Provided is a secondary battery which uses a heat generating reaction of the redox shuttle agent to achieve stopping a function of the battery by blocking ion conduction and rapidly increasing an internal resistance by means of volatilized non-aqueous solvent when an abnormality such as overcharge occurs. A secondary battery 1 comprises a battery element comprising a positive electrode 11, a negative electrode 12, a separator 13, and an electrolytic solution, and a casing sealing the battery element. The electrolytic solution comprises a redox shuttle agent and an organic solvent having a boiling point of 125° C. or less. The separator 13 comprises aramid fiber assembly, aramid microporous structure, polyimide microporous structure or polyphenylenesulfide microporous structure, and polyphenylenesulfide, and has an average void size of 0.1 μm or more.