Effect of cobalt doping on the enhanced energy storage performance of 2D vanadium diselenide: experimental and theoretical investigations.

Vanadium Diselenide (VSe 2 ) is a prominent candidate in the 2D transition metal dichalcogenides family for energy storage applications. Herein, we report the experimental and theoretical investigations on the effect of cobalt doping in 1T-VSe 2 . The energy storage performance in terms of specific capacitance, stability and energy and power density is studied. It is observed that 3% Co doped VSe 2 exhibits better energy storage performance as compared to other concentrations, with a specific capacitance of ∼193 F g -1 in a two-electrode symmetric configuration. First-principles Density Functional Theory based simulations support the experimental findings by suggesting an enhanced quantum capacitance value after the Co doping in the 1T-VSe 2 . By making use of the advantages of the specific electrode materials, a solid state asymmetric supercapacitor (SASC) is also assembled with MoS 2 as the negative electrode. The assembled Co-VSe 2 //MoS 2 SASC device shows excellent energy storage performance with a maximum energy density of 33.36 Wh kg -1 and a maximum power density of 5148 W kg -1 with a cyclic stability of 90% after 5000 galvano static charge discharge cycles.