Patent ID: 7838138

Claim:
An electrolyte membrane comprising: a fluorinated acid that contains 20 acid-functional groups or less per molecule and has a molecular weight of less than 10,000, wherein, after being heated from 1° C. to 200° C. at a ramp rate of 10° C./minute, and then cooled to 120° C. within 5 minutes, the fluorinated acid exhibits a cumulative mass loss of about 6% or less, based on an initial weight of the fluorinated acid, while being maintained at 120° C. for a 24 hour period, the cumulative mass loss being measured during the 24 hour period, and wherein the electrolyte membrane contains less than about 60% by weight phosphoric acid; and a basic polymer protonated by the fluorinated acid, wherein the basic polymer retains at least about 90% of original functional groups of the basic polymer and at least about 90% of an original molecular weight of the basic polymer when the electrolyte membrane is subjected to an environmental temperature of 85° C. and an environmental relative humidity of 95% for 100 hours.