Cathode active material, positive electrode for lithium ion secondary battery, and lithium ion secondary battery
A cathode active material for a positive electrode for a lithium ion secondary battery, comprising a lithium-containing composite oxide represented by aLi(Li 1/3 Mn 2/3 )O 2 ·(1- a )LiMO 2 (M: at least one transition metal element selected from Ni, Co and Mn, and 0<a<1), wherein in an X-ray diffraction pattern of the lithium-containing composite oxide, the ratio of the height (H 020 ) of a peak of (020) plane assigned to a crystal structure with space group C2/m to the height (H 003 ) of a peak of (003) plane assigned to a crystal structure with space group R-3 m (i.e. H 020 /H 003 ) is at most 0.038, and the ratio of the height (H 110 ) of a peak of (110) plane assigned to a crystal structure with space group C2/m to the height (H 003 ) of a peak of (003) plane assigned to a crystal structure with space group R-3 m (i.e. H 110 /H 003 ) is at most 0.013.
1. A cathode active material, comprising:
a lithium-containing composite oxide represented by
aLi ( Li 1/3 Mn 2/3 ) O 2 ·(1- a )LiMO 2 ,
wherein
M is Ni Co and/or Mn, and
0< a ≤0.22 or 0.64 ≤a <1,
wherein, in an X-ray diffraction pattern of the lithium-containing composite oxide, the ratio (H 020 /H 003 ) of the height (H 020 ) of a (020) plane peak assigned to a crystal structure with a C2/m space group to the height (H 003 ) of a (003) plane peak assigned to a crystal structure with an R-3m space group in a range of from 0.005 to 0.038, and
wherein, in an X-ray diffraction pattern of the lithium-containing composite oxide, the ratio (H 110 /H 003 ) of the height (H 110 ) of a (110) plane peak assigned to the crystal structure with the C2/m space group to the height (H 003 ) of the (003) plane peak assigned to the crystal structure with the R-3m space group is at most 0.013.
2. The material of claim 1 , wherein, in the lithium-containing composite oxide, the ratio (Ni/X) of the molar amount of Ni to the total molar amount (X) of Ni, Co, and Mn is in a range of from 0.15 to 0.45,
wherein the ratio (Co/X) of the molar amount of Co to the total molar amount (X) of Ni, Co, and Mn is in a range of from 0 to 0.15, and
wherein the ratio (Mn/X) of the molar amount of Mn to the total molar amount (X) of Ni, Co, and Mn is in a range of from 0.55 to 0.85.
3. The material of claim 1 , having a specific surface area in a range of from 0.5 m 2 /g to 4 m 2 /g.
4. The material of claim 1 , having a volume-based accumulative 50% size (D 50 ) in a range of from 3 μm to 15 μm.
5. The material of claim 1 , wherein, in an X-ray diffraction pattern of the lithium-containing composite oxide, the crystallite diameter obtained by the Scherrer equation from the (003) plane peak assigned to the crystal structure with the R-3m space group is in a range of from 30 nm to 120 nm.
6. The material of claim 1 , wherein, in an X-ray diffraction pattern of the lithium-containing composite oxide, the crystallite diameter obtained by the Scherrer equation from the (110) plane peak assigned to the crystal structure with the R-3m space group is in a range of from 10 nm to 80 nm.
7. A positive electrode configured for a lithium ion secondary battery, comprising:
the cathode active material of claim 1 ;
an electrically conductive material; and
a binder.
8. A lithium ion secondary battery, comprising:
the electrode of claim 7 ;
a negative electrode; and
a non-aqueous electrolyte.
9. The material of claim 1 , wherein, in the lithium-containing composite oxide M comprises Co and optionally Ni and/or Mn.
10. The material of claim 1 , wherein, in the lithium-containing composite oxide,
0.2≤ a≤ 0.22.
11. The material of claim 1 , wherein, in the lithium-containing composite oxide,
0< a ≤0.22.
12. The material of claim 1 , wherein, in the lithium-containing composite oxide,
M is Ni α Co β Mn γ ,
α is in a range of from 0.5 to 0.833,
β is in a range from 0 to 0.75,
γ is in a range of from 0.167 to 0.5, and
α>γ.
13. The material of claim 1 , wherein the ratio (H 020 /H 003 ) is in a range of from 0.005 to 0.0365.
14. The material of claim 1 , wherein the ratio (H 020 /H 003 ) is in a range of from 0.005 to 0.035.
15. The material of claim 1 , wherein the ratio (H 110 /H 003 ) is at most 0.0126.
16. The material of claim 1 , wherein the ratio (H 110 /H 003 ) is at most 0.0122.
17. The material of claim 1 , wherein, in an X-ray diffraction pattern of the lithium-containing composite oxide, the crystallite diameter obtained by the Scherrer equation from the (003) plane peak assigned to the crystal structure with the R-3m space group is in a range of from 50 nm to 110 nm.
18. The material of claim 1 , wherein, in an X-ray diffraction pattern of the lithium-containing composite oxide, the crystallite diameter obtained by the Scherrer equation from the (003) plane peak assigned to the crystal structure with the R-3m space group is in a range of from 15 nm to 70 nm.
19. The material of claim 1 , having a volume-based accumulative 50% size (D 50 ) in a range of from 3 μm to 12 μm.
20. The material of claim 1 , wherein the volume-based accumulative 50% size (D 50 ) in a range of from 3 μm to 10 μm.
21. The material of claim 1 , wherein, in the lithium-containing composite oxide, 0.64≤a<1.
22. The material of claim 1 , wherein, in the lithium-containing composite oxide, 0.64≤a≤0.75.