Preparation method of copper-doped porous nanosilicon negative electrode material
By embedding copper ions into montmorillonite and using molten salt-assisted magnesothermic reaction to prepare copper-doped nanoporous silicon materials, the structural collapse problem of nano-silicon anode materials during charge and discharge processes was solved, thereby improving the cycle stability and electrochemical performance of lithium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2024-07-19
- Publication Date
- 2026-07-21
AI Technical Summary
Existing nano-silicon anode materials suffer from severe structural collapse during repeated charge-discharge cycles, resulting in poor cycle performance. Furthermore, nano-silicon materials prepared by existing magnesia reduction methods exhibit insufficient stability during volume expansion.
Using inexpensive montmorillonite as raw material, copper ions are embedded through ion exchange technology and combined with molten salt-assisted magnesothermic reaction to prepare copper-doped nanoporous silicon materials. The copper-silicon alloy phase is used to slow down volume expansion and enhance structural stability.
It effectively suppresses nanostructure collapse, improves lithium storage performance, rate performance and cycle performance of lithium batteries, enhances electrical conductivity and promotes electron migration.
Smart Images
Figure CN118908220B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a method for preparing copper-doped porous nano-silicon anode material. Background Technology
[0002] Lithium-ion batteries possess characteristics such as high energy density, long lifespan, high safety, low self-discharge rate, and no memory effect, making them one of the most widely used energy storage devices today. Silicon materials have a large lithium storage capacity, thus silicon anodes can significantly improve the energy density of lithium-ion batteries. However, the pulverization effect caused by the large volume expansion rate during charging poses challenges for practical applications. Nanostructuring is an effective means to overcome the pulverization of silicon anodes, and its shorter lithium-ion diffusion distance is beneficial for improving the lithium storage capacity of silicon anodes at high current densities. However, the structural collapse effect that occurs in nano-silicon materials after multiple charge-discharge cycles adversely affects their long-term cycle stability.
[0003] Montmorillonite is a hydrous aluminosilicate two-dimensional layered mineral with abundant resources, low price, large specific surface area, and exchangeable interlayer cations. Currently, magnesothermic reduction using montmorillonite as a raw material has become a cheap and efficient method for preparing nano-silicon materials. For example, patent CN110034296A discloses a method for preparing convex mirror-shaped silicon nanosheets by intercalation separation of montmorillonite combined with magnesiac reduction technology. This method breaks the interlayer bonding force of montmorillonite, separating the silicon and aluminum layers, increasing the contact area between silicon oxide and magnesium powder, and ensuring that very thin silicon nanosheets are obtained after magnesiac reduction. This results in superior electrochemical performance in the field of lithium-ion battery anode materials. Patent CN117303370A discloses a method for preparing silicon nanosheet anode materials by molten salt-assisted magnesiac reduction of montmorillonite. This method enables montmorillonite to form a nanosheet structure, which helps silicon particles maintain their integrity during charge and discharge, slows down volume expansion, and improves the cycle life and rate performance of lithium-ion batteries. Furthermore, this preparation method is adaptable to different production scales and has high scalability. Even though montmorillonite-magnesiac-reduced silicon has nanoporous properties that can effectively alleviate the volume expansion effect during silicon charge and discharge, the nano-silicon materials prepared by the above methods still suffer from poor cycle performance due to the collapse of the porous structure after multiple charge and discharge cycles. Summary of the Invention
[0004] To address the shortcomings of the existing technologies, this invention proposes a method for preparing copper-doped porous nanoporous silicon anode materials. Utilizing inexpensive montmorillonite as the silicon source, and combining ion exchange technology with molten salt-assisted magnesiothermal reaction, copper-doped porous nanoporous silicon materials with excellent cycle performance and good structural stability are obtained in a one-step reaction.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing copper-doped porous nano-silicon anode material, comprising the following steps:
[0006] (1) Mix copper salt solution with montmorillonite and let stand, then filter, collect and vacuum dry to obtain copper ion doped montmorillonite;
[0007] (2) Copper ion-doped montmorillonite, magnesium powder and metal chloride are mixed evenly under anhydrous and oxygen-free conditions to obtain molten salt-assisted magnesium thermal reduction raw material.
[0008] (3) The molten salt-assisted magnesium thermal reduction raw material was subjected to magnesium thermal reduction reaction in an anhydrous and oxygen-free atmosphere to obtain a mixture containing copper-doped nano-silicon materials.
[0009] (4) The mixture of copper-doped nano-silicon materials was washed and filtered sequentially with water and acid solution, and the filtered product was vacuum dried to obtain copper-doped porous nano-silicon material preform.
[0010] (5) The copper-doped porous nano-silicon material preform is heat-treated in a protective gas to obtain the copper-doped porous nano-silicon anode material.
[0011] In a preferred embodiment of the present invention, the copper salt is at least one of copper chloride, copper sulfate, and copper nitrate; the metal chloride is at least one of sodium chloride, potassium chloride, magnesium chloride, and calcium chloride.
[0012] In a preferred embodiment of the present invention, the mass-to-volume ratio of montmorillonite to copper salt solution is (0.1-1):(1-10); the concentration of copper salt solution is 0.1-10 mol / L.
[0013] In a preferred embodiment of the present invention, the mass ratio of copper ion-doped montmorillonite, magnesium powder and metal chloride is 1:(0.1-5):(1-10).
[0014] In a preferred embodiment of the present invention, the temperature of the magnesium thermal reduction reaction is 400-1000°C and the time is 1-36 hours.
[0015] As a preferred embodiment of the present invention, in step (4), the acid solution cleaning includes cleaning with A acid first, followed by cleaning with B acid; A acid is at least one of hydrochloric acid, sulfuric acid, and nitric acid, and B acid is at least one of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid.
[0016] In a preferred embodiment of the present invention, the concentration of the A acid is 0.01–5 mol / L, and the cleaning time is 1 min–10 h; the mass percentage concentration of the B acid is 0.01%–10%, and the cleaning time is 1 min–10 h.
[0017] In a preferred embodiment of the present invention, the temperature of the vacuum drying process is 40-80°C and the time is 1 min-24 h.
[0018] In a preferred embodiment of the present invention, the heat treatment temperature is 300-1000°C and the time is 1 min-24 h.
[0019] In a preferred embodiment of the present invention, the anhydrous and oxygen-free gas atmosphere is one or more of nitrogen, argon, hydrogen and helium.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0021] This invention uses inexpensive montmorillonite as raw material. Utilizing the ion exchange property between montmorillonite layers, copper ions are embedded into the internal structure of montmorillonite through ion exchange. A copper-silicon alloy phase is then obtained through a molten salt-assisted magnesothermic reduction reaction. Lithium ions can enter the montmorillonite interlayer and react with the copper-silicon alloy phase, thereby mitigating volume expansion from the inside. This process requires relatively few controlled influencing factors. This invention not only effectively suppresses the nanostructure collapse effect after multiple charge-discharge cycles but also enhances the crystal structure stability of montmorillonite to a certain extent. The metallic copper precipitated after the copper-silicon alloy reacts with lithium ions can also improve the conductivity of montmorillonite, promote electron migration, and improve electrochemical performance. Therefore, this invention can significantly improve the lithium storage performance, rate performance, and cycle performance of lithium batteries. Attached Figure Description
[0022] Figure 1 This is a SEM image of the copper-doped porous nano-silicon anode material prepared in Example 1.
[0023] Figure 2 The image shows the elemental energy spectrum of the copper-doped porous nano-silicon anode material prepared in Example 1.
[0024] Figure 3 The image shows the XRD pattern of the copper-doped porous nano-silicon anode material prepared in Example 1.
[0025] Figure 4 The graph shows the lithium storage cycle performance of the copper-doped porous nano-silicon anode material prepared in Example 1.
[0026] Figure 5 The images show the SEM images of the undoped copper porous nano-silicon anode material electrode film prepared in Comparative Example 1 before and after 2000 cycles; (a) is the SEM image of the undoped copper porous nano-silicon anode material electrode film prepared in Comparative Example 1 before 2000 cycles; (b) is the SEM image of the undoped copper porous nano-silicon anode material electrode film prepared in Comparative Example 1 after 2000 cycles.
[0027] Figure 6 The images show SEM comparisons of the morphology of the copper-doped porous nano-silicon anode material electrode film prepared in Example 1 before and after 2000 cycles; (a) SEM comparison of the morphology of the copper-doped porous nano-silicon anode material electrode film prepared in Example 1 before 2000 cycles; (b) SEM comparison of the morphology of the copper-doped porous nano-silicon anode material electrode film prepared in Example 1 after 2000 cycles.
[0028] Figure 7 This is a SEM image of the copper-doped porous nano-silicon anode material prepared in Example 2.
[0029] Figure 8 The graph shows the lithium storage cycle performance of the copper-doped porous nano-silicon anode material prepared in Example 2. Detailed Implementation
[0030] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.
[0031] Example 1
[0032] A method for preparing a copper-doped porous nano-silicon anode material includes the following steps:
[0033] (1) Prepare a copper chloride solution. After thoroughly stirring the copper chloride solution with montmorillonite, let it stand for a certain period of time to allow the interlayer metal ions of montmorillonite to undergo ion exchange with the copper ions in the copper chloride solution. After the ion exchange is completed, filter and collect the solution and vacuum dry it to obtain copper ion-doped montmorillonite.
[0034] (2) Copper ion-doped montmorillonite, magnesium powder and anhydrous sodium chloride are mixed in a glove box at a weight ratio of 10:8:40 and ground in a mortar to obtain molten salt-assisted magnesium thermal reduction raw material.
[0035] (3) Place the molten salt-assisted magnesium thermal reduction raw material in a stainless steel crucible, transfer it to a tube furnace with argon gas, and heat it to 650°C to carry out the molten salt-assisted magnesium thermal reduction reaction of montmorillonite and magnesium powder. The reaction time is 6 hours to obtain a mixture containing copper-doped nano-silicon materials.
[0036] (4) The mixture of copper-doped nano-silicon materials was ground, deionized water was added to the ground powder and stirred slowly for 2 hours, and then filtered to obtain solid powder product I; solid powder product I was added to 0.5 mol / L hydrochloric acid and stirred at room temperature for 4 hours, and then filtered to obtain solid powder product II; solid powder product II was dispersed in 0.5% HF solution and stirred for 4 hours to leach, filtered and rinsed with deionized water several times to obtain solid powder III; solid powder III was placed in a vacuum drying oven and vacuum dried at 60°C for 10 hours to obtain copper-doped porous nano-silicon material preform.
[0037] (5) The copper-doped porous nano-silicon material preform was annealed under an argon atmosphere at a temperature of 400°C for 2 hours to obtain the copper-doped porous nano-silicon anode material.
[0038] The application of a copper-doped porous nano-silicon anode material as a battery material is as follows:
[0039] according to Figure 1 It can be seen that the copper-doped porous nano-silicon anode material prepared in this embodiment has a porous structure. According to... Figure 2 It can be seen that the copper-doped porous nano-silicon anode material contains only copper, silicon, and oxygen elements. This is shown in the XRD pattern. Figure 3 It is known that copper-doped porous nano-silicon anode materials possess a single-element silicon crystalline phase. Using the porous nano-silicon anode material prepared in this embodiment as the positive electrode, lithium metal sheets as the negative electrode, and a Celgard membrane as the separator, the electrolyte consists of LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio 3:7) with 10 wt% fluoroethylene carbonate (FEC). The binder consists of polyacrylic acid (PAA) and sodium carboxymethyl cellulose (CMC, 6 wt%) (PAA / CMC volume ratio 1:1). The working electrode is prepared with silicon nanosheets, conductive carbon black Super-P, and binder in a weight ratio of 7:1.5:1.5. The battery is assembled in an argon-filled glove box, and constant current charge-discharge tests are performed. Figure 4 It is known that the copper-doped porous nano-silicon anode material has a reversible capacity of 1400 mAh / g after 2000 cycles at a current density of 200 mA / g.
[0040] according to Figure 6 It can be seen that the electrode surface of the copper-doped porous nano-silicon anode material prepared in this embodiment only forms some tiny cracks before and after cycling, indicating that the cross-sectional expansion of the silicon electrode is significantly improved under the synergistic effect of nanopority and copper doping, and the electrochemical performance is also improved.
[0041] Example 2
[0042] A method for preparing a copper-doped porous nano-silicon anode material includes the following steps:
[0043] (1) Prepare a copper sulfate solution. After thoroughly stirring the copper sulfate solution with montmorillonite, let it stand for a certain period of time to allow the metal ions between the montmorillonite layers to undergo ion exchange with the copper ions in the copper sulfate solution. After the ion exchange is completed, filter and collect the solution and vacuum dry it to obtain copper ion-doped montmorillonite.
[0044] (2) Copper ion-doped montmorillonite, magnesium powder, anhydrous lithium chloride and anhydrous magnesium chloride are mixed in a glove box at a weight ratio of 10:8:30:10 and ground in a mortar to obtain molten salt-assisted magnesium thermal reduction raw material.
[0045] (3) Place the molten salt-assisted magnesium thermal reduction raw material in a stainless steel crucible, transfer it to a tube furnace with argon gas, and heat it to 800°C to carry out the molten salt-assisted magnesium thermal reduction reaction of montmorillonite and magnesium powder. The reaction time is 3h to obtain a mixture containing copper-doped nano-silicon materials.
[0046] (4) The mixture of copper-doped nano-silicon materials was ground, deionized water was added to the ground powder and stirred slowly for 2 hours, and then filtered to obtain solid powder product I; solid powder product I was added to 0.5 mol / L hydrochloric acid and stirred at room temperature for 4 hours, and then filtered to obtain solid powder product II; solid powder product II was dispersed in 0.5% HF solution and stirred for 4 hours to leach, filtered and rinsed with deionized water several times to obtain solid powder III; solid powder III was placed in a vacuum drying oven and vacuum dried at 60°C for 10 hours to obtain copper-doped porous nano-silicon material preform.
[0047] (5) The copper-doped porous nano-silicon material preform was annealed under an argon atmosphere at a temperature of 400°C for 2 hours to obtain the copper-doped porous nano-silicon anode material.
[0048] The application of a copper-doped porous nano-silicon anode material as a battery material is as follows:
[0049] according to Figure 7It is known that the copper-doped porous nano-silicon anode material prepared in this embodiment has a porous structure, and the copper-doped porous nano-silicon anode material contains only copper, silicon, and oxygen elements, and has a single-element silicon crystal phase. Using the porous nano-silicon anode material prepared in this embodiment as the positive electrode, lithium metal sheets as the negative electrode, and a Celgard membrane as the separator, the electrolyte is composed of LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio 3:7) with 10 wt% fluoroethylene carbonate (FEC). The binder is composed of polyacrylic acid (PAA) and sodium carboxymethyl cellulose (CMC, 6 wt%) (PAA / CMC volume ratio 1:1). The working electrode is prepared with silicon nanosheets, conductive carbon black Super-P, and binder in a weight ratio of 7:1.5:1.5. The battery is assembled in an argon-filled glove box, and constant current charge-discharge tests are performed. Figure 8 It can be seen that the copper-doped porous nano-silicon anode material has a reversible capacity of 1370 mAh / g after 2000 cycles at a current density of 200 mA / g.
[0050] Example 3
[0051] A method for preparing a copper-doped porous nano-silicon anode material includes the following steps:
[0052] (1) Prepare a copper sulfate solution. After thoroughly stirring the copper sulfate solution with montmorillonite, let it stand for a certain period of time to allow the metal ions between the montmorillonite layers to undergo ion exchange with the copper ions in the copper sulfate solution. After the ion exchange is completed, filter and collect the solution and vacuum dry it to obtain copper ion-doped montmorillonite.
[0053] (2) Copper ion-doped montmorillonite, magnesium powder and anhydrous magnesium chloride are mixed in a glove box at a weight ratio of 10:1:100 and ground in a mortar to obtain molten salt-assisted magnesium thermal reduction raw material.
[0054] (3) Place the molten salt-assisted magnesium thermal reduction raw material in a stainless steel crucible, transfer it to a tube furnace with argon gas, and heat it to 1000℃ to carry out the molten salt-assisted magnesium thermal reduction reaction of montmorillonite and magnesium powder. The reaction time is 1h to obtain a mixture containing copper-doped nano-silicon materials.
[0055] (4) The mixture of copper-doped nano-silicon materials was ground, deionized water was added to the ground powder and stirred slowly for 10 h, and the solid powder product I was obtained by filtration. The solid powder product I was added to 0.01 mol / L hydrochloric acid and stirred at room temperature for 10 h, and the solid powder product II was obtained by filtration. The solid powder product II was dispersed in 0.01% HF solution and stirred for 10 h to leach, filtered and rinsed with deionized water several times to obtain solid powder III. The solid powder III was placed in a vacuum drying oven and vacuum dried at 40°C for 24 h to obtain copper-doped porous nano-silicon material preform.
[0056] (5) The copper-doped porous nano-silicon material preform was annealed under an argon atmosphere at a temperature of 1000℃ for 1 min to obtain the copper-doped porous nano-silicon anode material.
[0057] The application of a copper-doped porous nano-silicon anode material as a battery material is as follows:
[0058] The copper-doped porous nano-silicon anode material prepared in this embodiment has a porous structure and contains only copper, silicon and oxygen elements, and has a single silicon crystal phase. Using the porous nano-silicon anode material prepared in this embodiment as the positive electrode, lithium metal sheet as the negative electrode, and Celgard membrane as the separator, the electrolyte is composed of LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio of 3:7) with 10 wt% fluoroethylene carbonate (FEC). The binder is composed of polyacrylic acid (PAA) and sodium carboxymethyl cellulose (CMC, 6 wt%) (PAA / CMC volume ratio of 1:1). The working electrode is prepared by silicon nanosheets, conductive carbon black Super-P, and binder in a weight ratio of 7:1.5:1.5. The battery is assembled in an argon-filled glove box and constant current charge-discharge test is performed. The copper-doped porous nano-silicon anode material has a reversible capacity of 1500 mAh / g after 2000 cycles at a current density of 200 mA / g.
[0059] Example 4
[0060] A method for preparing a copper-doped porous nano-silicon anode material includes the following steps:
[0061] (1) Prepare a copper sulfate solution. After thoroughly stirring the copper sulfate solution with montmorillonite, let it stand for a certain period of time to allow the metal ions between the montmorillonite layers to undergo ion exchange with the copper ions in the copper sulfate solution. After the ion exchange is completed, filter and collect the solution and vacuum dry it to obtain copper ion-doped montmorillonite.
[0062] (2) Copper ion-doped montmorillonite, magnesium powder and anhydrous magnesium chloride are mixed in a glove box at a weight ratio of 10:50:10 and ground in a mortar to obtain molten salt-assisted magnesium thermal reduction raw material.
[0063] (3) Place the molten salt-assisted magnesium thermal reduction raw material in a stainless steel crucible, transfer it to a tube furnace with argon gas, and heat it to 400°C to carry out the molten salt-assisted magnesium thermal reduction reaction of montmorillonite and magnesium powder. The reaction time is 36h to obtain a mixture containing copper-doped nano-silicon materials.
[0064] (4) The mixture of copper-doped nano-silicon materials is ground, deionized water is added to the ground powder and stirred slowly for 1 min, and then filtered to obtain solid powder product I; the solid powder product I is added to 5 mol / L hydrochloric acid and stirred at room temperature for 1 min, and then filtered to obtain solid powder product II; the solid powder product II is dispersed in 5% HF solution and stirred for 1 min to leach, filtered and rinsed with deionized water several times to obtain solid powder III; the solid powder III is placed in a vacuum drying oven and vacuum dried at 80°C for 1 min to obtain copper-doped porous nano-silicon material preform.
[0065] (5) The copper-doped porous nano-silicon material preform was annealed under an argon atmosphere at a temperature of 300°C for 24 hours to obtain the copper-doped porous nano-silicon anode material.
[0066] The application of a copper-doped porous nano-silicon anode material as a battery material is as follows:
[0067] The copper-doped porous nano-silicon anode material prepared in this embodiment has a porous structure and contains only copper, silicon and oxygen elements, and has a single silicon crystal phase. Using the porous nano-silicon anode material prepared in this embodiment as the positive electrode, lithium metal sheet as the negative electrode, and Celgard membrane as the separator, the electrolyte is composed of LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio of 3:7) with 10 wt% fluoroethylene carbonate (FEC). The binder is composed of polyacrylic acid (PAA) and sodium carboxymethyl cellulose (CMC, 6 wt%) (PAA / CMC volume ratio of 1:1). The working electrode is prepared by silicon nanosheets, conductive carbon black Super-P, and binder in a weight ratio of 7:1.5:1.5. The battery is assembled in an argon-filled glove box and constant current charge-discharge test is performed. The copper-doped porous nano-silicon anode material has a reversible capacity of 1450 mAh / g after 2000 cycles at a current density of 200 mA / g.
[0068] Comparative Example 1
[0069] A method for preparing a porous nano-silicon anode material includes the following steps:
[0070] (1) Montmorillonite, magnesium powder and anhydrous sodium chloride are mixed in a glove box at a weight ratio of 10:8:40 and ground in a mortar to obtain molten salt-assisted magnesium thermal reduction raw material.
[0071] (3) Place the molten salt-assisted magnesium thermal reduction raw material in a stainless steel crucible, transfer it to a tube furnace with argon gas, and heat it to 650°C to carry out the molten salt-assisted magnesium thermal reduction reaction of montmorillonite and magnesium powder. The reaction time is 6 hours to obtain a mixture containing nano-silicon materials.
[0072] (4) The mixture of nano-silicon materials is ground, deionized water is added to the ground powder and stirred slowly for 2 hours, and then filtered to obtain solid powder product I; solid powder product I is added to 0.5 mol / L hydrochloric acid and stirred at room temperature for 4 hours, and then filtered to obtain solid powder product II; solid powder product II is dispersed in 0.5% HF solution and stirred for 4 hours to leach, filtered and rinsed with deionized water several times to obtain solid powder III; solid powder III is placed in a vacuum drying oven and vacuum dried at 60°C for 10 hours to obtain porous nano-silicon material preform.
[0073] (5) The porous nano-silicon material preform was annealed under an argon atmosphere at a temperature of 700°C for 4 hours to obtain the porous nano-silicon anode material.
[0074] The application of a porous nano-silicon anode material as a battery material is as follows:
[0075] The porous nano-silicon anode material prepared in this comparative example has a nanosheet structure and a single-element silicon crystalline phase. Using this porous nano-silicon anode material as the positive electrode, a lithium metal sheet as the negative electrode, and a Celgard membrane as the separator, the electrolyte consisted of LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio 3:7) with 10 wt% fluoroethylene carbonate (FEC). The binder consisted of polyacrylic acid (PAA) and sodium carboxymethyl cellulose (CMC, 6 wt%) (PAA / CMC volume ratio 1:1). The working electrode was prepared with silicon nanosheets, conductive carbon black Super-P, and binder in a weight ratio of 7:1.5:1.5. The battery was assembled in an argon-filled glove box, and constant current charge-discharge tests were performed. The porous nano-silicon anode material exhibited a reversible capacity of 900 mAh / g after 2000 cycles at a current density of 200 mA / g.
[0076] according to Figure 5 It can be seen that the electrode surface of the porous nano-silicon anode material without copper doping has more cracks before and after cycling, the silicon electrode expands more severely, and the electrochemical performance is poor.
[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a copper-doped porous nano-silicon anode material, characterized in that, Includes the following steps: (1) Mix copper salt solution with montmorillonite and let stand, then filter, collect and vacuum dry to obtain copper ion doped montmorillonite; the mass-volume ratio of montmorillonite to copper salt solution is (0.1~1):(1~10); the concentration of copper salt solution is 0.1~10 mol / L; (2) Copper ion-doped montmorillonite, magnesium powder and metal chloride are mixed evenly under anhydrous and oxygen-free conditions to obtain molten salt-assisted magnesium thermal reduction raw material; the mass ratio of copper ion-doped montmorillonite, magnesium powder and metal chloride is 1:(0.1~5):(1~10); (3) The molten salt-assisted magnesium thermal reduction raw material is subjected to magnesium thermal reduction reaction in an anhydrous and oxygen-free atmosphere to obtain a mixture containing copper-doped nano-silicon material; (4) The mixture of copper-doped nano-silicon materials was washed and filtered sequentially with water and acid solution, and the filtered product was vacuum dried to obtain copper-doped porous nano-silicon material preform. (5) The copper-doped porous nano-silicon material preform is heat-treated in a protective gas to obtain the copper-doped porous nano-silicon anode material.
2. The method for preparing the copper-doped porous nano-silicon anode material according to claim 1, characterized in that, The copper salt is at least one of copper chloride, copper sulfate, and copper nitrate; the metal chloride is at least one of sodium chloride, potassium chloride, magnesium chloride, and calcium chloride.
3. The method for preparing copper-doped porous nano-silicon anode material as described in claim 1, characterized in that, The temperature of the magnesium thermal reduction reaction is 400~1000℃, and the time is 1~36h.
4. The method for preparing copper-doped porous nano-silicon anode material as described in claim 1, characterized in that, In step (4), the acid solution cleaning includes cleaning with A acid first, followed by cleaning with B acid; A acid is at least one of hydrochloric acid, sulfuric acid, and nitric acid, and B acid is at least one of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid.
5. The method for preparing the copper-doped porous nano-silicon anode material as described in claim 4, characterized in that, The concentration of the A acid is 0.01~5 mol / L, and the washing time is 1 min~10 h; the mass percentage concentration of the B acid is 0.01%~10%, and the washing time is 1 min~10 h.
6. The method for preparing copper-doped porous nano-silicon anode material as described in claim 1, characterized in that, The vacuum drying process is performed at a temperature of 40-80°C for 1 minute to 24 hours.
7. The method for preparing copper-doped porous nano-silicon anode material as described in claim 1, characterized in that, The heat treatment temperature is 300~1000℃, and the time is 1min~24h.
8. The method for preparing copper-doped porous nano-silicon anode material as described in claim 1, characterized in that, The anhydrous and oxygen-free atmosphere is one or more of nitrogen, argon, hydrogen, and helium.