Novel Composites Polymer Electrolytes Based on Methylcellulose-pectin Blend Complexed With Potassium Phosphate and Ethylene Carbonate

Abstract

In large-scale all-solid-state storage technologies, solid polymer electrolytes (SPEs) provide greater safety and longer cycle life than traditional liquid or gel polymer electrolytes. Polymer electrolytes (PEs) derived from biopolymers have been intensively explored for use in electrochemical devices due to their great flexibility, low cost, and environmental sustainability. However, biopolymer-based electrolytes cannot meet the expectations of practical applications at room temperature due to their low ionic conductivity. Over the years, improving the performance of this class of electrolytes has been the focus of intense research and development, notably polymer blending, plasticization, and structural functionalization. Here, we investigate the performance of an all-biopolymer solid electrolyte based on a methylcellulose-pectin blend doped with potassium phosphate. FESEM micrographs as well as the shifting and changing intensity of FTIR bands in the electrolyte specimens confirm the polyblend homogeneity with no phase separation. The increased amorphous fraction of the composites polymer electrolytes (CPEs) is seen in the XRD and DSC patterns of the plasticized and unplasticized samples. Impendence studies performed on the system recorded a maximum ionic conductivity of 1×10-5 Scm-1 by doping with 50 wt.% K3PO4. This value further increased to 5.9×10-5 Scm-1 upon adding 25 wt.% EC to the polymer system. This sample also possesses an electrochemical stability window of 4.24V and an ion transference number of 0.95.