High‐performance all‐solid‐state supercapacitor with binder‐free binary transition metal sulfide array as cathode

Summary Transition metal sulfides show excellent performance in an aqueous supercapacitor. However, all‐solid‐state supercapacitors are attracting more and more interest because of thinner, lighter, and more flexible. Binary sulfides Ni 3 Co 6 S 8 nanowire arrays (NCS) are directly grown on a nitrogen‐doped carbon foam (NCF) through hydrothermal reaction, which is applied as a binder‐free electrode for all‐solid‐state supercapacitor. The unique needlelike structure assembled by nanosheet effectively increases the utilization efficiency of active materials and promotes electrochemical performance. The NCS‐NCF electrode shows promising application potential for wearable electronic devices due to the flexibility of NCF. A high‐specific capacitance of 243 mAh g −1 is delivered by NCS‐NCF electrode, which also exhibits good rate behavior along with outstanding cycle stability. The NCS‐NCF electrode (positive electrode) and NCF electrode (negative electrode) are employed to assemble asymmetric all‐solid‐state supercapacitor. When the high power density is 675 W kg −1 , the energy density of supercapacitor reaches the maximum of 28.31 Wh kg −1 . The specific capacitance of supercapacitors could maintain 84%, after 10 000 cycles of galvanostatic charge and discharge under 4 A g −1 , indicating the potential application of NCS‐NCF electrode as an excellent supercapacitor electrode material in flexible, wearable energy storage systems.