Binder-free CoMn2O4/carbon nanotubes composite electrodes for high-performance asymmetric supercapacitor

This study presents the fabrication of supercapacitor electrodes composed of CoMn2O4 (CMO) nanosheets coated onto carbon nanotubes which are grown on a stainless-steel mesh (SSM). The synthesis includes chemical vapor deposition of carbon nanotubes (CNTs) on the SSM followed by annealing at 450 °C in air for 2 h in order to generate defects for further electrodeposition of CMO nanosheets. The electrodeposited CMO exhibits excellent pseudocapacitive performance owing to high oxidation potential of cobalt as well as the fast electron transportation ability of manganese. By controlling the deposition time of CMO, favorable morphology and excellent capacitance can be achieved. Furthermore, the direct growth of CMO on CNTs/SSM prevents the use of binders or additives and avoids undesired resistances. The binder-free CMO/CNT electrode exhibits a superior specific capacitance of 732 F/g at a scan rate of 2 mV/s. Furthermore, an asymmetric supercapacitor was fabricated by paring the CMO/CNT electrode with activated carbon as an anode. The asymmetric supercapacitor exhibits an energy density of 47.39 W/kg with a power density of 400 Wh/kg together with good stability of 77% capacitance retention after 5000 cycles, which suggest that the composite electrode is of great significance for practical energy storage devices.