Positive electrode active material, method for manufacturing positive electrode active material, and secondary battery

Patent metadata

Field	Value
Publication number	US-11799080-B2
Application number	US-201816611791-A
Country	US
Kind code	B2
Filing date	May 11, 2018
Priority date	May 19, 2017
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

A positive electrode active material having high capacity and excellent cycle performance is provided. The positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charge and discharge as compared with those of a known positive electrode active material.

First claim

The invention claimed is:

1. A secondary battery comprising:
a positive electrode active material comprising lithium, cobalt, and oxygen,
wherein the positive electrode active material has a property that an X-ray diffraction pattern of the positive electrode active material has at least a first peak at 2θ of 19.30±0.20° and a second peak at 2θ of 45.55±0.10°, as analyzed by powder X-ray diffraction with a CuKα1 line in a charged state when charged with a lithium metal counter electrode at 25° C. and at 4.6 V, and
wherein the positive electrode active material further comprises magnesium, fluorine, and titanium,
wherein a discharge capacity retention rate of a coin cell comprising the positive electrode active material is higher than or equal to 74% and lower than or equal to 94% at the 50 th cycle of a cycle test at 25° C., the coin cell comprising a lithium metal counter electrode, and
wherein, for each cycle of the cycle test:
a CCCV charge is performed at a current value of 0.5 C and a battery voltage of 4.6V, with a termination current of 0.01 C,
a CC discharge is performed at a current value of 0.5 C until the battery voltage reaches 2.5V, and
1 C is set to 137 mA/g.

2. The secondary battery according to claim 1 ,
wherein a crystal structure having the first peak and the second peak is assigned to a crystal structure of a space group R-3m, and
wherein coordinate of cobalt is represented by (0, 0, 0.5) and coordinate of oxygen is (0, 0, x) in the crystal structure where x is defined as 0.20≤x≤0.25.

3. The secondary battery according to claim 1 ,
wherein, in an XPS analysis from a surface of the positive electrode active material, with a cobalt concentration set to 1, a magnesium concentration is greater than or equal to 0.4 and less than or equal to 1.5, and a fluorine concentration is greater than or equal to 0.05 and less than or equal to 1.5.

4. The secondary battery according to claim 1 ,
wherein the charged state is obtained by a CCCV charge.

5. The secondary battery according to claim 1 ,
wherein a median diameter of the positive electrode active material is greater than or equal to 2 μm and less than or equal to 40 μm.

6. The secondary battery according to claim 1 ,
wherein the coin cell comprises:
1 mol/L lithium hexafluorophosphate as an electrolyte,
an electrolyte solution in which ethylene carbonate and diethyl carbonate at a volume ratio of 3:7 and vinylene carbonate at a 2 wt % are mixed, and
a separator of 25-μm-thick polypropylene.

7. A secondary battery comprising:
a positive electrode active material comprising lithium, cobalt, and oxygen,
wherein the positive electrode active material has a property that an X-ray diffraction pattern of the positive electrode active material has at least a first peak at 2θ of 19.30±0.20° and a second peak at 2θ of 45.55±0.10°, as analyzed by powder X-ray diffraction with a CuKα1 line in a charged state when charged with a lithium metal counter electrode at 25° C. and at 4.6 V,
wherein the positive electrode active material further comprises magnesium and titanium,
wherein a discharge capacity retention rate of a coin cell comprising the positive electrode active material is higher than or equal to 74% and lower than or equal to 94% at the 50 th cycle of a cycle test at 25° C., the coin cell comprising a lithium metal counter electrode, and
wherein, for each cycle of the cycle test:
a CCCV charge is performed at a current value of 0.5 C and a battery voltage of 4.6V, with a termination current of 0.01 C,
a CC discharge is performed at a current value of 0.5 C until the battery voltage reaches 2.5V, and
1 C is set to 137 mA/g.

8. The secondary battery according to claim 7 ,
wherein a crystal structure having the first peak and the second peak is assigned to a crystal structure of a space group R-3m, and
wherein coordinate of cobalt is represented by (0, 0, 0.5) and coordinate of oxygen is (0, 0, x) in the crystal structure where x is defined as 0.20≤x≤0.25.

9. The secondary battery according to claim 7 ,
wherein, in an XPS analysis from a surface of the positive electrode active material, with a cobalt concentration set to 1, a magnesium concentration is greater than or equal to 0.4 and less than or equal to 1.5.

10. The secondary battery according to claim 7 ,
wherein the charged state is obtained by a CCCV charge.

11. The secondary battery according to claim 7 ,
wherein a median diameter of the positive electrode active material is greater than or equal to 2 μm and less than or equal to 40 μm.

12. The secondary battery according to claim 7 ,
wherein the coin cell comprises:
1 mol/L lithium hexafluorophosphate as an electrolyte,
an electrolyte solution in which ethylene carbonate and diethyl carbonate at a volume ratio of 3:7 and vinylene carbonate at a 2 wt % are mixed, and
a separator of 25-μm-thick polypropylene.

13. A secondary battery comprising:
a positive electrode active material comprising lithium, cobalt, and oxygen,
wherein the positive electrode active material has a property that an X-ray diffraction pattern of the positive electrode active material has at least a first peak at 2θ of 19.30±0.20° and a second peak at 2θ of 45.55±0.10°, as analyzed by powder X-ray diffraction with a CuKα1 line in a charged state when charged with a lithium metal counter electrode at 25° C. and at 4.6 V,
wherein the positive electrode active material further comprises magnesium and titanium,
wherein a discharge capacity retention rate of a coin cell comprising the positive electrode active material is higher than or equal to 86% and lower than or equal to 97% at the 30 th cycle of a cycle test at 25° C., the coin cell comprising a lithium metal counter electrode, and
wherein, for each cycle of the cycle test:
a CCCV charge is performed at a current value of 0.5 C and a battery voltage of 4.6V, with a termination current of 0.01 C,
a CC discharge is performed at a current value of 0.5 C until the battery voltage reaches 2.5V, and
1 C is set to 137 mA/g.

14. The secondary battery according to claim 13 ,
wherein a crystal structure having the first peak and the second peak is assigned to a crystal structure of a space group R-3m, and
wherein coordinate of cobalt is represented by (0, 0, 0.5) and coordinate of oxygen is (0, 0, x) in the crystal structure where x is defined as 0.20≤x≤0.25.

15. The secondary battery according to claim 13 ,
wherein, in an XPS analysis from a surface of the positive electrode active material, with a cobalt concentration set to 1, a magnesium concentration is greater than or equal to 0.4 and less than or equal to 1.5.

16. The secondary battery according to claim 13 ,
wherein a median diameter of the positive electrode active material is greater than or equal to 2 μm and less than or equal to 40 μm.

17. The secondary battery according to claim 13 , wherein the positive electrode active material further comprises fluorine.

18. The secondary battery according to claim 13 ,
wherein the charged state is obtained by a CCCV charge.

19. The secondary battery according to claim 13 ,
wherein the coin cell comprises:
1 mol/L lithium hexafluorophosphate as an electrolyte,
an electrolyte solution in which ethylene carbonate and diethyl carbonate at a volume ratio of 3:7 and vinylene carbonate at a 2 wt % are mixed, and
a separator of 25-μm-thick polypropylene.

20. A secondary battery comprising:
a positive electrode active material comprising lithium, cobalt, and

Assignees

• Semiconductor Energy Lab

Inventors

• Mikami Mayumi
• Uchida Aya
• Yoneda Yumiko
• Momma Yohei
• Takahashi Masahiro
• Ochiai Teruaki

Classifications

• H01M4/587

  for inserting or intercalating light metals · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M4/366

  as layered products · CPC title

• H01M4/131 Primary

  Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title