A two-dimensional SiO2-based composite material and its preparation method and application

Abstract

The application discloses a two-dimensional SiO2-based composite material and a preparation method and application thereof. The two-dimensional SiO2-based composite material comprises SiO2 nanosheets and a two-dimensional composite material; and the two-dimensional composite material is coated on the surface of the SiO2 nanosheets through electrostatic action. The application improves the electronic conductivity of the two-dimensional SiO2 and inhibits the volume expansion in the charge and discharge process through electrostatic self-assembly and two-dimensional material compounding, thereby effectively improving the electrochemical cycle stability of the SiO2 negative electrode.

Description

Technical Field

[0001] The present application relates to a two-dimensional SiO2-based composite material and its preparation method and application, belonging to the field of lithium-ion battery negative electrode materials. Background Art

[0002] Two-dimensional nanomaterials have attracted a lot of attention in basic research and technological applications because of their physical and chemical properties that are different from those of bulk materials, zero-dimensional materials and three-dimensional materials. In the past decade, more and more two-dimensional materials, including graphene, transition metal dihydrides, transition metal oxides and MXene, have been widely used in the fields of photocatalysis, electrocatalysis, energy storage and conversion, especially in the next generation of rechargeable lithium-ion batteries (LIBs). Among the two-dimensional anode materials, two-dimensional SiO2 has a high theoretical lithium storage capacity, fast Li + The diffusion rate and low discharge potential of SiO2 anodes are considered to be the most suitable electrode materials for next-generation LIBs. However, the practical application of SiO2 anodes is still limited by the mechanical degradation of the electrode structure caused by low conductivity, poor volume expansion and contraction, and the corresponding electrode is prone to fracture and pulverization. Summary of the Invention

[0003] This application is achieved by combining low interface impedance and fast Li + The two-dimensional composite material is assembled by electrostatic action on the two-dimensional SiO2 nanosheets with low diffusion rate, which improves the electronic conductivity of the two-dimensional SiO2 and inhibits its volume expansion during charging and discharging, thereby effectively improving the electrochemical cycle stability of the SiO2 negative electrode.

[0004] According to one aspect of the present application, there is provided a two-dimensional SiO2-based composite material, comprising SiO2 nanosheets and a two-dimensional composite material;

[0005] The two-dimensional composite material is coated on the surface of the SiO2 nanosheet through electrostatic action.

[0006] Optionally, the two-dimensional composite material is selected from at least one of molybdenum disulfide, graphene, and MXene.

[0007] According to another aspect of the present application, a method for preparing a two-dimensional SiO2-based composite material is provided, comprising the following steps:

[0008] The two-dimensional SiO2 nanosheet dispersion liquid is mixed with the two-dimensional composite material dispersion liquid, subjected to electrostatic self-assembly, and dried to obtain the two-dimensional SiO2-based composite material.

[0009] Optionally, the mass ratio of the two-dimensional SiO2 nanosheet dispersion to the two-dimensional composite material dispersion is 1:0.25~1.0, and the two-dimensional SiO2 nanosheet dispersion and the two-dimensional composite material dispersion are measured by the mass of the two-dimensional SiO2 nanosheets and the two-dimensional composite material, respectively.

[0010] Optionally, the mass ratio of the two-dimensional SiO2 nanosheet dispersion to the two-dimensional composite material dispersion is any value among 1:0.25, 1:0.5, 1:0.75, 1:1, or a range between two values.

[0011] Optionally, the two-dimensional composite material of the two-dimensional composite material dispersion is selected from at least one of molybdenum disulfide, graphene, and MXene.

[0012] Optionally, the concentration of the two-dimensional SiO2 nanosheet dispersion is 1 to 5 mg / mL.

[0013] Optionally, the concentration of the two-dimensional SiO2 nanosheet dispersion is any value among 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, or a range between two values.

[0014] Optionally, the concentration of the two-dimensional composite material dispersion is 0.5 to 2.5 mg / mL.

[0015] Optionally, the concentration of the two-dimensional composite material dispersion is any value of 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, or a range between two values.

[0016] In the present application, the solvents of the two-dimensional SiO2 nanosheet dispersion and the two-dimensional composite material dispersion are both selected from ethanol or water.

[0017] Optionally, the method for preparing the two-dimensional SiO2 nanosheets comprises:

[0018] a) preparing an aqueous solution containing template crystals, ethanol, and ammonia water, denoted as solution A;

[0019] b) preparing a solution containing a silicon source precursor and ethanol, denoted as solution B;

[0020] c) Solution A is mixed with solution B, evaporated, and calcined to obtain two-dimensional SiO2 nanosheets.

[0021] This application uses a template method to synthesize low interface impedance and fast Li +The two-dimensional SiO2 nanosheet with a diffusion rate is used for electrostatic self-assembly with a two-dimensional composite material, improves the electronic conductivity of the two-dimensional SiO2 and inhibits the volume expansion in the charge and discharge process, thereby effectively improving the electrochemical cycle stability of the SiO2 negative electrode. And the step-by-step preparation method can make the template crystal hydrolyze and then combine with the silicon source precursor, so that the silicon source precursor grows on the surface of the template crystal; on the other hand, the material content of each step can be accurately controlled to prepare a low interface impedance and fast Li + The two-dimensional SiO2 nanosheet with a diffusion rate.

[0022] Optionally, in step a), the template crystal is selected from at least one of sodium chloride, potassium chloride, sodium bromide and potassium bromide.

[0023] Optionally, the molar ratio of the template crystal, ethanol, ammonia and water in the solution A is 1:2-25:0.1-0.2:10-16.

[0024] Optionally, in step b), the silicon source precursor is selected from at least one of ethyl silicate, silane, silane oxide, diethyl silicate and azacyclohexane trimethylsilane.

[0025] Optionally, the molar ratio of the silane precursor and ethanol in the solution B is 1:250-350.

[0026] Optionally, in step c), the volume ratio of the solution A to the solution B is 1:0.5-1.5.

[0027] Optionally, the evaporation temperature is 50-70℃.

[0028] Optionally, the calcination condition is to increase the temperature to 400-600℃ at a temperature increasing rate of 1-5℃, and to keep the temperature for 1-5h.

[0029] Optionally, the electrostatic self-assembly time is 5-10h.

[0030] According to another aspect of the present application, the two-dimensional SiO2-based composite material or the two-dimensional SiO2-based composite material obtained by the above preparation method is applied to a rechargeable lithium ion battery negative electrode material.

[0031] The beneficial effects that can be produced by the present application include:

[0032] 1) The two-dimensional SiO2-based composite material provided by the present application is combined with a two-dimensional material through electrostatic self-assembly, improves the electronic conductivity of the two-dimensional SiO2 and inhibits the volume expansion in the charge and discharge process, thereby effectively improving the electrochemical cycle stability of the SiO2 negative electrode.

[0033] 2) The preparation method provided in this application uses a template method to synthesize low interface impedance and fast Li on the crystal surface + Based on the two-dimensional SiO2 nanosheets with high diffusion rate, they are composited with two-dimensional composite materials through electrostatic self-assembly to improve the mechanical stability of the electrode and inhibit the volume expansion of active particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a transmission electron microscopy image of the two-dimensional SiO2 / MXene composite material prepared in Example 1 of the present application;

[0035] Figure 2 This is a transmission electron microscopy image of the two-dimensional SiO2 nanosheet prepared in Comparative Example 1 of this application;

[0036] Figure 3 This is a diagram of the cycling performance of the samples prepared in Comparative Example 1 and Example 1 of the present application in lithium-ion batteries. DETAILED DESCRIPTION

[0037] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0038] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0039] Example 1

[0040] (1) Synthesis of two-dimensional SiO2-based composite materials:

[0041] 1) Sodium chloride: anhydrous ethanol: aqueous ammonia: deionized water were added in a molar ratio of 1:3:0.12:13, and mixed well to form solution A;

[0042] 2) Pipette ethyl silicate into anhydrous ethanol at a molar ratio of ethyl silicate to anhydrous ethanol = 1:310 to form solution B;

[0043] 3) Mixing the two solutions in a volume ratio of solution A to solution B = 1:0.83 to form a mixed solution C;

[0044] 4) Evaporation of mixed solution C at 60°C to obtain white crystals;

[0045] 5) Place the white crystals in a muffle furnace, heat to 500°C at 1°C / min, hold for 2 h, and cool naturally to obtain mixed sample D. Finally, wash with deionized water three times to obtain two-dimensional SiO2 nanosheets;

[0046] 6) Prepare a two-dimensional SiO2 nanosheet dispersion at a concentration of 4 mg / mL;

[0047] 7) Prepare a MXene dispersion at a concentration of 1 mg / mL;

[0048] 8) forming a two-dimensional SiO2 / MXene composite material mixed solution at room temperature according to a mass ratio of two-dimensional SiO2 nanosheets to MXene = 1:0.42;

[0049] 9) The two-dimensional SiO2 / MXene composite material obtained after vacuum filtration was placed in a vacuum oven at 80°C to obtain a two-dimensional SiO2 / MXene composite material as a negative electrode active material, such as Figure 1 As shown. Figure 1 It can be seen that the black shadow in the upper half of the figure is the two-dimensional SiO2 / MXene composite material, and the flakes with irregular edges in the lower right area are MXene.

[0050] Comparative Example 1

[0051] 1) Sodium chloride: anhydrous ethanol: aqueous ammonia: deionized water were added in a molar ratio of 1:3:0.12:13, and mixed well to form solution A;

[0052] 2) Pipette ethyl silicate into anhydrous ethanol at a molar ratio of ethyl silicate to anhydrous ethanol = 1:310 to form solution B;

[0053] 3) Mixing the two solutions in a volume ratio of solution A to solution B = 1:0.83 to form a mixed solution C;

[0054] 4) Evaporation of mixed solution C at 60°C to obtain white crystals;

[0055] 5) Place the white crystals in a muffle furnace, heat to 500°C at 1°C / min and keep warm for 2 h, then cool naturally to obtain mixed sample D, and finally wash with deionized water three times to obtain two-dimensional SiO2 nanosheets, such as Figure 2 As shown. Figure 2 It can be seen that the circular two-dimensional SiO2 nanosheets prepared in Comparative Example 1 have a size of 150 to 200 nm.

[0056] Example 3

[0057] The two-dimensional SiO2 / MXene composite material prepared in Example 1 and the two-dimensional SiO2 nanosheet prepared in Comparative Example 1 were used as the active material of the negative electrode of the lithium-ion battery, and the cycling performance of the half-cell was made with lithium metal sheet. Figure 3 As shown, the two-dimensional SiO2 nanosheets and two-dimensional SiO2 / MXene composites were -1 At the current density, the initial charge capacity is 164.3 mAh g -1 and 137.4mAh g -1 At the 300th cycle, the charge capacity of the two-dimensional SiO2 nanosheets dropped to 143.5 mAh g -1, while the two-dimensional SiO2 / MXene composite material increased to 357.0 mAh g -1 The addition of MXene increases the electronic conductivity of two-dimensional SiO2 nanosheets and weakens their Li + Volume expansion during insertion / extraction.

[0058] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A two-dimensional SiO2-based composite material, characterized in that: Including SiO2 nanosheets and MXene; The MXene is coated on the surface of the SiO2 nanosheets through electrostatic interaction; The method for preparing the two-dimensional SiO2-based composite material comprises the following steps: The two-dimensional SiO2 nanosheet dispersion is mixed with the MXene dispersion, subjected to electrostatic self-assembly, and dried to obtain a two-dimensional SiO2-based composite material; The preparation method of the two-dimensional SiO2 nanosheets comprises: a) preparing an aqueous solution containing template crystals, ethanol, and ammonia, denoted as solution A; b) preparing a solution containing a silicon source precursor and ethanol, denoted as solution B; c) mixing solution A with solution B, evaporating, and calcining to obtain two-dimensional SiO2 nanosheets; In step a), the template crystal is selected from at least one of sodium chloride, potassium chloride, sodium bromide, and potassium bromide.

2. A method for preparing the two-dimensional SiO2-based composite material according to claim 1, characterized in that: The following steps are involved: The two-dimensional SiO2 nanosheet dispersion is mixed with the MXene dispersion, subjected to electrostatic self-assembly, and dried to obtain a two-dimensional SiO2-based composite material; The preparation method of the two-dimensional SiO2 nanosheets comprises: a) preparing an aqueous solution containing template crystals, ethanol, and ammonia, denoted as solution A; b) preparing a solution containing a silicon source precursor and ethanol, denoted as solution B; c) mixing solution A with solution B, evaporating, and calcining to obtain two-dimensional SiO2 nanosheets; In step a), the template crystal is selected from at least one of sodium chloride, potassium chloride, sodium bromide, and potassium bromide.

3. The preparation method according to claim 2, characterized in that The mass ratio of the two-dimensional SiO2 nanosheet dispersion to the MXene dispersion is 1:0.25~1.0, and the two-dimensional SiO2 nanosheet dispersion and the MXene dispersion are calculated based on the mass of the two-dimensional SiO2 nanosheets and MXene, respectively.

4. The preparation method according to claim 2, characterized in that The concentration of the two-dimensional SiO2 nanosheet dispersion is 1-5 mg / mL; The concentration of the MXene dispersion is 0.5~2.5 mg / mL.

5. The preparation method according to claim 2, characterized in that In step a), the molar ratio of the template crystal, ethanol, aqueous ammonia and water in the solution A is 1:2-25:0.1-0.2:10-16.

6. The preparation method according to claim 2, characterized in that In step b), the silicon source precursor is selected from at least one of ethyl silicate, silane oxide, diethyl silicate, and azocyclohexanetrimethylsilane.

7. The preparation method according to claim 2, characterized in that In step b), the molar ratio of the silane precursor to ethanol in the solution B is 1:250-350.

8. The preparation method according to claim 2, characterized in that In step c), the volume ratio of solution A to solution B is 1:0.5-1.

5.

9. The preparation method according to claim 2, characterized in that In step c), the evaporation temperature is 50-70°C.

10. The preparation method according to claim 2, characterized in that In step c), the calcination conditions are: heating the temperature to 400-600° C. at a heating rate of 1-5° C. and keeping the temperature for 1-5 hours.

11. The preparation method according to claim 2, characterized in that The electrostatic self-assembly time is 5 to 10 hours.

12. Use of the two-dimensional SiO2-based composite material according to claim 1 or the two-dimensional SiO2-based composite material obtained by the preparation method according to any one of claims 2 to 11 in a negative electrode material for a rechargeable lithium-ion battery.

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