Separator including coating layer containing high and low density inorganic particles and particle binder resin and method for manufacturing the same

A separator for an electrochemical device, comprising:

• a porous separator substrate;
• and
• a coating layer on at least one surface of the porous separator substrate,
• wherein the coating layer comprises first inorganic particles, second inorganic particles, and a particulate binder resin,
• wherein a ratio of a density of the particulate binder resin to a density of the first inorganic particles is equal to or more than 0.2 and less than 0.33,
• wherein a ratio of a density of the particulate binder resin to a density of the second inorganic particles ranges from 0.33 to 0.5,
• wherein the coating layer comprises a first layer adjacent to the porous separator substrate and a second layer on a surface of the first layer,
• wherein the first layer comprises at least some of the first inorganic particles,
• wherein the second layer comprises at least some of the second inorganic particles,
• wherein the second layer has a larger thickness as compared to the first layer, and
• wherein the second inorganic particles comprise at least one selected from the group consisting of aluminum hydroxide (Al(OH)3) and Mg(OH)2.