In Situ Growth of 3D Nano‐array Ni 0.85 Se/NF Structure Supercapattery Electrode with Excellent Cyclic Stability and Superior Energy Density

The growth of three‐dimensional(3D) nano‐array Ni 0.85 Se structure on Ni foam (Ni 0.85 Se/NF) in situ by hydrothermal treatment using Na 2 SeO 3 ⋅5H 2 O as Se source is presented in this article. Moreover, when fabricated as binder‐free supercapattery electrode, the 3D nano‐array Ni 0.85 Se/NF structure demonstrates an excellent specific capacitance of 1344 and 686.50 F⋅g −1 at current densities of 0.5 and 5 A⋅g −1 , which was calculated by 4 mg active mass of Ni 0.85 Se. Impressively, the areal capacitance of 5.38 and 2.75 F⋅cm −2 can be got at the current densities of 2 and 20 mA⋅cm −2 . Furthermore, the supercapattery electrode exhibits a superior cyclic stability with 70.1 % capacity retention after 5000 cycles, which is notable for a selenide based supercapacitor. When assembled into Ni0.85Se//AC asymmetric supercapacitor, the operating voltage was expanded to 1.6 V, a good specific capacitance of 184.70 C⋅g −1 at 0.5 A⋅g −1 and remains 35.33 C⋅g −1 at 4 A⋅g −1 is achieved. The supercapattery electrode demonstrates an outstanding rate performance as a coin type asymmetric device, obtaining a great energy density of 38.48 Wh⋅kg −1 at the power density of 375 W⋅kg −1 . The aforementioned results suggested that the 3D nano‐array Ni 0.85 Se structure may a potential electrode for next generation supercapacitors.