SECONDARY BATTERY

This secondary battery comprises a battery element that includes a positive electrode, a negative electrode, and an electrolyte, a storage member that stores said battery element in an interior thereof, and an electric current blocking mechanism that operates in accordance with an increase in pressure in the interior of said storage member and that blocks the energization of the battery element. The positive electrode includes a lithium iron phosphate compound represented by formula (1). The electrolyte includes a solvent and an electrolyte salt. The solvent has a boiling point of 100°C or greater, and includes a chain carboxylic acid ester having a viscosity of 0.9 mPa・s or less at 25°C. The electrolyte salt includes a lithium sulfonylimide salt represented by formula (2). The operation pressure of the electric current blocking mechanism is 20 kgf/cm2 or greater. Formula (1): LiFex M1-x PO4 (M is one or two or more transition metal elements (not including Fe); x satisfies the expression 0