The yolk-shell nanorod structure of NiSe@C electrodes boosting charge transfer and cyclability in high-performance supercapacitors.

Developing novel electrode materials with reasonable structures and ideal conductivity is of great significance for energy storage devices. In this work, NiSe@C yolk-shell nanorods are grown on nickel foam (NF) via a one-step selenization and carbonization process. The carbon shell not only improves the conductivity and charge transfer of electrodes, but also inhibits the dissociation of NiSe core during redox reactions, which is crucial to electrochemical performances of SCs. Owing to the yolk-shell nanorod structure, the NiSe@C electrode exhibits an outstanding specific capacitance of 1669.7F g at 1 A g. Moreover, an asymmetric supercapacitor (ASC) is successfully assembled using NiSe@C and active carbon (AC) electrodes as the anode and cathode respectively, which delivers remarkable energy-storage characteristics. Specifically, the NiSe@C//AC ASC shows a high energy density (31.0 Wh kg) at a power density (723.7 W kg), and stable cycling performance (97% capacitance retention after 9000 cycles). These results make the NiSe@C a promising electrode for SCs.