A simple method for preparing two-dimensional Si / SiO x Methods and their applications in lithium / sodium batteries

Abstract

This invention provides a simple method for preparing two-dimensional Si / SiO2. x The method and its application in lithium / sodium batteries, the preparation includes the following steps: (1) at room temperature, silicon-calcium alloy is added to acetic acid solution, chloride solution is added to it, and the mixture is stirred until the reaction is complete; (2) the solution is filtered and dried to obtain two-dimensional Si / SiOx powder. The preparation process is simple, and two-dimensional Si / SiOx can be obtained by one-step acid etching. x The powder yields a material with a uniform two-dimensional structure, reducing processing steps and costs. It can be prepared at room temperature and pressure, without the need for high temperature, high pressure, or special environments. The yield of the Si / SiOx product can be controlled by adjusting the concentrations of acetic acid and ferric chloride. The prepared two-dimensional Si / SiOx... x The powder not only retains excellent electrochemical performance, but also requires simpler and more environmentally friendly preparation conditions, allowing for the one-step preparation of two-dimensional Si / SiO₂. x The material requires no further processing.

Description

Technical Field

[0001] This invention belongs to the field of energy storage and conversion, specifically relating to a simple method for preparing two-dimensional Si / SiO2. x The method and its application in lithium / sodium batteries. Background Technology

[0002] Silicon materials possess advantages such as high lithium storage capacity, low operating voltage, non-toxicity, and abundant reserves, making them promising candidates for applications in the battery field. However, silicon anodes experience rapid volume expansion (~400%) during cycling, leading to silicon pulverization and fragmentation, hindering the continuous growth of the SEI film and causing rapid performance degradation in the battery. Silicon oxides, formed by the combination of silicon and oxygen, can buffer the volume expansion of silicon (<200%) during the first cycle with the generated Li2O and some lithium silicates, achieving better cycle stability. However, their theoretical capacity is significantly lower than that of silicon materials, hindering the commercial application of silicon or silicon oxides in battery energy storage.

[0003] One way to solve the above problems is to prepare two-dimensional Si / SiO. x Composite materials. Si can provide a higher theoretical specific capacity; on the other hand, SiO... x This method can limit the volume expansion of silicon during charging and discharging, thus improving its electrochemical performance. Furthermore, the material's two-dimensional structure can accelerate ion transport and suppress volume expansion. However, existing fabrication techniques suffer from drawbacks such as complex preparation and high cost. Therefore, a simplified method for preparing two-dimensional Si / SiO₂ is needed. x This method is very meaningful. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a simple method for preparing two-dimensional Si / SiO2. x This invention discloses a method for fabricating two-dimensional Si / SiO₂ batteries and its application therein. The method provided by this invention is simple and can successfully produce two-dimensional Si / SiO₂. x And the prepared two-dimensional Si / SiO x The powder maintains excellent electrochemical properties.

[0005] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a simple method for preparing two-dimensional Si / SiO2. x The method, wherein the preparation includes the following steps:

[0007] (1) At room temperature, add the silicon-calcium alloy into the acetic acid solution, add the chloride solution, and stir until the reaction is complete;

[0008] (2) The solution was filtered and dried to obtain two-dimensional Si / SiO2.x powder.

[0009] The chloride in step (1) includes one or two of ferric chloride, ferrous chloride, copper chloride, zinc chloride, tin chloride, and aluminum chloride.

[0010] In step (1), the concentration of acetic acid is 0.5 mol / L. -1 - 10 mol L -1 ;

[0011] In step (1), the concentration of chloride is 0.2 mol L. -1 - 5 mol L -1 ;

[0012] The stirring time in step (1) is 6 h ~ 240 h;

[0013] The drying method in step (2) includes vacuum drying and freeze drying. The vacuum drying temperature is 50 ℃~ 80 ℃, and the freeze drying temperature is -30 ℃~ -50 ℃.

[0014] In a second aspect, the present invention provides a two-dimensional Si / SiO2 obtained by the preparation method described in the first aspect. x powder.

[0015] In a third aspect, the present invention provides a lithium-ion battery, wherein the negative electrode active material is the aforementioned two-dimensional Si / SiO₂. x powder.

[0016] In a fourth aspect, the present invention provides a sodium-ion battery, wherein the negative electrode active material is the aforementioned two-dimensional Si / SiO₂. x powder.

[0017] The silicon-calcium alloy used is mainly composed of CaSi2, which is a dense layered structure in which calcium and silicon elements are arranged in close alternation. In this invention, the chloride added hydrolyzes to generate HCl and hydroxide precipitates. Acetic acid can eliminate the formation of hydroxide precipitates, while the HCl generated from hydrolysis reacts with the Ca in the silicon-calcium alloy. 2+ The reaction is carried out while keeping the Si backbone unchanged. Two-dimensional Si / SiOx precipitate is obtained by one-step acid etching. At this time, there is only this precipitate in the solution. After filtration and drying, two-dimensional Si / SiOx powder is obtained.

[0018] The present invention has the following beneficial effects:

[0019] (1) The HCl from chloride hydrolysis and the Ca in the Zintl phase silicon-calcium alloy added in this invention 2+The reaction was carried out while keeping the Si backbone unchanged, and two-dimensional Si / SiO were obtained by a one-step acid etching method. x The powder yields a material with a uniform two-dimensional structure, reducing processing steps and costs. It can be prepared at room temperature and pressure, without the need for high temperature, high pressure, or special environments, making the process simple. The Si / SiO ratio of the product can be controlled by adjusting the concentrations of acetic acid and chloride. x Production.

[0020] (2) The present invention is easy to operate, and the precursors used are all commercially available materials. The preparation process is simple and easy to mass-produce, and it is expected to be commercialized.

[0021] (3) Compared with hydrochloric acid etching, vacuum stripping, molten salt method, etc., the two-dimensional Si / SiO prepared by this invention has better results. x The powder not only retains excellent electrochemical performance, but also requires simpler and more environmentally friendly preparation conditions, allowing for the one-step preparation of two-dimensional Si / SiO₂. x The material requires no further processing. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 Two-dimensional Si / SiO2 prepared in Example 1 x XRD pattern of the material.

[0024] Figure 2 Two-dimensional Si / SiO2 prepared in Example 1 x SEM image of the material.

[0025] Figure 3 Two-dimensional Si / SiO2 prepared in Example 1 x Coulomb efficiency diagram when used as the negative electrode of a lithium-ion battery.

[0026] Figure 4 Two-dimensional Si / SiO2 prepared in Example 1 x Cycle performance diagram when used as the negative electrode of a lithium-ion battery. Detailed Implementation

[0027] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments; the raw materials involved in the following embodiments are all purchased through commercial channels.

[0029] Example 1

[0030] A simple preparation of two-dimensional Si / SiO x Method:

[0031] (1) Acid stripping: Prepare 50 mL of 5 mol L at room temperature. -1 A solution of acetic acid was prepared by slowly adding 2 g of silicon-calcium alloy to it, followed by the addition of ferric chloride while stirring, to produce a 2 mol / L solution. -1 A ferric chloride solution was stirred for 24 hours. During this process, ferric chloride hydrolyzed to produce HCl, which reacted with calcium in the silicon-calcium alloy under acidic conditions, while the more stable silicon backbone remained unchanged, thus forming a two-dimensional structure.

[0032] (2) Centrifuge the solution after stirring and filtration, wash with deionized water until neutral, and dry the powder in a vacuum oven at 80°C. o After heating at C for 24 hours, two-dimensional Si / SiO can be obtained. x powder. Figure 1 The XRD pattern confirms the successful preparation of Si / SiO. x , Figure 2 The SEM image demonstrates the two-dimensional structure of the product.

[0033] (3) Performance testing: using two-dimensional Si / SiO x Lithium foil was used as the negative electrode active material, serving as both the counter and reference electrode. The electrolyte used was LiPF6+EC / DEC / 10% FEC, with a voltage range of 0.01V-3.0V. At 200 mA g... -1 Tested at a current density, the capacity retention rate was 95% after 100 cycles, demonstrating the excellent electrochemical performance of the material. Figure 3 and Figure 4 The figures show the coulombic efficiency and cycle performance of the battery, respectively. It can be seen that the lithium-ion battery using two-dimensional Si / SiOx as the negative electrode maintains a stable coulombic efficiency of around 100% after 300 cycles and possesses a high discharge capacity, demonstrating the excellent electrochemical performance of this material.

[0034] Example 2

[0035] A simple preparation of two-dimensional Si / SiO x Method:

[0036] (1) Acid stripping: At room temperature, prepare 50 mL of 3 mol L...-1 A solution of acetic acid was prepared by slowly adding 1.2 g of silicon-calcium alloy to it, followed by the addition of zinc chloride while stirring, to produce a 2 mol / L solution. -1 The zinc chloride solution was stirred for 24 hours.

[0037] (2) After stirring and reacting, the solution is centrifuged, filtered, washed with deionized water until neutral, and the powder is freeze-dried in a freeze dryer for 48 h to obtain two-dimensional Si / SiO. x powder.

[0038] Example 3

[0039] A simple preparation of two-dimensional Si / SiO x Method:

[0040] (1) Acid stripping: At room temperature, prepare 50 mL of 4 mol L... -1 A 1.5 g silicon-calcium alloy was slowly added to an acetic acid solution, and ferric chloride was added while stirring to prepare a 1.5 mol / L solution. -1 The ferric chloride solution was stirred for 24 hours.

[0041] (2) After stirring and reacting, the solution is centrifuged, filtered, washed with deionized water until neutral, and the powder is freeze-dried in a freeze dryer for 48 h to obtain two-dimensional Si / SiO. x pink

[0042] Example 4

[0043] A simple preparation of two-dimensional Si / SiO x Method:

[0044] (1) Acid stripping: At room temperature, prepare 50 mL of 5 mol L... -1 A solution of acetic acid was prepared by slowly adding 2 g of silicon-calcium alloy to it, followed by the addition of copper chloride while stirring, to produce a 2 mol / L solution. -1 The copper chloride solution was stirred for 24 hours.

[0045] (2) After stirring and reacting, the solution is centrifuged, filtered, washed with deionized water until neutral, and the powder is freeze-dried in a freeze dryer for 48 h to obtain two-dimensional Si / SiO. x pink

[0046] Example 5

[0047] A simple preparation of two-dimensional Si / SiO x Method:

[0048] (1) Acid stripping: At room temperature, prepare 50 mL of 5 mol L... -1A solution of acetic acid was prepared by slowly adding 3 g of silicon-calcium alloy to it, followed by the addition of aluminum chloride while stirring, to produce a 3 mol / L solution. -1 The aluminum chloride solution was stirred for 24 hours.

[0049] (2) After stirring and reacting, the solution is centrifuged, filtered, washed with deionized water until neutral, and the powder is freeze-dried in a freeze dryer for 48 h to obtain two-dimensional Si / SiO. x pink.

[0050] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Although the specific embodiments of the present invention have been described above, they are not intended to limit the protection scope of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A simple method for preparing two-dimensional Si / SiO x The method is characterized by, The method includes the following steps: (1) At room temperature, add the silicon-calcium alloy into the acetic acid solution, add the chloride solution, and stir until the reaction is complete; (2) The solution obtained in (1) was filtered and dried to obtain two-dimensional Si / SiO. x powder; The acetic acid solution is 50 mL of 5 mol / L. -1 The amount of silicon-calcium alloy used is 2 g, and the concentration of the chloride solution is 2 mol / L. -1 The chloride is ferric chloride; Alternatively, the acetic acid solution is 50 mL of 3 mol / L. -1 The amount of silicon-calcium alloy used is 1.2 g, and the concentration of the chloride solution is 2 mol / L. -1 The chloride is zinc chloride; Alternatively, the acetic acid solution is 50 mL of 4 mol / L. -1 The amount of silicon-calcium alloy used is 1.5 g, and the concentration of the chloride solution is 1.5 mol / L. -1 The chloride is ferric chloride; Alternatively, the acetic acid solution is 50 mL of 5 mol / L. -1 The amount of silicon-calcium alloy used is 2 g, and the concentration of the chloride solution is 2 mol / L. -1 The chloride is copper chloride; Alternatively, the acetic acid solution is 50 mL of 5 mol / L. -1 The amount of silicon-calcium alloy used is 3 g, and the concentration of the chloride solution is 3 mol / L. -1 The chloride is aluminum chloride.

2. The method as described in claim 1, characterized in that, The stirring time in step (1) is 6 h ~ 240 h.

3. The method as described in claim 1, characterized in that, The drying methods in step (2) include vacuum drying and freeze drying.

4. The method as described in claim 3, characterized in that, Vacuum drying temperature is 50 ℃ ~ 80 ℃, and freeze drying temperature is -30 ℃ ~ -50 ℃.

5. Two-dimensional Si / SiO₂ prepared by the method according to any one of claims 1-4 x powder.

6. A lithium-ion battery, characterized in that, The negative electrode active material is the two-dimensional Si / SiO as described in claim 5. x powder.

7. A sodium-ion battery, characterized in that, The negative electrode active material is the two-dimensional Si / SiO as described in claim 5. x powder.

Images