A separator includes a porous substrate having a plurality of pores; and a porous coating layer formed on at least one surface of the porous substrate and made of a mixture of a binder and a plurality of inorganic particles, wherein the binder includes a crosslinked binder. This separator may improve high temperature cycle performance, discharge characteristics and thermal resistance of an electrochemical device since the separator exhibits improved insolubility and impregnation to electrolyte and improved thermal resistance.