Construction of (Ni, Cu) Se2//Reduced Graphene Oxide for High Energy Density Asymmetric Supercapacitor

Abstract

AbstractSelenide, 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) Se2 nanowires on nickel foam (NF) with a facile one‐pot hydrothermal method. Upon rational design and careful growth control, regular (Ni, Cu) Se2 nanowires of several micrometers in length were grown, having an areal specific capacitance of 5.92 F cm−2 at a current density of 2 mA cm−2. Afterwards, an asymmetric supercapacitor was assembled by selecting the (Ni, Cu) Se2 nanowire/NF as the positive electrode, and reduced graphene oxide (RGO) as the negative electrode, delivering an ultrahigh energy density of 44.46 Wh kg−1 at a power density of 797.9 W kg−1, and when tested at an ultrahigh power density of 9796.7 W kg−1, an energy density of 6.53 Wh kg−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 mA cm−2. To the best of our knowledge, it is the first‐ever reported (Ni, Cu) Se2‐based supercapacitor/asymmetric supercapacitor. This work may arouse new interest for designing and growing transition‐metal selenide and/or metal selenide for large‐scale, practical supercapacitor applications.