Positive electrode active material for non-aqueous electrolyte secondary battery and method for producing the same, and non-aqueous electrolyte secondary battery and method for producing the same
The positive electrode active material is for a non-aqueous electrolyte secondary battery, suppressing deterioration of battery characteristics due to exposure to the atmosphere and having excellent battery capacity. A positive electrode active material for a non-aqueous electrolyte secondary battery includes a lithium-nickel composite oxide represented by general formula (1): Li a Ni 1−x−y Co x M y O 2+α (in which 0.05≤x≤0.35, 0≤y≤0.10, 0.95≤a≤1.10, 0≤a≤0.2, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al) and Li 3 BO 3 . At least a part of a surface of the lithium-nickel composite oxide is coated with Li 3 BO 3 . The content of boron in the positive electrode active material is 0.001% by mass or more and 0.2% by mass or less with respect to the entire positive electrode active material.
1. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a lithium-nickel composite oxide represented by general formula (1): Li a Ni 1−x−y Co x M y O 2+α (in which 0.05≤x≤0.35, 0≤y≤0.10, 0.95≤a≤1.10, 0≤α≤0.2, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al) and Li 3 BO 3 , the method comprising:
mixing a boron compound, at least one of a nickel composite hydroxide and a nickel composite oxide, and a lithium compound to obtain a lithium mixture; and
firing the lithium mixture in an oxygen atmosphere at a temperature of 715° C. or higher and 850° C. or lower to obtain a lithium-nickel composite oxide, wherein
the boron compound is mixed in an amount such that the content of boron is 0.001% by mass or more and 0.2% by mass or less with respect to the entire positive electrode active material, and
at least a part of a surface of the obtained lithium-nickel composite oxide is coated with Li 3 BO 3 ,
a diffraction peak of Li 3 BO 3 is only detected as a diffraction peak other than that derived from the lithium-nickel composite oxide in powder X-ray diffraction, and
the method is conducted without a step of reducing the content of boron from the lithium-nickel complex oxide such that the content of boron from the lithium mixture is maintained in the entire lithium-nickel complex oxide produced by the method.
2. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the boron compound contains at least one selected from H 3 BO 3 , B 2 O 3 , and LiBO 2 .
3. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the lithium compound contains lithium hydroxide.
4. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein at least a part of a surface of the lithium-nickel composite oxide is coated with Li 3 BO 3 alone.