Non‐Fluorinated Polymers with Dual Weak‐Solvation Sites for High‐Voltage Lithium Metal Batteries

Solid‐state lithium‐metal batteries (LMBs) using polymer electrolytes emerge as highly promising next‐generation systems. They offer enhanced safety and high energy density (>400 Wh kg −1 ) by replacing flammable liquids with flexible, solid‐state separators. However, conventional polymers face oxidation susceptibility at high voltages (<4.3 V). While fluorinated polymers extend the electrochemical window and induce robust, LiF‐rich interfaces, they are hindered by environmental persistence and high manufacturing costs. To overcome these limitations, we introduce PMDX‐Li, a non‐fluorinated polymer electrolyte designed via a dual weak‐solvation strategy. PMDX‐Li achieves a superior 5.3 V window, a high Li + transference number of 0.77, and an ionic conductivity of 0.48 mS cm −1 . In high‐voltage tests, Ni‐rich cathode cells cycle stably for 900 cycles at 4.3 V with 75.6% retention. Remarkably, cells using 4.6 V lithium‐rich manganese‐based (LRMO) cathodes maintain 80.4% capacity over 120 cycles at a low N/P ratio. Furthermore, an Ah‐level pouch cell demonstrates a high energy density of 415 Wh kg −1 and retains over 400 Wh kg −1 after initial cycling. This proves that high‐voltage performance is achievable without the environmental or cost penalties of fluorination.