▎ 摘　　要

Selenide, particularly transition-metal selenide, is gaining popularity for use as electrode materials in electrochemical capacitors, because they are low cost, highly conductive, earth abundant, and environmentally benign. Here, we fabricated (Ni,Cu) Se-2 nanowires on nickel foam (NF) with a facile one-pot hydrothermal method. Upon rational design and careful growth control, regular (Ni, Cu) Se-2 nanowires of several micrometers in length were grown, having an areal specific capacitance of 5.92 Fcm(-2) at a current density of 2 mAcm(-2). Afterwards, an asymmetric supercapacitor was assembled by selecting the (Ni, Cu) Se-2 nanowire/NF as the positive electrode, and reduced graphene oxide (RGO) as the negative electrode, delivering an ultrahigh energy density of 44.46 Whkg(-1) at a power density of 797.9 Wkg(-1), and when tested at an ultrahigh power density of 9796.7 Wkg(-1), an energy density of 6.53 Whkg(-1) can be still maintained, evidencing its potential applications. Besides its high energy density features, it is impressive to notice that the energy density still maintains 97.56% even after 4000-cycle fierce cycling at an ultrahigh current density of 50 mAcm(-2). To the best of our knowledge, it is the first-ever reported (Ni,Cu) Se-2- based supercapacitor/asymmetric supercapacitor. This work may arouse new interest for designing and growing transitionmetal selenide and/or metal selenide for large-scale, practical supercapacitor applications.