Stable and Efficient Li-Ion Battery Anodes Prepared from Polymer-Derived Silicon Oxycarbide-Carbon Nanotube Shell/Core Composites

We demonstrate the synthesis and electrochemical performance of polymer-derived silicon oxycarbide-carbon nanotube (SiOC-CNT) composites as a stable lithium intercalation material for secondary battery applications. Composite synthesis was achieved through controlled thermal decomposition of 1,3,5,7-tetramethyl 1,3,5,7-tetravinyl cyclotetrasiloxane (TTCS) precursor on carbon nanotubes surfaces that resulted in formation of shell/core type ceramic SiOC-CNT architecture. Li-ion battery anode (prepared at a loading of similar to 1.0 mg cm(-2)) showed stable charge capacity of 686 mA h g(-1) even after 40 cycles. The average Coulombic efficiency (excluding the first cycle loss) was 99.6%. Further, the post electrochemical imaging of the dissembled cells showed no apparent damage to the anode surface, highlighting improved chemical and mechanical stability of these composites. A similar trend was observed in the rate capability tests, where the SiOC-CNT anode (with 5 wt % loading in TTCS) again showed stable performance, completely recovering the first cycle capacity of similar to 750 mA h g(-1) when the current density was brought back to SO mA g(-1) after cycling at higher current densities.