Flexible freestanding Fe2O3-SnOx-carbon nanofiber composites for Li ion battery anodes

We demonstrate electrospun ternary Fe2O3-SnOx-carbon nanofiber (CNF) composites as high-performance, flexible, and freestanding anodes for Li ion batteries (LIBs). In the ternary composites, the CNF matrix accommodates volume changes of Fe and Sn during lithiation and delithiation, while also providing short Li ion diffusion pathways, which ultimately enhances the capacity of the LIB. The concentrations of Fe and Sn were varied to find the optimal composition. Higher Sn content increased capacity at slow discharge rates, but decreased capacity at higher discharge rates. Increasing Fe to Sn ratio improved performance at high discharge rates. The Fe2O3-SnOx-CNF composite fabricated at a Fe:Sn weight ratio of 3:1 exhibited a reversible capacity value of 756 mAh·g−1 after 55 cycles. The materials and methods demonstrated here are unique in producing a flexible, free-standing mat with high gravimetric capacity using a simple and scalable production process.