(EN) A polymer electrolyte composition comprising a mixed solvent including a plurality of solvents with boiling points differing from one another, and a block copolymer-type polymer electrolyte comprising a block having an ion-exchange group and a block having substantially no ion-exchange groups, wherein the mixed solvent is a good solvent of the block copolymer-type polymer electrolyte, and a solvent A having the highest boiling point of the solvents included in the mixed solvent is a poor solvent of the block copolymer-type polymer electrolyte and good solvent of the block having the ion-exchange group.
