Method for manufacturing positive electrode active material, and secondary battery

Patent metadata

Field	Value
Publication number	US-11670770-B2
Application number	US-202017036740-A
Country	US
Kind code	B2
Filing date	Sep 29, 2020
Priority date	Jun 26, 2017
Publication date	Jun 6, 2023
Grant date	Jun 6, 2023

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

The invention claimed is:

1. A lithium ion secondary battery comprising:
a positive electrode active material comprising lithium cobalt oxide,
wherein a dQ/dV vs V curve in a range of greater than or equal to 4.0V and less than or equal to 4.8V is obtained by differentiating capacitance (Q) with respect to voltage (V) in a charge curve,
wherein the dQ/dV vs V curve comprises both a first peak and a second peak in a range of greater than or equal to 4.0V and less than or equal to 4.2V,
wherein the positive electrode active material has a crystal structure with a space group of P2/m between the first peak and the second peak,
wherein the dQ/dV vs V curve comprises a third peak in a range of greater than or equal to 4.5V and less than or equal to 4.7V, and
wherein a height of the third peak is less than a height of each of the first peak and the second peak.

2. A lithium ion secondary battery comprising:
a positive electrode active material comprising lithium cobalt oxide,
wherein a dQ/dV vs V curve in a range of greater than or equal to 4.0V and less than or equal to 4.8V is obtained by differentiating capacitance (Q) with respect to voltage (V) in a charge curve,
wherein the dQ/dV vs V curve comprises both a first peak and a second peak in a range of greater than or equal to 4.0V and less than or equal to 4.2V,
wherein the positive electrode active material has a crystal structure with a space group of P2/m between the first peak and the second peak,
wherein the dQ/dV vs V curve comprises a third peak, wherein the third peak represents a change in crystal structure of the positive electrode active material to a H1-3 type structure, and
wherein a height of the third peak is less than a height of each of the first peak and the second peak.

3. The lithium ion secondary battery according to claim 2 ,
wherein the third peak is in a range of greater than or equal to 4.5V and less than or equal to 4.7V.

4. The lithium ion secondary battery according to claim 1 ,
wherein the positive electrode active material comprises magnesium and fluorine in a surface portion,
wherein the positive electrode active material has a layered rock-salt crystal structure, and
wherein the charge curve is a property observed when the positive electrode active material with a lithium metal counter electrode is charged.

5. The lithium ion secondary battery according to claim 2 ,
wherein the positive electrode active material comprises magnesium and fluorine in a surface portion,
wherein the positive electrode active material has a layered rock-salt crystal structure, and
wherein the charge curve is a property observed when the positive electrode active material with a lithium metal counter electrode is charged.

Assignees

• Semiconductor Energy Lab

Inventors

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

Classifications

• C01P2004/51

  Particles with a specific particle size distribution · CPC title

• H01M4/366

  as layered products · CPC title

• C01P2002/76

  by a space-group or by other symmetry indications · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title

• C01G51/42 Primary

  containing alkali metals, e.g. LiCoO2 · CPC title