Lithium ion conducting biopolymer membrane based on kappa carrageenan with LiCl and its application to electrochemical devices

Abstract

A lithium ion conducting solid biopolymer membrane (SBE) has been prepared by incorporating lithium chloride salt (LiCl) with the biopolymer K- Carrageenan (Kappa Carrageenan) using solution casting technique. One gram Kappa Carrageenan with 0.5 g LiCl yields ionic conductivity value of 1.15 × 10-2 Scm−1 which has been found by using Ac impedance analysis. The highest conducting biopolymer membrane possesses high amorphous nature among all the prepared biopolymer membranes, and XRD analysis confirms it. Highest conducting biopolymer possesses low crystallinity percentage of 8.18. Transference number analysis by Wagner’s polarization technique provides information that the major contribution for the conductivity is given by ions whereas minor contribution has been given by electrons. Transference number of ions is found to be 0.96 whereas transference number of electrons is 0.04. By using the using highest conducting composition (one gram Kappa Carrageenan: 0.5 g LiCl) as electrolyte, LiFePO4 as cathode and activated charcoal/graphite as anode, rechargeable lithium-ion conducting battery has been constructed and its voltage is found as 3.25 V. The performance of the battery has been studied by connecting a load (100 kΩ).