A simple self-supporting siloxene@MXene material and its application

Abstract

The present invention belongs to the field of energy storage and conversion, and relates to a self-supporting siloxene @MXene material and its application that can be easily prepared, including: adding MAX phase raw materials to a mixed solution of hydrochloric acid and lithium fluoride, centrifuging the obtained substance after water bath heating, and obtaining a MXene colloidal solution by a stripping method; placing a silicon calcium alloy in an acidic solution and stirring, filtering and drying the solution to obtain a siloxene powder; stirring the MXene colloidal solution and the siloxene powder evenly, filtering the mixed solution, and drying to obtain a siloxene @MXene composite film. The process of the present invention is simple, and the precursors used are all selected from commercial materials, so it is expected to be commercialized; siloxene @MXene can be prepared by regulating the heat treatment time and temperature, without other complicated steps; the prepared siloxene @MXene composite film material, the composite film can be directly used as a negative electrode of a lithium ion battery, without the need to add adhesives and additives, and effectively improves the specific capacity, cycle performance and conductivity of the negative electrode of the lithium ion battery.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage and conversion, and specifically relates to a method for preparing a siloxane@MXene composite film at low cost and its application. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Silicon material as the negative electrode of lithium-ion battery has suitable working voltage, high theoretical specific capacity (3579mAh g -1 However, the silicon anode will undergo a rapid volume expansion (~400%) during the process of lithium insertion and extraction, resulting in the pulverization and fragmentation of silicon and the continuous growth of the SEI film, leading to the rapid decay of battery performance.

[0004] Silicon oxide formed by the combination of silicon material and oxygen has a relatively high theoretical capacity (>2000mAh g -1 ), and during the first cycle, the generated Li2O and part of the lithium silicate can buffer the volume expansion of silicon (<200%), obtain better cycle stability, and is considered to be a more commercially suitable negative electrode material.

[0005] MXene(M n+1 X n ) is a type of two-dimensional inorganic compound material, composed of transition metal carbides, nitrides or carbonitrides with a thickness of several atomic layers. In the chemical formula, n = 1, 2 or 3, M is an early transition metal element, and X is a carbon or nitrogen element. From the perspective of structure and performance, MXene has advantages such as large specific surface area, fast charge and discharge performance and small volume change, which makes MXene materials have unique advantages in the field of electrochemistry. However, since MXene materials are prone to interlayer accumulation and collapse during the preparation process, this limits their further development in lithium-ion batteries. Summary of the invention

[0006] In order to overcome the above problems, the present invention provides a self-supporting siloxene@MXene material that is easily prepared and its application.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a method for easily preparing a self-supporting siloxene@MXene material, comprising:

[0009] The MXene colloidal solution and the siloxene powder are mixed evenly, filtered, and dried to obtain a siloxene@MXene composite film.

[0010] In order to solve the problem that MXene materials are prone to interlayer accumulation and collapse during the preparation process, the present invention prepares a siloxene@MXene composite material. Siloxene is a new type of two-dimensional silicon oxide with small volume expansion and good cyclability. By compounding siloxene with MXene, the MXene interlayer spacing can be expanded, and the MXene structure and electrochemical properties can be improved. On the other hand, the MXene self-supporting structure can limit the volume expansion of siloxene during the charge and discharge process, and improve the electrochemical properties of siloxene.

[0011] The second aspect of the present invention provides a self-supporting siloxane@MXene material prepared by the above method.

[0012] The third aspect of the present invention provides the use of the above-mentioned self-supporting siloxene@MXene material in the preparation of batteries or supercapacitors.

[0013] The beneficial effects of the present invention are:

[0014] (1) The present invention is easy to operate, has a simple process setting, and the precursors used are all commercially available materials. The preparation process is simple and easy to mass produce, and is expected to be commercialized.

[0015] (2) By adjusting the water bath reaction temperature and time in step 1, the concentration and number of exfoliated layers of the intermediate product MXene can be adjusted, thereby changing the structure of the siloxane@MXene material;

[0016] (3) By regulating the reaction time and reaction temperature in step 2, the silicon-oxygen ratio of the intermediate siloxene can be adjusted, thereby adjusting the specific surface area of ​​the product;

[0017] (4) By regulating the mass of siloxane and the concentration of the MXene colloidal solution in step three, self-supporting siloxane@MXene composite films of different thicknesses can be produced.

[0018] (5) The present invention prepares a highly conductive siloxane@MXene composite film material, which can be directly used as the negative electrode of a lithium-ion battery without the need to add adhesives and additives, thereby effectively improving the energy density of the device.

[0019] (6) The operation method of the present application is simple, low-cost, universal, and easy to scale up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 This is the SEM image of the intermediate product MXene in Example 1.

[0022] Figure 2 This is the SEM image of the intermediate product siloxane in Example 1.

[0023] Figure 3 This is the SEM image of the siloxane@MXene composite film produced in Example 1.

[0024] Figure 4 This is the XRD pattern of siloxene and siloxene@MXene composite film in Example 1.

[0025] Figure 5 This is a cycling performance diagram of the siloxane@MXene composite film of Example 1 used as the negative electrode of a lithium-ion battery.

[0026] Figure 6 This is a cycle performance diagram of siloxane used as the battery negative electrode in Example 1.

[0027] Figure 7 This is the cycling performance diagram of MXene used as the battery negative electrode in Comparative Example 1. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] As introduced in the background technology, in view of the deficiencies in the prior art, the present invention proposes a method for preparing porous silicon, porous silicon prepared by the method, and application of the porous silicon in the battery field.

[0030] A method for preparing a siloxane@MXene composite film at low cost, the preparation comprising the following steps:

[0031] (1) adding the MAX phase raw material to a mixed solution of hydrochloric acid and lithium fluoride, heating in a water bath, centrifuging the obtained solid phase material, and obtaining a MXene colloidal solution by a stripping method;

[0032] (2) placing the silicon-calcium alloy in an acidic solution and stirring for a period of time, filtering and drying the solution to obtain siloxane powder;

[0033] (3) The MXene colloidal solution and the siloxane powder are stirred evenly, the mixed solution is filtered, and dried to obtain a siloxane@MXene composite film.

[0034] In some embodiments, the MAX phase raw material in step (1) is one or a mixture of two of Ti3AlC2, Ti3SiC2, Ti2AlC, TiNbAlC, Ti2SiC, and TiNbSiC.

[0035] In some embodiments, the hydrothermal heating temperature in step (1) is 25°C to 45°C;

[0036] In some embodiments, the hydrothermal heating time in step (1) is 20 h to 30 h;

[0037] In some embodiments, the centrifugal speed in step (1) is 3000-4500 r / min;

[0038] In some embodiments, the stripping method in step (1) is ultrasonic stripping or mechanical stripping;

[0039] In some embodiments, the acidic solution in step (2) comprises one or two of hydrochloric acid, sulfuric acid, oxalic acid, nitric acid, perchloric acid, hypochlorous acid, and phosphoric acid;

[0040] In some embodiments, the drying method in step (2) includes vacuum drying and freeze drying, the vacuum drying temperature is 50°C to 80°C, and the freeze drying temperature is -30°C to -50°C;

[0041] In some embodiments, the stirring time in step (3) is 4 h to 6 h;

[0042] In some embodiments, the drying method in step (3) includes vacuum drying and freeze drying, the vacuum drying temperature is 50°C to 60°C, and the freeze drying temperature is -30°C to -50°C;

[0043] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0044] Example 1

[0045] A low-cost method for preparing siloxane@MXene composite membranes.

[0046] (1) Mix hydrochloric acid and aqueous solution and stir evenly to prepare 8 mol L -1of hydrochloric acid solution, and then added 0.8 g of lithium fluoride thereto and stirred for 5 minutes, added Ti3AlC2 MAX phase powder thereto, heated in a water bath for 24 hours, and then centrifuged the mixed solution to neutrality, and obtained the upper MXene colloidal solution by mechanical exfoliation. Figure 1 This is the SEM image of MXene, showing the two-dimensional layered structure of MXene.

[0047] (2) Silicon-calcium alloy purchased from Zhengzhou Mechanical Research Institute was added at 1 mol L -1 The impurity silicon is stirred in a sodium hydroxide solution, and then 1 g of silicon-calcium alloy is added to 100 ml of concentrated hydrochloric acid and stirred for 24 h. The solution is washed and filtered until it is neutral, and vacuum dried to obtain siloxane powder. Figure 2 This is the SEM image of siloxane. Figure 2 It shows that the silicon-calcium alloy was successfully etched to prepare two-dimensional silicene material.

[0048] (3) 12 mg of siloxane powder and a colloidal solution containing 40 mg of MXene were mixed and stirred evenly, then filtered to form a membrane, and freeze-dried (-30°C) to obtain a siloxane@MXene composite membrane. Figure 3 This is the SEM image of the composite membrane. It can be seen that the composite membrane has a multi-layer structure and a thickness of about 20 μm. Figure 4 The XRD patterns of siloxene and siloxene@MXene composite films show that the siloxene@MXene composite film was successfully prepared.

[0049] (4) The siloxane@MXene composite film was directly used as the negative electrode material of the lithium-ion battery. In the EC / DEC / lithium hexafluorophosphate electrolyte, lithium foil was used as the counter electrode and reference electrode to assemble a button cell. Its cycle performance was as follows Figure 5 shown. Figure 6 and Figure 7 The cycling performance of batteries with only siloxane and MXene as negative electrodes is shown in Figure 2. The stable capacity after 70 cycles is 400 mAh g -1 The capacity of the composite membrane is still greater than 500 mAh g after 100 cycles. -1 , therefore, the siloxane@MXene composite film has better electrochemical performance.

[0050] Example 2

[0051] Ti3SiC2 was selected as the MAX phase, and heated in a water bath in a mixed solution of hydrochloric acid and lithium fluoride for 30 hours, and centrifuged to obtain a MXene colloidal solution. Then, the siloxane obtained by etching the silicon-calcium alloy with concentrated hydrochloric acid was mixed evenly with the MXene colloidal solution, filtered to form a film, and vacuum dried to form a film. The composite film was directly used as the negative electrode material of the lithium-ion battery, showing good electrochemical properties.

[0052] Example 3

[0053] Ti3AlC2 was selected as the MAX phase, and the MXene preparation method was the same as in Example 1. Then 6 mol L -1 The silicon-calcium alloy was stirred in the dilute hydrochloric acid solution for 36 hours and centrifuged to obtain siloxane powder. The siloxane and MXene colloidal solutions were stirred evenly, filtered to form a film, and vacuum dried to form a film. The composite film was directly used as the negative electrode material of the lithium-ion battery, showing good electrochemical performance.

[0054] Example 4

[0055] Ti3AlC2 is selected as the MAX phase, and the preparation method of MXene is as in Example 1. An acetic acid solution is selected, and the silicon calcium alloy is stirred in the acetic acid solution for 24 hours and centrifuged to obtain siloxane powder. The siloxane and MXene colloidal solutions are stirred evenly, filtered to form a film, and vacuum dried to form a film. The composite film is directly used as the negative electrode material of the lithium ion battery, showing good electrochemical properties.

[0056] Example 5

[0057] TiNbAlC was selected as the MAX phase, which was heated in a water bath in a mixed solution of hydrochloric acid and lithium fluoride for 24 hours, and then centrifuged to obtain a MXene colloidal solution. The siloxane obtained by etching the silicon-calcium alloy with concentrated hydrochloric acid was then mixed evenly with the MXene colloidal solution, filtered to form a film, and vacuum dried to form a film. The composite film was directly used as the negative electrode material of the lithium-ion battery, showing good electrochemical properties.

[0058] Comparative Example 1

[0059] Naguib Michael et al. used MXene as a negative electrode in the paper "MXene: a promising transition metal carbide anode for lithium-ion batteries" published in 2012, but the cycle capacity was very low, such as Figure 7 shown.

[0060] Finally, it should be noted that the above is only 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 aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of them with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for easily preparing a self-supporting siloxene@MXene material, characterized in that: include: (1) Mix hydrochloric acid and aqueous solution and stir evenly to prepare 8 molL -1 0.8 g of lithium fluoride was added thereto and stirred for 5 minutes, Ti3AlC2 MAX phase powder was added thereto, heated in a water bath for 24 hours, and then the mixed solution was centrifuged to neutrality, and the upper MXene colloidal solution was obtained by mechanical exfoliation; (2) Silicon-calcium alloy was heated to 1 mol L -1 Stir in sodium hydroxide solution to remove impurity silicon, then add 1g of silicon-calcium alloy to 100ml of concentrated hydrochloric acid and stir for 24h, wash and filter until the solution is neutral, and vacuum dry to obtain siloxane powder; (3) 12 mg of siloxane powder was mixed with a colloidal solution containing 40 mg of MXene and stirred evenly, then filtered to form a membrane, and freeze-dried to obtain a siloxane@MXene composite membrane.

2. The method according to claim 1, characterized in that In step (3), the freeze-drying temperature is -30°C.

3. A self-supporting siloxane@MXene material prepared by the method of claim 1 or 2.

4. Use of the self-supporting siloxene@MXene material according to claim 3 in the preparation of batteries or supercapacitors.

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