Positive electrode active material, positive electrode, and nonaqueous-electrolyte secondary battery

Patent metadata

Field	Value
Publication number	US-9293234-B2
Application number	US-201113809551-A
Country	US
Kind code	B2
Filing date	Jun 16, 2011
Priority date	Jul 12, 2010
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

Provided is a positive electrode active material giving nonaqueous-electrolyte secondary batteries superior in cycle characteristics. The positive electrode active material according to the present invention includes a lithium-containing composite metal oxide having the composition represented by the following General Formula (1):

Li z Fe 1-x M x P 1-y Si y O 4   (1)

(wherein M is at least one metal element selected from Zr, Sn, Y, and Al, 0.05<x<1, and 0.05<y<1), characterized in that: the positive electrode active material is in the single crystalline phase of the lithium-containing composite oxide represented by General Formula (1) when 1>z>0.9 to 0.75 or 0.25 to 0.1>z>0;

the positive electrode active material has two crystalline phases of the lithium-containing composite oxides represented by the following General Formulae (2) and (3) when 0.9 to 0.75>z>0.25 to 0.1:

Li a Fe 1-x M x P 1-y Si y O 4   (2)

(wherein 0.75 to 0.9≦a≦1.00, 0.05<x<1, and 0.05<y<1); and

Li b Fe 1-x M x P 1-y Si y O 4   (3)

(wherein, 0≦b≦0.1 to 0.25+x, 0.05<x<1, and 0.05<y<1), and

when the product of the lengths of the b and c axes of the unit cell of the lithium-containing composite oxide of General Formula (2) is designated as bc1 and the product of the lengths of the b and c axes of the unit cell of the lithium-containing composite oxide of General Formula (3) as bc2, α, which is defined by equation α=(bc2)/(bc1), is 0.99<α<1.01.

First claim

What is claimed is:

1. A positive electrode active material for nonaqueous-electrolyte secondary batteries, comprising a lithium-containing composite oxide represented by the following General Formula (1):
Li z Fe 1-x M x P 1-y Si y O 4   (1)

(wherein M is at least one metal element selected from Zr, Sn, Y, and Al, 0.05<x<1, and 0.05<y<1), characterized in that:
the lithium-containing composite oxide is in the single phase of the lithium-containing composite oxide represented by General Formula (1) when 1≧z>0.75 or when 0.25>z>0;
a charge and discharge reaction progresses in a state where the positive electrode active material has two phases of the lithium-containing composite oxides represented by the following General Formulae (2) and (3) when 0.75>z>0.25:
Li a Fe 1-x M x P 1-y Si y O 4   (2)

(wherein 0.75≦a≦1.00, 0.05<x<1, and 0.05<y<l); and
Li b Fe 1-x M x P 1-y Si y O 4   (3)

(wherein 0≦b≦0.25, 0.05<x<1, b+x<1, and 0.05<y<l), and
when the product of the lengths of the b and c axes of the unit cell of the lithium-containing composite oxide of General Formula (2) is designated as bc1 and the product of the lengths of the b and c axes of the unit cell of the lithium-containing composite oxide of General Formula (3) as bc2, α, which is defined by equation α=(bc2)/(bc1), is 0.99<α<1.01 in a state where the positive electrode active material has two phases.

2. The positive electrode active material for nonaqueous-electrolyte secondary batteries according to claim 1 , wherein the valency of M is tetravalent.

3. The positive electrode active material for nonaqueous-electrolyte secondary batteries according to claim 1 , wherein M is Zr.

4. The positive electrode active material for nonaqueous-electrolyte secondary batteries according to claim 1 , wherein at least part of the surface of the positive electrode active material is covered with carbon.

5. A nonaqueous-electrolyte secondary battery positive electrode, comprising the positive electrode active material for nonaqueous-electrolyte secondary batteries according to claim 1 , a conductor, and a binder.

6. A nonaqueous-electrolyte secondary battery, comprising a positive electrode containing the positive electrode active material for nonaqueous-electrolyte secondary batteries according to claim 1 , a negative electrode, an electrolyte, and a separator.

Assignees

• Nishijima Motoaki
• Ohira Koji
• Sueki Toshitsugu
• Esaki Shougo
• Tanaka Isao
• Koyama Yukinori
• Tanaka Katsuhisa
• Fujita Koji
• Murai Shunsuke
• Sharp Kk

Inventors

• Nishijima Motoaki
• Ohira Koji
• Sueki Toshitsugu
• Esaki Shougo
• Tanaka Isao
• Koyama Yukinori
• Tanaka Katsuhisa
• Fujita Koji
• Murai Shunsuke

Classifications

• C01B33/20

  Silicates (persilicates C01B15/14 {; containing aluminium C01B33/26}) · CPC title

• H01M4/625

  Carbon or graphite · CPC title

• H01M4/364

  as mixtures · CPC title

• H01M4/5825

  Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines · CPC title

• H01M4/131

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