Cathode active material, cathode mixture, method for producing cathode active material, method for producing cathode, and method for producing oxide solid-state battery

Patent metadata

Field	Value
Publication number	US-2019103603-A1
Application number	US-201816127445-A
Country	US
Kind code	A1
Filing date	Sep 11, 2018
Priority date	Sep 29, 2017
Publication date	Apr 4, 2019
Grant date	—

Abstract

Disclosed is a cathode active material that can lower sintering temperature, the cathode active mated al including a particle of a lithium containing composite oxide having a layered rock-salt crystalline phase, wherein the layered rock-salt crystalline phase is partially deficient in lithium, a percentage of deficient lithium in the layered rock-salt crystalline phase in a surface portion of the particle is higher than that in the layered rock-salt crystalline phase inside the particle, and the particle includes two phases that are different in lattice constant as the layered rock-salt crystalline phase.

First claim

What is claimed is:

1 . A cathode active material that comprises a particle of lithium containing composite oxide having a layered rock-salt crystalline phase, wherein
the layered rock-salt crystalline phase is partially deficient in lithium, a percentage of deficient lithium in the layered rock-salt crystalline phase in a surface portion of the particle is higher than that in the layered rock-salt crystalline phase inside the particle, and the particle includes two phases that are different in lattice constant as the layered rock-salt crystalline phase.

2 . A cathode mixture comprising:
the cathode active material according to claim 1 ; and a lithium compound whose melting point is lower than that of the cathode active material.

3 . The cathode mixture according to claim 2 , wherein
the lithium compound is at least one selected from the group consisting of lithium nitrate lithium formate, lithium acetate, and lithium hydroxide.

4 . A method for producing a cathode active material, the method comprising:
contacting a particle of a lithium containing composite oxide having a layered rock-salt crystalline phase with an acid solution, and extracting lithium from a surface of the particle to the acid solution, to obtain a cathode active material that includes two phases different in lattice constant as the layered rock-salt crystalline phase.

5 . The method according to claim 4 ,
wherein a ratio (A1/B1) of a number of hydrogen ions included in the acid solution (A1) to a number of lithium atoms included in the particle before the particle is contacted with the acid solution (B1) is no more than 1/3.

6 . The method according to claim 4 ,
wherein a ratio (B2/B1) of a number of lithium atoms included in the particle after the particle is contacted with the acid solution (B2) to a number of the lithium atoms included in the particle before the particle is contacted with the acid solution (B1) is no less than 0.9 and less than 1.0.

7 . A method for producing a cathode, comprising:
mixing the cathode active material according to claim 1 with a lithium compound whose melting point is lower than that of the cathode active material, to obtain a cathode mixture; and heating the cathode mixture at a temperature of no less than the melting point of the lithium compound, and sintering the cathode mixture.

8 . A method for producing a cathode, comprising:
producing a cathode active material according to the method of claim 4 ; mixing the cathode active material with a lithium compound whose melting point is lower than that of the cathode active material, to obtain a cathode mixture; and heating the cathode mixture at a temperature of no less than the melting point of the lithium compound, and sintering the cathode mixture.

9 . The method according to claim 7 ,
wherein the lithium compound is at least one selected from the group consisting of lithium nitrate, lithium formate, lithium acetate, and lithium hydroxide.

10 . The method according to claim 7 , wherein in said sintering the cathode mixture, the cathode mixture is heated either while or after pressurized.

11 . A method for producing oxide solid-state battery, comprising:
mixing the cathode active material according to claim 1 with a lithium compound whose melting point is lower than that of the cathode active material, to obtain a cathode mixture; layering a layer that consists of the cathode mixture, and a layer of an oxide solid electrolyte, to obtain a laminate; and heating the laminate at a temperature of no less than the melting point of the lithium compound and lower than reaction temperature of the cathode mixture with the oxide solid electrolyte, and sintering the cathode mixture over a surface of the layer of the oxide solid electrolyte.

12 . A method for producing an oxide solid-state battery, comprising:
producing a cathode active material according to the method of claim 4 ; mixing the cathode active material with a lithium compound whose melting point is lower than that of the cathode active material, to obtain a cathode mixture; layering a layer that consists of the cathode mixture, and a layer of an oxide solid electrolyte, to obtain a laminate; and heating the laminate at a temperature of no less than the melting point of the lithium compound and lower than reaction temperature of the cathode mixture with the oxide solid electrolyte, and sintering the cathode mixture over a surface of the layer of the oxide solid electrolyte.

13 . The method according to claim 11 , wherein
the oxide solid electrolyte includes garnet type lithium lanthanum zirconate, and a temperature at which the laminate is heated is no less than the melting point of the lithium compound and lower than 600° C.

14 . The method according claim 11 ,
wherein the lithium compound is at least one selected from the group consisting lithium nitrate, lithium formate, lithium acetate, and lithium hydroxide.

15 . The method according claim 11 ,
wherein in said sintering the cathode mixture over a surface of the layer of the oxide solid electrolyte, the laminate is heated either while or after pressurized.

Assignees

• Toyota Motor Co Ltd

Inventors

• Kawakami Masatsugu
• Ohta Shingo

Classifications

• H01M4/62

  Selection of inactive substances as ingredients for active masses, e.g. binders, fillers · CPC title

• H01M10/0562

  Solid materials · CPC title

• 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

• H01M10/058

  Construction or manufacture · CPC title