The Synthesis of NiCo2O4–MnO2 Core–Shell Nanowires by Electrodeposition and Its Supercapacitive Properties

Abstract

Hierarchical composite films grown on current collectors are popularly reported to be directly used as electrodes for supercapacitors. Highly dense and conductive NiCo2O4 nanowires are ideal backbones to support guest materials. In this work, low crystalline MnO2 nanoflakes are electrodeposited onto the surface of NiCo2O4 nanowire films pre-coated on nickel foam. Each building block in the composite films is a NiCo2O4–MnO2 core–shell nanowire on conductive nickel foam. Due to the co-presence of MnO2 and NiCo2O4, the MnO2@NiCo2O4@Ni electrode exhibits higher specific capacitance and larger working voltage than the NiCo2O4@Ni electrode. It can have a high specific capacitance of 1186 F·g−1 at 1 A·g−1. When the core–shell NiCo2O4–MnO2 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.