Energy-dense wire-like supercapacitors based on scalable three-dimensional porous metal-graphene oxide skeleton electrodes

Abstract

Synthesis of three-dimensional (3D) porous current collectors is a pioneering strategy to improve the energy density and power density of wire-like supercapacitors. The strategy is further promoted in this work by synthesizing multi-scale 3D porous current collectors with secondary nanostructured metals on the surface. Through the proposed nano-‘reinforced concrete’ mechanism at the micron scale, Ni and graphene oxide (GO) are synergistically co-deposited on the surface of Ni wires, forming a macroporous skeleton with tunable thickness. Cu is further synthesized on the Ni-GO macroporous skeleton through a structure catalyzed electroless deposition. The resultant Cu@Ni-GO exhibits a 3D porous structure covered with secondary Cu nanosheets. Cu@Ni-GO and Ni-GO are used as current collectors for negative and positive electrodes, respectively, while active materials are in situ formed on each electrode through surface oxidation. The negative electrodes and positive electrodes exhibit excellent electrochemical performance with volumetric capacitances of 510.7 F cm⁻³ and 235.2 F cm⁻³, respectively. Asymmetric wire-like supercapacitors are also developed, showing a very high energy density of 30.2 mW h cm⁻³. The application potential of wire-like supercapacitors is demonstrated by powering a LED array and an electronic watch.