Controlled Comparative Study of Phase Selectivity, Morphology, and Electrochemical Performance in Vanadium-Based Co and Ni Compounds for Hybrid Energy Storage

High Resolution Image Download MS PowerPoint Slide Battery–supercapacitor hybrids (BSHs) with high energy and power densities have emerged as some of the most promising energy storage devices, but developing efficient electrode materials remains essential. Vanadium-based materials with rich redox chemistry are attractive candidates for energy storage, but limited conductivity and structural stability restrict their practical performance. To overcome these limitations, bimetallic systems incorporating cobalt or nickel have been explored to regulate phase formation and enhance electrochemical properties. In this study, vanadium-centered cobalt and nickel compounds are synthesized under identical hydrothermal conditions to enable direct structural and electrochemical comparison. The cobalt-integrated sample (Co–V) forms hollow spherical architectures with a CoV 2 O 6 ·H 2 O phase and achieves a higher specific capacitance (C F ) of 1087.6 F/g at 20 mV/s, while the nickel-integrated material (Ni–V) presents NiS 2 -rich aggregated morphologies with lower surface area and inferior performance. A BSH composed of Co–V and reduced graphene oxide electrodes achieves a maximum energy density of 50.4 Wh/kg and a power density of 650 W/kg. A C F retention of 88.4% and Coulombic efficiency of 96.5% after 10 000 cycles are also attained. This comparative investigation reveals how transition metal selection directs structural evolution and redox behavior in vanadium-based compounds, providing insight into morphology-controlled charge storage mechanisms for advanced hybrid energy devices.