Positive electrode active material for non-aqueous electrolyte secondary battery, process for manufacturing positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery using the positive electrode active material

1. A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium metal composite oxide,

wherein the lithium metal composite oxide is represented by a general formula: Li a Ni 1-x-y-z Co x D y E z O 2 wherein, in the formula, 0.05≤x≤0.35, 0≤y≤0.35, 0.002≤z≤0.05, 1.00≤a≤1.30, an element D is at least one type of element selected from Mn, V, Mo, Nb, Ti, and W, and an element E is an element forming an alloy with lithium at a potential more noble than a potential in which ions of the element E are reduced, the element E being Si, or Si in combination with at least one of Mg and Al, wherein the lithium metal composite oxide comprises primary particles and secondary particles formed by aggregating the primary particles,

wherein an oxide containing the element E exists at a surface of at least either of the primary particles and the secondary particles.

2. The positive electrode active material for the non-aqueous electrolyte secondary battery according to claim 1 , wherein at least a part of the element E of the lithium metal composite oxide is solid-solved in the primary particles or the secondary particles.

3. A non-aqueous electrolyte secondary battery comprising:

a positive electrode;

a negative electrode;

a separator; and

a non-aqueous electrolyte,

wherein the positive electrode includes the positive electrode active material for the non-aqueous electrolyte secondary battery according to claim 1 as a constituent material.

4. The non-aqueous electrolyte secondary battery according to claim 3 , wherein an alloy of the element E and lithium exists at a surface of the negative electrode after charging and discharging.

5. The non-aqueous electrolyte secondary battery according to claim 4 , wherein the element E contained in the negative electrode after charging and discharging is 50 mass ppm or more and 600 mass ppm or less with respect to the negative electrode.

6. A process for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium metal composite oxide, wherein the lithium metal composite oxide is represented by a general formula: Li a Ni 1-x-y-z Co x D y E z O 2 wherein, in the formula, 0.05≤x≤0.35, 0≤y≤0.35, 0.002≤z≤0.05, 1.00≤a≤1.30, an element D is at least one type of element selected from Mn, V, Mo, Nb, Ti, and W, and an element E is an element forming an alloy with lithium at a potential more noble than a potential in which ions of the element E are reduced, the element E being Si, or Si in combination with at least one of Mg and Al, wherein the lithium metal composite oxide comprises primary particles and secondary particles formed by aggregating the primary particles,

wherein the process comprises:

a crystallization step for crystallizing transition metal composite hydroxide particles by supplying and mixing an aqueous solution at least containing nickel and cobalt, an aqueous solution containing ammonium ion donor, and an alkaline solution, in a reaction tank;

a mixing step for mixing a transition metal composite hydroxide obtained by the crystallization step, a compound containing the element E, and a lithium compound; and

a firing step for firing a lithium mixture obtained by the mixing step at a temperature of 700° C. to 1000° C. and forming the lithium metal composite oxide,

wherein an oxide containing the element E is formed at a surface of at least either of the primary particles and the secondary particles by the mixing step.