Button-shaped battery

Abstract

Provided is a button-shaped battery which is provided with a battery container including an exterior can, a sealing can, and a resin gasket, and which is capable of favorably suppressing the intrusion of moisture from the outside to the inside.　A button-shaped battery according to the present invention is characterized by being provided with a battery container including 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 surface of the gasket that is exposed to the outside, and the resin coating layer contains an epoxy resin having a glass transition temperature of -20°C or less. The thickness of the resin coating layer is preferably 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, wherein a resin coating layer is formed on the exposed surface of the gasket, and the resin coating layer contains an epoxy resin having a glass transition temperature of −20° C. or lower.

[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 FIG. 1 , a resin coating layer 8 containing an epoxy resin having a glass transition temperature (Tg) of −20°C or lower is formed on the exposed surface of the gasket 7. A resin coating layer with this configuration is less susceptible to moisture permeation. Furthermore, even when the gasket expands and contracts due to charging and discharging the battery, the epoxy resin with a low Tg contained in the resin coating layer can deform in response to the volumetric changes, thereby effectively maintaining the moisture-blocking function of the resin coating layer. In the button battery of the present invention, these effects of the resin coating layer effectively prevent moisture from penetrating into the battery container from the outside. Therefore, the button battery of the present invention can prevent electrolyte leakage due to moisture penetration from the outside, even when the battery contains an electrolyte consisting of, for example, an aqueous solution.

[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 such curable resins (resins before curing) as well as those obtained after curing (cured epoxy resin products), and the Tg of the epoxy resin contained in the resin coating layer is the value of the product obtained after curing (cured epoxy resin product).

[0015] The Tg of the epoxy resin contained in the resin coating layer is −20° C. or lower, and preferably −40° C. or lower, from the viewpoint of ensuring that the resin coating layer can deform well in response to volumetric changes in the gasket. There is no particular restriction on the lower limit of the Tg of the epoxy resin contained in the resin coating layer, but it is usually −80° C. or higher.

[0016] The Tg of the epoxy resin referred to in this specification is a value measured in accordance with the provisions of Japanese Industrial Standards (JIS) K 7121.

[0017] An example of an epoxy resin having a Tg of −20° C. or less is a cured product of a curable composition containing modified silicone, an epoxy resin, and an amine.

[0018] Examples of modified silicones in the composition include copolymers having a reactive Si-containing functional group and having structural units derived from alkyl acrylate esters and / or alkyl methacrylate esters whose molecular chains have an alkyl group containing 1 to 8 carbon atoms, and structural units derived from alkyl acrylate esters and / or alkyl methacrylate esters whose molecular chains have an alkyl group containing 10 or more carbon atoms; oxyalkylene polymers having a reactive Si-containing functional group; etc. Here, the reactive Si-containing functional group is a Si-containing functional group that can form a crosslinked structure by forming a siloxane bond, and examples include those represented by the following formula (1):

[0019]

[0020] In the formula (1), R is an organic triorganosiloxy group having 1 to 20 carbon atoms, some of the hydrogen atoms of which may be substituted; X is a hydroxyl group or a hydrolyzable group; and n is 1 or 2.

[0021] Examples of the epoxy resin in the composition include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD ​​type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, glycidyl ester type epoxy resins, urethane-modified epoxy resins, nitrogen-containing epoxy resins, epoxy resins derived from alcohols, rubber-modified epoxy resins (such as those derived from polybutadiene, nitrile butadiene rubber, and carboxyl-terminated nitrile butadiene rubber), flame-retardant epoxy resins (such as those containing bromine), and alicyclic epoxy resins.

[0022] As the amine in the composition, various amines such as primary amines, secondary amines, tertiary amines and polyamidoamines can be used, as well as amines that decompose in the presence of water to produce amines, such as ketimines and enamines.

[0023] If necessary, various components such as a diluent, a filler, an adhesion promoter, a curing catalyst, a thixotropic agent, a stabilizer, a moisture absorbent, and a foaming agent may be added to the composition.

[0024] As such a curable composition, commercially available products include two-component adhesives (such as "EP001K" manufactured by Cemedine Co., Ltd.) which consist of a base agent containing an epoxy resin and a curing agent containing a modified silicone, and which are mixed together when used, and these can be used.

[0025] 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.

[0026] The resin coating layer can be formed, for example, by applying the curable composition to a predetermined location on the gasket and leaving it for a predetermined time in a moisture-containing environment (e.g., in normal air), thereby producing an epoxy resin (cured epoxy resin) having the above-mentioned Tg.

[0027] For example, when forming a resin coating layer using the above-mentioned two-component adhesive (an adhesive consisting of a base agent containing an epoxy resin and a curing agent containing modified silicone), the base agent and curing agent are mixed and applied to a predetermined location on the gasket, and then the standing conditions for curing can be a temperature of 23 to 30°C and a time of 30 to 90 minutes.

[0028] The resin coating layer has a water vapor permeability of 50 g / m ２24 hours or less (test environment: 85°C, relative humidity 85%, resin layer thickness: 1.0 mm). 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 preferably 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 JIS Z 0208 method (cup method) for a film obtained by applying a curable composition for forming the 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 ３The 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 Silver oxide (Ag) having an average particle size of 1.4 μm and containing 3.7% (by mass) of Bi relative to the total amount of silver ２ O) particles and carbon black particles (BET specific surface area 68 m ２ / g and acetylene black having an average primary particle size of 35 nm) in a mass ratio of 98:2 to prepare a mixture.

[0077] Furthermore, the mixture, graphite particles (BET specific surface area: 20 m ２ / g, average particle size: 3.7 μm) and TiO ２ The positive electrode mixture was prepared by mixing the particles (average particle diameter: 250 nm) in proportions of 95.2 mass%, 3.8 mass%, and 1 mass%, respectively, and 300 mg of this positive electrode mixture was filled into a mold to a filling density of 5.7 g / cm.３ The mixture was pressure-molded into a disk shape having a diameter of 10.7 mm and a height of 0.6 mm, thereby producing a positive electrode mixture molded body.

[0078] The negative electrode active material used was mercury-free zinc alloy particles commonly used in alkaline primary batteries, containing 500 ppm In, 400 ppm Bi, and 10 ppm Al as additive elements. The particle size of the zinc alloy particles determined by the above-mentioned method was the average particle diameter (D ５０ ) was 120 μm, and the proportion of particles having a particle size of 75 μm or less was 25 mass % or less.

[0079] The zinc alloy particles and ZnO were mixed in a mass ratio of 97:3 to obtain a composition for forming a negative electrode (negative electrode composition). 78 mg of this composition was weighed out and used to prepare a negative electrode.

[0080] The alkaline electrolyte used was an aqueous solution in which potassium hydroxide was dissolved at a concentration of 35% by mass, and zinc oxide was further dissolved at a concentration of 3% by mass.

[0081] 5 g of an aqueous dispersion of PTFE (solid content: 60% by mass), 2.5 g of an aqueous solution of sodium polyacrylate (concentration: 2% by mass), and 2.5 g of hydrotalcite particles (average particle diameter: 0.4 μm) were kneaded and rolled to prepare a membrane with a thickness of 100 μm, which was then punched out into a circle with a diameter of 11.3 mm to prepare an anion conductive membrane.

[0082] A separator was constructed by laminating a multilayer film, in which two graft films (thickness: 30 μm) composed of a graft copolymer having a structure in which acrylic acid was graft copolymerized onto a polyethylene main chain, on both sides of a cellophane film (thickness: 20 μm), and vinylon-rayon mixed paper (thickness: 100 μm), and punching out a circle with a diameter of 11.3 mm. The anion conductive membrane was then further laminated on top of this.

[0083] The positive electrode (positive electrode mixture molded body), negative electrode (negative electrode composition), 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. The separator was positioned so that the anion conductive membrane was on the negative electrode side.

[0084] Next, a resin coating layer was formed on the exposed surface of the gasket in the battery container. The resin coating layer was formed using Cemedine's "EP001K" epoxy resin. The base resin and curing agent were mixed and applied to the exposed surface of the gasket. The mixture was then left to cure for 40 minutes at 23°C. This resulted in a button-type alkaline secondary battery having a structure similar to that shown in FIG. 1, a diameter of 11.5 mm, and a thickness of 3.0 mm. The Tg of the epoxy resin cured on the substrate under the same conditions as above was measured and found to be -64.7°C.

[0085] One of the produced button-type alkaline secondary 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 100 times, and the thickness was measured at five random points using the microscope's scale. The average of these measurements was taken as the thickness of the resin coating layer. The thickness of the obtained resin coating layer was 75 μm.

[0086] Comparative Example 1 A button-type alkaline secondary 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.

[0087] Comparative Example 2 A button-type alkaline secondary battery was produced in the same manner as in Example 1, except that a resin coating layer made of an epoxy resin having a Tg of 61°C, measured in the same manner as in Example 1, was formed on the exposed surface of the gasket.

[0088] Five button-type alkaline secondary batteries each of Example 1, Comparative Example 1, and Comparative Example 2 were prepared, and 10 charge-discharge cycles were performed in which the batteries were discharged at a constant current of 3.5 mA until the voltage reached 1.2 V, and then charged at a constant current of 7 mA until the voltage reached 1.8 V, followed by constant current-constant voltage charging at a constant voltage of 1.8 V until the current reached 0.7 mA. After that, the batteries were stored in an atmosphere at 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.

[0089]

[0090] As shown in Table 1, the button-type alkaline secondary battery of Example 1, in which a resin coating layer containing an epoxy resin (cured product) with a Tg of -20°C or less 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. 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 an epoxy resin with a Tg higher than -20°C, the number of days until leakage occurred was longer and the battery exhibited excellent leakage resistance.

[0091] 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.

[0092] 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).

[0093] 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.

[0094] 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 having a glass transition temperature of -20°C or lower.

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

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