Cathode active material precursor, cathode active material formed therefrom, method of preparing the cathode active material, and cathode and lithium battery each including the cathode active material

1. A cathode active material comprising:

a secondary particle comprising an aggregate of a plurality of primary particles,

wherein the secondary particle comprises a nickel-containing lithium transition metal oxide having a layered crystal structure,

wherein the plurality of primary particles comprises

a first primary particle having a size greater than about 400 nanometers,

a second primary particle having a size less than about 150 nanometers, and

a third primary particle having a size of about 150 nanometers to about 400 nanometers,

wherein the third primary particle has an area of about 80% to about 95% about 80% of a total area of the plurality of primary particles, and

wherein the secondary particle has a porosity of less than or equal to about 10% of a total area of the cathode active material.

2. The cathode active material of claim 1 ,

wherein the first primary particle has an area of less than or equal to about 20% of the total area of the plurality of primary particles,

wherein an area of the second primary particle is less than or equal to about 9% of the total area of the plurality of primary particles, and

wherein the secondary particle has a porosity of about 1% to about 10% of the total area of the cathode active material.

3. The cathode active material of claim 1 ,

wherein the plurality of primary particles has a particle uniformity of greater than or equal to about 90%,

wherein the first primary particle has an area of about 2.1% to about 19.2% of the total area of the plurality of primary particles,

wherein the second primary particle has an area of about 0.1% to about 8.6% of the total area of the plurality of primary particles, and

wherein the secondary particle has a porosity of about 1.5% to about 7% of the total area of the cathode active material.

4. The cathode active material of claim 1 , wherein the secondary particle comprising the nickel-containing lithium transition metal oxide having a layered crystal structure has an average particle diameter of about 15 μm to about 30 μm.

5. The cathode active material of claim 1 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure has a layered rock-salt structure and belongs to space group R-3m.

6. The cathode active material of claim 1 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure is a compound represented by Formulae 1 to 4:

Li x Ni 1−y−z−α Co y Mn z Me α O 2   Formula 1

wherein, in Formula 1,

1≤x≤1.1, 0≤y≤0.2, 0≤z≤0.2, 0≤α≤0.05,

Me may be Zr, Al, Mg, Ti, Cu, W, B, or a combination thereof, and

y+z+α≤0.3,

Li x Co 1−y M y O 2−α X α   Formula 2

Li x Ni 1−y Me y O 2−α X α   Formula 3

Li x Ni 1−y−z Mn y Ma z O 2−α X α   Formula 4

wherein, in Formulae 2 to 4,

1≤x≤1.1, 0≤y≤0.9, 0≤z≤0.2, 0≤α≤2,

M may be Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B, or a combination thereof,

Me may be Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Mn, Fe, Cu, B, or a combination thereof,

Ma may be Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B, or a combination thereof, and

X may be F, S, P or a combination thereof, and

wherein x, y, z, α, and Me are independently selected for each of Formulae 1 to 4.

7. The cathode active material of claim 1 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure is a compound represented by Formulae 5 to 7:

Li[Li 1−a Me a ]O 2+d   Formula 5

wherein, in Formula 5, 0.8≤a<1, 0≤d≤0.1, and

Me may be Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo, Pt or a combination thereof,

Li[Li 1−x−y−z Ma x Mb y Mc z ]O 2+d   Formula 6

wherein, in Formula 6, 0.8≤x+y+z<1, 0<x<1, 0<y<1, 0<z<1, 0≤d≤0.1, and

Ma, Mb, and Mc are each independently Mn, Co, Ni, Al, or a combination thereof

Li[Li 1−x−y−z Ni x Co y Mn z ]O 2+d   Formula 7

wherein, in Formula 7, 0.8≤x+y+z<1; 0<x<1, 0<y<1, 0<z<1, and 0≤d≤0.1, and

wherein x, y, z, d, Me, and Ma are independently selected for each of Formulae 5 to 7.

8. The cathode active material of claim 1 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure is a compound represented by Formula 8:

aLi 2 MnO 3− (1−a)LiMO 2   Formula 8

wherein, in Formula 8, 0<a<1, and

M comprises nickel, cobalt, manganese, vanadium, chromium, iron, zirconium, rhenium, aluminum, boron, germanium, ruthenium, tin, titanium, niobium, molybdenum, platinum, or a combination thereof.

9. The cathode active material of claim 1 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure is a compound represented by Formula 9:

Li x Ni 1−y−z M y Co z O 2   Formula 9

wherein, in Formula 9, 0.90≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.7≤1−y−z≤0.99, and

M is manganese, aluminum, titanium, calcium, or a combination thereof.

10. The cathode active material of claim 1 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure is a compound represented by Formula 9a:

Li x Ni 1−y−z M x Co y O 2   Formula 9a

wherein, in Formula 9a, 0.80≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, and 0.8≤1−y−z≤0.99.

11. The cathode active material of claim 10 , wherein the nickel-containing lithium transition metal oxide having a layered crystal structure is Li 1.03 [Ni 0.91 Co 0.06 Mn 0.03 ]O 2 , Li 1.03 [Ni 0.88 Co 0.08 Mn 0.04 ]O 2 , Li 1.03 [Ni 0.8 Co 0.15 Mn 0.05 ]O 2 , Li 1.03 [Ni 0.85 Co 0.10 Mn 0.05 ]O 2 , Li 1.03 [Ni 0.91 Co 0.05 Mn 0.04 ]O 2 , Li 1.05 [Ni 0.91 Co 0.06 Mn 0.03 ]O 2 , Li 1.05 [Ni 0.88 Co 0.08 Mn 0.04 ]O 2 , Li 1.05 [Ni 0.8 Co 0.15 Mn 0.05 ]O 2 , Li 1.05 [Ni 0.85 Co 0.10 Mn 0.05 ]O 2 , Li 1.05 [Ni 0.91 Co 0.05 Mn 0.04 ]O 2 , Li 1.06 [Ni 0.91 Co 0.06 Mn 0.03 ]O 2 , Li 1.06 [Ni 0.88 Co 0.08 Mn 0.04 ]O 2 , Li 1.06 [Ni 0.8 Co 0.15 Mn 0.05 ]O 2 , Li 1.06 [Ni 0.85 Co 0.10 Mn 0.05 ]O 2 , Li 1.06 [Ni 0.91 Co 0.05 Mn 0.04 ]O 2 ; Li 1.09 [Ni 0.91 Co 0.06 Mn 0.03 ]O 2 , Li 1.09 [Ni 0.88 Co 0.08 Mn 0.04 ]O 2 , Li 1.09 [Ni 0.8 Co 0.15 Mn 0.05 ]O 2 , Li 1.09 [Ni 0.85 Co 0.10 Mn 0.05 ]O 2 , or Li 1.09 [Ni 0.91 Co 0.05 Mn 0.04 ]O 2 .

12. The cathode active material of claim 1 , wherein the cathode active material further includes a small-particle-size cathode active material, and a mixture of the cathode active material and small-particle-size cathode active material has a pressed density of about 3.3 grams per cubic centimeter or greater.

13. A cathode comprising the cathode active material of claim 1 .

14. A lithium battery comprising:

the cathode of claim 13 ,

an anode,

and an electrolyte disposed between the cathode and the anode.

15. The lithium battery of claim 14 , wherein the lithium battery has an initial efficiency of about 93% or greater, and

the cathode has a pressed density of greater than or equal to about 2.8 grams per cubic centimeter.

16. The lithium battery of claim 14 , wherein, after discharging to 3.5 volts, the cathode active material has

an a-axis crystal lattice constant that is about 0.1% to about 0.5% less than an a-axis crystal lattice constant before the discharging, and

a c-axis crystal lattice constant that is about 0.1% to about 0.5% greater than a c-axis crystal lattice constant before the discharging.

17. A method of preparing a cathode active material, the method comprising:

mixing the cathode active material precursor and a lithium precursor to produce a mixture, wherein the cathode active material precursor has a specific area of about 8 square meters per gram to about 25 square meters per gram, and an average particle diameter of about 13.7 micrometers or greater, and wherein the cathode active material precursor is a vertical plate network-structured precursor of a nickel-containing lithium transition metal oxide;

first thermally treating the mixture to produce a first product;

washing the first product with water to produce a washed product;

drying the washed product to produce a dried product; and

second thermally treating the dried product to prepare the cathode active material of claim 1 ,

wherein a temperature of the second thermal treatment is less than a temperature of the first thermal treatment, and the cathode active material precursor includes a vertical plate network-structured precursor of a nickel-containing lithium transition metal oxide, wherein the cathode active material precursor has a specific area of about 8 square meters per gram to about 25 square meters per gram, and an average particle diameter of about 13.7 micrometers or greater.

18. The method of claim 17 , wherein the cathode active material precursor is prepared by:

mixing a metal source, a complexing agent, and a pH-adjusting agent to produce a mixture;

adjusting a pH of the mixture to produce a pH-adjusted mixture; and

reacting the pH-adjusted mixture.