REINFORCING SHEET FOR SOLID ELECTROLYTE MEMBRANE

The reinforcing sheet according to the present invention includes glass fibers and an organic binder that coats the glass fibers, and has voids to be filled with a solid electrolyte. The organic binder is (i) an organic polymer containing no element other than carbon, hydrogen and fluorine; or (ii) an organic polymer having a main chain and side chains, the main chain being perfluoroalkylene, and at least one of the side chains being terminated with a sulfonic acid group or a carboxylic acid group. The reinforcing sheet according to the present invention is suitable for improving the durability of a solid electrolyte membrane and maintaining the chemical stability thereof.