SEPARATOR COMPRISING DUAL COATING LAYERS AND SECONDARY BATTERY COMPRISING THE SAME

A separator having a polyolefin substrate, first coating layer including first inorganic particles on at least one surface of the polyolefin substrate and a second coating layer including second inorganic particles on a surface of the first coating layer opposite the polyolefin substrate, An average particle size of the first inorganic material particles of the first coating layer is greater than an average particle size of the second, inorganic material particles of the second coating layer. The first inorganic particles of the first coating layer are 900 nm or more based on. D50, and the second inorganic particles of the second coating layer are 10 nm or more and 500 nm or less based on D50.