Impregnating ultrafine FeS2 nanoparticles within hierarchical carbon tubes for advanced potassium-ion batteries

Transition-metal sulfides (TMSs) with high theoretical capacity and economical suitability are attractive anode materials for potassium-ion batteries (PIBs). However, the inherent low conductivity, tardy K+ diffusion kinetics, and huge volume change of TMSs pose a lot of challenges, impeding their practical application in PIBs. Herein, a simple template-assisted vulcanization strategy is presented for impregnating ultrasmall FeS2 nanoparticles within flexible carbon nanowires wrapped with robust amorphous carbon tubes (denoted as FeS2-C@CTs), resolving the abovementioned issues and improving the electrochemical performance of PIBs. Specifically, such a crafted FeS2-C@CT-based anode delivers a high reversible capacity of 524 mA h g(-1) at 50 mA g(-1), an intriguing rate capability of 208 mA h g(-1) at 10 A g(-1), and a decent cycling stability of 167 mA h g(-1) at 10 A g(-1) after 1000 cycles. More importantly, a full cell (K0.6CoO2//FeS2-C@CTs) also delivers an enhanced potassium storage performance, showing a high rate capacity of 123 mA h g(-1) at 1 A g(-1) and a long cycle life with a capacity retention rate of 87.6% after 200 cycles.