Mesoporous Carbon‐Coated Bismuth Nanorods as Anode for Potassium‐Ion Batteries

A new type of a mesoporous carbon‐coated bismuth (Bi@C) composite in the form of nanorods is fabricated and used as anode material in a potassium‐ion battery (KIB). The rod‐like Bi core is composed of nanoparticles and confined by a shell of amorphous carbon. The KIB with such Bi@C anode exhibits a high storage capacity of 425 mAh g −1 at 0.2 A g −1 . The mesoporous Bi@C, with a large surface area and an appropriate pore size is in close contact with the electrolyte and facilitates the diffusion of K + ions. The carbon shell soothes the mechanical stresses owing to the volumetric changes of the anode during charging and discharging of the battery, preventing the degradation of active material and delivering a cyclic stability of over 500 cycles. This superior performance demonstrates the importance of a structural design that can offer a new pathway to anode development in KIB as well as in other energy storage devices.