Method for preparing nano silicon through three-stage grinding

Abstract

The invention belongs to the field of nano material preparation, and particularly discloses a method for preparing nano silicon through three-stage grinding. The method comprises the following steps:1) adding high-purity silicon powder, a solvent and a dispersing agent into a dispersing tank of a first-stage sand mill, and carrying out pre-dispersion; introducing the dispersed mixed solution intoa first-stage sand mill for first-stage grinding to obtain silicon slurry with the nano-silicon particle size D50 of less than 1000nm; (2) introducing the slurry subjected to primary grinding into asecond-stage sand mill for secondary grinding to obtain silicon slurry with the nano-silicon particle size D50 of less than 100nm; (3) introducing the slurry subjected to secondary grinding into a third-stage sand mill for third-stage grinding to obtain silicon slurry with the nano-silicon particle size D50 of less than 50nm, and carrying out drying to obtain nano-silicon powder. Compared with theprior art, the method disclosed by the invention is simple in preparation process and low in cost, greatly improves the wet grinding efficiency, reduces the particle size of the nano silicon, ensuresthe uniform dispersity and stability of the silicon slurry, and is suitable for industrialization.

Description

technical field [0001] The invention belongs to the field of nanometer material preparation, and in particular relates to a method for preparing nanometer silicon by three-stage grinding. Background technique [0002] Silicon has an ultra-high theoretical specific capacity (4200mAh / g) and a low delithiation potential (<0.5V), but the volume change of silicon can be as high as 300% during charge and discharge, which will cause silicon particles to break and affect the active material and assembly. The connection between the fluids is not conducive to electron transport; on the other hand, the solid electrolyte interfacial film formed between the silicon-based material and the electrolyte gradually thickens, resulting in a sharp decline in the cycle performance of the lithium battery. There are even studies that show that the first coulombic efficiency of micron-sized silicon powder is less than 40%, and the cycle performance is very poor, and the reversible capacity is alm...

AI Technical Summary

Problems solved by technology

[0002] Silicon has an ultra-high theoretical specific capacity (4200mAh / g) and a low delithiation potential (<0.5V), but the volume change of silicon can be as high as 300% during charge and discharge, which will cause silicon particles to break and affect the active material and assembly. The connection between fluids is not conducive to electron transmission; on the other hand, the solid electrolyte interface film formed between the silicon-based material and the electrolyte gradually thickens, resulting in a sharp decline in the cycle performance of lithium batteries

There are even studies that show that the first Coulombic efficiency of micron-sized silicon powder is less than 40%, and the cycle performance is very poor, and the reversible capacity is almost zero in less than 10 weeks.

In order to reduce the volume expansion of silicon particles, the most effective method is to nano-size silicon particles to reduce their absolute volume expansion. However, at this stage, the size of nano-silicon prepared by wet grinding is basically about 80-100nm, and it is difficult to achieve a smaller size.

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