Effect of aging on the ionic conductivity of polyvinylidenefluoride-hexafluoropropylene (PVdF-HFP) membrane impregnated with different lithium salts

The aging towards the ionic conductivity have been studied using of different lithium salts namely, lithium bis(oxalate)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium fluoroalkylphosphate (LiFAP) and LiPF6 in polyvinylidenefluoride-hexafluoropropylene (PVdF-HFP) matrix. The crystallization behavior of LiBOB and LiDFOB has been noticed for the first time during storage of such membranes within the texture of PVdF-HFP matrix. At the same time, such behavior has not been observed in the case of LiFAP and LiPF6 based membranes. The growth of such crystallites would certainly hinder the mobility mechanism of Li+ ions and it has been confirmed by ionic conductivity measurements. The formation of such crystals has been validated through scanning electron microscopic studies.