Calcium silicate composited nano-Si anode with low expansion and high performance for lithium-ion batteries

SiO is the promising anode material in the next-generation lithium-ion batteries (LIBs) with high energy density. However, the passivation of the silicon oxide in SiO remains challenging to reduce its irreversible reactions and volume expansion during cycling. In this work, a scalable approach is proposed to synthesize the calcium silicate/nano-silicon composites (pSi@CaO) via transforming the SiO₂ in disproportionated SiO into calcium silicate at 1000 °C. The bulk distributed calcium silicate in pSi@CaO can effectively inhibit the expansion of nano-silicon and enhance the ionic transfer. The optimized pSi@20%CaO anode demonstrates a low electrode expansion of 12.3% upon lithiation and 7.6% upon delithiation after 50 cycles. It also exhibits excellent electrochemical stability, delivering a specific capacity of 808 mAh g^–1 at 50 mA g^-1 with an initial coulumbic efficiency of 72%, and maintaining 82% capacity after 500 cycles at 1 A g^-1. The feasible CaO passivation strategy in this work is expected to promote the practical applications of Si-based anodes in high-performance LIBs.