Electrochemical investigation of gel polymer electrolytes based on poly(methyl methacrylate) and dimethylacetamide for application in Li-ion batteries

In the present work, gel polymer electrolytes (GPEs) were prepared using poly(methyl methacrylate) (PMMA), lithium perchlorate (LiClO₄) and dimethylacetamide as a plasticizer. Solution-casting technique was used to fabricate GPEs containing different weight percentage of PMMA. The degree of crystallinity of GPE samples was studied by X-ray diffraction (XRD) analysis. Fourier transform infrared (FT-IR) spectroscopy was applied to study the level of interactions between lithium salt and PMMA in the prepared GPEs. Electrochemical properties were studied by electrochemical impedance spectroscopy, linear sweep voltammetry and DC polarization techniques. Lithium ion conductivity of GPEs was determined by calculating the bulk resistance of polymer electrolytes from Nyquist plot. Increasing PMMA content of GPEs resulted in an improvement in the electrochemical potential window from 4.2 to 4.5 V. The highest lithium transference number (0.42) and also the best electrochemical properties were obtained for GPE containing 0.75 M LiClO₄ and 10 wt% PMMA. Scanning electron microscopy images of the optimized GPE showed a porous and heterogeneous surface structure which is desirable for application in Li-ion batteries.