Lithium lanthanum zirconium tantalum oxide garnet crystal and all-solid-state lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-10319985-B2
Application number	US-201515522654-A
Country	US
Kind code	B2
Filing date	Oct 23, 2015
Priority date	Oct 27, 2014
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

There are provided a lithium-containing garnet crystal high in density and ionic conductivity, and an all-solid-state lithium ion secondary battery using the lithium-containing garnet crystal. The lithium-containing garnet crystal has a chemical composition represented by Li7-xLa3Zr2-xTaxO12 (0.2≤x≤1), and has a relative density of 99% or higher, belongs to a cubic system, and has a garnet-related structure. The lithium-containing garnet crystal has a lithium ion conductivity of 1.0×10−3 S/cm or higher. Further, this solid electrolyte material has a lattice constant a of 1.28 nm≤a≤1.30 nm, and lithium ions occupy 96h-sites in the crystal structure. The all-solid-state lithium ion secondary battery has a positive electrode, a negative electrode and a solid electrolyte, and the solid electrolyte is constituted of the lithium-containing garnet crystal according to the present invention.

First claim

The invention claimed is:

1. A lithium-containing garnet crystal, comprising a chemical composition represented by Li 7-x La 3 Zr 2-x Ta x O 12 , where 0.2≤x≤1, a relative density of 99% or higher, belonging to a cubic system, a lattice constant a in which 1.28 nm≤a≤1.30 nm, and a garnet-related structure,
wherein lithium ions occupy only 96h-sites in a crystal structure of the lithium-containing garnet crystal, and
the crystal structure contains at least two 96h-sites.

2. The lithium-containing garnet crystal according to claim 1 , wherein the lithium-containing garnet crystal has a length of 2 centimeters or longer.

3. The lithium-containing garnet crystal according to claim 1 , wherein the lithium-containing garnet crystal has a relative density of 100%.

4. The lithium-containing garnet crystal according to claim 1 , wherein the lithium-containing garnet crystal has a lithium ion conductivity of 1.0×10 −3 S/cm or higher.

5. The lithium-containing garnet crystal according to claim 1 , wherein the lithium-containing garnet crystal satisfies at least one of the following (1) and (2):
(1) a Nyquist plot by an alternating current impedance measurement indicates no resistance component by crystal grain boundaries and indicates only a resistance component of a material of the lithium-containing garnet crystal itself; and
(2) diffraction spots emerge in a diffraction pattern in an X-ray diffraction measurement, a neutron diffraction measurement or an electron diffraction measurement using a single crystal of the lithium-containing garnet crystal.

6. A method for producing the lithium-containing garnet crystal of claim 1 having a chemical composition represented by Li 7-x La 3 Zr 2-x Ta x O 12 , where 0.2≤x≤1, the method comprising:
melting at least a part of a raw material having a chemical composition represented by Li (7-x)y La 3 Zr 2-x Ta x O 12 , where 0.2≤x≤1, 1<y≤2 to thereby form a melted zone; and
moving the melted zone at a moving speed of 8 mm/h or higher.

7. The method for producing a lithium-containing garnet crystal according to claim 6 , wherein the moving speed is 8 mm/h or higher and 19 mm/h or lower.

8. The method for producing a lithium-containing garnet crystal according to claim 6 ,
wherein the raw material in a rod-shape is melted while being rotated at a rotating speed of 30 rpm or higher in a plane perpendicular to a longitudinal direction thereof.

9. The method for producing a lithium-containing garnet crystal according to claim 8 , wherein the rotating speed is 30 rpm or higher and 60 rpm or lower.

10. An all-solid-state lithium ion secondary battery having a positive electrode, a negative electrode and a solid electrolyte, wherein the solid electrolyte comprises a lithium-containing garnet crystal according to claim 1 .

Assignees

• Aist

Inventors

• Kataoka Kunimitsu
• Akimoto Junji

Classifications

• H01M10/0525

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

• H01M2300/0071

  Oxides · CPC title

• H01B1/08

  oxides · CPC title

• C01G35/006

  Compounds containing tantalum, with or without oxygen or hydrogen, and containing two or more other elements · CPC title

• H01M10/0562 Primary

  Solid materials · CPC title