Hierarchical NiS/N-doped carbon composite hollow spheres with excellent supercapacitor performance

Designing electrode materials with high specific capacitance is crucial for further improving the energy storage performance of supercapacitors. Nickel sulfide (NiS) nanosheets anchored on the surface of N-doped hollow carbon spheres (NiS/NHCS) were rationally designed and synthesized via a multistep transformation approach. Uniform nickel silicate nanosheets were first deposited on the surface of NHCSs, followed by chemical conversion into NiS nanosheets. The NiS/NHCS composite shows excellent electrochemical properties as an electrode material for supercapacitors. The NiS/NHCS electrode can deliver a high specific capacitance of 1150 F g(-1) at 1 A g(-1) and show outstanding cycling performance with a retention rate of 76% over 4000 cycles, which are much higher than those of pure NiS hollow spheres (NiS-HS) (400 F g(-1) and 63%, respectively). Moreover, a hybrid supercapacitor assembled with NiS/NHCS as the cathode and an activated carbon electrode as the anode delivers a high energy density of 38.3 W h kg(-1) at a power density of 160 W kg(-1) and has an excellent cycle performance with the retention rate of 96% after 5000 cycles. The exceptional electrochemical performance of the NiS/NHCS composite indicates its potential application in high-performance supercapacitors.