A preparation method and product of rectorite-based porous silicon-carbon composite material

Abstract

The invention belongs to the technical field of preparation of a porous silicon carbon composite material, and discloses a preparation method of a rectorite-based porous silicon carbon composite material and a product of the rectorite-based porous silicon carbon composite material. The preparation method comprises the steps of (1) uniformly mixing rectorite, magnesium powder and sodium chloride, and performing magnesiothermic reduction on a mixture under an argon atmosphere; (2) uniformly dispersing the material after magnesiothermic reduction in deionized water, removing a supernatant liquidafter performing full stirring and standing, and reserving a precipitant; (3) adding an HC1 solution into the precipitant for acid pickling; (4) washing the material subjected after acid pickling withan HF solution, and obtaining a porous silicon material after filtering and washing; and (5) placing the porous silicon material in a hydrogen and argon mixed atmosphere for heating, introducing acetylene gas for chemical vapor deposition (CVD) carbon coating, and cooling to obtain the porous silicon carbon composite material. By the preparation method, conversion from the rectorite to sheet-shaped porous silicon is achieved, and the prepared porous silicon carbon composite material is high in reversible capacity and has favorable cycle stability and rate property.

Description

technical field [0001] The invention belongs to the technical field of porous silicon-carbon composite material preparation, and more specifically relates to a method for preparing a rectorite-based porous silicon-carbon composite material and a product thereof. Background technique [0002] The miniaturization of portable mobile devices and the rapid development of electric vehicles have put forward higher requirements for energy storage systems, especially for the energy density and power density of lithium-ion batteries. Silicon-based anode materials are expected to replace commercial graphite as the next-generation anode material due to their high capacity, low lithium-deintercalation voltage, and environmental friendliness. The porous hierarchical micro-nano structure can effectively alleviate the volume expansion of silicon materials, reduce the polarization and improve the reversibility of lithium intercalation and extraction. However, due to the low intrinsic conduc...

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Problems solved by technology

Using the "Top-down" method to directly etch silicon is one of the methods to prepare porous silicon materials, but this method has low utilization rate of raw materials and high energy consumption

In the prior art, there is a method for preparing porous silicon by using clay ore mainly based on montmorillonite as raw material and utilizing magnesia thermal reduction; since the magnesia thermal reaction is a violent exothermic reaction, local overheating will occur and the Si nucleation growth rate will be too high. Fast, resulting in too large particle size is not conducive to alleviating the volume expansion effect of silicon; while the interlayer spacing of montmorillonite materials is too small, it cannot effectively slow down the nucleation and crystallization process of silicon, and it is necessary to intercalate or exfoliate montmorillonite to effectively avoid it. Overgrowth of silicon nanocrystals to maintain sheet-like structure

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