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,

• wherein 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/cm3, including two parts obtained by bisecting a cross-section of the separator in a thickness direction,
• wherein 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,
• wherein 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.