High mass loading flower-like MnO(2) on NiCo(2)O(4) deposited graphene/nickel foam as high-performance electrodes for asymmetric supercapacitors

The implementation of high mass loading MnO(2) on electrochemical electrodes of supercapacitors is currently challenging due to the poor electrical conductivity and elongated electron/ion transport distance. In this paper, a NiCo(2)O(4)/MnO(2) heterostructure was built on the surface of three-dimensional graphene/nickel foam (GNF) by a hydrothermal method. The petal structured NiCo(2)O(4) loaded on graphene played a wonderful role as a supporting framework, which provided more space for the growth of high mass loading MnO(2) microflowers, thereby increasing the utilization rate of the active material MnO(2). The GNF@NiCo(2)O(4)/MnO(2) composite was used as a positive electrode and achieved a high areal capacitance of 1630.5 mF cm(−2) at 2 mA cm(−2) in the neutral Na(2)SO(4) solution. The asymmetric supercapacitor assembled with the GNF@NiCo(2)O(4)/MnO(2) positive electrode and activated carbon negative electrode possessed a wide voltage window (2.1 V) and splendid energy density (45.9 Wh kg(−1)), which was attributed to the satisfactory electroactive area, low resistance, quick mass diffusion and ion transport caused by high mass loading MnO(2).