Investigation of seaweed derivative iota-carrageenan based biopolymer electrolytes with lithium trifluoromethanesulfonate

Abstract

In the present work, iota-carrageenan (i-carrageenan) biopolymer derived from edible seaweed has been chosen as the host polymer material for battery electrolyte. Ionic salt of lithium trifluoromethanesulfonate (LiCF _3 SO _3 ) commonly known as lithium triflate has been added with the host polymer as a source of charge carriers. The polymer membranes of 1.0 g i-carrageenan with LiCF _3 SO _3 of various compositions (0.1 wt% to 0.5 wt%) have been prepared by solution casting technique. X-ray diffraction (XRD) results indicate the enhancement in amorphous nature of polymer membranes due to the addition of LiCF _3 SO _3 . Complex formation between the salt and polymer has been studied by Fourier Transform Infrared (FTIR) spectroscopy. The high ionic conductivity of 1.27 × 10 ^−3 S cm ^−1 at room temperature is achieved with the combination of 1.0 g i-carrageenan : 0.4 wt% LiCF _3 SO _3 by AC impedance analysis. Total ion transference number estimated for the highest conducting sample is 0.95 by Wagner’s DC polarization method and electrochemical stability of the same is 3.52 V by Linear Sweep Voltammetry (LSV) measurement. Lithium ion conducting battery has been fabricated using the highest conducting polymer membrane. Its open circuit voltage is measured as 1.70 V and its performance is studied.

Keywords

• iota carrageenan
• lithium triflate
• solid polymer electrolyte
• conductivity