Synthesis and characterization of biopolymer electrolyte based on tamarind seed polysaccharide, lithium perchlorate and ethylene carbonate for electrochemical applications

Abstract

Eco-friendly and cost-effective solid biopolymer electrolytes based on tamarind seed polysaccharide (TSP) as host polymer with different concentrations of lithium perchlorate (LiClO 4 ) as ionic dopant salt and different wt% of ethylene carbonate (EC) as plasticizer have been synthesized via solution casting technique. The amorphous nature and complexation of the salt with the polymer matrix have been confirmed by XRD and FTIR analysis, respectively. The change in glass transition temperature (T g ) of the polymer electrolyte has been measured using DSC analysis. Maximum ionic conductivity of 8.77 × 10 −4  S cm −1 is obtained for the polymer electrolyte composition of 1 g TSP/0.45 g LiClO 4 at ambient temperature, whereas the ionic conductivity improved to 1 order of magnitude (1.06 × 10 −3  S cm −1 ) through the incorporation of 0.3 wt% EC plasticizer into the above polymer electrolyte composition determined by AC impedance analysis. The activation energy (E a ) is observed to be low for the highest conducting EC plasticizer incorporated polymer electrolyte. The value of ionic transference number estimated by Wagner’s dc polarization method reveals that the conducting species are predominantly Li + ions. The electrochemical stability window of the highest conducting biopolymer electrolytes has been determined by LSV. From the constructed battery, the open circuit cell potentials of 1.6 and 1.9 V have been observed for the TSP-LiClO 4 and TSP-LiClO 4 -EC polymer electrolyte systems, respectively. The performance of the constructed battery has been compared with the commercially available lithium battery.