Bismuth nanoparticles embedded in carbon fibers as flexible and free-standing anodes for efficient sodium ion...

Metallic bismuth is a promising anode electrode material for sodium ion batteries due to its high theoretical specific capacity. However, the formation of Na₃Bi during the reaction process brings about significant volume changes and structural collapse of the electrode, resulting in the destruction of structures and a decrease in the cycling stability of sodium ion batteries. In this study, bismuth nanoparticles embedded in carbon fibers (Bi/CF) through a facile approach of electrospinning and calcination. Bi nanoparticles with diameters of approximately 20 nm were homogeneously dispersed in the carbon fibers, as confirmed by relevant morphological and structural features. The carbon fiber substrate can serve as a flexible and free-standing electrode, forming a conductive network to accelerate electron transport and ion diffusion. In light of this, Bi/CF anodes exhibit a high reversible capacity (376.6 mA h g^-1 at 0.1 A g^-1) and long-term cycle stability (only attenuates 0.12% in each cycle after 2000 times). This work provides a convenient and effective strategy for the synthesis of flexible and free-standing anodes for high-performance sodium ion batteries.