Polymer gel electrolyte, lithium ion battery and method for producing same

A method for producing a lithium ion battery, comprising:

• a step (A) of housing an electrode group comprising a positive electrode, a negative electrode and a separator in an outer package;
• a step (B) of injecting a pre-gel solution, which is a precursor of a polymer gel electrolyte, within the outer package, to impregnate the electrode group with the pre-gel solution to form a pre-battery;
• a step (C) of charging the pre-battery while keeping the state of the pre-gel solution;
• and
• a step (E) of gelatinizing the pre-gel solution by maintaining the pre-battery charged under warm temperature to form the polymer gel electrolyte,
• wherein the pre-gel solution comprises at least a lithium salt, an aprotic solvent and a polymer,
• an amorphous polymer layer derived from the polymer is formed on a surface of an electrode active material, and
• the polymer gel electrolyte comprises a crosslinked body of the polymer that is formed on the amorphous polymer layer.