Enhanced interface protection of freestanding Si anodes in carbon fiber nanotube by introducing MoO3 buffering layers

Developing Silicon (Si) based flexible and freestanding anodes is crucial for future wearable lithium ion batteries (LIBs) with satisfiable energy density. Improving the poor conductivity and unstable structure of Si in the lithiation/delithiation processes is a significantly important challenge. In this work, we synthesized flexible composites MoO3/Si@CFNT, in which MoO3 as a decorative layer and Si nanoparticles are well encapsulated into carbon fiber nanotube (CFNT). As freestanding lithium ion battery (LIB) anodes, the as-synthesized MoO3/Si@CFNT composites exhibit excellent Li+ storage performance for both half-cell and full-cell (610 mAh g−1 @200 cycles at 0.2 A g−1 for half-cell and 159 mAh g−1 @100 cycles at 0.5 A g−1, with a capacity retention rate of 85.9% and almost 99% coulombic efficiency for full-cell). We demonstrated that CFNT reserves sufficient space for the volume change of Si caused by lithiation, meanwhile, the enhanced interface protection of freestanding Si anodes in CFNT was achieved by introducing MoO3 buffering layers. Furthermore, we revealed the ion/electron transport kinetics of MoO3/Si@CFNT flexible electrode by GITT and ex-situ EIS measurements. This work offers a good example and inspiring insights into the design of many other Si based flexible anodes.