Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes primary particles that each include a lithium-manganese phosphate compound and have an average particle diameter of less than or equal to 100 nm. The negative electrode has an electrochemical capacity per unit area of less than or equal to an electrochemical capacity per unit area of the positive electrode.

Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is provided on the positive electrode current collector and includes an electrically conductive substance. The electrically conductive substance includes electrically conductive supports and electrically conductive particles. The electrically conductive supports each include a carbon material. The electrically conductive particles are supported by the electrically conductive supports. The electrically conductive particles are primary particles that each include a lithium phosphate compound and have an average particle size of less than 35 nanometers.