<scp> LiNO ₃ </scp> ‐induced ionic conductivity and band gap modulation in alginate polymer electrolytes

Abstract This study reports the successful synthesis of bio‐based polymer electrolytes (BBPEs) based on sodium alginate, incorporating varying content of lithium nitrate (LiNO 3 ), prepared using the solution casting method. The abundant functional groups in alginate enable effective salt complexation, while LiNO 3 provides mobile charge carriers, supporting the development of sustainable BBPE materials. Electrical performance, assessed via electrical impedance spectroscopy, showed an increasing trend in AC conductivity with higher salt content, peaking at ~ 10 −4 S cm −1 at room temperature. Frequency‐dependent analysis followed Jonscher's universal power law, indicating a hopping mechanism. UV–visible spectroscopy revealed a redshift in the absorption spectra and a decrease in the optical band gap from 5.41 to 5.32 eV, reflecting increased structural disorder and electronic delocalization. These results underline a strong link between ionic and optical properties, reinforcing the potential of LiNO 3 ‐doped alginate BBPEs for sustainable and transparent electrochemical systems. © 2025 Society of Chemical Industry.