Designing NiS/CoS decorated NiCo2S4 nanoflakes towards high performance binder-free supercapacitors

Given their excellent cycling stability, high-power density, and simple structures, supercapacitors have attracted great interest as promising energy storage devices for various systems ranging from small wearable electronic devices to large-scale renewable energy grids. However, it is still a challenge to develop electrodes of supercapacitors with high energy density to meet the requirement of these practical applications. Herein we report a procedure involving electrochemical deposition, hydrothermal conversion, and sulfurization to fabricate a binder-free NiCo2S4@NiS/CoS electrode with excellent supercapacitive performance. The NiCo2S4@NiS/CoS consists of NiCo2S4 nanoflakes, on which CoS and NiS nanoparticles are anchored. Because of the high specific capacitance of NiS and CoS nanoparticles and the good electronic contact between the sulfide components and the conductive substrate, the NiCo2S4@NiS/CoS hybrid material exhibits a high specific capacitance (2551 F g − 1 (354.3 mAh g − 1) at 2 A g − 1), excellent high-rate capability, and good cycling performance. The asymmetric supercapacitor assembled with the NiCo2S4@NiS/CoS cathode and a Fe3O4 nanosheet anode demonstrates high power and energy densities, suggesting that the NiCo2S4@NiS/CoS is suitable for use as the binder-free cathode material of supercapacitors.