NOVELTY - A lithium-ion secondary battery has a positive electrode (5) containing positive-electrode active material which occludes-discharges lithium ion, a negative electrode (6) containing negative-electrode active material which occludes-discharges lithium ion, and separator (7) arranged between the positive and negative electrodes. The positive-electrode active material has composite coating layer which covers the surface of a lithium-transition metal oxide. The composite coating layer contains oxide or fluoride of molybdenum, tungsten and zirconium, and a phosphoric acid compound.    USE - Lithium-ion secondary battery. Uses include but are not limited to mobile telephone, personal notebook computer, electric vehicle and hybrid electric vehicle.    ADVANTAGE - The lithium-ion secondary battery has high capacity, and excellent safety, cycle characteristics and thermal stability at the time of overcharge.    DETAILED DESCRIPTION - A lithium-ion secondary battery has a positive electrode containing positive-electrode active material which occludes-discharges lithium ion, a negative electrode containing negative-electrode active material which occludes-discharges lithium ion, and separator arranged between the positive and negative electrodes. The positive-electrode active material has composite coating layer which covers the surface of a lithium-transition metal oxide. The composite coating layer contains oxide or fluoride of molybdenum, tungsten and zirconium, and a phosphoric acid compound. The average atomic concentration from the center along thickness direction of the composite coating layer to the lithium transition metal oxide is higher than the average atomic concentration from the center along thickness direction of the composite coating layer to the electrolyte, based on the atomic concentration of molybdenum, tungsten and zirconium contained in the composite coating layer.    DESCRIPTION OF DRAWING(S) - The drawing shows an expanded view of laminated electrode group.    Positive electrode terminal (1)    Negative electrode terminal (2)    Positive electrode (5)    Negative electrode (6)    Separator (7)