# US 8,771,877 B2 · Positive electrode material for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery including the same, and method for producing the same

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- Number: US 8,771,877 B2
- Document ID: US8771877B2
- Status: Granted
- Kind: B2
- Application number: 12/448,629
- Filed: 2007-12-28
- Published: 2009-12-03
- Granted: 2014-07-08
- Earliest claimed: 2006-12-28
- Assignees: GS Yuasa International Ltd.
- Applicants: Yoshinobu Yasunaga; Akihiro Fujii; Tokuo Inamasu
- Inventors: Yoshinobu Yasunaga; Akihiro Fujii; Tokuo Inamasu
- Web page: https://patentgrep.com/patent/US8771877B2

## CPC

- H01M 4/5825: {Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines}
- C01B 32/05: Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
- H01M 4/02: Electrodes composed of, or comprising, active material
- H01M 4/136: Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
- H01M 4/366: {as layered products}
- H01M 4/625: {Carbon or graphite}
- C01P 2004/84: one phase coated with the other
- H01M 4/1397: of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
- H01M 4/587: for inserting or intercalating light metals
- H01M 2004/021: {Physical characteristics, e.g. porosity, surface area}
- Y02E 60/10: Energy storage using batteries
- Y10T 29/49115: including coating or impregnating
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Disclosed is a positive electrode material for nonaqueous electrolyte secondary batteries, which comprises a porous body composed of a material containing a polyanion. Also disclosed is a method for producing such a positive electrode material for nonaqueous electrolyte secondary batteries. When a carbon coating is formed on the surface of a material containing a polyanion of lithium iron phosphate or the like by a conventional method, the capacity during low rate discharge is improved but the capacity is not sufficient. In the present invention, the positive electrode material for nonaqueous electrolyte secondary batteries, which comprises a porous body composed of a material containing a polyanion, has a structure wherein the inner walls of the pores of the porous body are provided with a layered carbon, for improving the discharge capacity.

## Claims

### Claim 1

A positive electrode material for a nonaqueous electrolyte secondary battery comprising a porous body of a polyanion-containing material, wherein said porous body is a secondary particle formed by aggregation of primary particles, in which the primary particles are in direct contact with each other, and wherein inner walls of pores of said porous body are provided with carbon in layer state that forms continuous three-dimensional meshes, and wherein at least a part of the primary particles is not coated with carbon in a starting condition of the primary particles prior to aggregation into the secondary particle.

### Claim 2 (depends on 1)

The positive electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein said polyanion-containing material is lithium iron phosphate.

### Claim 3 (depends on 1)

A nonaqueous electrolyte secondary battery comprising the positive electrode material for a nonaqueous electrolyte secondary battery according to claim 1.

### Claim 4 (depends on 1)

The positive electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein said carbon is provided in layer state on the inner walls of the pores of the porous body such that the carbon layer is intensively distributed in the inner walls of the pores, but not distributed in the entirety of the pores.

### Claim 5 (depends on 1)

The positive electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein said continuous three-dimensional meshes, formed by the carbon layer on the inner walls of the pores of said porous body, electrically connect parts of said porous body such that there is no contact resistance in the carbon layer.

### Claim 6

A method for producing a positive electrode material for a nonaqueous electrolyte secondary battery comprising a porous body of a polyanion-containing material and carbon, wherein the method comprises: forming said porous body as a secondary particle by aggregation of primary particles of the polyanion-containing material, in which the primary particles are in direct contact with each other; and supplying said carbon to the polyanion-containing material in a gaseous source containing at least one of methanol, ethanol, propanol, and butanol in evaporated form, and heating the gaseous source to at least as high as an ignition point of a carbon source in the gaseous source in a manner such that inner walls of pores of said porous body are provided with said carbon in layer state that forms continuous three-dimensional meshes, wherein at least a part of the primary particles is not coated with carbon in a starting condition of the primary particles prior to aggregation into the secondary particle.

### Claim 7 (depends on 6)

The method for producing a positive electrode material for a nonaqueous electrolyte secondary battery according to claim 6, wherein said polyanion-containing material is synthesized by a hydrothermal method.

### Claim 8 (depends on 6)

The method for producing a positive electrode material for a nonaqueous electrolyte secondary battery according to claim 6, wherein said polyanion-containing material is synthesized by a spray drying granulation method.

### Claim 9 (depends on 6)

The method for producing a positive electrode material for a nonaqueous electrolyte secondary battery according to claim 6, wherein said polyanion-containing material is lithium iron phosphate, and the pores of said porous body are provided with the carbon in layer state by heating the gaseous source to at least as high as an ignition point of said at least one of methanol, ethanol, propanol, and butanol contained therein and at most 750° C.

### Claim 10 (depends on 6)

The method for producing a positive electrode material for a nonaqueous electrolyte secondary battery according to claim 6, wherein said carbon is provided in layer state on the inner walls of the pores of the porous body such that the carbon layer is intensively distributed in the inner walls of the pores, but not distributed in the entirety of the pores.

### Claim 11 (depends on 6)

The method for producing a positive electrode material for a nonaqueous electrolyte secondary battery according to claim 6, wherein said continuous three-dimensional meshes, formed by the carbon layer on the inner walls of the pores of said porous body, electrically connect parts of said porous body such that there is no contact resistance in the carbon layer.

### Claim 12

A method for producing a positive electrode material for a nonaqueous electrolyte secondary battery comprising a porous body of a polyanion-containing material and carbon, wherein the method comprises the steps of: forming said porous body as a secondary particle by aggregation of primary particles of the polyanion-containing material, in which the primary particles are in direct contact with each other; placing the secondary particle in a firing furnace; and supplying said carbon to the polyanion-containing material in a gaseous source containing at least one of methanol, ethanol, propanol, butanol, and ethylene glycol in evaporated form while heating the firing furnace to a high temperature such that inner walls of pores of said porous body are provided with said carbon in layer state that forms continuous three-dimensional meshes, wherein at least a part of the primary particles is not coated with carbon in a starting condition of the primary particles prior to aggregation into the secondary particle.