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 two or more primary particles at least a portion of the at least one secondary particle having a radial alignment structure, the two or more primary particles comprising a plurality of adjacent primary particles that form the radial alignment structure; and

a hetero-element compound included along a grain boundary of the plurality of adjacent primary particles that form the radial alignment structure.

2. The nickel-based active material of claim 1 , wherein the hetero-element compound is included on a surface of a primary particle of the plurality of adjacent primary particles that form the radial alignment structure.

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

5. The nickel-based active material of claim 1 , wherein the at least one secondary particle has an outer portion arranged in a radial alignment structure and an inner portion with an irregular porous structure.

6. The nickel-based active material of claim 4 , 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.

7. The nickel-based active material of claim 1 , wherein the at least one secondary particle has an outer portion arranged in a radial alignment structure and an inner portion with an irregular porous structure, wherein a pore size of the inner portion is larger than that of the outer portion.

8. The nickel-based active material of claim 7 , wherein the inner portion of the at least one secondary particle has a pore size of about 150 nm to about 1 μm, and the outer portion has a pore size less than 150 nm.

9. The nickel-based active material of claim 7 , wherein the at least one secondary particle further comprises an open pore having a pore size of less than 150 nm toward the inner portion.

10. The nickel-based active material of claim 1 , wherein the nickel-based active material comprises a plate particle having a long axis arranged in a radial direction.

11. The nickel-based active material of claim 10 , wherein the plate particle has 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.

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

13. 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 .

14. 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.