In this study, plasticized solid biopolymer electrolytes (SBEs) were successfully developed by incorporating ethylene carbonate (EC) and an ionic liquid, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), into alginate (Alg) doped with glycolic acid (GA) using the solvent casting method. The electrochemical properties of the prepared SBEs were analyzed through impedance spectroscopy to evaluate their ionic conduction behavior. At ambient temperature, the ionic conductivity of the unplasticized Alg-GA system reached ~ 10–5 S cm−1 with the addition of 20 wt% GA, and further increased to the order of ~ 10–4 S cm−1 and ~ 10–3 S cm−1 upon the introduction of plasticizers, with the highest conductivity of 2.03 × 10–3 S cm−1 achieved in the IL-plasticized system. The temperature-dependent conductivity followed Arrhenius behavior, confirming thermally activated ion transport. Jonscher’s power law was employed to analyze the AC conductivity trends, while theoretical conduction models were used to describe the charge transport mechanisms. The results indicate that the unplasticized system follows the quantum mechanical tunneling (QMT) model, whereas the plasticized systems exhibit conduction behavior consistent with the correlated barrier hopping (CBH) model. These findings demonstrate the significant role of plasticizers in enhancing ion transport and optimizing the electrochemical performance of Alg-GA-based SBEs for potential applications in sustainable energy storage devices.