Three‐Dimensional Hierarchical NiCo 2 O 4 Nanosheets/Carbon Nanotubes/Carbon Cloth as a Flexible Electrode Material for Electrochemical Capacitors

In order to achieve superior energy storage performances, the design of electrode materials with complex heterostructure has attracted intensive attention. In this study, the NiCo 2 O 4 /carbon nanotubes/carbon cloth (NiCo 2 O 4 /CNTs/CC) composite electrode material with a three‐dimensional (3D) and hierarchically porous structure was prepared by using ZnO‐assisted template method and followed the electrodeposition and thermal decomposition processes. The vertical carbon nanotube arrays on carbon cloth formed a 3D conductive network, which facilitates to achieve fast electron transportation. After further growing ultrathin NiCo 2 O 4 nanosheets on the surface of carbon nanotubes (CNTs), the resultant NiCo 2 O 4 /CNTs/CC electrode material exhibited remarkable electrochemical performances. It showed a maximum specific capacitance of 1518 F/g at a scan rate of 5 mV/s in 2 mol/L KOH aqueous solution and excellent stability under the conditions of long term cycling, mechanical bending and twisting conditions. The solid‐state symmetric electrochemical capacitor assembled by the NiCo 2 O 4 /CNTs/CC electrode material delivered an energy density of 13.0 Wh/kg at the power density of 1276 W/kg.