Fluorine-oxygen co-coordination of lithium in fluorinated polymers for broad temperature quasi-solid-state batteries

Polymer-based solid-state batteries operable across broad temperatures are critical for advanced energy storage but face limitations from sluggish ion transport kinetics in polymer electrolytes. Here, we develop a fluorinated quasi-solid polymer electrolyte that balances weak Li⁺-polymer interactions with efficient salt dissociation. This electrolyte was fabricated by in situ polymerization of 2,2,3,4,4,4-hexafluorobutyl acrylate. The incorporation of -CF2- groups within 2,2,3,4,4,4-hexafluorobutyl acrylate promotes the formation a fluorine-oxygen co-coordination structure that decouples ion conduction from polymer relaxation. This mechanism creates more efficient Li⁺ transport pathways along polymer chains and surrounding solvent molecules, promoting uniform Li⁺ flux at the Li metal electrode interface. Consequently, the electrolyte exhibits 0.27 mS cm−1 conductivity at −40 °C, enabling 10 C rates and operation from −50 to 70 °C in Li | |LiNi0.8Co0.1Mn0.1O2 cells. At 20 mA g−1 and −30 °C, the 4.5 V coin cell retains 64.3% capacity of its 30 °C capacity, while cells maintain 86% capacity after 200 cycles at 60 mA g−1 and 30 °C. Extending this coordination-tuning strategy to sodium-based systems yields similar ion-transport enhancements, highlighting its broad applicability for next-generation solid-state batteries. Polymer solid-state batteries operable across low and high temperatures face sluggish ion transport limitations. The authors develop a fluorinated polymer electrolyte with tailored Li–F/O coordination that decouples ion conduction from polymer relaxation, enabling stable Li metal cell operation from −50 to 70 °C.