Advanced Asymmetric Supercapacitors Based on Ni(OH) 2 /Graphene and Porous Graphene Electrodes with High Energy Density

Abstract Hierarchical flowerlike nickel hydroxide decorated on graphene sheets has been prepared by a facile and cost‐effective microwave‐assisted method. In order to achieve high energy and power densities, a high‐voltage asymmetric supercapacitor is successfully fabricated using Ni(OH) 2 /graphene and porous graphene as the positive and negative electrodes, respectively. Because of their unique structure, both of these materials exhibit excellent electrochemical performances. The optimized asymmetric supercapacitor could be cycled reversibly in the high‐voltage region of 0–1.6 V and displays intriguing performances with a maximum specific capacitance of 218.4 F g −1 and high energy density of 77.8 Wh kg −1 .…