Abstract: The positive electrode active material disclosed here includes: first lithium composite oxide particles in the form of single particles; and second lithium composite oxide particles in the form of secondary particles. When in a volume-based particle size distribution obtained by a laser diffraction scattering method, a 10%-particle size (D10) is a particle size with a cumulative frequency of 10%, a 50%-particle size (D50) is a particle size with a cumulative frequency of 50%, and a 90%-particle size (D90) is a particle size with a cumulative frequency of 90%, a 50%-particle size of the second lithium composite oxide particles is larger than that of the first lithium composite oxide particles, and a particle size distribution width of the second lithium composite oxide particles expressed by (D90-D10)/D50 is 0.50 to 0.65.

Abstract: Provided is a positive electrode active material that can provide a nonaqueous electrolyte secondary battery with high gas generation suppressing performance during storage and high output characteristics. The positive electrode active material includes monoparticulate first lithium composite oxide particles and secondary particulate second lithium composite oxide particles. The first and second lithium composite oxide particles contain Ni and have layered crystal structures. A median particle size D250 of the second lithium composite oxide particles is larger than a median particle size D150 of the first lithium composite oxide particles. An average primary particle size d1 of the first lithium composite oxide particles obtained by scanning electron microscope observation is less than 2.0 ?m. A ratio of the average primary particle size d1 of the first lithium composite oxide particles to the median particle size D150 of the first lithium composite oxide particles is 0.45 to 0.60.

Abstract: Provided is a positive electrode that can provide a nonaqueous electrolyte secondary battery with high gas generation suppressing performance during storage and high cycle characteristics. The positive electrode disclosed here includes a positive electrode current collector and a positive electrode active material layer supported by the positive electrode current collector. The positive electrode active material layer includes monoparticulate first Ni-containing lithium composite oxide particles and secondary particulate second Ni-containing lithium composite oxide particles. The first Ni-containing lithium composite oxide particles and the second Ni-containing lithium composite oxide particles have layered crystal structures. The first Ni-containing lithium composite oxide particles have an average particle size (D50) of 2 ?m to 6 ?m. The second Ni-containing lithium composite oxide particles have an average primary particle size of 1.2 ?m to 2.0 ?m.

Abstract: Provided is a positive electrode active material that can increase a volume capacity density of a positive electrode of a nonaqueous battery secondary battery and can provide the nonaqueous electrolyte secondary battery with high cycle characteristics. A positive electrode active material disclosed here includes monoparticulate first lithium composite oxide particles and secondary particulate second lithium composite oxide particles. An average particle size of the second lithium composite oxide particles is larger than an average particle size of the first lithium composite oxide particles. The second lithium composite oxide particles have a porosity of 0.9% to 4.0%.

Abstract: A secondary battery includes a positive electrode including a positive electrode core; and a positive electrode mixture layer formed on at least one of the surfaces of the positive electrode core. The positive electrode mixture layer has a first positive electrode mixture layer and a second positive electrode mixture layer formed om the surface of the first positive electrode mixture layer. The first positive electrode mixture layer contains a first positive electrode active material having a BET specific surface area of 1.6 m2/g to 2.8 m2/g, and the second positive electrode mixture layer contains a second positive electrode active material having a BET specific surface area of 0.8 m2/g to 1.3 m2/g. The thickness of the second positive electrode mixture layer is 5 ?m to 15 ?m.