Solvation-Preserving Gelation of Localized High-Concentration Electrolytes for Lithium Metal Batteries

Localized high-concentration electrolytes (LHCEs) exhibit excellent interfacial compatibility with lithium metal anodes and high-nickel cathodes, whereas the introduction of polymer networks during gelation may alter their intrinsic solvation structures. Here, we report a solvation-preserving gel electrolyte formed via in situ polymerization of a fluorinated polymer network within a 1,2-Dimethoxyethane (DME)-based LHCE. Unlike conventional gel polymer electrolytes, the fluorinated polymer exhibits limited Li⁺ coordination, thereby largely preserving the localized high-concentration solvation environment during gelation. This design couples the preserved LHCE solvation chemistry with a fluorinated polymer framework, enabling synergistic regulation of electrode-electrolyte interfaces and enhanced electrochemical performance. Meanwhile, the fluorinated polymer network further improves safety by reducing electrolyte flammability. Lithium symmetric cells achieve stable cycling over 2000 h, while LiNi_0.9Co_0.05Mn_0.05O₂ (NCM9)|Li full cells deliver 82.2% capacity retention after 300 cycles and operate stably up to 4.5 V. At the pouch-cell level, a gravimetric energy density of 394.3 Wh kg^-1 is achieved under lean-electrolyte conditions, while no thermal runaway is observed up to 300°C. This work demonstrates that preserving solvation structure via rational polymer network design enables simultaneous improvements in interfacial stability, safety, and practical performance in quasi-solid-state lithium metal batteries.