Secondary battery

Abstract

The present invention provides a highly safe secondary battery. The secondary battery comprises a positive electrode, wherein: the positive electrode includes positive electrode active material particles and a fibrous conductive material; the positive electrode active material particles contain lithium cobalt oxide; the positive electrode active material particles each have a surface layer part that has a rock salt type crystal structure and an internal part that has a layered rock salt type crystal structure; the surface layer part contains cobalt, nickel, magnesium, and fluorine; the internal part contains cobalt and aluminum, and in a planar view of the positive electrode or a cross-sectional view of the positive electrode, there is a region where the fibrous conductive material surrounds substantially all of the positive electrode active material particles.