Concentration effects on the structural, transport, and dielectric properties of the energy storage system {NaBF4 – dimethyl sulfoxide} used in sodium-ion battery technology: A molecular dynamics approach and DFT method

Abstract

The transition to sustainable energy has highlighted the need for the development of electrolytic energy storage systems. Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries, offering advantages such as the availability of natural resources, reduced cost, and good low-temperature performance, making them particularly well-suited for large-scale energy storage applications. In this context, we employed two numerical simulation approaches: molecular dynamics (MD) and density functional theory (DFT) to examine the thermodynamic, structural, dynamic, and dielectric properties of the energy storage system {NaBF4 – Dimethylsulfoxide}. For this, we used the GROMOS force field for MD simulations under standard temperature and pressure conditions and at different concentrations ranging from 0.10 to 0.85 M. The DFT calculations were performed at the B3LYP functional level combined with the def2-TZVP and 6–311++G(d,p) basis sets, while implicit solvation effects were taken into account using the CPCM model. Finally, our results from MD and DFT approaches confirmed that the coordination environment of Na⁺ is formed by 3 DMSO molecules and one BF₄⁻ anion. Moreover, the transport of ions as well as the dielectric response show a strong dependence on the salt concentration. Indeed, the increase in concentration leads to a decrease in ionic diffusion and a gradual drop in the dielectric permittivity of the electrolytic solution. These valuable results contribute to the optimization of a new generation of electrolytic systems related to sodium-based rechargeable battery technology.