Silicon composite negative electrode material of lithium ion battery, preparation method thereof and lithium ion battery

Abstract

The invention provides a silicon composite negative electrode material, which comprises nanometer silicon secondary particles, a graphene layer and amorphous carbon, wherein the graphene and the nanometer silicon secondary particles have a core-shell structure, the graphene layer is a shell, and the nanometer silicon secondary particles are a core; gaps are formed between the graphene layer and the nanometer silicon secondary particles; and the amorphous carbon is filled in the vacancy of the graphene layer. According to the invention, the structure of the silicon composite negative electrodematerial is improved, and especially the gaps are reserved between the graphene layer and the nanometer silicon secondary particles, so that a space is reserved for expansion of the silicon material in the charging and discharging process. Meanwhile, amorphous carbon is obtained by roasting a specific carbon source, so that defects of the graphene are effectively compensated, the gaps can be effectively filled, and expansion failure in the later charging and discharging process is prevented. In addition, the preparation method of the silicon composite negative electrode material provided by the invention is simple and easy to implement, and has a prospect of large-scale application.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and relates to a silicon composite negative electrode material and a preparation method thereof, and a lithium ion battery, in particular to a silicon composite negative electrode material for a lithium ion battery, a preparation method thereof, and a lithium ion battery. Background technique [0002] Lithium-ion batteries usually include positive electrodes, negative electrodes, separators, electrolytes, and shells. They have the advantages of high operating voltage, high specific energy, long cycle life, light weight, less self-discharge, no memory effect, and high cost performance. The main selection object of rechargeable power supply in the fields of electric vehicles, artificial satellites, aerospace and other fields. However, as people have higher requirements for battery capacity and long cycle life in electronic equipment, the performance of existing lithium-ion batteries i...

AI Technical Summary

Problems solved by technology

However, the intercalation and extraction of lithium ions in the silicon negative electrode material during the charging and discharging process will cause the silicon material to experience 400% expansion and contraction.

Such a large volume change during the cycle will cause the mechanical force to gradually pulverize the silicon anode material, causing the structure to collapse, eventually causing the electrode active material to separate from the current collector, losing electrical contact, cutting off the electronic path, and finally causing The cycle performance of the battery is greatly reduced; and due to this volume effect, the continuous fragmentation of the silicon negative electrode material will make the SEI film formed on the surface unstable, and with the destruction of the electrode structure, a new SEI film is continuously formed on the exposed silicon surface. Exacerbated silicon corrosion and capacity fading, making the charging efficiency lower

At the same time, the conductivity of silicon is poor, and these shortcomings have caused great obstacles to the practical application of silicon-based anode materials.

Therefore, these reasons make the cycle performance of silicon anode materials very poor

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