Exposure of functional group from hyperbranched precursor to arrange SiOC phase for lithium-ion batteries

Abstract

Polymer-derived silicon oxycarbide (SiOC) ceramics are promising anode materials for lithium-ion batteries due to their high theoretical capacity. However, controlling their structure and composition during pyrolysis is challenging. This study employs chemical methods to construct hyperbranched polysiloxane precursors, exposing varying amounts of Si–OH groups to regulate Si–C and Si–O rearrangement. The resulting SiOC ceramics exhibit high reversible phase contents and improved electrical conductivity with added phenolic resin. The optimized SiOC ceramic M1-PF delivers a reversible capacity of 775.5 mAh g−1 after 300 cycles at 0.5 A g−1, and 344 mAh g−1 at 4 A g−1. A full cell with M1-PF and LiFePO4 retains 89.7 % capacity after 100 cycles at 0.2 A g−1. This work provides new insights for customizing SiOC ceramics for advanced battery applications.