DFT Calculations for Temperature Stable Quantum Capacitance of VS₂ Based Electrodes for Supercapacitors

Using density functional theory calculations, we demonstrate the quantum capacitance of the VS₂ electrode which can be improved by doping with non-metallic elements such as nitrogen (N), phosphorus (P), and arsenic (As) atoms. The radius, charge, and morphology of these non-metallic elements help to improve the performance of VS₂ material as electrodes of supercapacitors. The As-doped VS₂ monolayer demonstrated the maximum quantum capacitance of 31.2369 μF/cm² at 300 K. At 1200 K, quantum capacitance reaches the value of 25.2149 μF/cm², showing the inconsiderable change in value for this wide range of temperature variation. Additionally, the other important properties of undoped and doped VS₂ monolayers such as density of states, energy band structure, electrical conductivity, thermal conductivity, and the Seebeck coefficient were also computed and examined in detail. The band structure of the P and As-doped VS₂ monolayers showed a metallic nature, which is suitable for electrode application. In the case of As-doped VS₂ material, a high figure of merit of 3.536 was observed by using DFT-D2 calculations, due to the large Seebeck coefficient and significant electrical conductivity. Our findings will be helpful in further exploring the suitability of VS₂ monolayers as electrodes of supercapacitors.