USE OF AN ELECTROLYTE CONTAINING AN ALUMINUM SALT AND A SULFONE COMPOUND IN A SECONDARY BATTERY

A secondary battery capable of decreasing progression temperature of a precipitation-dissolution reaction of aluminum is provided. A cathode 11 and an anode 12 are separated from each other by a separator 13. An electrolyte with which the separator 13 is impregnated contains an alkyl sulfone (R1-S(=O) 2 -R2: each of R1 and R2 represents an alkyl group) and a solvent (having a specific dielectric constant of 20 or less) together with an aluminum salt. A content of the solvent is equal to or larger than 30 mol% and is less than 88 mol%, and a mol ratio (a content of the aluminum salt/a content of the alkyl sulfone) is equal to or larger than 4/5 and is less than 7/3.