Controlled synthesis of NiSe-Ni0.85Se nanocomposites for high-performance hybrid supercapacitors

Constructing nanostructured multiphase composite is an effective way for optimizing the performance of electrode materials. Here we report our findings in design and fabrication of a high-performance electrode material composed of two-phase nickel selenide (NiSe-Ni0.85Se) nanoparticles, which exhibits a high specific capacity of 669 C g−1 at 1 A g−1 and 460 C g−1 at 20 A g−1, indicating its good rate capability (~69%). Moreover, a hybrid supercapacitor composed of NiSe-Ni0.85Se positive electrode and reduced graphene oxide (rGO) negative electrode delivers a specific capacitance of 101 F g−1, high energy of 41 Wh kg−1 and good cycling stability with ~80% capacity retention after 5000 cycles at 10 A g−1. These findings provide an important insight into rational design of nanostructured multiphase nickel selenide materials for energy storage systems.