POSITIVE ELECTRODE ACTIVE MATERIAL AND LITHIUM-ION SECONDARY BATTERY

Abstract

There is provided a positive electrode active material containing a lithium composite oxide having a layered rock salt structure containing Li, Ni, Co and Mn, and further containing at least one additive selected from Li3BO3, Li3PO4 and Li2SO4.

Description

Claims

1. A positive electrode active material to be used for a lithium ion secondary battery, wherein the positive electrode active material comprises a lithium composite oxide having a layered rock salt structure containing Li, Ni, Co and Mn, and further comprises at least one additive selected from Li3BO3, Li3PO4 and Li2SO4 andwherein a content of the additive is 0.1 to 10% by weight with respect to a total content of the lithium composite oxide and the additive.

2. The positive electrode active material according to claim 1, wherein the additive is present in a state of being deposited on at least a part of a grain boundary and of a surface of the lithium composite oxide.

3. The positive electrode active material according to claim 1, wherein the positive electrode active material is in a form of a sintered plate.

4. The positive electrode active material according to claim 3, wherein the sintered plate has a degree of orientation I[003]/I[104] that is defined as a ratio of a diffraction intensity I[003] derived from the (003) plane to a diffraction intensity I[104] derived from the (104) plane in an XRD profile measured by X-ray diffraction (XRD), of 1.2 to 3.6.

5. The positive electrode active material according to claim 3, wherein the sintered plate has an interfacial length per 1 µm2 of unit cross-sectional area of 0.45 µm or shorter.

6. The positive electrode active material according to claim 3, wherein the sintered plate has a porosity of 20 to 40%.

7. The positive electrode active material according to claim 3, wherein the sintered plate has a mean pore diameter of 3.5 µm or larger.

8. The positive electrode active material according to claim 3, wherein the sintered plate has a thickness of 30 to 300 µm.

9. The positive electrode active material according to claim 1, wherein the positive electrode active material is in a form of a powder.

10. The positive electrode active material according to claim 1, wherein a molar ratio of Li/(Ni+Co+Mn) in the positive electrode active material is 0.95 to 1.10.

11. A lithium ion secondary battery, comprising: a positive electrode layer comprising the positive electrode active material according to claim 1;a negative electrode layer comprising a negative electrode active material; anda LiOH·Li2SO4-based solid electrolyte interposed between the positive electrode layer and the negative electrode layer.

12. The lithium ion secondary battery according to claim 11, wherein the positive electrode active material is in a form of a sintered plate.

13. The lithium ion secondary battery according to claim 11, wherein the positive electrode layer comprises a particle of the positive electrode active material, a particle of the LiOH·Li2SO4-based solid electrolyte and an electron conductive auxiliary in a form of a mixture.

14. The lithium ion secondary battery according to claim 11, wherein the negative electrode active material is Li4Ti5O12.

15. The lithium ion secondary battery according to claim 11, wherein the LiOH·Li2SO4-based solid electrolyte comprises a solid electrolyte identified to be 3LiOH·Li2SO4 by X-ray diffraction.