Unveiling the potential of bimetallic chalcogenides Ni Co2X4 (X = S, Se, Te): A computational exploration of electronic structure, quantum capacitance, and mechanical properties for advanced energy storage

Abstract

A move towards renewable energy sources is now essential to meet society's rising energy demands, and adequate energy storage for later use is also required. This study investigates Bimetallic Transition Metal Chalcogenides (BTMCs), specifically Ni ${\text{Co}}_2{X}_4$ (X = S, Se, Te), for energy storage applications. Using Density Functional Theory (DFT), the electronic properties, quantum capacitance ($C_Q$), and surface charge density of bulk structures are analyzed. BTMCs exhibit enhanced properties due to the synergistic effects of multiple transition metals, making them superior to single-metal chalcogenides. Experimentally less explored Ni ${\text{Co}}_2{\text{Se}}_4$ with cubic phase has shown the highest $C_Q$ (3418 F/g) and surface charge density (1902C/g), attributed to selenium's atomic properties. Highest $C_Q$ obtained for Ni ${\text{Co}}_2{S}_4$, Ni ${\text{Co}}_2{\text{Se}}_4$ and Ni ${\text{Co}}_2{\text{Te}}_4$ is 2510, 3418,2860 F/g at the potential +1V, similar trend is visible in surface charge density are forNi ${\text{Co}}_2{S}_4$, Ni ${\text{Co}}_2{\text{Se}}_4$ and Ni ${\text{Co}}_2{\text{Te}}_4$ is 1791,1902 and 1678 C/g at the potential of +1V.Also, Young's modulus (Y) for Ni ${\text{Co}}_2{S}_4$, Ni ${\text{Co}}_2{\text{Se}}_4$ and Ni ${\text{Co}}_2{\text{Te}}_4$ is 170,189 and 177 GPa, respectively. Higher ‘Y’ of Ni ${\text{Co}}_2{\text{Se}}_4$ will be good for applications requiring high mechanical strength and stiffness. The NiCo₂X₄ (X = S, Se, Te) combination in chalcogenides enhances redox activity, stability, and electrochemical performance through multiple oxidation states and strong orbital hybridization. Computational studies predict material behavior and guide experiments to identify cathodic and anodic materials for asymmetric supercapacitors.