Nonflammable eutectic GPEs mediated by solvent-anchoring effect enabling improved interfacial Li+ transport kinetics in high-performance lithium metal batteries

Abstract

Nonflammable gel polymer electrolytes (GPEs) are intriguing owing to their flame-retardancy, high ionic conductivity and nonleakage properties. However, their application is critically hindered by unfavorable interfacial compatibility due to the incorporation of high-reactive solvents. Herein, we present an innovative solvent anchoring strategy to remold Li⁺ solvation structure, thus inducing an effective interfacial protective layer to alleviate adverse solvents decomposition. A nonflammable eutectic GPE (DIPE) is synthesized by in situ incorporating poly-ethoxylated trimethylolpropane triacrylate (PETPTA) polymer skeleton to flame-retardant LiTFSI-sulfolane (SL)-based deep eutectic solvent (DES). The “SL solvent anchoring” strategy is validated to rely on dipole–dipole intermolecular interaction between CH₂ groups on the PETPTA polymer skeleton and OS groups on SL solvents, which breaks the solvation dominance of SL solvents and directly suppresses their decomposition. It simultaneously facilitates reconstruction of a TFSI⁻-dominated Li⁺ solvation sheath without increasing LiTFSI concentration, thereby fostering anion-derived SEI and CEI protective layers. Dynamic interfacial resistance evolution reveals accelerated interfacial Li⁺ transport kinetics in DIPE. Therefore, Li|DIPE|Li cell delivers remarkably enhanced Li reversibility with cycle life over 1000 h at 0.1 mA cm⁻² and Li|DIPE|LCO cell achieves 90.7% capacity retention over 700 cycles at 0.3 C. This study opens an emerging avenue to remold Li⁺ solvation environment and enhance interfacial compatibility in GPE by manipulating the solvent-anchoring effect.