High performance flexible energy storage device based on copper foam supported NiMoO4 nanosheets-CNTs-CuO nanowires composites with core–shell holey nanostructure

Abstract Because of the intensified electrochemical activities, mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes. Nevertheless, low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance. In order to offset the defect, a novel copper (Cu) foam-supported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array (NiMoO4 NSs-CNTs-CuO NWAs/Cu foam) flexible electrode is constructed. The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area, which can provide a large number of active sites for redox reactions. Besides, the CNTs networks supply improved conductivity, which can hasten electron transport. Through this simple and efficient design method, the spatial distribution of each component in the flexible electrode is more orderly, short and fast electron transport path with low intrinsic resistance. As a result, the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent energy storage performance with high specific areal capacitance of 23.40 F cm-2 at a current density of 2 mA cm-2, which outperforms most of the flexible electrodes reported recently. The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm-3 and a power density up to 0.4 W cm-3 under a working voltage window of 1.7 V. In addition, outstanding flexibility of up to 100° bend and good cycling stability with the capacitance retention of 82.53% after 10,000 cycles can be obtained.