Positive electrode for lithium secondary battery, manufacturing method thereof, and lithium secondary battery

Patent metadata

Field	Value
Publication number	US-9252419-B2
Application number	US-201213602350-A
Country	US
Kind code	B2
Filing date	Sep 4, 2012
Priority date	Sep 9, 2011
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.

First claim

What is claimed is:

1. A positive electrode for a lithium secondary battery, comprising:
a positive electrode current collector; and
a positive electrode active material layer over the positive electrode current collector,
wherein the positive electrode active material layer includes:
a rectangular parallelepiped or substantially rectangular parallelepiped particle of a lithium-containing composite oxide having an olivine structure; and
a graphene oxide, and

wherein a b-axis of the rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide having the olivine structure is oriented vertically to a surface of the positive electrode current collector,
wherein a number of rectangular parallelepiped or substantially rectangular parallelepiped particle having b-axis thereof oriented vertically to the surface of the positive electrode current collector is larger than a number of rectangular parallelepiped or substantially rectangular parallelepiped particle oriented in other axes directions, and
wherein a peak intensit ratio of a (020) diffraction to a (101) diffraction of the lithium-containing composite oxide having the olivine structure in a X-ray diffraction spectrum is greater than or equal to 4.5 and less than or equal to 5.5.

2. The positive electrode for a lithium secondary battery according to claim 1 , wherein the lithium-containing composite oxide having the olivine structure is lithium iron phosphate.

3. The positive electrode for a lithium secondary battery according to claim 1 , wherein the rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide having the olivine structure is a single crystal particle.

4. The positive electrode for a lithium secondary battery according to claim 3 , wherein a length in a b-axis direction of the rectangular parallelepiped or substantially rectangular parallelepiped of the lithium-containing composite oxide having the olivine structure is shorter than lengths in an a-axis direction and a c-axis direction of the rectangular parallelepiped or substantially rectangular parallelepiped of the lithium-containing composite oxide having the olivine structure.

5. The positive electrode for a lithium secondary battery according to claim 1 , wherein the graphene oxide is multilayer graphene oxide including 2 to 100graphene oxide sheets.

6. The positive electrode for a lithium secondary battery according to claim 1 , wherein the graphene oxide is reduced.

7. A lithium secondary battery, comprising:
a negative electrode;
an electrolyte solution; and
a positive electrode comprising:
a positive electrode current collector; and
a positive electrode active material layer over the positive electrode current collector,

wherein the positive electrode active material layer includes:
a rectangular parallelepiped or substantially rectangular parallelepiped particle of a lithium-containing composite oxide having an olivine structure; and
a graphene oxide, and

wherein a b-axis of the rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide having the olivine structure is oriented vertically to a surface of the positive electrode current collector,
wherein a number of rectangular parallelepiped or substantially rectangular parallelepiped particle having b-axis thereof oriented vertically to the surface of the positive electrode current collector is larger than a number of rectangular parallelepiped or substantially rectangular parallelepiped particle oriented in other axes directions, and
wherein a peak intensity ratio of a (020) diffraction to a (101) diffraction of the lithium-containing composite oxide having the olivine structure in a X-ray diffraction spectrum is greater than or equal to 4.5 and less than or equal to 5.5.

8. The lithium secondary battery according to claim 7 , wherein the lithium-containing composite oxide having the olivine structure is lithium iron phosphate.

9. The lithium secondary battery according to claim 7 . wherein the rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide having the olivine structure is a single crystal particle.

10. The lithium secondary battery according to claim 9 , wherein a length in a b-axis direction of the rectangular parallelepiped or substantially rectangular parallelepiped of the lithium-containing composite oxide having the olivine structure is shorter than lengths in an a-axis direction and a c-axis direction of the rectangular parallelepiped or substantially rectangular parallelepiped of the lithium-containing composite oxide having the olivine structure.

11. The lithium secondary battery according to claim 7 , wherein the graphene oxide is multilayer graphene oxide including 2 to 100 graphene oxide sheets.

12. The lithium secondary battery according to claim 7 , wherein the graphene oxide is reduced.

13. The positive electrode for a lithium secondary battery according to claim 1 , wherein the lithium-containing composite oxide having the olivine structure is coated with the graphene oxide or multilayer graphene oxide.

14. The positive electrode for a lithium secondary battery according to claim 1 ,
wherein the positive electrode active material layer includes a first rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide and a second rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide;
wherein the second rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide is stacked on the first rectangular parallelepiped or substantially parallelepiped particle of the lithium-containing composite oxide, and
wherein a b-axis of the first rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide and a b-axis of the second rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide are oriented vertically to the surface of the positive electrode current collector.

15. The lithium secondary battery according to claim 7 , wherein the lithium-containing composite oxide having the olivine structure is coated with the graphene oxide or multilayer graphene oxide.

16. The lithium secondary battery according to claim 7 ,
wherein the positive electrode active material layer includes a first rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide and a second rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide;
wherein the second rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide is stacked on the first rectangular parallelepiped or substantially parallelepiped particle of the lithium-containing composite oxide, and
wherein a b-axis of the first rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide and a b-axis of the second rectangular parallelepiped or substantially rectangular parallelepiped particle of the lithium-containing composite oxide are oriented vertically to the surface of the positive electrode current collector.

Assignees

• Miwa Takuya
• Inoue Nobuhiro
• Nomoto Kuniharu
• Momo Junpei
• Semiconductor Energy Lab

Inventors

• Miwa Takuya
• Inoue Nobuhiro
• Nomoto Kuniharu
• Momo Junpei

Classifications

• C01B31/043

  Chemistry & Metallurgy · mapped topic

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• H01M4/04 Primary

  Processes of manufacture in general · CPC title

• C01B25/45

  containing plural metal, or metal and ammonium · CPC title

• C01B25/306 Primary

  from phosphates · CPC title