COMPOSITE POLYMER ELECTROLYTE MEMBRANE, MEMBRANE ELECTRODE ASSEMBLY AND SOLID POLYMER FUEL CELL USING SAME

A composite polymer electrolyte membrane has a high proton conductivity even under low-humidity, low-temperature conditions, a reduced dimensional change rate, a high mechanical strength and high chemical stability, and produces a solid polymer electrolyte fuel cell with a high output and high physical durability, a membrane electrode assembly, and a solid polymer electrolyte fuel cell containing the same. This composite polymer electrolyte membrane contains a composite layer composed mainly of a polyazole-containing nanofiber nonwoven fabric (A) and an ionic group-containing polymer electrolyte (B), the polyazole-containing nanofiber nonwoven fabric (A) being basic.