Swift heavy ion irradiation induced enhancement in electrochemical properties of ionic liquid based PVdF-HFP-layered silicate nanocomposite electrolyte membranes

• Polymer layered silicate nanocomposites have been irradiated with Si9+ ions.
• Use of ionic liquid as salt helped to achieve high ionic conductivity.
• Intercalation increases with increasing fluence finally leading to exfoliation.
• Room temperature ionic conductivity of the order of 10−2 S cm−1 has been obtained.
• Electrochemical stability window of −3.9 V to 6.5 V has been achieved.

In the present work, effects of 100 MeV Si9+ ion irradiation of different fluences on poly(vinylidene fluoride-co-hexafluoro propylene) (PVdF-HFP)-layered silicate nanocomposite electrolyte membranes based on ionic liquid, 1-butyl-3-methylimidazolium bromide have been investigated. With increasing ion fluence, intercalation of PVdF-HFP into the interlayers of layered silicate increases eventually leading to exfoliation of silicate layers at the fluence of 5×1011 ions cm−2. Swift heavy ion (SHI) irradiation induces chain scissions in the polymer leading to increase in amorphicity due to which room temperature ionic conductivity increases with increasing ion fluence. Highest room temperature ionic conductivity of 4.96×10–2 S cm−1 has been obtained at the highest fluence of 1×1012 ions cm−2 employed in the present work. SHI irradiation increases the porosity of the nanocomposite electrolyte membranes as confirmed from scanning electron microscopy results. Contact angle measurements reveal that upon SHI irradiation the hydrophilic electrolyte membranes turn hydrophobic. High electrochemical stability window of −3.9 V to 6.5 has been achieved at the highest ion fluence of 1×1012 ions cm−2. Upon SHI irradiation the rate of decrease of ionic conductivity becomes slower indicating enhancement in interfacial stability.