CN107346820A - A kind of three-dimensional porous carbon-wrapped silicon composite negative electrode material and preparation method thereof - Google Patents

Abstract

The invention provides a three-dimensional porous carbon-coated silicon composite anode material and a preparation method thereof. The composite cathode material consists of a carbon cloth substrate, a three-dimensional porous carbon layer growing on the carbon cloth substrate and a silicon nano material wrapped in the three-dimensional porous carbon layer. The preparation method of the composite negative electrode material comprises the following steps: coating a mixed solution of starch, sodium hydroxide and water on carbon cloth, drying, calcining, cooling to room temperature, soaking in a hydrochloric acid solution, washing, and drying to obtain the carbon cloth with the three-dimensional porous carbon layer; and mixing a silicon nano material with an ethylene glycol and/or propylene glycol solution, then carrying out hydrothermal reaction on the silicon nano material and the carbon cloth with the three-dimensional porous carbon layer, cooling to room temperature, washing and drying to obtain the three-dimensional porous carbon coated silicon composite negative electrode material. The composite negative electrode material provided by the invention is a high-conductivity and high-capacity negative electrode material, and the composite negative electrode material can reduce the influence of the volume change of a silicon-based material on the structure.

Description

A kind of three-dimensional porous carbon-wrapped silicon composite negative electrode material and preparation method thereof

technical field

The invention provides a three-dimensional porous carbon-wrapped silicon composite negative electrode material and a preparation method thereof, and a lithium ion battery containing the composite negative electrode material, belonging to the technical field of lithium ion batteries.

Background technique

Energy is the material basis for human survival and development. Currently, human beings are facing serious energy shortages. With the rapid development of the global economy, the continuous consumption of fossil energy, and the increasingly serious environmental pollution, it is becoming more and more important to study a high-efficiency, low-cost, environmentally friendly, and high-performance energy conversion and storage system.

Lithium-ion batteries are widely used in automobiles, electric power, railways, communications, national defense, consumer Electronic production and other fields, which has attracted extensive attention of scientific researchers.

At present, commercial lithium-ion batteries mainly use graphite-based negative electrode materials, but its theoretical specific capacity is only 372mAh/g, which cannot meet the demand for high energy density of lithium-ion batteries in the future. As a new type of lithium battery anode material, silicon has a lithium storage capacity of 4200mAh/g, nearly 10 times that of graphite. However, there are still some technical problems in using silicon as the negative electrode material at present. Due to the poor conductivity of silicon-based materials, there is a serious volume expansion in the process of deintercalating lithium, which causes the structural damage of the material and even falls off from the electrode. Therefore, the main technical difficulty in the application of silicon-based negative electrode materials in lithium-ion batteries is that the volume of most silicon-based materials changes greatly during the process of lithium intercalation and deintercalation, and the structural expansion and structural destruction of silicon-based materials eventually lead to a severe decline in capacity. .

Contents of the invention

In order to solve the above-mentioned technical problems, the object of the present invention is to provide a composite negative electrode material of three-dimensional porous carbon-wrapped silicon and a preparation method thereof. The composite negative electrode material is a silicon-carbon composite negative electrode material with high conductivity and high capacity, and the composite negative electrode material can reduce the influence of the volume change of the silicon-based material on the structure.

The object of the present invention is also to provide a lithium ion battery containing the composite negative electrode material of the above-mentioned three-dimensional porous carbon-wrapped silicon.

In order to achieve the above object, the present invention firstly provides a composite anode material of three-dimensional porous carbon wrapped silicon, which composite anode material is composed of a carbon cloth substrate, a three-dimensional porous carbon layer grown on the carbon cloth substrate, and wrapped in the said carbon cloth substrate. Composition of silicon nanomaterials in three-dimensional porous carbon layers.

In the composite anode material of the above-mentioned three-dimensional porous carbon-wrapped silicon, preferably, the electrical conductivity of the carbon cloth substrate is below 5 mΩ·cm ² . Carbon cloth is carbon fiber cloth, which is a fabric of carbon fiber and a conductive material with high toughness and high flexibility. In the present invention, the carbon cloth base can be selected from one or more combinations of polyacrylonitrile (PAN)-based carbon fiber cloth, viscose-based carbon fiber cloth, pitch-based carbon fiber cloth, etc., for the weaving method of the carbon cloth And the size is not particularly limited, and can be selected by those skilled in the art according to actual needs.

In the above-mentioned composite negative electrode material of silicon-wrapped three-dimensional porous carbon, preferably, the thickness of the three-dimensional porous carbon layer is 0.5-100 μm, and the surface area of the three-dimensional porous carbon in the three-dimensional porous carbon layer is 20-300 m ² /g, The pore volume is 10-200m ³ /g, and the average pore diameter is 2-200nm.

In the composite anode material of the above-mentioned three-dimensional porous carbon-wrapped silicon, preferably, the silicon nanomaterial includes silicon nanoparticles and/or silicon nanowires, the diameter of the silicon nanoparticles is 1-150 nm, and the diameter of the silicon nanowires is The diameter is 5-10nm, the length is 10-50nm, based on the total weight of the composite negative electrode material of the three-dimensional porous carbon wrapped silicon, wherein the content of silicon nanomaterials is 1-70%, more preferably, wherein the silicon nanomaterials The content is 40-60%.

In the composite anode material of the above-mentioned three-dimensional porous carbon-wrapped silicon, preferably, the three-dimensional porous carbon layer is grown on the carbon cloth substrate through the following steps: coating the mixed solution of starch, sodium hydroxide and water on the carbon cloth, and then dried at 50-120°C (drying time is preferably 3-24 hours), then calcined at 500-900°C under the protection of nitrogen and/or argon for 0.5-24 hours, and then cooled to room temperature, Then put into hydrochloric acid solution and soak for 5-48 hours, after washing (can be washed with deionized water), and drying (the drying temperature is preferably 80-120°C, and the time is preferably 6-48 hours), a three-dimensional porous carbon layer is obtained carbon cloth. Wherein, the hydrochloric acid solution may be a hydrochloric acid solution with a mass concentration of 5-35%. In addition, the above steps can be repeated to prepare three-dimensional porous carbon layers with different thicknesses.

In the preparation step of the above-mentioned carbon cloth having a three-dimensional porous carbon layer, preferably, the mixed solution of starch, sodium hydroxide and water is prepared by the following steps: the mass ratio is about 1:(1-100) :(1-10) (the mass ratio is preferably 1:(1-10):5) starch, sodium hydroxide, water (preferably deionized water) are mixed evenly, and then placed at 20-100°C for 2-48 Hours, after cooling to room temperature (the step of cooling to room temperature can be optionally carried out, depending on the temperature of the above-mentioned placement), the mixed solution of starch, sodium hydroxide and water is obtained.

In the above step of preparing the carbon cloth with a three-dimensional porous carbon layer, preferably, the amount of the mixture of starch, sodium hydroxide and water coated on the carbon cloth is 0.01-5 g/cm ² each time.

According to a specific embodiment of the present invention, preferably, the preparation step of the above-mentioned carbon cloth with a three-dimensional porous carbon layer further includes: before coating the mixed solution of starch, sodium hydroxide and water on the carbon cloth, first coating the carbon cloth Cleaning, the specific steps are: put the carbon cloth in ethanol solution water for cleaning (preferably ultrasonic cleaning) for 0.1-5 hours, and then put it into acetone solution for cleaning (preferably ultrasonic cleaning) for 0.1-5 hours. Wherein, the ethanol solution may be an ethanol solution with a mass concentration of 90-99.9%, and the acetone solution may be an acetone solution with a mass concentration of 90-99.9%.

In the composite negative electrode material of the above-mentioned three-dimensional porous carbon-wrapped silicon, preferably, the silicon nanomaterial is wrapped in the three-dimensional porous carbon layer through the following steps: a solution of the silicon nanomaterial and ethylene glycol and/or propylene glycol, etc. (Mass concentration can be 90-99.9%) mixed, then react with the carbon cloth with the three-dimensional porous carbon layer under 90-200 ℃ hydrothermal conditions for 2-48 hours, after cooling to room temperature, wash (can use deionized washing with water), drying (the drying temperature is preferably 60-80° C., and the drying time is preferably 6-48 hours), to obtain the composite negative electrode material of three-dimensional porous carbon-wrapped silicon. Wherein, the silicon nanomaterials used include silicon nanoparticles and/or silicon nanowires, the particle diameter of the silicon nanoparticles is preferably 1-150nm, the diameter of the silicon nanowires is preferably 5-10nm, and the length is preferably 10 nm. -50nm.

According to a specific embodiment of the present invention, preferably, the above-mentioned three-dimensional porous carbon-wrapped silicon composite negative electrode material provided by the present invention has a capacity of 500-2000mAh g ^-1 and a Coulombic efficiency of 95-99%.

In addition, the present invention also provides a method for preparing the composite negative electrode material of the above-mentioned three-dimensional porous carbon-wrapped silicon, which includes the following steps:

(1) Coat the mixture of starch, sodium hydroxide and water on the carbon cloth, then dry it at 50-120°C (the drying time is preferably 3-24 hours), and then dry it at 500-900°C, nitrogen and /or calcined under the protection of argon for 0.5-24 hours, then cooled to room temperature, then soaked in hydrochloric acid solution for 5-48 hours, washed (can be washed with deionized water), dried (the drying temperature is preferably 80-120 °C , the time is preferably 6-48 hours), obtain a carbon cloth with a three-dimensional porous carbon layer;

(2) Mix silicon nanomaterials with a solution of ethylene glycol and/or propylene glycol, etc. (mass concentration can be 90-99.9%), and then mix with the carbon cloth with a three-dimensional porous carbon layer under 90-200 ° C under hydrothermal conditions React for 2-48 hours, cool to room temperature, wash (can be washed with deionized water), and dry (the drying temperature is preferably 60-80°C, and the time is preferably 6-48 hours), to obtain the three-dimensional porous carbon package Silicon composite anode material.

In the above preparation method, preferably, step (1) can be repeated to prepare three-dimensional porous carbon layers with different thicknesses. In addition, the hydrochloric acid solution in step (1) can be a hydrochloric acid solution with a mass concentration of 5-35%.

In the above preparation method, preferably, the mixed solution of starch, sodium hydroxide and water is prepared through the following steps: the mass ratio is about 1: (1-100): (1-10) (the mass The ratio is preferably 1:(1-10):5) starch, sodium hydroxide, water (preferably deionized water) are mixed evenly, then placed at 20-100°C for 2-48 hours, after cooling to room temperature (the cooling The step to room temperature can be optionally carried out, depending on the above-mentioned standing temperature), to obtain the mixed solution of starch, sodium hydroxide and water.

In the above preparation method, preferably, the amount of the mixture of starch, sodium hydroxide and water coated on the carbon cloth each time is 0.01-5 g/cm ² .

According to a specific embodiment of the present invention, preferably, the above-mentioned preparation method also includes step (1)-1 before step (1): putting the carbon cloth in an ethanol solution for cleaning (preferably ultrasonic cleaning) for 0.1-5 hours, and then Put into acetone solution for cleaning (preferably ultrasonic cleaning) for 0.1-5 hours. That is, before coating the mixture of starch, sodium hydroxide and water on the carbon cloth, the carbon cloth is cleaned. Wherein, the ethanol solution may be an ethanol solution with a mass concentration of 90-99.9%, and the acetone solution may be an acetone solution with a mass concentration of 90-99.9%.

In the above preparation method, preferably, in step (2), the silicon nanomaterials used include silicon nanoparticles and/or silicon nanowires, the particle diameter of the silicon nanoparticles is preferably 1-150nm, and the silicon nanoparticles The nanowires preferably have a diameter of 5-10 nm and a length of 10-50 nm.

The invention provides a composite negative electrode material in which three-dimensional porous carbon-wrapped silicon is synthesized on carbon cloth and a preparation method thereof. The preparation method provided by the present invention grows three-dimensional porous carbon on carbon cloth, and then wraps silicon nanomaterials to prepare a composite negative electrode material; specifically, it includes: preparing a three-dimensional porous carbon layer on a carbon cloth substrate by a calcining method, and then using hydrothermal The reaction wraps silicon nanomaterials in the three-dimensional porous carbon layer on the carbon cloth substrate, and finally prepares a composite negative electrode material. In the composite negative electrode material of the present invention, the existence of three-dimensional porous carbon provides effective space and efficient electron transport path for the expansion of silicon-based materials, improves the capacity of the electrode material itself, and also plays an important role in improving cycle performance.

In addition, the present invention also provides a lithium ion battery containing the composite negative electrode material of the above-mentioned three-dimensional porous carbon-wrapped silicon.

According to a specific embodiment of the present invention, preferably, the above-mentioned lithium ion battery includes: a working electrode, a counter electrode or a reference electrode, an electrolyte and a diaphragm between the working electrode and the counter electrode or a reference electrode, wherein the working The electrode contains the composite negative electrode material of the three-dimensional porous carbon-wrapped silicon.

According to a specific embodiment of the present invention, preferably, the above-mentioned lithium ion battery further includes: a battery case for encapsulating the working electrode, the counter electrode or the reference electrode, the electrolyte and the diaphragm.

In the above lithium ion battery, preferably, the working electrode only includes the composite negative electrode material of the three-dimensional porous carbon-wrapped silicon. That is to say, the composite anode material of the three-dimensional porous carbon-wrapped silicon can be cut into a desired shape (vacuum drying can be carried out before cutting, the temperature can be 50-150 ° C, and the time can be 2-48 hours), directly as the working electrode. Alternatively, the working electrode may include a current collector and a negative electrode material layer formed on the surface of the current collector, and the negative electrode material layer includes the composite negative electrode material containing the three-dimensional porous carbon-wrapped silicon. More preferably, the negative electrode material layer further includes a conductive agent and/or a binder. The mass ratio of the three-dimensional porous carbon-wrapped silicon composite negative electrode material, the conductive agent and the binder may be (50-90):(0.1-40):(0-20). In addition, the negative electrode material layer can be formed on the surface of the current collector through the following steps: uniformly mixing the three-dimensional porous carbon-wrapped silicon composite negative electrode material, a conductive agent and/or a binder in an organic solvent, and then uniformly coated on the surface of the current collector, and after drying, the negative electrode material layer is formed (the above organic solvent will be completely volatilized during the drying process, and the final negative electrode material layer does not contain the organic solvent). The organic solvent may include one or a combination of N-methylpyrrolidone, dimethylsulfoxide, sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide and caprolactam . It can then optionally be trimmed to obtain a working electrode of the desired size.

In the above lithium ion battery, preferably, the current collector in the working electrode includes one of aluminum, copper, iron, tin, zinc, nickel, titanium and manganese or an alloy formed of several of these materials.

In the above lithium ion battery, preferably, the conductive agent includes one or a combination of conductive carbon black, conductive carbon spheres, conductive graphite, carbon nanotubes, conductive carbon fibers, graphene and reduced graphene oxide, etc. .

In the above lithium ion battery, preferably, the binder includes polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose, styrene-butadiene rubber (SBR) and polyolefin binders, etc. one or a combination of several.

In the above lithium ion battery, preferably, the counter electrode or reference electrode includes metallic lithium or a lithium-containing alloy or the like. More preferably, the lithium-containing alloy includes lithium aluminum alloy, and the content of lithium therein may be 20-50wt.%.

In the above lithium ion battery, preferably, the separator includes an insulating polymer film and/or an inorganic film. The diaphragm may include a film formed by one or a combination of polyethylene, polypropylene, polytetrafluoroethylene, cellulose, etc., and may also include glass fiber paper and/or a ceramic diaphragm. The separator can be a single-layer structure or a multi-layer structure. Also, the membrane may be a porous membrane.

In the above lithium ion battery, preferably, the electrolyte may include a solution formed of a lithium salt electrolyte and an organic solvent. Wherein, the lithium salt electrolyte includes LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₂ , LiP(C ₆ H ₄ O ₂ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiB(C ₂ One or a combination of O ₄ ) ₂ and LiN(CF ₃ SO ₂ ) ₂ etc. Described organic solvent comprises ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), butylene carbonate, methyl carbonate Butyl esters and their isomers, methyl acetate, methyl propionate, g-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,3-dioxolane, 4- One or a combination of methyl-1,3-dioxolane, propiolic acid, tetrahydrofuran, 2-methyltetrahydrofuran, and dimethyl sulfoxide. More preferably, the concentration of the lithium salt electrolyte in the electrolyte is 0.1-5 mol/L.

In the above lithium ion battery, the battery case can be a battery case commonly used in the field, such as a battery case made of SUS.

The present invention has no special limitation on the shape of the above-mentioned lithium-ion battery, which may be coin-shaped (ie, button-shaped), flat-plate-shaped, cylindrical-shaped, and angle-shaped.

In summary, the present invention provides a high-conductivity, high-capacity three-dimensional porous carbon-wrapped silicon composite anode material, and the composite anode material can reduce the impact of volume changes of silicon-based materials on the structure. Moreover, the preparation method of the composite negative electrode material provided by the invention has the advantages of simple process flow, environmental friendliness and pollution-free, high degree of industrialization, and the like. The three-dimensional porous carbon-wrapped silicon composite negative electrode material and the preparation method provided by the invention can promote the development of lithium-ion batteries, can be widely used in the field of energy storage, and are expected to promote the development of electric vehicles.

Description of drawings

Fig. 1 is the SEM photo of the carbon cloth with three-dimensional porous carbon layer prepared by embodiment 1;

Fig. 2 is the SEM photo of the composite negative electrode material of the three-dimensional porous carbon wrapped silicon prepared in embodiment 1;

3 is the cycle charge/discharge capacity retention curve of the lithium ion battery prepared in Example 1.

detailed description

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

Example 1

This embodiment provides a composite negative electrode material of three-dimensional porous carbon-wrapped silicon nanoparticles, which is prepared by the following steps:

(1) Put a carbon fiber cloth with a size of 2cm×5cm and a conductivity of <5mΩ· ^cm2 into an ethanol solution (99.5% mass concentration) for ultrasonic cleaning for 4 hours, and then put it into an acetone solution (99.5% mass concentration) Ultrasonic cleaning for 4 hours to obtain the cleaned carbon cloth;

(2) Dissolve starch in ionized water, then add sodium hydroxide, the mass ratio of starch: sodium hydroxide: water is 1:2:5, stir evenly, then place in an oven at 80°C for 12 hours, and cool to After room temperature, a mixture of starch, sodium hydroxide and water was obtained;

(3) The mixed solution of starch, sodium hydroxide and water obtained in step (2) is coated on the carbon cloth after cleaning obtained in step (1), and the amount of the mixed solution of coated starch, sodium hydroxide and water 5-10g, then dried at 80°C for 5 hours, then calcined at 550°C under the protection of Ar gas for 10 hours, then cooled to room temperature, then soaked in hydrochloric acid solution (mass concentration: 37%) for 10 hours, and removed After washing with ionized water, dry at 80°C for 10 hours to obtain a carbon cloth with a three-dimensional porous carbon layer. Figure 1 is an SEM photo of the carbon cloth with a three-dimensional porous carbon layer, wherein the thickness of the three-dimensional porous carbon layer is 1-2 μm , the surface area of the three-dimensional porous carbon in the three-dimensional porous carbon layer is 20-80m ² /g, the pore volume is 10-50m ³ /g, and the pore diameter is 20-80nm;

(4) Mix silicon nanoparticles with a particle size of 10-20nm and ethylene glycol solution (mass concentration is 99.8%), and then put into hydrothermal reaction with the carbon cloth with three-dimensional porous carbon layer obtained in step (3) In the kettle, react under hydrothermal conditions at 150°C for 8 hours, after cooling to room temperature, take out the product from the hydrothermal reaction kettle, wash with deionized water, and then dry at 60°C for 24 hours to obtain the three-dimensional porous carbon package Silicon composite anode material.

Fig. 2 is the SEM picture of the composite negative electrode material of this three-dimensional porous carbon wrapping silicon, and this composite negative electrode material is made of carbon cloth substrate, the three-dimensional porous carbon layer grown on the described carbon cloth substrate, and wrapping in the described three-dimensional porous carbon layer The composition of silicon nanoparticles, wherein the diameter of the silicon nanoparticles is 10-20nm, based on the total weight of the composite negative electrode material of the three-dimensional porous carbon-wrapped silicon, wherein the content of the silicon nanoparticles is 50-60%.

The CR2032 button battery was prepared by using the composite negative electrode material of three-dimensional porous carbon-wrapped silicon provided in this example, and the specific steps were as follows:

The three-dimensional porous carbon-wrapped silicon composite negative electrode material provided in this example was vacuum-dried in an oven at 50-150°C for 2-48 hours, and after vacuum drying, it was cut into discs with a diameter of 10 mm to prepare electrode sheets;

In a glove box filled with argon gas, use the above electrode sheet as the working electrode, microporous polypropylene as the diaphragm, and a 1mol/L solution prepared with lithium hexafluorophosphate and a mixed solvent of ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1 As the electrolyte, a metal lithium sheet was used as the counter electrode to assemble a CR2032 button battery.

Figure 3 is the cycle charge/discharge capacity retention curve of the lithium-ion battery. It can be seen from Figure 3 that the battery has a capacity of about 2000mAh g ^-1 , a Coulombic efficiency of about 98%, and high stability after 120 cycles (Generally speaking, the capacity loss in the first 1-3 cycles is negligible).

Example 2

This embodiment provides a composite anode material of three-dimensional porous carbon-wrapped silicon nanowires, which is prepared by the following steps:

(1) Put a carbon fiber cloth with a size of 2cm×5cm and a conductivity of <5mΩ· ^cm2 into an ethanol solution (99.5% mass concentration) for ultrasonic cleaning for 4 hours, and then put it into an acetone solution (99.5% mass concentration) Ultrasonic cleaning for 4 hours to obtain the cleaned carbon cloth;

(2) Dissolve starch in ionized water, then add sodium hydroxide, the mass ratio of starch: sodium hydroxide: water is 1:2:5, stir evenly, then place in an oven at 80°C for 12 hours, and cool to After room temperature, a mixture of starch, sodium hydroxide and water was obtained;

(3) The mixed solution of starch, sodium hydroxide and water obtained in step (2) is coated on the carbon cloth after cleaning obtained in step (1), and the amount of the mixed solution of coated starch, sodium hydroxide and water 5-10g, then dried at 80°C for 5 hours, then calcined at 650°C under the protection of Ar gas for 10 hours, then cooled to room temperature, then soaked in hydrochloric acid solution (mass concentration: 37%) for 10 hours. After washing with ionized water, dry at 80° C. for 10 hours to obtain a carbon cloth with a three-dimensional porous carbon layer, wherein the thickness of the three-dimensional porous carbon layer is 1-2 μm, and the surface area of the three-dimensional porous carbon in the three-dimensional porous carbon layer is 20- 80m ² /g, pore volume 10-50m ³ /g, pore diameter 80-150nm;

(4) mixing silicon nanowires with a diameter of 5-10nm and a length of 10-50nm with ethylene glycol solution (99.8% in mass concentration), and then mixing them with the carbon cloth with a three-dimensional porous carbon layer obtained in step (3) Put it into a hydrothermal reaction kettle, react under hydrothermal conditions at 150°C for 8 hours, after cooling to room temperature, take out the product from the hydrothermal reaction kettle, wash with deionized water, and then dry at 60°C for 24 hours to obtain the A three-dimensional porous carbon-wrapped silicon composite anode material.

The composite negative electrode material consists of a carbon cloth substrate, a three-dimensional porous carbon layer grown on the carbon cloth substrate, and silicon nanowires wrapped in the three-dimensional porous carbon layer, wherein the diameter of the silicon nanowires is 5- 10nm and a length of 10-50nm, based on the total weight of the three-dimensional porous carbon-wrapped silicon composite negative electrode material, wherein the content of silicon nanowires is 40-50%.

The CR2032 button battery was prepared by using the composite negative electrode material of three-dimensional porous carbon-wrapped silicon provided in this example, and the specific steps were as follows:

The three-dimensional porous carbon-wrapped silicon composite negative electrode material provided in this example was vacuum-dried in an oven at 50-150°C for 2-48 hours, and after vacuum drying, it was cut into discs with a diameter of 10 mm to prepare electrode sheets;

In a glove box filled with argon gas, use the above electrode sheet as the working electrode, microporous polypropylene as the diaphragm, and a 1mol/L solution prepared with lithium hexafluorophosphate and a mixed solvent of ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1 As the electrolyte, a metal lithium sheet was used as the counter electrode to assemble a CR2032 button battery.

The capacity of the battery is about 2000mAh g ^-1 , the Coulombic efficiency is about 98%, and the stability after 120 cycles is high.

Claims (10)

1. A composite anode material of three-dimensional porous carbon wrapped silicon, the composite anode material consists of a carbon cloth substrate, a three-dimensional porous carbon layer grown on the carbon cloth substrate, and silicon nanometers wrapped in the three-dimensional porous carbon layer Material composition. 2. the composite negative electrode material of three-dimensional porous carbon wrapping silicon according to claim 1, wherein, the thickness of described three-dimensional porous carbon layer is 0.5-100 μ m, and the surface area of the three-dimensional porous carbon in described three-dimensional porous carbon layer is 20- 300m ² /g, the pore volume is 10-200m ³ /g, and the average pore diameter is 2-200nm. 3. the composite anode material of three-dimensional porous carbon wrapping silicon according to claim 1, wherein, described silicon nanomaterial comprises silicon nanoparticle and/or silicon nanowire, and the diameter of described silicon nanoparticle is 1-150nm, so The silicon nanowires have a diameter of 5-10nm and a length of 10-50nm, based on the total weight of the three-dimensional porous carbon-wrapped silicon composite negative electrode material, wherein the content of silicon nanomaterials is 1-70%, preferably, The content of silicon nanomaterials is 40-60%. 4. The composite negative electrode material of three-dimensional porous carbon wrapped silicon according to claim 1, wherein the three-dimensional porous carbon layer is grown on the carbon cloth substrate by the following steps: starch, sodium hydroxide and water The mixture is coated on carbon cloth, then dried at 50-120°C, then calcined at 500-900°C under the protection of nitrogen and/or argon for 0.5-24 hours, then cooled to room temperature, and then placed in hydrochloric acid solution After soaking for 5-48 hours, washing and drying, a carbon cloth with a three-dimensional porous carbon layer is obtained; preferably, this step is repeated; The silicon nanomaterial is wrapped in the three-dimensional porous carbon layer through the following steps: the silicon nanomaterial is mixed with a solution of ethylene glycol and/or propylene glycol, and then mixed with the carbon cloth with the three-dimensional porous carbon layer at 90- React under hydrothermal conditions at 200°C for 2-48 hours, cool to room temperature, wash and dry to obtain the composite negative electrode material of three-dimensional porous carbon-wrapped silicon. 5. the composite negative electrode material of three-dimensional porous carbon wrapping silicon according to claim 4, wherein, the mixed solution of described starch, sodium hydroxide and water is prepared by the following steps: mass ratio is 1:(1- 100): (1-10) starch, sodium hydroxide and water are uniformly mixed, and then placed at 20-100° C. for 2-48 hours to obtain the mixed solution of starch, sodium hydroxide and water. 6. The composite negative electrode material of three-dimensional porous carbon wrapped silicon according to claim 4 or 5, wherein the amount of the mixed solution of starch, sodium hydroxide and water coated on the carbon cloth is 0.01-5g/ cm ² . 7. The composite anode material of three-dimensional porous carbon-wrapped silicon according to claim 1, which has a capacity of 500-2000mAh g ^-1 and a coulombic efficiency of 95-99%. 8. The preparation method of the composite negative electrode material of three-dimensional porous carbon wrapping silicon described in any one in claim 1-7, it comprises the following steps: (1) Coat the mixture of starch, sodium hydroxide and water on the carbon cloth, then dry at 50-120°C, and then calcinate at 500-900°C under the protection of nitrogen and/or argon for 0.5-24 hours , then cooled to room temperature, then soaked in hydrochloric acid solution for 5-48 hours, after washing and drying, a carbon cloth with a three-dimensional porous carbon layer is obtained; preferably, step (1) is repeated; (2) Mixing silicon nanomaterials with a solution of ethylene glycol and/or propylene glycol, and then reacting with the carbon cloth having a three-dimensional porous carbon layer under hydrothermal conditions at 90-200°C for 2-48 hours, and cooling to room temperature, washing and drying to obtain the composite negative electrode material of three-dimensional porous carbon-wrapped silicon. 9. A lithium-ion battery containing the composite negative electrode material of the three-dimensional porous carbon-wrapped silicon according to any one of claims 1-7. 10. The lithium ion battery according to claim 9, comprising: working electrode, counter electrode or reference electrode, electrolyte solution and separator between working electrode and counter electrode or reference electrode, wherein said working electrode A composite negative electrode material containing the three-dimensional porous carbon-wrapped silicon; Preferably, the working electrode only includes the composite negative electrode material of the three-dimensional porous carbon-wrapped silicon; or, the working electrode includes a current collector and a negative electrode material layer formed on the surface of the current collector, and the negative electrode material layer includes The composite negative electrode material containing the three-dimensional porous carbon-wrapped silicon.