The present invention pertains to a lithium ion secondary battery comprising a positive electrode and a non-aqueous electrolyte including a non-aqueous electrolyte solvent. The lithium ion secondary battery is characterized by: the positive electrode including a positive electrode active substance having an operating potential of at least 4.5 V relative to lithium metal; the non-aqueous electrolyte solvent including a fluorinated organophosphate indicated by a prescribed formula and at least one type selected from a group comprising sulfonic compounds indicated by the prescribed formula; and by including at least 5 vol% of sulfonic compound in the non-aqueous electrolyte solvent.