Composite positive active material, method of preparing the same, and positive electrode and lithium battery containing the material
A composite positive active material including an over-lithiated lithium transition metal oxide, the over-lithiated transition metal oxide including a compound represented by Formula 1 or Formula 3: [Formula 1] xLi 2-y M″ y MO 3 -(1-x)LiM′O 2 , [Formula 3] xLi 2-y M″ y MO 3 -x′LiM′O 2 -x″Li 1+d M′″ 2-d O 4 , x+x′+x″=1, 0<x<1, 0<x′<1, 0<x″<1, 0<y≦1, and 0≦d≦0.33, is disclosed. A positive electrode and a lithium battery containing the composite positive active material, and a method of preparing the composite positive active material are also disclosed.
1. A composite positive active material comprising an over-lithiated lithium transition metal oxide, the over-lithiated lithium transition metal oxide comprising a compound represented by Formula 1 or Formula 3:
x Li 2-y M″ y MO 3 -(1- x )LiM′O 2 [Formula 1]
in Formula 1, M being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number of +4,
M′ being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number of +3,
M″ being different from M and being at least one metal cation selected from Period 2 to Period 7 elements,
0<x<1, and 0<y≦1;
x Li 2-y M″ y MO 3 - x ′LiM′O 2 - x ″Li 1+d M′″ 2-d O 4 [Formula 3]
in Formula 3, M being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number of +4,
M′ being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number of +3,
M′″ being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number from +3 to +4, and
M″ being different from M, M′ and M′″ and being at least one metal cation selected from Period 2 to Period 7 elements,
x+x′+x″=1, 0<x<1, 0<x′<1, 0<x″<1, 0<y≦1, and 0≦d≦0.33,
wherein the over-lithiated lithium transition metal oxide has more than one phase.
2. The composite positive active material of claim 1 , wherein, in Formula 1, M″ is doped in a Li ion layer of Li 2-y M″ y MO 3 .
3. The composite positive active material of claim 1 , wherein 0<x<0.6 and 0<y<0.1.
4. The composite positive active material of claim 1 , wherein the over-lithiated lithium transition metal oxide further comprises fluorine.
5. The composite positive active material of claim 1 , wherein M is at least one metal selected from Mn, Ti, Zr, Sn, and Mo.
6. The composite positive active material of claim 1 , wherein M′ is at least one metal selected from Ni, Co, Mn, Fe, Al, Mg, Zn, Cu, Cr, V, and Nb.
7. The composite positive active material of claim 1 , wherein M″ is at least one metal cation selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, and In.
8. The composite positive active material of claim 7 , wherein M″ is at least one metal cation selected from Al, Mn, Cr, Zn, Ga, Mg, V, and Zr.
9. The composite positive active material of claim 1 , wherein the over-lithiated lithium transition metal oxide comprises a compound represented by Formula 2:
x Li 2-y M″ y MnO 3 -(1- x )LiNi a Co b Mn c O 2 [Formula 2]
wherein 0<x<1, 0<y≦1, 0<a<1, 0<b<1, 0<c<1, a+b+c=1, and M″ is different from Mn and is at least one metal cation selected from Period 2 to Period 7 elements.
10. The composite positive active material of claim 1 , wherein the over-lithiated lithium transition metal oxide is included in particles having an average particle size from about 10 nm to about 500 μm.
11. A lithium battery comprising:
a positive electrode comprising the composite positive active material of claim 1 ;
a negative electrode facing the positive electrode; and
an electrolyte between the positive electrode and the negative electrode.
12. A composite positive active material comprising an over-lithiated lithium transition metal oxide, the over-lithiated lithium transition metal oxide comprising a compound represented by Formula 9:
x Li 2 MO 3 -(1- x )LiM′O 2 [Formula 9]
M being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number of +4,
M′ being at least one metal selected from Period 4 transition metals and Period 5 transition metals and having an average oxidation number of +3,
a portion y, wherein 0<y≦1, of Li in a Li ion layer of the over-lithiated lithium transition metal oxide being replaced with at least one metal cation selected from Period 2 to Period 7 elements, and
0<x<1,
wherein the over-lithiated lithium transition metal oxide has more than one phase.