Polymer electrolyte membrane, manufacturing method therefor, and membrane electrode assembly comprising same

A polymer electrolyte membrane comprising a porous support and an ion conductor with which pores of the porous support are filled, wherein

• at a temperature of 80° C. and a relative humidity (RH) of 50%, the polymer electrolyte membrane has an in-plane (IP) proton conductivity of 0.046 S/cm to 0.1 S/cm and a through-plane (TP) proton conductivity of 0.042 S/cm to 0.1 S/cm, and
• each of an MD swelling ratio and a TD swelling ratio of the polymer electrolyte membrane calculated by Equation 1 and Equation 2 below after the polymer electrolyte membrane is immersed in distilled water of room-temperature for 12 hours and then dried in a vacuum state at 50° C. for 24 hours is 2% or less.
• ΔL(MD)=[(Lwet(MD)−Ldry(MD))/Ldry(MD)]×100 [Equation 1]
• ΔL(TD)=[(Lwet(TD)−Ldry(TD))/Ldry(TD)]×100 [Equation 2]
• where ΔL(MD) is an MD swelling ratio, ΔL(TD) is a TD swelling ratio, Lwet(MD) and Lwet(TD) are an MD length and a TD length measured immediately before the drying, respectively, and Ldry(MD) and Ldry(TD) are an MD length and a TD length measured immediately after the drying, respectively.

A method of manufacturing a polymer electrolyte membrane, the method comprising:

• casting a first mixed liquid comprising a first ion conductor;
• placing a first porous support of a dry state on the first mixed liquid such that the first porous support is entirely brought into a wet state;
• adding a second porous support of a dry state on the first porous support immediately after the first porous support is entirely brought into the wet state such that the first and second porous supports are in contact with each other;
• applying a second mixed liquid comprising a second ion conductor onto the second porous support such that the second porous support is entirely brought into a wet state;
• and
• drying the first and second porous supports of the wet state.