Ionic conduction in 70-MeV C5+-ion-irradiated poly(vinylidenefluoride-co-hexafluoropropylene)-based gel polymer electrolytes

Abstract

In an attempt to increase the Li+-ion diffusivity, poly(vinylidenefluoride-co-hexafluoropropylene)-(propylene carbonate+diethyl carbonate)-lithium perchlorate gel polymer electrolyte system has been irradiated with 70-MeV C5+-ion beam of nine different fluences. Swift heavy-ion irradiation shows enhancement in ionic conductivity at lower fluences and decrease in ionic conductivity at higher fluences with respect to unirradiated gel polymer electrolyte films. Maximum room-temperature (303K) ionic conductivity is found to be 2×10−2S∕cm after irradiation with a fluence of 1011ions∕cm2. This interesting result could be attributed to the fact that for a particular ion beam with a given energy, a higher fluence provides critical activation energy for cross linking and crystallization to occur, which results in the decrease in ionic conductivity. X-ray-diffraction results show decrease in the degree of crystallinity upon ion irradiation at low fluences (⩽1011ions∕cm2) and increase in crystallinity at higher fluences (>1011ions∕cm2). Analysis of Fourier-transform infrared spectroscopy results suggests the bond breaking at a fluence of 5×109ions∕cm2 and cross linking at a fluence of 1012ions∕cm2 and corroborate conductivity and x-ray-diffraction results. Scanning electron micrographs exhibit increased porosity of the polymer electrolyte after ion irradiation.