High performance hybrid supercapacitors assembled with multi-cavity nickel cobalt sulfide hollow microspheres as cathode and porous typha-derived carbon as anode

Unique hollow structures hold bright promise in the field of energy storage applications, but it is still challenging to synthesize bimetallic sulfide composites with complex hollow structures. In the present work, a NixCo1-xS2/ NiCo2S4 composite with multi cavity hollow sphere structure is prepared by a simple liquid-phase reaction and solvothermal sulfurization and used as a supercapacitor positive electrode material. Benefiting from the welldesigned unique structure and synergy between the nickel and cobalt elements, the composite exhibits excellent electrochemistry with a specific capacity of 797 C g (-1) at 1 A g (-1) and possesses good rate capability (78.8 % retention at 20 A g (-1)). In addition, Typha-derived carbon is prepared by calcination using discarded biomass Typha. And, a hybrid supercapacitor device is assembled by using NixCo(1- x)S(2)/NiCo2S4 and Typha-derived carbon as cathode and anode. The device exhibits a high energy density of 82.7 Wh kg (-1) at 513.5 W kg (-1) and possesses superior long-term cycling capacity (84.6 % after 10,000 cycles), indicating the great application potential of the composites in the field of supercapacitors. More importantly, the unique structural design and facile operation methods provide new ideas and broad prospects for the synthesis of complex metal sulfide materials in the energy storage field later.