Hierarchically urchin-like hollow NiCoS prepared by a facile template-free method for high-performance supercapacitors.

Hollow structures draw much attention for high energy density supercapacitors due to their large hollow cavities, high specific surface area, and low interfacial contact resistance. However, constructing hierarchical hollow structures remains a challenge. Herein, we reported a facile template-free method for a novel urchin-like hollow nickel cobalt sulfide (NiCoS). The hollow interior and urchin exterior remarkably improved the specific capacitance and accommodated structural collapse caused by electrochemical reactions. Owing to these features, the urchin-like hollow NiCoS spheres exhibited an impressive capacitance of 1398F g at 1 A g and maintained 1110F g with a large current density of 10 A g. The hybrid supercapacitor fabricated by NiCoS and active carbon possesses an energy density of 39.3 Wh kg at a power density of 749.6 W kg and an outstanding cycling stability of 74.4% retention after 5000 cycles. Our work presents a facile method of constructing a hollow structure of binary sulfide materials and also makes progress on highly efficient supercapacitors.