Secondary battery

A secondary battery, comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the positive electrode active material comprises a manganese-based material, and the non-aqueous electrolyte comprises a solvent, an electrolyte salt and an additive, and the additive comprises a compound represented by structural formula 1:

• wherein n is 0 or 1, A is selected from C or O, X is selected from
• R1 and R2 are each independently selected from H,
• R1 and R2 are not selected from H at the same time, and at least one of X, R1 and R2 comprises at least one sulfur atom;
• the secondary battery meets the following requirements:
• 0.73≤100×W×u/(q×s)≤4;
• and 2.0 g/Ah≤W≤3.15 g/Ah, 0.05%≤u≤3.0%, 12%≤q≤58%, 12 mg/cm2≤s≤25 mg/cm2;
• wherein W is a ratio of mass of the non-aqueous electrolyte to rated capacity of the secondary battery, and the unit is g/Ah;
• u is a percentage mass content of the compound represented by structural formula 1 in the non-aqueous electrolyte, and the unit is %;
• q is a percentage mass content of manganese in the positive electrode material layer, and the unit is %;
• s is a surface density of one side of the positive electrode material layer, and the unit is mg/cm2.