Preparation and Electrical Characterisation of Tamarind Seed Polysaccharide (TSP) Biopolymer Electrolyte

Abstract

The natural, abundantly available, non-toxic, bio-compatible and bio-degradable biopolymers and polysaccharides had become more viable in the synthesis of polymer electrolytes lately. They became a prime interest forthe development of storage energy devices like Batteries, Fuel cells, sensors and supercapacitors due to their eco-friendliness and cost effectiveness over the other synthetic available solid polymer electrolytes. Tamarind seed polysaccharide a biopolymer extracted from tamarind seed has applications in food industry, cosmetics, pharmaceutical industry and dyeing industries due to its stabilising, thickening and gelling nature and is also an emulsifying agent. The biopolymer electrolytes were prepared by Tamarind Seed Polysaccharide (TSP) as a polymer matrixwith a range ofweight proportions of Sodium Citrate (Na₃C₆H₅O₇). Solvent casting technique was used to prepare the biopolymer membranes with distilled water as solvent. The obtained biopolymer electrolytes were investigated with Impedance Spectroscopy and Transference Number Measurements (TNM). The magnitude of ionic conductivity is found to be increased with increase in salt ratio and temperature. The dielectric parameters like complex dielectricand tangent loss were analysed from AC impedance spectroscopy with frequency range from 42 Hz to 1MHz. The AC impedance data analysis revealed that the biopolymer membrane of 1g TSP:0.3g Na₃C₆H₅O₇ has the highest ionic conductivity with 2.4x10^-4Scm^-1 at room temperature. The decrease in Activation Energy (E_a) with the increase in salt ratio confirmed the Arrhenius relation of the polymer membranes. From the transport number calculations, the transference number close to unity revealed that the conductivity is because of the ions as the predominant charge carriers.