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Method of producing an electrode for a lithium secondary battery, and method of producing a lithium secondary battery

a secondary battery and lithium-ion battery technology, applied in the direction of cell components, final product manufacturing, sustainable manufacturing/processing, etc., can solve the problems of large quantity of lithium ions dissolving in water, low sensitivity and precision, and inability to eliminate water-soluble impurities such as lisub>2/sub>cosub>3 /sub>cannot be eliminated, etc., to achieve high sensitivity and precision, and analyze accurately

Inactive Publication Date: 2012-04-05
YU DENIS YAU WAI +5
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0014]An object of the present invention is to provide a method of producing an active material for a lithium secondary battery which solves the above-mentioned problems and enhances an energy density thereof, a method of producing an electrode for a lithium secondary battery using the method of producing the active material for a lithium secondary battery, and a lithium secondary battery produced by using the method of producing the electrode for a lithium secondary battery.
[0016]According to the above-mentioned method, it is possible to remove just only impurities, which are raw materials or by-products, such as Li3PO4, Li2CO3, or the bivalent Fe compounds such as FeSO4, FeO, or Fe3(PO4)2, other than LiFePO4, without dissolving Fe of LiFePO4, by using a pH buffer solution as a cleaning solution, after synthesizing LiFePO4, for example. Therefore, an active material for a lithium secondary battery, in which an energy density is enhanced, can be obtained. Further, it is possible to suppress voltage depression resulting from dissolving a Fe compound contained as an impurity in a positive electrode in a battery and moving the Fe compound to a negative electrode, and to suppress reduction in charge-discharge efficiency and voltage depression due to the deposition of Li. Furthermore, by suppressing the deposition of Li, charge retention characteristics can be improved. Further, impurities exhibiting alkalinity can be removed so that a reaction between the impurities and a binder of PVdF can be suppressed, thereby to improve a slurry property and to make the preparation of an electrode easier and obtain sufficient electrode strength.
[0035]By employing the methods of the second through the fifth inventions of the present application, the amounts of impurities can be quantified / analyzed with high sensitivity and high precision. Therefore, a substance causing the reduction in the capacity can be assessed up to a low concentration and can be analyzed accurately. When using these, it is possible to monitor variations in the amounts of impurities from production lot to production lot and provide a high-quality active material for a lithium secondary battery.
[0036]In accordance with the first invention of the present application, by cleaning an active material for a lithium secondary battery, including a lithium transition metal oxyanion compound, with the pH buffer solution, the impurities in the active material can be removed efficiently.
[0037]In accordance with the second through the fifth inventions of the present application, by quantifying the amounts of impurities with high sensitivity and high precision, variations in the amounts of impurities can be monitored from production lot to production lot and a high-quality active material for a lithium secondary battery can be provided.

Problems solved by technology

However, the cleaning with water proposed in Japanese Patent Laid-Open No. 2003-17054 has a problem that a large quantity of lithium ions dissolves in water from an active material.
Further, the cleaning with distilled water proposed in International Publication WO 2005 / 051840A1 pamphlet has a problem that water-insoluble impurities such as Li3PO4 and Li2CO3 cannot be eliminated even by cleaning.
Further, methods of quantifying the amounts of impurities proposed in International Publication WO 2005 / 051840A1 pamphlet and Japanese Patent Laid-Open No. 2002-117847 are low in sensitivity and precision, and a problem that the amounts of impurities contained in LiFePO4 vary from production lot to production lot is not resolved well.

Method used

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  • Method of producing an electrode for a lithium secondary battery, and method of producing a lithium secondary battery
  • Method of producing an electrode for a lithium secondary battery, and method of producing a lithium secondary battery
  • Method of producing an electrode for a lithium secondary battery, and method of producing a lithium secondary battery

Examples

Experimental program
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embodiment

Example 1

Preparation of Cleaning Solution

[0044]A pH standard solution of a phthalic salt (pH 4.01) produced by KISHIDA CHEMICAL Co., Ltd. was used as a cleaning solution. The cleaning solution at this time was at pH 4.0.

[0045]100 mg of a LiFePO4 sample (sample A) including Li3PO4 was weighed out and 10 ml of the cleaning solution was added to this sample, and the resulting mixture was cleaned for 1 hour by ultrasonic treatment in an ultrasonic pretreating apparatus.

[0046]The cleaning solution after the above cleaning was filtrated with a filter in order to remove the sample not dissolved by cleaning, and an amount of P dissolved in the cleaning solution was quantified by Inductively Coupled high frequency Plasma emission spectroscopic analysis (ICP emission spectroscopic analysis).

[0047]The amount of P dissolved was calculated by the following equation.

Amount of P dissolved (% by weight)=(amount of P dissolved in a cleaning solution (mg)×100) / amount of sample (mg)

[0048]In order to i...

example 2

[0049]Acetic acid and sodium acetate were mixed in a ratio of 1:1 by weight and pure water was added to the resulting mixture to prepare a 1.0% by weight aqueous solution of this mixture, and this aqueous solution was used as a cleaning solution. The cleaning solution at this time was at pH 4.5. A sample was cleaned, the amount of P dissolved in the cleaning solution was quantified, and a pH value of the cleaning solution was measured by the same procedure as in Example 1 except for using this cleaning solution.

example 3

[0050]Acetic acid and sodium acetate were mixed in a ratio of 1:10 by weight and pure water was added to the resulting mixture to prepare a 1.0% by weight aqueous solution of this mixture, and this aqueous solution was used as a cleaning solution. The cleaning solution at this time was at pH 5.6. A sample was cleaned, the amount of P dissolved in the cleaning solution was quantified, and a pH value of the cleaning solution was measured by the same procedure as in Example 1 except for using this cleaning solution.

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Abstract

A method of producing an active material for a lithium secondary battery, by which impurities causing problems in synthesizing an active material for a lithium secondary battery, including a lithium transition metal oxyanion compound are removed efficiently and enhancement of an energy density is realized, is provided. By cleaning the active material for a lithium secondary battery, including a lithium transition metal oxyanion compound, with a pH buffer solution, for example, it is possible to efficiently remove just only impurities such as Li3PO4 or Li2CO3, or a substance, other than LiFePO4, in which the valence of Fe is bivalent such as FeSO4, FeO or Fe3(PO4)2 without dissolving Fe of LiFePO4.

Description

[0001]This application is a division of application Ser. No. 12 / 071,880, filed Feb. 27, 2008, which claims priority based on Japanese Patent Application Nos. 2007-050586, 2007-136050, 2007-177742 and 2008-008288 filed Feb. 28, 2007, May 22, 2007, Jul. 5, 2007 and Jan. 17, 2008, respectively, and which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a method of producing an active material used for a lithium secondary battery, a method of producing an electrode for a lithium secondary battery, a method of producing a lithium secondary battery, and a method of monitoring a quality of an active material for a lithium secondary battery, and is particularly characterized in that, by cleaning an active material including a lithium transition metal oxyanion compound with a pH buffer solution, the amounts of impurities in the active material is reduced, and higher quality and enhancement of an energy densi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M10/04C01D15/00H01M4/04H01M4/58H01M10/0525H01M10/36
CPCC01B25/45H01M4/04Y10T29/49108H01M10/0525Y02E60/122H01M4/5825Y02E60/10Y02P70/50
Inventor YU, DENIS YAU WAIDONOUE, KAZUNORIYOSHIDA, TOSHIKAZUKADOHATA, TETSUOMURATA, TETSUYUKIMATSUTA, SHIGEKI
Owner YU DENIS YAU WAI
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