Synthesis of FeS/Fe2O3 hollow fibers derived from Fe-alginate fibers as anodes for high performance sodium-ion batteries

Search for anode materials for sodium ions batteries (SIBs) attracts researchers around the world because of their high-rate capability and excellent capacity. However, their stability needs to be improved. Thus, this work demonstrates a controllable method for the synthesis of one-dimensional (1D) hollow microfibers using "egg-box-structured" Fe-alginate fibers. The goal was to obtain an SIBs anode material with the optimal number of voids for efficient Na+ storage. An optimized micro and pore structures were designed to obtain the shortest Na+-diffusion distance. The novel FeS2/Fe2O3-HF composite was able to withstand volume expansion during charge/discharge processes and showed high specificity and rate capacity (483 mAh/g at 100 mA/g, 241 mAh/g at 2000 mA/g). The capacity retention of this cell was excellent: it maintained 245 mAh/g over four hundred 1000 mA/g cycles. Thus, FeS2/Fe2O3-HF composite is a very promising active anode material for SIBs.