Development and Investigation of Electrochemical and Dielectric Properties of Eco-Friendly Lithium-Ion Conductor Biopolymer Electrolyte for Energy Storage Application

This study investigates Li⁺ ion-conducting biopolymer blend electrolytes-based on chitosan (CS) and potato starch (PS) with glycerol plasticization. The advanced techniques including FTIR, impedance, TNM, LSV, and CV were employed to characterize the compositional and electrochemical properties of the solid films. The FTIR analysis indicates significant influence of glycerol on polymer/salt interactions, evidenced by the shift of FTIR bands to lower wavenumbers, signifying an increase in free ions within the host polymer system. Impedance results indicate that plasticizer addition reduces the bulk resistance to an optimum value of 49 Ω. The calculated DC values demonstrate the suitability of the electrolyte for use in energy storage applications (ESAs) with the highest ionic conductivity of 2.01 × 10⁻⁴ S cm⁻¹. The high values of both \({\epsilon }^{{\prime }}\) ${ϵ}^{\prime }$ and \({\epsilon }^{{\prime }{\prime }}\) ${ϵ}^{\prime \prime }$ at lower frequencies are due to interfacial polarization and the accumulation of charges, respectively. The sample with the largest plasticizer content has shown the highest \({\epsilon }^{{\prime }}\) ${ϵ}^{\prime }$ of 112.4 at 10⁵ Hz. The shifting of tan δ peaks to the higher frequency side with the increase of plasticizer indicates an increase in the mobility of cations. The combination of tan δ plot and Argand plot was used to explore the dominant mechanism in ion conduction. The electrochemical studies were performed to detect the ability of the films to be used for EDLC applications. The TNM (t_ion=0.947) and LSV (decomposition voltage = 3.1 V) values favor the films for ESAs. The pattern of CV curves at various scan rates established the successful design of the EDLC device. The calculated capacitance from the area under CV curves is sufficiently high. The capacitance was influenced by scan rates and changed from 12.92 to 38.68 F/g.