Silicon-carbon composite negative electrode material for lithium ion battery and preparation method thereof

Abstract

The invention relates to a silicon-carbon composite negative electrode material and a preparation method thereof. The silicon-carbon composite negative electrode material successively comprises nano silicon / graphite particles, a first carbon coating layer and an organic cracking carbon layer from inside to outside. The nano silicon / graphite particles are globular or globular-like composite particles formed by employing graphite as an inner core of a volume expansion buffer substrate and coating a nano silicon particle layer; the first carbon coating layer comprises carbon nanotubes and / or amorphous carbon, the carbon nanotubes and / or amorphous carbon are interspersed in a gap network formed by gaps of the nano silicon particles and / or are coated outside the nano silicon particle layer, so that the nano silicon is tightly wrapped between the carbon nanotubes and / or between the carbon nanotubes and the graphite substrate, and besides, the material ion conductivity is effectively enhanced; the organic cracking carbon layer is an outermost coating layer of the silicon-carbon composite negative electrode material. The silicon-carbon composite negative electrode material has excellent cycle performance, excellent multiplying power charging and discharging performance and lower volume expansion effect.

Description

technical field [0001] The invention relates to the field of lithium-ion battery negative electrode materials, in particular, the invention relates to a lithium-ion battery silicon-carbon composite negative electrode material and a preparation method thereof. Background technique [0002] Lithium-ion batteries have the advantages of high voltage, high energy density, no memory effect, long life, green and pollution-free, and low self-discharge. They have gradually become the preferred power supply equipment for various portable electronic products and are inseparable from people's daily life. [0003] Although lithium-ion batteries using graphite as the negative electrode material occupy a large proportion in the market, the theoretical specific capacity of graphite is relatively low, which is increasingly unable to meet the requirements of miniaturization of electronic equipment and high-power and high-capacity lithium-ion batteries for vehicles. . [0004] As the negative...

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Problems solved by technology

However, this method uses ultrasonic dispersion to disperse nano-silicon powder in the expanded graphite layer. It is difficult for nano-silicon to be completely inserted into the graphite layer. After suction filtration and drying, a large amount of nano-silicon powder will be enriched on the surface, and the enrichment uniformity out of control

During the charge-discharge cycle of the prepared material, the nano-silicon-enriched region will still pulverize rapidly with the charge-discharge process, and the capacity will decay.

At the same time, the intercalation of nano-silica powder in the expanded graphite layer will also cause the layered structure of graphite to be damaged to a certain extent, and the internal defects of the material will increase, resulting in a decrease in the first Coulombic efficiency of the material.

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