Positive active material, and positive electrode and lithium battery including positive active material
A positive active material includes first and second lithium nickel complex oxides. A positive electrode and lithium battery include the positive active material. The positive active material, and the lithium battery including the positive active material have increased filling density, are thermally stable, and have improved capacity.
1. A positive active material for a lithium battery, the positive active material comprising:
a first lithium nickel complex oxide having a particle volume distribution of 3.0 μm≦D25≦10.0 μm, 5.0 μm≦D50≦20.0 μm, and 10.0 μm≦D75≦25.0 μm, and
a second lithium nickel complex oxide having a particle volume distribution of 0.01 μm≦D25≦5.0 μm, 1.0 μm≦D50≦10.0 μm, and 5.0 μm≦D75≦15.0 μm.
2. The positive active material of claim 1 , wherein the first lithium nickel complex oxide has a particle volume distribution of 5.0 μm≦D25≦9.0 μm, 8.0 μm≦D50≦13.0 μm, and 13.0 μm≦D75≦18.0 μm, and the second lithium nickel complex oxide has a particle volume distribution of 1.0 μm≦D25≦3.0 μm, 2.0 μm≦D50≦7.0 μm, and 6.0 μm≦D75≦10.0 μm.
3. The positive active material of claim 1 , wherein the first lithium nickel complex oxide has a higher atomic percentage of nickel than the second lithium nickel complex oxide.
4. The positive active material of claim 1 , wherein the first lithium nickel complex oxide is represented by Formula 1 and the second lithium nickel complex oxide is represented by Formula 2:
Li a1 Ni x1 M′ y1 M″ z1 O 2-b1 X b1 Formula 1
Li a2 Ni x2 M′ y2 M″ z2 O 2-b2 X b2 Formula 2
wherein:
each M′ is independently at least one metal selected from the group consisting of Co, Mn, and alloys thereof;
each M″ is independently at least one metal selected from the group consisting of Al, Mg, Cr, Fe, Ti, Zr, Mo, and alloys thereof,
X is an element selected from the group consisting of O, F, S, and P,
0.9≦a1≦1.1,
x1=1−y1−z1
0≦y1≦0.5,
0≦z1≦0.2,
0≦b1≦2,
0.9≦a2≦1.1,
x2=1−y2−z2
0≦y2≦0.5,
0≦z2≦0.2, and
0≦b2≦2.
5. The positive active material of claim 4 , wherein x1>x2.
6. The positive active material of claim 5 , wherein 0.5<x1<1 and 0<x2≦0.5.
7. The positive active material of claim 5 , wherein 0.55≦x1<1 and 0<x2<0.55.
8. The positive active material of claim 1 , wherein the first lithium nickel complex oxide is at least one selected from the group consisting of LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.55 Co 0.25 Mn 0.2 O 2 , LiNi 0.55 Co 0.2 Mn 0.25 O 2 , and LiNi 0.55 Co 0.15 Mn 0.3 O 2 .
9. The positive active material of claim 1 , wherein the second lithium nickel complex oxide is at least one selected from the group consisting of LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.4 Co 0.3 Mn 0.3 O 2 , LiNi 0.4 Co 0.2 Mn 0.4 O 2 , and LiNi 1/3 Co 1/3 Mn 1/3 O 2 .
10. The positive active material of claim 1 , wherein the first lithium nickel complex oxide is LiNi 0.6 Co 0.2 Mn 0.2 O 2 and the second lithium nickel complex oxide is LiNi 0.5 Co 0.2 Mn 0.3 O 2 .
11. The positive active material of claim 1 , wherein the first lithium nickel complex oxide is present at about 75 wt % to about 99.99 wt % based on the weight of the positive active material, and the second lithium nickel complex oxide is present at about 0.01 wt % to about 25 wt % based on the weight of the positive active material.
12. The positive active material of claim 1 , wherein the positive active material has a press density of about 3.2 g/cm 3 to about 4.0 g/cm 3 .
13. The positive active material of claim 1 , further comprising a third lithium nickel complex oxide having a particle volume distribution of 2.0 μm≦D25≦7.0 μm, 3.0 μm≦D50≦15.0 μm, and 7.0 μm≦D75≦20.0 μm.
14. The positive active material of claim 13 , wherein the third lithium nickel complex oxide is represented by Formula 3:
Li a3 Ni x3 M′ y3 M″ z O 2-b3 X b3 Formula 3
wherein:
M′ is at least one metal selected from the group consisting of Co, Mn, and alloys thereof;
M″ is at least one metal selected from the group consisting of Al, Mg, Cr, Fe, Ti, Zr, Mo, and alloys thereof,
X is an element selected from the group consisting of O, F, S, and P,
0.9≦a3≦1.1,
x3=1−y3−z3
0≦y3≦0.5,
0≦z3≦0.2, and
0≦b3≦2.
15. The positive active material of claim 14 , wherein the first lithium nickel complex oxide is represented by Formula 1 and the second lithium nickel complex oxide is represented by Formula 2:
Li a1 Ni x1 M′ y1 M″ z1 O 2-b1 X b1 Formula 1
Li a2 Ni x2 M′ y2 M″ z2 O 2-b2 X b2 Formula 2
wherein:
each M′ is independently at least one metal selected from the group consisting of Co, Mn, and alloys thereof;
each M″ is independently at least one metal selected from the group consisting of Al, Mg, Cr, Fe, Ti, Zr, Mo, and alloys thereof,
X is an element selected from the group consisting of O, F, S, and P,
0.9≦a1≦1.1,
x1=1−y1−z1
0≦y1≦0.5,
0≦z1≦0.2,
0≦b1≦2,
0.9≦a2≦1.1,
x2=1−y2−z2
0≦y2≦0.5,
0≦z2≦0.2,
0≦b2≦2, and
x2<x3≦x1.
16. An electrode for a lithium battery, the electrode comprising the positive active material of claim 1 .
17. A lithium battery comprising:
a positive electrode comprising a positive active material comprising a first lithium nickel complex oxide having a particle volume distribution of 3.0 μm≦D25≦10.0 μm, 5.0 μm≦D50≦20.0 μm, and 10.0 μm≦D75≦25.0 μm, and a second lithium nickel complex oxide having a particle volume distribution of 0.01 μm≦D25≦5.0 μm, 1.0 μm≦D50≦10.0 μm, and 5.0 μm≦D75≦15.0 μm.
18. The lithium battery of claim 17 , wherein the first lithium nickel complex oxide is represented by Formula 1 and the second lithium nickel complex oxide is represented by Formula 2:
Li a1 Ni x1 M′ y1 M″ z1 O 2-b1 X b1 Formula 1
Li a2 Ni x2 M′ y2 M″ z2 O 2-b2 X b2 Formula 2
wherein:
each M′ is independently at least one metal selected from the group consisting of Co, Mn, and alloys thereof;
each M″ is independently at least one metal selected from the group consisting of Al, Mg, Cr, Fe, Ti, Zr, Mo, and alloys thereof,
X is an element selected from the group consisting of O, F, S, and P,
0.9≦a1≦1.1,
x1=1−y1−z1
0≦y1≦0.5,
0≦z1≦0.2,
0≦b1≦2,
0.9≦a2≦1.1,
x2=1−y2−z2
0≦y2≦0.5,
0≦z2≦0.2, and
0≦b2≦2.
19. The lithium battery of claim 18 , wherein x1>x2.
20. The lithium battery of claim 17 , wherein the positive active material further comprises a third lithium nickel complex oxide having a particle volume distribution of 2.0 μm≦D25≦7.0 μm, 3.0 μm≦D50≦15.0 μm, and 7.0 μm≦D75≦20.0 μm.