Construction of weakly solvating solid polymer electrolytes for high-voltage and stable lithium metal batteries

Industrial applications of in-situ polymerized solid-state electrolytes still face major challenges, such as low ionic conductivity, electrochemical instability, and incompatibility with high-voltage cathode. Herein, the fluorine-containing weakly solvating solid polymer electrolytes are designed to regulate the solvation structure, Li⁺ conductivity, and electrode/electrolyte interface. The strong electron-withdrawing effect and localization ability of fluorine atoms alter the electrostatic potential and charge distribution of the ether oxygen groups in monomer and solvent. This weakens the coordination between Li⁺ and the monomer/solvent while enhancing the coordination with the salt anion, leading to the formation of more contact ion pairs (CIPs) and aggregates (AGGs). This promotes the formation of inorganic-rich solid electrolyte interphase (SEI), enhancing the ionic conductivity of electrolytes and ameliorating the electrode/electrolyte interface. Furthermore, the introduction of fluorine lowers the HOMO of electrolyte, effectively improving its oxidative stability. Herein, a stable lithium stripping/deposition is achieved in Li||Li symmetric cells, maintaining 6420 h at 0.05 mA cm^-2. Furthermore, the Li||LiCoO₂ cells stably work 281 cycles with a capacity retention of 89.3 % at 0.5 C during a high voltage of 3-4.5 V. This strategy paves the way for the practicability of lithium metal batteries.