Thermally Stable and Dendrite‐Resistant Separators toward Highly Robust Lithium Metal Batteries

High‐level safety is of vital importance to the continuous pursuit of high‐energy‐density batteries in the increasingly electrified world. The thermal instability and dendrite‐induced issues of conventional polypropylene (PP) separators often cause internal short circuits and thermal runaway in batteries. Herein, a thermally stable and dendrite‐resistant separator (F‐PPTA@PP) is constructed using a dual‐functional and easy‐to‐commercialize design strategy of thermally safe poly‐p‐phenylene‐terephthamide nanofibers and plasma‐induced lithiophilic fluorine‐containing groups. In situ thermal monitoring, in situ optical observation, and multiphysics simulation demonstrate that F‐PPTA@PP can suppress thermal shrinkage of the separator and the formation of hotspots, and also promote uniform lithium deposition. Subsequently, lithium metal batteries are assembled, featuring an initial capacity of 194.1 mAh g –1 at 0.5 C with a low‐capacity attenuation of 0.02% per cycle over 1000 cycles. When operating under extreme conditions, i.e., −10 and 100 °C, ultrafast charging/discharging rates up to 30 C, lean electrolyte (2.4 µL mg –1 )/high mass‐loading (10.77 mg cm –2 ) or lithium‐sulfur batteries, F‐PPTA@PP separator still enables competitive electrochemical performance, highlighting its plausible processing scalability for high‐safety energy storage systems.