Development of sodium-ion conducting biopolymer electrolyte membrane based on Agar-Agar with sodium perchlorate (NaClO4) using ethylene carbonate (EC) as a plasticizer for primary Na-ion battery

The current study investigates the sodium ion conductivity of ethylene carbonate (EC) integrated biopolymer membranes made of agar-agar and sodium perchlorate in various concentrations. The facile solution cast approach is employed to fabricate the biopolymer membranes. The prepared biopolymer membranes are characterized by XRD, FTIR, DSC, AC Impedance, TGA, CV, and LSV techniques. X-ray diffraction analysis (XRD) studies the degree of crystalline/amorphous nature of the membranes. Fourier transform infrared spectroscopy (FTIR) confirms the complexation between salt and polymer. Adding sodium salt and incorporating a plasticizer improves the ionic conductivity of pure agar-agar from 3.12 x 10-7 S cm-1 to 3.15 x 10-3 S cm-1. Differential scanning calorimetry (DSC) studies the glass transition temperature (Tg) trend with salt concentration. The highest conducting biopolymer membrane exhibits a very low Tg value of 22.05 degrees C. Thermogravimetric analysis (TGA) examines the thermal stability of the membranes. Wagner's DC polarization technique evaluates the transference number for the prepared membrane. The electrochemical and cycling stability of the highest conducting membrane was studied by linear sweep voltammetry (LSV) and cyclic voltammetry (CV), respectively. The findings promote the development of a primary sodium ion conducting battery with the highest performing biopolymer membrane. The battery's performance has been studied with two different cathode materials (V2O5 and MnO2) and the highest remarkable open circuit voltage (OCV) of 3.13 V was achieved when V2O5 was used as a cathode.