METHOD OF PRODUCING LITHIUM ION SECONDARY BATTERY

Provided is a method of producing a lithium ion secondary battery, the method including: a charge and discharge treatment step of subjecting a first lithium ion secondary battery including a positive electrode having a positive electrode active material layer containing a sulfur-modified compound, a first liquid electrolyte, and a negative electrode to charge and discharge treatment; and a replacement step of replacing the first liquid electrolyte with a second liquid electrolyte to provide a second lithium ion secondary battery after the charge and discharge treatment step, wherein the first liquid electrolyte contains a solvent selected from the group consisting of: a saturated cyclic carbonate compound; and a saturated chain carbonate compound, and wherein the second liquid electrolyte contains a solvent selected from the group consisting of: a saturated cyclic ether compound; and a saturated chain ether compound.