Alkaline dry battery

Abstract

This alkaline dry battery is provided with: a hollow cylindrical positive electrode disposed in a battery case; a gel-like negative electrode filled in the hollow part of the positive electrode and containing zinc powder; and a separator disposed between the positive electrode and the negative electrode. And the total air permeability of the diaphragm is in the range of 1.5-8.7 cc / cm < 2 >. S. The negative electrode contains a sulfate in an amount of 0.01-0.5 mass% relative to the mass of the negative electrode in terms of sulfate ions.

Description

Technical Field

[0001] The present disclosure relates to alkaline dry cell 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 discloses an alkaline battery separator comprising alkali-resistant fibers, beaten cellulose fibers, and a binder. The separator has a combined water filterability of 700 ml or more, as measured by CSF value. The weight ratio of the alkali-resistant fibers to the beaten cellulose fibers is 28:72 to 72:28. The beaten cellulose fibers comprise mercerized natural wood fibers, and the natural wood fibers have a water filterability of 150 ml or more and less than 550 ml, as measured by CSF value. The separator is described as preferably having an air permeability of 13 cc / cm 2 / sec or less.

[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 No. 2017-047638

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

[0009] To keep manufacturing costs low, one approach is to use inexpensive, general-purpose separators in alkaline dry batteries. However, these general-purpose separators have high air permeability and low barrier properties. Consequently, during medium-load intermittent discharge, zinc oxide precipitates within the separator, making internal short circuits more likely.

[0010] One aspect of the present disclosure relates to an alkaline dry battery comprising: a hollow cylindrical positive electrode disposed within 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, wherein the separator has a total air permeability of 1.5 to 8.7 cc / cm 2 In the range of ·s, the negative electrode contains sulfate in an amount of 0.01 to 0.5% by mass relative to the mass of the negative electrode in terms of sulfate ions.

[0011] According to the present disclosure, it is possible to suppress the occurrence of an internal short circuit during medium-load intermittent discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a partially exploded cross-sectional view showing an example of an alkaline dry battery according to an embodiment. DETAILED DESCRIPTION

[0013] 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.

[0014] 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.

[0015] (Alkaline dry cell batteries)

[0016] The alkaline dry cell battery of this embodiment comprises: a hollow cylindrical positive electrode disposed within the battery case; a gel-like negative electrode containing zinc powder, which is filled within the hollow portion of the positive electrode; and a separator disposed between the positive and negative electrodes. The zinc powder includes zinc alloy powder. The total air permeability of the separator is between 1.5 and 8.7 cc / cm 2The negative electrode contains sulfate in an amount of 0.01 to 0.5% by mass relative to the mass of the negative electrode in terms of sulfate ions.

[0017] By including sulfate in the negative electrode, internal short circuits caused by the precipitation of zinc oxide under medium-load intermittent discharge conditions are suppressed, resulting in a total air permeability of 1.5 cc / cm 2 ·s or more, a relatively inexpensive separator can realize an alkaline dry cell with excellent medium-load intermittent discharge characteristics.

[0018] 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.

[0019] Sulfate added to the negative electrode is difficult to dissolve in the electrolyte of an undischarged alkaline dry cell due to its strong alkalinity. 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, zinc ions have the lowest solubility at neutral temperatures and readily dissolve in alkaline and acidic conditions. Therefore, sulfate dissolves during medium-load intermittent discharge, shifting the pH of the electrolyte from neutral to acidic, making zinc ions more soluble and suppressing the precipitation of zinc oxide.

[0020] 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.

[0021] If the content of sulfate contained in the negative electrode is 0.01% by mass or more in terms of sulfate ion conversion relative to the mass of the negative electrode, the effect of suppressing the internal short circuit caused by the precipitation of zinc oxide can be fully obtained. On the other hand, if the content of sulfate is excessive, the uneven distribution of sulfate inside the negative electrode becomes larger, so the uneven pH of the electrolyte inside the negative electrode becomes larger during discharge, sometimes promoting internal short circuit. From the aspect of suppressing the pH unevenness of the electrolyte, the content of sulfate can be 0.5% by mass or less in terms of sulfate ion conversion relative to the mass of the negative electrode. The content of sulfate can be 0.01% by mass or more and 0.5% by mass or less, preferably 0.05% by mass or more and 0.3% by mass or less, more preferably 0.08% by mass or more and 0.2% by mass or less.

[0022] Here, the content of sulfate converted into sulfate ions refers to the sulfate ions (SO4 2- The content of sulfate is determined by disassembling an undischarged alkaline dry cell, collecting at least a portion of the negative electrode (e.g., 80% or more) 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 content of sulfate. 2- The amount of sulfate was quantified and the mass of the sulfate in the negative electrode was calculated, thereby determining the content of sulfate converted into sulfate ions.

[0023] When the sulfate content is within the above range, if the total air permeability of the separator is 8.7 cc / cm 2 ·s or less, the internal short circuit caused by the precipitation of zinc oxide can be fully suppressed. On the other hand, the smaller the total air permeability of the separator, the easier it is to suppress the internal short circuit, but the manufacturing cost increases. If the total air permeability of the separator is 1.5cc / cm 2 ·s or more, it is possible to realize an alkaline dry battery in which the increase in manufacturing cost is suppressed and internal short circuit is suppressed even when used in medium load intermittent discharge. The total air permeability of the separator is 1.5cc / cm 2 s or more and 8.7cc / cm 2 ·s or less, more preferably 1.5cc / cm 2 s or more and 5cc / cm 2 ·s or less.

[0024] It should be noted that the total air permeability of the portion of the separator sandwiched between the positive electrode and the negative electrode only needs to meet the above range. As an example of the structure of the separator, as described later Figure 1As shown, there is a diaphragm having a cylindrical portion sandwiched between the positive electrode and the negative electrode and a bottom sandwiched between the negative electrode and the battery case. In this case, the total permeability of at least the cylindrical portion of the cylindrical portion and the bottom only needs to satisfy the above range, and there is no special limitation on the total permeability of the bottom.

[0025] The total air permeability A of the separator was measured as follows: the alkaline dry battery after manufacture was disassembled and removed, the separator was washed with a 34% by mass KOH aqueous solution, and allowed to stand for 1 day under reduced pressure at 20°C and dried. The resulting separator was then measured using the Frazier-type air permeability tester method specified in JIS L 1096:2010.

[0026] 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.

[0027] The total thickness of the separator should be 250 μm to 450 μm, preferably 270 μm to 400 μm, and more preferably 300 μm to 380 μm. The total thickness of the separator is the average thickness at 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 when the separator absorbs the electrolyte within the battery.

[0028] 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 in a cross-section measuring half the total height is measured at three angularly equivalent points (three adjacent points spaced 120° apart). The average value of these three points is defined as the total thickness T of the separator.

[0029] 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.

[0030] The alkaline dry battery disclosed herein comprises a positive electrode, a negative electrode, a separator, and an electrolyte, and may comprise other components as required. Examples of the components of the alkaline dry battery disclosed herein are described below.

[0031] (positive electrode)

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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).

[0038] (negative electrode)

[0039] 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.

[0040] 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.

[0041] The negative electrode comprises zinc alloy powder, a gelling agent, a surfactant, a sulfate, and an electrolyte. The negative electrode can be formed by mixing the zinc alloy powder, gelling agent, surfactant, sulfate, and electrolyte. To ensure more uniform dispersion of additives (gelling agent, surfactant, etc.) in the negative electrode, it is preferred to pre-add the additives to the electrolyte used to prepare the negative electrode. The electrolyte (alkaline electrolyte) described below can be used.

[0042] 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.

[0043] (Negative electrode current collector)

[0044] 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.

[0045] (diaphragm)

[0046] As the separator, a non-woven fabric mainly composed of fibers, a microporous film made of a resin, 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 polyolefin. In the case of a thin separator, multiple separators can be overlapped to adjust the thickness to the above-mentioned thickness.

[0047] (electrolyte)

[0048] 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.

[0049] 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).

[0050] (Battery casing)

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 solution (not shown).

[0055] The battery case 1 is a bottomed cylindrical case that functions as the positive electrode terminal. The positive electrode 2 is a hollow cylindrical structure placed in contact with the inner wall of the battery case 1. The negative electrode 3 is placed within the hollow portion 2H of the positive electrode 2. The separator 4 is placed between the positive electrode 2 and the negative electrode 3. The negative electrode has the characteristics described above.

[0056] The separator 4 is composed of a cylindrical separator 4a and a backing paper 4b. The separator 4a is arranged along the inner surface of the hollow portion 2H of the positive electrode 2, isolating the positive electrode 2 from the negative electrode 3. The backing paper 4b is arranged at the bottom of the hollow portion 2H of the positive electrode 2, isolating the negative electrode 3 from the battery case 1. The total air permeability of the separator 4a is between 1.5 and 8.7 cc / cm 2 ·The range of s.

[0057] 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.

[0058] 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 (not shown) are arranged within the battery outer shell.

[0059] The method of assembling the alkaline dry battery 10 is not particularly limited, and existing techniques can be applied as needed.

[0060] <Example>

[0061] The alkaline dry cell of the present disclosure is further described in detail through examples.

[0062] <Example 1>

[0063] (1) Preparation of electrolyte (alkaline electrolyte)

[0064] As the alkaline electrolyte, an alkaline aqueous solution containing potassium hydroxide (concentration: 33% by mass) and zinc oxide (concentration: 2% by mass) was prepared.

[0065] (2) Preparation of positive electrode

[0066] 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.

[0067] 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.

[0068] 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).

[0069] (3) Preparation of negative electrode

[0070] A gelled negative electrode was obtained by mixing zinc alloy powder, a surfactant, a gelling agent, a sulfate, and an electrolyte. The zinc alloy powder and materials other than the sulfate 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. Potassium sulfate (K2SO4) was used as the sulfate, and the content thereof was 0.01% by mass in terms of sulfate ions relative to the entire negative electrode. The content of the zinc alloy powder and the sulfate relative to the entire negative electrode was 66% by mass. The negative electrode active material used was 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.

[0071] (4) Assembly of alkaline dry batteries

[0072] Using the above components, alkaline dry cell batteries were assembled by the following method. Figure 1 The battery assembly steps are explained.

[0073] 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.

[0074] The separator 4 is formed by using a cylindrical separator 4a and a backing paper 4b. The cylindrical separator 4a and the backing paper 4b are made of a non-woven fabric sheet mainly composed of a mixture of rayon fiber and polyvinyl alcohol fiber (mass ratio is 1:1). The separator 4a is made of a non-woven fabric with a total air permeability of 1.5cc / cm 2 ·s diaphragm.

[0075] 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.

[0076] 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 periphery 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 (not shown) are placed in the battery case.

[0077] 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.

[0078] For battery A1, a cross section from the positive electrode terminal at the bottom of the battery case 1 to half the height of the negative electrode terminal plate 7 was obtained by CT scanning, and the total thickness of the separator was determined by the above method. The total thickness of the separator was 340 μm.

[0079] (5) Evaluation

[0080] 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.

[0081] 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.

[0082] <Examples 2 to 12, Comparative Examples 1 to 8>

[0083] Alkaline dry batteries A2 to A12 and B1 to B8 of Examples 2 to 12 and Comparative Examples 1 to 8 were produced and evaluated in the same manner as in Example 1 except that the total air permeability of the separator 4a and / or the sulfate content in the negative electrode were changed.

[0084] In Comparative Examples 1, 2, and 5, alkaline dry batteries were produced without adding sulfate to the negative electrode, and batteries B1, B2, and B5 were obtained, respectively.

[0085] For batteries A2 to A12 and B1 to B8, a cross-section at a height of 1 / 2 the height from the positive terminal at the bottom of the battery case 1 to the negative terminal plate 7 was obtained by CT scanning, and the total thickness of the diaphragm was calculated using the above method. The results showed that batteries A2 to A12 and B1 to B8 were the same as battery A1.

[0086] Table 1 shows the evaluation results of the duration. For Batteries A1-A12 and B1-B8, the ratio n / N of batteries with a duration of less than 8 hours is expressed as the internal short circuit occurrence rate. Table 1 also shows the total air permeability of the separator 4a and the sulfate content in the negative electrode for Batteries A1-A12 and B1-B8, along with the internal short circuit occurrence rate n / N. The sulfate content represents the percentage of the mass of sulfate ions in the sulfate relative to the total mass of the negative electrode.

[0087] As shown in Table 1, the total air permeability of the separator 4a is between 1.5 and 8.7 cc / cm 2 In the case of batteries A1 to A12 in which the content of sulfate is in the range of 0.01 to 0.5 mass % in terms of sulfate ions, internal short circuits are suppressed without increasing the manufacturing cost.

[0088]

Table 1

[0089]

[0090] In battery B1, the total air permeability of separator 4a is 1.3 cc / cm 2 ·s, using a separator with sufficiently low total air permeability and high barrier properties, internal short circuits can be suppressed even without adding sulfate to the negative electrode. However, the increased man-hours required to produce the separator and the increased material costs increase manufacturing costs.

[0091] In Battery B2, due to the use of a separator with a higher total air permeability than in Battery B1, internal short circuits could not be suppressed, resulting in a significant incidence of internal short circuits. In Battery B3, the addition of sulfate to the negative electrode reduced the incidence of internal short circuits compared to Battery B2, but the sulfate content, as low as 0.005% by mass (calculated as sulfate ions), was insufficient to suppress internal short circuits. Similarly, Batteries B5 and B6, with sulfate contents below 0.005% by mass (calculated as sulfate ions), also failed to adequately suppress internal short circuits.

[0092] On the other hand, in Batteries B4 and B7, the sulfate content, calculated as sulfate ions, was 0.7% by mass, which was excessive. Consequently, the incidence of internal short circuits increased compared to Batteries A4 and A12, respectively, and internal short circuits could not be suppressed. This is believed to be because the increased sulfate content increased the uneven distribution of sulfate within the negative electrode, increasing the pH variation of the electrolyte within the negative electrode, which in turn promoted internal short circuits.

[0093] The total air permeability of the diaphragm 4a is as high as over 8.7cc / cm 2 In the battery B8 with ·s, the internal short circuit could not be sufficiently suppressed simply by adding sulfate to the negative electrode.

[0094] <Examples 13 to 23>

[0095] In the preparation of the negative electrode (3) above, the sulfate added to the negative electrode was changed from potassium sulfate (K2SO4) in Example 1. Otherwise, the same procedures as in Example 1 were followed to prepare alkaline dry batteries A13 to A23 of Examples 13 to 23, and the same evaluations were performed.

[0096] In Examples 14 to 23, the total air permeability of the separator 4a was further changed from that in Example 1, and batteries A14 to A23 were obtained, respectively.

[0097] Table 2 shows the evaluation results for batteries A13 to A23, along with the evaluation results for batteries A1, A7, and A9. For each battery, the ratio n / N of batteries with a duration of less than 8 hours is expressed as the internal short circuit occurrence rate. Table 2 also shows the total thickness of the separator in each battery and the type of sulfate contained in the negative electrode, along with the internal short circuit occurrence rate n / N. The sulfate content of each battery shown in Table 2, calculated as sulfate ions, was 0.01% by mass relative to the total mass of the negative electrode.

[0098]

Table 2

[0099]

[0100] As shown in Table 2, in batteries A13 to A23, internal short circuits were suppressed regardless of the type of sulfate added to the negative electrode.

[0101] Industrial applicability

[0102] The present disclosure can be applied to alkaline dry batteries.

[0103] Description of Reference Numerals

[0104] 1: Battery housing

[0105] 2: Positive electrode

[0106] 3: Negative electrode

[0107] 4: Diaphragm

[0108] 4a: Cylindrical diaphragm

[0109] 4b: Bottom paper

[0110] 5: Padding

[0111] 5a: Thin-walled part

[0112] 6: Negative electrode collector

[0113] 7: Negative terminal plate

[0114] 8: Outer packaging label

[0115] 9: Sealing unit

[0116] 10: Alkaline dry batteries

Claims

1. An alkaline dry cell battery comprising: A hollow cylindrical positive electrode disposed in the battery case and having a hollow portion; a 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 total air permeability of the diaphragm is 1.5 cc / cm 2 ·s~8.7cc / cm 2 The range of s, The negative electrode contains sulfate in an amount of 0.01% by mass to 0.5% by mass relative to the mass of the negative electrode, calculated as sulfate ions.

2. The alkaline dry battery 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.

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