Low‐Hysteresis Liquid‐Free Ionic Conductors With Superior Toughness and High Mechanical Strength Enabled by Conformationally Changeable Crosslinkers

ABSTRACT Low hysteresis, superior toughness, and high mechanical strength are essential for enhancing the reliability and durability of stretchable ionic conductors. However, the production of ionic conductors with these mutually exclusive properties remains a great challenge. Herein, low‐hysteresis and highly resilient liquid‐free ionic conductors with a high strength of ∼4.0 MPa and a high toughness of ∼19.6 MJ/m 3 are fabricated by complexation of vanillin‐grafted polyvinyl alcohol (VPVA) and solid‐state ionic liquid (IL), followed by being crosslinked through 1,1'‐ferrocenedicarboxaldehyde (FcDa) with the force‐dependent conformational change characteristic (denoted as V‐I‐F). During small mechanical loading (≤200% strain), FcDa serve as rigid crosslinkers to efficiently suppress energy dissipation of the V‐I‐F ionic conductors, resulting in conductors with low hysteresis. Upon large mechanical loading, ferrocene in FcDa significantly deforms to activate sufficient energy dissipation pathways, which dramatically improve the toughness and damage resistance of ionic conductors. Even after being crushed by a 1.5‐ton car for 20 times, the V‐I‐F ionic conductors can still immediately recover to their original shape without damage and IL leakage. Meanwhile, the V‐I‐F ionic conductors show extremely low‐hysteresis properties in electrical response aspect and display highly stable and reproducible sensing performances over 4500 uninterrupted loading–unloading cycles at a 200% strain.