Effect of gamma irradiation on poly(vinyledene difluoride)–lithium bis(oxalato)borate electrolyte

Abstract

A poly(vinyledene difluoride)–lithium bis(oxalato)borate solid polymer electrolyte prepared by a solvent casting method has been irradiated with different doses of gamma-rays. Differential scanning calorimetry reveals that the polymer electrolyte irradiated with 35 kGy of γ-rays is the most amorphous sample. This is also supported by the results obtained from X-ray diffraction. The Fourier transform infrared spectrum of each irradiated sample has been deconvoluted in the wavenumber region between 1830 and 1758 cm⁻¹ in order to predict the percentage of free and contact ions in the samples. The sample exposed to 35 kGy of γ-rays contains the highest percentage of free ions and the lowest amount of contact ions. This sample also exhibits the highest room temperature conductivity of 3.05 × 10⁻⁴ S cm⁻¹, which is 15% higher relative to the virgin sample. The number density of free ions is observed to have more control on the conductivity variation with the γ-radiation dose compared to ionic mobility. This study confirms that γ-irradiation can be a potential way to obtain highly conductive and mechanically stable polymer electrolytes.