γ-Fe2O3 nanoparticles embedded in porous carbon fibers as binder-free anodes for high-performance lithium and sodium ion batteries

A facile strategy of electrospinning has been employed to fabricate freestanding anodes of γ-Fe2O3/porous carbon fibers (γ-Fe2O3/PCF) for both lithium and sodium ion batteries, in which γ-Fe2O3 nanoparticles ranging from 50 to 150 nm were in-situ formed and embedded in the porous carbon fibers. The thus obtained composite delivers highly reversible discharge capacities of 980 mAh g−1 in lithium ion batteries and 291 mAh g−1 in sodium ion batteries, corresponding to high capacity retentions of 97 and 78%, respectively. The superior electrochemical performance of the binder-free anodes can be attributed to the unique composite structure with γ-Fe2O3 nanoparticles homogenously dispersed in the porous carbon fibers, which should help alleviate the volumetric fluctuation, promote the wettability of electrolyte, and enhance the electronic conductivity, demonstrating a promising candidate as the flexible anode material for high-performance energy storage devices.