Patent ID: 10522832

Abstract:
A secondary battery includes a positive electrode including a positive electrode active material which includes a center portion including a lithium composite oxide including cobalt and an element M, and a covering portion that is provided on at least a portion of a surface of the center portion and contains lithium, nickel, and manganese elements. A concentration thereof has a gradient in a direction from a surface toward a center of the positive electrode active material. A first molar fraction satisfies 0.03<R<0.13 at a first position within the covering portion where the proportion D satisfies D=0.05. A second molar fraction satisfies 0.01<R<0.13 at a second position within the center portion where the proportion D satisfies D=0.3. A ratio F of the second molar fraction to the first molar fraction satisfies 0.7≤F≤1.