Nickel cobalt complex hydroxide particles and method for producing the same, positive electrode active material for non-aqueous electrolyte secondary battery and method for producing the same, and non-aqueous electrolyte secondary battery
A method for producing a nickel cobalt complex hydroxide includes first crystallization of supplying a solution containing Ni, Co and Mn, a complex ion forming agent and a basic solution separately and simultaneously to one reaction vessel to obtain nickel cobalt complex hydroxide particles, and a second crystallization of, after the first crystallization, further supplying a solution containing nickel, cobalt, and manganese, a solution of a complex ion forming agent, a basic solution, and a solution containing said element M separately and simultaneously to the reaction vessel to crystallize a complex hydroxide particles containing nickel, cobalt, manganese and said element M on the nickel cobalt complex hydroxide particles crystallizing a complex hydroxide particles comprising Ni, Co, Mn and the element M on the nickel cobalt complex hydroxide particles.
1. A nickel cobalt complex hydroxide represented by a formula:
Ni 1-x-y Co x Mn y M z (OH) 2+a , wherein 0.10≤x≤0.35, 0≤y≤0.35, 0<z≤0.05, 0≤a≤0.5, M is at least one element selected from a group consisting of Al, Mg, Ca, Ti, Zr, Nb, Ta, Cr, Mo, W, Fe, Cu, Si, Sn, Bi, Ga, Y, Sm, Er, Ce, Nd, La, Cd and Lu,
wherein the nickel cobalt complex hydroxide is in a form of secondary particles formed by agglomeration of primary particles,
wherein the secondary particles comprises:
a first layer having a radial depth ratio of less than 5% from a surface in the secondary particles;
a second layer having a radial depth ratio in a range of 5% to less than 50% and located at an inner side than the first layer in the secondary particles; and
a third layer having a radial depth ratio of 50% or greater and located at an inner side than the second layer in the secondary particles, and
wherein a SEM-EDX spectrum of said element M with respect to the radial depth in the secondary particles has a peak in the second layer,
wherein the peak includes a point of maximum coordinate value on a vertical axis among peaks in a CPS curve, and
wherein the CPS curve is a plot of a depth ratio in the radial direction to the radius of the secondary particles of the nickel cobalt complex hydroxide on the horizontal axis and fluorescent X-ray intensity at the depth ratio on the vertical axis.
2. The nickel cobalt complex hydroxide according to claim 1 , wherein assuming that the amount of said element M in the first layer is S1 and that the amount of said element M in the second layer is S2, S1 and S2 satisfy an inequality of S2>1.02 S1.
3. The nickel cobalt complex hydroxide according to claim 2 , wherein assuming that the amount of said element M in the third layer is S3, S2 and S3 satisfy an inequality of S2>1.02 S3.
4. The nickel cobalt complex hydroxide according to claim 1 , wherein the secondary particles of the nickel cobalt complex hydroxide have an inner core part made of fine primary particles, and the secondary particles comprise plate-like or needle-like primary particles larger than the fine primary particles outside the inner core part.
5. The nickel cobalt complex hydroxide according to claim 1 , wherein the secondary particles of the nickel cobalt complex hydroxide are made of rod-like or plate-like primary particles.