Poly(vinylidene fluoride)‐based polymer electrolytes are being intensely investigated for solid‐state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom‐to‐up strategy is employed to design single‐phase and densified polymer electrolytes via incorporating quasi‐ionic liquid with poly(vinylidene fluoride‐co‐hexafluoropropylene). Due to strong ion/dipole–dipole interaction, the optimized polymer electrolyte delivers high room‐temperature ionic conductivity of 1.55 × 10−3 S cm−1, superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm−3 as well as desirable self‐extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm−2. In particular, lithium metal battery Li||LiNi0.6Co0.2Mn0.2O2 exhibits a room‐temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid‐flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi‐ionic liquid/polymer electrolytes in safe lithium metal batteries.

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