The present application relates to a separator, comprising a substrate and a coating formed on at least one surface of the substrate, wherein the coating comprises inorganic particles and first organic particles embedded in the inorganic particles and forming protrusions on the surface of the coating, and the first organic particles have a primary particle morphology and a number-average particle size of ≥2 μm. The present application also relates to a secondary battery comprising the separator, a device comprising the secondary battery and a method for preparing the separator.