JP2008103134A - Air battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air battery having high output and high capacity by homogenizing a catalyst layer without deteriorating easiness of manufacturing the catalyst layer. <P>SOLUTION: This air battery includes: a positive electrode case which has an air hole on its bottom face and is opened at its one end; a positive electrode assembly comprising a diffusion paper, a water repellent film, and a gas diffusion electrode which is formed in a body by bonding a separator to a positive electrode catalyst layer composed of mangnese oxide, binder, a conductive material and activated carbon press-bonded and molded by using a positive electrode collector as a base member, where the diffusion paper, the water repellent film and the gas diffusion electrode are laminated in this on the bottom face of the positive electrode case; a gel-like negative electrode active material disposed so as to face and make contact with the separator of the positive electrode assembly while containing an electrolyte and zinc powder; a negative electrode case brought into electrical contact with the negative electrode active material; and an insulating gasket interposed and inserted in the space to be sealed between the negative electrode case and the positive electrode case. The air battery having high output and high capacity can be materialized by using polytetrafluoroethylene to which acrylic modification is applied as the binder of the positive electrode catalyst layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air battery, and more particularly to an air battery with high output and long life.

  Air batteries that use zinc as the negative electrode and oxygen in the air as the positive electrode do not need to pack the positive electrode active substance in the battery, so if the battery is the same size, pack more zinc as the negative electrode active substance. Is possible. Therefore, the air battery has an advantage that a large capacity can be obtained as compared with the alkaline manganese battery and the silver oxide battery, and the demand is increasing.

  Air batteries are mainly used in devices such as hearing aids, but in recent years, digitalization of devices such as hearing aids has progressed, and higher output of batteries has been desired. There is a growing need for capacity. Therefore, various efforts have been made such as reducing the internal resistance of the battery in order to achieve higher output and higher capacity of the air battery.

  For example, as shown in Patent Document 1, a conductive material such as graphite is mixed with a catalyst material that is an active material of the positive electrode catalyst layer, thereby reducing contact resistance between powders of the positive electrode catalyst layer and reducing internal resistance of the battery. In order to achieve higher output and higher capacity by increasing the discharge operating voltage, a device has been devised. However, the method disclosed in Patent Document 1 also has the following problems.

That is, by mixing a conductive material with the catalyst material that is the active material of the positive electrode catalyst layer, the resistance of the positive electrode catalyst layer itself is reduced and the heavy load discharge characteristics are improved. However, if too much conductive material is added, the internal resistance can be greatly reduced, but the catalyst layer cannot be molded, and the catalyst layer density is reduced, which makes it difficult to mold the catalyst layer. Since voids are formed between the electrolyte layers, the catalyst layer suffocates due to accumulation of the electrolyte in the catalyst layer. As a result, there are problems such as shortening of life and deterioration of storage characteristics.
JP-A-10-189006

  The present invention has been made in view of the above circumstances, and its purpose is to increase the dispersibility of the binder used in the catalyst layer and promote the fibrillation efficiency, thereby reducing the productivity of the catalyst layer. Is to provide a high-power and high-capacity air battery.

  In order to solve the above-described problems, the present invention provides a positive electrode case having one end with an air hole on the bottom surface, a diffusion paper, a water repellent film, and a positive electrode current collector that are sequentially stacked on the bottom surface of the positive electrode case. From a gas diffusion electrode in which a positive electrode catalyst layer composed of activated carbon, manganese oxide, binder, and conductive material, bonded to a separator, and a separator are bonded to each other, and a water repellent layer is bonded to the opposite surface. A positive electrode assembly, a gelled negative electrode active material containing an electrolyte and zinc powder disposed in contact with a separator of the positive electrode assembly, a negative electrode case in electrical contact with the negative electrode active material, and the negative electrode An air battery having an insulating gasket inserted between a sealed portion of a case and a positive electrode case, wherein polytetrafluoroethylene subjected to acrylic modification is used as a binder for the positive electrode catalyst layer. The features.

  According to the present invention, the dispersibility of the binder and the fibrillation efficiency are promoted, so that the catalyst layer is homogenized without deteriorating the productivity of the catalyst layer, and a high output and high capacity air battery is provided. be able to.

Hereinafter, the best mode of the present invention will be described in detail with reference to specific examples.
(Example 1)
FIG. 1 shows a PR44 type air battery according to this example. In FIG. 1, 1 is a positive electrode case, 2 is an air hole provided in the bottom surface of the positive electrode case 1, 3 is a diffusion paper, 4 is a water repellent film, 5 is a positive electrode current collector, 6 is a positive electrode catalyst layer, and 7 is a separator. , 8 is a water-repellent layer pressure-bonded to the catalyst layer 6, 9 is a positive electrode assembly, 10 is a negative electrode active material, 11 is a negative electrode case, 12 is an insulating gasket, and 13 is an air hole provided in the positive electrode case. It is a sealing tape for stopping.

  The positive electrode case 2 is made of nickel or nickel plated on iron or stainless steel. The diffusion paper 3 is made of kraft paper having a thickness of 50 to 100 μm, and the water repellent film 4 is made of a polytetrafluoroethylene (PTFE) film. The positive electrode catalyst layer 6 is composed of activated carbon, manganese oxide, expanded graphite as a conductive material, and a binder, and the catalyst layer constituent materials are heated and mixed at 130 ° C. and formed into a sheet shape with a heat roller. Is.

  Moreover, polytetrafluoroethylene powder (Mittabrene A-3000 manufactured by Mitsubishi Rayon Co., Ltd.) subjected to acrylic modification was used as a binder, and the amount of the binder was 25% in terms of the weight ratio of the catalyst constituent material. The separator 7 is a laminate of a polypropylene microporous membrane and a nonwoven fabric.

  The negative electrode active material 10 is a gel containing zinc powder and an electrolytic solution. This gel-like negative electrode active material 10 is a gel-like mixture prepared by blending polyacrylic acid (gelling agent) and zinc alloy powder in an electrolyte of 30 to 45% by weight potassium hydroxide aqueous solution. is there. The zinc alloy powder has a particle size of about 100 to 300 μm and is hatched or non-hatched with the addition of aluminum, bismuth, indium, lead or the like.

  Further, the negative electrode case 11 is made of, for example, a three-layer clad of nickel, stainless steel and copper, and the insulating gasket 12 is of a polyamide resin type.

(Examples 2 to 4)
A PR44 air battery having the same configuration as in Example 1 was prepared except that tetrafluoroethylene powder subjected to acrylic modification was used as the binder of the catalyst layer, and the blending ratios were set to 20%, 15%, and 10%, respectively.

(Comparative Examples 1 to 4)
A PR44 air battery having the same configuration as in Example 1 except that tetrafluoroethylene powder not subjected to acrylic modification was used as the binder of the catalyst layer, and the blending ratios were set to 25%, 20%, 15%, and 10%, respectively. Created.

(Comparative Examples 5 and 6)
A PR44 air battery having the same configuration as in Example 1 was prepared, except that tetrafluoroethylene powder obtained by subjecting the binder to acrylic modification to the catalyst layer was used and the blending ratio was set to 30% and 5%, respectively.

  Based on the configurations described in the above examples and comparative examples, 50 JIS standard PR44 type air cells were assembled, and the moldability of the catalyst layers was compared. Moreover, 15 mA heavy load discharge was implemented about the air battery of the said structure, the discharge result was expressed with the discharge capacity (0.9V cut) of the comparative example 1 as 100, and the operating voltage during discharge was measured.

Table 1 compares and displays each evaluation result.

  Comparing Examples 1 to 4 with Comparative Examples 1 to 6, it can be seen that Examples 1 to 4 have good results in the moldability of the catalyst layer and the discharge test. This is because tetrafluoroethylene with acrylic modification is used for the binder of the catalyst layer, and the binder is efficiently fibrillated and the dispersibility is improved, thereby improving the water repellency of the air electrode and penetrating the electrolyte. This is because the durability of the catalyst layer is increased.

  Moreover, in Example 4 and Comparative Example 4, even if the binder compounding ratio is the same, Example 4 has good moldability of the catalyst layer, but Comparative Example 4 has poor moldability of the catalyst layer and cannot form the catalyst layer. In Example 4, since the binder was efficiently fibrillated and dispersibility was improved by using tetrafluoroethylene subjected to acrylic modification as the binder of the catalyst layer, the catalyst layer could be molded even with a small amount of binder. It has become possible.

  Further, in Examples 1 to 4 and Comparative Examples 5 and 6, even when tetrafluoroethylene subjected to acrylic modification is used for the binder of the catalyst layer, if the binder blending ratio is too high as in Comparative Example 5, the catalyst layer Since the water repellency becomes too high, the operating voltage is lowered and the discharge capacity is lowered. In addition, when the blending ratio of the binder is too low as in Comparative Example 6, the catalyst layer can be molded efficiently and the moldability of the catalyst layer is deteriorated even if the dispersibility is good. This is considered to be because the amount of the binder for forming the catalyst layer is extremely too small. Therefore, when tetrafluoroethylene subjected to acrylic modification is used for the binder of the catalyst layer, the blending ratio is desirably 10% to 25%.

  In addition, this invention is not limited to the said Example, A various form can be taken in the range which does not deviate from the meaning of invention. For example, a cylindrical air battery other than a button-type air battery or a square air battery can be applied.

  As described above, according to the present invention, it is possible to provide a high-power and long-life air battery without reducing the productivity of the catalyst layer.

Sectional drawing which shows the principal part structural example of an air battery.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 2 ... Air hole, 3 ... Diffusion paper, 4 ... Water-repellent film, 5 ... Positive electrode collector, 6 ... Positive electrode catalyst layer, 7 ... Separator, 8 ... Water-repellent layer, 9 ... Positive electrode assembly, DESCRIPTION OF SYMBOLS 10 ... Negative electrode active material, 11 ... Negative electrode case, 12 ... Insulating gasket, 13 ... Seal tape.

Claims (2)

  One end of the positive electrode case with an air hole at the bottom, activated carbon formed by pressure bonding with diffusion paper, water-repellent film, and positive electrode current collector stacked sequentially on the bottom of the positive electrode case, manganese oxide A positive electrode assembly composed of a gas diffusion electrode in which a separator is adhered to a positive electrode catalyst layer composed of a material, a binder, and a conductive material, and a water-repellent layer is pressure-bonded to the opposite surface, and the separator of the positive electrode assembly Gelled negative electrode active material containing electrolyte solution and zinc powder arranged in contact with each other, a negative electrode case in electrical contact with the negative electrode active material, and interposed between sealed portions of the negative electrode case and the positive electrode case An air battery having an insulating gasket, wherein polytetrafluoroethylene subjected to acrylic modification is used as a binder for the positive electrode catalyst layer.   2. The air battery according to claim 1, wherein a binder compounding ratio of the positive electrode catalyst layer is 10% to 25%.

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