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-11139468-B2
Application number	US-201816127445-A
Country	US
Kind code	B2
Filing date	Sep 11, 2018
Priority date	Sep 29, 2017
Publication date	Oct 5, 2021
Grant date	Oct 5, 2021

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 method for producing a cathode mixture, 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, which means that two separate peaks which are derived from the same kind of the crystal faces of the layered rock-salt crystalline phase are confirmed, both two peaks are the local maximums, and are convex upward, when the particle is subjected to X-ray diffraction measurement;
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 lower than 600° C., and sintering the cathode mixture at the temperature.

2. The method according to claim 1 ,
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 ⅓.

3. The method according to claim 1 ,
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.

4. The method according to claim 1 ,
wherein the lithium compound is at least one selected from the group consisting of lithium nitrate, lithium formate, lithium acetate, and lithium hydroxide.

5. The method according to claim 1 , wherein in said sintering the cathode mixture, the cathode mixture is heated either while or after pressurized.

6. The method according to claim 1 , wherein
the lithium compound is at least one selected from the group consisting of lithium formate, and lithium acetate.

7. The method according to claim 1 , wherein in said sintering the cathode mixture, the cathode mixture is heated while pressurized.

8. The method according to claim 1 , wherein
a temperature at which the cathode mixture is heated is no more than 400° C.

9. A method for producing an oxide solid-state battery, 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, which means that two separate peaks which are derived from the same kind of the crystal faces of the layered rock-salt crystalline phase are confirmed, both two peaks are the local maximums, and are convex upward, when the particle is subjected to X-ray diffraction measurement;
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 600° C., and sintering the cathode mixture over a surface of the layer of the oxide solid electrolyte at the temperature.

10. The method according to claim 9 , wherein
the oxide solid electrolyte includes garnet type lithium lanthanum zirconate.

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

12. The method according to claim 9 ,
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.

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

14. The method according to claim 9 ,
wherein in said sintering the cathode mixture over a surface of the layer of the oxide solid electrolyte, the laminate is heated while pressurized.

15. The method according to claim 9 , wherein
a temperature at which the laminate is heated is no more than 400° C.

Assignees

• Toyota Motor Co Ltd

Inventors

• Kawakami Masatsugu
• Ohta Shingo

Classifications

• H01M4/1391 Primary

  of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M4/131

  Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M10/0525

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

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M4/62

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