# US 2013/0157134 A1 · Method of producing iron phosphate, lithium iron phosphate, electrode active substance, and secondary battery

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- Number: US 2013/0157134 A1
- Document ID: US20130157134A1
- Status: Published application
- Kind: A1
- Application number: 13/767,938
- Filed: 2013-02-15
- Published: 2013-06-20
- Earliest claimed: 2010-08-18
- Assignees: Murata Manufacturing Co., Ltd.
- Inventors: Yuji Kintaka
- Web page: https://patentgrep.com/patent/US20130157134A1

## CPC

- H01M 4/136: Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
- C01B 25/37: Phosphates of heavy metals
- C01B 25/45: containing plural metal, or metal and ammonium
- H01M 4/1397: of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
- H01M 4/5825: {Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines}
- H01M 10/052: Li-accumulators
- Y02E 60/10: Energy storage using batteries
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- 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}
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A mixed aqueous solution is prepared in which a phosphorus source, a divalent Fe compound, and an oxidant are mixed at a predetermined ratio. Then, this mixed aqueous solution is dropwise added into a buffer solution having a pH value of 1.5 to 9, thereby to produce a precipitated powder of FePO4. This FePO4 is synthesized with a lithium compound to obtain LiFePO4. An electrode active substance containing this LiFePO4 as a major component is used as a positive electrode material of a secondary battery.

## Claims

### Claim 1

A method of producing iron phosphate, the method comprising bringing a mixed aqueous solution, in which a phosphorus source and an iron compound containing trivalent iron are dissolved, into contact with a buffer solution having a pH value of 1.5 to 9 to produce an iron phosphate powder.

### Claim 2 (depends on 1)

The method according to claim 1, further comprising synthesizing the iron phosphate powder with a lithium compound to produce lithium iron phosphate.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the synthesizing further comprises:
mixing the iron phosphate powder and the lithium compound in a molar ratio of 1:1 to obtain a mixed powder; and
heat treating the mixed powder in a reducing atmosphere to produce the lithium iron phosphate.

### Claim 4 (depends on 2)

The method according to claim 2, further comprising forming an electrode active substance with the lithium iron phosphate.

### Claim 5 (depends on 1)

The method according to claim 1, further comprising preparing the mixed aqueous solution.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the mixed aqueous solution is prepared by mixing a divalent Fe compound, the phosphorus source, and an oxidant.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the divalent Fe compound and the phosphorous source are mixed in approximately equal molar ratio amounts, and the oxidant is in a greater molar ratio amount.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the mixed aqueous solution is added to the buffer solution.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the addition of the mixed aqueous solution to the buffer solution is ended before the pH reaches 1.5.

### Claim 10 (depends on 1)

Lithium iron phosphate obtained by synthesizing the iron phosphate produced by the production method according to claim 1 and a lithium compound.

### Claim 11 (depends on 2)

An electrode active substance, wherein lithium iron phosphate according to claim 2 is contained therein as a major component.

### Claim 12 (depends on 11)

A secondary battery having a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is formed of the electrode active substance according to claim 11.