Lithium transition metal composite oxide for use as positive active material of lithium secondary battery and method for producing the same

• US 20020110518A1
• Filed: 12/06/2001
• Published: 08/15/2002
• Est. Priority Date: 12/08/2000
• Status: Abandoned Application

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Okuda, Chikaaki, Takechi, Naoko, Ukyo, Yoshio
• Application Number:
  US10/003,279
• Publication Number:
  US 20020110518A1
• Time in Patent Office: Days
• US Class Current: 423/594.4
• CPC Class Codes: C01G 51/42 containing alkali metals, e.g. LiCoO2
• CPC Class Codes: C01G 51/44 containing manganese
• CPC Class Codes: C01G 53/42 containing alkali metals, e.g. LiNiO2
• CPC Class Codes: C01G 53/44 containing manganese
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2002/54 one element only
• CPC Class Codes: C01P 2002/85 by XPS, EDX or EDAX data
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: H01M 2004/021 Physical characteristics, e.g. porosity, surface area
• CPC Class Codes: H01M 2004/028 Positive electrodes
• CPC Class Codes: H01M 4/0471 involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• CPC Class Codes: H01M 4/1391 of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/362 Composites
• CPC Class Codes: H01M 4/505 of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A lithium transition metal composite oxide for use as a positive active material capable of composing a lithium secondary battery of which the internal resistance does not increase greatly even after stored in a charged state for a long period of time, and a method for readily producing such a lithium transition metal composite oxide. The lithium transition metal composite oxide is composed of a transition metal containing at least one selected from the group consisting of Co, Ni and Mn as a main composition element. The composition of a surface layer of each particle of the lithium transition metal composite oxide is made different from that of an inside of each particle. In one example, the ratio of lithium in the composition of the surface layer of each particle is made greater than that in the average composition of each particle. With the method for producing the lithium transition metal composite oxide, specific raw materials are mixed and fired in two stages.

Claims

1. A lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, comprising:

a transition metal as a main composition element, which is composed of at least one selected from the group consisting of Co, Ni and Mn, the ratio of lithium in a composition of a surface layer of each particle of said lithium transition metal composite oxide being greater than the ratio of lithium in an average composition of said each particle.

2. A lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, as claimed in claim 1, wherein said ratio of lithium in said composition of said surface layer of each particle of said lithium transition metal composite oxide is 1.2 or more times said ratio of lithium in said average composition of said each particle.

3. A lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, comprising:

a transition metal as a main composition element, which is composed of at least one selected from the group consisting of Co, Ni and Mn, at least one substitution element selected from the group consisting of Al and Fe being substituted for one part of said transition metal, and said lithium transition metal composite oxide satisfying at least one of conditions;

(1) the ratio of lithium in a composition of a surface layer of each particle of said lithium transition metal composite oxide is greater than the ratio of lithium in an average composition of said each particle; and

(2) the ratio of said substitution element in said composition of said surface layer of said each particle of said lithium transition metal composite oxide is less than the ratio of said substitution element in said average composition of said each particle.

4. A lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, as claimed in claim 3, wherein said ratio of lithium in said composition of said surface layer of said each particle of said lithium transition metal composite oxide is 1.2 or more times the ratio of lithium in said average composition of said each particle.

5. A lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, as claimed in claim 3, wherein said ratio of said substitution element in said composition of said surface layer of said each particle of said lithium transition metal composite oxide is 0.8 or less times the ratio of said substitution element in said average composition of said each particle.

6. A method for producing a lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, which includes a transition metal as a main composition element, said transition metal being composed of at least one selected from the group consisting of Co, Ni and Mn, and the ratio of lithium in a composition of a surface layer of each particle of said lithium transition metal composite oxide being greater than the ratio of lithium in an average composition of said each particle, comprising:

a first mixing step of mixing a lithium compound as a lithium source with a compound composed of at least one selected from the group consisting of Co, Ni and Mn as a transition metal source to obtain a first mixture;

a first firing step of firing said first mixture in an oxygen atmosphere to obtain a first lithium transition metal composite oxide;

a second mixing step of mixing said first lithium transition metal composite oxide with a lithium compound as a lithium source to obtain a second mixture; and

a second firing step of firing said second mixture in an oxygen atmosphere to obtain a second lithium transition metal composite oxide.

7. A method for producing a lithium transition metal composite oxide for use as a positive active material of a lithium secondary battery, which includes a transition metal as a main composition element, said transition metal being composed of at least one selected from the group consisting of Co, Ni and Mn, and at least one substitution element selected from the group consisting of Al and Fe being substituted for one part of said transition metal, and said lithium transition metal composite oxide satisfying at least one of conditions (1) the ratio of lithium in a composition of a surface layer of each particle of said lithium transition metal composite oxide is greater than the ratio of lithium in an average composition of said each particle, and (2) the ratio of said substitution element in said composition of said surface layer of said each particle of said lithium transition metal composite oxide is less than the ratio of said substitution element in said average composition of said each particle, comprising:

a first mixing step of mixing a lithium compound as a lithium source with a compound composed of at least one selected from the group consisting of Co, Ni and Mn as a transition metal source and a compound composed of at least one selected from the group consisting of Al and Fe as a substitution element source to obtain a first mixture;

a first firing step of firing said first mixture in an oxygen atmosphere to obtain a first lithium transition metal composite oxide;

a second mixing step of mixing said first lithium transition metal composite oxide with a lithium compound as a lithium source and a compound composed of at least one selected from the group consisting of Co, Ni and Mn as a transition metal source, as required, to obtain a second mixture; and

a second firing step of firing said second mixture in an oxygen atmosphere to obtain a second lithium transition metal composite oxide.