Electrolytic silicon/graphite composite from SiO2/graphite porous electrode in molten salts as a negative electrode material for lithium-ion batteries

Nano-silicon (nano-Si) and its composites have been regarded as the most promising negative electrode materials for producing the next-generation Li-ion batteries (LIBs), due to their ultrahigh theoretical capacity. However, the commercial applications of nano Si-based negative electrode materials are constrained by the low cycling stability and high costs. The molten salt electrolysis of SiO2 is proven to be suitable to produce nano-Si with the advantages of in-situ microstructure control possibilities, cheap affordability and scale-up process capability. Therefore, an economical approach for electrolysis, with a SiO2/graphite porous electrode as cathode, is adopted to produce nano-Si/graphite composite negative electrode materials (SGNM) in this study. The electrolytic product of the optimized porous electrode is taken as the negative electrode materials for LIBs, and it offers a capacity of 733.2 mAh·g−1 and an initial coulombic efficiency of 86.8% in a coin-type cell. Moreover, the capacity of the SGNM retained 74.1% of the initial discharging capacity after 50 cycles at 0.2C, which is significantly higher than that of the simple mixture of silicon and graphite obtained from the formation of silicon carbide (SiC) between nano-Si and graphite particles. Notably, this new approach can be applied to a large-scale production.