Enhancing Ion Transport in Polymer Electrolytes by Regulating Solvation Structure via Hydrogen Bond Networks

Polymer electrolytes (PEs) provide enhanced safety for high-energy-density lithium metal batteries (LMBs), yet their practical application is hampered by intrinsically low ionic conductivity and insufficient electrochemical stability, primarily stemming from suboptimal Li⁺ solvation environments and transport pathways coupled with slow polymer dynamics. Herein, we demonstrate a molecular design strategy to overcome these limitations by regulating the Li⁺ solvation structure through the synergistic interplay of conventional Lewis acid-base coordination and engineered hydrogen bond (H-bond) networks, achieved by incorporating specific H-bond donor functionalities (N,N'-methylenebis(acrylamide), MBA) into the polymer architecture. Computational modeling confirms that the introduced H-bonds effectively modulate the Li⁺ coordination environment, promote salt dissociation, and create favorable pathways for faster ion transport decoupled from polymer chain motion. Experimentally, the resultant polymer electrolyte (MFE, based on MBA) enables exceptionally stable Li metal cycling in symmetric cells (>4000 h at 0.1 mA cm^-2), endows LFP|MFE|Li cells with long-term stability, achieving 81.0% capacity retention after 1400 cycles, and confers NCM622|MFE|Li cells with cycling endurance, maintaining 81.0% capacity retention after 800 cycles under a high voltage of 4.3 V at room temperature. This study underscores a potent molecular engineering strategy, leveraging synergistic hydrogen bonding and Lewis acid-base interactions to rationally tailor the Li⁺ solvation structure and unlock efficient ion transport in polymer electrolytes, paving a promising path towards high-performance solid-state lithium metal batteries.