High rate capabilities of HF-etched SiOC anode materials derived from polymer for lithium-ion batteries

Polymer-derived silicon oxycarbide (SiOC) composites have recently attracted considerable attention because of their potential as high capacity electrode for rechargeable lithium ion batteries. However, low discharge capacity at large current densities hinders its practicality. In this work, SiOC compound as anode materials is synthesized by pyrolyzing polycarbosilane with a cyclic tetramethyl tetravinyl cyclotetrasiloxane, followed by etching with HF. The obtained SiOC delivers high reversible capacities of 321, 274 and 206 mA h g^-1 and high capacity retention of 100%, 93.4% and 68% at current densities of 1000, 2000 and 4000 mA g^-1 after 200 cycles, respectively. The excellent electrochemical properties can be attributed to the increased specific surface area, enlarged volume of nano-sized pores and F-doped silicon unit in the HF-etching process, which benefit the contact between active material and electrolyte, alleviate the volume change during discharge/charge process and raise the ionic conductivity.