Nonaqueous electrolyte secondary battery

A nonaqueous electrolyte secondary battery comprising:

• an electrode assembly including a negative plate and a positive plate including a positive electrode active material mix layer containing a positive electrode active material;
• a nonaqueous electrolyte;
• a battery case that houses the electrode assembly and the nonaqueous electrolyte;
• and
• a pressure-sensitive safety system that operates when the pressure in the battery case reaches a value greater than or equal to a predetermined value,
• wherein the nonaqueous electrolyte contains an electrolyte salt containing fluorine, the positive electrode active material mix layer contains lithium carbonate and lithium phosphate, the average particle size of lithium carbonate contained in the positive electrode active material mix layer is greater than the average particle size of lithium phosphate contained in the positive electrode active material mix layer, and the number of particles of lithium carbonate contained in the positive electrode active material mix layer is less than the number of particles of lithium phosphate contained in the positive electrode active material mix layer, and
• wherein the average distance between the neighboring lithium carbonate particles and lithium phosphate particles in the positive electrode active material mix layer is 4 μm to 20 μm.