Dispersion optimization of Si nanoparticles in Si@SiOC composites via ascorbic acid for high-performance Si-based Li-Ion batteries

Abstract

Silicon is a promising anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity, but its practical application is hindered by low electrical conductivity and large volume expansion during cycling. Silicon oxycarbide (SiOC) serves as an effective buffering matrix for embedding Si nanoparticles (NPs); however, uncontrolled aggregation of Si NPs still induces structural degradation and limits cyclability. In this study, ascorbic acid (AA) was introduced as a dispersing agent to achieve uniform Si NP dispersion within the SiOC matrix. The improved dispersion effectively mitigated localized stress and suppressed SEI overgrowth, thereby preserving structural integrity during cycling. In addition, the incorporation of AA promoted the formation of free carbon domains (FCDs) during pyrolysis, enhancing the electronic conductivity of the composite. As a result, the optimized Si@SiOC-A5.0 electrode delivered a high initial capacity of 1057 mA h g−1 and maintained 93.3 % capacity retention after 200 cycles. This work demonstrates that controlling Si NP dispersion through AA-assisted synthesis is an effective and scalable strategy for improving the electrochemical stability and durability of Si-based composite anodes.