SEPARATOR FOR ELECTROCHEMICAL ELEMENT, ELECTROCHEMICAL ELEMENT, AUTOMOBILE, AND ELECTRONIC DEVICE

A separator for an electrochemical element, the separator being interposed between a pair of electrodes and configured to be capable of holding an organic electrolytic solution that contains an electrolyte. The separator is a wet-laid nonwoven fabric that contains 10 to 50 mass% of thermoplastic synthetic fibers and 50 to 90 mass% of beaten regenerated cellulose fibers having a mean fiber length of 0.2 to 2.0 mm, and the separator has a thickness of 10 to 70 µm and a density of 0.25 to 0.90 g/cm 3 , including two parts obtained by bisecting a cross-section of the separator in a thickness direction. The two parts are a part (A part) with a small number of the thermoplastic synthetic fibers and a part (B part) with a large number of the thermoplastic synthetic fibers, and the A part and the B part are formed into a single layer in an integrated manner. A value obtained by dividing the number of the thermoplastic synthetic fibers in the A part by the number of the thermoplastic synthetic fibers in the B part is 0.85 or less.