Effect of Co2+ Doping on Electrochemical Properties of Nickel Metal Tungstate (NiWO4) Positive Material

Abstract

Currently, transition metal tungstates are emerging as electroactive materials for supercapacitors due to their excellent electrical conductivity and electrochemical properties. Small amounts of transition metal ions doping can affect the physical and electrical properties of transition metal tungstates. In this study, Co ion-doped NiWO₄ amorphous composites (CNWO) were synthesized using a simple and effective hydrothermal method and utilized as the cathode material for supercapacitors. The structure and electrochemical properties of NiWO₄ and CNWO composites were investigated using various testing techniques. Specifically, when the cobalt ion doping amount is 10%, the corresponding CNWO-10 electrode material exhibits a specific capacitance of 804 F g⁻¹ at 1 A g⁻¹, and at a current density of 10 A g⁻¹, the capacitance retention rate reaches 66.7%, demonstrating good rate performance. Additionally, an asymmetric supercapacitor device was constructed using CNWO-10 and activated carbon (AC) as positive and negative materials, respectively. Which could cycle reversibly under a potential window of 2.1 V. The device demonstrates a maximum specific capacitance of 76.5 F g⁻¹ at 0.5 A g⁻¹, and a high energy density of 47 Wh kg⁻¹ at a power density of 527 W kg⁻¹. Furthermore, 96% capacitance cycling stability is maintained after 5500 cycles at a trapezoidal current density. Moreover, the electrical conductivities of NiWO₄ and CNWO-10 samples are 9.01 × 10^–8 S m⁻¹ and 8.93 × 10^–6 S m⁻¹, attributed to the Co ion-doping that can reduce the gap width of the forbidden band to enhance conductivity. These results suggest that CNWO composites can serve as promising high-capacity electrode materials for high-performance supercapacitors in alkaline electrolytes.

Graphical Abstract