Positive electrode active material for secondary batteries, and secondary battery

Abstract

The present invention provides a positive electrode active material for secondary batteries, the positive electrode active material containing a lithium metal composite oxide that has a crystal structure based on a rock salt structure belonging to the space group Fm-3m. The lithium metal composite oxide contains at least one element A1 that is selected from the group consisting of Fe, Ca, Cr, Na, Al, Si, Mg, Cu, Zn, Pb, Sb and W. The content of the element A1 in the lithium metal composite oxide is 10 ppm by mass to 1,000 ppm by mass relative to the total amount of the lithium metal composite oxide. The lattice constant a, which shows the length of a crystal lattice of the lithium metal composite oxide in the a-axis direction, is 4.09 Å to 4.16 Å.