Method for manufacturing positive electrode active material, and secondary battery

Patent metadata

Field	Value
Publication number	US-2020176770-A1
Application number	US-201816624319-A
Country	US
Kind code	A1
Filing date	Jun 14, 2018
Priority date	Jun 26, 2017
Publication date	Jun 4, 2020
Grant date	—

Abstract

A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

First claim

1 - 10 . (canceled)

11 . A method for forming a positive electrode active material, comprising the steps of:
mixing a lithium source, a fluorine source, and a magnesium source to form a first mixture; mixing a composite oxide containing lithium, a transition metal, and oxygen with the first mixture to form a second mixture; and heating the second mixture.

12 . The method for forming a positive electrode active material according to claim 11 ,
wherein the positive electrode active material contains cobalt and nickel as the transition metal, and wherein a proportion of nickel atoms to a sum of cobalt atoms and nickel atoms is less than 0.1.

13 . The method for forming a positive electrode active material according to claim 11 , wherein the first mixture contains lithium fluoride as the lithium source and the fluorine source.

14 . The method for forming a positive electrode active material according to claim 13 ,
wherein the first mixture contains magnesium fluoride as the fluorine source and the magnesium source, wherein a molar ratio of the lithium fluoride to the magnesium fluoride is x:1, and wherein x is greater than or equal to 0.1 and less than or equal to 0.5.

15 . The method for forming a positive electrode active material according to claim 11 ,
wherein an atomic ratio of the transition metal in the composite oxide containing lithium, the transition metal, and oxygen in the second mixture to magnesium in the first mixture is 1:y, and wherein y is greater than or equal to 0.001 and less than or equal to 0.01.

16 . The method for forming a positive electrode active material according to claim 11 , wherein a heating temperature in a heating step of the second mixture is higher than or equal to 600° C. and lower than or equal to 950° C.

17 . The method for forming a positive electrode active material according to claim 11 , wherein a heating time in the heating step of the second mixture is longer than or equal to 2 hours.

18 . The method for forming a positive electrode active material according to claim 17 , wherein the heating time in the heating step of the second mixture is longer than or equal to 60 hours.

19 . A secondary battery comprising:
a positive electrode comprising the positive electrode active material formed by the method according to claim 11 ; and a negative electrode.

20 . A method for forming a positive electrode active material, comprising the steps of:
mixing a lithium source, a fluorine source, and a magnesium source to form a first mixture; mixing a composite oxide containing lithium, a transition metal, and oxygen with the first mixture to form a second mixture; and heating the second mixture, wherein in the composite oxide containing lithium, the transition metal, and oxygen, concentrations of elements other than lithium, the transition metal, or oxygen are less than or equal to 5,000 ppm wt when analysis is performed by a glow discharge mass spectroscopy.

21 . The method for forming a positive electrode active material according to claim 20 ,
wherein the positive electrode active material contains cobalt and nickel as the transition metal, and wherein a proportion of nickel atoms to a sum of cobalt atoms and nickel atoms is less than 0.1.

22 . The method for forming a positive electrode active material according to claim 20 , wherein the first mixture contains lithium fluoride as the lithium source and the fluorine source.

23 . The method for forming a positive electrode active material according to claim 22 ,
wherein the first mixture contains magnesium fluoride as the fluorine source and the magnesium source, wherein a molar ratio of the lithium fluoride to the magnesium fluoride is x:1, and wherein x is greater than or equal to 0.1 and less than or equal to 0.5.

24 . The method for forming a positive electrode active material according to claim 20 ,
wherein an atomic ratio of the transition metal in the composite oxide containing lithium, the transition metal, and oxygen in the second mixture to magnesium in the first mixture is 1:y, and wherein y is greater than or equal to 0.001 and less than or equal to 0.01.

25 . The method for forming a positive electrode active material according to claim 20 , wherein a heating temperature in a heating step of the second mixture is higher than or equal to 600° C. and lower than or equal to 950° C.

26 . The method for forming a positive electrode active material according to claim 20 , wherein a heating time in the heating step of the second mixture is longer than or equal to 2 hours.

27 . The method for forming a positive electrode active material according to claim 26 , wherein the heating time in the heating step of the second mixture is longer than or equal to 60 hours.

28 . A secondary battery comprising:
a positive electrode comprising the positive electrode active material formed by the method according to claim 20 ; and a negative electrode.

Assignees

• Semiconductor Energy Lab

Inventors

• Takahashi Masahiro
• Mikami Mayumi
• Momma Yohei
• Ochiai Teruaki
• Saitou Jyo

Classifications

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title

• C01P2002/77

  by unit-cell parameters, atom positions or structure diagrams · CPC title

• C01P2006/42

  Magnetic properties · CPC title

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title

• C01G51/66

  containing alkaline earth metals, e.g. SrCoO3 · CPC title