Button-type battery

Abstract

Provided is a button-type battery comprising a battery container having an outer can, a sealing can, and a gasket made of resin, the battery favorably suppressing the intrusion of moisture into the battery from the outside.　This button-type battery is characterized by comprising a battery container having: an outer can and a sealing can; and a gasket made of resin interposed between the outer can and the sealing can. The battery is also characterized in that a resin coating layer is formed on the surface of the gasket which is exposed to the outside, and in that the resin coating layer contains an epoxy resin and a plate-shaped filler. The resin coating layer preferably has a thickness of 50 μm or more.

Description

Button cell battery

[0001] The present invention relates to a button battery that includes a battery container having an outer can, a sealing can, and a resin gasket, and that can effectively prevent moisture from entering the battery from the outside.

[0002] In electrochemical cells such as button-type (coin-type) lithium secondary batteries and electric double layer capacitors having a battery container structured such that a resin gasket is sandwiched between an outer can housing power generating elements such as a positive electrode and a negative electrode and a sealing can, and the battery container is sealed, moisture is likely to penetrate from the outside to the inside of the battery container through an exposed portion of the gasket that forms part of the outer surface of the battery container, and there is a risk that the performance will not be maintained over a long period of time due to the influence of this moisture. For this reason, for example, Patent Document 1 attempts to solve this problem by providing an electrochemical cell in which a first resin that has low viscosity and good fluidity in liquid form is filled into the space formed by the positive electrode can, the negative electrode can (the outer can and the sealing can), and the gasket, and a second resin is further filled on top of the first resin.

[0003] JP 2007-35829 A

[0004] On the other hand, in alkaline batteries using alkaline electrolyte, gaskets are made of nylon resin, which has excellent alkali resistance but high water permeability, so even though the battery contains an aqueous electrolyte, leakage of the electrolyte to the outside due to water penetration into the battery can be a problem. For this reason, there is a need to develop a technology that can effectively prevent water from penetrating into the battery through the gasket.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a button battery that includes a battery container having an outer can, a sealing can, and a resin gasket, and that can effectively prevent moisture from entering the battery from the outside.

[0006] The button battery of the present invention comprises a battery container having an outer can, a sealing can, and a resin gasket interposed between the outer can and the sealing can, and is characterized in that a resin coating layer is formed on the exposed surface of the gasket, and the resin coating layer contains an epoxy resin and a plate-like filler.

[0007] In the battery industry, flat batteries with a diameter greater than their height are called button batteries or coin batteries, but there is no clear difference between these button batteries and coin batteries, and the button battery of the present invention does not exclude those called coin batteries, and such batteries called coin batteries are also included in the scope of the button battery of the present invention.

[0008] According to the present invention, it is possible to provide a button battery that includes a battery container having an outer can, a sealing can, and a resin gasket, and that can effectively prevent moisture from entering the inside from the outside.

[0009] 1 is a cross-sectional view schematically illustrating an example of a button battery of the present invention.

[0010] Fig. 1 is a cross-sectional view showing a schematic diagram of an example of a button battery of the present invention. The button battery 1 shown in Fig. 1 includes a battery container having an outer can 2, a sealing can 3, and a resin gasket 7 interposed between the outer can 2 and the sealing can 3. A positive electrode 4 and a negative electrode 5 are stacked with a separator 6 interposed therebetween and sealed together with an electrolyte (not shown). In the battery container of the button battery 1, the sealing can 3 is fitted into the opening of the outer can 2 via an annular gasket 7 with an L-shaped cross section. The open end of the outer can 2 is tightened inward, and the gasket 7 abuts against the sealing can 3, sealing the opening of the outer can 2 and forming a sealed structure.

[0011] 1, the gasket 7 interposed between the outer can 2 and the sealing can 3 has a portion (exposed surface) that is exposed to the outside of the battery container without contacting either the outer can 2 or the sealing can 3. In the button battery 1, there is a risk that external moisture may enter the battery container through the exposed surface of the gasket 7.

[0012] Therefore, in the button battery of the present invention, as shown in Figure 1, a resin coating layer 8 containing an epoxy resin and a plate-like filler is formed on the exposed surface of the gasket 7. A resin coating layer having this configuration is less permeable to moisture, and therefore can effectively prevent moisture from penetrating into the button battery from the outside. Therefore, with the button battery of the present invention, even if the battery contains an electrolyte solution consisting of, for example, an aqueous solution, it is possible to prevent leakage of the electrolyte solution due to moisture penetration from the outside.

[0013] Furthermore, when the external environment of the battery is low in humidity, moisture may escape from the inside of the battery to the outside through the gasket, resulting in a decrease in the electrolyte and a resulting decrease in battery capacity. However, in the button battery of the present invention, the resin coating layer formed on the exposed surface of the gasket acts to prevent moisture from escaping from the inside of the battery to the outside, thereby preventing a decrease in capacity due to this.

[0014] Generally, epoxy resins are curable resins that are cured by the action of heat, light, moisture in the air, etc. The epoxy resins contained in the resin coating layer include not only such curable resins (resins before curing) but also those that have been cured (cured epoxy resins). Usually, the epoxy resins contained in the resin coating layer are cured epoxy resins.

[0015] Examples of epoxy resins for forming the resin coating layer include bisphenol A type epoxy resins, bisphenol E type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, hydrogenated bisphenol A type epoxy resins, alicyclic type epoxy resins, glycidylamine type epoxy resins, and modified epoxy resins (acrylic modified epoxy resins, polybutadiene type modified epoxy resins, graft modified epoxy resins, silylated polyepoxy resins, etc.).

[0016] In order to increase the strength, rigidity, and resistance to moisture and heat of the epoxy resin, a silane coupling agent such as 3-glycidyloxypropyltrimethoxysilane may be added.

[0017] Examples of the platy filler contained in the resin coating layer include platy talc, mica, clay, and silicate compounds.

[0018] The average particle diameter of the plate-like filler is preferably 0.5 μm or more, since this makes it easier for the plate-like filler to be uniformly dispersed in the composition for forming a resin coating layer and makes it easier for the plate-like filler to exert its effects. If the average particle diameter of the plate-like filler is too large, large gaps (areas consisting only of epoxy resin) will exist between particles in the formed resin coating layer, reducing the moisture penetration inhibitory effect. Therefore, from the viewpoint of further enhancing the moisture penetration inhibitory effect of the resin coating layer, the average particle diameter of the plate-like filler is preferably 5 μm or less. The average particle diameter of the plate-like filler referred to here is determined by the D ５０ (The value of 50% diameter in the volume-based integrated fraction when calculating the integrated volume from particles with small particle sizes).

[0019] Furthermore, the aspect ratio of the plate-like filler is preferably 1.3 or more, more preferably 1.5 or more, and even more preferably 2 or more, because this makes it easier for the plate-like filler to be dispersed in a resin containing an epoxy resin and a plate-like filler with the filler oriented in the same direction. Furthermore, from the viewpoint of improving the processability of the resin containing an epoxy resin and a plate-like filler, the aspect ratio of the plate-like filler is preferably 25 or less, more preferably 20 or less. The aspect ratio of the plate-like filler referred to here means the ratio of the length of the longest part (major axis length) in the filler to the thickness of the filler (major axis length / thickness). Specifically, a transmission electron microscope photograph of the filler at 10,000x magnification is taken, the major axis length and thickness of 30 fillers are measured, the average major axis length and the average thickness are calculated, and the value is calculated as the ratio of these average values.

[0020] In the resin coating layer, when the content of the epoxy resin is 100 parts by mass, the content of the plate-like filler is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and is preferably 40 parts by mass or less, more preferably 30 parts by mass or less.

[0021] From the viewpoint of better suppressing the penetration of external moisture into the battery container, the resin coating layer preferably has a thickness of 50 μm or more, more preferably 75 μm or more, as measured by the method shown in the Examples below. There is no particular upper limit to the thickness of the resin coating layer, but since the effect saturates if the resin coating layer is too thick, it is usually 300 μm or less.

[0022] The resin coating layer can be formed by applying a resin coating layer-forming composition containing an epoxy resin (epoxy resin before curing), a plate-like filler, and, if necessary, an initiator and a solvent to a predetermined location on the gasket, and then applying energy (light, heat, etc.) appropriate for the initiator to cure the epoxy resin.

[0023] As the initiator, various known initiators used for curing epoxy resins (peroxide-based initiators, carboxylic acid-based initiators, benzophenone-based initiators, boron salt-based initiators, phosphorus-based initiators, triazine-based initiators, sulfonate-based initiators, imidazole-based initiators, etc.) can be used. In particular, as a photoinitiator for photocuring epoxy resins, PF ６ － , SbF ６ － , (Rf) ｎ PF ６－ｎ － [Rf is a perfluoroalkyl group and n is 1 to 6], (C ６ F ５ ) ４ － It is preferred to use sulfonium salts such as diphenyl(4-phenylthiophenyl)sulfonium antimony hexafluoride salts and iodonium salts, including the following:

[0024] The amount of initiator in the composition for forming a resin coating layer can be an amount suitable for curing the amount of epoxy resin contained in the composition. For example, in the case of the photoinitiator, the content in the composition for forming a resin coating layer is preferably 0.5% by mass or more, more preferably 1% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less.

[0025] Furthermore, the resin coating layer-forming composition may contain, as needed, a curing accelerator, a coupling agent, an antifoaming agent, a compatibilizer, a resin other than the epoxy resin, and the like.

[0026] The resin coating layer-forming composition may be a commercially available product such as "Moresco Moisture Cut" (product name) manufactured by MORESCO Corp. For example, WB90US is a UV-curable epoxy resin composition containing 70 to 90% by mass of epoxy resin and 5 to 20% by mass of plate-like filler.

[0027] The method and conditions for curing the epoxy resin after applying the composition for forming the resin coating layer onto the exposed surface of the gasket may be appropriately selected from methods and conditions commonly used for curing epoxy resins.

[0028] The resin coating layer has a water vapor permeability of 5 g / m ２ 24 hours or less (test environment: 40°C, relative humidity 90%, resin layer thickness: 100 μm). It is desirable that the resin coating layer does not transmit water vapor as much as possible, that is, its water vapor permeability is preferably as low as possible, and is 0 g / m ２ ・It may be 24 hours.

[0029] The water vapor permeability of the resin coating layer referred to in this specification is a value measured in accordance with Japanese Industrial Standards (JIS) Z 0208 method (cup method) for a film obtained by applying a composition for forming a resin coating layer onto a substrate such as a resin film, curing the epoxy resin, and then peeling the film from the substrate.

[0030] The button battery of the present invention can be, for example, an alkaline battery (alkaline primary battery, alkaline secondary battery) that uses an aqueous solution such as an alkaline electrolyte as the electrolyte (alkaline electrolyte).

[0031] For the positive electrode of the button battery, a positive electrode mixture compact obtained by molding a positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder into a pellet shape, or a structure having a positive electrode mixture layer formed from the positive electrode mixture on one or both sides of a current collector can be used.

[0032] Examples of the positive electrode active material include silver oxide (silver (I) oxide, silver (II) oxide, etc.); silver-containing composite oxides [composite oxides of silver and cobalt, nickel, bismuth, etc. (silver-nickel composite oxide, silver-nickel-cobalt composite oxide, etc.)]; manganese dioxide; and nickel oxyhydroxide.

[0033] When silver oxide is used as the positive electrode active material, it is preferable that the silver oxide be in a granular form. Silver oxide is usually supplied in the form of a fine powder with a particle size of 0.1 to 5 μm, but when this silver oxide is granulated and used in the form of granules, the resistance is lower than when used in the form of a fine powder, and therefore the load characteristics of the battery can be further improved.

[0034] When silver oxide is used in the form of a fine powder, a larger amount of conductive additive must be added to reduce resistance. However, because the carbon material preferably used as a conductive additive has a low bulk density, adding too much of it makes it difficult to increase the loading of the silver oxide active material. In contrast, using granular silver oxide improves weighability and reduces variation, and also improves packability and formability when pressure-molded. This reduces resistance and stabilizes the individual characteristics of multiple positive electrodes (and thus button batteries) when manufactured. Furthermore, the amount of carbon material used as a conductive additive can be reduced, allowing for an increased loading of silver oxide.

[0035] Furthermore, for example, silver (I) oxide reacts with the carbon material as shown in the following formula and is reduced, resulting in a decrease in discharge performance: ２ O+C→4Ag+CO ２

[0036] However, by granulating the silver oxide, the reaction is suppressed and the amount of carbon material added can be reduced as described above, which further suppresses the reduction reaction of silver oxide and improves discharge characteristics (especially low-temperature heavy-load characteristics).

[0037] When granular silver oxide is used as the positive electrode active material, its particle size is preferably 50 μm or more, more preferably 75 μm or more, and preferably 500 μm or less, more preferably 300 μm or less, and its bulk density is preferably 1.5 g / cm ３ More preferably, 1.8 g / cm ３ or more, preferably 3.5 g / cm ３ or less, more preferably 2.6 g / cm ３ The following is a summary of the results. Silver oxide in this form has better fluidity than powdered silver oxide, and as described above, it has improved weighability and moldability, reduced resistance, and improved reactivity, resulting in better load characteristics. Furthermore, the individual characteristics of the manufactured positive electrode (and therefore flat battery) are more stable. The particle size of the granular silver oxide referred to here is the number-average particle size calculated by measuring the number of particles n and the diameter d of each particle by laser light scattering using a Honeywell Microtrac particle size distribution analyzer "9320-X100." The bulk density of the granular silver oxide referred to here is the value determined by placing a predetermined amount of granular silver oxide in a container and using a bulk density measuring device in accordance with the bulk density measurement method specified in JIS R 1628.

[0038] Examples of the conductive additive for the positive electrode mixture that can be used include carbon materials such as acetylene black; ketjen black; carbon blacks such as channel black, furnace black, lamp black, and thermal black; and carbon fibers; as well as conductive fibers such as metal fibers; carbon fluoride; metal powders such as copper and nickel; and organic conductive materials such as polyphenylene derivatives.

[0039] Examples of binders for the positive electrode mixture include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and polyvinylpyrrolidone (PVP).

[0040] In the case of a positive electrode mixture molded body, the positive electrode can be produced by, for example, mixing a positive electrode active material, a conductive additive, a binder, and, if necessary, an electrolyte (electrolytic solution), etc., to prepare a positive electrode mixture, and then press-molding the mixture into a predetermined shape.

[0041] Furthermore, in the case of a positive electrode having a positive electrode mixture layer and a current collector, for example, a positive electrode active material, a conductive additive, a binder, and the like are dispersed in water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture-containing composition (slurry, paste, etc.) (the binder may be dissolved in the solvent), which is then applied to a current collector, dried, and, if necessary, subjected to a pressing treatment such as a calendaring treatment, thereby producing the positive electrode.

[0042] However, the positive electrode is not limited to those produced by the above methods, and may be produced by other methods.

[0043] As for the composition of the positive electrode mixture for the positive electrode, the amount of the positive electrode active material is preferably 80 to 98 mass %, the content of the conductive additive is preferably 1.5 to 10 mass %, and the content of the binder is preferably 0.5 to 10 mass %.

[0044] In the case of a positive electrode mixture molded body, the thickness thereof is preferably 0.15 to 4 mm. On the other hand, in the case of a positive electrode having a positive electrode mixture layer and a current collector, the thickness of the positive electrode mixture layer (thickness per surface of the current collector) is preferably 30 to 300 μm.

[0045] When a current collector is used for the positive electrode, examples of the current collector include those made of stainless steel such as SUS316, SUS430, and SUS444; aluminum; and aluminum alloys. Examples of the current collector include plain woven wire mesh, expanded metal, lath mesh, punched metal, metal foam, and foil (plate). The thickness of the current collector is preferably, for example, 0.05 to 0.2 mm. It is also desirable to apply a paste-like conductive material such as carbon paste or silver paste to the surface of such a current collector.

[0046] The negative electrode uses, for example, zinc particles, i.e., particles composed of pure zinc (including unavoidable impurities) or zinc alloys. In such negative electrodes, the zinc in the particles acts as the active material. Examples of alloy components of zinc alloy particles include indium, bismuth, and aluminum (the remainder being zinc and unavoidable impurities). The zinc particles in the negative electrode may be composed of only one type of particle with a single composition, or may contain two or more types of particles with different compositions.

[0047] However, it is preferable to use zinc particles that do not contain mercury as an alloying component. Batteries using such zinc particles can reduce environmental pollution caused by battery disposal. Also, for the same reason as in the case of mercury, it is preferable to use zinc particles that do not contain lead as an alloying component.

[0048] Regarding the particle size of the zinc particles, for example, the proportion of particles having a particle size of 75 μm or less in the total powder is preferably 50 mass % or less, more preferably 30 mass % or less, and the proportion of particles having a particle size of 100 to 200 μm is 50 mass % or more, more preferably 90 mass % or more. The particle size of the zinc particles referred to here is the 50% diameter value (D ) in the volume-based integrated fraction when determining the integrated volume from particles of small particle size, which is determined using a measuring device similar to that used in the above-mentioned method for measuring the average particle size of granular silver oxide. ５０ )

[0049] The negative electrode may contain, for example, a gelling agent (sodium polyacrylate, carboxymethyl cellulose, etc.) added as needed in addition to the zinc particles, and an alkaline electrolyte may be added to the gelling agent to form a negative electrode agent (gelled negative electrode). The amount of the gelling agent in the negative electrode is preferably, for example, 0.5 to 1.5 mass %.

[0050] The negative electrode can also be a non-gelled negative electrode that is substantially free of the gelling agent described above. (Note that a non-gelled negative electrode may contain a gelling agent as long as it does not thicken the alkaline electrolyte present near the zinc particles. Therefore, "substantially free of a gelling agent" means that the gelling agent may be present to an extent that does not affect the viscosity of the alkaline electrolyte.) In the case of a gelled negative electrode, the alkaline electrolyte is present near the zinc particles together with the gelling agent, but the action of the gelling agent thickens the alkaline electrolyte, suppressing the movement of the alkaline electrolyte and, in turn, the movement of ions in the electrolyte. This is thought to suppress the reaction rate at the negative electrode, which inhibits the improvement of the load characteristics (especially heavy load characteristics) of the battery. In contrast, by making the negative electrode non-gelled and maintaining a high ion migration rate in the alkaline electrolyte without increasing the viscosity of the alkaline electrolyte present near the zinc particles, the reaction rate at the negative electrode can be increased, thereby further improving the load characteristics (especially heavy load characteristics).

[0051] The alkaline electrolyte contained in the negative electrode can be the same as that injected into the battery.

[0052] The content of zinc particles in the negative electrode is, for example, preferably 60% by mass or more, more preferably 65% ​​by mass or more, and preferably 75% by mass or less, more preferably 70% by mass or less.

[0053] The negative electrode preferably contains an indium compound, which can more effectively prevent gas generation due to the corrosion reaction between zinc particles and the alkaline electrolyte.

[0054] Examples of the indium compound include indium oxide and indium hydroxide.

[0055] The amount of the indium compound used in the negative electrode is preferably 0.003 to 1 in terms of mass ratio to 100 zinc particles.

[0056] The alkaline electrolyte used in the button battery is preferably an aqueous solution (alkaline electrolyte) of one or more alkali metal hydroxides (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.). Potassium hydroxide is particularly preferred from the viewpoint of obtaining an electrolyte with high conductivity, and sodium hydroxide is particularly preferred from the viewpoint of further improving the leak resistance of the button battery. Regarding the concentration of the alkaline electrolyte, for example, the concentration of potassium hydroxide in the aqueous potassium hydroxide solution is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less. Furthermore, the concentration of sodium hydroxide in the aqueous sodium hydroxide solution is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably 35% by mass or less, and more preferably 30% by mass or less. By adjusting the concentration of the aqueous potassium hydroxide or sodium hydroxide solution to such values, an alkaline electrolyte with excellent conductivity can be obtained.

[0057] Furthermore, a gel electrolyte obtained by adding a known gelling agent (sodium polyacrylate, carboxymethyl cellulose, etc.) to the alkaline electrolyte solution described above can also be used as the alkaline electrolyte in the battery.

[0058] In addition to the above components, various known additives may be added to the alkaline electrolyte as needed, as long as the effects of the present invention are not impaired. For example, zinc oxide may be added to prevent corrosion (oxidation) of zinc particles used in the negative electrode of a button battery. Zinc oxide may also be added to the negative electrode.

[0059] In addition, when the button battery is a secondary battery, the alkaline electrolyte used as the alkaline electrolyte may contain one or more compounds selected from the group consisting of manganese compounds, tin compounds, and indium compounds dissolved therein.

[0060] When an alkaline secondary battery having a positive electrode containing silver oxide as the positive electrode active material is discharged, silver is produced from the silver oxide in the positive electrode. However, when the battery is charged, silver oxide crystals form around the silver, which effectively reduces the reaction area of ​​the positive electrode active material and inhibits subsequent battery reactions. However, when these compounds are dissolved in the alkaline electrolyte, ions derived from these compounds (manganese ions, tin ions, indium ions) adsorb to the positive electrode, suppressing the crystal growth of silver oxide and reducing the size of the silver oxide crystals that form. Therefore, the problem of silver oxide crystals produced during battery charging inhibiting battery reactions is suppressed, which can further improve the charge / discharge cycle characteristics of the secondary battery, for example.

[0061] Examples of manganese compounds dissolved in alkaline electrolytes include manganese chloride, manganese acetate, manganese sulfide, manganese sulfate, and manganese hydroxide. Examples of tin compounds dissolved in alkaline electrolytes include tin chloride, tin acetate, tin sulfide, tin bromide, tin oxide, tin hydroxide, and tin sulfate. Examples of indium compounds dissolved in alkaline electrolytes include indium hydroxide, indium oxide, indium sulfate, indium sulfide, indium nitrate, indium bromide, and indium chloride.

[0062] From the viewpoint of better ensuring the above-mentioned effects, the concentrations of the indium compound, manganese compound, and tin compound in the alkaline electrolyte (when only one of them is dissolved, this refers to the concentration of that compound, and when two or more of them are dissolved, this refers to the total concentration of those compounds) are preferably 50 ppm or more, and more preferably 500 ppm or more, by mass, and are preferably 10,000 ppm or less, and more preferably 5,000 ppm or less.

[0063] In button batteries, a separator is interposed between the positive electrode and the negative electrode. Separators that can be used in button batteries include nonwoven fabrics primarily made of vinylon and rayon, vinylon-rayon nonwoven fabrics (vinylon-rayon mixed paper), polyamide nonwoven fabrics, polyolefin-rayon nonwoven fabrics, vinylon paper, vinylon-linter pulp paper, and vinylon-mercerized pulp paper. Alternatively, the separator may be a laminate of a hydrophilically treated microporous polyolefin film (such as a microporous polyethylene film or a microporous polypropylene film), a cellophane film, and a liquid-absorbing layer (electrolyte retention layer) such as vinylon-rayon mixed paper. The thickness of the separator is preferably 20 to 500 μm.

[0064] Furthermore, when the button battery is a secondary battery, it is preferable to dispose an anion conductive membrane between the positive electrode and the negative electrode, which has a polymer matrix and has dispersed therein particles of at least one metal compound selected from the group consisting of metal oxides, hydroxides, carbonates, sulfates, phosphates, borates, and silicates.

[0065] Furthermore, it is preferable that the button battery contains a polyalkylene glycol or a calcium compound in at least one of the negative electrode, alkaline electrolyte (alkaline electrolyte solution), and separator. In this case, the action of the polyalkylene glycol or calcium compound can suppress the growth of zinc dendrites in the negative electrode, thereby further improving the charge / discharge cycle characteristics (in the case of a secondary battery) and storage characteristics of the button battery.

[0066] The polyalkylene glycols are compounds having a structure in which alkylene glycols such as ethylene glycol, propylene glycol, and butylene glycol are polymerized or copolymerized, and may have a crosslinked or branched structure, or may be compounds having a structure in which the terminals are substituted, and compounds having a weight-average molecular weight of about 200 or more are preferably used. There is no particular upper limit to the weight-average molecular weight, but in order to more easily exert the effect of the addition, it is preferable that the compound is water-soluble, and usually those having a weight-average molecular weight of 20,000 or less are preferably used, and those having a weight-average molecular weight of 5,000 or less are more preferably used.

[0067] More specifically, polyethylene glycols (polyethylene glycol, polyethylene oxide, etc.) having a structure in which ethylene glycol is polymerized, and polypropylene glycols (polypropylene glycol, polypropylene oxide, etc.) having a structure in which propylene glycol is polymerized are preferably used, and copolymer compounds containing an ethylene oxide unit and a propylene oxide unit (polyoxyethylene polyoxypropylene glycol, etc.) may also be used.

[0068] When polyalkylene glycols are used, the amount thereof is preferably 0.01 to 1.5 parts by mass relative to 100 parts by mass of zinc particles.

[0069] The calcium compounds include Zn(OH) produced during discharge, such as calcium hydroxide, calcium oxide, calcium chloride, and calcium sulfate. ４ ２－ It reacts with CaZn(OH) ４ Examples include compounds that generate complex compounds such as those mentioned above, and the complex compounds themselves, and calcium hydroxide and calcium oxide are preferably used.

[0070] When a calcium compound is used, the amount thereof is preferably 5 to 40 parts by mass relative to 100 parts by mass of zinc particles.

[0071] The outer can of the button battery can be made of, for example, nickel-plated iron or stainless steel.

[0072] Furthermore, the sealing plate of a button battery can be made of, for example, nickel-plated iron or stainless steel. When zinc particles, which are the negative electrode active material, are in direct contact with the inner surface of the sealing plate, it is preferable to form a metal layer made of copper or a copper alloy such as brass on the surface of the sealing plate that comes into contact with the negative electrode, and it is even more preferable to form a tin layer on the surface of the metal layer. The reason for forming a metal layer made of copper or a copper alloy on the surface of the sealing plate that comes into contact with the negative electrode is to suppress the formation of a local battery with the zinc and prevent corrosion of the zinc, and by forming a tin layer on the surface of the metal layer, the corrosion prevention effect can be further enhanced.

[0073] Gaskets for button batteries are made of materials such as nylon and polypropylene.

[0074] The shape of the button battery in plan view may be circular or polygonal, such as quadrilateral (square or rectangle), and in the case of a polygonal shape, the corners may be curved.

[0075] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0076] Example 1 A mixture containing 95% by mass of silver (I) oxide (positive electrode active material) granulated to an average particle size of 150 μm and 5% by mass of graphite (conductive additive) was filled into a mold and pressure-molded into a disk having a diameter of 8.9 mm and a height of 0.75 mm to prepare a positive electrode mixture compact, which was then impregnated with a portion of the following electrolytic solution.

[0077] The negative electrode was made of a zinc alloy (mercury-free zinc alloy) containing 1000 ppm Al, 100 ppm Bi, 500 ppm In, and 5 ppm Mg. The zinc alloy powder had a mean particle size of 120 μm and a particle size of 75 μm or less (measured by the above-mentioned method) of 25% by mass.

[0078] Furthermore, an aqueous solution of potassium hydroxide with a concentration of 36 mass % in which 4 mass % of zinc oxide and 1000 ppm of indium hydroxide were dissolved was used as the electrolyte.

[0079] The separator was made of a multilayer film in which two graft films (thickness: 30 μm) made of a graft copolymer having a structure in which acrylic acid was graft copolymerized onto a polyethylene main chain were placed on both sides of a cellophane film (thickness: 20 μm), and vinylon-rayon mixed paper (thickness: 100 μm) was laminated on top of this, and the laminate was punched out into a circle with a diameter of 9.2 mm.

[0080] The positive electrode (positive electrode mixture molded body), negative electrode, alkaline electrolyte, and separator were sealed in a battery container composed of an outer can made of a steel plate with a gold-plated inner surface, a sealing plate made of a copper-stainless steel (SUS304)-nickel clad plate, and an annular gasket made of nylon 66.

[0081] Next, a resin coating layer-forming composition ("Moresco Moisture Cut WB90US(P)" (product name) manufactured by MORESCO Corporation) was applied to the exposed surface of the gasket in the battery container, and the accumulated light intensity was 6 J / cm ２ The epoxy resin was cured by irradiating it with ultraviolet light under the conditions of: and then heating it at 80°C for 1 hour to form a resin coating layer, thereby obtaining a button-type alkaline primary battery having a diameter of 9.5 mm and a thickness of 2.7 mm and having a structure similar to that shown in Figure 1.

[0082] One of the produced alkaline primary button batteries was cut to obtain a cross section identical to the cross section shown in Figure 1. The resin coating layer provided on the gasket of this cross section was observed using a microscope at a magnification of 100x, and the thickness was measured at five random points using the microscope's scale. The average value of these measurements was taken as the thickness of the resin coating layer. The thickness of the resin coating layer obtained was 75 µm.

[0083] Comparative Example 1 A button-type alkaline primary battery was fabricated in the same manner as in Example 1, except that no resin coating layer was formed on the exposed surface of the gasket.

[0084] Comparative Example 2 A button-type alkaline primary battery was fabricated in the same manner as in Example 1, except that a commercially available fluorine-based coating agent was applied to the exposed surface of the gasket and dried to form a resin coating layer.

[0085] Five button-type alkaline primary batteries from each of Example 1, Comparative Example 1, and Comparative Example 2 were stored in an atmosphere of 60°C and 90% relative humidity, and the number of days until leakage was visually observed was measured. The average number of days measured for each battery was calculated, and the results are shown in Table 1.

[0086]

[0087] As shown in Table 1, the button-type alkaline primary battery of Example 1, in which a resin coating layer containing an epoxy resin (cured product) and a plate-like filler was formed on the exposed surface of the gasket, was able to effectively prevent external moisture from penetrating into the battery container due to the resin coating layer, and therefore, compared with the battery of Comparative Example 1, which did not have the resin coating layer, and the battery of Comparative Example 2, in which the resin coating layer was made of a fluorine-based resin, the number of days until leakage occurred was longer, and the battery exhibited excellent leakage resistance.

[0088] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0089] The button battery of the present invention can be used in the same applications as various known batteries (such as alkaline primary batteries and alkaline secondary batteries).

[0090] The button battery of the present invention can contribute to the achievement of Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all), Goal 11 (Make cities and human settlements inclusive, safe, resilient and sustainable), and Goal 12 (Ensure sustainable consumption and production patterns) out of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

[0091] REFERENCE SIGNS LIST 1 Button battery 2 Outer can 3 Sealing can 4 Positive electrode 5 Negative electrode 6 Separator 7 Gasket 8 Resin coating layer

Claims

1. A button battery comprising a battery container having an outer can, a sealing can, and a resin gasket interposed between the outer can and the sealing can, wherein a resin coating layer is formed on the exposed surface of the gasket, and the resin coating layer contains an epoxy resin and a plate-like filler.

2. The button battery according to claim 1, wherein the thickness of the resin coating layer is 50 μm or more.

Images