High‐Voltage All‐Solid‐State Lithium Metal Batteries Enabled by Localized High‐Salt‐Concentration In‐Chain Clustering Copolymer Electrolytes

Abstract All‐solid‐state polymer electrolyte‐based rechargeable batteries paired with high‐voltage cathodes and lithium anodes hold promising prospects to increase the energy density and the safety of lithium metal batteries (LMBs). To improve the stability of the polymer electrolytes at both the positive and negative electrodes, fluorinated polymer electrolytes have been designed and synthesized by copolymerization of epoxide monomers containing cyclic carbonates and fluorinated moieties. The cyclic carbonates possessing a large dielectric constant endow the polymer electrolytes with a high salt solubility. While, the introduction of the fluorinated moieties gives rise to an enhanced oxidation resistance of the electrolytes particularly in the cathode on one hand; on the other hand, it results in in‐chain micelle‐like clusters on the scale of a few nanometers due to the superior hydrophobicity, hence promoting the formation of localized high‐concentration polymer‐in‐salt electrolytes (PISEs) with a high lithium‐ion conductivity and transference number. This synergistic strategy enables a large lithium‐ion transference number of ∼0.72, a wide electrochemical stability window up to 5.2 V, and stable electrode/electrolyte interfaces. The Li/PISE/Li cells demonstrate stable cycling over 1500 h, and the all‐solid‐state NCM811/PISE/Li batteries exhibit a superior discharge capacity and prolonged cycling stability (∼98% capacity retention at 500 cycles) at 30 °C.