WO2022126882A1 - Silicon-carbon-based negative electrode material and preparation method thereof - Google Patents

Abstract

The present invention relates to the technical field of electrode materials, in particular to a silicon-carbon-based negative electrode material and a preparation method therefor. The silicon-carbon-based negative electrode material comprises a silicon material and a carbonaceous layer coating the surface of the silicon material, and the mass content of the silicon material is 30% to 50%. The silicon material is prepared by pickling a mixture of silicon oxide, a silicon-nickel alloy and a silicon-aluminum alloy, the silicon material has a porous structure, and the silicon-carbon-based negative electrode material has a porous structure. The silicon-carbon-based negative electrode material has a porous structure, which can alleviate the volume effect occurring during the process of charge and discharge, and reduce the pulverization and shedding of electroactive substances, thus improving the cycle stability of the lithium ion battery, and prolonging the service life and increasing the specific capacity of silicon-carbon-based negative electrode material. Coating the surface of a silicon material with a carbonaceous layer can effectively alleviate the problem of volume expansion of silicon materials. The silicon-carbon-based negative electrode material has a good cycle stability, a good conductivity and a high specific capacity, and also has good application prospects.

Description

Silicon carbon-based negative electrode material and preparation method thereof

CROSS-REFERENCE TO RELATED APPLICATIONS.

This application claims the priority of the Chinese patent application filed on December 15, 2020 with the application number 202011477615.5 and the invention title is "silicon carbon-based negative electrode material and its preparation method", the entire contents of which are incorporated herein by reference Applying.

technical field

The invention relates to the field of electrode materials, in particular to a silicon carbon-based negative electrode material and a preparation method thereof.

Background technique

Due to the important advantages of high voltage, high capacity, long cycle life and good safety performance, lithium-ion batteries have broad applications in portable electronic devices, electric vehicles, energy storage, space technology, biomedical engineering, defense industry, etc. It has become a research and new energy industry development hotspot that has attracted wide attention in the past decade and for a long time in the future.

technical problem

At present, the most widely used anode materials for lithium-ion batteries are carbon materials, such as natural graphite and graphitized mesocarbon microspheres. Among non-carbon anode materials, silicon has a very high theoretical specific capacity, a low lithium storage reaction voltage platform, and silicon is widely distributed in nature, and its content in the earth's crust is second only to oxygen, so silicon-based anode materials It is a new type of high-energy material with great development prospects. However, the low electronic and ionic conductivity of silicon results in poor kinetic performance of its electrochemical reaction; the cycle stability of ordinary pure silicon is poor. Moreover, the phase transition and volume expansion of silicon during the lithiation process will generate greater stress, resulting in electrode fracture and pulverization, increased resistance, and sudden drop in cycle performance. How to obtain negative electrode materials with high specific capacity, good cycle stability and small volume expansion is an urgent problem to be solved in this field.

technical solutions

According to various embodiments of the present application, a silicon carbon-based negative electrode material is provided, which has the characteristics of good cycle stability, good electrical conductivity and high specific capacity.

The invention also provides a preparation method of the silicon carbon-based negative electrode material, the preparation method obtains a good material forming effect, optimizes the material properties, is easy to operate, and facilitates popularization.

A silicon carbon-based negative electrode material, comprising a silicon material and a carbonaceous layer coated on the surface of the silicon material, the mass content of the silicon material is 30% to 50%, the mass content of the carbonaceous layer is 50% to 70%, and the mass content of the silicon material is 50% to 70%. It is prepared by pickling a mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy, the silicon material has a porous structure, and the silicon carbon-based negative electrode material has a porous structure.

For the above silicon carbon-based negative electrode material, the silicon material has a porous structure. After the carbonaceous layer is coated on the surface of the silicon material, the porous structure is still retained, that is, the silicon carbon-based negative electrode material has a porous structure, which can alleviate the volume effect during the charging and discharging process and reduce The problem of pulverization and shedding of electroactive substances, thereby improving the cycle stability of lithium-ion batteries, prolonging the service life, and increasing the specific capacity of silicon-carbon-based anode materials; coating the surface of the silicon material with a carbonaceous layer can effectively alleviate the The volume expansion of the material is the problem; the silicon carbon-based negative electrode material of the present invention has good cycle stability, good electrical conductivity and high specific capacity, and has a good application prospect.

In one embodiment, the mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.1-1:1-2:2-5.

In one of the embodiments, the general formula of silicon oxide is SiOx, 0<x<2.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: pickling the silicon material to obtain porous silicon; adding the porous silicon to an organic solvent and mixing uniformly to obtain a porous silicon slurry; grinding the porous silicon slurry; The obtained porous silicon is added to the carbon precursor, mixed evenly, and carbon-coated to form a crude silicon-carbon composite product; the crude silicon-carbon composite product is subjected to a carbonization treatment to obtain a silicon-carbon-based negative electrode material.

In one embodiment, in the step of pickling the silicon material to obtain porous silicon, the acid is hydrofluoric acid with a mass content of 5% to 8%, and the pickling is as follows: the silicon material is put into an acid solution, and the protective Gas, pickling time 3 ~ 5min.

In one embodiment, the organic solvent is ethylene glycol or ethanol.

In one embodiment, the mass content of porous silicon in the porous silicon slurry is 20%-35%.

In one embodiment, the carbon precursor is one or more of polyethylene glycol, glucose, sucrose and starch.

In one embodiment, the carbon coating treatment includes the following steps: mixing porous silicon and carbon precursor in a mass ratio of 1:5-15, stirring for 30-60 minutes, ultrasonically dispersing for 30-60 minutes, and then drying to obtain A crude silicon-carbon composite product with a carbonaceous layer.

In one embodiment, the carbonization treatment includes the following steps: putting the crude silicon-carbon composite material into a heating device, and feeding a protective gas; raising the temperature of the heating device to 150° C. to 210° C. and maintaining the temperature for 30 to 50 minutes; The temperature of the device is raised to 400°C to 550°C, and the temperature is kept for 100 to 120 minutes; the temperature of the heating device is raised to 800°C to 1000°C, the temperature is kept for 100 to 240 minutes, and cooled to room temperature to obtain a silicon carbon-based negative electrode material.

beneficial effect

The silicon carbon-based negative electrode material of the present invention includes a silicon material and a carbonaceous layer coated on the surface of the silicon material, the mass content of the silicon material is 30% to 50%, and the silicon material adopts silicon oxide, silicon The mixture of nickel alloy and silicon aluminum alloy is prepared by pickling, the silicon material has a porous structure, and the silicon carbon-based negative electrode material has a porous structure. The silicon carbon-based negative electrode material has a porous structure, which can alleviate the volume effect during the charging and discharging process and reduce the problem of pulverization and shedding of the electroactive material, thereby improving the cycle stability of the lithium-ion battery, prolonging the service life, and improving the silicon carbon-based negative electrode. The specific capacity of the material; the carbonaceous layer is coated on the surface of the silicon material, which can effectively alleviate the volume expansion problem of the silicon material; the silicon carbon-based negative electrode material of the present invention has good cycle stability, good conductivity, high specific capacity, and good application prospects.

Embodiments of the present invention

In order to facilitate understanding of the present invention, the present invention will be described more fully below. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the present disclosure is provided.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

The present invention provides a silicon carbon-based negative electrode material, which comprises a silicon material and a carbonaceous layer coated on the surface of the silicon material, wherein the mass content of the silicon material is 30% to 50%, and the mass content of the carbonaceous layer is 50% to 70%. %, the silicon material is made by pickling a mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy, the silicon material has a porous structure, and the silicon carbon-based negative electrode material has a porous structure.

The silicon material in the above-mentioned silicon carbon-based negative electrode material has a porous structure, and after the carbonaceous layer is coated on the surface of the silicon material, the porous structure is still retained, that is, the silicon carbon-based negative electrode material has a porous structure, which can alleviate the volume effect in the charging and discharging process. Reduce the problem of pulverization and shedding of electroactive materials, thereby improving the cycle stability of lithium-ion batteries, prolonging service life, and increasing the specific capacity of silicon-carbon-based anode materials; coating the surface of silicon materials with carbonaceous layers can effectively alleviate Volume expansion of silicon materials.

In one embodiment, the mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.1-1:1-2:2-5, and the crystal structures of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy are different, The structure of the porous silicon element formed after pickling is also different. The porous silicon oxide, silicon-nickel alloy and silicon-aluminum alloy obtained after pickling support each other, which fully alleviates the volume effect of the charging and discharging process. When the mass ratio of silicon-nickel alloy and silicon-aluminum alloy is 0.1-1:1-2:2-5, the mitigation effect is better. More preferably, the mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is selected to be 0.6-1:1-2:3-4.

In one embodiment, the general formula of silicon oxide is SiOx, 0<x<2.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100 : pickling the silicon material to obtain porous silicon.

In the step of pickling the silicon material to obtain porous silicon, the acid is hydrofluoric acid with a mass content of 5% to 8%. Wash time 3 ~ 5min. The function of bubbling is mainly used to disperse the silicon material, so that in the pickling process, the dispersion is uniform, the pickling is sufficient, and the pore forming structure is adjusted. The protective gas is argon, helium, and nitrogen, and the gas flow is 1-5mL/min. The protective gas is slowly injected, and the silicon materials are blown to collide and disperse each other, so that all surfaces of the silicon material can contact the acid solution, and the bubbles blown in. It is relatively slow, and will not cause the problem that the acid solution hits the silicon material in a large area and causes the deformation of the porous structure.

Further, the temperature of the acid solution is 10°C to 30°C to avoid the problems of too fast reaction speed, too large pore size and insufficient density. Preferably, the temperature of the acid solution is 18°C to 25°C.

After the silicon material is acid washed, it is washed with deionized water and then dried. The times of pickling can be one or two or three or more times, which mainly depends on the molding result of the silicon material.

S200: adding porous silicon into an organic solvent and mixing uniformly to obtain a porous silicon slurry.

The organic solvent is ethylene glycol or ethanol.

The mass content of porous silicon in the porous silicon slurry is 20% to 35%.

S300: grinding the porous silicon slurry. Wet ball milling can be used. The D50 particle size of the porous silicon after grinding is less than or equal to 50 nm, and preferably, the D50 particle size of the porous silicon is 10-40 nm.

S400: adding the ground porous silicon into the carbon precursor, mixing uniformly, and performing carbon coating treatment to form a crude silicon-carbon composite product.

The carbon precursor is one or more of polyethylene glycol, glucose, sucrose and starch.

The carbon coating treatment includes the following steps: mixing porous silicon and carbon precursor in a mass ratio of 1:5-15, stirring for 30-60 minutes, ultrasonically dispersing for 30-60 minutes, and then drying to obtain silicon with a carbonaceous layer Crude carbon composite products.

Preferably, magnetic stirring is used for stirring, and the stirring temperature is 20°C to 30°C, that is, room temperature.

Preferably, spray drying is used for drying, and the pressure of spray drying is 0.2-0.4 Mpa, the inlet temperature is 180-240°C, and the outlet temperature is 120-180°C.

S500: carbonizing the crude silicon-carbon composite material to obtain a silicon-carbon-based negative electrode material.

In one embodiment, the carbonization treatment includes the following steps: putting the crude silicon-carbon composite material into a heating device, and feeding a protective gas; raising the temperature of the heating device to 150° C. to 210° C. and keeping the temperature for 30-50 minutes; The temperature is raised to 400°C to 550°C, and the temperature is kept for 100 to 120 minutes; the temperature of the heating device is raised to 800°C to 1000°C, the temperature is kept for 100 to 240 minutes, and then cooled to room temperature to obtain a silicon carbon-based negative electrode material.

The protective gas is one of nitrogen, helium, neon, argon, hydrogen and argon-hydrogen, and the flow rate is 30-55 mL/min.

The silicon carbon-based negative electrode material of the present invention has good cycle stability, good electrical conductivity, high specific capacity, and the preparation method is easy to operate, and the material is cheap and easy to obtain, and has a good application prospect.

The following are specific examples.

Embodiment 1: The silicon carbon-based negative electrode material of this embodiment includes a silicon material and a carbonaceous layer coated on the surface of the silicon material. The mass content of the silicon material is 30%, and the mass content of the carbonaceous layer is 70%. The mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is made by pickling, and the silicon material has a porous structure.

The mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.1:1:5.

The general formula of silicon oxide is SiO2.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100: put the silicon material into a hydrofluoric acid solution with a mass content of 5%, the temperature of the acid solution is 25°C, and the protective gas argon is introduced, and the gas flow is 5mL/min, pickling time 4min, after the silicon material is pickled, washed with deionized water, and then dried to obtain porous silicon.

S200 : adding the porous silicon into the organic solvent ethylene glycol, and mixing uniformly to obtain a porous silicon slurry, and the mass content of the porous silicon in the porous silicon slurry is 30%.

S300: The porous silicon slurry is ground by wet ball milling, and the D50 particle size of the porous silicon after grinding is 10-40 nm.

S400: Add the ground porous silicon to the carbon precursor polyethylene glycol, the mass ratio of the porous silicon and the carbon precursor is 1:15, and the mixture is uniform; magnetic stirring is used, and the stirring temperature is 20 °C, and after 40 minutes, ultrasonic After dispersing for 30min, spray drying was used. The pressure of spray drying was 0.2Mpa, the inlet temperature was 180°C, and the outlet temperature was 180°C to obtain a crude silicon-carbon composite product with a carbonaceous layer.

S500: Put the crude silicon-carbon composite material into the heating device, and introduce the protective gas nitrogen with a flow rate of 30 mL/min; increase the temperature of the heating device to 150°C, and keep the temperature for 50 minutes; increase the temperature of the heating device to 450°C, keep the temperature 120min; raising the temperature of the heating device to 1000°C, keeping the temperature for 200min, and cooling to room temperature to obtain a silicon carbon-based negative electrode material.

Embodiment 2: The silicon carbon-based negative electrode material of this embodiment includes a silicon material and a carbonaceous layer coated on the surface of the silicon material. The mass content of the silicon material is 35%, and the mass content of the carbonaceous layer is 65%. The mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is made by pickling, and the silicon material has a porous structure.

The mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.6:1.5:3.

The general formula of silicon oxide is SiO1.5.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100: put the silicon material into a hydrofluoric acid solution with a mass content of 6%, the temperature of the acid solution is 18°C, and the protective gas nitrogen is introduced, and the gas flow rate is 2mL /min, the pickling time is 5min, the silicon material is washed with deionized water after pickling, and then dried to obtain porous silicon.

S200 : adding the porous silicon into the organic solvent ethanol, and mixing uniformly to obtain a porous silicon slurry, and the mass content of the porous silicon in the porous silicon slurry is 31%.

S300: The porous silicon slurry is ground by wet ball milling, and the D50 particle size of the porous silicon after grinding is 10-40 nm.

S400: Add the ground porous silicon to the carbon precursor polyethylene glycol and starch, the mass ratio of the porous silicon and the carbon precursor is 1:13, and the mixture is uniform; magnetic stirring is used, and the stirring temperature is 20 °C, and after 50 minutes, Ultrasonic dispersion was carried out for 30 minutes, and then spray drying was used. The pressure of spray drying was 0.2Mpa, the inlet temperature was 200°C, and the outlet temperature was 150°C to obtain a crude silicon-carbon composite product with a carbonaceous layer.

S500: Put the crude silicon-carbon composite material into the heating device, and feed the protective gas nitrogen with a flow rate of 55 mL/min; raise the temperature of the heating device to 150°C, and keep the temperature for 50 minutes; raise the temperature of the heating device to 550°C, keep the temperature 100min; raising the temperature of the heating device to 900° C., maintaining the temperature for 200min, and cooling to room temperature to obtain a silicon carbon-based negative electrode material.

Embodiment 3: The silicon carbon-based negative electrode material of this embodiment includes a silicon material and a carbonaceous layer coated on the surface of the silicon material. The mass content of the silicon material is 37%, and the mass content of the carbonaceous layer is 63%. The mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is made by pickling, and the silicon material has a porous structure.

The mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.6:1.5:3.

The general formula of silicon oxide is SiO0.8.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100: put the silicon material into a hydrofluoric acid solution with a mass content of 5%, the temperature of the acid solution is 20°C, and the protective gas nitrogen is introduced, and the gas flow rate is 2mL /min, the pickling time is 5min, the silicon material is washed with deionized water after pickling, and then dried to obtain porous silicon.

S200 : adding the porous silicon into the organic solvent ethylene glycol, and mixing uniformly to obtain a porous silicon slurry, and the mass content of the porous silicon in the porous silicon slurry is 34%.

S300: The porous silicon slurry is ground by wet ball milling, and the D50 particle size of the porous silicon after grinding is 10-40 nm.

S400: Add the ground porous silicon to the carbon precursor glucose, the mass ratio of the porous silicon and the carbon precursor is 1:10, and mix evenly; use magnetic stirring, the stirring temperature is 30 °C, after 35 minutes, ultrasonically disperse for 60 minutes, Then, spray drying is used, the pressure of spray drying is 0.3Mpa, the inlet temperature is 205°C, and the outlet temperature is 120°C to obtain a crude silicon-carbon composite product with a carbonaceous layer.

S500: Put the crude silicon-carbon composite material into the heating device, and introduce the protective gas nitrogen with a flow rate of 50 mL/min; raise the temperature of the heating device to 210°C, and keep the temperature for 40 minutes; raise the temperature of the heating device to 500°C, keep the temperature 110min; raise the temperature of the heating device to 1000°C, keep the temperature for 240min, and cool to room temperature to obtain a silicon carbon-based negative electrode material.

Embodiment 4: The silicon carbon-based negative electrode material of this embodiment includes a silicon material and a carbonaceous layer coated on the surface of the silicon material. The mass content of the silicon material is 40%, and the mass content of the carbonaceous layer is 60%. The mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is made by pickling, and the silicon material has a porous structure.

The mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 1:1:4.

The general formula of silicon oxide is SiO1.2.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100: put the silicon material into a hydrofluoric acid solution with a mass content of 6%, the temperature of the acid solution is 25°C, and the protective gas nitrogen is introduced, and the gas flow rate is 2mL /min, the pickling time is 3min, the silicon material is washed with deionized water after pickling, and then dried to obtain porous silicon.

S200 : adding the porous silicon into the organic solvent ethylene glycol, and mixing uniformly to obtain a porous silicon slurry, and the mass content of the porous silicon in the porous silicon slurry is 25%.

S300: The porous silicon slurry is ground by wet ball milling, and the D50 particle size of the porous silicon after grinding is 10-40 nm.

S400: Add the ground porous silicon to one or more of the carbon precursors polyethylene glycol, glucose, sucrose and starch, the mass ratio of the porous silicon and the carbon precursor is 1:9, and the mixture is uniform; the magnetic force is used Stir, the stirring temperature is 25 ° C, after 30 min, ultrasonic dispersion is performed for 60 min, and then spray drying is used. The pressure of spray drying is 0.3 Mpa, the inlet temperature is 190 ° C, and the outlet temperature is 120 ° C. A layer with a carbonaceous layer is obtained. The crude silicon carbon composite product.

S500: Put the crude silicon-carbon composite material into the heating device, and introduce the protective gas nitrogen with a flow rate of 35 mL/min; raise the temperature of the heating device to 150°C, and keep the temperature for 50 minutes; raise the temperature of the heating device to 400°C, keep the temperature 120min; raising the temperature of the heating device to 950° C., maintaining the temperature for 140min, and cooling to room temperature to obtain a silicon carbon-based negative electrode material.

Embodiment 5: The silicon carbon-based negative electrode material of this embodiment includes a silicon material and a carbonaceous layer coated on the surface of the silicon material. The mass content of the silicon material is 45%, and the mass content of the carbonaceous layer is 55%. The mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is made by pickling, and the silicon material has a porous structure.

The mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.8:1:4.

The general formula of silicon oxide is SiO1.8.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100: put the silicon material into a hydrofluoric acid solution with a mass content of 5.5%, the temperature of the acid solution is 25°C, and the protective gas nitrogen is introduced, and the gas flow rate is 3mL /min, the pickling time is 5min, the silicon material is washed with deionized water after pickling, and then dried to obtain porous silicon.

S200 : adding the porous silicon into the organic solvent ethylene glycol, and mixing uniformly to obtain a porous silicon slurry, and the mass content of the porous silicon in the porous silicon slurry is 23%.

S300: The porous silicon slurry is ground by wet ball milling, and the D50 particle size of the porous silicon after grinding is 10-40 nm.

S400: Add the ground porous silicon to one or more of the carbon precursors polyethylene glycol, glucose, sucrose and starch, the mass ratio of the porous silicon and the carbon precursor is 1:8, and the mixture is uniform; magnetic Stir, the stirring temperature is 20 ° C, after 50 minutes, ultrasonic dispersion is carried out for 30 minutes, and then spray drying is used. The pressure of spray drying is 0.2 Mpa, the inlet temperature is 240 ° C, and the outlet temperature is 150 ° C to obtain a carbonaceous layer. The crude silicon carbon composite product.

S500: put the crude silicon-carbon composite material into the heating device, and introduce the protective gas nitrogen with a flow rate of 45 mL/min; raise the temperature of the heating device to 180°C, and keep the temperature for 30 minutes; raise the temperature of the heating device to 400°C, keep the temperature 100min; raise the temperature of the heating device to 1000°C, keep the temperature for 240min, and cool to room temperature to obtain a silicon carbon-based negative electrode material.

Embodiment 6: The silicon carbon-based negative electrode material of this embodiment includes a silicon material and a carbonaceous layer coated on the surface of the silicon material. The mass content of the silicon material is 50%, and the mass content of the carbonaceous layer is 50%. The mixture of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is made by pickling, and the silicon material has a porous structure.

The mass ratio of silicon oxide, silicon-nickel alloy and silicon-aluminum alloy is 0.5:2:2.

The general formula of silicon oxide is SiO1.9.

The preparation method of the above-mentioned silicon carbon-based negative electrode material includes the following steps: S100: put the silicon material into a hydrofluoric acid solution with a mass content of 8%, the temperature of the acid solution is 20°C, and the protective gas nitrogen is introduced, and the gas flow rate is 2mL /min, the pickling time is 5min, the silicon material is washed with deionized water after pickling, and then dried to obtain porous silicon.

S200 : adding the porous silicon into the organic solvent ethylene glycol, mixing uniformly, to obtain a porous silicon slurry, and the mass content of the porous silicon in the porous silicon slurry is 20%.

S300: The porous silicon slurry is ground by wet ball milling, and the D50 particle size of the porous silicon after grinding is 10-40 nm.

S400: Add the ground porous silicon to the carbon precursor sucrose and starch, the mass ratio of the porous silicon and the carbon precursor is 1:5, and mix evenly; magnetic stirring is used, and the stirring temperature is 20 °C, and after 30 minutes, ultrasonic dispersion is carried out. 50min, and then use spray drying, the pressure of spray drying is 0.2Mpa, the inlet temperature is 200°C, and the outlet temperature is 160°C to obtain a crude silicon-carbon composite product with a carbonaceous layer.

S500: put the crude silicon-carbon composite material into the heating device, and introduce the protective gas nitrogen with a flow rate of 35mL/min; raise the temperature of the heating device to 200°C, and keep the temperature for 50min; raise the temperature of the heating device to 450°C, keep the temperature 120min; raising the temperature of the heating device to 800°C, keeping the temperature for 240min, and cooling to room temperature to obtain a silicon carbon-based negative electrode material.

Comparative Example 1: In this comparative example, a silicon carbon-based negative electrode material was prepared in basically the same way as in Example 4, except that the silicon material was only made of silicon oxide and did not contain silicon-nickel alloy and silicon-aluminum alloy.

Comparative Example 2: In this comparative example, a silicon carbon-based negative electrode material was prepared in the same manner as in Example 4, except that the silicon material was only made of silicon-nickel alloy, and did not contain silicon oxide and silicon-aluminum alloy.

Comparative Example 3: In this comparative example, a silicon-carbon-based negative electrode material was prepared in the same manner as in Example 4, except that the silicon material was only made of silicon-aluminum alloy and did not contain silicon oxide and silicon-nickel alloy.

Electrochemical performance test: The silicon carbon-based negative electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 3 and commercially available common negative electrode materials were respectively made into negative electrode plates, and then half-cells were made, and the related electrical properties were tested. The chemical properties are shown in Table 1.

The half cell is assembled into a button cell with the active material as the positive electrode and the lithium sheet as the negative electrode, and the electrolyte is LiPF6/EC:DEC (volume ratio is 1:1). The electrochemical test was carried out at room temperature, the cut-off charge-discharge voltage was 0.02-1.5V, the charge-discharge current density was 0.2mA/cm2, the first reversible specific capacity was tested at 0.1C, and the cycle efficiency was tested 50 times at 0.2C.

Table 1

It can be seen from the test results in Table 1 that the electrochemical properties of the silicon-carbon-based negative electrodes of Examples 1 to 6 are much better than those of the silicon-carbon-based negative electrodes of Comparative Examples 1 to 3. The mixture with the silicon-aluminum alloy is pickled into a silicon material, and the preparation method of the present invention can be used to prepare a silicon-carbon-based negative electrode material with good cycle stability, good electrical conductivity and high specific capacity.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. A silicon carbon-based negative electrode material is characterized in that it comprises a silicon material and a carbonaceous layer coated on the surface of the silicon material, the mass content of the silicon material is 30% to 50%, and the silicon material is made of silicon The mixture of oxide, silicon-nickel alloy and silicon-aluminum alloy is prepared by pickling, the silicon material has a porous structure, and the silicon carbon-based negative electrode material has a porous structure.
2. The silicon carbon-based negative electrode material according to claim 1, wherein the mass ratio of the silicon oxide, silicon-nickel alloy and silicon-aluminum alloy in the silicon material is 0.1-1:1-2:2- 5.
3. The silicon carbon-based negative electrode material according to claim 1, wherein the general formula of the silicon oxide is SiOx, 0<x<2.
4. The method for preparing a silicon carbon-based negative electrode material according to any one of claims 1 to 3, comprising the following steps: pickling the silicon material to obtain porous silicon; adding the porous silicon to an organic solvent and mixing evenly , obtain porous silicon slurry; grind the porous silicon slurry; add the ground porous silicon into the carbon precursor, mix evenly, and carry out carbon coating treatment to form a crude silicon-carbon composite product; The crude silicon-carbon composite material is subjected to carbonization treatment to obtain a silicon-carbon-based negative electrode material.
5. The method for preparing a silicon carbon-based negative electrode material according to claim 4, wherein in the step of acid-washing the silicon material to obtain porous silicon, the acid is hydrofluorine with a mass content of 5% to 8% Acid, pickling: put silicon material into acid solution, pass protective gas, pickling time 3-5min.
6. The method for preparing a silicon carbon-based negative electrode material according to claim 4, wherein the organic solvent is ethylene glycol or ethanol.
7. The method for preparing a silicon carbon-based negative electrode material according to claim 4, wherein the mass content of the porous silicon in the porous silicon slurry is 20% to 35%.
8. The method for preparing a silicon carbon-based negative electrode material according to claim 4, wherein the carbon precursor is one or more of polyethylene glycol, glucose, sucrose and starch.
9. The method for preparing a silicon-carbon-based negative electrode material according to claim 5, wherein the carbon coating treatment comprises the following steps: mixing the porous silicon and the carbon precursor in a mass ratio of 1:5 to 15; After stirring for 30-60 minutes, ultrasonically dispersing for 30-60 minutes, and then drying, to obtain a crude silicon-carbon composite product with a carbonaceous layer.
10. The method for preparing a silicon-carbon-based negative electrode material according to claim 5, wherein the carbonization treatment comprises the following steps: putting the crude silicon-carbon composite material into a heating device, and feeding a protective gas; The temperature of the heating device is raised to 150°C to 210°C, and the temperature is kept for 30 to 50 minutes; the temperature of the heating device is raised to 400°C to 550°C, and the temperature is kept for 100 to 120 minutes; the temperature of the heating device is raised to 800°C to 1000°C ℃, heat preservation for 100-240 min, and cooling to room temperature to obtain a silicon carbon-based negative electrode material.