Designing positive electrodes based on 3D hierarchical CoMn2O4@NiMn-LDH nanoarray composites for high energy and power density supercapacitors

Abstract

Herein, a positive electrode based on three-dimensional (3D) hierarchical CoMn₂O₄@NiMn-LDH core–shell nanowire arrays was successfully prepared on Ni foam via hydrothermal and calcination methods. The skeleton of the CoMn₂O₄ nanowire arrays was in situ developed on Ni foam substrates, and hierarchical NiMn-LDH nanosheets were homogeneously overlapped on the surface of CoMn₂O₄ nanowires. Electrochemical measurements revealed that this electrode represented the faradaic process of battery-type charge storage and exhibited a high specific capacity of 313 mA h g⁻¹ (under 1 A g⁻¹). The corresponding hybrid supercapacitor device, which was assembled by a CoMn₂O₄@NiMn-LDH cathode and activated carbon anode, possessed a high energy density of 118.8 W h kg⁻¹ with a power density of 799.4 W kg⁻¹. With two devices connected in series, the output voltage could reach 3.2 V and successfully assisted a group of light-emitting diodes turning on. This study provides an efficient strategy to develop next-generation high-performance energy storage devices.