Positive electrode material for lithium secondary battery, and positive electrode and lithium secondary battery which include the same
A positive electrode material, a positive electrode including the same, and a lithium secondary battery including the same are disclosed herein. In some embodiments, a positive electrode material includes a first positive electrode active material having a larger average particle diameter than a second positive electrode active material, wherein the first positive electrode active material and the second positive electrode active material are each independently a lithium transition metal oxide having a molar ratio of nickel of 80 mol % or more relative to the total molar amount of transition metals in the lithium transition metal oxide, and the positive electrode material satisfies Equation (1): 0<{( B−A )/ B }×100≤10 Equation (1): wherein, in Equation (1), A denotes a particle strength of the first positive electrode active material, and B denotes a particle strength of the second positive electrode active material.
1. A positive electrode material, comprising:
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 are each independently a lithium transition metal oxide having a molar ratio of nickel of 80 mol % or more relative to the total molar amount of transition metals in the lithium transition metal oxide,
wherein an average particle diameter (D 50 ) of the first positive electrode active material is larger than an average particle diameter (D 50 ) of the second positive electrode active material, and
wherein the positive electrode material satisfies Equation (1):
0<{( B−A )/ B}× 100≤10 Equation (1):
wherein, in Equation (1), A is a particle compressive fracture strength of the first positive electrode active material, and B is a particle compressive fracture strength of the second positive electrode active material wherein the first positive electrode active material and the second positive electrode active material are each independently a lithium transition metal oxide represented by Formula 1: Li 1+a Ni x Co y M 1 z M 2 w O 2 [Formula 1] wherein, in Formula 1, 0≤a≤0.3, 0.8≤x<1.0, 0<y<0.2, 0<z<0.2, and 0≤w≤0.1, M 1 is at least one selected from the group consisting of manganese (Mn) and aluminum (Al), and M 2 is at least one selected from the group consisting of tungsten (W), molybdenum (Mo), chromium (Cr), zirconium (Zr), titanium (Ti), magnesium (Mg), tantalum (Ta), and niobium (Nb).
2. The positive electrode material of claim 1 , wherein the first positive electrode active material and the second positive electrode active material are each independently a lithium transition metal oxide represented by Formula 2:
Li 1+a Ni x Co y Mn z1 Al z2 M 2 w O 2 [Formula 2]
wherein, in Formula 2,
0≤a≤0.3, 0.8≤x<1.0, 0<y<0.2, 0<z1<0.2, 0<z2<0.2, and 0≤w≤0.1, and
M 2 is at least one selected from the group consisting of W, Mo, Cr, Zr, Ti, Mg, Ta, and Nb.
3. The positive electrode material of claim 1 , wherein the first positive electrode active material is a lithium transition metal oxide having a molar ratio of the nickel of 85 mol % or more relative to the total molar amount of transition metals in the lithium transition metal oxide, and
Wherein the second positive electrode active material is a lithium transition metal oxide having a molar ratio of the nickel of 80 mol % to 85 mol % relative to the total molar amount of transition metals in the lithium transition metal oxide.
4. The positive electrode material of claim 1 , wherein A is in a range of 50 MPa to 500 MPa.
5. The positive electrode material of claim 1 , wherein B is in a range of 50 MPa to 500 MPa.
6. The positive electrode material of claim 1 , wherein the positive electrode material has a bimodal particle size distribution.
7. The positive electrode material of claim 1 , wherein the average particle diameter (D 50 ) of the first positive electrode active material is in a range of greater than 8 μm to 50 μm or less.
8. The positive electrode material of claim 1 , wherein the average particle diameter (D 50 ) of the second positive electrode active material is in a range of 0.1 μm to 8 μm.
9. The positive electrode material of claim 1 , wherein the first positive electrode active material and the second positive electrode active material are present in a weight ratio of 50:50 to 99:1.
10. A positive electrode comprising the positive electrode material of claim 1 .
11. A lithium secondary battery comprising the positive electrode of claim 10 .