Sub-micron porous Si-C/graphite anode with interpenetrated 3D conductive networks towards high-performance lithium-ion batteries

Abstract

Silicon (Si) has been envisaged as the most promising anode candidate for future lithium-ion batteries with high energy density and large power owing to its high theoretical capacity and abundance. However, the inherent drawbacks of Si anodes such as low electrical conductivity and volume variation seriously hinder their commercial scalable application. Here we demonstrate a magnesiothermic reduction process for converting marigold structured silica precursor into sub-micron silicon replicas. The complicated structured silica was converted into co-continuous composites of silicon, graphite and amorphous carbon layer by in-situ generation. This electrode delivers excellent rate capability with a discharge specific capacity of 631.7 mAh g−1 at 3 A g−1 and high cycling stability of 1114.9 mAh g−1 after 200 cycles at 0.1 A g−1. Moreover, the coulombic efficiency increased rapidly from the initial 62–97.3% after only 10 cycles and 98.8% can be obtained with negligible fading after 200 cycles. Remarkably, some byproduct partially decomposed from surfactant can be in-situ derived into amorphous carbon layer deposited in the gap of wrinkled silicon spheres, which was effectively improves the complete conductive contact and the interface compatibility between active materials. This work provides a new design strategy for preparing Si-graphite anodes suitable for commercial applications.