Most Li-metal batteries can work safely only under 45 °C and have risks of burning or explosion. A novel nonflammable Li-battery is developed to address the challenge, using an interpenetrating rigid-flexible poly (aryl-ether-ketone) nonwovens (PAEKNW) cross-linked with poly(ethylene glycol) dimethacrylate electrolyte to transport lithium ions. The hybridized polymer electrolyte possesses a high ionic conductivity of 1.2 × 10−3 S cm−1 at room temperature and a wide electrochemical window with decomposition voltage higher than 4.5V. It does not readily catch fire or shrink, even under open flame, and shows no noticeable volumetric expansion or contraction at 80 °C, in stark contrast to most liquid-electrolytes-based or gel batteries. Even after cut off by one-third, the battery continues to function. The unique bi-functional molecular design of the polymer electrolyte, which guarantees simultaneously a very rare combination of thermal and mechanical stability, high ion conductivity, and a wide electrochemical window at room temperature, is the key factor responsible for the excellent comprehensive performances.