Lithium-ion secondary battery

Abstract

A positive electrode active material that inhibits a decrease in discharge capacity in charge and discharge cycles and a secondary battery using the positive electrode active material are provided. Alternatively, a highly safe secondary battery is provided. A lithium-ion secondary battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer over the positive electrode current collector. The negative electrode includes a negative electrode current collector and a negative electrode active material layer over the negative electrode current collector. In a region where the positive electrode current collector and the negative electrode current collector face each other, the positive electrode active material layer contains a positive electrode active material, the positive electrode active material has a layered rock-salt crystal structure belonging to the space group R-3m, and an angle formed by the normal of the negative electrode current collector and the c-axis of the crystal structure of 50% or more of the number of particles of the positive electrode active material in the positive electrode active material layer is greater than or equal to 60° and less than or equal to 120°. As the positive electrode active material, lithium cobalt oxide or lithium nickel-cobalt-manganese oxide can be used.

Dependencies are inferred from the claim text.