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

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.