A SEPARATOR FOR A SECONDARY BATTERY

摘要

The present invention relates to a separation membrane for a secondary battery. More specifically, the present invention relates to a separation membrane for a secondary battery of which safety is improved as a contraction ratio of the separation membrane is enhanced in a high temperature condition. The separation membrane has a stratified structure in which a plurality of porous film layers are sequentially laminated, a draw ratio of each film layers is gradually or sequentially decreased as going from a center area to a surface area in a direction vertical to a laminated interface of the film layer. The separation membrane in accordance with the present invention has a low concentration ratio of the separation membrane even in a high temperature condition, and superior heat resistance and stability in dimension. Thus, there is an effect of enhancing high temperature stability of a battery produced by intervening the separation membrane in accordance with the present invention.