Method for evaluating a characteristic of a nonaqueous electrolyte secondary battery positive electrode active material

Patent metadata

Field	Value
Publication number	US-11855283-B2
Application number	US-202217962637-A
Country	US
Kind code	B2
Filing date	Oct 10, 2022
Priority date	Oct 31, 2017
Publication date	Dec 26, 2023
Grant date	Dec 26, 2023

Abstract

The present invention provides a method of evaluating a characteristic of a positive electrode active material for non-aqueous electrolyte secondary batteries, including a lithium-metal composite oxide powder including a secondary particle configured by aggregating primary particles containing lithium, nickel, manganese, and cobalt, or a lithium-metal composite oxide powder including both the primary particles and the secondary particle. The secondary particle has a porous internal structure. The characteristic being evaluated is a slurry pH, a soluble lithium content rate, or a porosity.

First claim

The invention claimed is:

1. A method for evaluating a characteristic of a positive electrode active material for non-aqueous electrolyte secondary batteries,
the positive electrode active material comprising:
a lithium-metal composite oxide powder including a secondary particle configured by aggregating primary particles containing lithium, nickel, manganese, and cobalt, or
a lithium-metal composite oxide powder including both the primary particles and the secondary particle, wherein
the secondary particle has a porous internal structure,
a mixed slurry being a mixture of water and the lithium-metal composite oxide powder as a slurry solid body component has a pH of 11.5 or less at a time when the mixed slurry contains the lithium-metal composite oxide powder at a slurry concentration of 50 [g/L],
the lithium-metal composite oxide powder contains soluble lithium at a content rate of 0.5 [% by mass] or less,
the lithium-metal composite oxide powder has a specific surface area of 3.0 to 4.0 [m 2 /g], and
the secondary particle has a porosity of more than 50 to 80 [%],

the characteristic being a slurry pH indicating a pH of a slurry containing water and the positive electrode active material as a solid body component,
the method comprising:
adding the positive electrode active material to the water so that the slurry contains the positive electrode active material at a concentration of 50 [g/L];
maintaining a state where the slurry is stirred for 30 minutes; and
obtaining the slurry pH by measuring the pH of the slurry with a pH meter in the state where the slurry is stirred.

2. A method for evaluating a characteristic of a positive electrode active material for non-aqueous electrolyte secondary batteries,
the positive electrode active material comprising:
a lithium-metal composite oxide powder including a secondary particle configured by aggregating primary particles containing lithium, nickel, manganese, and cobalt, or
a lithium-metal composite oxide powder including both the primary particles and the secondary particle, wherein
the secondary particle has a porous internal structure,
a mixed slurry being a mixture of water and the lithium-metal composite oxide powder as a slurry solid body component has a pH of 11.5 or less at a time when the mixed slurry contains the lithium-metal composite oxide powder at a slurry concentration of 50 [g/L],
the lithium-metal composite oxide powder contains soluble lithium at a content rate of 0.5 [% by mass] or less,
the lithium-metal composite oxide powder has a specific surface area of 3.0 to 4.0 [m 2 /g], and
the secondary particle has a porosity of more than 50 to 80 [%],

the characteristic being a soluble lithium content rate indicating a lithium amount contained in the positive electrode active material soluble in water being a liquid component of a slurry containing the positive electrode active material and the water,
the method comprising:
adding the positive electrode active material to the water so that the slurry contains the positive electrode active material at a concentration of 20 [g/L];
maintaining a state where the slurry is stirred for 10 minutes;
filtering the slurry; and
obtaining the soluble lithium content rate by measuring the lithium contained in an obtained filtrate with an ICP optical emission spectrometer.

3. A method for evaluating a characteristic of a positive electrode active material for non-aqueous electrolyte secondary batteries,
the positive electrode active material comprising:
a lithium-metal composite oxide powder including a secondary particle configured by aggregating primary particles containing lithium, nickel, manganese, and cobalt, or
a lithium-metal composite oxide powder including both the primary particles and the secondary particle, wherein
the secondary particle has a porous internal structure,
a mixed slurry being a mixture of water and the lithium-metal composite oxide powder as a slurry solid body component has a pH of 11.5 or less at a time when the mixed slurry contains the lithium-metal composite oxide powder at a slurry concentration of 50 [g/L],
the lithium-metal composite oxide powder contains soluble lithium at a content rate of 0.5 [% by mass] or less,
the lithium-metal composite oxide powder has a specific surface area of 3.0 to 4.0 [m 2 /g], and
the secondary particle has a porosity of more than 50 to 80 [%],

the characteristic being a porosity representing a measure of an amount of an internal space of the positive electrode active material,
the method comprising:
a first process of embedding a lithium-metal composite oxide in a resin;
a second process of exposing a cross section of a particle of the lithium-metal composite oxide embedded in the resin by cutting the particle using a cross-section polisher by argon sputtering;
a third process of observing the exposed cross section of the particle using a scanning electron microscope; and
a fourth process of determining a porosity by analyzing an image of the observed cross section of the particle with image analysis software so that a void of the image is analyzed as a black part and a dense portion is analyzed as a white part and calculating an area ratio of the black part/(the black part+the white part) for the cross section of any 20 or more of the particles.

Assignees

• Sumitomo Metal Mining Co

Inventors

• Oshita Hiroko
• Ryoshi Kazuomi
• Aida Taira
• Yamaji Koji
• Okada Jiro

Classifications

• C01G53/82

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

• H01M4/505 Primary

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title

• C01G53/50

  of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 · CPC title

• G01N15/08

  Investigating permeability, pore-volume, or surface area of porous materials · CPC title

• G01N21/71

  thermally excited · CPC title