JP2003017011A - Alkaline batteries - Google Patents

Abstract

(57) [Summary] The present invention has been made in view of the above circumstances of an alkaline dry battery, and an object of the present invention is to provide an alkaline dry battery having excellent long-term storage characteristics in an alkaline dry battery suitable for heavy load discharge. I do. SOLUTION: The present invention provides an alkaline dry battery comprising a metal positive electrode can, a positive electrode mixture accommodated in the positive electrode can, and a gelled zinc negative electrode material arranged to face the positive electrode mixture with a separator interposed therebetween. An alkaline battery characterized in that a conductive material layer containing a carbon-based material powder as a main component and a cobalt-based material powder is formed on an inner surface of the positive electrode can.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline dry battery, and more particularly to an alkaline dry battery having improved heavy load characteristics and storage stability.

[0002]

2. Description of the Related Art In recent years, heavy-load portable electric devices requiring a high current capacity such as digital cameras, AV players such as CD players, MD players, liquid crystal televisions, etc. have been widely used. Also, improvement of heavy load discharge characteristics, long life characteristics, etc. has been demanded in response to these applications.

A battery using a nickel hydroxide-based material as a positive electrode active material has been developed as an alkaline dry battery having excellent heavy load discharge characteristics (UK Patent 365).
125). This battery has (1) a high battery voltage of 1.73 V, (2) a flat discharge curve,
(3) It is known as a battery having excellent aspects such as high utilization rate of active material in heavy load discharge. Further, an inside-out type nickel-zinc secondary battery using nickel hydroxide as a positive electrode active material and zinc as a negative electrode active material is also known (Japanese Patent Laid-Open No. 2000-67910).

However, in these batteries,
Since the positive electrode active material has a strong oxidizing power, it oxidizes the inner surface of the positive electrode can material that is in contact with this positive electrode active material, forming the oxide of the positive electrode can material on the inner surface of the positive electrode can, and causing electrical conduction. There is a problem that the internal resistance of the battery is increased and the discharge characteristics are deteriorated due to the formation of an oxide film having poor properties. In the case of an alkaline battery using this nickel hydroxide-based substance as a positive electrode acting substance, there is a disadvantage in that long-term storage stability is poor.

That is, a conventional alkaline dry battery is shown in FIG. In FIG. 2, reference numeral 1 denotes a bottomed cylindrical metal can that also functions as a positive electrode terminal and is made of stainless steel, nickel-plated iron, or the like. A positive electrode mixture 2 containing a substance is housed in contact with the inner surface of the metal can 1. Inside the hollow of the positive electrode mixture 2, there is a bottomed cylindrical separator 3 made of non-woven fabric of vinylon and polyvinyl alcohol fiber.
The gelled zinc negative electrode material 4 is filled in via. Then, a negative electrode current collector rod 5 made of a brass metal rod is inserted into the negative electrode material 4, and one end of the negative electrode current collector rod 5 projects from the surface of the negative electrode material 4 and also serves as a ring-shaped metal plate 7 and a cathode terminal. It is electrically connected to the metal sealing plate 8. An insulating gasket 6 made of a double annular polyamide resin is arranged on the inner surface of the metal can 1 serving as the positive electrode and the outer peripheral surface of the protruding portion of the negative electrode current collector rod 5, and these are insulated. The opening of the metal can 1 is crimped and liquid-tightly sealed.

In the alkaline dry battery using the nickel hydroxide-based material, since the nickel hydroxide-based material forming the positive electrode active material has a strong oxidizing power, the nickel hydroxide-based material is placed in the metal positive electrode can 1 and is brought into contact therewith. It tends to oxidize the inner wall surface of the positive electrode can. Oxidation of the positive electrode can by the nickel hydroxide-based material causes reduction of the nickel hydroxide-based material, resulting in reduction in capacity or capacity deterioration of the alkaline dry battery.

Further, iron oxide generated on the inner wall surface of the positive electrode case due to oxidation, or a trivalent iron compound such as iron hydroxide acts as a film having low conductivity, which adversely affects large current (heavy load) discharge. The inconvenience of exerting it can be seen.
In other words, it is expected to be a high-performance, long-life power supply for digital still cameras and the like, but in reality, the high-performance and long-life power supply has not yet been fully achieved.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances of an alkaline dry battery, and an object thereof is to provide an alkaline dry battery suitable for heavy load discharge, which is excellent in long-term storage characteristics. To do.

[0009]

The present invention comprises a positive electrode can made of metal, a positive electrode mixture contained in the positive electrode can, and a gelled zinc negative electrode material facing the positive electrode mixture through a separator. In the alkaline dry battery described above, a conductive material layer containing carbon-based material powder as a main component and cobalt-based material powder contained therein is formed on the inner surface of the positive electrode can.

In the alkaline battery, the cobalt-based material contained in the conductive material layer includes metallic cobalt, cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide,
Further, it is desirable that it is at least one selected from the group consisting of cobalt hydroxide.

In the alkaline battery, graphite is desirable as the carbon-based substance, and the compounding ratio of the graphite powder and the cobalt-based substance is 1 to 10 parts by mass with respect to 100 parts by mass of the graphite powder. desirable.

Furthermore, in the alkaline battery, it is desirable to use a nickel hydroxide-based material as the positive electrode active material. The nickel hydroxide-based substance may be nickel hydroxide, nickel oxyhydroxide, or a substance obtained by doping these substances with other metal atoms, or a cobalt-based substance particle having conductivity on the particle surface of these substances. A coated product or the like can be used.

As described above, the alkaline dry battery of the present invention comprises, as a main component, a carbonaceous substance powder such as graphite on the inner surface of the positive electrode can, and by forming a conductive material layer containing the cobalt substance powder, The positive electrode active material prevents the reaction of oxidizing the inner surface of the positive electrode can, and suppresses an increase in the internal resistance of the battery to realize a dry battery with improved storage stability.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a sectional view of the alkaline dry battery of the present invention. In FIG. 1, the same components as those in FIG. 2 described above are designated by the same reference numerals, and description thereof will be omitted. That is, the present invention is characterized in that, in FIG. 1, the conductive material layer 10 is formed on the inner surface of the positive electrode can 1, particularly on the portion in contact with the positive electrode mixture. The present invention will be described below with reference to FIG.

(Positive Electrode Can) The positive electrode can 1 made of metal is made of, for example, stainless steel or an iron base material whose surface is plated with nickel, and its form and shape are cylindrical, rectangular tube, and button. It is shaped into a shape. The conductive material layer of the present invention is formed on at least the surface of the positive electrode cans that is in contact with the positive electrode. This conductive material layer is for imparting anticorrosion property to the metal constituting the positive electrode can, and is mainly composed of carbonaceous substance powder such as graphite and coated with a conductive paint containing cobalt type substance powder. It is composed of the formed conductive material layer.

(Conductive coating material) In the present invention, to form this conductive material layer, a carbon-based material powder such as graphite and a cobalt-based material powder are mixed and dispersed with a solvent and a binder, and kneaded into a paint form. -It is formed by preparing, coating and drying this on the inner surface of the positive electrode can. In the present invention, as the conductive material, graphite powder and cobalt-based material powder are used as the conductive material. The mixing ratio of these components is 1 to 10 of the cobalt-based material powder to 100 parts by weight of the graphite powder. A range of parts by mass is preferred. Even if the ratio of the cobalt-based substance powder exceeds the above range, no further effect can be expected, which causes a cost increase. On the other hand, when the blending ratio of the cobalt-based substance is less than the above range, the effect of blending the cobalt-based substance powder is reduced, the internal resistance of the battery after long-term storage is increased, and the heavy load discharge characteristic is deteriorated.

In the present invention, as the binder used in the conductive paint, the binder used in general paints can be used. Examples of this binder include polyvinyl chloride resin and polyvinyl butyl alcohol resin. Moreover, as the solvent, an organic solvent used in general paints can be used. Examples of this solvent include methyl ethyl ketone and cyclohexane. In the conductive coating material of the present invention, the mixing ratio of the conductive material and the binder is 100
The binder is used in the range of 20 to 100 parts by mass with respect to parts by mass. When the ratio of the conductive material is higher than this, the ratio of the binder component decreases, the strength of the conductive coating decreases, and peeling easily occurs. On the other hand, when the ratio of the conductive material is lower than the above range, the internal resistance increases and the heavy load discharge characteristics deteriorate. The ratio of solid content to solvent in the conductive paint is
Although it can be arbitrarily selected within a range that allows uniform coating, the solid content ratio is usually 10 to 50% by mass.

This conductive paint can be applied to the inner surface of the positive electrode can by using a spray gun and dried to form a coating film. Alternatively, a predetermined amount of the conductive paint is poured into the positive electrode can and the positive electrode can is tilted while the inner surface is tilted. It is also possible to form a conductive paint layer on and dry it to form a coating film. In the present invention, the film thickness of the conductive coating film depends on the mechanical strength of the film thickness.
A range of 20 μm is sufficient.

In the present invention, the carbonaceous substance may be a carbonaceous substance such as graphite, acetylene black or Ketjenblack which is used as a conductive material for dry batteries. Of these, graphite is conductive. , Most desirable in terms of stability.

In the present invention, the cobalt-based material powder used by being mixed with the graphite powder includes metallic cobalt, cobalt hydroxide (Co (OH) ₂ ), and cobalt monoxide (C).
oO), dicobalt trioxide (Co ₂ O ₃ ), and the like, and these are further subjected to an oxidation treatment to form cobalt oxyhydroxide (CoOOH), tricobalt tetroxide (C).
Powders such as those converted to highly conductive high order cobalt oxides such as o ₃ O ₄ ) can also be used.

(Positive Electrode Mixture) In the present invention, the positive electrode mixture is prepared by mixing and molding a positive electrode active material and a conductive material.
As the conductive material of the present invention, carbon particles such as graphite and acetylene black can be used. The blending amount is
The range of 3 to 10 parts by mass of carbon particles is suitable for 100 parts by mass of the positive electrode active material. If the blending ratio of carbon particles is higher than this, the amount of active material is relatively reduced, which makes it unsuitable for high capacity, while if the blending ratio of carbon particles is lower than this, the electron conductivity is relatively lowered, and therefore, it is high. It is no longer suitable for output characteristics.

As the positive electrode active material, any positive electrode active material suitable for heavy load discharge can be used, but it is particularly preferable to use a nickel hydroxide-based material. The positive electrode active material used in the present invention is mainly composed of nickel hydroxide or nickel oxyhydroxide particles. Further, nickel oxyhydroxide in which zinc or cobalt alone or both are eutectic is preferable because the structural change thereof can be reduced even in a low electrolytic solution ratio. The amount of zinc or cobalt to be eutectic with nickel oxyhydroxide is preferably in the range of 1 to 7%. This is because if the amount of zinc is less than this range, the shape of the battery changes due to swelling of the positive electrode depending on the conditions, and if it exceeds this range, the nickel purity is relatively lowered and it becomes unsuitable for high capacity.

In order to secure electronic conductivity between nickel oxyhydroxide particles, a composite oxyhydroxide obtained by depositing a highly conductive high-order cobalt compound on the surface of nickel hydroxide is provided. preferable. Examples of the cobalt compound deposited on the surface include cobalt hydroxide (Co (OH) ₂ ) and cobalt monoxide (C) as starting materials.
oO), dicobalt trioxide (Co ₂ O ₃ ), etc., and high conductivity such as cobalt oxyhydroxide (CoOOH) and tricobalt tetroxide (Co ₃ O ₄ ) can be obtained by oxidizing this. It is preferable to use the one converted into a higher cobalt oxide.

The above-mentioned positive electrode active material of the present invention can be produced, for example, by the following method. Cobalt hydroxide is added to nickel hydroxide particles doped with zinc and cobalt, and an aqueous sodium hydroxide solution is sprayed while stirring in an air atmosphere. Subsequent microwave heating produces composite nickel hydroxide particles in which a layer of cobalt higher oxide is formed on the surface of nickel hydroxide. Further, an oxidizing agent such as sodium hypochlorite may be added to this reaction system to proceed with oxidation to produce a composite nickel oxyhydroxide coated with a cobalt higher oxide. As a result, a positive electrode active material having extremely excellent conductivity can be obtained.

The cobalt particles or cobalt compound particles used in this case have a specific surface area of 2.5 to ³⁰ m ³ / g.
It is preferable to use cobalt hydroxide. By adopting cobalt particles or cobalt compound particles having a particle size within this range, the contact area between nickel hydroxide and cobalt hydroxide is secured, which leads to an improvement in the utilization rate of the positive electrode. The production of such a positive electrode mixture is described in JP-A-10-233229 and JP-A-10-275620.
JP-A-10-188969, etc., and the method for producing such a positive electrode mixture can be adopted in the present invention.

(Negative electrode mixture) As the negative electrode active substance which can be used in the present invention, zinc powder is preferable in view of energy density, cost, and large current output (discharge).
Furthermore, for example, indium (In), bismuth (B
A zinc alloy powder containing i), aluminum (Al) and the like in an amount of 0.02 to 0.5 mass% is desirable. That is, the alloying of zinc suppresses the rate of self-dissolution in the alkaline electrolyte and suppresses the generation of hydrogen gas inside the battery of the closed system, so that accidents such as liquid leakage can be prevented.

(Separator) In the present invention, examples of the separator include non-woven fabric made of vinylon, polyvinyl alcohol fiber, rayon, mercerized pulp and the like. It has been experimentally confirmed that when a separator made of these materials is selected, it is stable against the oxidizing power of the nickel hydroxide-based substance and retains the separator function for a long period of time. That is, since deterioration due to oxidation does not occur, occurrence of a short circuit inside the battery is eliminated or avoided, and long-term storage stability can be secured.

(Electrolytic Solution) As the alkaline electrolytic solution, an aqueous solution of potassium hydroxide (KOH), sodium hydroxide (N
aOH) aqueous solution, but from the viewpoint of conductivity and stability of the nickel hydroxide-based material, a 34 to 48 mass% potassium hydroxide aqueous solution is preferable. When a zinc alloy is used as the negative electrode acting substance, in order to reduce the generation of hydrogen gas due to self-discharging (dissolution) of zinc, a zinc compound such as zinc oxide is previously dissolved in an alkaline electrolyte to form zinc ions. Is desirable to exist. When the zinc compound is added to the alkaline electrolyte in a saturated state, the dissolution reaction of the negative electrode metal zinc during the discharge reaction is adversely affected. Therefore, the amount added to the alkaline electrolyte is about 2 to 6% by mass. Is preferred.

[0029]

EXAMPLES Examples will be described below with reference to FIG.

[Example 1] (Treatment of positive electrode can) JIS standard LR obtained by drawing a nickel-plated steel plate having a nickel-plated iron substrate surface
A cylindrical positive electrode case for a type 6 (AA) battery is prepared.
Then, the conductive material film of the present invention is formed on the inner wall surface of the positive electrode can. That is, 100 parts by mass of graphite powder and 5 parts by mass of cobalt oxyhydroxide powder are mixed, 60 parts by mass of polyvinyl chloride is further added as a binder, 200 parts by mass of methyl ethyl ketone as a solvent is added thereto, and mixed by a ball mixer for 2 hours. And then used it as paint. The coating material thus produced was sprayed and applied with a spray gun, then the solvent was evaporated and dried to form a conductive material layer on the inner wall surface of the positive electrode can so as to have a film thickness of 10 μm.

(Preparation of Positive Electrode Mixture) 92 parts by mass of nickel oxyhydroxide powder coated with high-order cobalt, which is a positive-electrode acting substance, on the surface, a conductive agent, and moldability and mold releasability from a mold. Artificial graphite powder (trade name SP-1
0, manufactured by Nippon Graphite Industry Co., Ltd.) and mixed with 8 parts by mass. After that, a hollow cylindrical positive electrode mixture was pressure-molded using a positive electrode mixture forming die corresponding to JIS standard LR6 type battery.

(Preparation of negative electrode) 0.05% by mass of indium, 0.01% by mass of bismuth and 0.0 of aluminum
An undenatured zinc alloy powder containing 03 mass%, a 40 mass% potassium hydroxide aqueous solution (electrolyte solution) having a zinc oxide concentration of 5 mass%, and sodium polyacrylate as a gelling agent,
A gelled zinc negative electrode was prepared by stirring and mixing under reduced pressure.

(Preparation of Separator) A non-woven fabric having a thickness of 110 μm and made of vinylon and polyvinyl alcohol fiber is wound in three layers, and a part thereof is heat-bonded to form a cylindrical body. Further, a disc is punched out from a polyethylene resin sheet having a thickness of 150 μm, and the disc is heated and adhered to one end of the cylindrical body to form a bottomed cylindrical separator.

(Assembly of Alkaline Battery) The above-prepared cylindrical positive electrode mixture, gelled zinc negative electrode, and separator were prepared in a conventional positive electrode case which also serves as a positive electrode terminal for JIS standard LR6 type battery in a conventional manner. By the means, they were attached and arranged to assemble an AA alkaline battery. FIG. 1 is a sectional view showing a schematic configuration of an assembled AA alkaline battery.

In FIG. 1, 1 is a bottomed cylindrical positive electrode can that also serves as a positive electrode terminal, 9 is a conductive material coating for covering the inner wall surface of the positive electrode can 1, and 2 is a conductive material coating 9 in the positive electrode can 1. Cylindrical positive electrode mixture (positive electrode) 3 mounted / disposed as is a bottomed cylindrical separator mounted / disposed inside the positive electrode mixture 2. The positive electrode mixture 2 has a structure in which three positive electrode mixtures, which are divided into slices, are laminated.

Further, 4 is a gelled zinc negative electrode filled in the hollow portion of the cylindrical positive electrode mixture 2 through a bottomed cylindrical separator 3, and 5 is one end in the gelled zinc negative electrode 4. It is a negative electrode current collector rod made of brass that is inserted and arranged such that the other end is projected.

Further, 6 is an insulating gasket which allows the other end of the negative electrode current collecting rod 5 to be inserted and electrically insulates from the positive electrode can 1, and which contributes to liquid-tight sealing, and 7 is an annular gasket. And 8 is a cap-shaped metal sealing plate whose inner wall surface is electrically connected to the other end of the negative electrode current collector rod 5 and which also functions as a negative electrode terminal. Here, the insulating gasket 6 is
For example, the positive electrode can 1 is made of polyamide resin, and the positive electrode can 1 is liquid-tightly sealed with the metal plate 7 and the metal sealing plate 8 by caulking the positive electrode can 1.

Comparative Examples 1 and 2 (Battery Assembly of Comparative Example) In Example 1 described above, the conductive material layer formed on the inner surface of the positive electrode can was made of a conductive material made of only graphite without using a cobalt-based material. An alkaline dry battery was manufactured in the same manner as in Example 1 except that a positive electrode can having a conductive layer was used (Comparative Example 1). In addition, in Example 1 except that the positive electrode can as obtained by drawing a nickel-plated steel plate having a nickel-plated surface of an iron substrate without forming a conductive layer on the inner surface of the positive electrode can was used. An alkaline dry battery was manufactured in the same manner as in Example 1 (Comparative Example 1).

[Evaluation] Next, with respect to the alkaline dry batteries of Example 1 and Comparative Examples 1 and 2, the discharge duration up to a closed circuit voltage of 0.9 V by continuous discharge of 2 A (average value of 20 surveyed samples, before starting storage) ), A digital still camera (Alegret PDR-M60, kk, Toshiba) mounted test shots (number of shots once every 30 seconds, average of 5 shots), undischarged (unused) battery at 40 ° C. at 40 ° C. Table 1 shows the results obtained by testing and evaluating the discharge duration time until the closed circuit voltage was 0.9 V and the number of images of the mounting test shooting after continuous storage at 2 A after storage for one day.

[0040]

[Table 1]

As can be seen from Table 1, 2 A continuous discharge,
The number of images taken in the mounting test by the digital still camera is better in the first embodiment. Example 1 using a cobalt-based material as compared to Comparative Example using a conductive material made of only graphite
It is considered that this is because the conductivity is improved, and in the case of Comparative Example 2, the positive electrode can has already reacted with the nickel hydroxide-based substance and the capacity has deteriorated.

On the other hand, the difference between Example 1 and Comparative Examples 1 and 2 is remarkable in the 2 A, large current (heavy load) discharge after storage, and the reason is considered as follows. That is, in the alkaline battery according to the comparative example, reduction of the nickel hydroxide-based material by the positive electrode can occurs, and the iron trivalent compound coating film grows. This can be said to be resistance, and especially under a large current, the IR drop becomes larger and the operating voltage decreases. On the other hand, in the case of the alkaline batteries according to the examples, since the positive electrode can is prevented from being oxidized and deteriorated and good conductivity is secured, it functions as an alkaline dry battery that retains high performance even during long-term storage.

In the above, the case of the AA alkaline battery is shown, but the same action and effect are recognized even in the case of, for example, the AA type, the C2 type, or the button type alkaline battery. It was also confirmed that when nickel oxyhydroxide and nickel oxyhydroxide coated with a cobalt compound were used as the positive-electrode active substance, the same function as a stable and high-performance alkaline dry battery was obtained.

The present invention is not limited to the above embodiments, but various modifications can be made without departing from the spirit of the invention. For example, the composition ratio and composition of the positive electrode mixture, the composition of the negative electrode, and the like can be appropriately selected according to the intended use or intended performance.

[0045]

According to the present invention, due to the strong oxidizing power of the positive electrode active material, the positive electrode can maintains and exhibits the required function without oxidative deterioration, but does not cause the reduction deterioration of the nickel hydroxide-based material. The decrease in battery capacity is also suppressed. In other words, there is no fear that the capacity of the positive electrode will decrease or the capacity of the battery will decrease due to oxidative deterioration of the positive electrode can, and while utilizing the features of the positive electrode active material, we will provide highly reliable alkaline dry batteries that exhibit excellent long-term use and storage stability. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an AA alkaline battery according to an embodiment.

FIG. 2 is a cross-sectional view showing a schematic configuration of a conventional AA alkaline battery.

[Explanation of symbols]

1 ... Positive electrode case 2 ... Positive electrode mixture 3 ... Resin-based separator 4 ... Gel zinc negative electrode 5 ... Negative electrode current collector 6 ... Insulation gasket 7: Ring metal plate 8: Metal sealing plate 9 ... Conductive material layer

Continued front page    F-term (reference) 5H011 AA02 AA04 BB03 CC06 DD09                       DD18                 5H017 AA02 AS06 DD05 EE01 EE06                       HH01                 5H024 AA14 CC02 DD02 DD14 DD15                       EE03 EE06 HH01                 5H050 AA07 AA08 AA09 BA04 CA03                       CA08 CB13 DA10 EA02 HA01

Claims (4)

[Claims] 1. An alkaline battery comprising a positive electrode can made of metal, a positive electrode mixture housed in the positive electrode can, and a gelled zinc negative electrode material facing the positive electrode mixture with a separator interposed therebetween. An alkaline dry battery characterized in that a conductive material layer containing carbonaceous substance powder as a main component and containing cobaltaceous substance powder is formed on the inner surface of the. 2. In the alkaline dry battery, the cobalt-based material contained in the conductive material layer is at least selected from the group consisting of metallic cobalt, cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, and cobalt hydroxide. The alkaline dry battery according to claim 1, wherein the alkaline dry battery is one type. 3. The alkaline dry battery according to claim 1, wherein the mixing ratio of the carbon-based material and the cobalt-based material is 1 to 10 parts by mass of the cobalt-based material with respect to 100 parts by mass of the carbon-based material. Alternatively, the alkaline dry battery according to claim 2. 4. The alkaline dry battery according to any one of claims 1 to 3, wherein the positive electrode active material in the alkaline dry battery is a nickel hydroxide-based material.