Positive electrode active material and nonaqueous electrolyte secondary battery using the same
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%.
1 . A positive electrode active material, comprising:
monoparticulate first lithium composite oxide particles; and
secondary particulate second lithium composite oxide particles, wherein
an average particle size (D50) of the secondary particulate second lithium composite oxide particles is larger than an average particle size (D50) of the monoparticulate first lithium composite oxide particles,
the secondary particulate second lithium composite oxide particles have a porosity of 0.9% to 4.0%,
an average primary particle size of the secondary particulate second lithium composite oxide particles is 1.2 μm to 2.5 μm,
a BET specific surface area of the secondary particulate second lithium composite oxide particles is 0.10 m 2 /g to 0.30 m 2 /g, and
a BET specific surface area of the monoparticulate first lithium composite oxide particles is 0.50 m 2 /g to 0.85 m 2 /g.
2 . The positive electrode active material according to claim 1 , wherein
each of the monoparticulate first lithium composite oxide particles and the secondary particulate second lithium composite oxide particles is particles of a lithium composite oxide containing Ni and having a layered structure.
3 . The positive electrode active material according to claim 2 , wherein
each of the monoparticulate first lithium composite oxide particles and the secondary particulate second lithium composite oxide particles is particles of a lithium nickel cobalt manganese composite oxide.
4 . The positive electrode active material according to claim 3 , wherein
a content of nickel in all metal elements except for lithium in the lithium nickel cobalt manganese composite oxide is 50 mol % or more.
5 . A nonaqueous electrolyte secondary battery, comprising:
a positive electrode;
a negative electrode; and
a nonaqueous electrolyte, wherein
the positive electrode includes a positive electrode active material including monoparticulate first lithium composite oxide particles; and
secondary particulate second lithium composite oxide particles,
an average particle size (D50) of the secondary particulate second lithium composite oxide particles is larger than an average particle size (D50) of the monoparticulate first lithium composite oxide particles,
the secondary particulate second lithium composite oxide particles have a porosity of 0.9% to 4.0%,
an average primary particle size of the secondary particulate second lithium composite oxide particles is 1.2 μm to 2.5 μm,
a BET specific surface area of the secondary particulate second lithium composite oxide particles is 0.10 m 2 /g to 0.30 m 2 /g, and
a BET specific surface area of the monoparticulate first lithium composite oxide particles is 0.50 m 2 /g to 0.85 m 2 /g.
6 . The positive electrode active material according to claim 1 , wherein
the average particle size (D50) of the second lithium composite oxide particles is 12 μm to 20 μm.
7 . The positive electrode active material according to claim 1 , wherein
the average particle size (D50) of the first lithium composite oxide particles is 2 μm to 6 μm.
8 . The positive electrode active material according to claim 6 , wherein
the average primary particle size of the secondary particulate second lithium composite oxide particles is an average diameter of primary particles of the secondary particulate second lithium composite oxide particles, and
the average particle size (D50) of the secondary particulate second lithium composite oxide particles is an average diameter of secondary particles of the secondary particulate second lithium composite oxide particles.
9 . The nonaqueous electrolyte secondary battery according to claim 5 , wherein
the average particle size (D50) of the second lithium composite oxide particles is 12 μm to 20 μm.
10 . The nonaqueous electrolyte secondary battery according to claim 5 , wherein
the average particle size (D50) of the first lithium composite oxide particles is 2 μm to 6 μm.
11 . The nonaqueous electrolyte secondary battery according to claim 9 , wherein
the average primary particle size of the secondary particulate second lithium composite oxide particles is an average diameter of primary particles of the secondary particulate second lithium composite oxide particles, and
the average particle size (D50) of the secondary particulate second lithium composite oxide particles is an average diameter of secondary particles of the secondary particulate second lithium composite oxide particles.