Composite material, method for producing the same, negative electrode material, method for producing the same, and battery

Abstract

The application relates to the technical field of batteries, in particular to a composite material and a preparation method thereof, a negative electrode material and a preparation method thereof, and a battery. x The SiO / Co3O4 composite material is composed of at least Co3O4 and a silicon-containing material, and the composite material has a nanosheet array structure, in which the length or width of a single nanosheet is 0.1-5 mu m, and the thickness of the single nanosheet is 5-20 nm. In the composite material, the nanosheet layer structure can effectively increase the contact area with electrolyte, is beneficial to the migration of electrons and lithium ions, and the gap between the sheet layers can reserve space for the volume expansion of the silicon-based material, and the structure is stable.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a composite material and its preparation method, a negative electrode material and its preparation method, and a battery. Background Technology

[0002] Lithium-ion batteries are widely used in electronics, electric vehicles, medical devices, and aerospace. Their performance is primarily limited by the electrode materials. Currently, graphite is the most commercially viable anode material; however, its relatively low specific capacity (theoretical specific capacity of 372 mAh / g) is increasingly failing to meet the demands for energy density, power density, and safety in lithium-ion batteries. Therefore, the development of novel anode materials is imperative. Among numerous potential candidates, silicon, with its ultra-high specific capacity (theoretical capacity of 4200 mAh / g) and low lithium intercalation potential, has become a strong contender for next-generation lithium-ion battery anode materials. However, the electrochemical performance of existing silicon-based anode materials is unsatisfactory. Therefore, developing an electrode material for lithium-ion batteries with high charge-discharge specific capacity and high cycle stability is crucial.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] One object of the present invention is to provide a SiO x / Co3O4 composite material is used to solve the technical problem of poor electrochemical performance of anode materials in existing technologies.

[0005] Another objective of this invention is to provide a negative electrode material with excellent conductivity, high charge / discharge specific capacity, and high cycle stability.

[0006] Another object of the present invention is to provide a SiO x Preparation method of / Co3O4 composite material.

[0007] Another object of the present invention is to provide a method for preparing a negative electrode material.

[0008] Another objective of this invention is to provide a lithium-ion battery with high charge-discharge specific capacity and cycle stability.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0010] A SiO x The / Co3O4 composite material is composed of at least Co3O4 and silicon-containing materials, and the composite material is in the form of a nanosheet array structure, wherein the length or width of a single nanosheet in the nanosheet array structure is 0.1 to 5 μm, and the thickness of a single nanosheet is 5 to 20 nm.

[0011] In one embodiment, the silicon-containing material is at least one of Si, SiO, and SiO2.

[0012] In one embodiment, the composite material contains silicon material with a mass fraction of 15.5% to 83.6% and Co3O4 with a mass fraction of 16.4% to 84.5%.

[0013] In one embodiment, the length-to-thickness ratio of the individual nanosheet is 1:(0.001-0.2), and the width-to-thickness ratio of the individual nanosheet is 1:(0.001-0.2).

[0014] A negative electrode material includes carbon fiber cloth and SiO2 as described above loaded on the carbon fiber cloth. x / Co3O4 composite material, wherein the loading of the composite material on the carbon fiber cloth is 0.5 to 13.3 mg / cm³. 2 .

[0015] In one embodiment, in the nanosheet array structure, individual nanosheets are perpendicular to the carbon fiber cloth.

[0016] In one embodiment, the diameter of a single carbon fiber in the carbon fiber cloth is 10–30 μm.

[0017] A SiO x The preparation method of / Co3O4 composite material includes the following steps:

[0018] The mixture of silicon source, cobalt source, surfactant and solvent is stirred to obtain the first mixed system;

[0019] The carbon fiber cloth is immersed in the first mixing system and then heat-treated to obtain the heat-treated carbon fiber cloth.

[0020] The heat-treated carbon fiber cloth is then washed, dried, and calcined to obtain SiO₂ loaded onto the carbon fiber cloth. x / Co3O4 composite material.

[0021] In one embodiment, the silicon source includes at least one of nano-silicon powder, potassium fluorosilicate, polysilazane, silicic acid, fluorosilicic acid, potassium silicate, copper fluorosilicate, ethyl silicate, butyl orthosilicate, tetraethyl orthosilicate, tungstic silicic acid, and sodium metasilicate.

[0022] In one embodiment, the cobalt source includes at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, cobalt phthalocyanine, and cobalt acetylacetonate.

[0023] In one embodiment, the surfactant includes at least one selected from glycerol, aniline, octadecylamine, ethylenediamine, ascorbic acid, potassium bromide, polyvinylpyrrolidone, 1-methylimidazole, and 2-methylimidazole.

[0024] In one embodiment, the solvent includes at least one selected from water, oleylamine, oleic acid, ethylene glycol, formic acid, and N,N-dimethylformamide.

[0025] In one embodiment, the mass ratio of the silicon source, cobalt source, and surfactant is 1:(0.03-79.6):(0.01-36.5).

[0026] In one embodiment, the ratio of the total mass of the silicon source, cobalt source, and surfactant to the amount of solvent is 1:(1.2 to 109.3 g / mL).

[0027] In one embodiment, the heat treatment includes employing a hydrothermal reaction.

[0028] In one embodiment, the carbon fiber cloth is further subjected to a pre-washing treatment before being immersed in the first mixing system; the pre-washing treatment uses detergents including alcohol solvents and water.

[0029] In one embodiment, the stirring process includes magnetic stirring; the stirring process lasts for 1 to 24 hours.

[0030] In one embodiment, the heat treatment temperature is 80–180°C, and the heat treatment time is 1–72 h.

[0031] In one embodiment, after the heat treatment, the heat-treated carbon fiber cloth is further cooled to room temperature.

[0032] In one embodiment, the detergent used in the washing process includes an alcohol solvent and water.

[0033] In one embodiment, the drying process includes vacuum drying; the drying temperature is 60–100°C, and the drying time is 1–24 hours.

[0034] In one embodiment, the calcination temperature is 200–800°C, and the calcination time is 1–24 h.

[0035] In one embodiment, the calcination treatment is carried out under nitrogen or inert gas conditions.

[0036] A method for preparing a negative electrode material, comprising SiO as described above. x The preparation method of / Co3O4 composite material yields SiO2 loaded on carbon fiber cloth. x / Co3O4 composite material, wherein SiO x The / Co3O4 composite material forms a negative electrode material with the carbon fiber cloth.

[0037] A lithium-ion battery comprising SiO as described above. x / Co3O4 composite material or SiO prepared by the method described above x / Co3O4 composite material;

[0038] Or it may include the negative electrode material as described above or the negative electrode material prepared by the method described above.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) In the composite material of the present invention, the nanosheet structure can effectively increase the contact area with the electrolyte, which is beneficial to the migration of electrons and lithium ions, and the gaps between the sheets can reserve space for the volume expansion of silicon-based materials, thus maintaining structural stability.

[0041] (2) The negative electrode material of the present invention has excellent conductivity and high charge-discharge specific capacity and cycle stability.

[0042] (3) The preparation methods of the composite material and negative electrode material of the present invention are simple, easy to implement and highly repeatable.

[0043] (4) The lithium-ion battery of the present invention has high charge-discharge specific capacity and excellent cycle stability. Attached Figure Description

[0044] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.

[0045] Figure 1 This is a scanning electron microscope (SEM) image of the negative electrode material in Embodiment 1 of the present invention, magnified 6500 times.

[0046] Figure 2 This is a SEM image of the negative electrode material in Embodiment 1 of the present invention, magnified 17,000 times.

[0047] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the negative electrode material in Embodiment 1 of the present invention.

[0048] Figure 4 The image shows the Fourier Transform Infrared (FTIR) spectrum of the negative electrode material in Example 1 of this invention.

[0049] Figure 5 The image shows the Raman spectrum of the negative electrode material in Example 1 of this invention.

[0050] Figure 6 The first charge-discharge curve of the battery prepared with the negative electrode material in Example 1 of this invention at 0.1C. Detailed Implementation

[0051] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0052] According to one aspect of the present invention, the present invention relates to a SiO x The / Co3O4 composite material is composed of at least Co3O4 and silicon-containing materials, and the composite material is in the form of a nanosheet array structure, wherein the length or width of a single nanosheet in the nanosheet array structure is 0.1 to 5 μm, and the thickness of a single nanosheet is 5 to 20 nm.

[0053] In one embodiment, in the nanosheet array structure, the length of a single nanosheet is 0.1–5 μm, the width of a single nanosheet is 0.1–5 μm, and the thickness of a single nanosheet is 5–20 nm. In another embodiment, the length of a single nanosheet is 0.1 μm, 0.5 μm, 1 μm, 1.2 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 4.5 μm, or 5 μm. In yet another embodiment, the width of a single nanosheet is 0.1 μm, 0.5 μm, 1 μm, 1.2 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 4.5 μm, or 5 μm. In one embodiment, the thickness of a single nanosheet is 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, or 20nm, etc.

[0054] In the composite material of the present invention, the ultrathin nanosheet array structure can effectively increase the contact area with the electrolyte, which is beneficial to the migration of electrons and lithium ions, and the gaps between the sheets can reserve space for the volume expansion of silicon-based materials, thus maintaining structural stability.

[0055] In one embodiment, SiO x In the / Co3O4 composite material, the silicon-containing material is SiO xAnd x can take at least one value from 0, 1, and 2, i.e., SiO x It is at least one of Si, SiO and SiO2.

[0056] In one embodiment, the silicon-containing material in the composite material has a mass fraction of 15.5% to 83.6%, and the Co3O4 has a mass fraction of 16.4% to 84.5%. In another embodiment, the mass fraction of the silicon-containing material includes, but is not limited to, 15.5%, 20%, 22%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 83.6%. The mass fraction of Co3O4 includes, but is not limited to, 16.4%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, or 84.5%. The ratio of silicon-containing material to Co3O4 in this invention, within a suitable range, can further synergistically enhance the electrochemical performance of the composite material.

[0057] In one embodiment, the length-to-thickness ratio of the individual nanosheet is 1:(0.001–0.2), for example 1:0.001, 1:0.002, 1:0.003, 1:0.005, 1:0.008, 1:0.009, 1:0.01, 1:0.02, 1:0.03, 1:0.05, 1:0.08, 1:0.1, 1:0.12, 1:0.13, 1:0.15, 1:0.18, or 1: The width-to-thickness ratio of the individual nanosheets is 1:(0.001~0.2), for example, 1:0.001, 1:0.002, 1:0.003, 1:0.005, 1:0.008, 1:0.009, 1:0.01, 1:0.02, 1:0.03, 1:0.05, 1:0.08, 1:0.1, 1:0.12, 1:0.13, 1:0.15, 1:0.18, or 1:0.2, etc. Within a suitable range, the thinner the individual nanosheets of this invention, the more beneficial it is for electrolyte wetting, and the better it is for improving the electrochemical performance of the battery.

[0058] According to another aspect of the invention, the invention also relates to a negative electrode material comprising carbon fiber cloth and SiO2 as described above loaded on said carbon fiber cloth. x / Co3O4 composite material, wherein the loading of the composite material on the carbon fiber cloth is 0.5 to 13.3 mg / cm³. 2 .

[0059] The negative electrode material of this invention exhibits high conductivity, excellent charge-discharge specific capacity, and cycle stability. The carbon fiber cloth serves several purposes: providing a suitable substrate for the growth of ultrathin nanosheet arrays; improving the conductivity of the composite material; and acting as a current collector, allowing for direct cutting to create the negative electrode sheet, simplifying the process.

[0060] In one embodiment, the loading of the composite material on the carbon fiber cloth includes, but is not limited to, 0.5 mg / cm³. 2 0.8 mg / cm 2 1mg / cm 2 2mg / cm 2 3mg / cm 2 4mg / cm 2 5mg / cm 2 6mg / cm 2 7mg / cm 2 8mg / cm 2 9mg / cm 2 10mg / cm 2 11mg / cm 2 12mg / cm 2 13mg / cm 2 13.3 mg / cm 2 In this invention, the loading of the negative electrode material on the carbon fiber cloth within the aforementioned suitable range can enable the negative electrode material to possess superior electrochemical performance. If the loading is too high, the silicon-based negative electrode material nanosheets will stack in multiple layers, which may easily lead to detachment and affect the stability of the structure; if the loading is too low, that is, the silicon-based negative electrode material has too little active material, it will affect the electrochemical performance; wherein the loading can be controlled by the precursor concentration, hydrothermal reaction temperature, time, carbon cloth size, etc.

[0061] In one embodiment, in the nanosheet array structure, individual nanosheets are perpendicular to the carbon fiber cloth.

[0062] In one embodiment, the diameter of a single carbon fiber in the carbon fiber cloth is 10 to 30 μm, such as 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 28 μm or 30 μm.

[0063] According to another aspect of the present invention, the present invention relates to a SiO x The preparation method of / Co3O4 composite material includes the following steps:

[0064] The mixture of silicon source, cobalt source, surfactant and solvent is stirred to obtain the first mixed system;

[0065] The carbon fiber cloth is immersed in the first mixing system and then heat-treated to obtain the heat-treated carbon fiber cloth.

[0066] The heat-treated carbon fiber cloth is then washed, dried, and calcined to obtain SiO₂ loaded onto the carbon fiber cloth. x / Co3O4 composite material.

[0067] This invention utilizes carbon fiber cloth as a substrate to grow a composite material with an ultrathin nanosheet array structure on the carbon fiber through a hydrothermal reaction. This ultrathin nanosheet structure can effectively increase the contact area with the electrolyte, which is beneficial to the migration of electrons and lithium ions. Furthermore, the gaps between the sheets can reserve space for the volume expansion of silicon-based materials, thus maintaining structural stability.

[0068] In one embodiment, the silicon source includes at least one of nano-silicon powder, potassium fluorosilicate, polysilazane, silicic acid, fluorosilicic acid, potassium silicate, copper fluorosilicate, ethyl silicate, butyl orthosilicate, tetraethyl orthosilicate, tungstic silicic acid, and sodium metasilicate.

[0069] In one embodiment, the cobalt source includes at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, cobalt phthalocyanine, and cobalt acetylacetonate.

[0070] In one embodiment, the surfactant includes at least one selected from glycerol, aniline, octadecylamine, ethylenediamine, ascorbic acid, potassium bromide, polyvinylpyrrolidone, 1-methylimidazole, and 2-methylimidazole.

[0071] In one embodiment, the solvent includes at least one selected from water, oleylamine, oleic acid, ethylene glycol, formic acid, and N,N-dimethylformamide.

[0072] In one embodiment, the mass ratio of the silicon source, cobalt source, and surfactant is 1:(0.03~79.6):(0.01~36.5), for example, 1:0.03:0.01, 1:0.05:0.02, 1:0.1:0.5, 1:5:2, 1:10:4, 1:20:5, 1:50:10, 1:79.6:36.5, etc.

[0073] In one embodiment, the ratio of the total mass of the silicon source, cobalt source, and surfactant to the amount of solvent is 1:(1.2 to 109.3), for example, 1:1.2, 1:5, 1:10, 1:20, 1:50, 1:80, 1:109.3, etc.

[0074] In one embodiment, the heat treatment includes employing a hydrothermal reaction.

[0075] In one embodiment, the carbon fiber cloth is further subjected to a pre-washing treatment before being immersed in the first mixing system; the detergent used in the pre-washing treatment includes an alcohol solvent and water. The alcohol solvent includes ethanol; the water is deionized water. In one embodiment, the cloth is washed 2 to 4 times with alcohol solvent and water respectively. By pre-washing the carbon fiber cloth, dust, impurities, etc. on its surface can be removed, which is beneficial for obtaining high-purity, stable nanosheet structure silicon-based anode materials in the later stage.

[0076] In one embodiment, the stirring process includes magnetic stirring; the stirring time is 1–24 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, 15 hours, 20 hours, 22 hours, 24 hours, etc. The present invention uses an appropriate stirring time to ensure uniform mixing of the raw materials, which is beneficial for the subsequent formation of ultrathin nanosheet structures in the composite material, thus ensuring the electrochemical performance of the composite material.

[0077] In one embodiment, the heat treatment temperature is 80–180°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C. In another embodiment, the heat treatment time is 1–72 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 10 hours, 15 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, or 70 hours. The present invention utilizes suitable heat treatment temperature and time, which is beneficial for generating ultrathin nanosheet structured anode materials, thereby improving the cycle stability of the battery.

[0078] In one embodiment, after the heat treatment, the heat-treated carbon fiber cloth is further cooled to room temperature.

[0079] In one embodiment, the washing process uses a detergent comprising an alcohol solvent and water. The alcohol solvent includes ethanol, isopropanol, etc., and the water includes deionized water. In one embodiment, the washing is performed 3 to 10 times sequentially using both the alcohol solvent and water.

[0080] In one embodiment, the drying process includes vacuum drying; the drying temperature is 60–100°C, and the drying time is 1–24 hours.

[0081] In one embodiment, the calcination temperature is 200–800°C, and the calcination time is 1–24 hours. In another embodiment, the calcination temperature includes, but is not limited to, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, or 800°C. In another embodiment, the calcination time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, or 24 hours. This invention, through appropriate calcination temperature and time, can alter the microstructure and physicochemical properties of the composite material, thereby resulting in a negative electrode material with excellent electrochemical performance. In one embodiment, the heating rate of the calcination treatment is 2–6°C / min.

[0082] In one embodiment, the calcination process is carried out under nitrogen or inert gas (e.g., argon, helium, etc.) conditions.

[0083] According to another aspect of the present invention, the present invention also relates to a method for preparing a negative electrode material, comprising SiO2 as described above. x The preparation method of / Co3O4 composite material yields SiO2 loaded on carbon fiber cloth. x / Co3O4 composite material, wherein SiO x The / Co3O4 composite material forms a negative electrode material with the carbon fiber cloth.

[0084] The method for preparing the negative electrode material of this invention is simple and easy to implement. The carbon fiber cloth is not only a substrate, but can also act as a current collector when assembling the button cell, which eliminates the need for material coating steps. There is no need to add binders and conductive agents in the process, which greatly reduces costs and process difficulty, and facilitates mass production.

[0085] According to another aspect of the invention, the invention also relates to a lithium-ion battery comprising SiO2 as described above. x / Co3O4 composite material or SiO prepared by the method described above x / Co3O4 composite material; or including the negative electrode material as described above or the negative electrode material prepared by the method described above.

[0086] The lithium-ion battery of the present invention has a high initial discharge capacity of 999.6 mAh / g or higher, a high initial efficiency of 81.9% or higher, and a high cycle capacity retention rate of 83.1% or higher after 50 cycles.

[0087] The following explanation, in conjunction with specific embodiments, comparative examples, and accompanying drawings, further clarifies the situation.

[0088] Example 1

[0089] A SiO xThe preparation method of / Co3O4 composite material includes the following steps:

[0090] (1) Measure 3 mL of ethyl silicate with a pipette, weigh 191 mg of cobalt nitrate and 200 mg of ascorbic acid with a balance, and add them to the PVC hydrothermal reactor liner containing 40 mL of ethylene glycol. Stir for 2 h to make the solution uniform. Cut the carbon fiber cloth that has been washed three times with deionized water and ethanol into 2×2 cm pieces, weigh them, and put them into the hydrothermal reactor. Then tighten the outer shell of the hydrothermal reactor and place it in a forced-air drying oven for hydrothermal reaction. The hydrothermal temperature is 180℃ and the reaction time is 6 h. After the reaction is completed, let it cool naturally to room temperature. Take out the carbon fiber cloth and rinse it several times with deionized water and ethanol. Arrange the washed carbon fiber in an oven and dry it at 80℃ for 6 h.

[0091] (2) The dried carbon fibers from (1) are arranged in a tube furnace, protected by N2, and calcined at a high temperature of 500℃, with a heating rate of 5℃ / min and a calcination time of 2h. The product is SiO2 loaded on the carbon fiber cloth. x / Co3O4 composite material, and weigh the carbon fiber cloth again. The difference between the mass of the carbon fiber cloth and the mass before the reaction is the SiO content. x The quality of / Co3O4 composite materials.

[0092] In addition, SiO2 loaded on carbon fiber cloth x The combination of Co3O4 composite material and carbon fiber cloth substrate can be used directly as a negative electrode material.

[0093] Example 2

[0094] A SiO x The preparation method of / Co3O4 composite material includes the following steps:

[0095] (1) Weigh 250mg of nano-silicon powder, 165mg of cobalt sulfate and 200mg of polyvinylpyrrolidone (PVP, average molecular weight 40000) using a balance and add them to the inner lining of a polytetrafluoroethylene hydrothermal reactor containing 40mL of deionized water. Stir for 2 hours to form a uniform emulsion. Cut the carbon fiber cloth, which has been washed three times with deionized water and ethanol, into 2×2cm pieces. Weigh the cloth and place it in the hydrothermal reactor. Then tighten the outer shell of the hydrothermal reactor and place it in a forced-air drying oven for hydrothermal reaction. The hydrothermal temperature is 170℃ and the reaction time is 12 hours. After the reaction is completed, allow it to cool naturally to room temperature. Take out the carbon fiber cloth and rinse it several times with deionized water and ethanol. Arrange the washed carbon fiber in an oven and dry it at 70℃ for 8 hours.

[0096] (2) The dried carbon fibers from (1) are arranged in a tube furnace, protected by N2, and calcined at a high temperature of 390℃, with a heating rate of 5℃ / min and a calcination time of 8h. The product is SiO2. x / Co3O4 composite material, and weigh the carbon fiber cloth again. The difference between the mass of the carbon fiber cloth and the mass before the reaction is the SiO content. x The quality of / Co3O4 composite materials.

[0097] In addition, SiO2 loaded on carbon fiber cloth x The combination of Co3O4 composite material and carbon fiber cloth substrate can be used directly as a negative electrode material.

[0098] Example 3

[0099] A SiO x The preparation method of / Co3O4 composite material includes the following steps:

[0100] (1) Weigh 310mg of silicic acid, 171mg of cobalt chloride and 190mg of 1-methylimidazole using a balance and add them to the inner lining of a polytetrafluoroethylene hydrothermal reactor containing 40mL of oleylamine. Stir for 2 hours to form a uniform emulsion. Cut the carbon fiber cloth, which has been washed three times with deionized water and ethanol, into 2×2cm pieces. Weigh the cloth and place it in the hydrothermal reactor. Then tighten the outer shell of the hydrothermal reactor and place it in a forced-air drying oven for hydrothermal reaction. The hydrothermal temperature is 150℃ and the reaction time is 20 hours. After the reaction is completed, allow it to cool naturally to room temperature. Take out the carbon fiber cloth and wash it several times with ethanol and isopropanol. Arrange the washed carbon fiber in an oven and dry it at 75℃ for 10 hours.

[0101] (2) The dried carbon fibers from (1) are arranged in a tube furnace, protected by N2, and calcined at a high temperature of 300℃, with a heating rate of 2℃ / min and a calcination time of 5h. The product is SiO2. x / Co3O4 composite material, and weigh the carbon fiber cloth again. The difference between the mass of the carbon fiber cloth and the mass before the reaction is the SiO content. x The quality of / Co3O4 composite materials.

[0102] In addition, SiO2 loaded on carbon fiber cloth x The combination of Co3O4 composite material and carbon fiber cloth substrate can be used directly as a negative electrode material.

[0103] Example 4

[0104] A SiO x The preparation method of / Co3O4 composite material includes the following steps:

[0105] (1) Weigh 300mg potassium silicate and 179mg cobalt acetylacetonate using a balance. Add 3mL glycerol to the PVC hydrothermal reactor containing 40mL oleic acid using a pipette. Stir for 1h to form a uniform emulsion. Cut the carbon fiber cloth, which has been washed three times with deionized water and ethanol, into 2×2cm pieces. Weigh the cloth and place it in the hydrothermal reactor. Then tighten the outer shell of the hydrothermal reactor and place it in a forced-air drying oven for hydrothermal reaction. The hydrothermal temperature is 180℃ and the reaction time is 10h. After the reaction is completed, allow it to cool naturally to room temperature. Take out the carbon fiber cloth and wash it several times with ethanol and isopropanol. Arrange the washed carbon fiber in an oven and dry it at 85℃ for 8h.

[0106] (2) The dried carbon fibers from (1) are arranged in a tube furnace, protected by N2, and calcined at a high temperature of 550℃, with a heating rate of 5℃ / min and a calcination time of 6h. The product is SiO2. x / Co3O4 composite material, and weigh the carbon fiber cloth again. The difference between the mass of the carbon fiber cloth and the mass before the reaction is the SiO content. x The quality of / Co3O4 composite materials.

[0107] In addition, SiO2 loaded on carbon fiber cloth x The combination of Co3O4 composite material and carbon fiber cloth substrate can be used directly as a negative electrode material.

[0108] Example 5

[0109] A SiO x The preparation method of / Co3O4 composite material includes the following steps:

[0110] (1) Weigh 260mg sodium metasilicate and 186mg cobalt phthalocyanine using a balance. Add 3mL of ethylenediamine to the PVC hydrothermal reactor liner containing 40mL of ethylene glycol using a pipette. Stir for 3 hours to form a uniform emulsion. Cut the carbon fiber cloth, which has been washed three times with deionized water and ethanol, into 2×2cm pieces. Weigh the cloth and place it in the hydrothermal reactor. Then tighten the outer shell of the hydrothermal reactor and place it in a forced-air drying oven for hydrothermal reaction. The hydrothermal temperature is 160℃ and the reaction time is 12 hours. After the reaction is completed, allow it to cool naturally to room temperature. Take out the carbon fiber cloth and wash it several times with ethanol and isopropanol. Arrange the washed carbon fiber in an oven and dry it at 80℃ for 6 hours.

[0111] (2) The dried carbon fibers from (1) are arranged in a tube furnace, protected by N2, and calcined at a high temperature of 480℃, with a heating rate of 3℃ / min and a calcination time of 12h. The product is SiO2. x / Co3O4 composite material, and weigh the carbon fiber cloth again. The difference between the mass of the carbon fiber cloth and the mass before the reaction is the SiO content.x The quality of / Co3O4 composite materials.

[0112] In addition, SiO2 loaded on carbon fiber cloth x The combination of Co3O4 composite material and carbon fiber cloth substrate can be used directly as a negative electrode material.

[0113] Comparative Example 1

[0114] This comparative example provides a commercial SiO / C anode material purchased from Krohde.

[0115] Comparative Example 2

[0116] This comparative example provides a Co3O4 powder reagent of analytical grade purchased from Maclean's.

[0117] Experimental Example

[0118] I. Characterization of Anode Materials

[0119] 1. Morphological and structural characterization

[0120] The negative electrode materials provided in Examples 1 to 5 were characterized by scanning electron microscopy (SEM). The SEM image of the negative electrode material in Example 1 is shown below. Figure 1 and Figure 2 As shown. By Figure 1 and Figure 2 It can be seen that the negative electrode material prepared in Example 1 exhibits an ultrathin nanosheet morphology. The length or width of a single nanosheet is 0.1-5 μm and the thickness is 5-20 nm. This nanosheet array structure can greatly alleviate the volume expansion of silicon-based materials during charging and discharging, and improve the cycle stability of the battery.

[0121] 2. X-ray diffraction (XRD) analysis

[0122] The negative electrode material provided in Example 1 was characterized by XRD analysis, such as... Figure 3 As shown, the negative electrode material of Example 1 contains Si, SiO and Co3O4, and its XRD diffraction patterns correspond to standard PDF cards #17-0901, #30-1127 and #43-1003, respectively, indicating that the present invention has successfully prepared a negative electrode material containing silicon-containing materials and Co3O4 composite materials.

[0123] 3. Infrared (FTIR) and Raman analysis

[0124] The negative electrode material provided in Example 1 was characterized by infrared analysis, such as... Figure 4 As shown, it can be seen that in the FTIR spectrum of Example 1, the values ​​between 500 and 750 cm⁻¹ are... -1There are two characteristic peaks within the range, corresponding to the vibrations of the Co-O group; 750–1000 cm⁻¹ -1 There are also two characteristic peaks within the range, corresponding to the vibrations of the Si-O groups. Figure 5 The image shown is the Raman spectrum of Example 1. It can be seen that at 194 cm⁻¹... -1 478cm -1 616cm -1 and 688cm -1 Characteristic peaks appeared at all locations, corresponding to the vibrations of the Co-O bonds; while at 518 cm⁻¹... -1 The characteristic peak at the location corresponds to the vibration of the Si-O bond. Both of the above characterization results prove that the product prepared in Example 1 is a negative electrode material containing silicon-containing materials and Co3O4 composite materials.

[0125] II. Electrochemical Performance Test Results of the Battery

[0126] The powder materials prepared in the examples and comparative examples were used to prepare coin cells. The specific steps are as follows:

[0127] The electrochemical performance of the product of this invention was evaluated by assembling CR2032-button half-cells. The electrode fabrication process of the examples is as follows: carbon fiber cloth with grown nanosheet arrays was punched and cut into 13mm diameter discs, which were directly used as electrodes; while the electrode preparation process of Comparative Examples 1 and 2 was as follows: the mass ratio of active material, acetylene black, CMC, and SBR was 80:10:4:6, where CMC was a 1% aqueous solution. The slurry was dispersed at 10,000 rpm for 0.5 h using a high-speed shear mixer, and then the uniformly stirred slurry was coated onto a 15μm thick copper foil. After natural air drying, the copper foil was placed in an 80℃ vacuum drying oven for 10 h, and the dried copper foil was compacted using a roller press; the electrode was punched and cut into 13mm diameter discs. Half-cells were assembled in a glove box protected by high-purity argon gas. The counter electrode was made of lithium foil, and the separator was a porous polypropylene membrane. The electrolyte consisted of a solvent, 1M LiPF6, and 5wt% fluoroethylene carbonate. The solvent was a mixture of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:1. Battery charge-discharge tests were conducted in a multi-channel cell, with the negative electrode material tested at a voltage range of 0.01V–1.5V (vs. Li). + / Li).

[0128] The electrochemical performance of the batteries prepared with the negative electrode materials of each embodiment and comparative example is shown in Table 1.

[0129] Table 1 Electrochemical performance test results

[0130]

[0131]

[0132] From Table 1 and Figure 6 It can be seen that the negative electrode materials of the various embodiments of the present invention have low resistivity and large specific surface area, among which the resistivity of Embodiment 1 is the lowest, reaching 2.6 × 10⁻⁶. -4 Ω·m, with Example 5 having the largest specific surface area at 13.2 m². 2 / g; After being assembled into a lithium-ion battery, the battery of Example 1 achieved a first discharge specific capacity of up to 1019.3 mAh / g under 0.1C conditions, with a first-discharge efficiency of 88.1%, far exceeding the first-discharge efficiencies of Comparative Examples 1 and 2 (63.2% for Comparative Example 1 and 50.9% for Comparative Example 2). Figure 6 As shown in Table 1, the cycle stability of the battery prepared by the negative electrode material of the present invention has been greatly improved. The battery prepared by the negative electrode material of Example 1 has a capacity retention rate of 90.2% after 50 cycles, while the battery prepared by Comparative Example 1 has a cycle capacity retention rate of only 79.6%, and the battery prepared by Comparative Example 2 has a cycle capacity retention rate of only 53.3%.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A SiO x The method for preparing the / Co3O4 composite material is characterized by, Includes the following steps: The mixture of silicon source, cobalt source, surfactant and solvent is stirred to obtain the first mixed system; The carbon fiber cloth is immersed in the first mixing system and then heat-treated to obtain the heat-treated carbon fiber cloth. The carbon fiber cloth after the heat treatment is subjected to washing treatment, drying treatment and calcination treatment to obtain SiO x / Co3O4 composite material; The SiO x The / Co3O4 composite material is composed of at least Co3O4 and a silicon-containing material, and the composite material has a nanosheet array structure. In the nanosheet array structure, the length or width of a single nanosheet is 2 to 5 μm, and the thickness of a single nanosheet is 5 to 20 nm. In the composite material, the mass fraction of the silicon-containing material is 15.5% to 83.6%, and the mass fraction of the Co3O4 is 16.4% to 84.5%. The silicon-containing material is at least one of Si and SiO. The length-to-thickness ratio of a single nanosheet is 1:(0.001 to 0.2), and the width-to-thickness ratio of a single nanosheet is 1:(0.001 to 0.2).

2. The SiO according to claim 1 x The method for preparing the / Co3O4 composite material is characterized by, It includes at least one of the following features (1) to (4): (1) The silicon source includes at least one of nano-silicon powder, potassium fluorosilicate, polysilazane, silicic acid, fluorosilicic acid, potassium silicate, copper fluorosilicate, ethyl silicate, butyl orthosilicate, tetraethyl silicate, tungstic silicic acid and sodium metasilicate; (2) The cobalt source includes at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, cobalt phthalocyanine, and cobalt acetylacetonate; (3) The surfactant includes at least one of glycerol, aniline, octadecylamine, ethylenediamine, ascorbic acid, potassium bromide, polyvinylpyrrolidone, 1-methylimidazole and 2-methylimidazole; (4) The solvent includes water, oleylamine, oleic acid, ethylene glycol, formic acid, and N,N At least one of dimethylformamide.

3. The SiO according to claim 1 x The method for preparing the / Co3O4 composite material is characterized by, It includes at least one of the following features (1) to (3): (1) The mass ratio of the silicon source, cobalt source and surfactant is 1:(0.03~79.6):(0.01~36.5); (2) The ratio of the total mass of the silicon source, cobalt source and surfactant to the amount of solvent used is 1:(1.2 ~109.3). (3) The heat treatment includes the use of hydrothermal reaction.

4. The SiO according to claim 1 x The method for preparing the / Co3O4 composite material is characterized by, It includes at least one of the following features (1) to (8): (1) The carbon fiber cloth is further subjected to a pre-washing treatment before being immersed in the first mixing system; the detergent used in the pre-washing treatment includes alcohol solvent and water; (2) The stirring process includes magnetic stirring; the stirring time is 1 to 24 hours. (3) The temperature of the heat treatment is 80 ~ 180 °C, and the time of the heat treatment is 1 ~ 72 h; (4) After the heat treatment, the heat-treated carbon fiber cloth is further cooled to room temperature; (5) The detergent used in the washing process includes alcohol solvent and water; (6) The drying process includes vacuum drying; the temperature of the drying process is 60 ~ 100 °C, and the drying time is 1 ~ 24 h; (7) The calcination temperature is 200 ~ 800 °C, and the calcination time is 1 ~ 24 h; (8) The calcination treatment is carried out under nitrogen or inert gas conditions.

5. A method for preparing a negative electrode material, characterized in that, Including SiO2 loaded on carbon fiber cloth prepared by the preparation method according to any one of claims 1 to 4. x / Co3O4 composite material, wherein SiO x The / Co3O4 composite material forms a negative electrode material with the carbon fiber cloth.

6. The method for preparing the negative electrode material according to claim 5, characterized in that, The loading of the composite material on the carbon fiber cloth is 0.5 ~ 13.3 mg / cm². 2 .

7. The method for preparing the negative electrode material according to claim 5, characterized in that, In the nanosheet array structure, each nanosheet is perpendicular to the carbon fiber cloth; and / or, in the carbon fiber cloth, the diameter of a single carbon fiber is 10 ~ 30 μm.

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