<p>The rising energy demand and sustainability challenges spur the eagerness to find new alternatives to traditional electrolytes for electrochemical applications. The present work employed classical molecular dynamics simulations to unveil the molecular understanding of betaine-based biodegradable ionic liquids (ILs). The role of the alkyl tail, which consists of an ether functionalized group in betaine-based ILs, is examined using [1O2BET]⁺ and [2O2BET]⁺ cations. The impact of methyl and ethyl tail groups on the structure–property relationship and ion dynamics is investigated using [DCA]^- and [TFSI]^- counter anions for the IL system at 300 K. The scaled atomic charges were derived using Density Functional Theory (DFT) calculations combined with the Density Derived Electrostatic and Chemical (DDEC) method to account for the ionic polarization. Binding energy and Radial distribution function analysis were carried out to elucidate the local structural arrangement and specific ion-ion interactions. Spatial distribution density maps differentiate these ILs, and the spatial arrangement of counter ions is found largely around the quaternary head group of betaine-based cations. The structure factor plots and velocity autocorrelation function helped to distinguish [1O2BET]⁺ and [2O2BET]⁺ cations. The [1O2BET][DCA] IL exhibits higher diffusion coefficients for cations and anions. Diffusion coefficients from simulation are used to estimate the ionic conductivity via the Nernst-Einstein relation and compared with experiments. The trends from simulations are found to be in close agreement with experiment and a good match for [TFSI]^- based ILs.</p> Graphical Abstract <p></p>