Confining silicon nanoparticles into porous-tight dual carbon layers for lithium-ion batteries

Porous silicon-carbon composite is considered as one of the most popular approaches to replace traditional graphite for high-energy lithium-ion batteries (LIBs). However, the introduction of carbon and pores usually involves complicated and environmentally unfriendly processes like etching, salt washing and metallothermic reduction. Here, we reported a facial way to fabricate a porosity-compactness dual-layers silicon-carbon composite by liquid phase solidification and carbonization. The inner citric acid constructs a porous carbon layer to provide extra space to accommodate volume expansion and facilitate electron and ion transform, and the outer pitch forms tough and compact carbon layer to stable the overall structure and to protect Si particles from electrolyte, thus improving the stability in the long run and guaranteeing initial coulombic efficiency (ICE) simultaneously. The as prepared electrode exhibited a gratifying cycling performance and a good ICE (79.4 %), and the capacity retention is up to 86.9 % after 100 cycles at 0.5 A g- 1. The capacity can still maintain 538.1 mA h g- 1 at 2 A g- 1, and this structure greatly facilitate charge transport and Li-ion transform (1.3x10- 19 cm2 s-1). This facial preparation process of porous silicon-carbon anodes may pave the way for the potential practical application in high energy LIBs.