JP2016033856A - Flat type alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat type alkaline battery of which the productivity is improved.SOLUTION: The flat type alkaline battery includes a positive electrode formed from a compact of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator and an alkaline electrolyte within a sealed space formed by fitting a sealing plate through a resin gasket to an opening of an outer can and fastening an opening end of the outer can inwards. The sealing plate includes a top face wall, a curved part that is curved downwards from the top face wall, and a peripheral folding part. On a surface of the curved part inside of the battery and a surface of the peripheral folding part closer to the outer can, a location including ten or more recesses of which the diameter is 0.5 to 5 μm is present within an area of 100 μm×100 μm, and the flat type alkaline battery includes antirust coating.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a flat alkaline battery with good productivity.

  Flat alkaline batteries such as buttons and coins, such as silver oxide batteries that use silver oxide as the positive electrode, generally have a power generation element including a positive electrode, a negative electrode, and an alkaline electrolyte. And a sealing plate having a peripheral folded portion and a resin gasket, and the resin gasket is placed between the peripheral folded portion of the sealing plate and the outer can by tightening the opening end of the outer can inward. It is formed by sealing the opening of the outer can in pressure contact with the inner peripheral surface of the opening end.

  However, when the flat alkaline battery is manufactured, when the outer can and the sealing plate are fitted, the alkaline electrolyte contained in the outer can may leak to the outside. When such leakage of the alkaline electrolyte occurs, it becomes necessary to clean the alkaline electrolyte component adhering to the outside of the flat alkaline battery after manufacture, and the productivity of the flat alkaline battery decreases. Moreover, there is a possibility that electrical connection between the battery and the external device may be hindered due to the leaked electrolyte. In recent years, there have been small-sized batteries with the spread of applications of flat alkaline batteries. However, in such batteries in particular, problems due to leakage of the alkaline electrolyte tend to occur.

  For these reasons, in flat alkaline batteries, there is a demand for development of a technique that avoids problems caused by leakage of alkaline electrolyte during production.

  Although not intended to suppress the leakage of alkaline electrolyte during the production of flat alkaline batteries, for example, in Patent Documents 1 and 2, the surface of the sealing plate that contacts the resin gasket is smoothed by polishing. A technique has been proposed in which a rust-preventing film containing a triazole-based compound as a main component is formed in that portion, thereby improving the leakage resistance of a flat alkaline battery after production.

Japanese Patent Publication No.58-41627 JP-A-8-190901

  This invention is made | formed in view of the said situation, The objective is to provide a flat alkaline battery with favorable productivity.

  In the flat alkaline battery of the present invention that can achieve the above object, a sealing plate is fitted to the opening of the outer can via a resin gasket, and the opening end of the outer can is tightened inward. A flat alkaline battery having a positive electrode composed of a molded product of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator, and an alkaline electrolyte in a sealed space formed by: The upper surface wall, a curved portion curved downward from the upper surface wall, and a peripheral folded portion, a surface on the battery inside of the curved portion, and a surface on the outer can side of the peripheral folded portion, In the region of 100 μm × 100 μm, there are locations having 10 or more recesses having a diameter of 0.5 to 5 μm, and the inner surface of the curved portion on the battery inner side and the peripheral folded portion on the outer can side surface It is characterized in that the anticorrosive coating containing a triazole compound is formed.

  In the battery industry, a flat battery with a diameter larger than the height is called a coin-type battery or a button-type battery, but there is a clear difference between the coin-type battery and the button-type battery. The flat alkaline battery of the present invention includes both coin-type batteries and button-type batteries.

  According to the present invention, a flat alkaline battery with good productivity can be provided.

It is a side view which represents typically an example of the flat alkaline battery of this invention. It is principal part sectional drawing of the flat alkaline battery represented in FIG. FIG. 3 is a partially enlarged view of FIG. 2. It is principal part sectional drawing which represents typically the other example of the flat alkaline battery of this invention.

  FIG. 1 is a side view schematically showing an example of the flat alkaline battery of the present invention, and FIG. 2 is a cross-sectional view of the main part of the flat alkaline battery of FIG.

  In the flat alkaline battery shown in FIG. 1 and FIG. 2, a sealing plate 2 having a negative electrode 4 embedded in an opening of an outer can 1 having a positive electrode 3 and a separator 5 formed of a positive electrode mixture molded body, It is fitted through an annular resin gasket 6 with an L-shaped cross section, and the opening end of the outer can 1 is tightened inward, whereby the resin gasket 6 abuts against the sealing plate 2, The opening of the outer can 1 is sealed so that the inside of the battery has a sealed structure. That is, the flat alkaline battery shown in FIGS. 1 and 2 includes the positive electrode 3, the negative electrode 4, and the separator 5 in the space (sealed space) in the battery container including the outer can 1, the sealing plate 2, and the resin gasket 6. A power generation element is loaded, and an electrolyte (not shown) is injected. The outer can 1 also serves as a positive terminal, and the sealing plate 2 also serves as a negative terminal.

  FIG. 3 shows an enlarged view of a part of FIG. In FIG. 3, in order to facilitate understanding of the configuration of the sealing plate 2, oblique lines indicating a cross-sectional view are omitted.

    As shown in FIG. 3, in the flat alkaline battery of the present invention, the sealing plate 2 has an upper surface wall 2a, a curved portion 2b curved downward from the upper surface wall 2a, and a peripheral folded portion 2c. The curved portion 2b of the sealing plate 2 is a portion having both ends of a dotted line in the vertical direction in the figure, and when the sealing plate 2 is viewed in cross section, a changing point where the downward curve starts from the substantially flat upper surface wall 2a. Is the starting point, and the next is the portion that ends in the upward direction (that is, the boundary with the peripheral folded portion 2c). Further, the peripheral folded portion 2c of the sealing plate 2 means a portion extending upward from the battery starting from the end of the curved portion 2b curved downward from the upper surface wall 2a (change point going upward). ing.

  And the flat alkaline battery of this invention is a recessed part with a diameter of 0.5-5 micrometers in the area | region of 100 micrometers x 100 micrometers in the surface at the side of the armored can 1 of the curved part 2b of the sealing board 2, and the periphery folding | turning part 2c. There are locations having 10 or more (hereinafter sometimes referred to as “recessed portion formation locations”).

  In FIG. 3, the part which becomes a recessed part formation location among the sealing plates 2 is shown with the thick broken line.

  In a conventional flat alkaline battery, from the viewpoint of improving the liquid leakage resistance with time, a sealing rust preventive film is formed prior to forming a rust preventive film containing a triazole compound on the battery inner surface of the sealing plate. The plate surface was smoothed by chemical polishing treatment.

  On the other hand, in the flat alkaline battery of the present invention, the smoothness is not increased on the surface inside the battery of the curved portion of the sealing plate and the surface on the outer can side of the peripheral folded portion, but the above-described portions are not included in these portions. In the above conventional flat alkaline battery, particularly when the battery size (battery diameter) is reduced, an outer can containing an alkaline electrolyte is produced. It is possible to suppress leakage of the alkaline electrolyte at the time of fitting with the sealing plate.

  The reason why it is possible to suppress leakage of the alkaline electrolyte during the production of the flat alkaline battery by providing the concave portion is not certain, but in the concave portion provided at the end of the sealing plate, for example, It is considered that the water repellency is improved as compared with the location where the property is improved, and this contributes to suppression of leakage of the alkaline electrolyte when the outer can and the sealing plate are fitted.

  In flat alkaline batteries, when the outer can and the sealing plate are fitted, an alkaline electrolyte is sandwiched between the sealing plate and the resin gasket, and this leaks out when the battery is stored or used. There is also a fear. However, in the case of the flat alkaline battery of the present invention, leakage due to these reasons can also be satisfactorily suppressed. The reason for this is not clear, but it is thought that the water repellency improving action by the recess formed at the end of the sealing plate contributes, and the alkaline electrolyte leaks out of the battery by forming a large number of recesses. It is presumed that the distance until this is also contributed to be longer than when the sealing plate surface is smooth.

  It is sufficient that at least 10 recesses having a diameter of 0.5 to 5 μm exist in a region of 100 μm × 100 μm in the recess formation location, and the recess has a diameter of less than 0.5 μm or exceeds 5 μm in this region. A recess may be present. However, from the viewpoint of making the above-described effect due to the concave portion formation more favorable, it is more preferable that the diameters of all the concave portions existing in the region are within the range of 0.5 to 5 μm.

  In the recessed portion forming portion, the number of recessed portions having a diameter of 0.5 to 5 μm existing in a region of 100 μm × 100 μm may be 10 or more, and more preferably 100 or more. However, there is a limit to the number of recesses having a diameter of 0.5 to 5 μm that can exist in a region of 100 μm × 100 μm, and it is usually preferable to be 500 or less.

  In the region of 100 μm × 100 μm corresponding to the recessed portion forming portion, the recessed portions having a diameter of 0.5 to 5 μm may be arranged regularly or irregularly.

  In the sealing plate of the flat alkaline battery, when the total area of the battery inner surface of the curved portion and the outer can side surface of the peripheral folded portion is divided for each region of 100 μm × 100 μm, 80% or more thereof is It is preferable that it corresponds to the recessed part formation location in which 10 or more recessed parts with a diameter of 0.5-5 micrometers exist. In this case, the above-described effect due to the provision of the recess forming portion becomes better. In addition, since all of the curved portion of the sealing plate and the inner surface of the peripheral folded portion and the surface of the peripheral folded portion on the outer can side may be a concave portion, the total area of these surfaces is 100 μm × 100 μm. The upper limit value of the ratio that preferably corresponds to a recess forming portion where 10 or more recesses having a diameter of 0.5 to 5 μm are present is divided by 100%.

  Although there is no restriction | limiting in particular about the depth of a recessed part, It is preferable that it is 0.5-50 micrometers.

  Further, the inner surface of the battery on the upper surface wall of the sealing plate may also be provided with a concave portion where ten or more concave portions having a diameter of 0.5 to 5 μm are present in a region of 100 μm × 100 μm. The entire surface of the inner surface of the battery on the wall may be a recess forming portion.

  In the present specification, “the number of recesses having a diameter of 0.5 to 5 μm present in a region of 100 μm × 100 μm” is a value obtained by the method described in Examples described later. Further, in this specification, “the total area of the battery inner surface of the curved portion of the sealing plate and the surface of the peripheral folded portion on the outer can side is divided into regions of 100 μm × 100 μm in a range of 0.5 to The ratio corresponding to the recessed portion forming portion where there are 10 or more 5 μm recessed portions is determined by the method described in the examples described later. Divide the total area of the region where the “number” satisfies the predetermined value by the total area of the battery inner surface of the curved portion of the sealing plate and the surface of the peripheral folded portion on the outer can side, and calculate this by percentage. Value.

  By providing the recessed portion forming portion as described above, the surface roughness of the battery inner surface of the curved portion of the sealing plate and the surface of the peripheral folded portion on the outer can side (that is, a state where there is no rust preventive film described later, i.e., The surface roughness before the rust coating is formed can be 5 to 50 μm in terms of arithmetic average roughness Ra. As a result, the surface roughness of the anticorrosive coating (thickness: about 5 to 100 nm) formed on the battery inner surface of the curved portion and the outer can side surface of the peripheral folded portion is also within the arithmetic average roughness range. When the sealing plate as described above is used, the productivity of the flat alkaline battery can be improved more favorably.

  The “surface roughness of the inner surface of the battery of the curved portion of the sealing plate and the surface of the peripheral folded portion on the side of the outer can” and the “surface roughness of the anticorrosive coating” as used in this specification It means arithmetic average roughness Ra measured by a simple surface roughness measuring instrument.

  Further, it is preferable that a rust preventive film containing a triazole-based compound is formed on the inner surface of the battery of the curved portion of the sealing plate and the outer can side of the peripheral folded portion, and the upper surface wall of the sealing plate. Moreover, it is more preferable that the rust preventive film is formed. The action of the anticorrosive film and the action of the recesses combine to improve the liquid leakage resistance with time of the flat alkaline battery. In addition, by forming a rust preventive film on the surface of the above-mentioned recessed portion forming portion, it is expected that the durability of the rust preventive film is improved by the anchor effect.

  Examples of the triazole compound for forming the rust-preventing film include triazoles and carboxylic acid derivatives of triazoles. Examples of triazoles include benzotriazole, 1,2,3-triazole, 1-methyl-1,2,3-triazole, 1-amino-1,2,3-triazole and the like. Examples of carboxylic acid derivatives of triazoles include 2-benzothiazylthioacetic acid, methyl 1-benzotriazolecarboxylate, and 1-benzotriazole acetic acid. For the formation of the anticorrosive film, only one of the exemplified triazole compounds may be used, or two or more of them may be used in combination.

  Moreover, the rust preventive film may contain components other than the triazole compound. Examples of such components include organic corrosion inhibitors such as cysteine, p-aminobenzaldehyde, and salicylandoxime.

  It is preferable that content of the triazole type compound in a rust preventive film is 5-100 mass%.

  Moreover, the said recessed part formation location in a sealing plate (The battery inner side surface of the curved part in a sealing plate, and the surface in the exterior can side of a periphery folding | turning part. However, when a rust prevention film is formed in these surfaces More preferably, pitch (coal tar pitch) is applied to the surface of the anticorrosive coating formed on these surfaces. In this case, the liquid leakage resistance with time of the flat alkaline battery is further improved.

  The sealing plate is usually provided with a nickel layer for improving aesthetics or corrosion resistance on one side of the steel plate, and copper for preventing the formation of a local battery with zinc as the negative electrode active material on the other side of the steel plate. Or it is comprised with the clad board which provided the copper alloy layer. Then, the clad material is drawn so that the nickel layer side becomes the battery outer side and the copper or copper alloy layer becomes the battery inner side, thereby forming a shape having a top wall, a curved portion, and a peripheral folded portion and sealing A plate is formed.

  Examples of the copper alloy of the copper or copper alloy layer in the clad material constituting the sealing plate include copper-tin alloy, brass, phosphor bronze, oxygen-free copper and the like.

  The sealing plate having the above shape is usually subjected to degreasing treatment, and then, for example, the surface of the copper or copper alloy layer of the sealing plate by a chemical polishing method using a hydrogen peroxide-sulfuric acid-based abrasive (i.e., the upper surface wall, The inner surface of the battery of the curved portion and the peripheral folded portion, and the outer can side surface of the peripheral folded portion) are chemically polished.

  In order to improve the smoothness of the surface of the sealing plate prior to the formation of the anticorrosive film as in the past, the sealing plate after chemical polishing is once washed with water, and then the sealing plate is acid washed with a sulfuric acid pickling solution. Then, the oxide film formed on the surface of the copper or copper alloy layer of the sealing plate is removed, but in order to provide the recess formation portion, acid cleaning with a pickling solution is performed without performing water washing after chemical polishing. Just do it. Further, hydrogen peroxide may be added to the pickling solution at the time of pickling. The recess can be formed while removing the oxide film by including hydrogen peroxide during pickling.

  Here, chemical polishing is carried out for 5 to 90 seconds using a solution obtained by adding 0.5 to 1.0 wt / vol of hydrogen peroxide to sulfuric acid having a concentration of 1 to 10% by mass. Further, the acid cleaning with the pickling solution is carried out for 10 to 90 seconds using a solution obtained by adding 0.01 to 0.5 wt / vol of hydrogen peroxide to sulfuric acid having a concentration of 1 to 10% by mass. Formation can be performed more effectively.

  The sealing plate after the acid cleaning with the pickling solution is formed with the rust preventive coating on the surface as necessary. For the formation of the anticorrosive film, for example, a composition containing a constituent material of the anticorrosive film such as a triazole compound and a solvent (water; methanol, alcohols of ethanol, etc.) is prepared, and this is applied to the sealing plate. It is possible to employ a method of drying after applying to a place where a rust film is to be formed or immersing a place where a rust preventive film is to be formed on a sealing plate in the composition.

  In addition, in order to apply the pitch to a predetermined portion of the sealing plate, the pitch may be applied to the sealing plate after the acid washing with the pickling solution or after the formation of the rust preventive film by a conventional method.

  The flat alkaline battery of the present invention is a sealed space formed by fitting a sealing plate to an opening of an outer can through a resin gasket and fastening the opening end of the outer can inward. If it has a positive electrode made of a molded body of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator, and an alkaline electrolyte, and the sealing plate has been described so far In addition, there is no restriction | limiting in particular about another structure and structure, The structure and structure employ | adopted by the flat alkaline battery known conventionally can be applied.

  For the positive electrode related to the flat alkaline battery, for example, active materials such as silver oxide (eg, silver oxide, silver oxide), manganese dioxide, nickel oxyhydroxide, silver and cobalt, nickel or bismuth are combined. It is formed by mixing a material and the like, a conductive additive, and further an electrolytic solution for forming and a binder to form a positive electrode mixture, and press forming the positive electrode mixture into a ring shape or the like.

  When silver oxide is used as the positive electrode active material, the silver oxide is preferably granular. Usually, silver oxide is provided in the form of a fine powder having a diameter of 0.1 to 5 μm. However, when this silver oxide is granulated and used in a granular form, the resistance is higher than when it is used in a fine powder state. Since it becomes low, the load characteristic of a silver oxide battery can be improved more.

  When silver oxide is used in a fine powder state, it is necessary to add a larger amount of conductive aid to reduce resistance, but the carbonaceous material used as the conductive aid has a low bulk density. If it is added too much, it becomes difficult to increase the filling amount of silver oxide as an active material. On the other hand, when granular silver oxide is used, weighability is improved and variation is reduced, and when press molding is performed, filling property is increased and moldability is improved, so that resistance is reduced, When a plurality of positive electrodes (and thus flat alkaline batteries) are manufactured, individual characteristics are stabilized. Furthermore, the amount of carbonaceous material added as a conductive auxiliary agent can be reduced, and the amount of silver oxide filled can be increased.

Furthermore, for example, in the case of silver oxide, the discharge performance is lowered because the reaction is caused by the reaction with the carbonaceous material as shown below.
2Ag ₂ O + C → 4Ag + CO ₂

  However, by making silver oxide into granules, the above reaction is suppressed, and the amount of carbonaceous material added can be reduced as described above. Characteristics (especially low temperature heavy load characteristics) are improved.

In the positive electrode according to the present invention, when granular silver oxide is used, the particle size is preferably 50 μm or more, more preferably 75 μm or more, preferably 500 μm or less, more preferably 300 μm or less, The bulk density is preferably 1.5 g / cm ³ or more, more preferably 1.8 g / cm ³ or more, preferably 3.5 g / cm ³ or less, more preferably 2.6 g / cm ^3. It is as follows. If the silver oxide is in such a form, it has better fluidity than the powdered one, and as described above, the weighing property and formability are improved, the resistance is lowered, and the reactivity is improved. The characteristics are more excellent, and the characteristics of the individual positive electrodes (and thus silver oxide batteries) to be manufactured are stabilized. The particle size of granular silver oxide here is determined by measuring the number of particles n and the diameter d of each particle by scattering of laser light using a microtrack particle size distribution meter “9320-X100” manufactured by Honeywell. The calculated number average particle diameter. Further, the bulk density of the granular silver oxide referred to here is a value obtained by putting a predetermined amount of granular silver oxide into a container and using a bulk density measuring device in accordance with the bulk density measuring method specified in JIS R 1628. It is.

  For example, graphite, ketjen black, acetylene black, or the like can be used as the conductive additive related to the positive electrode. The amount of the conductive additive in the positive electrode mixture is preferably, for example, 3 to 8.5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  As the binder for the positive electrode, for example, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, or the like can be used. The amount of the binder in the positive electrode mixture is preferably 0.1 to 1% by mass, for example.

  The negative electrode according to the flat alkaline battery contains zinc particles or zinc alloy particles (hereinafter sometimes collectively referred to as “zinc-based particles”), and zinc in these particles acts as an active material. . Examples of the alloy component of the zinc alloy particles include indium (for example, the content is 50 to 500 mass ppm), bismuth (for example, the content is 50 to 500 mass ppm), and the like (the balance is zinc and inevitable impurities). is there). The zinc-based particles possessed by the negative electrode may be one type alone or two or more types.

  However, it is preferable to use zinc-based particles that do not contain mercury as an alloy component. A battery using such zinc-based particles can suppress environmental pollution due to battery disposal. For the same reason as mercury, it is preferable to use zinc-based particles that do not contain lead as an alloy component.

  Examples of the zinc-based particles include particles in which the ratio of the powder having a particle diameter of 100 to 200 μm is 50% by volume or more, more preferably 90% by volume or more in the total powder. The volume ratio of the powder having a particle diameter of 100 to 200 μm in the zinc-based particles herein is measured by the same measuring method and measuring apparatus as the particle diameter measuring method of the “granular silver oxide”.

  The zinc-based particles used for the negative electrode may have the above-mentioned form, but from the viewpoint of further improving the load characteristics of the battery, for example, among all the particles in the zinc-based particles, the particle size is 75 μm or less. The ratio of the particles is preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. In this way, when the zinc-based particles of the negative electrode are small, the specific surface area of the entire negative electrode can be increased, so that the reaction at the negative electrode can be promoted efficiently, and the load characteristics (especially heavy load characteristics) of the battery are further improved. It becomes possible to raise. The ratio of particles having a particle size of 75 μm or less in the zinc-based particles can be determined by measuring the ratio of particles that can pass through a 75 μm mesh screen (200 mesh screen).

  From the viewpoint of increasing the reaction efficiency at the negative electrode by reducing the size of the zinc-based particles possessed by the negative electrode, the proportion of particles having a particle size of 45 μm or less among the zinc-based particles possessed by the negative electrode is 30% by mass. Preferably, it is 50% by mass or more, more preferably 75% by mass or more, and the proportion of particles having a particle size of 32 μm or less is 20% by mass or more. Preferably, it is more preferably 30% by mass or more, and further preferably 50% by mass or more. In addition, since the handleability falls when the size of the zinc-based particle which the negative electrode has is too small, for example, the minimum size of the zinc-based particle which the negative electrode has is desirably about 1 μm. The ratio of particles having a particle size of 45 μm or less in the zinc-based particles is determined by measuring the ratio of particles that can pass through a 45 μm mesh sieve (330 mesh sieve mesh). The ratio of particles having a particle size of 32 μm or less can be determined by measuring the ratio of particles that can pass through 32 μm openings (440 mesh openings).

  The negative electrode includes, for example, a gelling agent (polyacrylic acid soda, carboxymethyl cellulose, etc.) added as necessary in addition to the zinc-based particles, and is configured by adding an alkaline electrolyte thereto. A negative electrode agent (gelled negative electrode) can be applied. The amount of the gelling agent in the negative electrode is preferably 0.5 to 1.5% by mass, for example.

  The negative electrode may be a non-gelled negative electrode that does not substantially contain the gelling agent as described above (in the case of a non-gelled negative electrode, the electrolyte present in the vicinity of the zinc-based particles is thickened). Therefore, “substantially no gelling agent” means that it may be contained to the extent that it does not affect the electrolyte viscosity). In the case of a gelled negative electrode, an electrolyte solution is present together with the gelling agent in the vicinity of the zinc-based particles, but this electrolyte solution is thickened by the action of the gelling agent, and the electrolyte solution moves. The movement of ions in the electrolyte is suppressed. For this reason, the reaction rate at the negative electrode is suppressed, which is considered to hinder the improvement of the load characteristics (particularly heavy load characteristics) of the battery. On the other hand, by making the negative electrode non-gel, keeping the ion moving rate in the electrolytic solution high without increasing the viscosity of the electrolytic solution present in the vicinity of the zinc-based particles, increasing the reaction rate at the negative electrode, Load characteristics (particularly heavy load characteristics) can be further enhanced.

  As an alkaline electrolyte of a flat alkaline battery, for example, an alkaline aqueous solution made of an aqueous solution of an alkali metal hydroxide such as potassium hydroxide, sodium hydroxide, or lithium hydroxide, or a solution added with zinc oxide is used. be able to. The concentration of the alkali metal hydroxide in the alkaline electrolyte is preferably 28 to 38% by mass in the case of potassium hydroxide, for example, and when zinc oxide is used, the concentration is 1.0. It is preferable that it is -4.0 mass%.

  The separator of the flat alkaline battery is not particularly limited. For example, a nonwoven fabric mainly composed of vinylon and rayon, vinylon / rayon nonwoven fabric (vinylon / rayon mixed paper), polyamide nonwoven fabric, polyolefin / rayon nonwoven fabric, vinylon paper, vinylon Linter pulp paper, vinylon mercerized pulp paper, and the like can be used. A hydrophilic microporous polyolefin film (microporous polyethylene film, microporous polypropylene film, etc.), cellophane film, and liquid absorbing layer (electrolyte holding layer) such as vinylon / rayon mixed paper were stacked. It is good also as a separator.

  As the outer can of the flat alkaline battery, iron plated nickel or stainless steel can be used. A resin gasket made of nylon 66 or the like is recommended.

  The shape of the flat alkaline battery in a plan view may be a circle or a polygon such as a quadrangle (square or rectangle). In the case of a polygon, the corner may be curved.

  FIG. 4 is a cross-sectional view of a main part schematically showing another example of the flat alkaline battery of the present invention. The battery of FIG. 3 employs a so-called bottom structure in which the outer peripheral portion of the positive electrode (positive electrode mixture molded body) 3 is disposed between the inner bottom surface of the outer can 1 and the resin gasket 6.

  The battery shown in FIG. 2 employs a so-called centering structure in which the resin gasket 6 reaches the bottom of the outer can 1, and therefore the portion of the battery internal volume occupied by the gasket 6 not involved in power generation. Is big. On the other hand, the battery shown in FIG. 4 employs a bottom structure to increase the positive electrode filling amount (positive electrode active material filling amount) in the battery, thereby further increasing the capacity. be able to.

  The flat alkaline battery of the present invention can be applied to the same uses as various uses in which conventionally known flat alkaline batteries are used.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
A flat alkaline battery having the appearance shown in FIG. 1 and the structure shown in FIGS. 3 and 4 was produced.

<Preparation of sealing plate>
The sealing plate 2 is formed by drawing a clad plate having a nickel layer on one surface of the steel plate and a copper layer on the other surface, so that the curved portion curved downward from the upper surface wall 2a. 2b and the peripheral folded portion 2c, and in the upper surface wall 2a and the curved portion 2b, the nickel layer is the outer surface of the battery and the copper layer is the inner surface of the battery (the copper layer in the peripheral folded portion 2c). In the shape of the outer can side surface).

  Then, the sealing plate 2 is subjected to chemical polishing for 60 seconds using a chemical polishing liquid prepared by adding 0.5 wt / vol of hydrogen peroxide to 10 mass% sulfuric acid, and subsequently 10 mass% concentration. The surface of the upper surface wall 2a and the curved portion 2b that is inside the battery, and the peripheral folded portion 2c are obtained by acid cleaning for 60 seconds using a pickling solution prepared by adding 0.02 wt / vol of hydrogen peroxide to sulfuric acid. A recess forming portion was provided on the entire surface on the outer can side. The number of recesses in the recess forming part after formation was 15 in a region of 100 μm × 100 μm.

  Note that the number of recesses in the recess forming portion of the sealing plate 2 is the number of recesses having a diameter of 0.5 to 5 μm observed in a 100 μm × 100 μm region of the target surface using a scanning electron microscope. And confirmed.

  Subsequently, a rust-preventing film made of benzotriazole is applied to the surface of the sealing plate 2 provided with the recess forming portion on the inner surface of the upper surface wall 2a and the curved portion 2b and on the outer can side of the peripheral folded portion 2c. Formed.

<Preparation of positive electrode mixture molding>
As a positive electrode active material, a mixture containing 95% by mass of granular silver oxide having an average particle size of 150 μm and a bulk density of 2.4 g / cm ³ and 5% by mass of graphite is pressure-molded. The molded body was pulverized and sieved to obtain a positive electrode mixture having an average particle size of 300 μm. This positive electrode mixture is filled in a mold, and pressure-molded into a disk shape having a filling density of 5.5 g / cm ³ , a diameter of 10.9 mm, and a height of 1.9 mm, thereby producing a positive electrode mixture molded body. This was impregnated with a part of the following alkaline electrolyte.

<Battery assembly>
The negative electrode used was 0.2 g of mercury-free zinc particles having a particle size of 75 μm or less in a proportion of 25% by mass or less and an average particle size of 120 μm. As the alkaline electrolyte, a 36% by mass potassium hydroxide aqueous solution in which 4% by mass of zinc oxide was dissolved was used. Furthermore, the outer can was produced using SUS430. In addition, “YG2152” from Yuasa Membrane System Co., Ltd. was used as the separator. This separator is formed by laminating a cellophane film having a thickness of 20 μm and a graft film having a thickness of 30 μm. The graft film has a structure in which a polyethylene main chain is graft copolymerized with acrylic acid. It is composed of a polymer. Further, a vinylon-rayon mixed paper having a thickness of 400 μm was used as the electrolytic solution holding layer. The separator and the electrolyte solution holding layer were used by punching into a circle having a diameter of 11.3 mm.

  Using the above positive electrode (positive electrode mixture molded body), negative electrode, alkaline electrolyte, outer can, sealing plate, separator and electrolyte holding layer, and further using an annular gasket made of nylon 66, diameter 11.5 mm, thickness 5 A 4 mm flat alkaline battery (flat silver oxide battery) was produced. In assembling the battery, the sealing plate was used after applying a pitch to the surface of the anticorrosive coating. 3 and 4, the electrolytic solution holding layer is not shown, but in the battery of Example 1, the electrolytic solution holding layer was disposed on the upper surface side (the negative electrode 4 side) of the separator 5. Furthermore, in FIG. 3 and FIG. 4, each layer of the clad material constituting the sealing plate is not shown separately.

Example 2
The pickling solution used for pickling the sealing plate 2 was changed to a solution prepared by adding 0.05 wt / vol of hydrogen peroxide to sulfuric acid having a concentration of 10% by mass, and the formation of the recessed portion was performed. A flat alkaline battery was produced in the same manner as in Example 1.

  In addition, as for the sealing board 2 used in Example 2, the number of the recessed parts in the recessed part formation location after formation was 100 pieces in the area | region of 100 micrometers x 100 micrometers.

Example 3
The pickling solution used for pickling the sealing plate 2 was changed to a solution prepared by adding 0.3 wt / vol of hydrogen peroxide to 10% strength by weight sulfuric acid, and the formation of the recessed portion was performed. A flat alkaline battery was produced in the same manner as in Example 1.

  In addition, as for the sealing board 2 used in Example 3, the number of the recessed parts in the recessed part formation location after formation was 2000 pieces in the area | region of 100 micrometers x 100 micrometers.

Example 4
A flat alkaline battery was produced in the same manner as in Example 2 except that it was used for assembling the battery without applying a pitch to the sealing plate 2.

Comparative Example 1
A flat alkaline battery was produced in the same manner as in Example 1 except that the pickling solution used for pickling the sealing plate 2 was changed to sulfuric acid having a concentration of 10% by mass to form the concave portion.

  In the sealing plate 2 used in Comparative Example 1, the number of recesses in the recess forming part after formation was 5 in a region of 100 μm × 100 μm.

Comparative Example 2
A flat alkaline battery was produced in the same manner as in Example 1 except that a sealing plate provided with a recess forming portion was used by applying a pitch without providing a rust preventive coating in the same manner as in Example 2.

  Evaluation of leakage resistance by investigating whether or not there was leakage of alkaline electrolyte after storing 1000 pieces of each of flat alkaline batteries of Examples and Comparative Examples in an atmosphere of 60 ° C. and 90% relative humidity for 90 days did.

  Table 1 shows the evaluation results and the structure of the sealing plate used for each battery.

  As shown in Table 1, the flat alkaline batteries of Examples 1 to 4 using a sealing plate in which a rust-proof coating was formed after providing a specific recess formation location on a specific surface had insufficient recess formation. Compared to the battery of Comparative Example 1 using a sealing plate and the battery of Comparative Example 2 using a sealing plate not formed with a rust preventive coating, the number of leaked alkaline electrolytes is small, and good liquid leakage resistance Had. That is, it can be said that the flat alkaline batteries of Examples 1 to 4 had a good productivity because the number of alkaline electrolytes leaked out was extremely small among the many produced.

DESCRIPTION OF SYMBOLS 1 Exterior can 2 Sealing plate 2a Upper surface wall 2b Curved part 2c Peripheral turning part 3 Positive electrode (molded body of positive electrode mixture)
4 Negative electrode 5 Separator 6 Resin gasket

Claims (3)

In a sealed space formed by fitting a sealing plate to the opening of the outer can via a resin gasket and tightening the opening end of the outer can inwardly, a molded body of the positive electrode mixture A flat alkaline battery having a positive electrode comprising, a negative electrode containing zinc particles or zinc alloy particles, a separator and an alkaline electrolyte,
The sealing plate has an upper surface wall, a curved portion curved downward from the upper surface wall, and a peripheral folded portion,
On the battery inner surface of the curved portion and the outer can side surface of the peripheral folded portion, there are locations having 10 or more recesses having a diameter of 0.5 to 5 μm in a region of 100 μm × 100 μm. And a rust-proof coating containing a triazole compound is formed on the inner surface of the curved portion and the outer can side of the peripheral folded portion. .   2. The flat alkaline battery according to claim 1, wherein a surface roughness of the anticorrosive coating formed on the inner surface of the curved portion and the outer can side of the peripheral folded portion is 5 to 50 μm.   The flat alkaline battery according to claim 1 or 2, wherein a pitch is applied to a surface of the sealing plate where the concave portion is present.

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