DOI: https://doi.org/10.55373/mjchem.v26i4.167

Keywords: Tamarind seed polysaccharide; deep eutectic solvent; flexible film; lithium-ion batteries

Abstract

The presence of hydroxyl groups in polysaccharides results in brittle electrolyte films with poor ionic conductivity. The incorporation of traditional plasticizers like ethylene carbonate (EC) and propylene carbonate (PC) had effectively addressed the brittleness problem, but these plasticizers pose health risks. Thus, in this study, different weight percentages (%) (i.e., 0.2, 0.3, 0.4, 0.5, and 0.6 wt%) of choline chloride:1,4-butanediol (ChCl:1,4-BD), deep eutectic solvent (DES) with lower toxicity were incorporated into the tamarind seed polysaccharide (TSP) matrix. Then, the structural, electrical, morphological, and mechanical properties of the films obtained were evaluated. The polymer electrolyte films were prepared using the solution casting technique and a fixed amount of lithium triflate (LiTf) was added as the additional conducting species. A flexible and free-standing film of TSP-based electrolyte at the highest ionic conductivity of 2.30 x 10-4 S cm-1 was successfully obtained with the addition of 0.4 wt% of DES (TSPL 0.4). This was probably due to the successful prevention of hydrogen bonding as DES occupied the spaces between TSP chains. This could be further supported by the TSP-DES, TSP-LiTf, and salt-DES interactions as confirmed from Fourier transform infrared spectroscopy (FTIR) analyses. The smooth surface with no agglomeration due to salt and DES particles was observed for the optical micrograph of TSPL 0.4. This is due to the salt-DES interaction, which also contributes to the enhancement of the ionic conductivity of TSPL 0.4. The tensile test demonstrates the maximum tensile strain of 50.00% for TSPL 0.4, indicating the highest flexibility of the sample.