Nickel-based active material for lithium secondary battery, method of preparing the same, and lithium secondary battery including positive electrode including the nickel-based active material

1. A nickel-based active material for a lithium secondary battery, the nickel-based active material comprising:

at least one secondary particle comprising an aggregate of plate-shaped primary particles arranged to have a radially aligned outer portion and an irregularly aligned inner portion, the irregularly aligned inner portion having a plurality of pores distributed throughout, and

a hetero-element compound on the plate-shaped primary particles.

2. The nickel-based active material of claim 1 , wherein the hetero-element compound is included along a grain boundary of adjacent primary particles and/or on a surface of a primary particle.

3. The nickel-based active material of claim 1 , wherein the hetero-element is at least one selected from zirconium (Zr), titanium (Ti), aluminum (Al), magnesium (Mg), tungsten (W), phosphorus (P), and boron (B).

4. The nickel-based active material of claim 3 , wherein the hetero-element compound further comprises lithium (Li).

5. The nickel-based active material of claim 3 , wherein an amount of the at least one hetero-element of the hetero-element compound is about 0.0005 mol to about 0.03 mol based on 1 mol of transition metals of the nickel-based active material.

6. The nickel-based active material of claim 1 , wherein

a pore size of the inner portion is larger than a pore size of the outer portion.

7. The nickel-based active material of claim 6 , wherein the pore size of the inner portion is about 150 nm to about 1 μm, and the pore size of the outer portion is less than 150 nm.

8. The nickel-based active material of claim 6 , wherein the secondary particle further comprises an open pore having a pore size of less than 150 nm toward the inner portion.

9. The nickel-based active material of claim 1 , wherein the plate-shaped primary particles in the outer portion each have a long axis arranged in a radial direction.

10. The nickel-based active material of claim 9 , wherein the plate-shaped primary particles each have an average length of about 150 nm to about 500 nm, an average thickness of about 100 nm to about 200 nm, and a length-to-thickness ratio of about 1:2 to about 1:10.

11. The nickel-based active material of claim 1 , wherein the nickel-based active material of the at least one secondary particle is represented by Formula 1:

Li a (Ni 1-x-y-z Co x Mn y M z )O 2   Formula 1

wherein, in Formula 1, M is at least one element selected from boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), and aluminum (Al), and

a, x, y, and z satisfy the following relations: 0.95≤a≤1.3, x≤(1−x−y−z), y≤(1−x−y−z), 0<x<1, 0≤y<1, and 0≤z<1.

12. The nickel-based active material of claim 1 , wherein the nickel-based active material is LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.33 CO 0.33 Mn 0.33 O 2 , LiNi 0.8 CO 0.1 Mn 0.1 O 2 , or LiNi 0.85 CO 0.1 Al 0.05 O 2 .

13. A lithium secondary battery comprising:

a positive electrode comprising the nickel-based active material of claim 1 ;

a negative electrode; and

an electrolyte between the positive electrode and the negative electrode.

14. A method of preparing a nickel-based active material of claim 1 , the method comprising:

obtaining a nickel-based active material A by performing a first heat treatment on a mixture of a lithium precursor and metal hydroxide in an oxidative gas atmosphere; and

mixing a raw material containing the nickel-based active material A and a heteroelement and performing a second heat treatment thereon,

wherein a temperature at which the second heat treatment is performed is higher than a temperature at which the first heat treatment is performed, and

the prepared nickel-based active material comprises at least one secondary particle comprising an aggregate of two or more primary particles, wherein at least a portion of the secondary particle has a radial alignment structure.

15. The method of claim 14 , wherein the first heat treatment is performed at 600° C. to 800° C., and the second heat treatment is performed at 700° C. to 900° C.