Natural polymer electrolyte based on guar gum doped with NaI for Na-ion batteries

Solid polymer electrolytes play a vital role in energy storage devices, especially in the battery industry, to improve compatibility and portability. Natural polymers made from biowaste material are biodegradable and have been utilized for electrolyte preparation. Biopolymer-based electrolyte leads to sustainability due to their low cost, eco-friendly nature and non-toxicity. This work pertains to the preparation of one such natural polymer electrolyte based on guar gum as the host polymer, sodium iodide as an ionic dopant and 1,2 dimethoxy ethane as the plasticizer. Traditional Solution casting technique has been used for the preparation of electrolytes. The complexation between guar gum (GG) and NaI has been revealed by Fourier transform infrared spectra. The biopolymer electrolyte is stable up to 300–350°C and was assessed by thermogravimetric analysis. The surface roughness factor (R_a) was measured by 3D-optical profilometry. The transference number was determined by the chronoamperometry technique. AC impedance spectroscopy exhibited that the biopolymer electrolyte containing 0.4 g GG: 0.75 wt% NaI has the highest ionic conductivity of 7 × 10^–3 S cm^–1. Hence with suitable electrodes, the prepared electrolyte may be used in the fabrication of coin cells.