Electrode active material, preparation method thereof, and electrode and lithium battery containing the same
An electrode active material includes a core capable of intercalating and deintercalating lithium; and a surface treatment layer disposed on at least a portion of a surface of the core, wherein the surface treatment layer includes a lithium-free oxide having a spinel structure, and an intensity of an X-ray diffraction peak corresponding to impurity phase of the lithium-free oxide, when measured using Cu—Kα radiation, is at a noise level of an X-ray diffraction spectrum or less.
1. An electrode active material, consisting of:
a core capable of intercalating and deintercalating lithium; and
a surface treatment layer that completely covers the core,
wherein the surface treatment layer comprises a lithium-free oxide having a spinel structure, and an intensity of an X-ray diffraction peak corresponding to impurity phases of the lithium-free oxide, when measured using Cu—Kα radiation, is at a noise level of an X-ray diffraction spectrum or less, wherein,
the lithium-free oxide is one or more selected from SnMg 2 O 4 SnZ 2 O 4 , MgAl 2 O 4 , CuAl 2 O 4 , Zn Al 2 O 4 and NiAl 2 O 4 , and wherein
the core comprises one or more compounds selected from compounds expressed by the following Formulas 4 to 8:
Li x Co 1−y M y O (2−α) X α , Formula 4
Li x Co (1−y−z) Ni y M z O (2−α) X α , Formula 5
Li x Mn (2−y) M y O (4−a) X α , Formula 6
Li x Co (2−y) M y O (4−α) X α , and Formula 7
Li x Me y M z PO (4−α) X α Formula 8
wherein 0.90≤x≤1.1, 0≤y≤0.9, 0≤z≤0.5, (1−y−z)>0, 0≤α≤2;
Me is one or more metals selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, and B;
M is one or more elements selected from Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni, Mn, Cr, Fe, Mg, Sr, V, and a rare-earth element; and X is an element selected from O, F, S, and P.
2. The electrode active material of claim 1 , wherein the lithium-free oxide has an X-ray diffraction peak at about 35.5°±2.0° two-theta for a peak corresponding to a (311) crystal face, when measured using Cu—Kα radiation, and a full width at half maximum of the X-ray diffraction peak corresponding to the (311) crystal face is less than 0.3° two-theta.
3. The electrode active material of claim 1 , wherein the lithium-free oxide has an X-ray diffraction peak at about 35.5°±2.0° two-theta for a peak corresponding to a (311) crystal face, when measured using Cu—Kα radiation, and a full width at half maximum of the X-ray diffraction peak corresponding to the (311) crystal face is about 0.220° two-theta to about 0.270° two-theta.
4. The electrode active material of claim 1 , wherein a ratio of an intensity of an X-ray diffraction peak corresponding to a (440) crystal face to an intensity of an X-ray diffraction peak corresponding to a (311) crystal face is about 0.3 or more.
5. The electrode active material of claim 1 , wherein a ratio of an intensity of an X-ray diffraction peak corresponding to a (511) crystal face to an intensity of an X-ray diffraction peak corresponding to a (400) crystal face is about 0.25 or more.
6. The electrode active material of claim 5 , wherein a ratio of an intensity of an X-ray diffraction peak corresponding to a (511) crystal face to an intensity of an X-ray diffraction peak corresponding to a (440) crystal face is about 0.5 or more.
7. The electrode active material of claim 5 , wherein a content of the lithium-free oxide is about 10 weight percent or less, based on a total weight of the electrode active material.
8. The electrode active material of claim 5 , wherein a thickness of the surface treatment layer is about 1 angstrom to about 1 micrometer.
9. An electrode comprising an electrode active material according to claim 5 .
10. A lithium battery comprising an electrode according to claim 9 .