Improving cycling stability of Bi-encapsulated carbon fibers for lithium/sodium-ion batteries by Fe2O3 pinning

Abstract Bi draws increasing attention as anode materials for lithium-ion batteries and sodium-ion batteries due to its unique layered crystal structure, which is in favor of achieving fast ionic diffusion kinetics during cycling. However, the dramatic volume expansion upon lithiation/sodiation and an insufficient theoretical capacity of Bi greatly hinder its practical application. Herein, we report the Fe2O3 nanoparticle-pinning Bi-encapsulated carbon fiber composites through the electrospinning technique. The introduction of Fe2O3 nanoparticles can prevent the growth and aggregation of Bi nanoparticles during synthetic and cycling processes, respectively. Fe2O3 with high specific capacity also contributes to the specific capacity of the composites. Consequently, the as-prepared Bi-Fe2O3/carbon fiber composite exhibit outstanding long-term stability, which delivers reversible capacities 504 and 175 mA h/g after 1000 cycles at 1 A/g for lithium-ion and sodium-ion batteries, respectively.