Positive electrode active material for nonaqueous electrolyte secondary batteries, and production method thereof

Patent metadata

Field	Value
Publication number	US-10854873-B2
Application number	US-201615555597-A
Country	US
Kind code	B2
Filing date	Mar 1, 2016
Priority date	Mar 3, 2015
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

A method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, includes: a mixing step of adding a W compound powder having a solubility A adjusted to 2.0 g/L or less to a Li-metal composite oxide powder and stirring in water washing of the composite oxide powder, the solubility A being determined by stirring the W compound in water having a pH of 12.5 at 25° C. for 20 minutes, the composite oxide powder being represented by the formula:

Li c Ni 1-x-y Co x M y O 2

and composed of primary and secondary particles, followed by solid-liquid separation, to thereby obtain a tungsten-containing mixture with the tungsten compound dispersed in the composite oxide powder; and a heat-treating step of heat-treating the mixture to uniformly disperse W on the surface of primary particles and thereby form a compound containing W and Li from the W and Li in the mixture, on the surface of primary particles.

First claim

The invention claimed is:

1. A positive electrode active material for nonaqueous electrolyte secondary batteries, the positive electrode active material being represented by a general formula (1):
Li a Ni 1-x-y Co x M y W z O 2+α ,

where 0≤x≤0.35, 0.0005≤z≤0.030, 0.97≤a≤1.25, 0≤α≤0.20, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al, wherein:
a lithium-metal composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles is a base material,
the positive electrode active material has voids between the primary particles of the lithium-metal composite oxide as the base material and a void content measured by image analysis of any cross section of the secondary particles with a scanning electron microscope (SEM) is 0.15 to 3%,
a compound containing lithium and tungsten is formed on a surface of the primary particles of the lithium-metal composite oxide as the base material, the compound containing lithium and tungsten is present on the surface of the primary particles of the lithium-metal composite oxide as coating thin film having a film thickness of 1 to 100 nm,
a specific surface area of the positive electrode active material, measured by a BET method, is 0.9 to 1.5 m 2 /g, and
when the voids between the primary particles at any 20 or more points are EDX analyzed in transmission-type electron microscope observation of a cross section of the secondary particles, tungsten is detected at 50% or more of the number of the voids analyzed.

2. The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein an amount of tungsten contained in the compound containing lithium and tungsten is 0.08 to 3.0 at% in terms of the number of W atoms with respect to the total number of atoms of Ni, Co and M contained in the lithium-metal composite oxide.

3. The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the lithium-metal composite oxide as the base material is represented by a general formula (2):
Li b Ni 1-x-y Co x M y O 2 ,

where 0≤x≤0.35, 0≤y≤0.35, and 0.95≤b≤1.20 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al.

4. A positive electrode active material for nonaqueous electrolyte secondary batteries, the positive electrode active material being represented by a general formula (1):
Li a Ni 1-x-y Co x M y W z O 2+α ,

where 0≤x≤0.35, 0≤y≤0.35, 0.0005≤z≤0.030, 0.97≤a≤1.25, 0≤α≤0.20, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al, wherein:
a lithium-metal composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles is a base material,
the positive electrode active material has voids between the primary particles of the lithium-metal composite oxide as the base material and a void content measured by image analysis of any cross section of the secondary particles with a scanning electron microscope (SEM) is 0.15 to 3%,
a compound containing lithium and tungsten is formed on a surface of the primary particles of the lithium-metal composite oxide as the base material, the compound containing lithium and tungsten is present on the surface of the primary particles of the lithium-metal composite oxide in both forms of thin film having a film thickness of 1 to 100 nm and fine particles having a particle size of 1 to 200 nm,
a specific surface area of the positive electrode active material, measured by a BET method, is 0.9 to 1.5 m 2 /g, and
when the voids between the primary particles at any 20 or more points are EDX analyzed in transmission-type electron microscope observation of a cross section of the secondary particles, tungsten is detected at 50% or more of the number of the voids analyzed.

5. The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 4 , wherein an amount of tungsten contained in the compound containing lithium and tungsten is 0.08 to 3.0 at% in terms of the number of W atoms with respect to the total number of atoms of Ni, Co and M contained in the lithium-metal composite oxide.

6. The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 4 , wherein the lithium-metal composite oxide as the base material is represented by a general formula (2):
Li b Ni 1-x-y Co x M y O 2 ,

where 0≤x≤0.35, 0≤y≤0.35, and 0.95≤b≤1.20 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al.

Assignees

• Sumitomo Metal Mining Co

Inventors

• Furuichi Yuki
• Komukai Tetsufumi

Classifications

• C01P2004/50

  Agglomerated particles · CPC title

• C01P2004/82

  two phases having the same anion, e.g. both oxidic phases · CPC title

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• H01M4/505

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

• H01M4/364

  as mixtures · CPC title