| CPC H01M 4/131 (2013.01) [C01G 53/42 (2013.01); H01M 4/0471 (2013.01); H01M 4/364 (2013.01); H01M 4/366 (2013.01); H01M 4/505 (2013.01); H01M 4/525 (2013.01); H01M 10/0525 (2013.01); C01P 2002/50 (2013.01); C01P 2004/03 (2013.01); C01P 2004/51 (2013.01); C01P 2004/62 (2013.01); C01P 2004/64 (2013.01); C01P 2006/10 (2013.01); C01P 2006/12 (2013.01); C01P 2006/40 (2013.01); H01M 2004/021 (2013.01); H01M 2004/028 (2013.01)] | 15 Claims |

|
1. A positive electrode active material for a lithium ion secondary battery, the positive electrode active material having a mole ratio among lithium (Li), nickel (Ni), cobalt (Co), an element M, and tungsten (W) of Li:Ni:Co:M:W=a:(1−x−y):x:y:z (in which 0≤x≤0.35, 0≤y≤0.35, 0.005≤z≤0.030, 0.97≤a≤1.25, and the element M represents at least one element selected from the group consisting of Mn, V, Mg, Mo, Nb, Ti, and Al), wherein
the positive electrode active material comprises: a lithium-metal composite oxide which comprises primary particles and secondary particles formed of a plurality of the primary particles which are aggregated together; and a compound containing lithium and tungsten present on surfaces of the primary particles,
an amount of tungsten contained in the compound containing lithium and tungsten is 0.5 atom % or more and 3.0 atom % or less in terms of a ratio of a number of atoms of W with respect to a total number of atoms of Ni, Co, and the element M, and
a conductivity when the positive electrode active material is compressed to 4.0 g/cm3 as determined by powder resistance measurement is 6×10−3 S/cm or less.
|