Zwitterionic Dynamic Supramolecular Elastomer Electrolytes for High-Voltage and Dendrite-Free Lithium Metal Batteries

To simultaneously address the challenges of lithium (Li) dendrite growth, low ionic conductivity, and limited oxidative stability in lithium metal batteries (LMBs), flexible zwitterionic dynamic supramolecular elastomer electrolytes (DSEEs) with (bis(2-hydroxyethyl)-methyl-(3-sulfopropyl) azanium) and (2-ureido-4-pyrimidinone) as chain extenders are proposed. First, DSEEs promote the formation of an inorganic-rich solid electrolyte interface. Second, the polar groups within zwitterions regulate Li⁺ transport and the electric field at the Li surface, thereby homogenizing Li⁺ deposition. Third, the flexible DSEEs enable strong adhesion to the Li anode through electrostatic attraction, eliminating Li nucleation sites, and self-adapt to volume changes of the Li anode. Fourth, zwitterions enhance Li⁺ dissociation to achieve high ionic conductivity, while their dipole moments and dense hydrogen-bonding network provide substantial oxidation resistance. Notably, the DSEE with balanced zwitterion and hydrogen-bonding density exhibits robust adhesion with a high shear strength (21.0 N cm⁻²), a high ionic conductivity (9.55 × 10⁻⁴ S cm⁻¹), and a wide electrochemical stability window (5.3 V). Importantly, the optimized DSEE enables reversible and stable Li plating/stripping without observable dendrites, as confirmed by morphological and simulation studies, and shows excellent compatibility with various cathodes. Overall, this study opens a new avenue for developing safe, dendrite-free LMBs with high energy density.