High-entropy alloy FeNiCuMnSbBi nanofibers as anode for high-performance potassium-ion capacitors

Abstract

Potassium-ion capacitors (PICs) have recently gotten significant interest due to their price and excellent power/energy density. Nonetheless, the advancement of PICs is hindered by a limited cycle life, which arises from the ion intercalation and deintercalation processes. Herein, a high-entropy alloy of FeNiCuMnSbBi combined with carbon-nanofibers (HEA₆/CNFs) is reported as novel electrode materials for potassium-ion storage, which exhibit favorable electrochemical properties. Experiments and characterization proved that excellent electrochemical performance of HEA₆/CNFs is the result of combined high-entropy effect and carbon-nanofibers. The active materials (Sb, Bi) participate in redox reaction, and transition metal elements (Fe, Ni, Cu, Mn) and carbon-nanofiber jointly construct the conductive skeleton and minimize the increase in volume to enhance the structural stability of material during the reaction process. Integration of activated carbon cathode and HEA₆/CNFs anode in PICs demonstrated high-power density of 10,000 W kg⁻¹, an impressive energy density of 109 Wh kg⁻¹ and an ultralong cycle performance with 83.6% capacity retention after 20,000 cycles at 5.0 A g⁻¹. This research paves the way for the application of high entropy materials in potassium-ion capacitors.