Diaphragm for alkaline dry battery and alkaline dry battery

Abstract

A separator for an alkaline dry battery is disposed between a positive electrode and a negative electrode of an alkaline dry battery provided with the positive electrode, the negative electrode containing zinc, and an electrolyte solution. The separator contains a sulfate in an amount of 0.08-1.7 mg in terms of sulfate ions per 1 cm2 relative area between the positive electrode and the negative electrode.

Description

Technical Field

[0001] The present disclosure relates to alkaline dry batteries, and more particularly to a separator used in alkaline dry batteries. Background Art

[0002] Alkaline dry batteries (alkaline manganese dry batteries) are widely used because they have a larger capacity and can deliver higher currents than manganese dry batteries. Alkaline dry batteries typically consist of a positive electrode, a negative electrode, a separator positioned between the two electrodes, and an alkaline electrolyte. The positive electrode contains manganese dioxide as the positive electrode active material. Various proposals have been made to improve the characteristics of alkaline dry batteries.

[0003] Patent Document 1 proposes an alkaline battery separator comprising a cross-linked high water-absorbing polymer compound having a carboxyl group at a concentration of 5.0 to 45.0 g / m 2 The invention relates to an alkaline battery separator formed by attaching a wet-laid nonwoven fabric containing alkali-resistant fibers, and laminating the wet-laid nonwoven fabric containing alkali-resistant fibers to a cross-linked substrate, wherein the cross-linked highly water-absorbent polymer compound contains 1.0×10 -4 ~10mg / cm 2 Silicate compounds are added in a manner similar to that described above.

[0004] Patent Document 2 proposes adding a calcium compound or a sulfuric acid compound to at least one of a positive electrode, a negative electrode containing zinc, and an electrolyte in an alkaline battery comprising a positive electrode, a negative electrode containing zinc, and an electrolyte to prevent a decrease in discharge voltage under heavy-load discharge conditions. According to Patent Document 2, sulfate ions migrate toward the negative electrode along with H₂O during discharge. Therefore, even under heavy-load discharge conditions, the electrolyte volume near the negative electrode remains sufficient, thereby suppressing a decrease in discharge voltage.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-227067

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-297776 Summary of the Invention

[0009] For alkaline dry batteries using zinc as the negative electrode, an alkaline aqueous solution as the electrolyte, and a porous separator, during intermittent discharge at a medium load (e.g., 3.9Ω), tiny crystals of conductive zinc oxide may precipitate within the separator, causing an internal short circuit and shortening the discharge duration.

[0010] In Patent Document 1, a separator is formed by using 1.0×10 -4~10mg / cm 2 The silicate compound is added within a certain range. The silicate compound and the cross-linked highly water-absorbent polymer compound form a network structure between molecules, which can prevent short circuits caused by dendrites. However, in the separator described in Patent Document 1, although the addition of the silicate compound easily suppresses the precipitation of zinc oxide, the ionic conductivity of the electrolyte and the discharge characteristics are sometimes reduced. In addition, the effect of suppressing the precipitation of zinc oxide during use in medium-load intermittent discharge cannot be said to be sufficient, and it is required to suppress internal short circuits caused by the precipitation of zinc oxide at a higher level.

[0011] One aspect of the present disclosure relates to a separator for an alkaline dry battery, which is disposed between the positive electrode and the negative electrode of an alkaline dry battery having a positive electrode, a negative electrode containing zinc, and an electrolyte solution. 2 The relative area contains 0.08 mg or more and 1.7 mg or less of sulfate in terms of sulfate ions.

[0012] Another aspect of the present disclosure relates to an alkaline dry battery comprising: the hollow cylindrical positive electrode disposed in a battery case; the gel-like negative electrode containing zinc powder and filled in the hollow portion of the positive electrode; and a separator disposed between the positive electrode and the negative electrode, the separator comprising the alkaline dry battery separator.

[0013] According to the present disclosure, an alkaline dry battery can be realized in which the occurrence of an internal short circuit during medium-load intermittent discharge is suppressed by using a separator for an alkaline dry battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a partially exploded cross-sectional view showing an example of an alkaline dry battery according to an embodiment. DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes exemplified, but other numerical values ​​and other materials may also be applied as long as the invention to which the present disclosure relates can be implemented. In this specification, a description such as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be replaced by "above numerical value A and below numerical value B". In the following description, when a lower limit and an upper limit are exemplified for numerical values ​​of specific physical properties, conditions, etc., as long as the lower limit is not above the upper limit, any one of the exemplified lower limits can be arbitrarily combined with any one of the exemplified upper limits. When multiple materials are exemplified, one can be selected and used alone, or two or more can be used in combination.

[0016] Furthermore, the present disclosure includes combinations of matters described in two or more claimed technical solutions arbitrarily selected from the plurality of claimed technical solutions described in the attached claims. In other words, as long as no technical contradiction arises, matters described in two or more claimed technical solutions arbitrarily selected from the plurality of claimed technical solutions described in the attached claims may be combined.

[0017] (Separator for alkaline dry batteries)

[0018] The alkaline dry battery separator (hereinafter sometimes referred to as "separator") of this embodiment is arranged between the positive electrode and the negative electrode of an alkaline dry battery including a positive electrode, a negative electrode containing zinc, and an electrolyte solution. 2 The relative area contains 0.08 mg or more and 1.7 mg or less of sulfate in terms of sulfate ions.

[0019] By including sulfate in the separator, internal short circuits caused by precipitation of zinc oxide in a medium-load intermittent discharge usage environment can be suppressed, thereby achieving an alkaline dry battery having excellent medium-load intermittent discharge characteristics.

[0020] It is believed that the precipitation of zinc oxide is caused by the OH group in the electrolyte in the negative electrode caused by discharge. - Ions are consumed, the pH of the electrolyte decreases, and the electrolyte tilts toward neutrality, which reduces the solubility of zinc ions dissolved in the electrolyte. In particular, under usage conditions such as medium loads of approximately 250 to 500 mA, where discharge is repeated intermittently for approximately one hour per day, the pH of the electrolyte decreases significantly in certain areas, making the electrolyte prone to becoming neutral. This can lead to internal short circuits caused by the precipitation of zinc oxide.

[0021] Sulfate is difficult to dissolve in an undischarged alkaline dry cell due to the strongly alkaline electrolyte. However, as the pH of the electrolyte in the negative electrode decreases with discharge, it becomes readily soluble, further lowering the pH of the electrolyte toward the acidic side. Meanwhile, the solubility of zinc ions is lowest at neutral conditions and readily dissolves in alkaline and acidic conditions. Therefore, sulfate dissolves during medium-load intermittent discharge, shifting the pH of the electrolyte from neutral to acidic. This makes zinc ions more soluble, thus suppressing the precipitation of zinc oxide within the separator.

[0022] In addition to the separator, the negative electrode may also contain sulfate. However, internal short circuits caused by zinc oxide precipitation occur because the electrolyte in the separator shifts toward the neutral side. Therefore, the presence of sulfate in the separator is effective because it affects the pH of the electrolyte in the separator.

[0023] It should be noted that under heavy load (eg, approximately 1 A) discharge conditions, alkaline dry batteries generally experience a drop in discharge voltage and reach the end of their life before the electrolyte reaches neutrality, and thus are less likely to experience internal short circuits due to zinc oxide precipitation.

[0024] Regarding the content of sulfate contained in the separator, if the separator has a 1 cm 2 When the relative area is 0.08 mg or more in terms of sulfate ions, the effect of suppressing internal short circuits caused by the precipitation of zinc oxide can be fully achieved. On the other hand, if the sulfate content is excessive, the pores inside the separator are easily clogged, sometimes reducing ion conductivity or reducing the liquid retention of the electrolyte.

[0025] In order to suppress the decrease in ion conductivity and the decrease in liquid retention, the content of sulfate should be less than 1 cm 2 The relative area should be less than 1.7 mg in terms of sulfate ions. 2 The relative area may be 0.08 mg or more and 1.7 mg or less in terms of sulfate ions, preferably 0.1 mg or more and 1.0 mg or less, and more preferably 0.15 mg or more and 0.8 mg or less.

[0026] The sulfate can be contained in the portion of the separator facing the positive electrode and the negative electrode and sandwiched between the positive electrode and the negative electrode in the above-mentioned content. Figure 1 As shown, there is a separator having a cylindrical portion sandwiched between the positive and negative electrodes and a bottom portion sandwiched between the negative electrode and the battery case. In this case, at least the cylindrical portion of the cylindrical portion and the bottom portion only needs to contain sulfate within the above-mentioned range. The bottom portion is not particularly limited, and a conventional separator that does not contain sulfate can be used.

[0027] Every 1cm 2 The sulfate content of the opposing area refers to the sulfate content per 1 cm of the separator when a separator is used in the area where the positive electrode and the negative electrode face each other. 2 On the other hand, sometimes multiple separators are overlapped to form a desired total thickness, or a single separator is wound multiple times and overlapped to form a desired total thickness. In this case, the thickness of each 1 cm 2 The sulfate content of the opposing area refers to the sulfate content of each layer of the separator per 1 cm in the area where the positive electrode and the negative electrode face each other. 2 The value obtained by summing up the sulfate content.

[0028] The sulfate content converted into sulfate ions refers to the sulfate ions (SO4 2-) of the quality benchmark.

[0029] The sulfate content is determined by disassembling an undischarged alkaline dry cell, collecting at least a portion (e.g., 80% or more) of the separator in the area where the positive and negative electrodes face each other, and measuring its mass. The collected negative electrode is then exposed to pure water to dissolve the sulfate, and ion chromatography is performed to determine the sulfate content. 2- The mass of the sulfate in the negative electrode was calculated and the content of sulfate converted into sulfate ions was obtained. The content of sulfate converted into sulfate ions was divided by the area of ​​the collected separator to obtain the content of sulfate per 1 cm 2 The sulfate content calculated as sulfate ions relative to the area.

[0030] The cations that constitute the sulfate are not particularly limited as long as they do not interfere with the discharge reaction of the battery. The sulfate may be a salt of a metal cation and a sulfate ion. From the perspective of having a greater effect on lowering the pH after dissolution, the sulfate preferably comprises at least one selected from potassium sulfate, sodium sulfate, aluminum sulfate, potassium aluminum sulfate, calcium sulfate, zinc sulfate, and lithium sulfate, and preferably also comprises hydrates thereof.

[0031] As the separator, non-woven fabrics mainly composed of fibers, microporous films made of resins, etc. can be used. Examples of fiber materials include cellulose, polyvinyl alcohol, etc. The non-woven fabric can be formed by mixing cellulose fibers and polyvinyl alcohol fibers, or by mixing rayon fibers and polyvinyl alcohol fibers. Examples of the material of the microporous film include resins such as cellophane and polyolefins. In the case of a thin separator, multiple separators can be overlapped to adjust the thickness to the above-mentioned thickness.

[0032] The base material used in the alkaline dry cell separator of the present disclosure can use synthetic fibers and / or alkali-resistant cellulose fibers with excellent alkali resistance. Examples of synthetic fibers with excellent alkali resistance include at least one selected from polyvinyl alcohol fibers, ethylene-vinyl alcohol copolymer fibers, polypropylene fibers, polyethylene fibers, polyamide fibers, polypropylene / polyethylene composite fibers, and polypropylene / ethylene-vinyl alcohol copolymer composite fibers. As a binder, polyvinyl alcohol can be included in the synthetic fiber. For example, a synthetic fiber can be used in which polyvinyl alcohol fibers, cellulose fibers, and a polyvinyl alcohol binder are mixed in a range of 30 to 60% by mass of polyvinyl alcohol fibers, 30 to 60% by mass of cellulose fibers, and 5 to 23% by mass of polyvinyl alcohol binder.

[0033] The separator may preferably be a nonwoven fabric produced by wet-sheeting these fibers.

[0034] Among these fibers, the separator preferably comprises polyvinyl alcohol-based fibers. Polyvinyl alcohol-based fibers have excellent affinity (wettability) with water. Therefore, when a sulfate aqueous solution is used in the production method (ii) or (iii) described below, the sulfate easily adheres between the fibers of the highly hydrophilic polyvinyl alcohol-based fibers.

[0035] The separator may include fibrillated fibers. Fibrillated fibers are fibers made by rubbing the fibrils, which are small fibers within the fiber, to raise them. The branched fibers appear to be entangled like a net, creating a more complex three-dimensional structure than fibers simply folded from single fibers. Therefore, sulfates easily adhere to the three-dimensional structure of fibrillated fibers. Among them, fibrillated alkali-resistant cellulose fibers are preferred because sulfates easily and evenly adhere to the fine fibers.

[0036] Examples of methods for producing a separator containing sulfate include: (i) a method in which a solid sulfate is attached to the vicinity of the surface of a separator substrate; (ii) a method in which a sulfate solution is applied or impregnated onto a separator substrate sheet and then dried to precipitate the sulfate; and (iii) a method in which a sulfate solution is used when wet-making the separator substrate.

[0037] In the method (i) of attaching a solid sulfate near the surface of the separator substrate, the powdered sulfate is pressed onto the separator by pressing, thereby fixing the sulfate to the surface of the substrate sheet and the gaps between the fibers. In addition, when multiple layers of separator substrates are laminated to form a single separator, the sulfate can be arranged between the layers of the separator substrate. The sulfate can be made into a slurry by including a binder, and the slurry can be applied to the surface of the separator substrate or between the laminated layers. Examples of the binder include polyvinyl alcohol.

[0038] In the method (ii) of applying or impregnating a sulfate solution onto a separator substrate sheet and then drying the sheet to precipitate the sulfate, the sulfate solution can be an aqueous solution or an organic solvent such as an alcohol. Alternatively, a material that binds to the sulfate, such as polyvinyl alcohol, can be dissolved in the solvent along with the sulfate. Drying conditions are not particularly limited, as long as the temperature is above the solvent evaporation temperature.

[0039] In the method (iii) of using a solution containing a sulfate when wet-making the separator substrate, the sulfate solution can be an aqueous solution or a solution of an organic solvent such as alcohol. Alternatively, a material having adhesion to the sulfate, such as polyvinyl alcohol, can be dissolved in the solvent together with the sulfate.

[0040] The total thickness of the separator can be, for example, 150 μm to 450 μm, preferably 160 μm to 400 μm, and more preferably 170 μm to 340 μm. The total thickness of the separator is the average thickness of three angularly equivalent points on the cylindrical separator (three adjacent points separated by an angular interval of 120°). The total thickness of the separator refers to the thickness of the separator when it absorbs the electrolyte within the battery.

[0041] The total thickness T of the separator is determined by obtaining a cross-section of a manufactured alkaline dry cell using CT scanning and measuring the distance between the positive and negative electrodes. The distance from the tip of the positive terminal to the tip of the negative terminal is defined as the total height. The distance between the positive and negative electrodes is measured at three angularly equivalent points (three adjacent points spaced 120° apart) in a cross-section measuring half the total height. The average value of these three points is defined as the total thickness T of the separator.

[0042] The total air permeability of the separator can be, for example, 0.1 cc / cm 2 s or more and 8.7cc / cm 2 ·s or less, preferably 0.2cc / cm 2 s or more and 5.0cc / cm 2 ·s or less, more preferably 0.3cc / cm 2 s or more and 3.0cc / cm 2 s or less. The lower the total air permeability of the separator, the easier it is to suppress internal short circuits caused by the precipitation of zinc oxide, but the manufacturing cost increases. If the total air permeability is within the above range, the manufacturing cost will not be increased beyond necessity, and an alkaline dry battery that suppresses internal short circuits can be achieved even when used in medium-load intermittent discharge. It should be noted that the total air permeability of the portion of the separator sandwiched between the positive and negative electrodes only needs to be within the above range.

[0043] The total air permeability A of the separator is measured as follows: the alkaline dry battery after manufacture is disassembled and removed, the separator is washed with a 34% by mass KOH aqueous solution, and allowed to stand under reduced pressure at 20°C for 1 day and dried. The resulting separator is then measured according to the Frazier-type air permeability tester method specified in JIS L 1096:2010.

[0044] Separators can be formed to a desired total thickness by stacking multiple sheets of a single separator of a specified thickness, or by winding a single separator of a specified thickness multiple times and stacking them. In this case, if multiple sheets of the same type of separator are stacked, the total air permeability A can be calculated by dividing the air permeability of a single separator measured without stacking by the number of stacked sheets. If different types of separators are stacked, the total air permeability A can be calculated by measuring the air permeability of the stacked separators.

[0045] (Alkaline dry cell batteries)

[0046] The alkaline dry battery comprises a hollow cylindrical positive electrode disposed in a battery case, a gel-like negative electrode containing zinc powder and filling the hollow portion of the positive electrode, and a separator disposed between the positive electrode and the negative electrode. The separator comprises the above-mentioned separator for alkaline dry batteries.

[0047] The alkaline dry battery disclosed herein comprises a positive electrode, a negative electrode, a separator, and an electrolyte solution, and may comprise other components as required. The separator comprises the above-mentioned separator for alkaline dry batteries.

[0048] In one embodiment, an alkaline dry battery comprises a hollow cylindrical positive electrode disposed in a battery case, a gel-like negative electrode containing zinc powder and filling the hollow portion of the positive electrode, and a separator disposed between the positive electrode and the negative electrode. The separator may be the aforementioned separator for alkaline dry batteries.

[0049] Hereinafter, examples of components other than the separator of the alkaline dry battery of the present disclosure will be described.

[0050] (positive electrode)

[0051] The positive electrode contains manganese dioxide as the positive electrode active material. The positive electrode typically contains a positive electrode active material and a conductive material, and optionally, a binder. The positive electrode can be formed by pressurizing a positive electrode mixture into a cylindrical body (positive electrode pellets). The positive electrode mixture, for example, contains a positive electrode active material, a conductive material, an alkaline electrolyte, and optionally, a binder. The cylindrical body can also be pressurized after being housed in the housing body to ensure a tight fit with the inner wall of the housing body.

[0052] A preferred example of manganese dioxide as the positive electrode active material is electrolytic manganese dioxide, but natural manganese dioxide and chemical manganese dioxide can also be used. The crystal structure of manganese dioxide includes α-type, β-type, γ-type, δ-type, ε-type, η-type, λ-type, and ramsdellite-type.

[0053] The average particle size (D50) of the manganese dioxide powder may be, for example, in the range of 25 μm to 60 μm in order to easily ensure the filling property of the positive electrode and the diffusibility of the electrolyte in the positive electrode.

[0054] From the viewpoint of formability and suppression of positive electrode expansion, the BET specific surface area of ​​manganese dioxide can be, for example, 20 m 2 / g~50m 2 The BET specific surface area can be measured, for example, using a specific surface area measuring device based on a nitrogen adsorption method.

[0055] The conductive material can be a conductive carbon material. Examples of conductive carbon materials include carbon black (such as acetylene black) and graphite. Examples of graphite include natural graphite and artificial graphite. The conductive material can be a powdered conductive material. The average particle size (D50) of the conductive material can be in the range of 3 μm to 20 μm. The content of the conductive material in the positive electrode can be in the range of 3 to 10 parts by mass (e.g., 5 to 9 parts by mass) per 100 parts by mass of manganese dioxide.

[0056] To absorb hydrogen generated within the battery, a silver compound can be added to the positive electrode. Examples of silver compounds include silver oxide (Ag2O, AgO, Ag2O3, etc.) and silver-nickel composite oxide (AgNiO2).

[0057] (negative electrode)

[0058] The negative electrode contains zinc alloy powder as the negative electrode active material. From the perspective of corrosion resistance, the zinc alloy may contain at least one selected from indium, bismuth and aluminum. The indium content in the zinc alloy may be, for example, in the range of 0.01% by mass to 0.1% by mass. The bismuth content in the zinc alloy may be, for example, in the range of 0.003% by mass to 0.02% by mass. The aluminum content in the zinc alloy may be, for example, in the range of 0.001% by mass to 0.03% by mass. From the perspective of corrosion resistance, the content of elements other than zinc in the zinc alloy may be in the range of 0.025% by mass to 0.08% by mass.

[0059] From the perspective of negative electrode packing and electrolyte diffusibility within the negative electrode, the average particle size (D50) of the zinc alloy powder can be in the range of 100 μm to 200 μm (e.g., 110 μm to 160 μm). It should be noted that, in this specification, the average particle size refers to the median particle size (D50) at which the cumulative volume reaches 50% in a volume-based particle size distribution. The median particle size can be determined, for example, using a laser diffraction / scattering particle size distribution analyzer.

[0060] The negative electrode comprises zinc alloy powder, a gelling agent, a surfactant, and an electrolyte. The negative electrode can be formed by mixing the zinc alloy powder, gelling agent, surfactant, and electrolyte. To ensure a more uniform dispersion of additives (gelling agent, surfactant, etc.) in the negative electrode, it is preferred that the additives be pre-added to the electrolyte used to prepare the negative electrode. The electrolyte (alkaline electrolyte) described below can be used.

[0061] In order to improve corrosion resistance, a compound containing a metal having a high hydrogen overvoltage, such as indium or bismuth, may be appropriately added to the negative electrode.

[0062] To further suppress internal short circuits caused by zinc oxide precipitation under medium-load intermittent discharge conditions, sulfate may be included in the negative electrode in addition to the separator. In this case, the sulfate content in the negative electrode, calculated as sulfate ions, may be in the range of 0.01 to 0.5% by mass relative to the mass of the negative electrode.

[0063] (Negative electrode current collector)

[0064] The alkaline dry battery disclosed herein may include a negative electrode current collector inserted into the negative electrode. The negative electrode current collector may be made of a metal (elemental metal or an alloy). The negative electrode current collector is preferably made of copper, or may be an alloy of copper and zinc (e.g., brass). The negative electrode current collector may be plated with tin or other plating as needed.

[0065] (electrolyte)

[0066] As the electrolyte (alkaline electrolyte), for example, an alkaline aqueous solution containing potassium hydroxide can be used. The concentration of potassium hydroxide in the alkaline electrolyte is preferably in the range of 30 to 50% by mass (e.g., 30 to 40% by mass). The alkaline electrolyte may contain zinc oxide.

[0067] The alkaline electrolyte may contain a surfactant. The use of a surfactant can improve the dispersibility of the negative electrode active material particles. Examples of surfactants include those listed for the negative electrode. The surfactant content in the alkaline electrolyte is typically in the range of 0.001 to 0.5% by mass (e.g., 0.002 to 0.2% by mass).

[0068] (Battery casing)

[0069] The battery casing is not particularly limited; a casing corresponding to the shape of the battery can be used. The shape of the alkaline dry cell of this embodiment is not particularly limited; it can be cylindrical or coin-shaped (including button-shaped). The battery casing typically includes a battery shell, a negative terminal plate, and a gasket. The battery shell can be, for example, a metal shell with a bottom and a cylindrical shape. The metal shell can be, for example, a nickel-plated steel plate. To reduce the contact resistance between the positive electrode and the battery shell, the inner surface of the battery shell can be coated with a carbon film. The negative terminal plate can be formed of the same material as the metal shell, for example, a nickel-plated steel plate.

[0070] Examples of gasket materials include polyamide, polyethylene, polypropylene, polyphenylene ether, and polyphenylene oxide. From the perspective of corrosion resistance to alkaline electrolytes, preferred gasket materials include polyamide 6,6, polyamide 6,10, polyamide 6,12, and polypropylene. The gasket typically has a thin, annular portion.

[0071] An example embodiment of the present disclosure is described below in detail with reference to the accompanying drawings. The components of the alkaline dry cell described below can be applied to the components described above. Furthermore, the components of the alkaline dry cell described below can be modified based on the above description. Furthermore, the matters described below can also be applied to the above embodiment.

[0072] A partially exploded cross-sectional view of an alkaline dry cell 10 having an inside-outside structure according to an embodiment of the present disclosure is shown in FIG. Figure 1 The cylindrical alkaline dry battery 10 includes a battery case 1 , a positive electrode 2 disposed in the battery case 1 , a negative electrode (gel-like negative electrode) 3 , a separator 4 , and an electrolyte 15 .

[0073] The battery case 1 is a bottomed cylindrical case that functions as a positive electrode terminal. The positive electrode 2 is a hollow cylindrical case having a hollow portion 2H and is positioned in contact with the inner wall of the battery case 1. The negative electrode 3 is positioned within the hollow portion 2H of the positive electrode 2. The separator 4 is positioned between the positive electrode 2 and the negative electrode 3.

[0074] The separator 4 consists of a cylindrical separator 4a and a backing paper 4b. The separator 4a is positioned along the inner surface of the hollow portion 2H of the positive electrode 2, separating the positive electrode 2 from the negative electrode 3. The backing paper 4b is positioned at the bottom of the hollow portion 2H of the positive electrode 2, separating the negative electrode 3 from the battery case 1. Of the separator 4a and the backing paper 4b, at least the separator 4a has the above-described characteristics.

[0075] The opening of the battery case 1 is sealed by a sealing unit 9. The sealing unit 9 includes a gasket 5, a negative electrode current collector 6, and a negative electrode terminal plate 7 that functions as a negative electrode terminal. The negative electrode current collector 6 has a nail shape with a head and a main body. The negative electrode current collector 6 includes, for example, copper, or an alloy including copper and zinc, such as brass. The negative electrode current collector 6 may also be subjected to a plating treatment such as tin plating as needed. The main body of the negative electrode current collector 6 is inserted into the through hole provided in the center of the gasket 5, and is inserted into the negative electrode 3. The head of the negative electrode current collector 6 is welded to the flat portion in the center of the negative electrode terminal plate 7. The gasket 5 has an annular thin-walled portion 5a.

[0076] The open end of the battery case 1 is crimped to the peripheral edge (flange) of the negative electrode terminal plate 7 via the peripheral edge of the gasket 5. The outer surface of the battery case 1 is covered with an outer packaging label 8. The battery case 1, gasket 5, and negative electrode terminal plate 7 constitute the battery outer shell. The positive electrode 2, negative electrode 3, separator 4, and alkaline electrolyte 15 are disposed within the battery outer shell.

[0077] The method of assembling the alkaline dry battery 10 is not particularly limited, and existing techniques can be applied as needed.

[0078] <Example>

[0079] The alkaline dry battery separator and the alkaline dry battery disclosed herein are further described in detail through examples.

[0080] <Example 1>

[0081] (1) Preparation of electrolyte (alkaline electrolyte)

[0082] As the alkaline electrolyte, an alkaline aqueous solution containing potassium hydroxide (concentration: 33% by mass) and zinc oxide (concentration: 2% by mass) was prepared.

[0083] (2) Preparation of positive electrode

[0084] Manganese dioxide (positive electrode active material) and graphite (conductive material) were mixed to form a mixture. The mixture was mixed at a mass ratio of manganese dioxide to graphite of 100:6. Electrolytic manganese dioxide powder (average particle size (D50): 40 μm) was used for the manganese dioxide, and graphite powder (average particle size (D50): 8 μm) was used for the graphite.

[0085] The electrolyte was added to the mixture, stirred thoroughly, and then compressed into a sheet to obtain a positive electrode mixture. The mass ratio of the mixture to the electrolyte was set to 100:2. The electrolyte used was the same alkaline electrolyte prepared in (1) above.

[0086] Next, the flaky positive electrode mixture was crushed into pellets, which were then classified using a 10-100 mesh sieve to obtain granules. The resulting pellets were then press-molded into a hollow cylindrical shape (10.8 mm in height) to obtain positive electrode pellets (mass 2.9 g).

[0087] (3) Preparation of negative electrode

[0088] A gel-like negative electrode was obtained by mixing zinc alloy powder, a surfactant, a gelling agent, and an electrolyte. Materials other than the zinc alloy powder were mixed in a mass ratio of surfactant:gelling agent:electrolyte = 0.005:2.4:100. The electrolyte used was the same alkaline electrolyte prepared in (1) above. The content of the zinc alloy powder relative to the total negative electrode was 66% by mass. The negative electrode active material used was a zinc alloy powder containing 0.02% by mass of indium, 0.01% by mass of bismuth, and 0.005% by mass of aluminum. The surfactant used was an anionic surfactant. The gelling agent used was a mixture of cross-linked polyacrylic acid and a partial sodium salt of cross-linked polyacrylic acid.

[0089] (4) Production of diaphragm

[0090] As the base material for the separator 4a, a nonwoven fabric sheet was prepared, primarily composed of a mixture of rayon fibers and polyvinyl alcohol fibers. As the alkali-resistant cellulose fiber, rayon fibers (Polynosic rayon fibers) were beaten and fibrillated. The fibrillated rayon fibers were mixed with polyvinyl alcohol fibers and a polyvinyl alcohol binder at a mass ratio of 50:40:10. Using a wet paper machine, a sheet with a thickness of 100 μm and a weight per unit area of ​​32 g / m was obtained. 2 Non-woven fabric sheet.

[0091] Zinc sulfate heptahydrate (ZnSO₄·7H₂O) was dissolved in water to prepare a 10% by mass aqueous solution of the sulfate (ZnSO₄). When using a sulfate hydrate, the amount of hydrate added was adjusted to achieve a sulfate concentration of 10% by mass in the aqueous solution. A nonwoven fabric sheet was placed on a smooth polytetrafluoroethylene plate, and the sulfate aqueous solution was evenly applied to the nonwoven fabric sheet. The sheet was then dried at 90°C to adhere the sulfate to the nonwoven fabric sheet. The nonwoven fabric sheet with the sulfate adhered to it was double-wound into a cylindrical shape to produce a cylindrical separator 4a.

[0092] A nonwoven fabric sheet mainly composed of a mixture of rayon fibers and polyvinyl alcohol fibers (mass ratio 1:1) was prepared as the backing paper 4b. A cylindrical separator 4 with a bottom was formed using the cylindrical separator 4a and the backing paper 4b.

[0093] (5) Assembly of alkaline dry batteries

[0094] Using the above components, alkaline dry cell batteries were assembled by the following method. Figure 1 The battery assembly steps are explained.

[0095] First, a coating agent (product name: バニーハイト) manufactured by Nippon Kokuen Co., Ltd. is applied to the inner surface of a bottomed cylindrical shell made of nickel-plated steel sheet to form a carbon film with a thickness of about 10 μm, thereby obtaining a battery shell 1. Next, four positive electrode pellets are inserted longitudinally into the battery shell 1 and then pressurized to form a positive electrode 2 in a state of close contact with the inner wall of the battery shell 1. After a bottomed cylindrical separator 4 is arranged on the inner side of the positive electrode 2, the alkaline electrolyte prepared in (1) above is injected and impregnated into the separator 4. The battery is left in this state for a predetermined time to allow the alkaline electrolyte to penetrate from the separator 4 to the positive electrode 2. Then, 6.3 g of the gel-like negative electrode 3 is filled inside the separator 4.

[0096] The negative electrode current collector 6 is formed by stamping conventional brass into a nail shape and then tinning the surface. The head of the negative electrode current collector 6 is welded to the negative electrode terminal plate 7 made of nickel-plated steel. The main body of the negative electrode current collector 6 is then press-fitted into the central through-hole of the gasket 5, which is primarily composed of polyamide 6,10. This completes the sealing unit 9 consisting of the gasket 5, negative electrode current collector 6, and negative electrode terminal plate 7.

[0097] Next, the sealing unit 9 is placed in the opening of the battery case 1. At this point, the main body of the negative electrode current collector 6 is inserted into the negative electrode 3. Next, the open end of the battery case 1 is crimped onto the peripheral edge of the negative electrode terminal plate 7 with the gasket 5 interposed therebetween, thereby sealing the opening of the battery case 1. Thus, the positive electrode 2, negative electrode 3, separator 4, and alkaline electrolyte 15 are placed in the battery case.

[0098] Next, the outer surface of the battery case 1 was covered with the outer label 8. In this way, the alkaline dry battery A1 of Example 1 was produced.

[0099] The battery A1 was disassembled after fabrication, and the separator 4a containing the electrolyte was collected. The sulfate ions (SO4 2- ) was quantitatively determined. As a result, the content of sulfate contained in the separator 4a was determined per 1 cm between the positive electrode and the negative electrode. 2 The relative area was calculated as 0.08 mg in terms of sulfate ion.

[0100] (6) Evaluation

[0101] The battery was connected to a 3.9Ω resistor via a switch. The switch was turned on with a duty cycle of 1 hour per day, and intermittent discharge was performed. Specifically, a cycle of 1 hour of discharge followed by a 23-hour rest period was repeated in an environment of 20±1°C. This discharge cycle was repeated until the battery voltage reached 0.8V.

[0102] For 20 alkaline dry cell batteries (N = 20), the total discharge time (i.e., the total period during which the switch was in the on state) from the start of discharge to the point when the battery voltage dropped below 0.8 V was evaluated as the duration. If the duration was less than 8 hours, it was determined that an internal short circuit had occurred during discharge. The number of batteries with a duration of less than 8 hours, n, was determined.

[0103] <Examples 2 to 10, Comparative Examples 1 to 3>

[0104] Alkaline dry batteries A2 to A10 and B1 to B3 of Examples 2 to 12 and Comparative Examples 1 to 3 were produced and evaluated in the same manner as in Example 1 except that the content and / or type of sulfate added to the separator 4a was changed.

[0105] In Comparative Example 1, an alkaline dry battery was produced without adding sulfate to the negative electrode, and battery B1 was obtained.

[0106] For batteries A2 to A10, B2, and B3, the batteries were disassembled and the separator 4a was collected in the same manner as for battery A1. The sulfate ions (SO4 2- ) was quantified, and the content of sulfate contained in the separator 4a was taken as the content of sulfate contained in the separator 4a per 1 cm between the positive electrode and the negative electrode. 2 The relative area was calculated as a value converted to sulfate ions. The results are shown in Table 1.

[0107] <Comparative Example 4>

[0108] In Example 1, a separator 4 a to which potassium silicate (K 2 SiO 3 ) was added instead of sulfate was used. Alkaline dry battery B4 was produced in the same manner as in Example 1 except for the above. The battery was evaluated in the same manner as in Example 1.

[0109] The battery B4 was disassembled and the separator 4a was collected. The silicate ions (SiO3 2- ) was quantitatively determined to determine the silicate content in the separator 4a. The results showed that the silicate content per 1 cm between the positive and negative electrodes was 2 The relative area was calculated as 0.08 mg in terms of silicate ions.

[0110] Table 1 shows the evaluation results of the duration. In Table 1, for batteries A1 to A10 and B1 to B4, the ratio n / N of batteries with a duration of less than 8 hours is expressed as the occurrence ratio of internal short circuits. In addition, Table 1 shows the type and content of the salt compound (sulfate or silicate) added to the separator 4a of batteries A1 to A10 and B1 to B4 together with the occurrence ratio n / N of internal short circuits. The content of sulfate or silicate represents the number of cells per 1 cm between the positive electrode and the negative electrode. 2 The percentage of the mass of sulfate ions or silicate ions in the salt compound relative to the area.

[0111] As shown in Table 1, when the distance between the positive and negative electrodes is 1 cm, 2In batteries A1 to A10 containing separators 4a containing sulfate so that the relative area in terms of sulfate ions fell within the range of 0.08 mg to 1.7 mg, internal short circuits were suppressed without causing a decrease in discharge performance.

[0112] In Battery B2, the addition of sulfate to the separator reduced the occurrence rate of internal short circuits compared to Battery B1, which did not add sulfate to the separator. However, the sulfate content per 1 cm 2 The relative area was as small as 0.06 mg in terms of sulfate ions, and therefore internal short circuits could not be sufficiently suppressed.

[0113] In battery B3, the amount of sulfate added was 1.83 mg, which was sufficiently large to fully suppress internal short circuits. However, the pores inside the separator were easily clogged, resulting in reduced ion conductivity and electrolyte retention, which sometimes led to reduced discharge performance.

[0114] In battery B4 in which silicate was added to the separator, the occurrence rate of internal short circuits was lower than that of battery B1. However, internal short circuits could not be fully suppressed and occurred at a considerable rate.

[0115]

Table 1

[0116]

[0117] Industrial applicability

[0118] The present disclosure can be applied to alkaline dry batteries.

[0119] Description of Reference Numerals

[0120] 1: Battery housing

[0121] 2: Positive electrode

[0122] 3: Negative electrode

[0123] 4: Diaphragm

[0124] 4a: Cylindrical diaphragm

[0125] 4b: Bottom paper

[0126] 5: Padding

[0127] 5a: Thin-walled part

[0128] 6: Negative electrode collector

[0129] 7: Negative terminal plate

[0130] 8: Outer packaging label

[0131] 9: Sealing unit

[0132] 10: Alkaline dry batteries

Claims

1. A separator for an alkaline dry battery, the separator being arranged between the positive electrode and the negative electrode of an alkaline dry battery comprising a positive electrode, a negative electrode containing zinc, and an electrolyte solution. The separator for alkaline dry batteries has a thickness of 1 cm between the positive electrode and the negative electrode. 2 The relative area contains 0.08 mg or more and 1.7 mg or less of sulfate in terms of sulfate ions.

2. The alkaline dry battery separator according to claim 1, wherein The sulfate includes at least one selected from potassium sulfate, sodium sulfate, aluminum sulfate, potassium aluminum sulfate, calcium sulfate, zinc sulfate, lithium sulfate, and hydrates thereof. The alkaline dry battery separator according to claim 1 , further comprising polyvinyl alcohol-based fibers. The alkaline dry battery separator according to claim 1 , further comprising fibrillated fibers.

5. An alkaline dry cell battery comprising: The positive electrode is disposed in the battery case and has a hollow cylindrical shape and a hollow portion; the gel-like negative electrode filled in the hollow portion of the positive electrode and containing zinc powder; and a separator disposed between the positive electrode and the negative electrode, The separator includes the separator for alkaline dry batteries according to any one of claims 1 to 4.

Images