Controllable one-pot synthesis of emerging β-Cu2Se nanowire freely standing on nickel foam for high electrochemical energy storage performance

Transition metal selenide has stimulated much research interest in energy storage and conversion, due to its excellent electrical conductivity. β-Cu2Se with special crystal structure is considered as super-ionic conductor, of which the diffusion coefficient is as large as a liquid. The fast ions and electrons conductor β-Cu2Se with uniformly dense nanowire crossing with each other directly on nickel foam is prepared via simple one-step solvothermal grow method for 4 h, avoiding conductive agent and binder. The feature much benefitting for electrons and ions transfer enable the β-Cu2Se-4h electrode delivers specific capacity as high as 182.4 mA h g−1 at current density of 2 mA cm−2, which is still 105.6 mA h g−1 even at high current density of 50 mA cm−2, and excellent cycling stability of 85% after repetitively charge-discharge 10,000 times. The fabricated asymmetric supercapacitor (β-Cu2Se-4h//AC) achieves maximum energy and power density is 48 Wh kg−1 and 5500 W kg−1.