Electrolyte membrane and preparation method thereof

A preparation method of an electrolyte membrane, comprising:

• mixing a first polymer, an ionic liquid, and an organic solvent to obtain a first solution;
• adding solid electrolyte to the first solution to obtain a slurry A;
• mixing at least one type of second polymers to obtain a polymer mixture, wherein a weight-average molecular weight of each of the at least one type of second polymers is different from each other;
• mixing the polymer mixture, the ionic liquid, and the organic solvent to obtain colloid liquid B;
• dividing the slurry A into partial batches and adding each of the partial batches of the slurry A to the colloid liquid B to obtain an intermediate colloid C;
• wherein a mixture of the slurry A and the colloid liquid B is stirred for a period of time after each of the partial batches of the slurry A is added to the colloid liquid B, and a pH of the mixture of the slurry A and the colloid liquid B is maintained to be 6.8 to 7.5;
• mixing lithium salt and the ionic liquid with the organic solvent to obtain a composite solution;
• mixing the intermediate colloid C with the composite solution to obtain a composite;
• and
• applying the composite onto a substrate and drying the composite to form the electrolyte membrane.