Mechanically Robust and Ion-Conductive Polyampholyte Elastomers via Dimeric Ionic Bonding

The development of ionic materials with high ionic conductivity and mechanical strength is challenging. This study presents a novel synthetic strategy for the development of a mechanically robust and ionically conductive polyampholyte elastomer based on ionic dimers (IDs) with strong ionic bonds between imidazolium and sulfonate. Polymerization of ID monomers with a network that forms a cross-linking moiety results in a novel polyampholyte ID elastomer (IDE). The addition of lithium (Li) salts in the IDE substantially enhances the ionic conductivity up to 0.82 mS cm^-1 with a high Li⁺ transference number (t_Li⁺) of 0.79. The mechanical properties of the IDE with Li salts are remarkable, with a tensile strength of 27.4 MPa and a Young's modulus of 211 MPa, outperforming previous polyampholyte elastomers. A resistive-type iontronic sensor using the IDE exhibited excellent sensitivity (gauge factor = 2.92) and reliable cycle performance (≈400 cycles) under repetitive stress. The IDE serves as a polymer electrolyte in a pouch-type full cell, showing stable capacity at a high current density of 1.0 C (corresponding to 4.0 mA cm^-2) under ambient conditions (25 °C, 0.2 MPa). This synthetic strategy offers a new approach for designing ionic materials with high conductivity and mechanical strength.