Positive electrode active material including lithium cobaltate coated with lithium titanate and magnesium oxide

Patent metadata

Field	Value
Publication number	US-10741828-B2
Application number	US-201715638449-A
Country	US
Kind code	B2
Filing date	Jun 30, 2017
Priority date	Jul 5, 2016
Publication date	Aug 11, 2020
Grant date	Aug 11, 2020

Abstract

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

First claim

The invention claimed is:

1. A lithium-ion secondary battery comprising a positive electrode active material layer comprising:
a positive electrode active material particle comprising a first transition metal, a second transition metal, a representative element, and fluorine,
wherein the representative element and the fluorine are present in a crack portion observed from a TEM image in the positive electrode active material particle.

2. The lithium-ion secondary battery according to claim 1 ,
wherein a relative value of a concentration of the second transition metal is greater than or equal to 0.05 and less than or equal to 0.4 when a surface of the positive electrode active material particle is subjected to an XPS analysis and a concentration of the first transition metal is defined as 1.

3. The lithium-ion secondary battery according to claim 1 ,
wherein a relative value of a concentration of the representative element is greater than or equal to 0.4 and less than or equal to 1.5 when a surface of the positive electrode active material particle is subjected to an XPS analysis and a concentration of the first transition metal is defined as 1.

4. The lithium-ion secondary battery according to claim 1 ,
wherein the first transition metal is cobalt,
wherein the second transition metal is titanium, and
wherein the representative element is magnesium.

5. A lithium-ion secondary battery comprising a positive electrode active material layer comprising:
a positive electrode active material particle comprising a first transition metal, a second transition metal, a representative element, and fluorine,
wherein the representative element and the fluorine are present in a portion which includes crystal defects observed from a TEM image in the positive electrode active material particle.

6. The lithium-ion secondary battery according to claim 5 ,
wherein a relative value of a concentration of the second transition metal is greater than or equal to 0.05 and less than or equal to 0.4 when a surface of the positive electrode active material particle is subjected to an XPS analysis and a concentration of the first transition metal is defined as 1.

7. The lithium-ion secondary battery according to claim 5 ,
wherein a relative value of a concentration of the representative element is greater than or equal to 0.4 and less than or equal to 1.5 when a surface of the positive electrode active material particle is subjected to an XPS analysis and a concentration of the first transition metal is defined as 1.

8. The lithium-ion secondary battery according to claim 5 ,
wherein the first transition metal is cobalt,
wherein the second transition metal is titanium, and
wherein the representative element is magnesium.

Assignees

• Semiconductor Energy Lab

Inventors

• Ochiai Teruaki
• Kawakami Takahiro
• Mikami Mayumi
• Momma Yohei
• Takahashi Masahiro
• TSURUTA Ayae

Classifications

• H01M2300/0028

  characterised by the solvent · CPC title

• H01M10/0568

  characterised by the solutes · CPC title

• H01M4/366

  as layered products · CPC title

• H01M10/0525 Primary

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

• H01M2004/028

  Positive electrodes · CPC title