Positive electrode material for secondary battery and lithium secondary battery including the same
A positive electrode material for a secondary battery, including a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material and the second positive electrode active material consist of a lithium composite transition metal oxide including at least two or more transition metals selected from the group consisting of nickel (Ni), cobalt (Co) and manganese (Mn) are provided. The average particle size (D 50 ) of the first positive electrode active material is two or more times larger than that of the second positive electrode active material, and the first positive electrode active material has a concentration gradient in which at least one of Ni, Co or Mn contained in the lithium composite transition metal oxide has a concentration difference of 1.5 mol % or more between the center and the surface of a particle of the lithium composite transition metal oxide.
1. A positive electrode material for a secondary battery, comprising:
a first positive electrode active material and a second positive electrode active material,
wherein each of the first positive electrode active material and the second positive electrode active material consists of a lithium composite transition metal oxide including two or more transition metals selected from the group consisting of nickel (Ni), cobalt (Co) and manganese (Mn),
an average particle size (D 50 ) of the first positive electrode active material is at least two times larger than that of the second positive electrode active material, and
the first positive electrode active material has a concentration gradient in which at least one of Ni, Co or Mn contained in the lithium composite transition metal oxide has a concentration difference of 1.5 mol % or more between a center and a surface of a particle of the lithium composite transition metal oxide,
wherein the second positive electrode active material further comprises a coating layer on at least a part of the surface of the particle,
the coating layer comprises a lithium oxide containing at least one or more selected from the group consisting of boron (B) and manganese (Mn), and
wherein the lithium composite transition metal oxide of the second positive electrode active material is without a concentration gradient.
2. The positive electrode material according to claim 1 , wherein the first positive electrode active material has the concentration gradient in which a concentration of at least one of Ni, Co or Mn contained in the lithium composite transition metal oxide is gradually changed at a rate of 0.1 to 5 mol % per 1 μm from the center to the surface of the particle of the lithium composite transition metal oxide based on a total mole number of the corresponding metal included in the positive electrode active material.
3. The positive electrode material according to claim 1 , wherein the first positive electrode active material has the concentration gradient in which a concentration of Ni is gradually decreased at a rate of 0.1 to 5 mol % per 1 μm from the center to the surface of the particle of the lithium composite transition metal oxide based on a total mole number of Ni included in the positive electrode active material.
4. The positive electrode material according to claim 1 , wherein the first positive electrode active material has the concentration gradient in which a concentration of at least one of Mn or Co is gradually increased at a rate of 0.1 to 5 mol % per 1 μm from the center to the surface of the particle of the lithium composite transition metal oxide based on a total mole number of Mn or Co, respectively, included in the positive electrode active material.
5. The positive electrode material according to claim 1 , wherein the first positive electrode active material and the second positive electrode active material have a Ni content of 60 mol % or more, among entire non-lithium metal elements contained in the lithium composite transition metal oxide.
6. The positive electrode material according to claim 1 , wherein the first positive electrode active material and the second positive electrode active material include a lithium composite transition metal oxide containing Ni, Co, Mn and Al.
7. The positive electrode material according to claim 1 , wherein the first positive electrode active material and the second positive electrode active material are represented by Formula 1 below:
Li p Ni 1−(x1+y1+z1) Co x1 M a y1 M b z1 M c q1 O 2 [Formula 1]
where M a is at least one or more elements selected from the group consisting of Mn and Al, M b is at least one or more elements selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, M c is at least one or more elements selected from the group consisting of Al, Zr, Ti, Mg, Ta, Nb, Mo and Cr, and 0.9≤p≤1.5, 0<x1≤0.4, 0<y1≤0.4, 0≤z1≤0.1, 0≤q1≤0.1, and 0<x1+y1+z1≤0.4.
8. The positive electrode material according to claim 1 , wherein the first positive electrode active material and the second positive electrode active material are lithium composite transition metal oxides with same or different compositions.
9. The positive electrode material according to claim 1 , wherein a ratio of the average particle sizes (D 50 ) of the first positive electrode active material and the second positive electrode active material is 5:1 to 2:1.
10. The positive electrode material according to claim 1 , wherein the average particle size (D 50 ) of the first positive electrode active material is 10 to 30 μm.
11. The positive electrode material according to claim 1 , wherein the average particle size (D 50 ) of the second positive electrode active material is 1 to 10 μm.
12. The positive electrode material according to claim 1 , wherein the first positive electrode active material and the second positive electrode active material are present in a weight ratio of 9:1 to 1:9.
13. The positive electrode material of claim 1 , wherein the concentration difference is from 1.5 mol % to 3 mol %.
14. The positive electrode material of claim 1 , wherein a difference in the concentration of the at least one of Ni, Co or Mn per 1 μm in particles is from 0.1 to 5 mol %.
15. A positive electrode for a secondary battery, comprising the positive electrode material according to claim 1 .
16. A lithium secondary battery comprising the positive electrode according to claim 15 .
17. A positive electrode material for a secondary battery, comprising:
a first positive electrode active material and a second positive electrode active material,
wherein each of the first positive electrode active material and the second positive electrode active material consists of a lithium composite transition metal oxide including two or more transition metals selected from the group consisting of nickel (Ni), cobalt (Co) and manganese (Mn),
an average particle size (D50) of the first positive electrode active material is at least two times larger than that of the second positive electrode active material, and
the first positive electrode active material has a concentration gradient in which at least one of Ni, Co or Mn contained in the lithium composite transition metal oxide has a concentration difference of 1.5 mol % or more between a center and a surface of a particle of the lithium composite transition metal oxide,
wherein the second positive electrode active material further comprises a coating layer on at least a part of the surface of the particle,
the coating layer comprises a lithium oxide containing at least one or more selected from the group consisting of boron (B) and manganese (Mn), and
wherein the first positive electrode active material has the concentration gradient in which a concentration of at least one of Mn or Co is gradually increased at a rate of 0.1 to 5 mol % per 1 μm from the center to the surface of the particle of the lithium composite transition metal oxide based on a total mole number of Mn or Co, respectively, included in the positive electrode active material.
18. The positive electrode material of claim 17 , wherein the first positive electrode active material has the concentration gradient in which a concentration of at least one of Ni, Co or Mn contained in the lithium composite transition metal oxide is gradually changed at a rate of 0.1 to 5 mol % per 1 μm from the center to the surface of the particle of the lithium composite transition metal oxide based on a total mole number of the corresponding metal included in the positive electrode active material.
19. The positive electrode material of claim 17 , wherein the first positive electrode active material has the concentration gradient in which a concentration of Ni is gradually decreased at a rate of 0.1 to 5 mol % per 1 μm from the center to the surface of the particle of the lithium composite transition metal oxide based on a total mole number of Ni included in the positive electrode active material.
20. The positive electrode material of claim 17 , wherein the first positive electrode active material and the second positive electrode active material have a Ni content of 60 mol % or more, among entire non-lithium metal elements contained in the lithium composite transition metal oxide.