Candied-Haws-like Architecture Consisting of FeS₂@C Core–Shell Particles for Efficient Potassium Storage

The major challenge faced by potassium-ion batteries (PIBs) lies in the shortage of high-performance and cost-effective electrode materials. Herein, we demonstrate a candied-haws structure containing FeS2@C core–shell units as an advanced anode for PIBs. This special material is featured with thin amorphous carbon as the shell, which can confine the active iron disulfide core during the (de)potassiation processes to maintain the structural integrity. Moreover, consecutive carbon nanofibers interconnect with each other to generate a high-performance three-dimensional conductive framework, contributing to attaining enhanced reaction kinetics. Consequently, when measured as an anode material for PIBs, the FeS2@C nanocomposite achieves a large reversible capacity of 292 mAh g–1 at 0.1 A g–1 after 300 cycles and a high-rate capacity of 183 mAh g–1 at 2 A g–1.