Separator including porous polymer substrate and porous coating layer containing inorganic particles and binder polymer, and method for manufacturing the same

A separator for an electrochemical device, comprising:

• a porous polymer substrate;
• and
• a porous coating layer on at least one surface of the porous polymer substrate, wherein the porous coating layer comprises inorganic particles and a binder polymer,
• wherein the porous coating layer comprises a first region that is in contact with the porous polymer substrate and a second region on an opposite side of the first region that is not in contact with the porous polymer substrate,
• wherein the binder polymer present in the first region has a concentration gradient increasing from the porous polymer substrate toward an outermost surface of the porous coating layer,
• wherein the binder polymer present in the second region has a concentration gradient increasing from the porous polymer substrate toward the outermost surface of the porous coating layer,
• wherein the concentration gradient of the binder polymer present in the second region has a larger slope than a slope of the concentration gradient of the binder polymer present in the first region, and
• wherein a weight ratio of the inorganic particles to the binder polymer in each of the first region and the second region is 90:10 to 50:50.