Design of a porous Si/C particulate composite with nanoparticulate Si, polysilsesquioxane derived pore phase, and phenolic resin derived carbon for Li-ion battery anode

Silicon is one of the most promising anode materials for Li-ion batteries owing to its exceptionally high theoretical capacity, yet its practical application remains limited due to lithiation induced severe volumetric expansion and structural instability. In this work, a porous Si/C composite anode is developed by a facile and scalable process using nanocrystalline Si, a polymethylsilsesquioxane preceramic polymer as a sacrificial pore-forming template and a phenolic resin for creating the encapsulating carbon phase. The void space, created after the removal of silica from the polymer derived ceramic, directly accommodates lithiation-induced expansion of Si, while the phenolic resin-derived hard carbon shell ensures mechanical integrity and electronic conductivity. Also, the silicon to carbon ratio was further optimised to maximise electrochemical performance. The optimised composite retained 870 mAh g −1 after 300 cycles at 100 mA g −1 and 482 mAh g −1 over 200 cycles at 1 A g −1 . This work demonstrates the polymethylsilsesquioxane interlayer acting as both a conformal coating precursor and a self-sacrificing pore template as an effective design strategy for high-performance Si/C anodes for next-generation Li-ion batteries.