阅读说明：本技术 一种硅碳复合材料及其制备方法和应用 (Silicon-carbon composite material and preparation method and application thereof ) 是由 赵宇飞 林少雄 刘盛华 丁男 张辰 王叶 辛昱 于 2020-06-18 设计创作，主要内容包括：本发明公开了一种硅碳复合材料及其制备方法和应用,涉及硅材料技术领域,其制备方法包括以下步骤：将纳米硅颗粒放入反应炉的阴极台上,炉体为阳极,将炉腔抽真空后,向其中通入含碳和/或氮元素的气体使炉腔内保持低真空状态；在反应炉的阳极和阴极之间通高压电流产生辉光放电,使炉腔内的气体分解生成碳和/或氮的正离子轰击纳米硅表面,得到碳化硅和/或氮化硅包覆的碳和/或氮掺杂纳米硅材料,再将其与石墨进行复合制得硅碳复合材料。本发明中纳米硅材料经处理后包覆层薄且均匀,能够抑制硅材料在充放电中的体积膨胀,有效避免硅材料和电解液的直接接触,从而提高硅材料的首次库伦效率和循环稳定性能。(The invention discloses a silicon-carbon composite material and a preparation method and application thereof, relating to the technical field of silicon materials, wherein the preparation method comprises the following steps: placing the nano silicon particles on a cathode platform of a reaction furnace, taking the furnace body as an anode, vacuumizing the furnace chamber, and introducing gas containing carbon and/or nitrogen elements into the furnace chamber to keep the furnace chamber in a low vacuum state; high-voltage current is conducted between an anode and a cathode of the reaction furnace to generate glow discharge, so that positive ions of carbon and/or nitrogen generated by decomposition of gas in the furnace cavity bombard the surface of the nano silicon to obtain the carbon and/or nitrogen-doped nano silicon material coated by the silicon carbide and/or the silicon nitride, and the carbon and/or nitrogen-doped nano silicon material is compounded with graphite to obtain the silicon-carbon composite material. The coating layer of the processed nano silicon material is thin and uniform, so that the volume expansion of the silicon material in charging and discharging can be inhibited, and the direct contact between the silicon material and electrolyte is effectively avoided, thereby improving the first coulombic efficiency and the circulation stability of the silicon material.)

1. The preparation method of the silicon-carbon composite material is characterized by comprising the following steps:

s1, placing the nano silicon particles on a cathode platform of a reaction furnace, taking the furnace body as an anode, vacuumizing the furnace chamber, and introducing gas containing carbon and/or nitrogen to keep the furnace chamber in a low vacuum state;

s2, high-voltage current is conducted between the anode and the cathode of the reaction furnace to generate glow discharge, so that gas in the furnace cavity is decomposed to generate positive ions of carbon and/or nitrogen, and the positive ions of the carbon and/or nitrogen bombard the surface of the nano silicon to obtain the carbon and/or nitrogen-doped nano silicon material coated by the silicon carbide and/or the silicon nitride;

and S3, compounding the carbon and/or nitrogen-doped nano silicon material coated by the silicon carbide and/or the silicon nitride with graphite to obtain the silicon-carbon composite material.

2. The method of claim 1, wherein in step S1, after the chamber is evacuated to 1-0.1Pa, a gas containing carbon and/or nitrogen is introduced into the chamber to maintain the pressure in the chamber at 60-1400 Pa.

3. The method according to claim 1 or 2, wherein the gas containing carbon and/or nitrogen is one or more of methane, ethane, ethylene, propylene, acetylene, propyne, ammonia gas, nitrogen gas, carbon vapor, carbon dioxide, nitrogen dioxide, and urea vapor in S1.

4. The method as claimed in any one of claims 1 to 3, wherein the applied voltage of the high voltage current in S2 is 350-850V.

5. The method according to any one of claims 1 to 4, wherein the high voltage current is a direct current in S2.

6. The method for producing a silicon-carbon composite material according to any one of claims 1 to 5, wherein the current density of the high-voltage current in S2 is 0.5 to 2.0mA/cm²。

7. The method according to any one of claims 1 to 6, wherein the nano-silicon has a particle size of 1 to 500nm in S2.

8. The method according to any one of claims 1 to 7, wherein the graphite has a particle size of 10 to 20 μm in S3.

9. A silicon-carbon composite material produced by the production method according to any one of claims 1 to 8.

10. Use of the silicon carbon composite material of claim 9 in a negative electrode material of a lithium ion battery.

Technical Field

The invention relates to the technical field of silicon materials, in particular to a silicon-carbon composite material and a preparation method and application thereof.

Background

The endurance mileage of the power electric vehicle is related to the change of the requirements of people and the development of the future automobile industry, and in order to realize the energy density of 300wh/kg of the power battery, a ternary material is inevitably selected to replace the commercial lithium iron phosphate and lithium cobaltate as the anode material of the lithium ion battery; and the silicon-carbon material is used for replacing a graphite cathode, so that the energy density of the battery is improved by times, and the inevitable trend of the development of the new energy automobile industry is also provided.

The silicon has the advantages of lower platform potential, ultrahigh theoretical capacity (3800mAh/g, Li15Si 4; 4200mAh/g, Li15Si4 which is nearly 10 times of the capacity of the marketized graphite), high surface area, high tap density, simple preparation and the like, so the silicon has great application prospect. However, when the silicon material is used as a negative electrode material, the volume of the silicon material is greatly changed in the charge and discharge processes, so that the performance of the battery is sharply attenuated; therefore, the silicon material needs to be doped and coated and compounded with the graphite material to inhibit the volume expansion of the silicon material in the charging and discharging processes.

Disclosure of Invention

Based on the technical problems in the background art, the invention provides a silicon-carbon composite material and a preparation method and application thereof, the silicon-carbon composite material can inhibit the volume expansion of a silicon material in charging and discharging, and effectively avoids the direct contact of the silicon material and electrolyte, so that the first coulombic efficiency and the circulation stability of the silicon material are improved.

The invention provides a preparation method of a silicon-carbon composite material, which comprises the following steps:

s1, placing the nano silicon particles on a cathode platform of a reaction furnace, taking the furnace body as an anode, vacuumizing the furnace chamber, and introducing gas containing carbon and/or nitrogen to keep the furnace chamber in a low vacuum state;

s2, high-voltage current is conducted between the anode and the cathode of the reaction furnace to generate glow discharge, so that gas in the furnace cavity is decomposed to generate positive ions of carbon and/or nitrogen, and the positive ions of the carbon and/or nitrogen bombard the surface of the nano silicon to obtain the carbon and/or nitrogen-doped nano silicon material coated by the silicon carbide and/or the silicon nitride;

in the step, positive ions of carbon and/or nitrogen bombard the surface of the nano silicon, kinetic energy is converted into heat energy to heat a workpiece, and electrons are absorbed and reduced into atoms which are absorbed by the surface of the nano silicon and diffused to the inner layer to obtain the carbon and/or nitrogen doped nano silicon material; the positive ions of carbon and/or nitrogen bombard the surface of the nano silicon to generate cathode sputtering, silicon ions sputtered are combined with the carbon and/or nitrogen ions to form silicon carbide and/or silicon nitride, and the silicon carbide and/or silicon nitride are attached to the surface of the nano silicon to form a doped nano silicon material coated by the silicon carbide and/or silicon nitride;

and S3, compounding the doped nano silicon material coated by the silicon carbide and/or the silicon nitride with graphite to obtain the silicon-carbon composite material.

Preferably, in S1, after the furnace chamber is vacuumized to 1-0.1Pa, gas containing carbon and/or nitrogen elements is introduced into the furnace chamber, so that the pressure in the furnace chamber is maintained at 60-1400 Pa.

Preferably, in S1, the gas containing carbon and/or nitrogen is one or more of methane, ethane, ethylene, propylene, acetylene, propyne, ammonia gas, nitrogen gas, carbon vapor, carbon dioxide, nitrogen dioxide, urea vapor, and the like.

Preferably, in S2, the loading voltage of the high-voltage current is 350-850V.

Preferably, in S2, the high-voltage current is direct current.

Preferably, in S2, the high voltage current has a current density of 0.5-2.0mA/cm²。

Preferably, in S2, the nano silicon has a particle size of 1 to 500 nm.

Preferably, in S3, the graphite has a particle size of 10 to 20 μm.

The invention also provides the silicon-carbon composite material prepared by the method.

The invention also provides an application of the silicon-carbon composite material prepared by the method in a lithium ion battery cathode material.

Has the advantages that: the invention provides a preparation method of a silicon-carbon composite material, which is different from the traditional methods of solid phase coating, high temperature gas phase coating and the like, and is characterized in that high-voltage current is applied to generate glow discharge, so that gas in a furnace cavity is decomposed to generate positive ions of carbon and/or nitrogen, the positive ions of the carbon and/or nitrogen bombard the surface of a nano silicon to obtain a carbon and/or nitrogen doped nano silicon material coated by silicon carbide and/or silicon nitride, and the coating layer of the silicon carbide and/or the silicon nitride in the material is thin and uniform, so that the volume expansion of the silicon material in charging and discharging can be inhibited, the direct contact between the silicon material and electrolyte is effectively avoided, and the first coulomb efficiency and the circulation stability of the silicon material are improved. The silicon-carbon composite material obtained by compounding the coated doped nano silicon material and graphite can be used as a lithium ion battery cathode material to effectively improve the first coulombic efficiency, the cycle performance and the like of the battery.

Drawings

FIG. 1 is an SEM image of a silicon-carbon composite material prepared in example 1 of the present invention;

FIG. 2 is a diagram showing the charging-off first time of the silicon-carbon composite material prepared by the embodiment 1 and the conventional method;

FIG. 3 is a chargecycle chart of a silicon carbon composite material obtained by example 1 of the present invention and a conventional method;

FIG. 4 is an SEM photograph of a silicon-carbon composite material prepared in example 2 of the present invention;

FIG. 5 is a diagram of the charging and discharging for the first time in accordance with the embodiment 2 of the present invention and the silicon carbon composite material manufactured by the conventional method;

FIG. 6 is a chargecycle chart of a silicon carbon composite material obtained by example 2 of the present invention and a conventional method;

FIG. 7 is an SEM photograph of a silicon-carbon composite material prepared in example 3 of the present invention;

FIG. 8 is a charging-off diagram of a silicon-carbon composite material prepared by example 3 according to the present invention and a conventional method;

fig. 9 is a chargecycle chart of the silicon carbon composite material prepared by the embodiment 3 of the present invention and the conventional method.

Detailed Description

The technical solution of the present invention will be described in detail below with reference to specific examples.