Positive active material for rechargeable lithium battery, method of preparing same, and rechargeable lithium battery including the same
A positive active material for a rechargeable lithium battery including a core including at least one selected from a nickel-based composite oxide represented by Chemical Formula 1 or a lithium manganese oxide represented by Chemical Formula 2; and a coating layer on a surface of the core and including a lithium metal oxide represented by Chemical Formula 3, the positive active material having a peak at a 2θ value of about 19° to about 22° and another peak at a 2θ value of about 40° to about 45° in an X-ray diffraction pattern using a CuKα ray, is disclosed. A method of preparing the same, and a rechargeable lithium battery including the same, are also disclosed. LiNi x Co y Mn 1-x-y O 2 Chemical Formula 1 Li a Mn b O c Chemical Formula 2 Li 2 MO 3 Chemical Formula 3 In Chemical Formulae 1 to 3, x, y, a, b, c, and M are the same as in the detailed description.
1. A positive active material for a rechargeable lithium battery, comprising:
a core comprising a nickel-based composite oxide represented by Chemical Formula 1; and
a coating layer on a surface of the core and comprising a lithium metal oxide represented by Chemical Formula 3,
wherein the lithium metal oxide represented by Chemical Formula 3 on the surface of the core has a peak at a 2θ value of 20° to about 22° and another peak at a 2θ value of about 40° to about 45° in an X-ray diffraction pattern using a CuKα ray:
LiNi x Co y Mn 1-x-y O 2 Chemical Formula 1
wherein 0.56≤x≤0.8, and 0.1≤y≤0.8, and
Li 2 MO 3 Chemical Formula 3
wherein the nickel-based composite oxide represented by Chemical Formula 1 comprises Mn,
wherein M is Zr,
wherein the positive active material has an exothermic main peak in a range of 300° C. to 311° C. as measured by differential scanning calorimetry,
wherein the positive active material has an intensity ratio of the peak at a 28 value of 20° to about 22° to the other peak at a 2θ value of about 40° to about 45° of about 2.0 to about 3.0, and
wherein the positive active material is formed using a sol-gel method.
2. The positive active material of claim 1 , wherein the positive active material has an intensity ratio of the peak at a 2θ value of about 20° to about 22° to the other peak at a 2θ value of about 40° to about 45° of about 2.0 to about 2.5.
3. The positive active material of claim 1 , wherein the positive active material comprises about 98.5 wt % to about 99.9 wt % of the core.
4. The positive active material of claim 1 , wherein the positive active material comprises about 0.1 wt % to about 1.5 wt % of the coating layer.
5. A rechargeable lithium battery comprising
a positive electrode comprising the positive active material according to claim 1 ;
a negative electrode; and
an electrolyte.