Stretchable Ionic-Liquid-Based Gel Polymer Electrolytes for Lithium Ion Batteries

Stretchable cross-linked gel polymer electrolytes (C-GPEs) have been fabricated through electron-beam irradiation (EBI) of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-co-HFP)]/triallyl isocyanurate (TAIC) blend films followed by adsorption of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][TFSI]). It was found that polymer films containing 5 wt % cross-linker exhibit an excellent IL uptake value of 3.0 when irradiated at 75 kGy. The prepared C-GPEs have a high ion conductivity of 1.4 mS/cm at room temperature compared with a value of 0.7 mS/cm for P(VDF-co-HFP)/IL (1/3, m/m) blend gel. Morphological measurements indicate interconnected nanoporous structures in the films that can provide effective channels for ion immigration. Moreover, the C-GPEs show a high tensile strength of 10.6 MPa and an excellent elasticity, with almost full strain recovery after 100% stretch. In a LiFePO4/C-GPE/Li half-cell, the C-GPEs exhibit high electrochemical stability. Therefore, we consider that the prepared C-GPEs might have a potential application in flexible or/and stretchable energy storage devices.