JP2002151092A - Alkaline battery - Google Patents

Abstract

(57) [Problem] To provide an alkaline battery having high energy density and excellent long-term storage characteristics. SOLUTION: A positive electrode case 1 also serving as a positive electrode terminal, a positive electrode 3 housed and arranged in the positive electrode case 1 containing a ferric acid (VI) salt as an active substance, and a negative electrode arranged to face the positive electrode 3 5, a separator 4 for separating the negative electrode 5 and the positive electrode 3, an alkaline electrolyte carried on at least the separator 4, and electrically connected to the negative electrode 5 and integrated with the positive electrode case 1 via an insulating gasket 7. An alkaline battery having a negative electrode terminal portion 9
An alkaline battery, wherein at least a surface of the inner wall surface of the positive electrode case 1 in contact with the positive electrode 3 is coated with a graphite layer 2 to impart anticorrosion properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery, and more particularly, to an alkaline battery having a high energy density and excellent long-term storage characteristics using ferric acid (VI) salt as a positive electrode active material.

[0002]

2. Description of the Related Art As is well known, alkaline batteries are widely used as power sources for portable radios, cassettes, and the like. In recent years, with the spread of digital still cameras and the like, batteries that serve as power sources have been further improved in performance,
It is required to have a long life. In response to such a demand, the open circuit voltage of about 1.6
It is more advantageous to use a ferrate exhibiting an open circuit voltage of about 1.8 V instead of manganese dioxide or the like exhibiting V because it is more advantageous for a power supply for equipment exhibiting constant power consumption behavior.
I) An alkaline battery using a salt as a positive electrode active substance has been proposed.

For example, a positive electrode mixture containing a ferric acid (VI) salt formed into a hollow cylindrical shape is housed and mounted in a bottomed cylindrical metal positive electrode case also serving as a positive electrode terminal. The cylindrical portion is filled with a gelled negative electrode via a bottomed cylindrical separator, a negative electrode current collector is inserted into the filled negative electrode, and the opening of the positive electrode case is made of a metal which also serves as a negative electrode terminal via an insulating gasket. There is known an alkaline battery having a configuration in which a sealing plate (a negative electrode terminal portion) is sealed in a liquid-tight manner.

Here, the metal positive electrode case is made of, for example, stainless steel, nickel-plated iron, or the like, and the positive electrode mixture is made of ferric acid (VI) salt, which is a positive electrode active substance.
For example, it is made of a composition containing K ₂ FeO ₄ , BaFeO ₄ , and the like, and a conductive agent. The bottomed cylindrical separator is, for example, a nonwoven fabric such as a polyamide fiber or a polyolefin fiber, and the gelled negative electrode is a non-melonized zinc powder, an aqueous solution of potassium hydroxide containing zinc oxide, and sodium polyacrylate ( (Gelling agent). Further, the negative electrode current collector rod is made of, for example, brass.

[0005]

However, in the case of an alkaline battery using a ferric acid (VI) salt as a positive electrode active substance, there is a disadvantage that long-term storage stability is poor. That is, since the ferric acid (VI) salt forming the positive electrode active substance has a strong oxidizing power, it tends to oxidize the inner wall surface of the positive electrode case that is in contact with the metal positive electrode case in a state of being housed and disposed in the metal positive electrode case. Oxidation of the positive electrode case with the ferric acid (VI) salt leads to reduction of the ferric acid (VI) salt.
The capacity or capacity of the alkaline battery will be reduced.

[0006] In addition, a trivalent iron compound such as iron oxide or iron hydroxide formed on the inner wall surface of the positive electrode case by oxidation acts as a film having low conductivity, which adversely affects large current (heavy load) discharge. Inconvenience is seen.
In other words, although it is expected to be a high-performance and long-life power supply corresponding to a digital still camera or the like, in reality, it has not yet reached a high performance and a long life.

The present invention has been made in view of the above circumstances, and has as its object to provide an alkaline battery having a high energy density and excellent long-term storage characteristics.

[0008]

According to the first aspect of the present invention, there is provided a positive electrode case also serving as a positive electrode terminal and a positive electrode case accommodated in the positive electrode case.
A positive electrode containing a ferric acid (VI) salt disposed as an active substance, a negative electrode disposed opposite to the positive electrode, a separator separating the negative electrode and the positive electrode, and an alkaline electrolyte supported on at least the separator; An alkaline battery having a negative electrode terminal portion electrically connected to the negative electrode, and integrally sealing the positive electrode case via an insulating gasket and sealing, wherein at least a surface of the positive electrode case inner wall facing the positive electrode is graphite. An alkaline battery characterized in that the layer is coated with a layer to impart anticorrosion properties.

A second aspect of the present invention is the alkaline battery according to the first aspect, wherein the ferric acid (VI) salt is at least one selected from potassium ferrate and barium ferrate.

A third aspect of the present invention is the alkaline battery according to the first or second aspect, wherein the negative electrode contains a zinc alloy as a negative electrode active material.

According to a fourth aspect of the present invention, in the alkaline battery according to any one of the first to third aspects, the alkaline electrolyte is a potassium hydroxide aqueous solution containing a zinc compound.

In the first to fourth aspects of the present invention, the metal positive electrode case is made of, for example, stainless steel, a surface nickel-plated iron base material, and the like, and its shape and shape are cylindrical, square cylindrical, and the like. , Button shapes, and the like. In the inner wall surface of these positive electrode cases, at least the graphite layer which covers at least the surface in contact with the positive electrode and imparts anticorrosion properties is generally prepared by kneading and preparing a solvent, a binder or an adhesive, and graphite powder in the form of a paint. Then, it is formed by coating and drying. In addition, since this graphite layer has conductivity, it does not impair the current collecting effect as the positive electrode terminal of the positive electrode case.

In the invention of claims 1 to 4, the ferric acid (VI) salt constituting the positive electrode active substance is represented by the general formula: M _x FeO ₄ (where M is an alkali and alkaline earth element, and M is +
X = 2 in case of monovalent, + = indicated by x = 1 in case of bivalent
Hexavalent iron compounds such as potassium ferrate (K ₂ Fe
O ₄ ) and barium ferrate (BaFeO ₄ ). Here, the ferrate is not particularly limited, but the above-mentioned potassium ferrate and barium ferrate are preferable in consideration of energy density and stability. The ferric acid (VI) salt may be used in one kind or in a mixture of two or more kinds. In forming a positive electrode mixture (positive electrode), a conductive agent is added in order to impart required conductivity. Combined.

In the first to third aspects of the present invention, the negative electrode active material is preferably zinc powder in consideration of energy density, cost, and large current output (discharge).
For example, a zinc alloy powder containing about 0.02 to 0.5% by mass of indium (In), bismuth (Bi), aluminum (Al) or the like 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 sealed battery, so that accidents such as liquid leakage can be prevented.

Here, as other component elements that are alloyed with zinc, the discharge characteristics, the ability to suppress the generation of hydrogen gas due to self-dissolution of zinc inside the battery when not in use, and after use has been interrupted, are taken into consideration comprehensively. Other than the above-mentioned exemplified elements, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, titanium, vanadium, iron, copper, zirconium, niobium, silver, gallium, tin and the like can be mentioned. In the case of a zinc alloy containing bismuth, bismuth segregates on the surface of the zinc alloy, reducing the self-dissolution of zinc when not in use and during long-term storage, and in the case of a zinc alloy containing aluminum, Reduce self-dissolution after discontinuation of use.

In the first to fourth aspects of the present invention, examples of the alkaline electrolyte include an aqueous solution of potassium hydroxide (KOH) and an aqueous solution of sodium hydroxide (NaOH).
From the viewpoints of conductivity and stability of ferric acid (VI) salt, 34 to
A 48% by mass aqueous solution of potassium hydroxide is preferred. Also,
When a zinc alloy is used as the negative electrode active material, a zinc compound such as zinc oxide is previously dissolved in an alkaline electrolyte to reduce the generation of hydrogen gas due to self-discharge (dissolution) of zinc, and zinc ions are present. It is desirable to keep it. In addition, when the zinc compound is added to the alkaline electrolyte in a saturated state, on the contrary, the dissolution reaction of the negative electrode metal zinc during the discharge reaction is hindered.
About 2 to 6% by mass is preferable.

In the inventions according to claims 1 to 4, the separator is (a) a woven or nonwoven fabric or a porous film made of polyamide resin fibers such as 6,6-nylon, and (b) a polyethylene resin. Woven cloth or sheet made of polyolefin resin-based fiber such as polypropylene resin or the like by melt blow method, or porous film, or (c) a cloth woven cloth made of glass fiber and having a thickness of about 200 to 500 μm. No. If you select a separator made of these materials,
It was experimentally confirmed that the compound was stable against the oxidizing power of ferric acid (VI) salt and maintained 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 and the like can be ensured.

According to the first to fourth aspects of the present invention, the oxidation reaction of the positive electrode case due to the strong oxidizing power of the ferric acid (VI) salt constituting the positive electrode active substance is prevented, and the formation of a film of the oxidation reaction product or the ferric acid (VI) A reduction in capacity or deterioration in capacity of the battery due to reduction of salt is avoided. That is, the possibility of deterioration or damage due to oxidation of the positive electrode case is eliminated, and the ferric acid (VI) salt does not undergo reductive deterioration, so that the battery capacity does not decrease and
It is possible to make an alkaline battery exhibiting excellent long-term use and storage stability while utilizing the features of ferric acid (VI) salt.

[0019]

An embodiment will be described below with reference to FIG.

Embodiment

Processing of the positive electrode case

A cylindrical positive electrode case for a JIS standard LR6 type (AA) battery obtained by drawing a metal plate having a nickel-plated iron base surface is prepared. Next, a paint containing about 20% by mass of graphite powder dispersed therein is sprayed and applied by a spray gun on the inner wall surface of the positive electrode case, and then the solvent is evaporated and dried to form a graphite-based layer on the inner wall surface of the positive electrode case. I do.

Preparation of positive electrode mixture (positive electrode)

Powder 8 of potassium ferrate as a positive electrode active substance
8 parts by mass and 12 parts by mass of an artificial graphite powder (trade name: SP-10, manufactured by Nippon Graphite Industries KK) which is a conductive agent and imparts moldability and mold release property to a mold were mixed and stirred. Thereafter, a positive electrode mixture having a hollow cylindrical shape was pressure-formed using a positive electrode mixture molding die corresponding to JIS standard LR6 type battery.

Preparation of negative electrode

Indium 0.05 mass%, bismuth 0.
A non-melonized zinc alloy powder containing 0.01% by mass and 0.003% by mass of aluminum, a 40% by mass aqueous solution of potassium hydroxide (electrolyte) having a zinc oxide concentration of 5% by mass, and sodium polyacrylate as a gelling agent Was stirred and mixed under reduced pressure to prepare a gelled zinc negative electrode.

Preparation of separator

Thickness 110 made of polyethylene resin fiber
A nonwoven fabric having a thickness of μm is wound three times, and a part of the nonwoven fabric is heated and adhered to form a cylindrical body. Further, a circular plate is punched out from a polyethylene resin sheet having a thickness of 150 μm, and the circular plate 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 are mounted and arranged by a conventional means in a positive electrode case also serving as a positive electrode terminal corresponding to JIS standard type LR6 type battery. Thus, an AA alkaline battery was assembled. FIG. 1 is a cross-sectional view showing a schematic configuration of an assembled AA alkaline battery.

In FIG. 1, 1 is a bottomed cylindrical positive electrode case also serving as a positive electrode terminal, 2 is a graphite-based layer covering the inner wall surface of the positive electrode case 1, and 3 is a graphite-based layer 2 in the positive electrode case 1.
A cylindrical positive electrode mixture (positive electrode) mounted and arranged via
Reference numeral 4 denotes a bottomed cylindrical separator mounted and arranged inside the positive electrode mixture 3. In addition, the positive electrode mixture 3 has a configuration in which three positive electrode mixtures divided in a ring shape are laminated.

Reference numeral 5 denotes a gelled zinc negative electrode in which the hollow portion of the cylindrical positive electrode mixture 3 is filled via a bottomed cylindrical separator 4, and reference numeral 6 denotes one end of the gelled zinc negative electrode 5. This is a brass-made negative electrode current collector rod that is inserted and arranged with the other end protruding.

Further, reference numeral 7 denotes an insulating gasket that allows the other end of the negative electrode current collector rod 6 to pass therethrough and electrically insulates the positive electrode case 1 from the other, and contributes to liquid-tight sealing.
Is a ring-shaped metal plate, and 9 is a hat-shaped metal sealing plate also serving as a negative electrode terminal whose inner wall surface is electrically connected to the other end of the negative electrode current collecting rod 6. Here, the insulating gasket 7
Is made of a polyamide resin, for example, and the positive electrode case 1 is liquid-sealed by a metal plate 8 and a metal sealing plate 9 by caulking the positive electrode case 1.

Battery assembly of comparative example

In the configuration of the alkaline battery shown in FIG. 1, a positive electrode case 1 having an inner wall surface treated with a graphite paint.
Instead of using a positive electrode case that was obtained by drawing a nickel-plated metal plate on the surface of an iron base material without the inner wall surface treatment with graphite paint, Battery was created.

Next, regarding the alkaline batteries of the above Examples and Comparative Examples, the discharge duration up to a closed circuit voltage of 0.9 V (average value of 20 surveyed items, before the start of storage) with a continuous discharge of 2 A, a digital still camera (Allegretto) PDR-M
1, kk. Mounting test by Toshiba) Number of shots (1 shot per 30 seconds, average of 5 shots), 2A continuous after storing undischarged (unused) batteries at 60 ° C for 20 days and 60 ° C for 40 days Table 1 shows the results of tests and evaluations of the discharge duration up to a closed circuit voltage of 0.9 V by discharging.

[0037]

[Table 1]

As can be seen from Table 1, 2A continuous discharge,
The embodiment is superior in both the number of shots taken during the mounting test by the digital still camera. In other words, the comparative example is inferior, and in the case of the comparative example, it is considered that the positive electrode case has already reacted with ferrate to cause the capacity deterioration.

On the other hand, in the 2A, high current (heavy load) discharge after storage, the difference between the embodiment and the comparative example is remarkable, and the reason is considered as follows. That is, in the alkaline battery according to the comparative example, reduction of ferrate due to the positive electrode case occurs, and a trivalent compound film of iron grows. In particular, under high current, the IR drop becomes larger,
It can be said that the operating voltage decreases. On the other hand, in the case of the alkaline battery according to the embodiment, since the positive electrode case is prevented from being oxidized and deteriorated, good conductivity is also ensured, so that the alkaline battery functions as an alkaline battery that maintains high performance even during long-term storage.

In the above description, the case of AA alkaline batteries has been shown. However, similar effects can be obtained in the case of, for example, AA or AA batteries, or button alkaline batteries. In addition, barium ferrate as a positive electrode active substance,
Alternatively, in the case of a potassium ferrate-barium ferrate mixed system,
Similarly, it was confirmed that it functions as a stable and high-performance alkaline battery.

The present invention is not limited to the above embodiment, and 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 purpose of use or the intended performance.

[0042]

According to the first to fourth aspects of the present invention, ferric acid (V
I) Due to the strong oxidizing power of the salt, the positive electrode case maintains and exhibits a required function without being oxidized and degraded, but does not cause reduction degradation of ferrate, so that a decrease in battery capacity is also suppressed. In other words, there is no danger of a decrease in the positive electrode capacity or a decrease in the battery capacity due to the oxidative deterioration of the positive electrode case.
A highly reliable alkaline battery exhibiting excellent long-term use and storage stability while utilizing the features of salt can be provided.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Positive electrode case 2 ... Graphite layer 3 ... Positive electrode mixture 4 ... Resin-based separator 5 ... Gelled zinc negative electrode 6 ... Negative electrode current collector rod 7 ... Insulating gasket 8 ... Ring metal plate 9 ... Metal Sealing plate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 4/64 H01M 4/64 B 6/06 6/06 B (72) Inventor Keisuke Narumi Shinagawa-ku, Tokyo 3-4-10 Minamishinagawa Toshiba Battery Corporation F-term (reference) 5H011 AA02 CC05 DD09 DD17 5H017 AA02 AS06 AS10 BB08 CC01 DD05 EE06 5H024 AA02 AA14 CC02 CC14 DD02 DD15 FF09 5H050 AA07 AA08 AA09 BA04 CA02 CB13 DA04 FA

Claims (4)

[Claims] 1. A positive electrode case also serving as a positive electrode terminal, a positive electrode containing a ferric acid (VI) salt housed and disposed in the positive electrode case as an active substance, a negative electrode disposed opposite to the positive electrode, A separator for separating the negative electrode and the positive electrode,
At least an alkaline electrolyte supported on the separator,
An alkaline battery having a negative electrode terminal portion electrically connected to the negative electrode, and integrally sealing the positive electrode case via an insulating gasket, and sealing at least a surface of the positive electrode case inner wall surface with which the positive electrode is in contact. An alkaline battery characterized in that the layer is coated with a layer to impart anticorrosion properties. 2. The alkaline battery according to claim 1, wherein the ferric acid (VI) salt is at least one selected from potassium ferrate and barium ferrate. 3. The alkaline battery according to claim 1, wherein the negative electrode active substance contains a zinc alloy. 4. The method according to claim 1, wherein the alkaline electrolyte is an aqueous potassium hydroxide solution containing a zinc compound.
An alkaline battery according to claim 3.