Ultrahigh volumetric capacitance and cycle stability via structure design and synergistic action between CoMoO4 nanosheets and 3D porous Ni-Co film

Abstract

The rational design of the composites constituted by active materials and self-supported conductive current collectors has been turned out to be an effective way to achieve excellent electrochemical performance of supercapacitors. In this work, the 3D network-like continuous porous Ni-Co film (3DNC) with high conductivity and controllable porous structure was obtained through simple de-alloying and annealing processes, and then ultrathin CoMoO4 nanosheets were homogeneously grown onto skeleton of 3DNC film by hydrothermal and low-temperature annealing processes. The 3DNC film exhibits considerable electrochemical performance, whose controllable pore structure insures optimized mass loading of CoMoO4 and maximized space utilization of integrated electrode. The highly interconnected porous channels among the ultrathin CoMoO4 nanosheets provide high ion-accessible effective surface area and fast ion diffusion path, which significantly increases the reaction kinetics of the CoMoO4 nanosheets. Such outstanding structural advantages and the synergistic effect between CoMoO4 nanosheets and 3DNC film result in desired electrochemical performance with an extremely high volumetric capacitance of 2601.3 F cm−3 (325.2 mAh cm−3), excellent rate performance and superior cycle stability up to 20,000 cycles. The impressive results open an avenue toward the rational design of free-standing composites with high-performance electrochemical performance through both structure design and the synergistic action between active materials and conductive current collectors.