Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium‐Ion Batteries

Abstract Potassium‐ion batteries (PIBs) are regarded as promising candidates in next‐generation energy storage technology; however, the electrode materials in PIBs are usually restricted by the shortcomings of large volume expansion and poor cycling stability stemming from a high resistance towards diffusion and insertion of large‐sized K ions. In this study, BiSbS x nanocrystals are rationally integrated with sulfurized polyacrylonitrile (SPAN) fibres through electrospinning technology with an annealing process. Such a unique structure, in which BiSbS x nanocrystals are embedded inside the SPAN fibre, affords multiple binding sites and a short diffusion length for K + to realize fast kinetics. In addition, the molecular structure of SPAN features robust chemical interactions for stationary diffluent discharge products. Thus, the electrode demonstrates a superior potassium storage performance with an excellent reversible capacity of 790 mAh g −1 (at 0.1 A g −1 after 50 cycles) and 472 mAh g −1 (at 1 A g −1 after 2000 cycles). It's one of the best performances for metal dichalcogenides anodes for PIBs to date. The unusual performance of the BiSbS x @SPAN composite is attributed to the synergistic effects of the judicious nanostructure engineering of BiSbS x nanocrystals as well as the chemical interaction and confinement of SPAN fibers.