Positive electrode active material precursor for lithium secondary battery, positive electrode active material manufactured by using thereof, and lithium secondary battery including the same

1. A positive electrode active material comprising:

a plurality of primary particles, each of the plurality of primary particles comprising a plurality of metals; and

a secondary particle comprising the plurality of primary particles

wherein each of the plurality of primary particles has an a-axis and a c-axis in a crystal structure,

wherein in each of the plurality of primary particles, an a-axis directional length is longer than a c-axis directional length,

wherein the secondary particle comprises a center part and a surface part surrounding the center part, and

wherein the a-axis directional length of the primary particles in the surface part is longer than the a-axis directional length of the primary particles in the center part.

2. The positive electrode active material of claim 1 , wherein each of the plurality of primary particles comprises an oxide of at least one of nickel, cobalt, manganese and aluminum and lithium.

3. The positive electrode active material of claim 1 , wherein the secondary particle has a concentration gradient of a metal.

4. The positive electrode active material of claim 1 , wherein the primary particles are adjoining each other and grow to a fixed route, and a lithium ion is easily inserted to a space formed between the fixed routes.

5. The positive electrode active material of claim 1 , wherein the a-axis and the c-axis are defined by a diffraction pattern of a Fourier transform obtained from a TEM image of the plurality of primary particles.

6. A positive electrode active material comprising:

a plurality of primary particles, each of the plurality of primary particles comprising a plurality of metals; and

a secondary particle comprising the plurality of primary particles,

wherein each of the plurality of primary particles has an a-axis and a c-axis in a crystal structure,

wherein the a-axis and the c-axis are defined by a diffraction pattern of a Fourier transform obtained from a TEM image of the plurality of primary particles,

wherein the secondary particle comprises a center part and a surface part surrounding the center part, and

the a-axis of at least a part of the plurality of primary particles extends in a direction toward the surface part.

7. The positive electrode active material of claim 6 , wherein each of the plurality of primary particles has a rod shape having a long side and a short side.

8. The positive electrode active material of claim 7 , wherein the long side corresponds to the a-axis so that the plurality of primary particles extend from the center part to the surface part.

9. The positive electrode active material of claim 8 , wherein each of the plurality of primary particles has a concentration gradient of a metal from a portion adjacent to the center part to a portion adjacent to the surface part.

10. The positive electrode active material of claim 6 , wherein an aspect ratio of the primary particles in the center part is smaller than an aspect ratio of the primary particles in the surface part.

11. The positive electrode active material of claim 6 , wherein a concentration gradient of a metal is provided inside each of the plurality of primary particles in a longitudinal direction of each of the plurality of primary particles.

12. The positive electrode active material of claim 11 , wherein the metal is at least one of nickel, cobalt, manganese, and aluminum, and a concentration gradient of the metal is provided inside the primary particles.

13. A positive electrode active material comprising:

an oxide of at least one of nickel, cobalt, manganese and aluminum and lithium; and

a secondary particle comprising a plurality of primary particles,

wherein each of the plurality of primary particles has an a-axis and a c-axis in a crystal structure,

wherein the a-axis and the c-axis are defined by a diffraction pattern of a Fourier transform obtained from a TEM image of the plurality of primary particles,

wherein the secondary particle comprises a seed region, an intermediate region, and a maintain region in a direction from a center part to a surface part,

wherein a length of the primary particles of the maintain region in the direction from the center part to the surface part is longer than a length of the primary particles of the seed region, and

wherein a content of a metal of the maintain region is smaller than a content of a metal of the seed region.

14. The positive electrode active material of claim 13 , wherein each of the plurality of primary particles has a hexagonal crystal structure.

15. The positive electrode active material of claim 13 , wherein the primary particles in the intermediate region comprise:

a concentration gradient part in which a concentration of any one or more of the nickel, the cobalt, the manganese, and the aluminum is changed; and

a concentration maintaining part in which a concentration of any one or more of the nickel, the cobalt, the manganese, and the aluminum is constant.

16. The positive electrode active material of claim 13 , wherein the secondary particle comprises the center part and the surface part, and

a concentration of nickel of the center part is higher than a concentration of nickel of the surface part.

17. The positive electrode active material of claim 13 , wherein an average concentration of nickel is about 80 mol % or more.

18. The positive electrode active material of claim 13 , wherein a length of the seed region from the center part to the surface part is at least 1 μm or more.

19. A lithium secondary battery comprising:

a positive electrode comprising the positive electrode active material of claim 1 ;

a negative electrode spaced apart from the positive electrode; and

an electrolyte between the positive electrode and the negative electrode.