Positive electrode active material and battery including the same

1. A positive electrode active material comprising:

a lithium composite oxide,

wherein the lithium composite oxide includes a first lithium composite oxide and a second lithium composite oxide different from the first lithium composite oxide,

wherein the first lithium composite oxide has a crystal structure belonging to space group Fd-3m,

wherein at least a part of a surface of the first lithium composite oxide is covered with the second lithium composite oxide, and

wherein the second lithium composite oxide has a crystal structure belonging to space group Fd-3m,

wherein the first lithium composite oxide has an average composition represented by composition formula Li x Me y O α Q β ,

where

Me is at least one selected from the group consisting of Mn, Co, Ni, Fe, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, P, and Al,

Q is at least one selected from the group consisting of F, Cl, N, and S,

1.05≤ x ≤1.4,

0.6≤ y≤ 0.95,

1.2≤α≤2, and

0≤β≤0.8,

wherein the following mathematical formulas (I) and (II) are satisfied:

0.05≤Integrated intensity ratio I (18°-20°) /I (43°-46°) ≤0.90  (I), and

0.8≤Integrated intensity ratio I (63°-65°) /I (17°-19°) ≤2.0  (II),

where the integrated intensity ratio I (18°-20°) /I (43°-46°) is a ratio of an integrated intensity I (18°-20°) to an integrated intensity I (43°-46°) ,

the integrated intensity ratio I (63°-65°) /I (17°-19°) is a ratio of an integrated intensity I (63°-65°) to an integrated intensity I (17°-19°) ,

the integrated intensity I (18°-20°) is an integrated intensity of a first peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 18° and less than or equal to 20° in the X-ray diffraction pattern of the positive electrode active material,

the integrated intensity I (43°-46°) is an integrated intensity of a second peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 43° and less than or equal to 46° in the X-ray diffraction pattern of the positive electrode active material,

the integrated intensity I (63°-65°) is an integrated intensity of a third peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 63° and less than or equal to 65° in the X-ray diffraction pattern of the positive electrode active material, and

the integrated intensity I (17°-19°) is an integrated intensity of a fourth peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 17° and less than or equal to 19° in the X-ray diffraction pattern of the positive electrode active material.

2. The positive electrode active material according to claim 1 ,

wherein the integrated intensity ratio I (18°-20°) /I (43°-46°) is greater than or equal to 0.05 and less than or equal to 0.70.

3. The positive electrode active material according to claim 2 ,

wherein the integrated intensity ratio I (18°-20°) /I (43°-46°) is greater than or equal to 0.05 and less than or equal to 0.30.

4. The positive electrode active material according to claim 1 ,

wherein the integrated intensity ratio I (63°-65°) /I (17°-19°) is greater than or equal to 1.3 and less than or equal to 1.6.

5. A positive electrode active material comprising:

a lithium composite oxide,

wherein the lithium composite oxide includes a first lithium composite oxide and a second lithium composite oxide different from the first lithium composite oxide,

wherein the first lithium composite oxide is a multiphase mixture including a first phase having a crystal structure belonging to space group Fm-3m and a second phase having a crystal structure belonging to a space group other than space group Fm-3m,

wherein at least a part of a surface of the first lithium composite oxide is covered with the second lithium composite oxide, and

wherein the second lithium composite oxide has a crystal structure belonging to space group Fd-3m,

wherein the first lithium composite oxide has an average composition represented by composition formula Li x Me y O α Q β ,

where

Me is at least one selected from the group consisting of Mn, Co, Ni, Fe, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, P, and Al,

Q is at least one selected from the group consisting of F, Cl, N, and S,

1.05≤ x ≤1.4,

0.6≤ y≤ 0.95,

1.2≤α≤2, and

0≤β≤0.8,

wherein the following mathematical formulas (I) and (II) are satisfied:

0.05≤Integrated intensity ratio I (18°-20°) /I (43°-46°) ≤0.90  (I), and

0.8≤Integrated intensity ratio I (63°-65°) /I (17°-19°) ≤2.0  (II),

where the integrated intensity ratio I (18°-20°) /I (43°-46°) is a ratio of an integrated intensity I (18°-20°) to an integrated intensity I (43°-46°) ,

the integrated intensity ratio I (63°-65°) /I (17°-19°) is a ratio of an integrated intensity I (63°-65°) to an integrated intensity I (17°-19°) ,

the integrated intensity I (18°-20°) is an integrated intensity of a first peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 18° and less than or equal to 20° in the X-ray diffraction pattern of the positive electrode active material,

the integrated intensity I (43°-46°) is an integrated intensity of a second peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 43° and less than or equal to 46° in the X-ray diffraction pattern of the positive electrode active material,

the integrated intensity I (63°-65°) is an integrated intensity of a third peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 63° and less than or equal to 65° in the X-ray diffraction pattern of the positive electrode active material, and

the integrated intensity I (17°-19°) is an integrated intensity of a fourth peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 17° and less than or equal to 19° in the X-ray diffraction pattern of the positive electrode active material.

6. The positive electrode active material according to claim 5 ,

wherein the crystal structure of the second phase belongs to at least one selected from the group consisting of space group Fd-3m, space group R-3m, and space group C2/m.

7. The positive electrode active material according to claim 6 ,

wherein the crystal structure of the second phase belongs to space group Fd-3m.

8. The positive electrode active material according to claim 1 ,

wherein the second lithium composite oxide is mixed with at least a part of the surface of the first lithium composite oxide to form a solid solution.

9. The positive electrode active material according to claim 1 ,

wherein a molar ratio of the second lithium composite oxide to the first lithium composite oxide is less than or equal to 50%.

10. The positive electrode active material according to claim 9 ,

wherein the molar ratio is greater than or equal to 6% and less than or equal to 29%.

11. The positive electrode active material according to claim 1 ,

wherein the second lithium composite oxide has a thickness of greater than or equal to 0.1 nm and less than or equal to 100 nm.

12. The positive electrode active material according to claim 11 ,

wherein the second lithium composite oxide has a thickness of greater than or equal to 0.5 nm and less than or equal to 6 nm.

13. The positive electrode active material according to claim 1 ,

wherein the first lithium composite oxide further includes Mn.

14. The positive electrode active material according to claim 1 ,

wherein the first lithium composite oxide includes at least one selected from the group consisting of F, Cl, N, and S.

15. The positive electrode active material according to claim 1 ,

wherein the first lithium composite oxide includes F.

16. The positive electrode active material according to claim 1 ,

wherein the following two mathematical formulas are satisfied:

1.33≤α≤2, and

0≤β≤0.67.

17. The positive electrode active material according to claim 16 ,

wherein the following two mathematical formulas are satisfied:

1.33≤α≤1.9, and

0.1≤β≤0.67.

18. The positive electrode active material according to claim 1 ,

wherein the following two mathematical formulas are satisfied:

1.1≤ x≤ 1.25, and

0.75≤ y≤ 0.8.

19. The positive electrode active material according to claim 1 ,

wherein the lithium composite oxide is contained as a main component in the positive electrode active material.

20. A battery comprising:

a positive electrode including the positive electrode active material according to claim 1 ;

a negative electrode; and

an electrolyte.

21. The battery according to claim 20 ,

wherein the negative electrode includes at least one selected from the group consisting of:

(i) a negative electrode active material capable of occluding and releasing lithium ions; and

(ii) a material that allows lithium metal to dissolve from the material into the electrolyte during discharging and to precipitate on the material during charging, and

wherein the electrolyte is a nonaqueous electrolyte.

22. The battery according to claim 20 ,

wherein the negative electrode includes at least one selected from the group consisting of:

(i) a negative electrode active material capable of occluding and releasing lithium ions; and

(ii) a material that allows lithium metal to dissolve from the material into the electrolyte during discharging and to precipitate on the material during charging, and

wherein the electrolyte is a solid electrolyte.

23. The positive electrode active material according to claim 1 ,

wherein the second lithium composite oxide is represented by a composition formula (2),

Li a A b O c   (2)

where

A is at least one element selected from the group consisting of Ni, Co, Mn, Nb, Si, Al, P, S, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Mo, Ru, Ta, and W, and

the following three mathematical formulas are satisfied:

0< a≤ 2,

1.8≤ b≤ 2.2, and

3.5≤ c≤ 4.5.

24. The positive electrode active material according to claim 5 ,

wherein the second lithium composite oxide is represented by a composition formula (2),

Li a A b O c   (2)

where

A is at least one element selected from the group consisting of Ni, Co, Mn, Nb, Si, Al, P, S, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Mo, Ru, Ta, and W, and

the following three mathematical formulas are satisfied:

0< a≤ 2,

1.8≤ b≤ 2.2, and

3.5≤ c≤ 4.5.