Positive electrode active material, secondary battery, and electronic device

Abstract

The breakage or cracking of a positive electrode active material due to pressure application, repeated charging and discharging, or the like is likely to cause dissolution of a transition metal, an excessive side reaction, and the like. With a crack, unevenness, a step, roughness, or the like on the surface of a positive electrode active material, stress tends to be concentrated on part, which easily causes breakage. By contrast, with a smooth surface and a nearly spherical shape, stress concentration is alleviated; thus, breakage is unlikely to occur. Therefore, a positive electrode active material with a smooth surface and little unevenness is formed. For example, when the positive electrode active material is subjected to image analysis using a microscope image, the median value of the solidity is larger than or equal to 0.96. Alternatively, the median value of the fractal dimension of the positive electrode active material is smaller than or equal to 1.143. Alternatively, the median value of the circularity of the positive electrode active material is larger than or equal to 0.7.

Dependencies are inferred from the claim text.