ammonia, sodium hydroxide, and lithium hydroxide; Preferably, the graphene oxide dispersion comprises graphene oxide and a solvent; Preferably, the solvent is water; Preferably, in the graphene oxide dispersion, the mass ratio of graphene oxide to solvent is (0.01-0.09):1, more preferably (0.01-0.04):

1.

3. The preparation method according to claim 1 or 2, wherein, The mixing method described in step (1) is high-pressure homogenization, with a pressure of 500-1000 MPa and a processing time of 10-60 min.

4. The preparation method according to any one of claims 1-3, wherein, The median particle size of the silicon powder is 50-400 μm, preferably 50-200 μm; Preferably, the median particle size of the graphite is 5-25 μm, and more preferably 10-20 μm; Preferably, the graphite is selected from artificial graphite and / or natural graphite.

5. The preparation method according to any one of claims 1-4, wherein, Based on the total amount of graphene oxide, silicon powder and graphite, the content of graphene oxide is 0.5-1 wt%, the content of silicon powder is 40-62 wt%, and the content of graphite is 35-55 wt%.

6. The preparation method according to any one of claims 1-5, wherein, The silicon powder in step (2) is provided from a silicon powder slurry containing silicon powder, solvent and optional dispersant; Preferably, the dispersant is selected from at least one of polyacrylic acid, carboxymethyl cellulose, polyether, polymethacrylic acid, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium alginate, lithium alginate, styrene-butadiene rubber, polyvinyl butyral, phytic acid, and phosphoric acid, and more preferably at least one of polyether, polyacrylic acid, and phytic acid. Preferably, based on the total amount of the silicon powder slurry, the content of the dispersant is 0.1-5 wt%, more preferably 0.3-1 wt%. Preferably, the solvent is an alcohol and / or water.

7. The preparation method according to any one of claims 1-6, wherein, The mixing in step (2) includes: (2-1) The silicon powder, solvent and optional dispersant are first mixed to obtain silicon powder slurry; (2-2) The silicon powder slurry and the graphene oxide slurry are mixed for the second time; (2-3) Mix the mixture obtained in step (2-2) with graphite for a third time.

8. The preparation method according to any one of claims 1-7, wherein, In step (3), the heat treatment temperature is 400-1000℃, the time is 10min-6h, and the heating rate is 1-20℃ / min; Preferably, the heat treatment method includes: heating the precursor to 200-400°C at a heating rate of 1-20°C / min, holding at that temperature for 10 min-6 h, and then heating it to 650-1000°C and holding it for 10 min-6 h.

9. The silicon-carbon anode material prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery, wherein, The lithium-ion battery includes a positive electrode and a negative electrode, wherein the negative electrode includes the silicon-carbon negative electrode material as described in claim 9.

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