Silicon negative electrode material and preparation method, device and application thereof

Abstract

The application belongs to the technical field of secondary batteries, and particularly relates to a silicon negative electrode material, a preparation method and device thereof, and application thereof. In the application, a carrier after deposition of silicon is treated by cold plasma, so that crystalline silicon on the carrier is converted into amorphous silicon, and the electrical performance of the silicon negative electrode material is improved, especially the cycle capacity retention rate. In the application, a preparation device including a silicon deposition unit and a cold plasma reaction unit is provided, the process control difficulty of a silane deposition process is reduced, the operation flexibility is greatly improved, and the production capacity can be continuously expanded.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a silicon anode material and its preparation method, apparatus and application. Background Technology

[0002] Silicon-carbon anodes exhibit good stability, small volume change, and excellent conductivity, leading to rapid industrialization progress in recent years. Among existing technologies, chemical vapor deposition (CVD) offers the best crystal structure and doping concentration for silicon-carbon anode materials, resulting in a high overall cost-effectiveness in terms of product quality and process flow. The commonly used CVD method uses porous carbon materials as a deposition carrier. At a specific temperature, silanes are adsorbed into the pores of the porous carbon and decompose to form a carbon-embedded silicon composite material, which is then coated with carbon to obtain the silicon-carbon anode material. However, in actual preparation, silanes are not completely adsorbed into the pores before decomposition; some are deposited on the carrier surface and decompose to form a silicon layer. This surface-deposited silicon layer tends to grow into crystalline silicon, affecting the electrical performance of the material in its final application. Furthermore, as the reactor scales up, the uneven temperature distribution within the reactor intensifies, significantly increasing the number of locally overheated areas. This phenomenon is severely exacerbated, negatively impacting the product quality and stability after large-scale mass production of silicon-carbon anode materials, and is one of the main obstacles to further expanding the production capacity of existing reaction equipment. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art, such as the tendency of the silicon layer deposited on the surface of the carrier to grow into crystalline silicon when preparing silicon anode materials, which affects the electrical performance of the material in the final application, and the fact that the existing reaction equipment is not conducive to expanding production capacity, so as to provide a silicon anode material and its preparation method, apparatus and application.

[0004] To this end, the present invention provides the following technical solution.

[0005] The method for preparing silicon anode material provided by the present invention includes the following steps: S1: depositing silicon on a support to obtain composite material particles; S2: treating the composite material particles obtained in S1 with cold plasma.

[0006] Optionally, in step S2, when using cold plasma to treat the composite material particles obtained in S1, the temperature is 0–500°C. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 0°C, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C; or any range of two values, for example, 20–30°C, 70–80°C, 130–140°C, 170–190°C, 240–260°C, 320–330°C, 380–390°C, 450–470°C.

[0007] Optionally, the discharge gas used in the cold plasma treatment step is an inert gas, including but not limited to the gases in the embodiments and the following gases: helium, neon, krypton, and xenon.

[0008] In practical applications, the method for preparing silicon anode materials provided by this invention allows for the selection of the discharge power of cold plasma treatment within a conventional range without particular limitations. Optionally, the discharge power of cold plasma treatment can be 1–50 kW. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 1 kW, 5 kW, 12 kW, 17 kW, 20 kW, 25 kW, 30 kW, 35 kW, 40 kW, 45 kW, 50 kW, or any range of two values, such as 4–6 kW, 10–11 kW, 18–19 kW, 22–23 kW, 27–20 kW, etc. 8kW, 31-32kW, 35-36kW, 42-43kW, 48-49kW; there is no particular limitation on the residence time for cold plasma treatment of composite material particles. When the discharge power of cold plasma treatment is low, the residence time can be appropriately increased. Optionally, the residence time is 0.75-75 min, and specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 1 min, 5 min, 10 min, 15 min, 20 min, 25 min, 31 min, 37 min, 40 min. n, 45min, 50min, 55min, 60min, 65min, 70min, 73min, or any range of two values, for example, 0.75~1.5min, 7~8min, 12~13min, 18~19min, 24~26min, 31~32min, 35~36min, 42~43min, 47~48min, 54~55min, 58~59min, 64~66min, 71~72min.

[0009] Optionally, in step S1, silicon is deposited using the CVD method.

[0010] Optionally, the silicon deposition temperature is 350–650°C; specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, or any range of two values, such as 380–390°C, 450–470°C, 510–530°C, 580–590°C, 610–620°C. The silicon deposition time is 1–15 hours; specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 2 hours, 3 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, or any range of two values, such as 1–2 hours, 4–5 hours, 7–8 hours, 11–12 hours, 14–15 hours.

[0011] Optionally, the silicon source used for silicon deposition is a silane and / or a group-substituted silane; preferably, in step S1, the silicon source used includes at least one of silane, ethyl silane, methyl silane, methylchlorosilane, and dichlorosilane.

[0012] Optionally, the carrier used for silicon deposition is a carbon-based material; preferably, the carbon-based material includes at least one of porous carbon, carbon nanotubes, carbon aerogel, and graphene.

[0013] Optionally, step S3 is also included: carbon coating the composite material particles treated in step S2.

[0014] Optionally, in step S3, carbon coating is performed using the CVD method.

[0015] Optionally, the carbon coating temperature is 450–800°C, with specific examples including but not limited to the point values ​​in the embodiments and the following point values: 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, or any range of two values, such as 450–470°C, 510–530°C, 580–590°C, 610–620°C, 670–680°C, 730–740°C, 790–800°C. The carbon coating time is 0.5–5 hours, with specific examples including but not limited to the point values ​​in the embodiments and the following point values: 2 hours, 3 hours, 4 hours, 5 hours, or any range of two values, such as 0.5–1 hour, 2–3 hours, 4–5 hours.

[0016] Optionally, the carbon source used for carbon coating is a hydrocarbon; preferably, the carbon source used includes at least one of acetylene, methane, ethylene, propylene, butadiene, propyne, benzene, toluene, and xylene.

[0017] The apparatus for preparing silicon anode material provided by the present invention includes a silicon deposition unit and a cold plasma reaction unit arranged sequentially; the outlet of the silicon deposition unit is connected to the inlet of the cold plasma reaction unit.

[0018] Preferably, the cold plasma reaction unit includes a cold plasma reaction device and a conveying device disposed inside the cold plasma reaction device; the conveying device is used to convey materials from the feed end to the discharge end of the cold plasma reaction unit.

[0019] Optionally, the cold plasma reaction device is a dielectric barrier discharge plasma reaction device;

[0020] Optionally, the conveying device includes a transmission belt, a transmission reel, and a power unit; the power unit drives the transmission reel to move, and the transmission reel in turn drives the transmission belt to move.

[0021] Optionally, the dielectric barrier discharge plasma reaction device includes a reaction chamber, and a first electrode, a second electrode, and a dielectric barrier layer disposed inside the reaction chamber.

[0022] Optionally, the first electrode and the second electrode are arranged opposite to each other, and the material passes between the first electrode and the second electrode through the reaction chamber.

[0023] Optionally, the conveyor belt is located between the first and second electrodes of the dielectric barrier discharge plasma reactor. The material is placed on the conveyor belt and reacts as it moves through the dielectric barrier discharge plasma reactor, ensuring the continuous progress of the reaction.

[0024] Optionally, the dielectric barrier layer is disposed on the side of the first electrode near the second electrode.

[0025] Preferably, it also includes a carbon coating unit; the outlet of the cold plasma reaction unit is connected to the inlet of the carbon coating unit.

[0026] Optionally, the outlet of the silicon deposition unit is located above the inlet of the cold plasma reaction unit, and the outlet of the cold plasma reaction unit is located above the inlet of the carbon coating unit. The material moves between the units by gravity, saving energy.

[0027] The method for preparing silicon anode material provided by the present invention, using the above-mentioned preparation apparatus, includes the following steps: depositing silicon on a carrier in a silicon deposition unit to obtain composite material particles; transferring the composite material particles from the outlet of the silicon deposition unit to the inlet of the cold plasma reaction unit; and subjecting the composite material particles to cold plasma treatment in the cold plasma reaction unit.

[0028] Optionally, the method further includes the step of conveying the cold plasma-treated composite material particles from the outlet of the cold plasma reaction unit to the inlet of the carbon coating unit, and then performing carbon coating on the cold plasma-treated composite material particles in the carbon coating unit.

[0029] Optionally, a conveying device can be used to convey the composite material particles from the feed port of the cold plasma reaction unit to the discharge port of the cold plasma reaction unit.

[0030] The present invention provides a silicon anode material prepared by the above preparation method or the above preparation apparatus.

[0031] The present invention also provides an electrode sheet comprising the aforementioned silicon anode material. Other components and preparation methods of the electrode sheet are conventional in the art, and the present invention does not specifically limit them.

[0032] The present invention also provides a secondary battery, comprising the aforementioned silicon anode material or electrode sheet. Specifically, the secondary battery is a lithium-ion battery, and the other components and preparation methods of the lithium-ion battery are conventional in the art, and the present invention does not specifically limit them.

[0033] The beneficial effects of this invention are:

[0034] The present invention provides a method for preparing silicon anode materials, comprising the following steps: S1: depositing silicon on a support to obtain composite material particles; S2: treating the composite material particles obtained in S1 with cold plasma. This preparation method can avoid the formation of crystalline silicon in the silicon anode material, thereby improving its electrical performance, especially its cycle performance. In step S1, during silicon deposition on the support, some silicon will deposit on the surface of the support to form a crystalline silicon layer; while in step S2, the composite material particles obtained in S1 are treated with cold plasma. The high-energy particles in the cold plasma bombardment destroy the lattice structure of the crystalline silicon deposited on the surface of the support, transforming it into amorphous silicon, thereby improving the electrical performance of the material, especially its cycle capacity retention.

[0035] The method for preparing silicon anode material provided by the present invention further includes step S3: carbon coating the treated composite material particles obtained in step S2 to obtain silicon anode material. The surface of the particles treated by cold plasma has higher surface energy, which can form a stronger adsorption effect on the carbon source during the carbon coating process, which is beneficial to improving the carbon coating efficiency, making the silicon surface better covered by carbon, and thus improving the first coulombic efficiency of the prepared battery.

[0036] The apparatus for preparing silicon anode materials provided by this invention includes a silicon deposition unit and a cold plasma reaction unit. The cold plasma reaction unit is introduced into the apparatus for preparing silicon anode materials to convert the crystalline silicon layer generated in the silicon deposition process into an amorphous state, reducing the process control difficulty of the silane deposition process, significantly improving its operational flexibility, and enabling continuous expansion of production capacity.

[0037] The silicon anode material preparation apparatus provided by the present invention also includes a carbon coating unit, which facilitates the direct carbon coating of composite material particles treated with cold plasma, thereby achieving integrated operation.

[0038] The silicon anode material preparation apparatus provided by the present invention includes a cold plasma reaction unit comprising a cold plasma reaction device and a conveying device disposed inside the cold plasma reaction device, which can realize the continuous preparation of silicon anode materials. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the apparatus for preparing the silicon anode material using the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1-Reaction chamber; 2-First electrode; 3-Second electrode; 4-Dielectric barrier layer; 5-Drive reel; 6-Drive belt; 7-Cold plasma reaction unit outlet; 8-Cold plasma reaction unit inlet; 9-Carbon coating unit; 10-Carbon coating unit inlet; 11-Silicon deposition unit; 12-Silicon deposition unit outlet. Detailed Implementation

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

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

[0045] Example 1

[0046] This embodiment provides a device for preparing silicon anode materials, as described below. Figure 1 Detailed explanation.

[0047] The apparatus for preparing silicon anode material according to this embodiment of the invention includes a silicon deposition unit 11 and a cold plasma reaction unit; the outlet 12 of the silicon deposition unit is connected to the inlet 8 of the cold plasma reaction unit. In preparing the silicon anode material, the carrier and silicon source first undergo a silicon deposition reaction in the silicon deposition unit 11, and then enter the cold plasma reaction unit for further reaction to obtain the silicon anode material.

[0048] In some embodiments, the cold plasma reaction unit includes a cold plasma reaction apparatus and a conveying device disposed inside the cold plasma reaction apparatus; the conveying device is used to convey materials from the feed end to the discharge end of the cold plasma reaction unit.

[0049] In some embodiments, the cold plasma reaction device used is a dielectric barrier discharge plasma reaction device, which includes a reaction chamber 1, a first electrode 2, a second electrode 3 and a dielectric barrier layer 4 disposed inside the reaction chamber 1; the first electrode 2 and the second electrode 3 are disposed opposite to each other, and the material passes through the reaction chamber 1 between the first electrode 2 and the second electrode 3; the dielectric barrier layer 4 is disposed on the side of the first electrode 2 near the second electrode 3.

[0050] In some embodiments, the conveying device includes a transmission belt 6, a transmission reel 5, and a power unit; the power unit drives the transmission reel 5 to move, and the transmission reel 5 in turn drives the transmission belt 6 to move. The transmission belt 6 is located between the first electrode 2 and the second electrode 3 of the dielectric barrier discharge plasma reactor. The material is placed on the transmission belt 6, and as the transmission belt 6 moves, it passes through the dielectric barrier discharge plasma reactor to undergo a reaction, ensuring the continuous progress of the reaction.

[0051] In some embodiments, a carbon coating unit 9 is also included. The outlet 7 of the cold plasma reaction unit is connected to the inlet 10 of the carbon coating unit. The obtained silicon anode material is fed into the carbon coating unit 9 for carbon coating to obtain carbon-coated silicon anode material.

[0052] In some embodiments, the silicon deposition unit outlet 12 is located above the cold plasma reaction unit inlet 8, and the cold plasma reaction unit outlet 7 is located above the carbon coating unit inlet 10. The material moves between the units by gravity, saving energy.

[0053] Example 2

[0054] This embodiment provides a method for preparing a silicon anode material, using... Figure 1 The apparatus described above is used for preparation, and the specific steps are as follows:

[0055] (1) Take 1 kg of carbon aerogel carrier (porosity approximately 1 cm). 3 / g, specific surface area approximately 2000m²2 / g, pore size 8~15nm), using silane as the silicon source, flow rate 3L / min, under normal pressure and 480℃ conditions, were deposited in silicon deposition unit 11 for 4h to obtain composite material particles;

[0056] (2) The composite material particles obtained in step (1) are carried by argon gas and enter the plasma reaction unit inlet 8 through the silicon deposition unit outlet 12. They fall onto the transmission belt 6. The power unit drives the transmission roller 5 to move, and the transmission roller 5 drives the transmission belt 6 to move. Finally, the transmission belt 6 drives the composite material particles to move in the reaction chamber 1 at a speed of 0.05 m / min. The particles are processed through the plasma discharge area between the first electrode 2 and the dielectric barrier layer 4 and the second electrode 3. The environment is normal temperature and pressure, the discharge power is 10 kW, the discharge gas is argon gas, the discharge width is 0.5 m, and the discharge length is 1.5 m.

[0057] (3) The composite material particles processed in step (2) are fed into the carbon coating unit inlet 10 through the plasma reaction unit outlet 7. Acetylene is used as the carbon source, the flow rate is 1L / min, and the reaction is carried out in the carbon coating unit 9 for 1h under normal pressure and 600℃ to obtain silicon anode material.

[0058] Example 3

[0059] This embodiment provides a method for preparing a silicon anode material, using the same apparatus as in Embodiment 2.

[0060] The specific preparation steps are as follows:

[0061] (1) Take 1.5 kg of porous carbon support (porosity approximately 0.9 cm). 3 / g, specific surface area approximately 1900m² 2 The composite material particles were obtained by depositing methylsilane as the silicon source (with a pore size of 4-10 nm) in silicon deposition unit 11 for 5 h at a flow rate of 6 L / min and a normal pressure of 590 °C for 5 h.

[0062] (2) The composite material particles obtained in step (1) are carried by argon gas and enter the plasma reaction unit inlet 8 through the silicon deposition unit outlet 12. They fall onto the transmission belt 6. The power unit drives the transmission roller 5 to move, and the transmission roller 5 drives the transmission belt 6 to move. Finally, the transmission belt 6 drives the composite material particles to move in the reaction chamber 1 at a speed of 0.02 m / min. The particles are processed through the plasma discharge area between the first electrode 2 and the dielectric barrier layer 4 and the second electrode 3. The environment is normal temperature and pressure, the discharge power is 10 kW, the discharge gas is argon gas, the discharge width is 0.5 m, and the discharge length is 1.5 m.

[0063] (3) The composite material particles processed in step (2) are fed into the carbon coating unit inlet 10 through the plasma reaction unit outlet 7. Butadiene is used as the carbon source and the flow rate is 1L / min. The reaction is carried out in the carbon coating unit 9 for 0.5h under normal pressure and 650℃ to obtain silicon anode material.

[0064] Example 4

[0065] This embodiment provides a method for preparing a silicon anode material, using the same apparatus as in Embodiment 2.

[0066] The specific preparation steps are as follows:

[0067] (1) Take 2 kg of multi-walled carbon nanotube carrier ((0.7 cm) 3 / g, 1600m 2 / g, pore size 2-5nm), using dichlorosilane as the silicon source, under normal pressure and 620℃ conditions with a flow rate of 5L / min, the composite material particles were deposited in silicon deposition unit 11 for 5h to obtain composite material particles;

[0068] (2) The composite material particles obtained in step (1) are carried by argon gas and enter the plasma reaction unit inlet 8 through the silicon deposition unit outlet 12. They fall onto the transmission belt 6. The power unit drives the transmission roller 5 to move, and the transmission roller 5 drives the transmission belt 6 to move. Finally, the transmission belt 6 drives the composite material particles to move in the reaction chamber 1 at a speed of 0.02 m / min. The particles are processed through the plasma discharge area between the first electrode 2 and the dielectric barrier layer 4 and the second electrode 3. The environment is normal temperature and pressure, the discharge power is 10 kW, the discharge gas is argon gas, the discharge width is 0.5 m, and the discharge length is 1.5 m.

[0069] (3) The composite material particles processed in step (2) are fed into the carbon coating unit inlet 10 through the plasma reaction unit outlet 7. Toluene is used as the carbon source, the flow rate is 1L / min, and the reaction is carried out in the carbon coating unit 9 for 0.5h under normal pressure and 680℃ to obtain silicon anode material.

[0070] Comparative Example 1

[0071] This comparative example provides a method for preparing a silicon anode material, the specific steps of which are as follows:

[0072] (1) Take 1 kg of carbon aerogel carrier, use silane as silicon source, flow rate 3 L / min, and deposit it in silicon deposition unit 11 for 4 h at atmospheric pressure 480℃ to obtain composite material particles.

[0073] (2) Using acetylene as the carbon source, with a flow rate of 1 L / min, the above composite material particles were carbon coated in carbon coating unit 9 at atmospheric pressure and 600 °C for 1 h to obtain silicon anode material.

[0074] Comparative Example 2

[0075] This comparative example provides a method for preparing a silicon anode material, the specific steps of which are as follows:

[0076] (1) Take 1.5 kg of porous carbon support, use methylsilane as silicon source, flow rate 6 L / min, and deposit it in silicon deposition unit 11 for 5 h under normal pressure and 590℃ to obtain composite material particles;

[0077] (2) Using butadiene as the carbon source, with a flow rate of 1 L / min, the above composite material particles were carbon coated in carbon coating unit 9 at atmospheric pressure and 650 °C for 0.5 h to obtain silicon anode material.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing a silicon anode material, the specific steps of which are as follows:

[0080] (1) Take 2 kg of carbon nanotube carrier, use dichlorosilane as silicon source, and deposit it in silicon deposition unit 11 for 5 h at a flow rate of 5 L / min and atmospheric pressure of 620 °C to obtain composite material particles.

[0081] (2) Using toluene as the carbon source, with a flow rate of 1 L / min, the above composite material particles were carbon coated in carbon coating unit 9 at atmospheric pressure and 680 °C for 0.5 h to obtain silicon anode material.

[0082] Test Example 1

[0083] The silicon anode material obtained in the examples and comparative examples was used to prepare a CR2032 coin cell. The specific steps are as follows:

[0084] Silicon anode material, conductive additive carbon black, and binder (sodium carboxymethyl cellulose and styrene-butadiene rubber in a 1:1 mass ratio) were weighed at a mass ratio of 94:2:4. A slurry was prepared using a pulping machine, and the slurry was coated using a 250μm doctor blade on a coating machine at 30mm / s. After baking at 80℃ for 2 hours, the anode was obtained. A Celgard 2400 polypropylene separator was used, and lithium metal sheets were selected as the positive electrode. The electrolyte was a LiPF6 system electrolyte [a 1mol / L LiPF6 solution with an EC / DC 1:1 (volume ratio) mixture as the solvent]. The anode and the prepared material were assembled into a CR2032 coin cell in a glove box.

[0085] The prepared CR2032 coin cells were subjected to constant current charge-discharge tests using a charge-discharge apparatus. The discharge cutoff voltage was 0.005V, and the charge cutoff voltage was 2V. The first week of charge-discharge testing was conducted at a current density of 1C / 10C to obtain the charge-discharge capacity and initial coulombic efficiency of the material. The test results are shown in Table 1.

[0086] Test Example 2

[0087] The silicon anode material obtained in the examples and comparative examples was used to prepare a complete battery cell. The specific steps are as follows:

[0088] Silicon anode material was prepared by mixing it with graphite to form a composite with a specific capacity of 450 mAg / h. The composite, conductive additive carbon black, and binder (sodium carboxymethyl cellulose and styrene-butadiene rubber in a 1:1 mass ratio) were weighed at a ratio of 94:2:4 to prepare a slurry. This slurry was coated onto a current collector to obtain the anode sheet. Active material LiCoO2, conductive carbon black, and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a weight ratio of 96.7:1.7:1.6. This mixture was then coated onto an Al foil, dried, and cold-pressed to obtain the positive electrode sheet. Using a porous PE polymer film as a separator, the positive electrode sheet, separator, and anode sheet were stacked sequentially, with the separator acting as a separator between the positive and negative electrodes. The resulting coil was then wound to obtain the bare battery cell. The bare battery cell was placed in its outer packaging and injected with electrolyte to prepare a 404865 model battery cell (positive electrode areal density 17.9 g / cm³). 2 The negative electrode surface density is 7.0 g / cm³. 2 The electrolyte used is Xinzhoubang LBC421B10 and encapsulated. After formation, degassing, edge trimming and other processes, the full cell is obtained.

[0089] The fabricated cells were subjected to constant current charge-discharge tests using a charge-discharge apparatus. The discharge cutoff voltage was 2.75V, and the charging cutoff voltage was 4.2V. Both charge-discharge tests were conducted at a current density of 1C. The capacity retention rate was tested after 100 and 300 full charge cycles. The test results are shown in Table 1.

[0090] Table 1

[0091]

[0092] Based on the test data given in Table 1, Example 2 was compared with Comparative Example 1, Example 3 with Comparative Example 2, and Example 4 with Comparative Example 3 individually. It can be seen that, compared to the comparative examples where carbon coating was applied directly after silicon deposition without cold plasma treatment, the silicon anode material prepared using this invention improves the battery's initial efficiency while maintaining the original specific capacity level. This is a result of the improved carbon coating effect achieved by the preparation method of this invention. Furthermore, it can be seen that the silicon anode material prepared using this invention also significantly improves the overall battery cycle performance. Its advantage in capacity retention is evident after 100 cycles, and the capacity retention remains good after 300 cycles. This is a result of the preparation method provided by this invention effectively solving the crystallization problem during silicon deposition.

[0093] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a silicon anode material, characterized in that, Includes the following steps: S1: Silicon is deposited on a carrier to obtain composite material particles; S2: The composite material particles obtained in S1 are treated with cold plasma; When using cold plasma to treat the composite material particles obtained in S1, the temperature is 0~500℃. The discharge gas used in the cold plasma treatment step is an inert gas.

2. The method for preparing the silicon anode material according to claim 1, characterized in that, The discharge power of cold plasma treatment is 1~50kW.

3. The method for preparing the silicon anode material according to claim 2, characterized in that, The residence time for cold plasma treatment is 0.75~75 min.

4. The method for preparing the silicon anode material according to claim 1, characterized in that, In step S1, silicon is deposited using chemical vapor deposition.

5. The method for preparing the silicon anode material according to claim 4, characterized in that, The temperature for silicon deposition is 350~650℃, and the time is 1~15h.

6. The method for preparing the silicon anode material according to claim 4, characterized in that, The silicon source used for silicon deposition is silane and / or group-substituted silane.

7. The method for preparing the silicon anode material according to claim 6, characterized in that, The silicon source includes at least one of silane, ethylsilane, methylsilane, methylchlorosilane, and dichlorosilane.

8. The method for preparing the silicon anode material according to claim 4, characterized in that, The substrate used for silicon deposition is a carbon-based material.

9. The method for preparing the silicon anode material according to claim 8, characterized in that, The carbon-based material includes at least one of porous carbon, carbon nanotubes, carbon aerogel, and graphene.

10. The method for preparing the silicon anode material according to claim 1, characterized in that, It also includes step S3: carbon coating the composite material particles processed in step S2.

11. The method for preparing the silicon anode material according to claim 10, characterized in that, In step S3, carbon coating is performed using chemical vapor deposition.

12. The method for preparing the silicon anode material according to claim 10, characterized in that, The carbon coating temperature is 450~800℃, and the time is 0.5~5h.

13. The method for preparing the silicon anode material according to claim 10, characterized in that, The carbon source used for carbon coating is a hydrocarbon.

14. The method for preparing the silicon anode material according to claim 13, characterized in that, The carbon source includes at least one of acetylene, methane, ethylene, propylene, butadiene, propyne, benzene, toluene, and xylene.

15. The method for preparing the silicon anode material according to any one of claims 1 to 14, characterized in that, The silicon anode material is prepared using the following apparatus, which includes a silicon deposition unit and a cold plasma reaction unit arranged sequentially; the outlet of the silicon deposition unit is connected to the inlet of the cold plasma reaction unit.

16. The method for preparing the silicon anode material according to claim 15, characterized in that, The cold plasma reaction unit includes a cold plasma reaction device and a conveying device disposed inside the cold plasma reaction device.

17. The method for preparing the silicon anode material according to claim 16, characterized in that, The cold plasma reaction device is a dielectric barrier discharge plasma reaction device.

18. The method for preparing the silicon anode material according to claim 17, characterized in that, The conveying device includes a transmission belt, a transmission reel, and a power unit.

19. The method for preparing the silicon anode material according to claim 18, characterized in that, The dielectric barrier discharge plasma reaction device includes a reaction chamber, and a first electrode, a second electrode, and a dielectric barrier layer disposed inside the reaction chamber.

20. The method for preparing the silicon anode material according to claim 19, characterized in that, The first electrode and the second electrode are arranged opposite each other, and the material passes between the first electrode and the second electrode through the reaction chamber.

21. The method for preparing the silicon anode material according to claim 19, characterized in that, The transmission belt is located between the first electrode and the second electrode, and the material is placed on the transmission belt.

22. The method for preparing the silicon anode material according to claim 19, characterized in that, The dielectric barrier layer is disposed on the side of the first electrode near the second electrode.

23. The method for preparing the silicon anode material according to claim 15, characterized in that, It also includes a carbon coating unit; the outlet of the cold plasma reaction unit is connected to the inlet of the carbon coating unit.

24. The method for preparing the silicon anode material according to claim 23, characterized in that, The outlet of the silicon deposition unit is located above the inlet of the cold plasma reaction unit, and the outlet of the cold plasma reaction unit is located above the inlet of the carbon coating unit.

25. The method for preparing the silicon anode material according to claim 16, characterized in that, The apparatus for preparing the silicon anode material includes the following steps: Silicon is deposited on a carrier in the silicon deposition unit to obtain composite material particles; The composite material particles are conveyed from the outlet of the silicon deposition unit to the inlet of the cold plasma reaction unit; The composite material particles are subjected to cold plasma treatment in a cold plasma reaction unit.

26. The method for preparing the silicon anode material according to claim 23, characterized in that, It also includes the following steps: The composite material particles treated with cold plasma are conveyed from the outlet of the cold plasma reaction unit to the inlet of the carbon coating unit, and carbon coating is performed on the composite material particles treated with cold plasma in the carbon coating unit.

27. The method for preparing the silicon anode material according to claim 26, characterized in that, The composite material particles are conveyed from the inlet of the cold plasma reaction unit to the outlet of the cold plasma reaction unit using a conveying device.

28. A silicon anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-27.

29. An electrode sheet, characterized in that, Including the silicon anode material as described in claim 28.

30. A secondary battery, characterized in that, Includes the silicon anode material as described in claim 28 or the electrode sheet as described in claim 29.

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