Tough and Durable\nSlide-Ring Ion Gels for Stretchable\nElectronics Leveraging Strain-Induced Crystallization of Poly(ethylene\nglycol)

Conventional ion gels comprising ionic liquids (ILs)\nand polymer\nnetworks exhibit a trade-off between mechanical toughness and durability.\nDespite their promising electrochemical properties, this trade-off\nhas limited their applicability in stretchable electronics subjected\nto successive and high-frequency deformation. In this study, we have\nfabricated tough and durable ion gels by using reversible strain-induced\ncrystallization (SIC) of poly(ethylene glycol) (PEG) in slide-ring\n(SR) ion gels, in which PEG chains are cross-linked by ring molecules.\nSIC provides mechanical toughness without irrevocably changing their\nnetwork structure after experiencing repetitive deformation. We highlight\nthe outstanding ion-transport and mechanical properties of SR ion\ngels swollen with 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)\nimide ([C<sub>2</sub>mim][NTf<sub>2</sub>]). SR ion gels displayed\nion-conductivity values >1 mS cm<sup>–1</sup> at 313 K,\nrupture\nenergy comparable to the highest values reported for ion gels, as\nwell as constant stress–strain relationships over thousands\nof recurrent loading–unloading cycles. In this study, we demonstrated\nthat SIC can overcome the typical dilemma of toughness and durability\nin existing ion gels.