Boosting the capacitive property of cobalt sulfide through interface engineering for high-performance supercapacitors

Metal sulfide arrays can store electrochemical energy owing to their high theoretical capacity, shortened diffusion routes, and rich electrochemical sites. However, their sluggish redox reaction has limited further application in high power density devices. Herein, a novel hybrid and hierarchical nanostructure with a thin layer of NiO deposited on the surface of walnut-like CoS particles is constructed and the NiO layer can greatly improve the capacitive properties of cobalt sulfide. In this hybrid nanostructure, the amount of NiO on the surface of CoS is precisely tuned to boost the electrochemical performance. Consequently, NiO/CoS exhibits a higher capacitance/capacity of 1749 F g−1/243.9 mAh g−1 fueled by the excellent electrical conductivity and appropriate surface structures. When assembled into a hybrid supercapacitor, the NiO/CoS//AC devices deliver a maximum capacitance of 60 C g−1 at 1.0 A g−1. Energy density reaches 45 Wh kg−1 when the power density is at 750 W kg−1. Additionally, the fabricated supercapacitor has good cycling stability with a capacity retention rate of 74% after 5000 cycles.