Self-supporting silicon-based lithium battery negative electrode coating and its preparation method and application

Abstract

The present invention relates to a self-supporting silicon-based negative electrode coating for lithium batteries, and a preparation method and application thereof, belonging to the field of coating technology. The preparation method described in the present invention first dissolves silicon powder, carbon powder and metal powder in water, and obtains a composite powder through emulsification, drying and granulation; the mass ratio of the silicon powder, carbon powder and metal powder is 1‑3:1:6‑8; then atmospheric plasma spraying technology is used to deposit the composite powder on the surface of a soluble salt matrix to obtain the self-supporting silicon-based negative electrode coating for lithium batteries. The self-supporting effect of the metal or carbon frame in the negative electrode coating for lithium batteries described in the present invention can effectively inhibit the volume expansion of silicon-based materials, reduce the weight of lithium batteries, and reduce the loss of electric energy in practical applications. In addition, the self-supporting silicon-based material negative electrode coating for lithium batteries does not require the addition of a binder during the preparation process, and the metal powder can act as a current collector, which can significantly improve the conductivity and electrochemical performance of the lithium battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a self-supporting silicon-based lithium battery negative electrode coating, a preparation method thereof, and an application thereof. Background Art

[0002] With the advancement of science and technology, people have an increasing demand for mobile and fixed energy storage devices. Among them, the most common electrochemical energy storage device is the lithium-ion battery, which mainly relies on the movement of lithium ions between the positive and negative electrodes to work, and has very high efficiency and reversibility. However, with the increasing performance requirements of lithium-ion batteries in commercial applications, people are prompted to seek electrode materials with larger capacity. Among them, silicon has a low lithium insertion potential and high specific capacity (4200mAh / g), and is low-cost and environmentally friendly. It is considered to be one of the most promising negative electrode materials. However, silicon will expand in volume when the lithium-ion battery is charged and discharged, destroying the electrode structure, making the reversible performance of the negative electrode material worse and the battery capacity seriously attenuated. Therefore, it is an inevitable trend to improve silicon-based materials.

[0003] Currently, the conventional lithium battery manufacturing method is to add dispersants, conductive agents, and binders to the negative electrode material to form a negative electrode slurry, which is then coated on the surface of the current collector to obtain the electrode. However, the addition of binders to the negative electrode material can affect the battery's conductivity, increase the battery's internal resistance, and accelerate battery aging.

[0004] Patent CN 109244386 A discloses a high-energy silicon-containing lithium battery and its preparation method. The positive electrode's conductive agents are single-walled carbon nanotubes and graphene; the negative electrode sheet is composed of a negative electrode active material, conductive carbon black, single-walled carbon nanotubes, carbon methyl sulfide (CMC), and a binder. While this method optimizes the composition of the positive and negative electrode conductive agents and the binder to suppress volume expansion and improve charge and discharge stability, the addition of the binder during the lithium battery preparation process can easily reduce the conductivity of the negative electrode, shortening the battery's service life.

[0005] Patent CN 113224304 A discloses a copper-nickel co-doped silicon carbide (SiC) negative electrode material for lithium-ion batteries and its preparation method. Using a gel-sol technique and calcination heat treatment, copper and nickel are in situ doped during the SiC synthesis process to produce a Cu, Ni-SiC electrode material. While this method can alter the unit cell structure and improve mechanical strength and conductivity, it suffers from long processing times and low efficiency, making it unsuitable for commercial applications. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art such as the volume effect of silicon-based materials, low efficiency of existing preparation methods, and poor conductivity of lithium batteries.

[0007] To address the above technical issues, the present invention provides a self-supporting silicon-based negative electrode coating for lithium batteries, as well as its preparation method and application. Utilizing atmospheric plasma spraying and composite powdering technology, the self-supporting silicon-based negative electrode coating for lithium batteries is produced. This effectively suppresses the volume expansion of the silicon-based material, improves the conductivity and electrochemical performance of the lithium battery, and reduces the weight of the lithium battery itself.

[0008] The first object of the present invention is to provide a method for preparing a lithium battery negative electrode coating based on a self-supporting silicon substrate, comprising the following steps:

[0009] S1, dissolving silicon powder, carbon powder and metal powder in a solvent, emulsifying, drying and granulating to obtain a composite powder; the mass ratio of the silicon powder, carbon powder and metal powder is 1-3:1:6-8;

[0010] S2. Using atmospheric plasma spraying technology, the composite powder described in S1 is deposited on the surface of a soluble salt matrix to obtain the self-supporting silicon-based lithium battery negative electrode coating.

[0011] In one embodiment of the present invention, in S1, the silicon powder and metal powder each have a particle size of 100nm-1000nm; the carbon powder has a particle size of 1μm-10μm. The metal powder acts as a current collector, absorbing stress, reducing its own weight, and improving the cycling efficiency and rate capability of the silicon electrode. The carbon powder increases the conductivity of the electrode, while the carbon framework absorbs the stress of the silicon, effectively mitigating the volume changes that occur in the active material during charge and discharge.

[0012] In one embodiment of the present invention, in S1, the carbon powder is graphene oxide powder and / or graphene powder; the metal powder is one or more of copper powder, tin powder and nickel powder.

[0013] In one embodiment of the present invention, the particle size of the graphene powder is 1 μm-10 μm; the particle size of the graphene oxide powder is 1 μm-5 μm.

[0014] In one embodiment of the present invention, in S1, the emulsification is carried out in a high-speed emulsifier with a rotation speed of 7000-9000 rpm and an emulsification time of 9h-11h.

[0015] In one embodiment of the present invention, in S1, the granulation conditions are: inlet temperature of 200-240°C, outlet temperature of 100-120°C, atomization speed of 6000-7000 r / min, and feed rate of 100-150 g / min.

[0016] In one embodiment of the present invention, in S1, the particle size of the composite powder is 45 μm-75 μm.

[0017] In one embodiment of the present invention, in S1, the preparation of the composite powder specifically includes the following steps: dissolving silicon powder, carbon powder and metal powder in water, putting them into a high-speed emulsifier, emulsifying and stirring, and simultaneously drying them with a heater to obtain a colloidal mixture; using a spray granulator to granulate, and after screening with a sieve, obtaining a composite powder.

[0018] In one embodiment of the present invention, in S2, the soluble salt matrix is a potassium bromide glass sheet or a sodium chloride salt brick; the thickness of the soluble salt matrix is 5mm-100mm, which provides conditions for realizing a self-supporting silicon-based lithium battery negative electrode coating.

[0019] In one embodiment of the present invention, a soluble salt matrix is clamped between two plates using a clamp, a circular hole with a diameter of 13 mm is punched on the front plate, and after spraying, a self-supporting silicon-based lithium battery negative electrode coating with a diameter of 13 mm is obtained.

[0020] In one embodiment of the present invention, in S2, the process parameters of atmospheric plasma spraying include: a movement speed of the spray gun of 200-600 mm / s; a spraying distance of 120-200 mm; a power of 26-32 kW; a current of 700-810 A, a voltage of 37-40 V; a flame core temperature of 10000-15000 K; a powder feeding rate of 10-20 g / min; and a number of spraying cycles of 2-10 times.

[0021] In one embodiment of the present invention, in S2, during the atmospheric plasma spraying process, the main gas is argon, the main gas pressure is 0.6-0.8 MPa, and the main gas flow rate is 30-70 L / min; the auxiliary gas is helium, the auxiliary gas pressure is 0.3-0.6 MPa, and the auxiliary gas flow rate is 2-50 L / min.

[0022] In one embodiment of the present invention, in S2, the temperature of the soluble salt matrix during the spraying process does not exceed 600°C.

[0023] The second object of the present invention is to provide a self-supporting silicon-based lithium battery negative electrode coating prepared by the method described.

[0024] In one embodiment of the present invention, the thickness of the self-supporting silicon-based lithium battery negative electrode coating is 40 μm-150 μm, which can be adjusted by the number of spraying cycles.

[0025] The third object of the present invention is to provide a lithium battery electrode, which is prepared from the self-supporting silicon-based lithium battery negative electrode coating.

[0026] The fourth object of the present invention is to provide a lithium battery, the negative electrode of which is prepared using the self-supporting silicon-based lithium battery negative electrode coating.

[0027] The technical solution of the present invention has the following advantages over the prior art:

[0028] (1) The self-supporting effect of the metal or carbon framework in the lithium battery negative electrode coating of the present invention can effectively suppress the volume expansion of the silicon-based material, reduce the weight of the lithium battery, and reduce the loss of electrical energy in practical applications. In addition, the self-supporting silicon-based material lithium battery negative electrode coating does not require the addition of a binder during the preparation process, and the metal powder can act as a current collector, which can significantly improve the conductivity and electrochemical performance of the lithium battery.

[0029] (2) In lithium battery applications, the lithium battery negative electrode coating of the present invention comprises micron-sized / submicron-sized silicon particles deposited on a metal frame or a carbon frame. When the silicon expands, the metal or graphene absorbs the stress of the silicon, significantly reducing the likelihood of silicon fracture and effectively achieving self-support. Furthermore, when the silicon fractures, the silicon particles disperse throughout the composite system, enabling the lithium battery to maintain good electrochemical stability.

[0030] (3) The atmospheric plasma spraying process used in the present invention for the negative electrode coating of lithium batteries achieves a flame core temperature of up to 15,000 K, which allows the metal to be melted. In the plasma spraying environment, silicon and metal are in a molten state, making it easier to coat silicon particles. Furthermore, high temperatures also make it easier to form compounds between silicon and metal, which is beneficial for improving the stability and electrochemical activity of lithium batteries.

[0031] (4) The atmospheric plasma spraying technology used in the lithium battery negative electrode coating of the present invention has strong thermal stress and energy. During the spraying, the silicon will be pre-split and dispersed into very small particles, so that the probability of silicon being destroyed during the electrochemical test will be greatly reduced, and very good properties can be maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 Schematic diagram of a self-supporting silicon-based lithium battery negative electrode coating deposited by the atmospheric plasma spraying technology of the present invention.

[0034] Figure 2 This is a cycle curve diagram of the coating material in the test example.

[0035] Explanation of the accompanying figures: 1-1 is a robotic arm, 1-2 is a powder feeder, 1-3 is a plasma spray gun, 1-4 is a plasma flame, 1-5 is a composite powder, 1-6 is a lithium battery negative electrode coating based on a self-supporting silicon base, and 1-7 is a soluble salt matrix. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0037] Example 1

[0038] A self-supporting silicon-based lithium battery negative electrode coating and a preparation method thereof, specifically comprising the following steps:

[0039] (1) Emulsification: Weigh 30 g of silicon powder, graphene oxide powder, and copper powder in a mass ratio of 1.5:1:7.5, pour them into a 2 L beaker, add 1000 mL of deionized water and mix, put them into a high-speed emulsifier, emulsify and stir, and slowly dry them with a heater at the same time. The speed of the high-speed emulsifier is 8000 rpm, and the emulsification time is 10 h. After the emulsification is completed, a colloidal mixture of silicon powder, graphene oxide powder, and copper powder is obtained; wherein the particle size of the silicon powder is 200 nm, the particle size of the graphene oxide powder is 2 μm, and the particle size of the copper powder is 200 nm.

[0040] (2) Granulation: The emulsified colloidal mixture was granulated on a spray granulator to remove moisture to obtain a silicon / graphene oxide / copper composite powder with a particle size of 50 μm; wherein the parameters of the spray granulator are: inlet temperature of 220°C, outlet temperature of 110°C, atomization speed of 6500 r / min, and feed rate of 135 g / min.

[0041] (3) Spraying technology: Figure 1As shown, a sodium chloride salt brick with a thickness of 25 mm is clamped between two plates using a clamp, a circular hole with a diameter of 13 mm is punched on the front plate, the prepared composite powder 1-5 is placed in a powder feeder 1-2, and a self-supporting lithium battery negative electrode coating 1-6 containing silicon / graphene oxide / copper is prepared on a removable soluble salt matrix 1-7 by atmospheric plasma spraying; wherein, the parameters of the atmospheric plasma spraying are set as follows: the power of the spray gun 1-3 is 30 kW, the current is 750 A, the voltage is 40 V, the flame core 1-4 temperature is 12000 K, the main gas is argon, the main gas pressure is 0.7 MPa, the main gas flow rate is 35 L / min, the auxiliary gas is helium, the auxiliary gas pressure is 0.4 MPa, the auxiliary gas flow rate is 5 L / min, the powder feeding rate is 10 g / min, the moving speed of the robotic arm 1-1 is set to 200 mm / s, the spraying distance is 120 mm, and the number of spraying cycles is 3 times. The temperature of the substrate during the spraying process was 500° C. The composite coating thickness was set to 45 μm and the diameter was set to 13 mm.

[0042] Example 2

[0043] A self-supporting silicon-based lithium battery negative electrode coating and a preparation method thereof, specifically comprising the following steps:

[0044] (1) Emulsification: Weigh 30 g of silicon powder, graphene oxide powder, and copper powder in a mass ratio of 3:1:6, pour them into a 2 L beaker, add 1000 mL of deionized water and mix, put them into a high-speed emulsifier, emulsify and stir, and slowly dry them with a heater at the same time. The speed of the high-speed emulsifier is 8000 rpm, and the emulsification time is 10 h. After the emulsification is completed, a colloidal mixture of silicon powder, graphene oxide powder, and copper powder is obtained; wherein the particle size of the silicon powder is 400 nm, the particle size of the graphene oxide powder is 5 μm, and the particle size of the copper powder is 400 nm.

[0045] (2) Granulation: The emulsified colloidal mixture was granulated on a spray granulator to remove moisture to obtain a silicon / graphene oxide / copper composite powder with a particle size of 65 μm; wherein the parameters of the spray granulator are: inlet temperature of 220°C, outlet temperature of 110°C, atomization speed of 6500 r / min, and feed rate of 135 g / min.

[0046] (3) Spraying technology: A 25 mm thick sodium chloride salt brick was clamped between two plates using a fixture. A 13 mm diameter circular hole was punched in the front plate. The prepared composite powder was placed in a powder feeder. A self-supporting lithium battery negative electrode coating containing silicon / graphene oxide / copper was prepared on a removable dissolved salt substrate by atmospheric plasma spraying. The atmospheric plasma spraying parameters were set as follows: spray gun power of 30 kW, current of 750 A, voltage of 40 V, flame core temperature of 12000 K, main gas of argon, main gas pressure of 0.7 MPa, main gas flow rate of 35 L / min, auxiliary gas of helium, auxiliary gas pressure of 0.4 MPa, auxiliary gas flow rate of 5 L / min, powder feeding rate of 10 g / min, robot arm movement speed of 200 mm / s, spraying distance of 120 mm, and spraying cycle number of 3 times. The substrate temperature during the spraying process was 500 °C. The composite coating thickness is set to 45 μm and the diameter size is set to 13 mm.

[0047] Example 3

[0048] A self-supporting silicon-based lithium battery negative electrode coating and a preparation method thereof, specifically comprising the following steps:

[0049] (1) Emulsification: Weigh 30 g of silicon powder, graphene oxide powder, and tin powder in a mass ratio of 1.5:1:7.5, pour them into a 2 L beaker, add 1000 mL of deionized water and mix, put them into a high-speed emulsifier, emulsify and stir, and slowly dry them with a heater at the same time. The speed of the high-speed emulsifier is 8000 rpm, and the emulsification time is 10 h. After the emulsification is completed, a colloidal mixture of silicon powder, graphene oxide powder, and tin powder is obtained; wherein the particle size of the silicon powder is 200 nm, the particle size of the graphene oxide powder is 2 μm, and the particle size of the tin powder is 200 nm.

[0050] (2) Granulation: The emulsified colloidal mixture was granulated on a spray granulator to remove moisture to obtain a silicon / graphene oxide / tin composite powder with a particle size of 50 μm; wherein the parameters of the spray granulator are: inlet temperature of 220°C, outlet temperature of 110°C, atomization speed of 6500 r / min, and feed rate of 135 g / min.

[0051] (3) Spraying technology: A 25 mm thick sodium chloride salt brick was clamped between two plates using a fixture. A 13 mm diameter circular hole was punched in the front plate. The prepared composite powder was placed in a powder feeder. A self-supporting lithium battery negative electrode coating containing silicon / graphene oxide / tin was prepared on a removable dissolved salt substrate by atmospheric plasma spraying. The atmospheric plasma spraying parameters were set as follows: spray gun power of 30 kW, current of 750 A, voltage of 40 V, flame core temperature of 12000 K, main gas of argon, main gas pressure of 0.7 MPa, main gas flow rate of 35 L / min, auxiliary gas of helium, auxiliary gas pressure of 0.4 MPa, auxiliary gas flow rate of 5 L / min, powder feeding rate of 10 g / min, robot arm movement speed of 200 mm / s, spraying distance of 120 mm, and spraying cycle number of 3 times. The substrate temperature during the spraying process was 500 °C. The composite coating thickness is set to 45 μm and the diameter size is set to 13 mm.

[0052] Example 4

[0053] A self-supporting silicon-based lithium battery negative electrode coating and a preparation method thereof, specifically comprising the following steps:

[0054] (1) Emulsification: Weigh 30 g of silicon powder, graphene oxide powder, and tin powder in a mass ratio of 3:1:6, pour them into a 2 L beaker, add 1000 mL of deionized water and mix, put them into a high-speed emulsifier, emulsify and stir, and slowly dry them with a heater at the same time. The speed of the high-speed emulsifier is 8000 rpm, and the emulsification time is 10 h. After the emulsification is completed, a colloidal mixture of silicon powder, graphene oxide powder, and tin powder is obtained; wherein the particle size of the silicon powder is 400 nm, the particle size of the graphene oxide powder is 5 μm, and the particle size of the tin powder is 400 nm.

[0055] (2) Granulation: The emulsified colloidal mixture was granulated on a spray granulator to remove moisture to obtain a silicon / graphene oxide / tin composite powder with a particle size of 65 μm; wherein the parameters of the spray granulator are: inlet temperature of 220°C, outlet temperature of 110°C, atomization speed of 6500 r / min, and feed rate of 135 g / min.

[0056] (3) Spraying technology: A 25 mm thick sodium chloride salt brick was clamped between two plates using a fixture. A 13 mm diameter circular hole was punched in the front plate. The prepared composite powder was placed in a powder feeder. A self-supporting lithium battery negative electrode coating containing silicon / graphene oxide / tin was prepared on a removable dissolved salt substrate by atmospheric plasma spraying. The atmospheric plasma spraying parameters were set as follows: spray gun power of 30 kW, current of 750 A, voltage of 40 V, flame core temperature of 12000 K, main gas of argon, main gas pressure of 0.7 MPa, main gas flow rate of 35 L / min, auxiliary gas of helium, auxiliary gas pressure of 0.4 MPa, auxiliary gas flow rate of 5 L / min, powder feeding rate of 10 g / min, robot arm movement speed of 200 mm / s, spraying distance of 120 mm, and spraying cycle number of 3 times. The substrate temperature during the spraying process was 500 °C. The composite coating thickness is set to 45 μm and the diameter size is set to 13 mm.

[0057] Comparative Example 1

[0058] The method is basically the same as Example 2, except that the spray gun power is 22kW, the current is 600A, and the voltage is 37V.

[0059] Comparative Example 2

[0060] The same as Example 4, except that the spray gun power is 35kW, the current is 800A, and the voltage is 44V.

[0061] Comparative analysis:

[0062] The surface morphology of the self-supporting silicon-based lithium battery negative electrode coating prepared in Examples 1-4 and Comparative Examples 1-2 was measured and investigated. The coatings in Examples 1-4 were dense and uniform, and the metal and graphene oxide formed a self-supporting framework, which reduced the stress effect of silicon, effectively suppressed the volume expansion of the negative electrode material, and reduced the weight of the lithium battery itself. However, the self-supporting coating obtained in Comparative Example 1-2 had phenomena such as falling off and breaking. It can be seen that when the spraying process parameters are insufficient or too large, that is, when the heating and melting state is not good, the bonding strength of the coating is not good, the mutual wrapping between the various particles is not good, and the entire coating is not sufficient to support the long-life cycle operation of the lithium battery.

[0063] Test Case

[0064] The coating materials prepared in Examples 1-4 and Comparative Examples 1-2 were fabricated into button cells to test their performance. The working electrode was a self-supporting silicon-based lithium battery negative electrode coating, the auxiliary and reference electrodes were lithium sheets, the separator was an 18 mm diameter polypropylene film, and the electrolyte was a 1.0 mol / L lithium hexafluorophosphate / ethylene carbonate:diethyl carbonate (1:1 volume ratio). In an argon-filled glove box with a moisture content of less than 24.2 ppm, the working electrode, separator, lithium sheet, gasket, and spring were sequentially placed into the battery case to assemble a CR2032 button cell.

[0065] Battery performance tests were conducted on a NEWARE-BTS-5V / 10mA battery test system with a voltage range of 0.01-3V and a current density of 100mA / g for cycle life. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were measured using an electrochemical workstation (CHI604E and IM6ex) with a fluctuation amplitude of 5mV and a frequency range of 10 -2 -10 5 Hz. The test results are shown in Table 1 and Figure 2 As shown:

[0066] Table 1

[0067] Sample First cycle discharge capacity (mAh / g) First cycle charge capacity (mAh / g) First-cycle coulombic efficiency (%) Example 1 1158 698 60.3 Example 2 1385 892 64.4 Example 3 1217 722 59.3 Example 4 1246 783 62.8 Comparative Example 1 754 348 46.2 Comparative Example 2 718 301 41.9

[0068] From Table 1 and Figure 2 It can be seen from the data that the present invention can prepare a lithium battery negative electrode coating material with excellent performance, and Examples 1-4 all show good electrochemical performance. Among them, the batteries prepared in Examples 2 and 4 have a higher first-cycle coulomb efficiency, indicating that the self-supporting silicon-based material lithium battery negative electrode coating with a large silicon content has better cycle performance and reversible capacity. In contrast, the battery first-cycle charge / discharge specific capacity and first-cycle coulomb efficiency obtained in Comparative Examples 1 and 2 are lower than those in Examples 1-4, indicating that the spraying process will affect the electrochemical properties of the coating, and too high or too low power will reduce the coating performance, making it difficult to achieve a self-supporting effect. Therefore, the self-supporting silicon-based material lithium battery negative electrode coating of the present invention can significantly improve the coulomb efficiency of the lithium battery and has significant economic benefits.

[0069] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium battery negative electrode coating based on a self-supporting silicon substrate, characterized in that: The following steps are included: S1. Dissolving silicon powder, carbon powder, and metal powder in water, emulsifying, drying, and granulating to obtain a composite powder; the mass ratio of the silicon powder, carbon powder, and metal powder is 1-3:1:6-8; the carbon powder is graphene oxide powder and / or graphene powder; and the metal powder is one or more of copper powder, tin powder, and nickel powder; S2. Use atmospheric plasma spraying technology to deposit the composite powder described in S1 on the surface of a soluble salt matrix to obtain the self-supporting silicon-based lithium battery negative electrode coating; the process parameters of atmospheric plasma spraying include: the movement speed of the spray gun is 200-600 mm / s; the spraying distance is 120-200 mm; the power is 26-32 kW; the current is 700-810 A, the voltage is 37-40 V; the flame core temperature is 10000-15000 K; the powder feeding rate is 10-20 g / min; and the number of spraying cycles is 2-10 times.

2. The method for preparing a self-supporting silicon-based negative electrode coating for a lithium battery according to claim 1, characterized in that: In S1, the particle sizes of the silicon powder and the metal powder are both 100 nm-1000 nm; the particle size of the carbon powder is 1 μm-10 μm.

3. The method for preparing a lithium battery negative electrode coating based on a self-supporting silicon substrate according to claim 1, characterized in that: In S1, the granulation conditions are: inlet temperature of 200-240°C, outlet temperature of 100-120°C, atomizing speed of 6000-7000 r / min, and feed rate of 100-150 g / min.

4. The method for preparing a lithium battery negative electrode coating based on a self-supporting silicon substrate according to claim 1, characterized in that: In S2, the soluble salt matrix is a potassium bromide glass sheet or a sodium chloride salt brick; the thickness of the soluble salt matrix is 5 mm to 100 mm.

5. The method for preparing a lithium battery negative electrode coating based on a self-supporting silicon substrate according to claim 1, characterized in that: In S2, during the atmospheric plasma spraying process, the main gas is argon, the main gas pressure is 0.6-0.8 MPa, and the main gas flow rate is 30-70 L / min; the auxiliary gas is helium, the auxiliary gas pressure is 0.3-0.6 MPa, and the auxiliary gas flow rate is 2-50 L / min.

6. A self-supporting silicon-based negative electrode coating for lithium batteries prepared by the method according to any one of claims 1 to 5.

7. A lithium battery electrode, characterized in that: The lithium battery electrode is prepared from the self-supporting silicon-based lithium battery negative electrode coating according to claim 6.

8. A lithium battery, characterized in that: The negative electrode is prepared by using the self-supporting silicon-based lithium battery negative electrode coating according to claim 6.

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