Tough and Durable Slide-Ring Ion Gels for Stretchable Electronics Leveraging Strain-Induced Crystallization of Poly(ethylene glycol)

Conventional ion gels comprising ionic liquids (ILs) and polymer networks exhibit a trade-off between mechanical toughness and durability. Despite their promising electrochemical properties, this trade-off has limited their applicability in stretchable electronics subjected to successive and high-frequency deformation. In this study, we have fabricated tough and durable ion gels by using reversible strain-induced crystallization (SIC) of poly(ethylene glycol) (PEG) in slide-ring (SR) ion gels, in which PEG chains are cross-linked by ring molecules. SIC provides mechanical toughness without irrevocably changing their network structure after experiencing repetitive deformation. We highlight the outstanding ion-transport and mechanical properties of SR ion gels swollen with 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide ([C2mim][NTf2]). SR ion gels displayed ion-conductivity values >1 mS cm–1 at 313 K, rupture energy comparable to the highest values reported for ion gels, as well as constant stress–strain relationships over thousands of recurrent loading–unloading cycles. In this study, we demonstrated that SIC can overcome the typical dilemma of toughness and durability in existing ion gels.