Antioxidative Fluoropolymer Gel Electrolyte for High‐Voltage Lithium Metal Batteries Achieved by Facile In Situ Polymerization

Gel polymer electrolytes (GPEs) are regarded as a promising alternative to traditional liquid electrolytes due to safety concerns of batteries. However, GPEs encounter challenges primarily related to their low oxidative decomposition potential and inferior interfacial compatibility with electrodes. Poly(methyl methacrylate‐trifluoroethyl methacrylate‐isocyanate ethyl methacrylate) (P(MMA‐TFEMA‐IMA)) fluoropolymer‐based GPE is designed and prepared by a facile in situ thermal polymerization process. Due to the high liquid uptake ability of polymers inherited from MMA monomers, GPE exhibits a high room temperature ionic conductivity. By incorporating the fluorinated functional group with higher bond energy through TFEMA monomer, the GPE achieves an enhanced oxidative decomposition voltage. Due to effective interfacial contact between electrode and electrolyte, the Li||GPE||Li cell demonstrates stable cycling time for over 500 h without short‐circuiting. Furthermore, Li||GPE||LiNi 0.6 Co 0.2 Mn 0.2 O 2 cell exhibits an initial discharge capacity of 171.7 mAh g −1 at 0.5 C current rate, maintaining 81.5% of its initial capacity after 200 cycles. The partial IMA segment plays a crucial role in building a high‐quality and stable cathode electrolyte interface film, which contributes to the reduced interfacial resistance and the improved structural stability of high‐voltage cathodes. These findings provide a straightforward method for designing comprehensive electrolytes suitable for high‐energy‐density lithium metal batteries.