Layered silicate materials, methods for their preparation and use

Abstract

This invention provides layered silicon materials, their preparation methods, and applications. The preparation method includes: grinding and mixing silicon powder with metallic lithium, heat-treating under a protective atmosphere, and cooling to obtain a lithium-silicon alloy; mixing and stirring the lithium-silicon alloy with an organic solvent, first adding alcohol for alcohol elution to remove lithium, then acid washing and drying to obtain the layered silicon material. This method can produce a porous silicon structure formed by stacking ultrathin nano-silicon wafers. The pores between the ultrathin wafer layers form low-torsion ion channels, which can significantly accelerate the diffusion rate of lithium ions in the electrode, significantly improve the rate performance of the silicon material, and the porous structure formed by the stacked layers can provide a buffer space for the volume change of the active material during charging and discharging, reducing the risk of particle breakage and active material shedding; at the same time, the uniform stress distribution can also stabilize the electrode interface and extend the cycle life. This method is simple, safe, and energy-efficient.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery materials technology, specifically relating to layered silicon materials, their preparation methods, and applications. Background Technology

[0002] High energy density is a core goal that the scientific and industrial communities in the field of lithium-ion batteries have been continuously pursuing, but the theoretical specific capacity of graphite anodes is only 372 mAh g. -1 This significantly limits the improvement of battery energy density. In contrast, silicon anode materials have a reversible specific capacity as high as 3579 mAh g⁻¹. -1 Silicon anodes have a lithium intercalation potential approximately 10 times that of graphite; they also possess a high lithium intercalation potential, effectively suppressing lithium plating and thus improving battery safety. However, silicon anodes suffer from severe volume expansion, poor interface stability, and insufficient conductivity during cycling, hindering their commercial application. Therefore, developing silicon anode materials that combine high capacity and high stability has significant theoretical and engineering value.

[0003] Nanostructuring silicon materials can effectively mitigate volume effects during cycling. For example, patent application CN115010135B discloses a two-dimensional silicon nanosheet anode material, which effectively improves the cycling stability of silicon anode materials. The design of porous silicon anodes not only buffers volume expansion but also promotes electrolyte wetting, improving the cycling and rate performance of silicon anode materials. For instance, patent application CN119352048A discloses a porous nanostructured silicon anode material with a capacity retention of 57% after 200 cycles. Therefore, organically combining the advantages of two-dimensional layered silicon materials and porous silicon materials to develop a two-dimensional porous silicon anode is an effective means to improve the electrochemical performance of silicon anode materials.

[0004] Alloying is an effective way to control the morphology of porous silicon. Patent application CN106629736B discloses a method for preparing porous silicon powder; patent application CN116282030A discloses a porous silicon material, its preparation method, and its applications. However, the materials prepared by the above patents exhibit a honeycomb structure, failing to achieve synergy between morphology control (two-dimensional silicon nanosheets) and structure control (porous structure), resulting in insignificant improvement in electrochemical performance. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned problems of the prior art, and its purpose is to provide layered silicon materials, their preparation methods and applications.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a method for preparing layered silicon materials is provided, including: Silicon powder and metallic lithium are ground and mixed, heat-treated under a protective atmosphere, and then cooled to obtain a lithium-silicon alloy. After mixing and stirring the lithium-silicon alloy with an organic solvent, alcohol is first added dropwise for alcohol washing to remove lithium, followed by acid washing and drying to obtain layered silicon material.

[0007] Secondly, a layered silicon material is provided, which is prepared using the preparation method described in the first aspect.

[0008] Thirdly, an electrochemical energy storage device is provided, comprising the layered silicon material described in the second aspect.

[0009] Specifically, the present invention applies the above-mentioned silicon material to lithium battery anode materials. Compared with raw silicon, the layered silicon material has significantly improved cycle stability and rate performance.

[0010] This invention discloses a method for preparing layered silicon materials. The method involves synthesizing a lithium-silicon alloy and innovatively pre-dispersing it using certain organic solvents. Solvent molecules insert into the alloy lattice, pre-weakening interlayer forces. Furthermore, the lithium removal reaction kinetics are actively regulated by adding alcohol dropwise, thereby safely and controllably guiding the lithium removal process. The final result is a three-dimensional porous structure formed by stacked and interlaced silicon nanosheets, which effectively promotes ion transport and adapts to volume changes.

[0011] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: 1. This invention provides a simple, safe, and low-energy-consumption method for synthesizing layered porous silicon materials. First, lithium metal and silicon are mixed and calcined to synthesize a lithium-silicon alloy. Then, an organic solvent is introduced, followed by alcohol washing and acid washing of the lithium. This method can produce porous silicon structures formed by stacking ultrathin nano-silicon wafers.

[0012] 2. In this invention, lithium-silicon alloy is pre-dispersed using organic solvents. The organic solvents, as a medium, can dilute and uniformly disperse the alcohols that subsequently participate in the reaction, thus transforming the lithium removal reaction from severe surface corrosion to a gentle, controllable process from the outside in.

[0013] 3. The organic solvent used in this invention has molecules that can insert into the interstitial spaces of the lithium-silicon alloy lattice or adsorb onto specific crystal planes, pre-weakening interlayer forces and reducing interfacial energy in specific directions. During subsequent delithiation, lithium extraction preferentially proceeds along these pre-treated weakened paths, thereby guiding the material to expand in a directional manner and forming a layered structure that is more conducive to ion transport and adaptability to volume changes.

[0014] 4. The porous silicon material prepared by this invention, formed by stacking ultrathin nano-silicon wafers, has a large interlayer spacing, and the pores between the layers form low-torsion ion channels, which can significantly accelerate the diffusion rate of lithium ions in the electrode and significantly improve the rate performance of the silicon material. In addition, the porous structure formed by stacking layers can provide a buffer space for the volume change of the active material during charging and discharging, reducing the risk of particle breakage and active material shedding; at the same time, the uniform stress distribution can also stabilize the electrode interface and extend the cycle life.

[0015] 5. The porous silicon material formed by stacking ultrathin nano-silicon wafers synthesized in this invention exhibits excellent performance in lithium-ion battery anodes. Compared with raw silicon, the cycle stability and rate performance of the sample of this invention are significantly improved. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the 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 based on these drawings without creative effort.

[0017] Figure 1 The image shows the XRD pattern of the layered silicon material prepared in Example 1. Figures 2-3 This is a scanning electron microscope image of the layered silicon material prepared in Example 1; Figure 4 A scanning electron microscope image of the silicon material prepared in Comparative Example 1; Figure 5 The silicon material prepared in Example 1 and Comparative Example 1, along with the battery assembled with nano-silicon, were used in a 2A g test. -1 Cyclic performance at current density; Figure 6 The rate performance diagram shows the battery assembled from the layered silicon material and nano-silicon prepared in Example 1. Figure 7 The battery assembled from the layered silicon material prepared in Example 1 was tested at 0.2 A g. -1 First charge-discharge curves at current density; Figure 8 The graph shows the rate performance of batteries assembled from the layered silicon materials prepared in Examples 1, 4-6. Detailed Implementation

[0018] Some embodiments provide a method for preparing layered silicon materials, including: Silicon powder and metallic lithium are ground and mixed, heat-treated under a protective atmosphere, and then cooled to obtain a lithium-silicon alloy. After mixing and stirring the lithium-silicon alloy with an organic solvent, alcohol is first added dropwise for alcohol washing to remove lithium, followed by acid washing and drying to obtain layered silicon material.

[0019] It should be noted that when eluting lithium with alcohol, the purpose of adding alcohol is to control the rate of alcohol addition. Otherwise, the reaction will be very vigorous and accompanied by a large amount of exothermic reaction, affecting the silicon morphology. Specifically, the addition can be performed according to conventional dropwise operation, such as using a dropper. The dropping rate can be controlled according to the exothermic reaction conditions, for example, a dropping rate of 3~8 mL / min.

[0020] In some implementations, cooling can be achieved through furnace cooling.

[0021] In some embodiments, the heat treatment under a protective atmosphere may specifically involve placing the mixture in a sealed crucible and performing heat treatment under an inert gas atmosphere. The crucible may be a nickel crucible, an alumina crucible, or a graphite crucible, etc.

[0022] In some preferred embodiments, the silicon powder is nano-silicon powder; the particle size of the silicon powder is 100~500nm, such as 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.

[0023] In some preferred embodiments, the lithium metal is lithium powder or lithium particles; the particle size of the lithium powder is 30~50μm, for example 30μm, 32μm, 35μm, 38μm, 40μm, 42μm, 45μm, 48μm, 50μm, etc.

[0024] In some preferred embodiments, the mass ratio of lithium metal to silicon powder is 1:1 to 2, such as 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, etc.

[0025] In some preferred embodiments, the protective atmosphere is one or a combination of two of argon, nitrogen, or helium.

[0026] In some preferred embodiments, the heat treatment temperature is 400~800℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, etc.

[0027] In some preferred embodiments, the heat treatment time is 1 to 4 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, etc.

[0028] In some preferred embodiments, the organic solvent is one or more of NMP, DMC, and EMC.

[0029] In some preferred embodiments, the solid-liquid ratio of the lithium-silicon alloy to the organic solvent is (0.1~5)g:(10~50)mL, for example, 0.1g:50mL, 0.5g:50mL, 1g:50mL, 1g:45mL, 1g:40mL, 1g:35mL, 1g:30mL, 1g:25mL, 1g:20mL, 1g:18mL, 1g:15mL, 1g:12mL, 1g:10mL, 1g:9mL, 1g:8mL, 1g:7mL, 1g:6mL, 1g:5mL, 1g:4.5mL, 1g:4mL, 1g:3.5mL, 1g:3mL, 1g:2.5mL, 1g:2mL, etc. In some preferred embodiments, the lithium-silicon alloy is further ground before mixing and stirring with the organic solvent.

[0030] In some preferred embodiments, the mixing and stirring time is 0.1 to 1 hour, for example, 0.1 hour, 0.2 hour, 0.3 hour, 0.4 hour, 0.5 hour, 0.6 hour, 0.7 hour, 0.8 hour, 0.9 hour, 1 hour, etc.

[0031] In some preferred embodiments, the alcohol is one or more of anhydrous ethanol, isopropanol, methanol, ethylene glycol, glycerol, etc.

[0032] In some preferred embodiments, the solid-liquid ratio of the lithium-silicon alloy to the alcohol is (0.1~5)g:(100~500)mL, for example, 0.1g:500mL, 0.1g:400mL, 0.1g:300mL, 0.1g:200mL, 0.1g:100mL, 0.3g:100mL, 0.5g:100mL, 0.8g:100mL, 1g:100mL, 1.5g:100mL, 2g:100mL, 2.5g:100mL, 3g:100mL, 3.5g:100mL, 4g:100mL, 4.5g:100mL, 5g:100mL, etc.

[0033] In some preferred embodiments, the alcohol washing time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.

[0034] In some preferred embodiments, the alcohol washing for lithium removal by adding alcohol includes: placing the mixture obtained by mixing and stirring in an ice-water bath, adding alcohol dropwise to the mixture, and then stirring and washing the mixture at 15~30°C after the alcohol has been added.

[0035] In some preferred embodiments, the acid is one or more of formic acid, acetic acid, propionic acid, butyric acid, etc.

[0036] In some preferred embodiments, the drying is freeze-drying.

[0037] It is worth noting that after alcohol washing, solid-liquid separation (such as filtration) is performed before acid washing.

[0038] Some embodiments of the present invention provide a layered silicon material, which is prepared using the aforementioned preparation method. In some preferred embodiments, the layered silicon material has a size of 10-20 μm, such as 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.; the thickness of the ultrathin nano-silicon wafers constituting the porous silicon is 5-10 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc. Ultrathin nano-silicon wafers help reduce ion diffusion paths, improve ion transport performance, and enhance initial coulombic capacity and high-rate electrical performance.

[0039] Some embodiments provide an electrochemical energy storage device, including the aforementioned layered silicon material.

[0040] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0041] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0043] Example 1 This embodiment provides a method for preparing a layered silicon material, the method comprising the following steps: (1) Grind and mix nano-silicon powder with an average particle size of 100 nm and lithium powder in an inert atmosphere (such as a glove box), transfer them to a sealed crucible and calcine them in an argon atmosphere to obtain a lithium-silicon alloy.

[0044] The mass ratio of silicon to lithium is 1.4:1, the calcination temperature is 600℃, and the calcination time is 2h. (2) After grinding, the lithium-silicon alloy is mixed with NMP to form a liquid phase system. After stirring for 0.5 h, it is placed in an ice-water bath and anhydrous ethanol is added dropwise. After the anhydrous ethanol is added, the lithium is removed by stirring at room temperature for 2 h. After the reaction, the mixture is filtered and then washed with acetic acid for 2 h. After filtration, the lithium is removed by stirring and then filtered and freeze-dried to obtain the final product.

[0045] The solid-liquid ratio of lithium silicon alloy and NMP is 1g:20mL, and the solid-liquid ratio of lithium silicon alloy and anhydrous ethanol is 1g:300mL.

[0046] The XRD pattern of the final product is shown below. Figure 1 As shown, by Figure 1 It can be seen that the product is amorphous silicon.

[0047] The SEM image of the final product is shown below. Figures 2-3 As shown, by Figures 2-3 It can be seen that the prepared silicon material is a layered porous silicon material, and the size of the layered silicon material is 10~20μm. The layered porous silicon material is a loose porous structure formed by stacking ultrathin nano-silicon wafers, and the thickness of the ultrathin nano-silicon wafers is 5~10nm.

[0048] Example 2 This embodiment provides a method for preparing a layered silicon material, the method comprising the following steps: (1) Grind and mix nano-silicon powder with an average particle size of 100 nm and lithium powder in an inert atmosphere (such as a glove box), transfer them to a sealed crucible and calcine them in an argon atmosphere to obtain a lithium-silicon alloy.

[0049] The mass ratio of silicon to lithium is 1.7:1, the calcination temperature is 500℃, and the calcination time is 2h. (2) After grinding, the lithium-silicon alloy is mixed with NMP to form a liquid phase system. After stirring for 0.5 h, it is placed in an ice-water bath and anhydrous ethanol is added dropwise. After the anhydrous ethanol is added, the lithium is removed by stirring at room temperature for 2 h. After the reaction, the mixture is filtered and then washed with acetic acid for 2 h. After filtration, the lithium is removed by stirring and then filtered and freeze-dried to obtain the final product.

[0050] The solid-liquid ratio of lithium silicon alloy and NMP is 1g:20mL, and the solid-liquid ratio of lithium silicon alloy and anhydrous ethanol is 1g:300mL.

[0051] Example 3 This embodiment provides a method for preparing a layered silicon material, the method comprising the following steps: (1) Grind and mix nano-silicon powder with an average particle size of 100 nm and lithium powder in an inert atmosphere (such as a glove box), transfer them to a sealed crucible and calcine them in an argon atmosphere to obtain a lithium-silicon alloy.

[0052] The mass ratio of silicon to lithium is 1:1, the calcination temperature is 600℃, and the calcination time is 2h. (2) After grinding, the lithium-silicon alloy is mixed with NMP to form a liquid system. After stirring for 0.5 h, it is placed in an ice-water bath and anhydrous ethanol is added dropwise. After the anhydrous ethanol is added, the lithium is removed by stirring at room temperature for 2 h. After the reaction, the mixture is filtered and then washed with acetic acid for 2 h. After filtration, the lithium is washed by stirring and filtering again. Finally, the product is freeze-dried to obtain the final product.

[0053] The solid-liquid ratio of lithium silicon alloy and NMP is 1g:20mL, and the solid-liquid ratio of lithium silicon alloy and anhydrous ethanol is 1g:300mL.

[0054] Example 4 This embodiment is similar to Embodiment 1, except that the calcination temperature is 400℃.

[0055] Example 5 This embodiment is similar to Embodiment 1, except that the calcination temperature is 500℃.

[0056] Example 6 This embodiment is similar to Embodiment 1, except that the calcination temperature is 700℃.

[0057] Comparative Example 1 The difference from Example 1 is that step (2) is different. Specifically, step (2) is as follows: The lithium-silicon alloy was ground and placed in a reaction vessel. The reaction vessel was placed in an ice-water bath, and anhydrous ethanol was added dropwise. After the anhydrous ethanol was added, the mixture was stirred at room temperature for 2 hours to carry out the delithiation reaction. After the reaction, the mixture was filtered, and then the lithium was washed with acetic acid for 2 hours with stirring. After filtration, the mixture was freeze-dried to obtain the final product.

[0058] The solid-liquid ratio of lithium silicon alloy and anhydrous ethanol is 1g:300mL.

[0059] SEM images of the obtained silicon material are as follows: Figure 4 As shown, by Figure 4 It can be seen that the product is in a porous aggregated state, with the size of a single secondary particle being approximately 200~500nm, and the morphology being an irregular block shape, with the aggregate size reaching 1~3μm.

[0060] Performance testing: Using the silicon materials prepared in the above embodiments and comparative examples, as well as the raw material nano-silicon powder (average particle size 100 nm), as active materials, 0.07 g of active material, 0.02 g of sodium alginate, and 0.01 g of Super P (the mass ratio of active material: binder: conductive agent is 7:2:1) were weighed out and ground for 10 min. Then, a mixture of 0.4 mL of ethanol and water (volume ratio 1:3) was added, and grinding continued for 20 min to obtain a slurry. Copper foil was placed in an automatic coating machine, and the slurry was coated onto the surface of the copper foil. After starting the machine, the slurry was uniformly coated onto the surface of the copper foil, with a coating thickness of 100 μm and a coating speed of 10 mm / s. -1 The electrodes were dried in an 80℃ vacuum drying oven for 10-12 hours, and then cut into 12mm circular electrodes. The mass of the electrodes and empty foil was weighed to calculate the mass of the active material. The electrodes, CR2025 battery casing, and separator were dried in a 50℃ vacuum drying oven for 2 hours and then placed in a glove box (H2O ≤ 0.1ppm, O2 ≤ 0.1ppm). A 14mm diameter, 0.3mm thick lithium metal sheet was used as the counter electrode. The electrolyte was 1M LiPF6 / EC:DEC (volume ratio 1:1) + 10wt.% FEC. After battery assembly, the battery was left to stand for 12 hours before subsequent electrochemical testing.

[0061] The charge-discharge cycle performance and rate performance of button cells were tested using the Blue Battery Testing System. The charge-discharge cutoff voltage range was 0.01~2V. All tested cells were first subjected to a 0.2A g test. -1 Activation was performed by cycling three times at a current density, and the test temperature was 25°C. The same electrochemical performance testing method was used for all examples.

[0062] In Example 1 and Comparative Example 1, the silicon material and raw material nano-silicon powder prepared respectively were used as active materials in the assembly of batteries at 0.2 A g. -1 After activation, at 2A g -1 Cyclic performance such as Figure 5 As shown; the rate performance of batteries assembled using Example 1 and raw material nano-silicon powder as active materials is as follows. Figure 6 As shown; the silicon material prepared in Example 1 was in a concentration of 0.2 A g. -1 The first charge-discharge curve is as follows: Figure 7 As shown; the rate performance of batteries assembled using silicon materials prepared in Examples 1, 4-6 as active materials is as follows. Figure 8 As shown.

[0063] Depend on Figure 5 It can be seen that the layered silicon material prepared in Example 1 has significantly better cycle performance than the silicon material prepared by nano-silicon powder and Comparative Example 1; Figure 6It can be seen that the layered silicon material prepared in Example 1 has significantly better rate performance than nano-silicon powder.

[0064] Depend on Figure 8 It can be seen that as the calcination temperature increases, the rate performance first increases and then decreases.

[0065] Examples 1-6, batteries assembled using silicon material prepared in Comparative Example 1 as the active material, were tested at 0.2 A g. -1 Activation at 2A g and at 2A g -1 The electrochemical performance data are shown in Table 1.

[0066] Table 1 Electrochemical performance data of batteries assembled from silicon materials prepared in Examples 1-6 and Comparative Example 1 analyze: As can be seen from the test data in the table above, the layered silicon material prepared by the process of this invention exhibits excellent electrochemical performance when used as a negative electrode material for lithium-ion batteries.

[0067] Comparing the experimental data from Examples 1 and 4-6 reveals that during the synthesis of lithium-silicon alloys, if the calcination temperature is too low, the fusion degree between the lithium and silicon phases will be insufficient, making it difficult to construct the target nanolayered porous structure. This ultimately leads to a significant reduction in the material's initial coulombic efficiency and high-rate performance. If the calcination temperature of the lithium-silicon alloy is too high, it will promote agglomeration of the alloy, forming blocky aggregates with a particle size of 20-40 μm. However, after delithiation treatment, the silicon material can still maintain a micron-scale nanolayered porous structure. This indicates that increasing the calcination temperature does not destroy the layered porous morphology of the material. However, its agglomeration leads to a smaller specific surface area, and the relatively thick silicon wafer will lengthen the diffusion distance of ions in the solid phase, which is not conducive to rapid charge and discharge (high-rate performance).

[0068] The data comparison results of Examples 1 and 3 show that when the lithium source ratio is too high, it is easy to induce the individual agglomeration of metallic lithium, resulting in the lithium-silicon alloy exhibiting stronger metallic characteristics. After delithiation treatment, only spherical channels remain on the surface of the silicon substrate, and a nano-layered porous structure cannot be formed, which in turn causes a decrease in the material's initial coulombic efficiency and capacity.

[0069] As can be seen from the comparison of data from Example 1 and Comparative Example 1, the addition of organic solvents can guide the material to expand in a directional manner, forming a layered structure that is more conducive to ion transport and adapting to volume changes.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing layered silicon materials, characterized in that, include: Silicon powder and metallic lithium are ground and mixed, heat-treated under a protective atmosphere, and then cooled to obtain a lithium-silicon alloy. After mixing and stirring the lithium-silicon alloy with an organic solvent, alcohol is first added dropwise for alcohol washing to remove lithium, followed by acid washing and drying to obtain layered silicon material.

2. The method for preparing layered silicon material as described in claim 1, characterized in that, The silicon powder is nano-silicon powder; the particle size of the silicon powder is 100~500nm; The lithium metal is lithium powder or lithium particles; the particle size of the lithium powder is 30~50μm; the particle size of the lithium particles is 0.1~1mm.

3. The method for preparing layered silicon material as described in claim 1, characterized in that, The mass ratio of lithium metal to silicon powder is 1:1~2.

4. The method for preparing layered silicon material as described in claim 1, characterized in that, The protective atmosphere is one or a combination of two of argon, nitrogen, or helium; the heat treatment temperature is 400~800℃; and the heat treatment time is 1~4h.

5. The method for preparing layered silicon material as described in claim 1, characterized in that, The organic solvent is one or more of NMP, DMC, and EMC; The solid-liquid ratio of the lithium-silicon alloy to the organic solvent is (0.1~5)g:(10~50)mL; The mixing and stirring time is 0.1~1h; Before mixing and stirring the lithium-silicon alloy with the organic solvent, the lithium-silicon alloy is also ground.

6. The method for preparing layered silicon material according to claim 1, characterized in that, The alcohol is one or more selected from anhydrous ethanol, isopropanol, methanol, ethylene glycol, and glycerol; The solid-liquid ratio of the lithium-silicon alloy to the alcohol is (0.1~5)g:(100~500)mL.

7. The method for preparing layered silicon material as described in claim 1, characterized in that, The alcohol washing time is 1-3 hours; The method of adding alcohol for alcohol washing to remove lithium includes: placing the mixture obtained by mixing and stirring in an ice-water bath, adding alcohol dropwise to the mixture, and then stirring and washing the mixture at 15~30℃ after the alcohol has been added. The acid is one or more of formic acid, acetic acid, propionic acid, and butyric acid; The drying process is freeze-drying; After alcohol washing, solid-liquid separation is performed, and then the solid obtained from solid-liquid separation is acid washed.

8. A layered silicon material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. The layered silicon material as described in claim 8, characterized in that, The layered silicon material has a size of 10~20μm; the layered silicon material is a layered porous silicon material; the layered porous silicon material is composed of ultrathin nano-silicon wafers; the thickness of the ultrathin nano-silicon wafers is 5~10nm.

10. An electrochemical energy storage device, characterized in that, Including the layered silicon material as described in claim 8 or 9.

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