Heteroleptic Coordination Polymer Electrolytes Initiated by Lewis-Acidic Eutectics for Solid Zinc–Metal Batteries

Solid polymer electrolytes (SPEs) offer a viable path for overcoming the interfacial problems caused by side reactions and irregular deposition in rechargeable Zn (zinc)–metal batteries. However, this potential has been hampered by limited Zn2+ mobility in polymers; a central conundrum remains on how to solvate Zn2+ strongly enough to free it from anionic traps but weakly enough to minimize its migration barriers. Inspired by biologically dynamic Zn functions, we report a general strategy for constructing highly Zn2+-conductive SPEs by the engineering of heteroleptic coordination. Leveraging polymerization catalyzed by Lewis-acidic Zn2+ predissociated eutectics, we stoichiometrically integrate polymeric ligands (polyacrylamide) with kindred small-molecule co-ligands (acetamide) for Zn2+ centers. This heteroleptic configuration allows for the formation of entropy-increased ion channels with both labile Zn2+–polymer bonding and accelerated polymer mobility, warranting conductivity gains of 2 orders of magnitude and doubling the Zn2+-transference number to 0.44, compared with traditional SPEs. The applicability of the proposed heteroleptic coordination design is also demonstrated by the improved reversibility of Zn plating/stripping process (1200 h) and prolonged cycle life of solid Zn–metal batteries (350 cycles with Mo6S8 cathodes) with improved Coulombic efficiency (∼99%). This study underscores the importance of tailoring the coordination environment in improving cationic mobility in polymers.