JP2010073347A - Positive electrode mixture for dry battery, method of manufacturing the same, and dry battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode mixture for a dry battery with high electrolyte impregnating properties, high effective utilization rate of an active substance molded in high density, and excellent in discharge characteristics. <P>SOLUTION: A positive electrode material containing a positive electrode active material made of manganese dioxide and a conductive agent made of graphite is compression-molded into a given shape (a hollow cylindrical shape) to form a positive electrode mixture 2, a molded body surface of which 2 is imparted with hydrophilicity by surface modification by means of plasma discharge, UV irradiation or corona discharge. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positive electrode mixture for dry batteries, and more particularly, to a positive electrode mixture for dry batteries having a high impregnation property of an electrolyte, a method for producing the same, and a dry battery using the same.

  The positive electrode mixture of an alkaline battery is usually formed by mixing a positive electrode active material such as manganese dioxide and a conductive agent such as graphite with a binder or the like, and compression-molding the mixture into a predetermined shape.

  In recent years, there has been a demand for improvement in discharge performance of alkaline batteries. For this reason, in order to accommodate as much of the positive electrode active material as possible by effectively using the limited internal volume of the battery case, The density of the compression molded body is increased.

  However, when the density of the molded body is increased, the void volume inside the molded body is reduced, the amount of the liquid electrolyte impregnated is reduced, and the time required for the liquid absorption is also increased. As a result, the electrolytic solution in the battery case becomes deficient, which causes a problem that the effective utilization rate of the active material molded at a high density is lowered and the discharge performance of the battery is lowered.

  Therefore, in order to increase the effective utilization rate of the active material and improve the discharge performance of the battery, a recess is provided on the surface of the positive electrode mixture pellet formed by compression molding, and the electrolytic solution is formed in the space formed in this recess. Japanese Patent Application Laid-Open No. H10-228707 describes a technique for storing the above.

  However, when the density of the positive electrode material mixture pellets is increased, the depression provided on the surface of the positive electrode material mixture pellets is brittle.

Patent Document 2 describes a technique for increasing both the positive electrode active material and the impregnating electrolyte. That is, by forming the positive electrode mixture into a molded body composed of a mixture grain having a high density and a high strength and a mixture grain having a lower strength than the mixture grain, When the electrolyte is impregnated, the space between the low-strength mixture particles swells to form microcracks, and the electrolyte is held in these microcracks. Thereby, the density of the molded body can be increased by the high-strength mixture particles, and the electrolyte solution impregnation property of the molded body can be improved by the low-strength mixture particles.
JP 2000-036301A JP 2002-0753338

  However, since the technique described in Patent Document 2 is based on the premise that the electrolyte solution is impregnated between the low-strength mixture particles, it takes a long time to absorb the electrolyte solution. There is a possibility that the amount of liquid absorption impregnation of the liquid may be reduced. On the other hand, since high-strength mixture particles are used, it is difficult to compress the molded body at high density, and before the molded body is compression-molded, a process for producing high-strength mixture particles Therefore, there is a problem that productivity is reduced.

  The present invention has been made in view of such points, and provides a positive electrode mixture for a dry battery having high electrolyte solution impregnation property, high effective utilization of an active material formed at high density, and excellent discharge characteristics. For the purpose.

  The positive electrode mixture for a dry battery according to the present invention is a positive electrode mixture formed by compression molding a positive electrode material containing a positive electrode active material and a conductive agent into a predetermined shape, and the surface of the molded body of the positive electrode mixture is subjected to surface modification. It is characterized by imparting hydrophilicity.

  With such a configuration, since the surface of the molded body of the positive electrode mixture can easily absorb the electrolytic solution, the electrolyte impregnation property of the positive electrode mixture can be improved. In addition, since the surface of the molded body may be modified after the positive electrode mixture is compression-molded at a high density, a battery having excellent discharge characteristics can be obtained without hindering densification of the molded body.

  Here, the positive electrode active material is preferably made of manganese dioxide, and the conductive agent is preferably made of graphite. The surface modification is preferably performed by plasma discharge, UV irradiation, or corona discharge on the surface of the molded body of the positive electrode mixture. Thereby, hydrophilicity can be provided to the surface of the molded body of the positive electrode mixture by a simple treatment, and a positive electrode mixture having high electrolyte solution impregnation property can be easily obtained.

  The surface of the molded body of the positive electrode mixture is preferably further roughened by plasma discharge, UV irradiation, or corona discharge. Thereby, since the surface of the molded body of the positive electrode mixture becomes easier to absorb the electrolytic solution, the electrolyte solution impregnation property of the positive electrode mixture can be further improved.

  The positive electrode mixture is preferably compression-molded into a hollow cylinder, and the inner wall surface of the positive electrode mixture is preferably given hydrophilicity by plasma discharge, UV irradiation, or corona discharge. Thereby, since the electrolyte solution poured into the hollow part of the molded body of the positive electrode mixture is easily absorbed from the inner wall surface of the molded body, the electrolyte solution impregnation property of the positive electrode mixture can be further improved.

  The method for producing a positive electrode mixture for a dry battery according to the present invention includes a step of mixing a positive electrode active material made of manganese dioxide and a conductive agent made of graphite, and compression-molding the mixture to form a positive electrode mixture having a predetermined shape. And a step of imparting hydrophilicity to the surface of the positive electrode mixture formed in a predetermined shape by plasma discharge, UV irradiation, or corona discharge.

  A dry battery according to the present invention is characterized in that the positive electrode mixture for a dry battery described above is housed in a battery case together with an electrolytic solution.

  According to the present invention, the surface of the positive electrode mixture that has been compression-molded into a predetermined shape is given hydrophilicity by performing surface modification such as plasma discharge, so that the surface of the positive electrode mixture absorbs the electrolytic solution. Therefore, the electrolyte solution impregnation property of the positive electrode mixture can be improved. In addition, since the surface of the molded body may be modified after the positive electrode mixture is compression-molded at a high density, a battery having excellent discharge characteristics can be obtained without hindering densification of the molded body.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of simplicity. In addition, this invention is not limited to the following embodiment.

  FIG. 1 is a half cross-sectional view showing a configuration of an alkaline battery using a positive electrode mixture for alkaline batteries in an embodiment of the present invention.

  As shown in FIG. 1, a hollow cylindrical positive electrode mixture 2 is accommodated in a bottomed cylindrical battery case 1, and a separator 4 formed in a bottomed cylindrical shape is provided in a hollow portion of the positive electrode mixture 2. A gelled negative electrode 3 is accommodated therebetween. The positive electrode mixture 2, the separator 4 and the gelled negative electrode 3 contain an alkaline electrolyte. The opening of the battery case 1 accommodates power generation elements such as the positive electrode mixture 2 and the gelled negative electrode 3, and then is connected to the negative electrode current collector 6 and the negative electrode current collector 6. 7) and the sealing unit 9 in which the gasket 5 is integrated. Further, the outer surface of the battery case 1 is covered with an exterior label 8.

  Here, the positive electrode mixture 2 is obtained by compression molding a mixture containing a positive electrode active material such as manganese dioxide, a conductive agent such as graphite, and a binder or a lubricant with a mold or the like. Then, the surface of the compression molded positive electrode mixture 2 is subjected to surface modification by plasma discharge, UV irradiation, or corona discharge to impart hydrophilicity. Thereby, since the molded object surface of the positive electrode mixture 2 becomes easy to absorb electrolyte solution, the electrolyte solution impregnation property of a positive electrode mixture can be improved. In addition, since the surface of the molded body may be modified after the positive electrode mixture is compression-molded at a high density, a battery having excellent discharge characteristics can be obtained without hindering densification of the molded body.

  The surface modification of the positive electrode mixture 2 can be performed by subjecting the surface of the molded body to plasma discharge, UV irradiation, or corona discharge.

  FIG. 2 is a configuration diagram schematically showing a surface treatment method by plasma discharge as an example of surface modification of the hollow cylindrical positive electrode mixture 2.

  As shown in FIG. 2, the plasma generator 10 generates a plasma by applying a high pressure to the inside of the plasma nozzle 11, and irradiates the positive electrode mixture 2 with the plasma from the injection port of the plasma nozzle 11. The surface of the agent 2 is modified to impart hydrophilicity. Further, when modifying the inner wall surface of the positive electrode mixture 2, the inner wall surface of the positive electrode mixture 2 can be easily modified by irradiating the plasma while rotating the injection nozzle of the plasma nozzle. Thereby, since the electrolyte solution poured into the hollow part of the positive electrode mixture 2 is easily absorbed from the inner wall surface of the positive electrode mixture 2, the electrolyte solution impregnation property of the positive electrode mixture 2 can be further improved.

  In the present invention, the surface of the molded body of the positive electrode mixture 2 is imparted with hydrophilicity to the surface of the molded body by performing plasma discharge, UV irradiation, or corona discharge. It is also possible to roughen the surface of the molded body. Thereby, since the molded object surface of the positive electrode mixture 2 becomes easier to absorb electrolyte solution, the electrolyte solution impregnation property of the positive electrode mixture 2 can further be improved.

  Here, the material for the positive electrode active material is not particularly limited, but materials such as nickel oxyhydroxide can be used in addition to manganese dioxide. As the conductive agent, materials such as graphite powder, carbon black, and carbon fiber can be used.

  As the gelled negative electrode 3, for example, a gelling agent added to an alkaline electrolyte, processed into a gel shape, and zinc alloy powder as a negative electrode active material mixed and dispersed can be used. Moreover, as a gelatinizer, materials, such as a carboxy vinyl polymer and its salts (poly (meth) acrylic acid, its metal salt, etc.), carboxymethyl cellulose, its salts, etc. can be used, for example.

  As the separator 4, for example, a nonwoven fabric mainly composed of polyvinyl alcohol fibers and cellulose fibers subjected to alkali resistance treatment can be used.

  Nylon, polypropylene, or the like is used for the gasket 5, but 6,6-nylon, 6,10-nylon, 6,12-nylon may be used as a material having alkali resistance and heat resistance.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, in the above-described embodiment, the hollow cylindrical positive electrode mixture has been described as an example of the positive electrode mixture molded body. However, for example, a hollow positive electrode mixture may be used. Moreover, in the said embodiment, although the alkaline dry battery was demonstrated to the example as a dry battery, it can apply also to dry batteries, such as a manganese dry battery and a nickel-type primary battery. Moreover, the dry battery using the positive electrode mixture in the present invention is not limited to a cylindrical dry battery but can be applied to a square dry battery.

  The positive electrode mixture for dry batteries of the present invention has a high electrolyte solution impregnation property, and a dry battery using the positive electrode mixture has excellent discharge characteristics and is suitably used as a power source for electronic devices.

1 is a half cross-sectional view showing a configuration of an alkaline battery in an embodiment of the present invention. It is the block diagram which showed the method of the surface treatment by the plasma discharge of the positive mix in the embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Positive electrode mixture 3 Gel-like negative electrode 4 Separator 5 Gasket 6 Negative electrode collector 8 Exterior label 9 Sealing unit 10 Plasma generator 11 Plasma nozzle

Claims (7)

A positive electrode mixture for a dry battery, which is obtained by compression molding a positive electrode material containing a positive electrode active material and a conductive agent into a predetermined shape,
A positive electrode mixture for a dry battery, wherein the surface of the molded body of the positive electrode mixture is provided with hydrophilicity by surface modification.   The positive electrode mixture for a dry battery according to claim 1, wherein the positive electrode active material is made of manganese dioxide, and the conductive agent is made of graphite.   The positive electrode mixture for a dry battery according to claim 1 or 2, wherein the surface modification is performed by plasma discharge, UV irradiation, or corona discharge on the surface of the molded body of the positive electrode mixture.   The positive electrode mixture for dry batteries according to claim 3, wherein the surface of the molded body of the positive electrode mixture is further roughened by the plasma discharge, UV irradiation, or corona discharge.   The positive electrode mixture is compression molded into a hollow cylindrical shape, and hydrophilicity is imparted to the inner wall surface of the positive electrode mixture by the plasma discharge, UV irradiation, or corona discharge. Positive electrode mixture for dry batteries. Mixing a positive electrode active material made of manganese dioxide and a conductive agent made of graphite, and compression-molding the mixture to form a positive electrode mixture of a predetermined shape;
And a step of imparting hydrophilicity to the surface of the positive electrode mixture formed in the predetermined shape by plasma discharge, UV irradiation, or corona discharge.   A dry battery in which the positive electrode mixture for dry batteries according to any one of claims 1 to 5 is housed in a battery case together with an electrolytic solution.

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