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SiO is a promising anode material for next-generation lithium-ion batteries (LIBs) with high-energy density. However, the passivation of 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 calcium silicate/nanosilicon composites (pSi@CaO) by transforming the SiO2 in disproportionate SiO into calcium silicate at 1000 ℃. The bulk-distributed calcium silicate in pSi@CaO can effectively inhibit nanosilicon expansion and enhance ionic transfer. The optimized pSi@20%CaO anode demonstrates a low electrode expansion of 12.3% upon lithiation and 7.6% upon lithiation 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 Columbic efficiency of 72% and maintaining 82% capacity after 500 cycles at 1 A g−1. The feasible CaO passivation strategy proposed in this work is expected to promote practical applications of Si-based anodes in high-performance LIBs.