The present application relates to a separator, comprising: two layers of substrate and a coating formed between the two layers of substrate, wherein the coating contains inorganic particles, and 30 wt% to 70 wt% of the inorganic particles have a surface coated with a coating layer, and 70 wt% to 30 wt% of the inorganic particles have an uncoated surface, based on the total weight of the inorganic particle. The separator may realize a high mechanical strength, a high wettability, and a good interfacial bonding, and may also effectively inhibit the growth of lithium dendrites, and thus improve the cycling performance of a secondary battery.