Preparation and lithium storage properties of core-shell silicon carbon composites based on sepiolite

Silicon-based anode electrode materials prepared by reducing natural silicate minerals can not only improve the electrochemical properties of silicon materials using the special structure of natural minerals, but also have the advantages of environmental friendliness and low-cost, which has attracted more and more attention. In this paper, silicon carbon composites with core-shell structure were prepared by aluminothermic reduction and solvent evaporation with natural sepiolite as raw material and asphalt as carbon source. The results show that the existing form of silicon is crystal. The silicon material prepared by aluminothermic reduction successfully maintains the hollow tubular structure of sepiolite. Carbon belongs to amorphous structure, and the carbon layer is evenly coated on the surface of silicon nanotubes. When carbon content is 15%, the core-shell structure silicon carbon composite has the best electrochemical performance. The first discharge-specific capacity of the SNT/C-15% is 1610.4 mAh/g, and the initial coulomb efficiency is 79.7%. After 500 cycles, Si/C-15% shows the highest residual capacity of 1072.4 mAh/g, and its capacity retention rate is as high as 83.5% compared to the initial charge capacity. The silicon carbon composites prepared in this paper not only show high capacity, but also have high coulomb efficiency.