Construction of 3D self-supported electrodes of amorphous Ni(OH)2 with rationally nanostructued architecture for supercapacitor applications

Abstract

"Amorphous Ni(OH)2 coating on nanostructured nickel scaffolds with rational archietcture have been successfully fabricated by a facile process of templated-directed electrodeppsition and surface oxidation treatment. Nitrocellulose membrane with interconnected fibers and fiber diameter of a few hundred nanometers was used to fabricate nanoprpous nickel (NPN) at low cost. The as-prepared NPN has interconnected pore channels with pore diameter of a few hundred nanometers providing enough inner space for the formation of Ni(OH)2 nanosheets and short pathways for fast diffusion of electrolyte ions. Upright self-supported nickel nanowire array (USNWA) and self-supported nickel nanowire array (INWA) were fabricated with porous polycarbonate template and porous polyester template, respectively. Both of USNWA and INWA can be used as miniature conductive scaffolds ensuring excellent electrical/ionic conductivity, and providing large surface area. The amorphous Ni(OH)2 nanosheets coating on the miniatuer nickel scaffold was converted from the metallic surface by oxidation treatment. The conversion of metallic surface to amorphous Ni(OH)2 nanosheets creates a stable core-shell structure, a low contact resistane and guarantees a high utilization of Ni(OH)2. Because of the material and architecture advantages, the Ni(OH)2@NPN/USNWA/INWA show enhanced electrochemical performance of ultrahigh specific capacities more than 3500 F g-1 at a current density of 5 A g-1, remarkable rate capability and excellent cycling stability. The asymmetric supercapacitor of Ni(OH)2@INWA//rGO delivers a high energy density of 53 Wh kg-1 at a power density of 395 W kg-1, and an energy density of 31 Wh kg-1 can be maintained at a power density of 4973 W kg-1. It also shows long-term stability with 91 % retention of the initial capacitance after 10000 cycles at a current density of 2 A g-1. The excellent electrochemical performance of Ni(OH)2@NPN/USNWA/INWA makes them promising for supercapacitor applications."