Synthesis of Silicon\nOxycarbide Beads from Alkoxysilane\nas Anode Materials for Lithium-Ion Batteries

Abstract

Silicon is an important anode material for lithium-ion\nbatteries\nbecause of its high theoretical capacity. However, the large volume\nexpansion of silicon anodes hinders its commercial utilization. As\nan alternative, silicon oxycarbides (SiOCs) mitigate the expansion\nof anodes during lithiation, and the synthesis of SiOC beads from\nsilanes is rather simple and at a low cost. In this study, we compared\nthree different reactor setups for making the SiOC beads from methyltrimethoxysilane\n(MTMS) and found that the control of residence time was crucial. Thereby,\nthe batch reactor turned out to be the easiest one for making monodispersed\nbeads. We also reduced the O/Si ratio of the SiOC beads by adding\ndimethyldimethoxysilane (DMDMS) for better battery performance. The\nfirst-cycle delithiation capacity of the most stable material was\nover 1796 mA h/g, with an initial Coulombic efficiency of 82%, while\nthe capacity retention after 170 cycles was 67% (992 mA h/g) at a\ncharging rate of 2 A/g in the potential range of 0.01–3 V.\nThis was among the best of the reported data so far for the SiOC beads\nfrom MTMS.