SEPARATOR IN WHICH DOUBLE COATING LAYER IS FORMED AND SECONDARY BATTERY COMPRISING SAME

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