Vanadium-doped Co0.85Se nanowire arrays with high areal capacitance for hybrid supercapacitor electrodes

The continuous exploration of advanced electrode materials is noteworthy to reform next-generation high-performance energy storage technology toward a green future. Benefiting from their abundant redox centers and electrochemically active sites, transition metal selenides (TMSs) have emerged as promising electrode materials for supercapacitors, which present massive potential in bridging a gap between the high power density and enhanced energy density. In this paper, we provide a two-step approach for constructing vanadium-doped Co0.85Se (V-doped Co0.85Se) nanowires on nickel foam that have outstanding electrochemical performance. In the three-electrode system, the areal specific capacity of the V-doped Co0.85Se was found as high as 1.28 mAh cm-2 (127.78 mAh g-1) at 5 mA cm -2, which is 1.97 times of that of the Co0.85Se electrode. The assembled quasi-solid-state hybrid supercapacitor also exhibits impressive electrochemical performance, possessing an energy density of 5.30 mWh cm-3 at a power density of 51.15 mW cm-3, and an excellent cycling stability (with capacitance retention of 84.2% after 5000 cycles). The enhanced electrochemical performance of the V-doped Co0.85Se is caused by a unique nanowire-like morphology with high specific surface area, and low charge transfer resistance and ion diffusion resistance. This work provides a feasible strategy for combining metallic element vanadium with selenide electrodes.