JP2007220374A - Alkaline zinc primary cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cell free from degradation of manufacturing yield due to destruction of a press-molded cathode molded body at handling of the same. <P>SOLUTION: In a cathode mixture 2 for the alkaline zinc primary cell consisting of a mixture of a nickel hydroxide system compound and manganese oxide as a cathode active material, graphite, a binder, and alkaline electrolyte solution, the binder is either a hydrophobic binder, a hydrophilic binder, or a mixture of hydrophobic and hydrophilic binders, and is mixed at a ratio of 0.1 to 2 pts.wt. to 100 pts.wt. of the cathode active material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an alkaline zinc primary battery, and more particularly to an alkaline zinc primary battery with improved workability and discharge capacity during battery production.

  Portable alkaline appliances such as notebook personal computers, CD players, MD players, and liquid crystal televisions, and super heavy loads and heavy loads such as mobile phones have been required for recent alkaline batteries. In order to extract a large current for a long time, it is necessary to suppress a voltage drop during large current discharge. The voltage drop accompanying the discharge of the positive electrode is said to be largely dependent on (1) the proton diffusibility of manganese dioxide itself and (2) the diffusivity of the reactant in the positive electrode. In order to improve these points, studies have been made on basic physical properties of electrolytic manganese dioxide, and attempts have been made to improve the production method. Further, if the surface area of manganese dioxide in the positive electrode is increased, it contributes to the diffusibility of the reactants. Therefore, the reduction of the particle size of electrolytic manganese dioxide has been studied, and further improvement of packing properties has been studied.

  In order to realize high performance in alkaline manganese batteries, increasing the manganese dioxide content in the positive electrode mixture has also been studied. However, increasing the content of manganese dioxide inevitably decreases the content of the graphite powder of the conductive agent contained in the positive electrode mixture. As a result, the formability / conductivity of the positive electrode mixture is decreased and the contact resistance with the positive electrode can is increased, which causes a decrease in short circuit current and heavy load characteristics.

  As an excellent battery with high discharge characteristics, an alkaline battery having an inside-out shape using a nickel hydroxide compound or a mixture of a nickel hydroxide compound and manganese dioxide as a positive electrode active material and zinc as a negative electrode active material It has been known. In these batteries, the positive electrode mixture is mixed with a positive electrode active material and graphite by adding an alkaline electrolyte, and is formed into a hollow cylindrical shape by press molding, which has a bottom with a separator and a gelled zinc negative electrode. A battery is configured by being accommodated in a cylindrical positive electrode can. In alkaline batteries using nickel hydroxide compounds, attempts have been made to improve the discharge capacity, and it is conceivable to reduce the graphite content that does not directly contribute to the discharge capacity. By the way, since the nickel hydroxide compound as the positive electrode active material has a small particle size, it is difficult to maintain the shape, and when trying to reduce the amount of graphite blended from the positive electrode mixture, the shape maintenance becomes a problem. That is, when the positive electrode mixture formed in the hollow cylindrical body by press molding is stored in the positive electrode can, the positive electrode mixture is destroyed by the handling force, which causes a decrease in yield.

Therefore, it is known to solve the above-mentioned problems during handling of the positive electrode active material by using a hydrophobic binder, a hydrophilic binder, or a binder composed of a mixture thereof as a binder (see Patent Document 1). However, in this battery, since the positive electrode active material is composed only of a nickel oxyhydroxide compound, the battery is particularly suitable for application to a medium load device such as a CD player or MD player or a light load device such as a radio. There is a need for improved properties.
JP 2003-017042 A

An object of the present invention is to provide a high-capacity battery that is destroyed during handling and does not reduce the yield of battery production.

  The present invention relates to a positive electrode comprising a mixture of 40 to 80 parts by mass of a nickel hydroxide compound as a positive electrode active material and 60 to 20 parts by mass of manganese dioxide, graphite, a binder, and an alkaline electrolyte. In the mixture, the binder is a hydrophobic binder, a hydrophilic binder, or a mixture of a hydrophobic binder and a hydrophilic binder, and the binder is 0.1 to 2 parts by mass with respect to 100 parts by mass of the positive electrode active material. It is an alkaline zinc primary battery characterized by being blended in proportions.

  In the present invention, the mixing ratio of the nickel hydroxide compound and manganese dioxide is preferably in the range of 40 to 60 parts by mass of nickel hydroxide compound and 60 to 40 parts by mass of manganese dioxide. . If the amount of the nickel hydroxide compound is below this range, it is disadvantageous in the characteristics in the heavy load characteristics. On the other hand, if the amount of the nickel hydroxide compound is above this range, it is disadvantageous in the characteristics of medium to light loads. .

  In the present invention, the surface of the nickel hydroxide compound particles is coated with at least one substance selected from cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide, metallic nickel, and metallic cobalt. It may be a thing.

Moreover, in the said invention, it is preferable that a binder is a mixture of a hydrophobic binder and a hydrophilic binder, and the mixing ratio is the range of 9: 1-5: 5.

As described above, according to the present invention, it is possible to provide a battery capable of realizing a high capacity without reducing the yield of battery manufacturing.

  Hereinafter, detailed embodiments of the battery of the present invention will be described in detail with reference to the drawings. FIG. 1 shows that the present invention is applied to a JIS standard LR6 type (AA) battery called a so-called inside-out structure (a structure in which the battery can body is on the positive electrode side and the battery lid side is on the negative electrode side). It is an example.

  In FIG. 1, reference numeral 1 denotes a bottomed cylindrical metal can also serving as a positive electrode terminal. A positive electrode mixture 2 containing a positive electrode active material formed in a hollow cylindrical shape inside the metal can 1 is an inner surface of the metal can 1. It is accommodated so that it may touch. The hollow interior of the positive electrode mixture 2 is filled with a gel-like zinc negative electrode material 4 via a bottomed cylindrical separator 3 made of a nonwoven fabric of acetalized polyvinyl alcohol fibers. 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 protrudes from the surface of the negative electrode material 4 and serves as a ring-shaped metal plate 7 and a cathode terminal. The metal sealing plate 8 is electrically connected. An insulating gasket 6 made of a double annular polyamide resin is disposed 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 collecting rod 5, and these are insulated. The opening of the metal can 1 is caulked and sealed in a liquid-tight manner.

Below, the positive mix, negative electrode material, and electrolyte solution of this invention are demonstrated in detail.
(Positive electrode mixture)
In the present invention, the positive electrode mixture includes a positive electrode active material composed of a mixture in the range of 40 to 80 parts by mass of nickel hydroxide compound particles and 60 to 20 parts by mass of manganese dioxide, a conductive agent composed of graphite, and alkaline electrolysis. It is composed of a liquid and a binder, and these are mixed and manufactured by press forming into a hollow cylindrical shape whose outer diameter is substantially equal to the inner diameter of the metal can of the battery outer packaging material. In the formed positive electrode mixture, the positive electrode active material particles and the conductive agent particles are bound to each other, and the grain boundary between the particles is filled with the electrolytic solution.

  In the positive electrode active material, if manganese dioxide is more than 60% by weight, it is not preferable because heavy load characteristics are deteriorated. Therefore, the nickel hydroxide compound is in the range of 40% by weight to 80% by weight and manganese dioxide is 60% by weight. To 20% by weight.

  In addition, the same kind and blending of the binder as in the examples of the present invention using a positive electrode active material having a nickel hydroxide compound in the range of 40 wt% to 80 wt% and manganese dioxide in the range of 60 wt% to 20 wt%. In this case, the same effect was obtained.

  In the present invention, a binder is employed in the positive electrode mixture in order to bind the positive electrode mixture components. As this binder, a hydrophobic binder, a hydrophilic binder, or a mixture thereof is used. Examples of the hydrophobic binder used in the present invention include polyethylene, polypropylene, polytetrafluoroethylene, and the like. Among these, polyethylene is particularly preferable because it has a low heat deformation temperature, a high binder function and is inexpensive. Examples of the hydrophilic binder used in the present invention include polyacrylic acid and carboxymethyl cellulose. In the present invention, the blending amount of these binders (with respect to the positive electrode mixture) is preferably in the range of 0.1 to 2% by mass. When the amount of the binder is less than this range, the strength of the positive electrode mixture molded body is low, and it cannot withstand handling during battery assembly. On the other hand, when the amount of the binder exceeds the above range, the volume of the positive electrode active material in the limited battery can is reduced, which causes a decrease in capacity.

  In the present invention, as the binder, a hydrophobic binder alone, a hydrophilic binder alone, or a mixture thereof is used. When a hydrophobic binder is used alone, the effect of improving the strength is high, and a sufficient amount of shape retention is exhibited. However, since this binder has little affinity with the alkaline electrolyte and is electrically insulating, the positive electrode mixture has high internal resistance and deteriorates high rate discharge characteristics. On the other hand, when a hydrophilic binder is used alone, it has a high affinity with the alkaline electrolyte, so there is no risk of an increase in internal resistance, but this binder absorbs the alkaline electrolyte in the battery assembly process after forming the mixture. May swell and deform the molding mixture. Therefore, in the present invention, it is preferable to use a mixture of these two types of binders. In the present invention, the blending ratio of the hydrophobic binder and the hydrophilic binder is preferably in the range of 9: 1 to 5: 5 by mass ratio.

  Examples of the nickel hydroxide compound used in the present invention include nickel hydroxide and nickel oxyhydroxide. The nickel oxyhydroxide compound which is the positive electrode active material used in the present invention is a compound obtained by partially oxidizing nickel hydroxide, and may be γ-nickel oxyhydroxide having a valence of nickel atoms of 3 or water. A compound having a trivalent intermediate valence between a tetravalent nickel atom which is a valence of nickel atoms of nickel oxide and a nickel atom which is completely an oxyhydroxide may be used.

  Further, the surface of the nickel hydroxide compound particles used in the present invention is coated with at least one substance selected from cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide, metallic nickel, and metallic cobalt. May be.

  Further, the nickel hydroxide-based compound itself that is the positive electrode active material may be eutectic with zinc or cobalt alone or both. This positive electrode active material is characterized in that stable discharge can be performed even at a low electrolyte ratio. The amount of zinc or cobalt to be eutectic in this nickel hydroxide compound is preferably in the range of 4 to 12%. This is because if the amount of zinc is below this range, there will be a problem of lowering the utilization factor, and if it exceeds this range, there will be a problem that the capacity density will decrease due to a decrease in specific gravity.

Moreover, the capacity maintenance rate at the time of storage can be improved by adding the compound of Y, Er, Yb, and Ca to the said positive electrode active material. Examples of the compound used in the present invention, for example, _{Y 2 O 3, Er 2 O} 3, Yb 2 O 3, metal oxides, and the like, and metal fluorides such as CaF ₂ and the like. These metal oxides and metal fluorides can be used in the range of 0.1 to 10% by mass with respect to the positive electrode active material. When the compounding amount of the metal oxide or metal fluoride is below the above range, a sufficient effect cannot be obtained. On the other hand, when the blending amount exceeds the above range, a problem of capacity reduction occurs, which is not preferable. In the present invention, in order to add a metal oxide or metal fluoride to the positive electrode active material, it is produced by adding the metal oxide particles or metal fluoride particles to the positive electrode active material dispersed in an aqueous medium. can do.

  The nickel hydroxide particles of the present invention can be produced by the following method. Nickel hydroxide can be produced by gradually adding an aqueous sodium hydroxide solution and an aqueous ammonia solution to an aqueous nickel sulfate solution while stirring to maintain the pH of the solution at 13-14. At this time, nickel hydroxide doped with zinc and cobalt can be produced by using a solution in which zinc sulfate and cobalt sulfate aqueous solution are mixed with nickel sulfate aqueous solution. Further, nickel oxyhydroxide can be produced by adding an oxidizing agent such as sodium hypochlorite to the nickel hydroxide thus produced and proceeding with oxidation. Further, in order to coat the surface of these nickel hydroxide compound particles with a cobalt-based or nickel-based material, for example, cobalt hydroxide is added to nickel hydroxide particles, and an aqueous sodium hydroxide solution is added while stirring in the atmosphere. By spraying and subsequently applying microwave heating, it is possible to produce composite nickel hydroxide particles in which a layer of higher cobalt oxide is formed on the nickel hydroxide surface. By this method, a positive electrode active material having excellent conductivity can be obtained.

  Moreover, in this invention, a graphite particle is mix | blended in the said positive mix, and electroconductivity is improved. In the present invention, the content of the graphite particles in the positive electrode mixture is preferably 10% by mass or less. If the graphite particle content in the positive electrode mixture is excessively increased, the amount of the positive electrode active material that can be filled in the limited volume of the metal can itself decreases, and the carbonate ions that are generated when the graphite particles are oxidized. This is because the self-discharge is accelerated and the discharge capacity is reduced. For this purpose, the content of carbon particles in the positive electrode mixture is preferably 10% by mass or less, more preferably in the range of 3% by mass to 7% by mass.

(Negative electrode material)
The negative electrode material used in the present invention is a negative electrode material mainly composed of a zinc alloy, which is a negative electrode active material, and zinc gel used in known alkaline manganese primary batteries can be used. This negative electrode material is preferably in the form of a gel in terms of handling. In order to make the negative electrode material into a gel, it can be easily gelled by adding an electrolyte and a thickener to the negative electrode active material.

  The zinc alloy used in the present invention may be a zinc alloy that does not contain mercury and lead, which is known as a non-anneaded zinc alloy. Specifically, a zinc alloy containing 0.01 to 0.06 mass% indium, 0.005 to 0.02 mass% bismuth, and 0.0035 to 0.015 mass% aluminum has an effect of suppressing generation of hydrogen gas. There is desirable. In particular, indium and bismuth are desirable for improving the discharge performance. The reason for using a zinc alloy instead of pure zinc as the negative electrode active substance is that the self-dissolution rate in the alkaline electrolyte is slowed down to suppress hydrogen gas generation inside the battery when it is used as a sealed battery product. This is to prevent accidents caused by liquid.

  Moreover, it is desirable that the shape of the zinc alloy is powdery so that the surface area can be increased to cope with a large current discharge. The average particle diameter of the zinc alloy preferable in the present invention is preferably in the range of 90 to 210 μm. When the average particle diameter of the zinc alloy exceeds the above range, the surface area becomes relatively small and it becomes difficult to cope with the large current discharge. Also, if the average particle size is below the above range, handling during battery assembly is difficult, and it becomes difficult not only to mix uniformly with the electrolyte and gelling agent, but also because the surface is active, it is oxidized. It is easy and unstable.

  Moreover, as a thickener used in this invention, polyvinyl alcohol, polyacrylate, CMC, alginic acid, etc. can be used. In particular, polyacrylic acid is preferable because of its excellent chemical resistance to strong alkalis.

(Electrolyte)
The electrolytic solution used in the present invention is preferably an aqueous solution using an alkaline substance such as potassium hydroxide or sodium hydroxide as the electrolyte, and particularly preferably potassium hydroxide is used as the electrolyte. In the present invention, the electrolyte such as potassium hydroxide is dissolved in water to form an electrolytic solution. It is desirable to add a zinc compound to the electrolytic solution. Such zinc compounds include compounds such as zinc oxide and zinc hydroxide, with zinc oxide being particularly preferred.

The alkaline aqueous solution containing at least a zinc compound is used as the electrolytic solution because the zinc alloy self-dissolution in the alkaline aqueous solution is remarkably less than that of the acidic electrolytic solution, and further in the alkaline electrolytic solution of zinc alloy. This is to further suppress the self-dissolution of the compound by dissolving a zinc compound, for example, zinc oxide, and pre-existing zinc ions. The concentration of the electrolytic solution is optimally in the range of 7 to 11 mol / l in order to obtain high electric conductivity.

Examples of the present invention and comparative examples will be described in detail below.
Example 1
First, 8 parts by mass of graphite as a conductive agent is added to 50 parts by mass of nickel oxyhydroxide powder and 50 parts by mass of electrolytic manganese dioxide, and then 0.1 part by mass of particulate polyethylene resin is added as a binder, followed by dry stirring. After 10 minutes at a rotational speed of 300 rpm, 5 parts by weight of 40% by weight caustic potash aqueous solution as a kneading liquid is added, wet stirring is performed for 10 minutes at a rotational speed of 300 rpm, and further, the wet stirring is rotated for uniform mixing. The stirring mixture was carried out at several 600 rpm for 10 minutes. Subsequently, the stirring mixture was compacted at a compressive strength of 1.96 × 103 MPa (200 kg / mm ² ) to produce a thin piece. Furthermore, the granule mixture was produced by crushing the thing of a thin piece state using a classifier. Then, this granule mixture is pressure-molded into a hollow cylindrical shape to produce a positive electrode mixture pellet, which is inserted into the positive electrode can. In this way, the AA alkaline zinc primary battery shown in FIG. 1 was assembled.

(Examples 2 to 24)
A battery was produced in the same manner as in Example 1 except that the type and blending amount of the binder were as shown in Table 1.

(Comparative Examples 1-17)
A battery was produced in the same manner as in Example 1 except that the type and amount of the binder were as shown in Table 2.

(Evaluation)
The battery manufactured by the above method was evaluated by the following method.

[Method for measuring strength of molded positive electrode mixture]
A hollow cylindrical positive electrode mixture molded body is compressed in the radial direction, and the strength when broken is measured with a rheometer.

[Method for measuring expansion coefficient of molded article]
The inner diameter, outer diameter, and height of the hollow cylindrical positive electrode mixture molded body are measured to determine the volume. After being immersed in a 40% by mass aqueous caustic potash solution for 10 minutes, the sample is taken out and the inner diameter, outer diameter, and height are measured again. From this, it is divided by the volume before immersion to obtain the expansion coefficient of the molded body.

[Discharge performance measurement method]
Discharge at 1,000 mA 10 s / m * 1 hour / day at 20 ° C., and measure the discharge capacity until the closed circuit voltage reaches 0.9V. In the above three types of evaluation, Tables 1 and 2 show the relative values when Comparative Example 1 is taken as 100%.

  From the results of Examples 1 to 24 and Comparative Examples 1 to 17, when the strength of the molded product is seen, when polyethylene, polypropylene or polyacrylic acid is used alone as a binder, and a mixture of polyethylene and polyacrylic acid is used. In any case, the strength increases as the amount added increases. By setting the addition amount to 0.1 parts by mass or more, it is possible to achieve a strength increase of 10% or more with respect to the additive-free Comparative Example 1, and to improve the yield of battery manufacturing. When the hydrophobic binder is added, the expansion coefficient of the molded body decreases as compared with the expansion coefficient of the additive-free Comparative Example 1, but increases when the hydrophilic binder is added. In Comparative Example 7, Comparative Example 15 and Comparative Example 17 in which the expansion ratio exceeded 116%, the predetermined gel could not be filled, and the battery could not be manufactured. As the discharge performance, when the addition amount of the hydrophobic binder is small, the expansion rate of the positive electrode mixture is reduced, so that the contact of the positive electrode active material is good and the discharge performance is improved, but when the addition amount exceeds 2 parts by mass. The influence as an insulator is increased, and the performance deterioration more than the capacity reduction due to the addition occurs. On the other hand, in the case of a hydrophilic binder, the discharge performance is also improved because the liquid retention capacity of the electrolytic solution is improved by increasing the addition amount. However, when the addition amount exceeds 2 parts by mass, the performance improvement rate is lowered due to the volume reduction of the active material due to the addition of the binder. Further, it has been found that the expansion rate is too high, causing inconvenience in battery production.

(Examples 25-29, Comparative Examples 18-28)
A battery was produced in the same manner as in Example 1 except that the type and blending amount of the positive electrode active material and the type and blending amount of the binder were as shown in Table 3, respectively. Evaluated. The results are also shown in Table 3. The following evaluation was added.

[Method for measuring additional discharge performance]
A continuous discharge of 150 mA was performed at 20 ° C., and the discharge capacity until the closed circuit voltage reached 0.9 V was measured. In each evaluation of the above Table 3, the value of each inspection item is shown as a relative value when the comparative example 1 is 100%.

As is clear from the results in Table 3, when the composition of the positive electrode active material and the composition of the binder are within the scope of the present invention, a battery having a high capacity and excellent heavy load discharge characteristics is obtained. It became clear that it can manufacture with a manufacturing yield.

Sectional drawing which shows an example of the inside out type | mold battery suitable for applying this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Metal container 2 ... Positive electrode mixture 3 ... Separator 4 ... Gel-like negative electrode 5 ... Negative electrode current collecting rod 6 ... Insulating gasket 7 ... Metal plate 8 ... Metal sealing plate

Claims (4)

In a positive electrode mixture consisting of a mixture of a nickel hydroxide compound and manganese dioxide, which is a positive electrode active material, graphite, a binder, and an alkaline electrolyte,
The binder is a hydrophobic binder, a hydrophilic binder, or a mixture of a hydrophobic binder and a hydrophilic binder, and the binder is blended at a ratio of 0.1 to 2 parts by mass with respect to 100 parts by mass of the positive electrode active material. An alkaline zinc primary battery characterized by comprising:   2. The alkaline zinc primary battery according to claim 1, wherein the positive electrode active material is a mixture containing a nickel hydroxide compound in a range of 40 parts by mass to 80 parts by mass and manganese dioxide 60 parts by mass to 20 parts by mass. .   2. The alkaline zinc primary battery according to claim 1, wherein the positive electrode active material is a mixture containing a nickel hydroxide compound in a range of 40 to 60 parts by mass and manganese dioxide in a range of 60 to 40 parts by mass. . 4. The binder according to claim 1, wherein the binder is a mixture of a hydrophobic binder and a hydrophilic binder, and the mixing ratio is in the range of 9: 1 to 5: 5. Alkaline zinc primary battery.

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