Polyhedral Oligomeric Silsesquioxane-Based SiOC Coating for Robust Silicon Nanoparticle Anodes in Lithium-Ion Batteries

Silicon-based anode materials are regarded as an ideal choice for high-performance lithium-ion battery anodes because of their high specific capacities and abundant resources. Carbon coating is an effective strategy to mitigate their significant volume expansion, but some carbon materials have low mechanical strength. SiOC has high chemical stability and mechanical properties, which can make up for this weakness. Here, we report a simple SiOC coating method for Si nanoparticles prepared from the in situ condensation of phenyl-POSS (polyhedral oligomeric silsesquioxane) and subsequent carbonization. POSS disperses well and forms a uniform and dense SiOC coating after polycondensation. Its cage structure creates pores that help buffer silicon expansion and provide more pathways for lithium-ion transport. SiOC formed by phenyl-POSS has a high carbon content which gives it excellent electrical conductivity, and its rigid cross-linked network between phenyl groups can effectively limit silicon’s volume expansion. The optimized sample has a high reversible capacity of 985.0 mAh g–1 at 0.5 A g–1, and it still remains 866.7 mAh g–1 with a retention rate of 90.1% after 200 cycles. The excellent electrochemical performance demonstrates that phenyl-POSS has great potential as a coating material to boost the structural stability of silicon anodes, offering an approach for utilizing phenyl-POSS in electrochemical applications.