Provided is an electrolyte characterized by containing a heteroelement-containing organic solvent which comprises a specific organic solvent having a dielectric constant of 10 or less and/or a dipole moment of 5D or less. The heteroelement-containing organic solvent is contained at a molar ratio of 3 to 5 in terms of a metal salt where an alkali metal, alkaline earth metal, or aluminum serves as the cation, and the chemical structure represented by general formula (1) serves as the anion. General formula (1): (R1X1)(R2SO2)N