Separator including density-controlled coating layer and battery including the same

Disclosed herein is a separator for batteries. The separator includes a coating layer formed on a base film to have a density of 1.2 g/mto 2 g/musing a coating agent containing a polyvinylidene fluoride homopolymer and inorganic particles having an average particle size of 1 nm to 700 nm, thereby providing a slim structure while ensuring high peel strength and strong adhesion to electrodes. Further, a battery including the separator is disclosed. The battery has high stability and long lifespan.