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

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 Ni3Co6S8 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.