Lithium battery negative electrode material with nano-silicon retained in carbon shell and its production method and use

Abstract

The invention relates to a lithium ion battery negative electrode material with nanometer silicon reserved in a carbon shell and fabrication method and application of the lithium ion battery negativeelectrode material. According to the method, waste single-crystal micro powder wrapped with an organic matter is oxidized to a composite with nanometer silicon embedded into silicon oxide in one stepby wet advance oxidization, and an expansion-resistant structure with the nanometer silicon reserved in a carbon layer is formed by the traditional steps of coating a carbon layer through carbonization and corroding to remove the silicon oxide. By the method, solid waste is eliminated, the environmental pollution is reduced, and the cost of the nanometer silicon which can be used for the lithium battery negative electrode material is greatly reduced.

Description

technical field [0001] The invention belongs to a method for treating waste silicon powder coated with organic matter, and in particular relates to a lithium battery negative electrode material with nano-silicon stored in a carbon shell, a preparation method and application thereof. Background technique [0002] Silicon is the most productive and widely used material in the modern semiconductor industry. The main process of silicon wafer production is completed by crystal growth, crystal cutting and other machining steps. For example, silicon wafers in the photovoltaic industry are mainly composed of silicon ingots squaring, truncating, edging, wire cutting and other steps. [0003] With the rapid development of the photovoltaic industry, the amount of silicon materials has expanded rapidly, and has now exceeded the amount in the semiconductor field. In 2014, the amount of domestically produced high-purity polysilicon and imported polysilicon reached about 220,000 tons. Th...

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Problems solved by technology

At present, the negative electrode materials of lithium batteries in commercial use are mainly carbon materials such as graphite, but the capacity of graphite negative electrode is very close to its theoretical capacity (372mAh / g), while silicon has a specific capacity as high as 4200mAh / g, which is an ideal high specific capacity. And a safe negative electrode material, silicon will have a volume change of 320% during the lithium intercalation and delithiation process, which often causes the active material to pulverize and fall off, and lose its charge and discharge characteristics

After years of research, through improvements such as nanonization, carbon coating, and structural design, it is basically possible to deal with the volume change of silicon in the process of charging and discharging lithium. Its cost is very high, and it has reached 200,000-300,000 / ton at present, and nano-silicon is easy to agglomerate, which further affects the dispersion of silicon-carbon anode materials

In general, the high cost of nano-silicon and its easy agglomeration and non-conductive properties restrict the industrialization process of silicon-carbon anode materials. Therefore, a low-cost method of using waste silicon powder from photovoltaic cutting to prepare nano-silicon for lithium batteries The manufacture of silicon carbon anode materials has become an urgent problem to be solved in the industry

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