Silicon-based negative electrode material and preparation method and application thereof

Abstract

The application provides a silicon-based negative electrode material and a preparation method and application thereof, and relates to the technical field of lithium ion batteries.A preparation method of a silicon-based negative electrode material comprises the following steps: S1, cleaning and drying a current collector to obtain a clean current collector; S2, performing magnetron sputtering treatment on the clean current collector to obtain a current collector on which a silicon film is deposited; S3, performing metal-assisted etching on the current collector on which the silicon film is deposited to obtain a silicon nanowire negative electrode material; and S4, performing carbon coating and organic surface modification on the silicon nanowire negative electrode material to obtain a silicon-based negative electrode material.The silicon-based negative electrode material prepared by the application has excellent cycle performance.

Description

Technical Field

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

[0002] Silicon-based anodes have attracted considerable attention due to their high theoretical specific capacity (~4212 mAh / g). As a material that can form alloys with lithium, each silicon atom can react with 4.4 lithium ions, representing a significant improvement over the capacity of commercial graphite (~372 mAh / g). This makes them a potential next-generation anode material. Furthermore, silicon's low cost, being one of the most abundant elements on Earth, is another reason for their popularity. However, silicon-based anodes experience significant volume expansion and contraction during charging and discharging. Repeated volume expansion and contraction can lead to material detachment and a rapid capacity decay. Additionally, silicon's low conductivity and lithium-ion conductivity are major reasons why silicon-based anodes are difficult to commercialize on a large scale.

[0003] The most significant problem with silicon-based lithium-ion battery anodes is the unavoidable volume changes that occur during cycling. As cycling progresses, stress buildup occurs, leading to breakage of the active material. To avoid this, nano-sizing is commonly used to address the breakage of active materials caused by volume changes. Silicon nanowires, thanks to their large aspect ratio, have ample space between nanowires to accommodate the spatial changes caused by volume expansion, thus mitigating the problem of active material breakage.

[0004] Magnetron sputtering is a type of physical vapor deposition (PVD) technology, which can be divided into DC magnetron sputtering and radio frequency (RF) magnetron sputtering. RF magnetron sputtering can be applied to materials with poor conductivity. RF magnetron sputtering is generally used for preparing silicon thin films. Currently, common methods for preparing silicon-based nanowire anode materials include chemical vapor deposition (CVD), metal-assisted etching (MAE), and laser ablation. Compared to the other two methods, MAE offers better dimensional controllability, better fabrication safety, and lower environmental requirements. Therefore, the development of a silicon-based anode material is urgently needed and is of great significance to the development of lithium-ion batteries. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a silicon-based anode material, its preparation method and application.

[0006] The present invention proposes a method for preparing a silicon-based anode material, comprising the following steps:

[0007] S1. Clean and dry the current collector to obtain a clean current collector;

[0008] S2. The clean current collector is subjected to magnetron sputtering to obtain a current collector with a silicon thin film deposited on it;

[0009] S3. The current collector with deposited silicon thin film is etched with metal-assisted etching to obtain silicon nanowire anode material;

[0010] S4. Silicon nanowire anode materials are carbon-coated and organically modified to obtain silicon-based anode materials.

[0011] This invention provides a method for preparing a silicon-based anode material. A silicon thin film is prepared on a battery-grade copper foil using a low-cost, simple, and easily industrialized magnetron sputtering method. The silicon thin film is then etched into nanowires using a metal-assisted etching method to prepare a silicon-based anode material with high cycle performance.

[0012] Preferably, in S1, the current collector is a copper foil.

[0013] Preferably, in step S1, the cleaning process includes ultrasonically treating the current collector sequentially in acetone, ethanol, and deionized water for 15–60 minutes.

[0014] Preferably, in step S1, drying includes drying the current collector at 60–80°C for 2–4 hours.

[0015] Preferably, in S2, the magnetron sputtering conditions include: using an inert gas as the working gas, a sputtering power of 50W to 200W, and a gas flow rate of 10 to 100 sccm.

[0016] Controlling the magnetron sputtering process conditions helps to prepare films with high density and good adhesion to the current collector substrate, making them less prone to detachment.

[0017] More preferably, the inert gas is argon.

[0018] Preferably, in S2, the thickness of the film is 0.5 μm to 3 μm.

[0019] Preferably, in step S2, the magnetron sputtering chamber is subjected to high vacuum treatment before the magnetron sputtering process.

[0020] Preferably, in S3, the metal-assisted etching includes: arranging a current collector with a silicon thin film deposited on it using a polystyrene microsphere template, performing metal sputtering on the microspheres, then adding an organic solvent for immersion treatment to remove the thin film material obtained from the microspheres, performing an etching reaction, and acid washing.

[0021] Metal-assisted etching, using polystyrene microspheres as templates, can effectively control the size of nanowires, making it easier to select more suitable nanowire sizes. At the same time, a large number of structural gaps are retained between the nanowire arrays, which helps to improve cycle performance.

[0022] More preferably, the metal used in the metal sputtering is selected from one or more of gold, silver, and iron.

[0023] More preferably, the organic solvent is selected from one or more of acetone, tetrahydrofuran, toluene, dichloromethane, trichloroethylene, tetrahydronaphthalene, decahydronaphthalene, and petroleum ether.

[0024] More preferably, the etching reaction includes immersing the thin film material in an etching solution for etching, wherein the etching solution is a mixture of 5% to 40% hydrofluoric acid and 5% to 30% hydrogen peroxide, wherein the volume ratio of hydrofluoric acid to hydrogen peroxide is 0.3 to 0.9.

[0025] By controlling the composition of the etching solution, the length of the nanowires can be well controlled, thus obtaining silicon-based anode materials with optimal performance.

[0026] More preferably, the acid solution used for pickling is selected from one or more of concentrated nitric acid and aqua regia.

[0027] Preferably, in S4, the carbon coating is selected from one of gas phase carbon coating, liquid phase carbon coating, and solid phase carbon coating; the carbon source for carbon coating is selected from one or more of glucose, pitch, acetylene, and methane.

[0028] Carbon coating allows carbon to be catalyzed in situ by metal to form carbon nanowires that connect within the metal network structure, thereby improving cycle performance.

[0029] Preferably, in step S4, the organic surface modification includes immersing the film material in an organic solvent containing an organic compound to obtain a mixed solution, and then vacuum drying the resulting mixed solution.

[0030] Organic surface modification helps prevent material expansion, which in turn creates a fresh interface that continuously forms an SEI film, leading to electrolyte consumption and thus affecting cycle performance.

[0031] More preferably, the organic compound includes one or more of PR-PAA and PHnH.

[0032] More preferably, the organic compound accounts for 1 wt% to 5 wt% of the mass of the film material.

[0033] More preferably, the organic solvent includes one or more of ethanol and ethylene glycol.

[0034] The present invention also proposes a silicon-based anode material prepared by the above preparation method.

[0035] The silicon-based anode material prepared by this invention has controllable size and excellent cycle performance.

[0036] Application of the above-described silicon-based anode material or the silicon-based anode material prepared by the above-described preparation method in lithium-ion batteries.

[0037] The beneficial effects of this invention are as follows:

[0038] This invention utilizes magnetron sputtering and metal-assisted etching, with the main advantages of rapid and efficient fabrication. The sputtered films exhibit high density and excellent adhesion to the current collector substrate, preventing detachment. Compared to traditional anode materials, magnetron sputtering eliminates the need for conductive agents and binders, while also saving on cumbersome preparation steps such as coating, significantly reducing costs. Furthermore, the etched films possess controllable dimensions and excellent cycle performance. The nanowire array retains numerous structural gaps, which effectively accommodate volume changes induced by silicon nanowires during charging and discharging, thereby reducing internal stress accumulation on the electrode surface, lowering the risk of electrode breakage, and facilitating further industrial production and commercialization of silicon-based anode materials. Attached Figure Description

[0039] Figure 1 The SEM image of the nanowire anode material obtained in Example 1 of this invention is shown.

[0040] Figure 2 This is a cycle performance spectrum of a battery assembled from the negative electrode material prepared in this invention.

[0041] Figure 3 The image shows the cycle performance of batteries assembled from the negative electrode materials of Example 1 and Comparative Example 4.

[0042] Figure 4 The image shows the cycle performance of batteries assembled from the negative electrode materials of Example 1 and Comparative Example 5. Detailed Implementation

[0043] The technical solution of the present invention will be described in detail through specific embodiments.

[0044] Unless otherwise specified, all materials and reagents used in the following examples and comparative examples are commercially available.

[0045] Example 1

[0046] A method for preparing a silicon-based anode material includes the following steps:

[0047] S1. The copper foil is ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 20 minutes in sequence to remove oil and other impurities on the surface of the copper foil. The cleaned copper foil is placed in a forced-air drying oven and dried at 60°C for 2 hours until there is no moisture residue on the surface of the copper foil to obtain clean copper foil.

[0048] S2. Magnetron Sputtering: The SKY / TRP-450 high-vacuum magnetron sputtering system is used as the growth equipment. First, the magnetron sputtering chamber is subjected to high vacuum treatment. Clean copper foil is placed inside the magnetron sputtering instrument, and the prepared target material is placed on the RF target position. The magnetron sputtering chamber is then evacuated to a vacuum level of 1×10⁻⁶. -4 Argon gas with a purity of 99.999% was introduced into the sputtering chamber at a flow rate of 10 sccm, a sputtering power of 200 W, and a sputtering thickness of 2 μm. Magnetron sputtering was then performed to obtain copper foil with a silicon thin film deposited on it.

[0049] S3. Metal-Assisted Etching: Polystyrene microsphere templates are arranged on copper foil with deposited silicon films using the LB method: A 25mm diameter plastic petri dish is cleaned with deionized water; a filter paper of the corresponding diameter is placed in the petri dish and its surface is wetted with deionized water until it adheres tightly to the bottom of the petri dish; a glass slide (20×20mm) is placed at the edge of the petri dish at a certain angle to the bottom and then cleaned with deionized water; the copper foil with deposited silicon films is placed on the filter paper at the bottom of the petri dish and deionized water is injected until the silicon film is completely submerged; a suspension of 200nm diameter polystyrene microspheres is taken into an injection needle and passed through the glass slide... The polystyrene nanosphere template is obtained by gradually dripping the substrate onto the surface of deionized water until the nanospheres are fully covered. After removing the deionized water, the polystyrene nanosphere template is obtained on the surface of the silicon thin film. Gold is then sprayed onto the nanospheres with a thickness of 2-10 nm. The gold-sprayed thin film material is then immersed in tetrahydrofuran for 12 hours to remove the polystyrene nanospheres and obtain a neatly arranged circular template thin film material. The obtained circular template thin film material is then immersed in an etching solution for 1 minute for etching. The etched material is then placed in a concentrated nitric acid solution to remove the residual silver plating layer on the surface after etching, thus obtaining the silicon nanowire anode material. The etching solution is a mixture of 40% hydrofluoric acid and 30% hydrogen peroxide at a volume ratio of 0.3.

[0050] S4. Silicon nanowire anode material is carbon-coated and organically modified to obtain silicon-based anode material; wherein, carbon coating includes a CVD carbon coating process for silicon nanowire anode material: under an argon atmosphere, acetylene is used as a carbon source for chemical vapor deposition, and carbon nanotubes are formed on and inside the metal film surface through in-situ metal catalysis, with the carbon nanotube diameter being 50-100 nm; organic surface modification includes: ultrasonically dispersing the obtained carbon-coated film material in an organic solvent containing 1 mol / L PR-PAA to obtain a mixed solution, and vacuum drying the obtained mixed solution to obtain silicon-based anode material, wherein PR-PAA accounts for 2 wt% of the mass of the film material, and the organic solvent is a mixed solution of ethanol and ethylene glycol in a volume ratio of 1:1.

[0051] Example 2

[0052] The only difference between Example 2 and Example 1 is that the etching time in step S3 is 5 minutes, while the other conditions are the same as in Example 1.

[0053] Example 3

[0054] The only difference between Example 3 and Example 1 is the composition of the etching solution in step S3. The etching solution is a mixture of 40% hydrofluoric acid and 30% hydrogen peroxide in a volume ratio of 0.5. Other conditions are the same as in Example 1.

[0055] Comparative Example 1

[0056] The only difference between Comparative Example 1 and Example 1 is that step S3 was not performed, i.e., metal-assisted etching was not performed. All other conditions were the same as in Example 1.

[0057] Comparative Example 2

[0058] The only difference between Comparative Example 2 and Example 1 is that the organic surface modification in step S4 was not performed; all other conditions were the same as in Example 1.

[0059] Comparative Example 3

[0060] The only difference between Comparative Example 3 and Example 1 is that step S4 was not performed, i.e., the organic surface modification and carbon coating were not performed. All other conditions were the same as in Example 1.

[0061] Comparative Example 4

[0062] The only difference between Comparative Example 4 and Example 1 is the composition of the etching solution in step S3. The etching solution is a mixture of 40% hydrofluoric acid and 30% hydrogen peroxide in a volume ratio of 1.0. Other conditions are the same as in Example 1.

[0063] Comparative Example 5

[0064] The only difference between Comparative Example 5 and Example 1 is that the diameter of the polystyrene microspheres in step S3 is 500 nm, while the other conditions are the same as in Example 1.

[0065] The negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-5 were cut into circular pieces with a diameter of 14 mm and placed in a glove box with water and oxygen concentrations of less than 0.1 ppm. A half-cell with a lithium sheet as the counter electrode was prepared using a CR2032 battery case. The prepared half-cell was placed for more than 10-12 hours to ensure that the electrolyte was fully immersed. The prepared half-cell was then ready for charge and discharge testing.

[0066] Figure 1 The SEM image of the silicon-based anode material obtained in Example 1 of this invention clearly shows the nanowire array structure. Figure 2The graph shows the cycle performance of the battery assembled from the negative electrode material prepared in this invention. It can be seen that the cycle performance of the silicon-based negative electrode material gradually improves with the increase of etching time. This also indicates that carbon coating and organic surface modification have a certain effect on improving cycle performance. Figure 3 The graphs show the cycle performance of batteries assembled from the negative electrode materials of Example 1 and Comparative Example 4. The cycle performance of batteries assembled from negative electrode materials with different etching solution component contents varies. The cycle performance decreased to some extent when the hydrofluoric acid content increased. Figure 4 The graphs show the cycle performance of batteries assembled from the negative electrode materials of Example 1 and Comparative Example 5. The cycle performance of batteries assembled from negative electrode materials with different diameter spherical templates varies. As the diameter of the spherical templates increases, the cycle performance decreases.

[0067] In summary, the silicon-based anode material provided by this invention has excellent cycle performance.

[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based anode material, characterized in that, Includes the following steps: S1. Clean and dry the current collector to obtain a clean current collector; S2. The clean current collector is subjected to magnetron sputtering to obtain a current collector with a silicon thin film deposited on it; S3. The current collector with deposited silicon thin film is etched with metal-assisted etching to obtain silicon nanowire anode material; S4. Silicon nanowire anode materials are carbon-coated and organic surface-modified to obtain silicon-based anode materials. In S3, the metal-assisted etching includes: arranging polystyrene microspheres on a current collector with a deposited silicon thin film as a template, performing metal sputtering on the microspheres, then adding an organic solvent to remove the thin film material obtained from the microspheres, performing an etching reaction, and acid washing; the etching reaction includes immersing the thin film material in an etching solution for etching, the etching solution being a mixture of 5%~40% hydrofluoric acid and 5%~30% hydrogen peroxide, wherein the volume ratio of hydrofluoric acid to hydrogen peroxide is 0.3~0.9; In step S4, the organic surface modification includes immersing the film material in an organic solvent containing an organic compound to obtain a mixed solution, and then vacuum drying the resulting mixed solution; the organic compound is PR-PAA.

2. The preparation method according to claim 1, characterized in that, In S2, the magnetron sputtering conditions include: using an inert gas as the working gas, a sputtering power of 50W~200W, and a gas flow rate of 10~100sccm.

3. The preparation method according to claim 1, characterized in that, In S4, the carbon coating is selected from one of gas phase carbon coating, liquid phase carbon coating, and solid phase carbon coating; the carbon source for carbon coating is selected from one or more of glucose, pitch, acetylene, and methane.

4. A silicon-based anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the silicon-based anode material according to claim 4 or the silicon-based anode material prepared by the preparation method according to any one of claims 1 to 3 in a lithium-ion battery.

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