Carbon-coated hierarchically porous silicon as anode material for lithium ion batteries

Silicon is one of the most promising anode materials for high energy density lithium ion batteries. However, its fast capacity decay due to volume expansion and the resultant particle pulverization hinders its commercial application. Diverse strategies have been proposed to reduce these effects. In this article, hierarchically porous silicon composite is formed by coating the porous silicon particles obtained by magnesiothermically reducing commercial diatomite. Both the void space between the silicon particles and the pores within each silicon particle are designed to accommodate the volume change of silicon in the charge and discharge processes. On the other hand, the carbon coating layer alleviates the volume change of silicon and maintain the electric contact between the particles. The carbon-coated hierarchically porous silicon composite based on this design concept shows much better cyclability than that of the bare porous silicon.