| abstract |
[SOLVING MEANS] Provided is a proton-conductive membrane including a crosslinked polymer and a plasticizer, wherein the crosslinked polymer includes a proton acceptor group in an amount equal to not less than 10 mol % of repeating units constituting the crosslinked polymer, the plasticizer includes a proton donor compound having a pKa value of not more than 2.5, and the plasticizer is a viscoelastic solid in a temperature range of 50° C. to 120° C. |