Lithium composite oxide for a lithium secondary battery and positive electrode for a lithium secondary battery including the lithium composite oxide
A nickel composite hydroxide for a lithium secondary battery represented by Formula 1 below with a small compositional variation in M: Ni 1-x-y-z Co x M y Mn z (OH) 2 (1), where, in Formula 1, M is aluminum (Al), zirconium (Zr), titanium (Ti), magnesium (Mg), silicon (Si), or zinc (Zn), x is a number from 0 to 0.5, y is a number from 0.01 to 0.2, and z is a number from 0 to 0.5.
1. A nickel composite hydroxide for a lithium secondary battery that is Ni 0.80 Co 0.10 Mn 0.05 Al 0.05 (OH) 2 or Ni 0.9 Co 0.05 Mn 0.025 Al 0.025 (OH) 2 .
2. The nickel composite hydroxide as claimed in claim 1 , wherein the Al has a compositional variation of about 2% or less as measured by energy dispersive spectroscopy (EDS).
3. The nickel composite hydroxide as claimed in claim 1 , wherein the nickel composite hydroxide has an average particle diameter of from about 5 μm to about 25 μm, and a tap density of from about 1.0 g/cm 3 to about 3.0 g/cm 3 .
4. A lithium composite oxide for a lithium secondary battery that is LiNi 0.80 Co 0.10 Mn 0.05 Al 0.05 O 2 .
5. The lithium composite oxide as claimed in claim 4 , wherein the lithium composite oxide has an average particle diameter of from about 5 μm to about 25 μm, and a tap density of from about 1.0 g/cm 3 to about 3.0 g/cm 3 .
6. A positive electrode for a lithium secondary battery that comprises the lithium composite oxide as claimed in claim 4 .
7. A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode is the positive electrode as claimed in claim 6 .
8. The lithium composite oxide as claimed in claim 4 , wherein the compositional variation of Al is a standard deviation of 2% or less based on a sample measured at 20 randomly chosen points by EDS.
9. A method of preparing a nickel composite hydroxide for a lithium secondary battery, the method comprising:
mixing an M-containing compound, a chelating agent, and a first solvent to prepare a chelated M precursor mixture;
preparing a nickel precursor, a second solvent, and, optionally, a cobalt precursor, to prepare a nickel-containing precursor mixture; and
mixing the chelated M precursor mixture, the nickel-containing precursor mixture, a complexing agent, and a pH adjusting agent in an amount such that the prepared nickel is Ni 0.80 Co 0.10 Mn 0.05 Al 0.05 (OH) 2 or Ni 0.9 Co 0.05 Mn 0.025 Al 0.025 (OH) 2 .
10. The method as claimed in claim 9 , wherein the chelating agent is at least one selected from the group of acetylacetone, ethylenediaminetetraacetic acid, and benzoylacetone.
11. The method as claimed in claim 9 , wherein the M-containing compound is an aluminum alkoxide.
12. A method of preparing a lithium composite oxide for a lithium secondary battery, the method comprising: mixing a nickel composite hydroxide that is Ni 0.80 Co 0.10 Mn 0.05 Al 0.05 (OH) 2 or Ni 0.9 Co 0.05 Mn 0.025 Al 0.025 (OH) 2 and a lithium compound to prepare a mixture; and thermally treating the mixture to provide a lithium composite oxide that is LiNi 0.80 Co 0.10 Mn 0.05 Al 0.05 O 2 , or LiNi 0.9 Co 0.05 Mn 0.025 Al 0.025 O 2 .
13. The method as claimed in claim 12 , wherein the thermal treating is performed at a temperature of about 700° C. to about 900° C.