Construction of Cu-Doped Ni–Co-Based Electrodes for High-Performance Supercapacitor Applications

Element doping is an effective method to improve the specific capacity and ion transfer rate of binary metal compounds. In this study, Cu-doped Ni–Co-based electrode materials were synthesized by a hydrothermal process and subsequent annealing treatment. The experimental results show that the nanocone-like Cu-doped Ni–Co carbonate hydroxides (Ni–Co–Cu CH) with high mass loading and the Cu-doped Ni–Co oxide (Ni–Co–Cu oxide) electrode with abundant oxygen defects achieve high area specific capacities of 6.31 F/cm2 and 6.54 F/cm2 at 3 A/g, respectively, which are about 2.5 times larger than the area specific capacity of the undoped nanorod-like Ni–Co precursor electrode (2.51 F/cm2 at 3 A/g). The quasi-solid-state asymmetric supercapacitors (ASCs) Ni–Co–Cu CH//AC and Ni–Co–Cu oxide//AC also achieved high energy densities of 36.9 Wh/kg and 42.1 Wh/kg at power densities of 374.2 W/kg and 374.9 W/kg, respectively, which can light up a red light emitting didode for ∼8 min and ∼11 min, respectively. Cu doping not only changes the morphology and defect state of a Ni–Co bimetallic compound electrode but also improves its electricity conduction and electrochemical performance. This strategy has important reference significance for the preparation of excellent performance supercapacitor energy storage materials in the future.