Cationic chain-anchored monolayer enables wide-temperature composite polymer electrolytes for lithium-metal batteries

Ionic transport pathways critically influence the stability, capacity, and safety of solid-state lithium-metal batteries. However, realizing efficient ionic conduction that couples fast ion transport kinetics with interfacial stability remains a formidable challenge in solid-state lithium-metal batteries under wide-temperature conditions. Here, we report a cationic chain-anchored monolayer strategy for engineering stable ion transport pathways within poly(vinylidene fluoride-co-hexafluoropropylene)/garnet-based composite polymer electrolytes. The dynamic evolution is investigated using synchrotron infrared spectroscopy, two-dimensional solid-state nuclear magnetic resonance spectroscopy, and additional operando measurements. We demonstrate that an in-situ formed single-ion-like conducting cationic chain-anchored monolayer, featuring solvent-phobic chain-tethered cationic channels, establishes robust and efficient ion transport pathways in the composite electrolyte interface. The resultant electrolytes deliver a low activation energy (0.092 eV) and high Li⁺ transference number (0.78), enabling 400 cycles at 120 °C (Li||LiFePO₄, >99% capacity retention) and 450 cycles at -25 °C (4.5 V Li||LiNi_0.8Co_0.1Mn_0.1O₂, 82.5% capacity retention). Our work offers an effective strategy towards quasi-solid/solid-state lithium-metal batteries with stable long-term cycling across a wide-temperature range.