Cathode active material having manganese oxide and boron, cathode and lithium battery including cathode active material, and method of preparing the cathode active material
A cathode active material including: a lithium manganese oxide of which primary particles has a diameter of 1 μm or more and which has a spinel structure in which an X-ray diffraction (XRD) peak intensity ratio of I(111)/I(311) is 1.0 or more; and a boron element disposed at least one position selected from the group consisting of inside the primary particles and on surfaces of the primary particles.
1. A cathode active material comprising:
a lithium manganese oxide comprising primary particles having a diameter of 6 μm to 10 μm and which has a spinel structure in which an X-ray diffraction (XRD) peak intensity ratio of I(111)/I(311) is about 1.0 or more; and
a boron element disposed on at least one position selected from the group consisting of inside the primary particles and on surfaces of the primary particles,
wherein a specific surface area of the cathode active material is from about 0.2 m2/g to about 0.385 m2/g.
2. The cathode active material of claim 1 , wherein the XRD peak intensity ratio of I(111)/I(311) is from about 1.5 to about 3.0.
3. The cathode active material of claim 1 , wherein a full wide at half maximum (FWHM) of a peak at a bragg angle 2θ of 36.2±0.2° with respect to a CuK-alpha characteristic X-ray wavelength of 1.541 Å is about 0.6 or less.
4. The cathode active material of claim 1 , wherein an average secondary particle diameter (D50) of the lithium manganese oxide is from about 10 μm to about 20 μm.
5. The cathode active material of claim 1 , wherein an amount of the boron element is from about 1 ppm to about 2000 ppm based on the total weight of the cathode active material.
6. The cathode active material of claim 1 , wherein the lithium manganese oxide is represented by Formula 1 below:
Li x Mn 2-y M y O 4 <Formula 1>
where 0.9≦x≦1.4 and 0≦y≦1, and
wherein M comprises one or more metal selected from the group consisting of Al, Co, Ni, Cr, Fe, Zn, Mg, and Li.
7. The cathode active material of claim 1 , wherein the lithium manganese oxide is represented by Formula 2 below:
Li x Mn 2-y Al y O 4 <Formula 2>
wherein 0.9≦x≦1.4 and 0≦y≦1.
8. A cathode comprising the cathode active material of claim 1 .
9. A lithium battery comprising the cathode of claim 8 .
10. A method of preparing the cathode active material of claim 1 , the method comprising:
mixing a lithium precursor, a manganese precursor, a boron-based compound prepare a mixture; and
calcinating the mixture at a temperature of from about 700° C. to about 900° C.
11. The method of claim 10 , further comprising mixing a dopant precursor with the lithium precursor, the manganese precursor, and the boron-based compound to prepare the mixture.
12. The method of claim 10 , wherein the amount of the boron-based compound is from about 0.1 wt. % to about 10 wt. % based on the total weight of the mixture.
13. The method of claim 11 , wherein an amount of the boron-based compound is from about 0.1 wt. % to about 10 wt. % based on the total weight of the mixture.
14. The method of claim 10 , wherein the boron-based compound comprises at least one material selected from the group consisting of B 2 O 3 , H 3 BO 3 , and Li 2 B 4 O 7 .
15. The method of claim 11 , wherein the boron-based compound comprises at least one material selected from the group consisting of B 2 O 3 , H 3 BO 3 , and Li 2 B 4 O 7 .
16. The method of claim 11 , wherein the dopant precursor comprises at least one metal selected from the group consisting of Al, Co, Ni, Cr, Fe, Zn, Mg, and Li.
17. The method of claim 10 , wherein the calcination is performed in air for about 5 to about 30 hours.
18. The method of claim 11 , wherein the calcination is performed in air for about 5 to about 30 hours.