| 摘要 |
PROBLEM TO BE SOLVED: To provide a base material for a lithium ion secondary battery separator high in processability, strength, uniformity, and post-process handleability when a coating layer containing inorganic particles is formed on an unwoven fabric surface.SOLUTION: A base material for a lithium ion secondary battery separator includes a coating layer containing inorganic particles on at least one surface of an unwoven fabric made of synthetic resin short fibers. The average fiber diameter of the entire unwoven fabric made of the synthetic resin short fibers is equal to or less than 5.5 μm, the average fiber diameter of fibers constituting the surface of one surface of the unwoven fabric and the average fiber diameter of fibers constituting the surface of an opposite surface are different from each other, and the ratio R=D(W)/D(T) of the average fiber diameter D(W) of the surface having a large average fiber diameter with the average fiber diameter D(T) of the surface having a small average fiber diameter is equal to or higher than 1.10, more preferably, 1.30 to 2.50. Preferably, the base material for the lithium ion secondary battery separator includes synthetic resin short fibers each having a length of 1 mm or lower. |
