Constructing Low-Friction Ion Transport Pathways in Crosslinked Polymer Electrolyte for Practical Quasi-Solid-State Lithium Metal Batteries

Quasi-solid-state polymer electrolytes are promising candidates for lithium metal batteries (LMBs) with high energy density, but still suffer from sacrificed ionic conductivity caused by electrolyte solidification. Here, by tuning monomer structures with different Li⁺-affinity, we investigate the decisive role of the segmental solvation ability of the polymer matrix in cation transport. Owing to the overly strong affinity for cations, conventional ether segments significantly decrease the Li⁺ relaxation rate, and the resulting "sticky" polymer chains impede Li⁺ migration. In contrast, the weakly coordinating segments such as fluorinated ether could effectively minimize coupling with Li⁺ ions, thereby constructing "low-friction" cation transport pathways in crosslinked polymer electrolytes, as reflected by the nearly unchanged Li⁺ relaxation kinetics and high ionic conductivity. Therefore, the industrial Li metal pouch cells achieve excellent comprehensive electrochemical performance under harsh lean-electrolyte conditions, with electrolyte dosage even as low as 1.3 g Ah^-1. The 2 Ah NCM811/Li cell exhibits an extended lifespan beyond 520 cycles and maintains stable operation across a wide temperature range from -50°C to +90°C. The 8.7 Ah NCM955/Li cell delivers 550 Wh kg^-1 energy density and demonstrates impressive cycling stability over 260 cycles. This work could inspire fundamental understanding and further development toward practical LMBs.