SECONDARY BATTERY

A secondary battery is provided and includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode current collector including aluminum and a positive electrode active material layer provided on the positive electrode current collector. The positive electrode active material layer includes a lithium-containing compound. The electrolytic solution includes an electrolyte, a solvent, and an additive. The electrolyte includes a bis(fluorosulfonyl)imide salt. The solvent includes at least one of an ethylene carbonate, a propylene carbonate, a fluoroethylene carbonate, a dimethyl carbonate, and a gamma butyrolactone. The additive includes at least one of a lithium fluorophosphate, a sulfinyl compound, and a dinitrile compound. The molar ratio of the original solvent to lithium ions, which is calculated from a vibration spectrum of the electrolytic solution, is more than 0 and 1.78 or less.