Study of PVAc-PMMA-LiCl polymer blend electrolyte and the effect of plasticizer ethylene carbonate and nanofiller titania on PVAc-PMMA-LiCl polymer blend electrolyte

Abstract

Abstract lithium ion conducting polymer electrolyte is one of the essential components of modern rechargeable lithium batteries because of its good interfacial contact with electrodes and effective mechanical properties. A solid lithium ion conducting polymer blend electrolyte is prepared using poly (vinyl acetate) (PVAc) and poly (methyl methacrylate) (PMMA) polymers with different molecular weight percentages (wt%) of lithium chloride (LiCl) by the solution casting technique with tetrahydrofuran as a solvent. The polymer electrolytes were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), Thermogravimetry (TG), AC impedance spectroscopy and ionic transport measurements. XRD and FTIR studies confirm the amorphous nature of the polymer electrolyte and the complexation of salt with polymer. The thermal behavior of polymer electrolytes has been studied from DSC and TG. The highest conductivity obtained using AC impedance spectroscopy is 1.03×10−5 Scm−1 at 303 K for 70 wt%PVAc:30 wt%PMMA:0.8 wt% of LiCl polymer-salt complex. The plasticizer ethylene carbonate (EC) and nanofiller titania (TiO2) were added to the optimized high conducting blend polymer electrolyte. An enhancement in conductivity by one order of magnitude was observed for the plasticized 70 wt%PVAc-30 wt%PMMA-0.8 wt% LiCl polymer electrolyte at ambient temperature. The ionic conductivity value obtained using AC impedance spectroscopy for the plasticized 70 wt%PVAc-30 wt%PMMA-0.8 wt% LiCl polymer electrolyte was 1.03×10−4 Scm−1. The highest conductivity obtained for 70 wt%PVAc-30 wt%PMMA-0.8% LiCl-6 mg TiO2 was 4.45×10−4 Scm−1. Dielectric properties of polymer films are studied and discussed. The electrochemical stability of 1.69 V and 2.69 V was obtained for 70 wt%PVAc-30 wt%PMMA-0.8% LiCl and 70 wt%PVAc-30 wt%PMMA-0.8% LiCl-6 mg TiO2 polymer electrolytes, respectively, using linear sweep voltammetry. The value of Li+ ion transference number was estimated by the DC polarization method and was found to be 0.99 for the highest conducting 70 wt%PVAc-30 wt%PMMA-0.8 wt% LiCl-6 mg TiO2 nanocomposite polymer electrolyte.