Maximizing Redox Charge Storage via Cation (V)–Anion (S) Dual Doping on Nickel Diselenide Nanodiscs for Hybrid Supercapacitors

Dual doping of the cation–anion in the layered nanomaterials can be an effective strategy to precisely address the chief electrochemical barriers in achieving maximum energy and power for supercapacitor materials. To reap the maximum benefits from the above approach, we synthesized vanadium and sulfur dual-doped nickel diselenide (V, S-NiSe2) nanodiscs on carbon cloth. The X-ray photoelectron spectroscopy results strongly suggested the key role of S as a second dopant in assisting V (with low electronegativity) to alter the electron density around Ni. This shift of electron density from V with the assistance of S facilitated maximum transfer of charge from Ni also promoting rapid redox reactions, which is supported by a 22% increment in b-value (0.62), 89% electro active sites, and 2.4 times swift diffusion of the OH– ions. In addition, V, S-NiSe2 nanodiscs also presented an excellent charge storage of 1464 F g–1@1 A g–1 and a good rate capability of 70% until 20 A g–1, exceeding those of NiSe2 and V-doped NiSe2. In relation, a hybrid supercapacitor cell is also fabricated by assembling the V, S-NiSe2 with an activated carbon electrode, presenting a remarkable energy density of 28.0 W h kg–1 at a power density of 714.7 W kg–1 with reputable cycling stability.