Molecular Dynamics Simulations of Betaine-Based Ionic Liquids: A Comparative Study of Scaled Versus Full Charge Model

Energy demand increases significantly over the years and huge investment is focused on electrolyte materials such as polymer electrolytes, ionic liquids, and composites to fulfill the energy requirements. The performance of energy devices is largely influenced by electrode and electrolyte materials. The accumulation of energy waste including electrolytes and their disposal has drawn attention toward biodegradable electrolytes. In the present work, the betaine-based ionic liquids [C4BET] [TFSI] and [C4BET][DCA] are explored for their electrolyte characteristics at room temperature using classical molecular dynamics simulations. Forcefield parameters are developed using the full charge model (CHELPG method) and scaled charge model (density-derived electrostatic and chemical 3 (DDEC3) and DDEC6 method) to screen the polarizability and charge transfer effects. The radial distribution analysis unveils that cation-anion and anion-anion interactions are relatively weak in the scaled charge model compared to the full charge model. A significant increase in diffusivity can be seen for the scaled charge model and DDEC6 overestimates the mobility of ions. Nernst-Einstein conductivity calculated using the scaled charge models closely resembles experimental conductivity.