Silicon negative electrode material battery negative electrode sheet and lithium-ion battery

Abstract

The present application relates to the field of materials, and more specifically, to a silicon negative electrode material, a battery negative electrode sheet, and a lithium-ion battery. The silicon negative electrode material comprises a nano-sheet silicon-based material and a carbon coating layer, with a metal layer or metal particles between the carbon coating layer and the silicon-based material. The surface of the silicon negative electrode material of the present application has a carbon coating layer, which can effectively prevent the direct contact between the nano-sheet silicon-based material and the electrolyte, and the SEI film formed on the coating layer is thin and stable. In addition, there is a metal layer or metal particles between the nano-sheet silicon-based material and the carbon coating layer, and the good electrical conductivity of the metal can compensate for the poor electrical conductivity of silicon.

Description

Technical Field

[0001] The present application relates to the field of materials, and specifically to a silicon negative electrode material, a battery negative electrode sheet, and a lithium-ion battery. Background Art

[0002] Silicon has attracted great attention from researchers due to its extremely high theoretical lithium insertion capacity (up to 4200mAh / g) and low lithium storage potential, making it an ideal candidate for new high-capacity lithium storage materials. However, during the lithium storage process, silicon expands by more than 300%, which can easily cause the silicon particles to pulverize, causing the active material to fall off the current collector, resulting in a significant decrease in the cycling stability of the electrode. At the same time, when silicon particles are exposed to the electrolyte, an unstable SEI (solidelectrolyte interphase) film will form on the silicon surface, reducing the cycling performance of the electrode material. In addition, silicon material is a semiconductor, so its conductivity is not as good as that of graphite negative electrodes, which limits its rate performance.

[0003] To address issues such as the volume change of silicon anodes during lithium insertion and extraction, carbon coating is commonly used to improve the cycling performance of silicon anode materials. Even so, optimizing the electrochemical performance of carbon-coated silicon anodes remains a technical challenge that the industry is striving to address. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a silicon negative electrode material, a battery negative electrode sheet and a lithium-ion battery, which are intended to improve the electrochemical performance of the carbon-coated silicon negative electrode material.

[0005] The present application provides a silicon negative electrode material, comprising a nano-sheet silicon-based material and a carbon coating layer, wherein a metal layer or metal particles are provided between the carbon coating layer and the silicon-based material.

[0006] The carbon coating of the silicon negative electrode material can effectively prevent direct contact between the nano-sheet silicon-based material and the electrolyte, and the SEI film formed on the coating is thin and stable. In addition, there is a metal layer or metal particles between the nano-sheet silicon-based material and the carbon coating. The good conductivity of the metal can compensate for the poor conductivity of silicon. This can make the silicon negative electrode material of the present application have excellent electrochemical performance, a specific capacity of more than 1000mAh / g, and excellent rate performance.

[0007] In some embodiments of the present application, the nano-sheet-shaped silicon-based material includes one or more of silicon nanosheets, silicon alloy nanosheets, and silicon monoxide nanosheets.

[0008] In some embodiments of the present application, the silicon alloy includes one or more of silicon-aluminum alloy, silicon-magnesium alloy, and silicon-ferroalloy.

[0009] In some embodiments of the present application, the thickness of the silicon nanosheet is 5-100 nm; the plane size is 100-2000 nm, the thickness of the metal layer is 1-20 nm, and the thickness of the carbon coating layer is 2-20 nm.

[0010] In some embodiments of the present application, the graphitization degree γ of the carbon coating layer satisfies 0.3≦γ≦1, where γ=(0.344-d 002 ) / (0.344-0.3354), d 002 is the nanolayer spacing of the carbon coating layer on the 002 crystal plane.

[0011] In some embodiments of the present application, the metal in the metal layer or the metal particles includes one or more of tin, copper, iron, silver, and magnesium.

[0012] In some embodiments of the present application, the weight percentage of silicon is 70% to 98%, the weight percentage of metal is 0.5% to 20%, the weight percentage of carbon is 1.5-20%, and the weight percentage of oxygen is 0% to 10%.

[0013] The present application also provides a battery negative electrode sheet, which includes any one of the above-mentioned silicon negative electrode materials.

[0014] The present application also provides a lithium-ion secondary battery, which includes the above-mentioned battery negative electrode sheet.

[0015] The present application also provides a lithium-ion solid-state battery, which includes the above-mentioned battery negative electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a scanning electron microscope (SEM) image of the silicon negative electrode material provided in Example 1 of the present application;

[0018] Figure 2 This is a transmission electron microscope (TEM) image of the silicon anode material provided in Example 1 of the present application;

[0019] Figure 3 This is the electrochemical cycle diagram of the silicon negative electrode material provided in Example 1 of the present application. DETAILED DESCRIPTION

[0020] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0021] The silicon negative electrode material, battery negative electrode sheet and lithium-ion battery of the embodiments of the present application are described in detail below.

[0022] The silicon negative electrode material comprises a nano-sheet silicon-based material and a carbon coating layer, wherein a metal layer or metal particles are provided between the carbon coating layer and the silicon-based material.

[0023] The carbon coating of the silicon negative electrode material can effectively prevent direct contact between the nano-sheet silicon-based material and the electrolyte, and the SEI film formed on the coating is thin and stable. In addition, there is a metal layer or metal particles between the nano-sheet silicon-based material and the carbon coating. The good conductivity of the metal can compensate for the poor conductivity of silicon. This can make the silicon negative electrode material of the present application have excellent electrochemical performance, a specific capacity of more than 1000mAh / g, and excellent rate performance.

[0024] The nano-sheet silicon-based material refers to a material whose core is a silicon-based material, which is a sheet-like structure and has a thickness of nanometer level.

[0025] Optionally, the nanosheet-shaped silicon-based material includes one or more of silicon nanosheets (the material is silicon alone), silicon alloy nanosheets (the material is silicon alloy), and silicon monoxide nanosheets (the material is silicon monoxide).

[0026] Furthermore, the silicon alloy includes one or more of silicon-aluminum alloy, silicon-magnesium alloy, and silicon-ferroalloy.

[0027] In an optional embodiment of the present application, the silicon nanosheet has a thickness of 5-100 nm and a planar dimension of 100-2000 nm. For example, the thickness of the silicon nanosheet is 5 nm, 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, or 100 nm, and the planar dimension of the silicon nanosheet is 100 nm, 200 nm, 400 nm, 800 nm, 1200 nm, 1600 nm, or 2000 nm.

[0028] In an optional embodiment of the present application, the metal layer has a thickness of 1-20 nm. If the metal layer has a thickness of 5-20 nm, the metal layer has a layered structure. If the metal layer has a thickness of 1-5 nm, the metal layer will be discontinuous, and the metal layer can be considered as a nano-granular structure. For example, the metal layer has a thickness of 1 nm, 2 nm, 4 nm, 8 nm, 12 nm, 16 nm, or 20 nm.

[0029] In an optional embodiment of the present application, the carbon coating layer has a thickness of 2-20 nm. When the carbon coating layer is thicker (e.g., 5-20 nm), it can form a distinct layer structure. When the carbon coating layer is thinner (e.g., 2-5 nm), the carbon coating layer may not completely cover the metal layer or nano-sheet silicon-based material. For example, the carbon coating layer has a thickness of 2 nm, 4 nm, 5 nm, 8 nm, 12 nm, 16 nm, or 20 nm.

[0030] In an optional embodiment of the present application, the graphitization degree γ of the carbon coating layer satisfies 0.3≦γ≦1, where γ=(0.344-d 002 ) / (0.344-0.3354), d 002 The graphitization degree γ is the nanometer-to-nanolayer spacing of the carbon coating on the 002 crystal plane. A graphitization degree γ in the range of 0.3-1 indicates a high degree of graphitization, which can lead to higher efficiency and cycle performance of the silicon anode material. For example, the graphitization degree γ is 0.3, 0.4, 0.5, 0.6, 0.8, or 1.0.

[0031] In an optional embodiment of the present application, the metal in the metal layer or metal particles includes one or more of tin, copper, iron, silver, and magnesium. When the metal layer or metal particles are made of tin, the performance of the silicon negative electrode material is better.

[0032] In an optional embodiment of the present application, the weight percentage content of silicon is 70% to 98%, the weight percentage content of metal is 0.5% to 20%, the weight percentage content of carbon is 1.5-20%, and the weight percentage content of oxygen is 0%, 1%, 2%, 4%, 6%, 8% or 10%.

[0033] For example: the weight percentage of silicon is 70%, 74%, 78%, 82%, 86%, 90%, 94% or 98%; the weight percentage of tin is 0.5%, 1%, 2%, 4%, 8%, 12%, 16% or 20%; the weight percentage of carbon is 1.5%, 3%, 5%, 8%, 10%, 12%, 14%, 16%, 18% or 20%; the weight percentage of oxygen is 0% to 10%.

[0034] After the silicon negative electrode material is mixed with a solvent, a conductive additive and a binder, a negative electrode slurry can be formed. The negative electrode slurry is coated on a negative electrode current collector and dried to form a negative electrode sheet.

[0035] After the negative electrode sheet is combined with the positive electrode sheet and the separator, an electrode group is formed. The electrode group is placed in a shell and injected with electrolyte to form a lithium-ion secondary battery.

[0036] The negative electrode sheet, the positive electrode sheet and the solid electrolyte are combined to form a lithium-ion solid-state battery. The preparation method of the above-mentioned silicon negative electrode material comprises:

[0037] S110, taking a granular silicon-based material, a polymer compound, a metal salt and a solvent, mixing and then grinding, so that the granular silicon-based material is converted into a nano-sheet silicon-based material, and then drying to obtain a precursor.

[0038] As an example, the granular silicon-based material includes one or more of silicon particles, silicon alloy particles, and silicon monoxide particles. The silicon alloy includes one or more of silicon-aluminum alloy, silicon-magnesium alloy, and silicon-ferroalloy.

[0039] The silicon particles can be single crystal silicon particles, microcrystalline silicon particles, or polycrystalline silicon particles. In some embodiments of the present application, single crystal silicon particles are used, as they are more conducive to forming silicon nanosheets. The silicon particles have a particle size of less than or equal to 1 μm. Most silicon particles are nanometer-sized, which facilitates the formation of sheets after grinding.

[0040] As an example, the polymer compound includes one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl butyral, and polyethylene glycol.

[0041] The solvent includes at least one of water, methanol, ethanol, propanol, isopropanol, butanol, acetone, isopropyl alcohol, ether, n-hexane, n-heptane, N-methylpyrrolidone and ethylene glycol.

[0042] The metal salt includes one or more of tin salt, iron salt, copper salt, and nickel salt. The metal salt only needs to be soluble in the solvent.

[0043] For example, in some embodiments, the solvent is ethanol.

[0044] The nanosheet-shaped silicon-based material includes one or more of silicon nanosheets, silicon alloy nanosheets, and silicon monoxide nanosheets. The silicon alloy includes one or more of silicon-aluminum alloy, silicon-magnesium alloy, and silicon-iron alloy. Optionally, the silicon nanosheet has a thickness of 5-100 nm and a planar dimension of 100-2000 nm.

[0045] Optionally, the mass ratio of silicon particles to metal salt in the precursor is 0.5% to 20%, and the weight percentage of carbon is 1.5-20%.

[0046] S120 , carbon-coating the precursor. For example, chemical vapor deposition is performed on the precursor using an organic gas to coat the precursor with carbon. During the chemical vapor deposition process, the organic gas can react with the metal salt to generate carbon.

[0047] The organic gas can be decomposed into carbon after being catalyzed by the aforementioned metal salt. As an example, the organic gas includes at least one of acetylene, methane, toluene, propylene and ethylene; for example, the organic gas is acetylene.

[0048] In the embodiments of the present application, the amount of coated carbon can be set according to specific needs. For example, the thickness of the carbon coating can be deposited according to the final performance requirements of the silicon negative electrode material. This application is not limited. For example, in some embodiments, the carbon coating layer accounts for 4-7wt% of the silicon negative electrode material.

[0049] The preparation method of the present application utilizes metal salts to decompose organic gases to deposit carbon on the surface of the precursor. This method can generate a uniform and dense carbon layer on the surface containing nano-sheet silicon-based materials. The carbon layer can effectively avoid direct contact between the nano-sheet silicon-based materials and the electrolyte, and the SEI film formed on the coating layer is thin and stable. In addition, metal salts react with organic gases to generate metal, and the metal is located between the flaky silicon-based material and the coated carbon layer. The good electrical conductivity of the metal can make up for the poor electrical conductivity of silicon. The silicon negative electrode material prepared by this method has excellent electrochemical properties, a specific capacity of more than 1500mAh / g, and excellent rate performance.

[0050] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0051] Example 1

[0052] This embodiment provides a silicon negative electrode material, which is mainly prepared by the following steps:

[0053] (1) Weigh 1.5 kg of single-crystal silicon powder with a particle size of 5-10 μm, 30 g of PVP (polyvinyl pyrrolidone), and 120 g of SnC2O4 into 15 L of ethanol and homogenize and disperse them in a homogenizer for 30 min to obtain a suspension;

[0054] (2) The suspension was placed in a coarse grinder and sand-milled for 1 hour, then transferred to a fine grinder and sand-milled for 1 hour, and then dried to obtain metal salt-doped silicon nanosheets;

[0055] (3) The metal salt-doped silicon nanosheets were placed in a rotary kiln and heated from room temperature to 700°C under a nitrogen atmosphere with an N2 flow rate of 600 sccm. Then, C2H2 was introduced with a flow rate of 600 sccm and a heating rate of 10°C / min. The temperature was maintained at 680°C for 60 min to obtain a silicon negative electrode material.

[0056] 4) The silicon anode material was tested, and its thickness was 30 nm, length was 500 nm, and width was 300 nm. Silicon alone accounted for 87.6 wt% of the silicon anode material; tin alone accounted for 5.1 wt% of the silicon anode material; the carbon coating layer accounted for 5.7 wt% of the silicon anode material; and oxygen accounted for 1.1 wt% of the silicon anode material.

[0057] Example 2

[0058] This embodiment provides a silicon negative electrode material. Please refer to Example 1. This embodiment is the same as step 2) of Example 1. The remaining steps of this embodiment are as follows:

[0059] 1) Weigh 1.5 kg of single-crystal silicon powder with a particle size of 5-10 μm, 30 g of PVP (polyvinyl pyrrolidone), and 122 g of FeSO4 into 15 L of ethanol and homogenize and disperse them in a homogenizer for 30 minutes to obtain a suspension;

[0060] 3) The metal salt-doped silicon nanosheets were placed in a rotary kiln and heated from room temperature to 700°C under a nitrogen atmosphere with an N2 flow rate of 600 sccm. C2H2 was then introduced with a flow rate of 600 sccm and a heating rate of 10°C / min. The temperature was maintained at 700°C for 60 min to obtain a silicon negative electrode material.

[0061] 4) The silicon anode material was tested, and its thickness was 30 nm, length was 500 nm, and width was 300 nm. The silicon element accounted for 90.3 wt% of the silicon anode material; the iron element accounted for 2.6 wt% of the silicon anode material; the carbon coating layer accounted for 5.9 wt% of the silicon anode material; and oxygen accounted for 0.9 wt% of the silicon anode material.

[0062] Example 3

[0063] This embodiment provides a silicon negative electrode material. Please refer to Example 2. This embodiment is the same as Step 2) and Step 3) of Example 2. The remaining steps of this embodiment are as follows:

[0064] 1) Weigh 1.5 kg of solar silicon wafer scrap and crush it to 5-10 μm using a crusher. Then, place the 5-10 μm solar silicon wafer scrap, 30 g of PVP, and 80 g of SnC2O4 in 15 L of ethanol and homogenize and disperse them using a homogenizer for 30 minutes.

[0065] 4) The silicon anode material was tested, and its thickness was 30 nm, length was 500 nm, and width was 300 nm. In the silicon anode material, silicon alone accounted for 88.9 wt% of the silicon anode material; tin alone accounted for 2.8 wt% of the silicon anode material; the carbon coating layer accounted for 6.3 wt% of the silicon anode material; iron alone accounted for 0.8 wt% of the silicon anode material; and oxygen accounted for 1.1 wt% of the silicon anode material.

[0066] Example 4

[0067] This embodiment provides a silicon negative electrode material. Please refer to Example 2. This embodiment is the same as Step 2) and Step 3) of Example 2. The remaining steps of this embodiment are as follows:

[0068] 1) Weigh 1.5 kg of single crystal silicon powder with a particle size of 5-10 μm, 30 g of PVP and 122 g of FeSO4 into 15 L of ethanol and homogenize and disperse them in a homogenizer for 30 minutes;

[0069] 4) The silicon anode material was tested, and its thickness was 35 nm, length was 550 nm, and width was 320 nm. In the silicon anode material, silicon alone accounted for 88.3 wt% of the silicon anode material; tin alone accounted for 4.8 wt% of the silicon anode material; the carbon coating layer accounted for 5.3 wt% of the silicon anode material; and oxygen accounted for 0.8 wt% of the silicon anode material.

[0070] Example 5

[0071] This embodiment provides a silicon negative electrode material. Please refer to Example 2. This embodiment is the same as Step 2) and Step 3) of Example 2. The remaining steps of this embodiment are as follows:

[0072] 1) Weigh 1.5 kg of single crystal silicon powder with a particle size of 5-10 μm, 30 g of PVP and 122 g of FeSO4 into 15 L of ethanol and homogenize and disperse them in a homogenizer for 30 minutes;

[0073] 4) The silicon anode material was tested, and its thickness was 30 nm, length was 500 nm, and width was 300 nm. In the silicon anode material, silicon alone accounted for 90.3 wt% of the silicon anode material; iron alone accounted for 2.6 wt% of the silicon anode material; the carbon coating layer accounted for 5.9 wt% of the silicon anode material; and oxygen accounted for 0.9 wt% of the silicon anode material.

[0074] Example 6

[0075] This embodiment provides a silicon negative electrode material. Please refer to Example 2. This embodiment is the same as Step 2) and Step 3) of Example 2. The remaining steps of this embodiment are as follows:

[0076] (1) Weigh 1.5 kg of polysilicon powder with a particle size of 5-10 μm, 30 g of PVP, and 122 g of CuSO4 into 15 L of ethanol and homogenize and disperse them in a homogenizer for 30 min;

[0077] (2) The suspension was placed in a coarse grinder and sand-milled for 1 hour, then transferred to a fine grinder and sand-milled for 1 hour, and then dried to obtain metal salt-doped silicon nanosheets;

[0078] (3) The metal salt-doped silicon nanosheets were placed in a rotary kiln and heated from room temperature to 380°C under a nitrogen atmosphere with an N2 flow rate of 600 sccm. Then, C2H2 was introduced with a flow rate of 600 sccm and a heating rate of 10°C / min. The temperature was maintained at 680°C for 60 min to obtain a silicon negative electrode material.

[0079] 4) The silicon anode material was tested and found to have a thickness of 30 nm, a length of 580 nm, and a width of 310 nm. In the silicon anode material, silicon alone accounted for 88.3 wt% of the silicon anode material; tin alone accounted for 4.8 wt% of the silicon anode material; the carbon coating layer accounted for 5.3 wt% of the silicon anode material; and oxygen accounted for 0.8 wt% of the silicon anode material.

[0080] Example 7

[0081] This embodiment provides a silicon negative electrode material. Please refer to Example 2. This embodiment is the same as Step 2) and Step 3) of Example 2. The remaining steps of this embodiment are as follows:

[0082] 1) Weigh 1.5 kg of microcrystalline silicon powder with a particle size of 5-10 μm, 30 g of PVP and 122 g of FeSO4 into 15 L of ethanol and homogenize and disperse them in a homogenizer for 30 minutes;

[0083] 4) Testing the silicon anode material revealed a thickness of 28 nm, a length of 690 nm, and a width of 250 nm. Silicon alone accounted for 87.3 wt% of the silicon anode material; copper alone accounted for 4.3 wt% of the silicon anode material; the carbon coating accounted for 4.4 wt% of the silicon anode material; and oxygen accounted for 1.2 wt% of the silicon anode material.

[0084] Comparative Example 1

[0085] This comparative example provides a silicon negative electrode material. This comparative example is the same as step 2) and step 3) of Example 2. The remaining steps of this comparative example are as follows:

[0086] 1) Weigh 1.5 kg of single crystal silicon powder with a particle size of 5-10 μm and 30 g of PVP (polyvinyl pyrrolidone) and homogenize and disperse them in a homogenizer for 30 minutes to obtain a suspension.

[0087] 4) The silicon negative electrode material was tested, and its thickness was 59 nm, its length was 820 nm, and its width was 330 nm. In the silicon negative electrode material, silicon alone accounted for 95.3 wt% of the silicon negative electrode material; the carbon coating layer accounted for 3.4 wt% of the silicon negative electrode material; and oxygen accounted for 1.3 wt% of the silicon negative electrode material.

[0088] Comparative Example 2

[0089] This comparative example provides a silicon negative electrode material, and directly tests the original solar silicon.

[0090] Test example

[0091] The silicon negative electrode material prepared in the above examples and comparative examples was mixed evenly with super-p (conductive carbon black) and sodium alginate in a mass ratio of 8:1:1 using a stirrer, and then evenly coated on a copper foil. The mixture was placed in a vacuum drying oven and vacuum dried at 120°C for 12 hours, and then taken out to form an electrode sheet.

[0092] A lithium sheet was used as the counter electrode, the electrolyte was a 1 mol / l LiPF6 solution in EC+DMC (volume ratio of 1:1), and a PP / PE / PP three-layer membrane was used as the separator (purchased from Celgard, USA). CR2032 button cells were assembled in an argon atmosphere glove box.

[0093] The assembled batteries were electrochemically tested using a Blue Electric tester (purchased from Wuhan Blue Electric Electronics Co., Ltd.). Cycling was performed at a rate of 0.05C for one week and then at a rate of 0.2C for 99 cycles. The charge and discharge cutoff voltage range was 0.01V to 1.0V. The test results are shown in Table 1.

[0094] Table 1

[0095]

[0096] As can be seen from Table 1, in Comparative Example 1, the silicon negative electrode material does not contain a single metal, and its cycle stability is poor; in Comparative Example 2, the silicon negative electrode material does not contain a single metal and a carbon coating layer, and its cycle stability is even worse. The silicon negative electrode material provided in the embodiments of the present application contains a single metal (tin, iron, or copper) and a carbon layer coated on the silicon surface, which can improve the material's cycle stability and performance.

[0097] Figure 1 and Figure 2 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the negative electrode material provided in Example 1 of the present application respectively show that the silicon-based material is silicon nanosheets. Figure 1 (SEM) shows that the thickness of silicon nanosheets is 5 to 100 nm; the plane size is 100 to 2000 nm. Figure 2 (TEM) shows that the thickness of the first coating layer on the surface of the silicon-based material is 1-5nm, and the thickness of the second carbon coating layer is 2-10nm.

[0098] Figure 3 The electrochemical cycle diagram of the half-cell prepared from the negative electrode material provided in Example 1 of the present application is shown in FIG. Figure 3It can be seen that the first-week charging capacity of the half-cell provided in Example 1 is as high as 1396.9 mAh / g, and the cycle capacity retention rate after 100 weeks is 81.26%, showing excellent electrochemical performance.

[0099] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A silicon negative electrode material, characterized in that: It includes: Silicon nanosheets and a carbon coating layer, with a metal layer between the carbon coating layer and the silicon nanosheets; The preparation method of the silicon negative electrode material comprises: S110, mixing and grinding single crystal silicon particles, a polymer compound, a metal salt, and a solvent to convert the single crystal silicon particles into the silicon nanosheets, and then drying to obtain a precursor; S120, performing chemical vapor deposition on the precursor using an organic gas, wherein the organic gas reacts with the metal salt to form the carbon coating layer and the metal layer; The thickness of the silicon nanosheet is 5-100 nm, and the plane size is 100-2000 nm; the thickness of the metal layer is 1-20 nm.

2. The silicon negative electrode material according to claim 1, characterized in that The thickness of the carbon coating layer is 2-20 nm.

3. The silicon negative electrode material according to claim 1 or 2, characterized in that: The graphitization degree γ of the carbon coating layer satisfies 0.3≦γ≦1, where γ=(0.344-d 002 ) / (0.344-0.3354), d 002 is the nanolayer spacing of the carbon coating layer on the 002 crystal plane.

4. The silicon negative electrode material according to claim 1 or 2, characterized in that The metal in the metal layer includes one or more of tin, copper, iron, silver, and magnesium.

5. The silicon negative electrode material according to claim 1, characterized in that The weight percentage of silicon is 70% to 98%, the weight percentage of metal is 0.5% to 20%, the weight percentage of carbon is 1.5-20%, and the weight percentage of oxygen is 0% to 10%.

6. A battery negative electrode sheet, characterized in that: The battery negative electrode sheet comprises the silicon negative electrode material according to any one of claims 1 to 5.

7. A lithium ion secondary battery, characterized in that: The lithium-ion secondary battery comprises the battery negative electrode sheet according to claim 6.

8. A lithium-ion solid-state battery, characterized in that: The lithium-ion solid-state battery comprises the battery negative electrode sheet according to claim 6.

Images