The Synthesis of NiCo(2)O(4)–MnO(2) Core–Shell Nanowires by Electrodeposition and Its Supercapacitive Properties

Hierarchical composite films grown on current collectors are popularly reported to be directly used as electrodes for supercapacitors. Highly dense and conductive NiCo(2)O(4) nanowires are ideal backbones to support guest materials. In this work, low crystalline MnO(2) nanoflakes are electrodeposited onto the surface of NiCo(2)O(4) nanowire films pre-coated on nickel foam. Each building block in the composite films is a NiCo(2)O(4)–MnO(2) core–shell nanowire on conductive nickel foam. Due to the co-presence of MnO(2) and NiCo(2)O(4), the MnO(2)@NiCo(2)O(4)@Ni electrode exhibits higher specific capacitance and larger working voltage than the NiCo(2)O(4)@Ni electrode. It can have a high specific capacitance of 1186 F·g(−1) at 1 A·g(−1). When the core–shell NiCo(2)O(4)–MnO(2) composite and activated carbon are assembled as a hybrid capacitor, it has the highest energy density of 29.6 Wh·kg(−1) at a power density of 425 W·kg(−1) with an operating voltage of 1.7 V. This work shows readers an easy method to synthesize composite films for energy storage.