| CPC H01M 4/485 (2013.01) [C01G 53/40 (2013.01); C01G 53/42 (2013.01); H01M 4/131 (2013.01); H01M 4/1391 (2013.01); C01P 2002/52 (2013.01); H01M 2004/028 (2013.01)] | 16 Claims |

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1. A positive electrode active material, comprising:
secondary particles each composed of an aggregate of primary particles that contain a lithium transition metal composite oxide having a layered structure and a composition ratio of a number of moles of nickel to a total number of moles of metals other than lithium of from 0.7 to less than 1,
wherein a compound containing boron is attached on at least a part of surfaces of the primary particles,
a compound containing sodium is present in at least a part of particle boundaries of the secondary particles,
a sodium element content is in a range of from 150 ppm to 1300 ppm and
a ratio of a number of moles of boron element relative to the total number of moles of metals other than lithium in the lithium transition metal composite oxide is in a range of from 0.1% by mole to 2% by mole.
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