Effect of Ionic Liquid on Poly(Acrylic Acid)/Aloe Vera-Based Gel Polymer Blend Electrolyte

Foong, Jie Shen (2025) Effect of Ionic Liquid on Poly(Acrylic Acid)/Aloe Vera-Based Gel Polymer Blend Electrolyte. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Gel polymer electrolytes have garnered significant attention for use in energy storage devices as a replacement to liquid electrolytes. In this project, a gel polymer blend electrolyte consisting of poly(acrylic acid) (PAA)/Aloe vera-lithium trifluoromethanesulfonate (LiOtf) and 1-ethyl-1-methylpyrrolidinium bromide (EMPyrrBr) ionic liquid were prepared by solution casting technique. The addition of EMPyrrBr is to determine its optimum ratio to the ionic liquid-free GPE and study its effects on the ionic conductivity, thermal stability, structural and electrochemical properties. Ionic liquid-free PAA/Aloe vera-LiOtf gel polymer blend electrolyte shows an ionic conductivity of (3.41 ± 0.01) × 10-3 S cm-1 and the ionic conductivity increases to (1.97 ± 0.01) × 10-2 S cm-1 upon the addition of 25 wt.% of EMPyrrBr. The ion conduction mechanism follows the Arrhenius theory where the ions migrate more vigorously along the polymer matrix based on an ion-hopping mechanism at elevated temperatures. The complexation between PAA, Aloe vera, LiOtf and EMPyrrBr was confirmed by FTIR analysis. Ionic liquid-added gel polymer blend electrolytes show glass transition temperature (Tg) of 57-59℃ in differential scanning calorimetry (DSC) analysis. In thermogravimetric analaysis (TGA), the thermal stability of the polymer blend electrolyte shows a slight decrease upon the inclusion of EMPyrrBr when heated until 800℃. The ionic liquid-added GPE exhibits the highest working potential window of 2.23 V and ion transport number of 0.9526 as proven in linear sweep voltammetry (LSV) and transference number analysis.