A kind of high first-efficiency silicon-carbon composite negative electrode material and preparation method thereof

Abstract

The invention relates to a high first-efficiency silicon-carbon composite negative electrode material and a preparation method thereof, belonging to the technical field of preparation of lithium-ion battery materials. Technical solution: After weighing lithium carbonate and lithium hydroxide and mixing them evenly, press them into block material A; then place the nano-silicon in the receiving vessel, and place the block material A in the heating part of the reaction vessel, and inert atmosphere and vacuum Under high temperature and bombardment voltage, lithium carbonate and lithium hydroxide were deposited on the surface of nano-silicon to obtain composite material B; composite material B was used as working electrode, saturated calomel was used as reference electrode, platinum electrode was used as counter electrode, and bistrifluoroform The ethylene carbonate of the sulfonylimide is used as a solvent for electrochemical deposition, added to an absolute ethanol solution of lithium acetate, soaked, washed and dried to obtain a silicon-carbon composite negative electrode material. The present invention coats a layer of composite material similar to SEI material on the surface of nano-silicon to avoid the consumption of lithium ions during the charging and discharging process of nano-silicon, and improve its first-time efficiency and cycle performance.

Description

technical field [0001] The invention relates to a high first-efficiency silicon-carbon composite negative electrode material and a preparation method thereof, belonging to the technical field of preparation of lithium-ion battery materials. Background technique [0002] As the market demand for high-energy-density anode materials increases, the anode materials used in lithium-ion batteries are required to have higher specific capacity and better cycle performance. At present, the negative electrode materials of lithium-ion batteries mainly include the following types: graphite-based carbon materials, amorphous carbon materials, silicon-based materials, tin-based materials, etc. Although graphite-based carbon materials are the negative electrode materials with the highest market share, their specific capacity is only 372mAh∙g -1 , it is difficult to meet the demand for high specific capacity anode materials in the future. The theoretical specific capacity of silicon materia...

AI Technical Summary

Problems solved by technology

Although graphite-based carbon materials are the negative electrode materials with the highest market share, their specific capacity is only 372mAh∙g -1 , it is difficult to meet the demand for high specific capacity anode materials in the future

The theoretical specific capacity of silicon materials is as high as 4200mAh∙g -1 However, due to the drastic volume change of silicon during the cycle, the material will be pulverized and lose its connection with the conductive substrate, which will eventually lead to a rapid decline in capacity. At the same time, the initial efficiency of its material is low (below 80%), limiting its material Promoted application of

Although the nanometerization and porosity of silicon materials can reduce the stress change of silicon in the process of lithiation and reduce the pulverization of materials, which is beneficial to improve the cycle performance of silicon-based negative electrodes, and by coating carbon materials on the surface of materials can also reduce its Expansion and its improvement of first-time efficiency, but the magnitude is not obvious, and it is still difficult to meet the market's demand for high first-efficiency, high-capacity, and high-cycle silicon-based materials. For example, the patent (CN103165874A) discloses that silicon alloy powder is used as raw material and reacted with inorganic acid Generate porous silicon particles; then wash and remove the surface silicon oxide with HF acid solution, wash and dry to obtain porous silicon materials

This method requires the use of highly corrosive HF acid, and the prepared porous silicon is not nanoscale, but the first-time efficiency of the material has not been improved, which will cause the first-time efficiency of the lithium-ion battery to be low during the use of the lithium-ion battery, resulting in the positive electrode lithium-ion The low utilization rate of its lithium-ion battery increases the cost of

The reason for the low efficiency of silicon-based materials for the first time is that the silicon material forms an SEI film during the first charging and discharging process and consumes lithium ions. Ion content continues to decrease, thereby affecting its cycle performance

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