LAUSR

Separators with low‐cost, superior mechanical properties, such as nanofiber materials, are considered a viable option for solving the dendritic problem in alkali metal batteries. Consuming the dendrites rather than blocking them underpins the long‐life stable cycle performance of the cell. Herein, a five‐layer structural separator (LiNO3@PVDF@mask) is presented, in which a mask is used as a framework and the polyvinylidene fluoride (PVDF) layer loaded with LiNO3 can generate a passivation layer by reacting with K dendrites. In the case of potassium metal batteries, for example, the LiNO3@PVDF@mask separator has excellent mechanical properties that can effectively cope with the hazards caused by the K dendrite. In addition, sustained‐release LiNO3 can react with penetrated K dendrites to form inactive substances like KNO3 and K2O, blocking further dendrite growth. Importantly, the LiNO3@PVDF@mask separator uses a low‐cost abundant mask and possesses excellent wettability of electrolyte with a reduced amount of liquid electrolyte, enabling one to further iron out cost problems. This study opens up a new direction for research and contributes to practical applications of flexible devices for rechargeable alkaline metal batteries.