Reduced-graphene-oxide-modified self-supported NiSe2 nanospheres on nickel foam as a battery-type electrode material for high-efficiency supercapacitors

Self-supported NiSe 2 nanospheres have been successfully synthesized by a one-step microwave method, and then coated with a layer of reduced graphene oxide (rGO) by a simple dip-coating method. Due to the excellent conductivity and high surface area of rGO, as a battery-type electrode material, the as-prepared NiSe 2 @rGO composite exhibited an excellent specific capacity of 224.75 mAh g −1 at 1 A g −1 , far exceeding that of the NiSe 2 nanospheres (72.5 mAh g −1 at 1 A g −1 ). NiSe 2 @rGO showed good cycling performance, with 78.13% retention of its initial capacity after 5000 cycles. Furthermore, an NiSe 2 @rGO//activated carbon (AC) asymmetric supercapacitor (ASC) showed a high energy density (E) of 25.85 Wh kg −1 at a power density (P) of 730 W kg −1 . The NiSe 2 @rGO//AC showed good capacity retention, maintaining 85.45% of the original value after 10000 cycles.