Stabilizing Residual Monomers within In Situ Polymerized Electrolytes for High-Voltage Lithium Metal Batteries

Poly(1,3-dioxolane) (PDOL)-based electrolyte has gained wide attention due to its high compatibility with the lithium metal anode, intimate contact with electrodes, and high ionic conductivity. However, its application in high-voltage batteries is limited because the residual DOL monomers are prone to oxidation at high voltage. Here, we report that LiDFOB-initiated in situ polymerization stabilizes these residual monomers, thus overcoming the oxidation-related limitations of PDOL-based electrolytes. This approach promotes the formation of a thermodynamically stable Li⁺-DOL-DFOB^- solvation structure and DOL-PDOL clusters, reducing the oxidative decomposition of the residual DOL monomers and extending the electrochemical stability window up to 5.0 V vs Li⁺/Li. It also enhances ionic conductivity (4.39 mS cm^-1), and facilitates the formation of a uniform, F-rich cathode-electrolyte interphase. Electrochemical tests and computational simulations reveal that the reduced Li⁺-PDOL interactions in the designed PDOL promote higher ionic mobility and electrochemical stability. Consequently, Li||LiCoO₂ cells using the designed PDOL exhibit remarkable cycling performance, maintaining 80% capacity retention over 760 cycles at a cut-off voltage of 4.35 V. These findings establish PDOL as a transformative electrolyte for high-voltage lithium metal batteries.