Positive active material for rechargeable lithium battery and rechargeable lithium battery
A positive active material for a rechargeable lithium battery includes a lithium nickel composite oxide having an I (003) /I (104) ratio of greater than or equal to about 0.92 and less than or equal to about 1.02 in X-ray diffraction, wherein the I (003) /I (104) ratio is a ratio of a diffraction peak intensity I (003) of a (003) phase and a diffraction peak intensity I (104) of a (104) phase. The lithium nickel composite oxide includes lithium and a nickel-containing metal, and nickel is present in an amount of greater than or equal to about 80 atm % based on the total atom amount of the nickel-containing metal. A rechargeable lithium battery includes the positive active material.
1. A positive active material for a rechargeable lithium battery, comprising
a lithium nickel composite oxide having a I (003) /I (104) ratio of greater than or equal to about 0.92 and less than or equal to about 1.02 in X-ray diffraction, wherein the I (003) /I (104) ratio is a ratio of a diffraction peak intensity I (003) of a (003) phase and a diffraction peak intensity I (104) of a (104) phase,
wherein the lithium nickel composite oxide comprises lithium and a nickel-containing metal,
wherein the lithium nickel composite oxide is represented by Chemical Formula 1:
Li a Ni x CO y M z O 2 Chemical Formula 1
wherein, M is at least one metal selected from aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce), and
0.2≤a≤1.2, 0.85≤x<1, 0<y≤0.2, 0≤z≤, and x+y+z=1,
wherein a full width at half maximum FWHM (003) of a diffraction peak at the (003) phase of the lithium nickel composite oxide in X-ray diffraction is greater than or equal to about 0.13 and less than or equal to about 0.15,
wherein the lithium nickel composite oxide has an average transition metal valence of greater than or equal to about 2.9 calculated from an analysis of an X-ray absorption fine structure (XAFS) or from a carbon, hydrogen, nitrogen, oxygen (CHNO) elemental analysis, and
wherein the lithium nickel composite oxide is produced by adding a saturated NaCO 3 aqueous solution to co-precipitate a carbonate salt of Ni, Co and M to provide a co-precipitated carbonate salt; mixing lithium hydroxide with the co-precipitated carbonate salt to provide a mixed powder, and conducting a single firing at about 750° C. to about 850° C. under an oxygen partial pressure of greater than about 0.1 MPa and less than about 0.5 MPa to provide the lithium nickel composite oxide.
2. The positive active material of claim 1 ,
wherein, M is at least one metal selected from chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce), 0.2≤a≤1.2, 0.85≤x<1, 0<y≤0.2, 0≤z≤0.1, and x+y+z=1.
3. The positive active material of claim 1 , wherein an average particle diameter of secondary particles of the lithium nickel composite oxide is greater than or equal to about 8 μm and less than or equal to about 25 μm.
4. The positive active material of claim 1 , wherein the lithium nickel composite oxide is obtained by firing the mixed powder at an oxygen partial pressure of from 0.2 MPa to less than 0.5 MPa.
5. The positive active material of claim 1 , wherein a full width at half maximum FWHM (104) of a diffraction peak at the (104) phase of the lithium nickel composite oxide in X-ray diffraction is greater than or equal to about 0.15 and less than or equal to about 0.18.
6. A rechargeable lithium battery comprising a positive electrode comprising the positive active material of claim 1 .
7. The rechargeable lithium battery of claim 6 , wherein the lithium nickel composite oxide is represented by Chemical Formula 1:
Li a Ni x CO y M z O 2 Chemical Formula 1
wherein, M is at least one metal selected from aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce), 0.2≤a≤1.2, 0.85≤x<1, 0<y≤0.2, 0≤z≤0.1, and x+y+z=1.
8. The rechargeable lithium battery of claim 6 , wherein an average particle diameter of secondary particles of the lithium nickel composite oxide is greater than or equal to about 8 μm and less than or equal to about 25 μm.
9. The rechargeable lithium battery of claim 6 , wherein the lithium nickel composite oxide is obtained by firing a lithium nickel composite oxide precursor at an oxygen partial pressure of greater than about 0.1 MPa and less than about 0.5 MPa.
10. The rechargeable lithium battery of claim 6 , wherein a full width at half maximum FWHM (104) of a diffraction peak at the (104) phase of the lithium nickel composite oxide in X-ray diffraction is greater than or equal to about 0.15 and less than or equal to about 0.18.
11. The rechargeable lithium battery of claim 6 , wherein the lithium nickel composite oxide has an average transition metal valence of greater than or equal to about 2.9 calculated from an analysis of an X-ray absorption fine structure (XAFS) or from a carbon, hydrogen, nitrogen, oxygen (CHNO) elemental analysis.
12. The positive active material of claim 1 , wherein, M is at least one metal selected from manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce).