UV-ozone contributions towards facile self-assembly and high performance of silicon-carbon fiber materials as lithium-ion battery anodes.

Si-carbon composites have been considered as next generation lithium-ion battery anodes, with a view to sufficiently exerting the respective superiorities of high specific capacity of Si as well as excellent mechanical flexibility and electrical conductivity of carbon. However, direct blending of carbon with Si cannot obtain a synergy composite, resulting in inferior cycle properties during charge-discharge due to huge volume changes and deficient electron-conducting channels from the unavoidably aggregated Si. Herein, the composition of carbon fibers (CNFs) with Si nanoparticles (SiNPs) has been performed through UV-ozone surface modification followed by electrostatic self-assembly. It is found that solvent-free UV-ozone exposure of CNFs for 20 min successfully introduces carboxylic groups, as conventional acid treatment for 12 h. Besides UV-ozone surface modification provides an efficient and scalable route, the distribution and functionalization of CNFs can be also modified to effectively combine with amino-functionalized SiNPs. As a result, such Si-CNF composites containing 70.0 wt% SiNPs are able to exhibit excellent cycle performance with high coulombic efficiency of 74.8% at the 1st cycle and high specific discharge capacity of 1063 mAh g-1 at the 400th cycle.