Electrolyte membrane comprising nanocomposite ion complex, manufacturing method thereof, and fuel cell including the same

An electrolyte membrane includes a nanocomposite ion complex that is a reaction product of a nanocomposite with a basic polymer. The nanocomposite includes a polymer having a sulfonic acid group and an unmodified clay. Either the unmodified clay has a layered structure and is dispersed in the polymer having the sulfonic acid group, and the polymer is intercalated between layers of the clay or the unmodified clay has an exfoliated structure and the exfoliated layers of the unmodified clay are dispersed in the polymer. The electrolyte membrane shows high mechanical strength, high ionic conductivity, and excellent methanol crossover impeding properties even when the degree of sulfonation of the polymer having the sulfonic acid group is high. When a methanol aqueous solution is used as a fuel, the fuel cell including the electrolyte membrane has a low methanol crossover, and thus, has a high operational efficiency and a long lifetime.