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. Furthermore, the Li||LiCoO 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.