Alkaline dry cell

Abstract

This alkaline dry cell comprises a positive electrode 2, a negative electrode 3, a separator 4, and an electrolyte. The negative electrode 3 contains zinc alloy particles as a negative electrode active substance. The electrolyte contains an additive represented by formula (a). (In formula (a), n is a natural number from 3 to 7, and m is a natural number from 3 to 7.)

Description

alkaline batteries

[0001] The present disclosure relates to alkaline dry batteries.

[0002] Alkaline batteries (alkaline manganese batteries) are widely used because they have a larger battery capacity and can extract a larger current than manganese batteries. Alkaline batteries contain a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an alkaline electrolyte. Various proposals have been made to improve the performance of alkaline batteries.

[0003] Claim 1 of Patent Document 1 (JP 2008-34375 A) describes "an alkaline dry battery comprising: a positive electrode containing at least one of manganese dioxide powder and nickel oxyhydroxide powder; a negative electrode containing zinc alloy powder; a separator disposed between the positive electrode and the negative electrode; an alkaline electrolyte; a metal case containing iron as a main component; and a nickel-containing layer formed on the inner surface of the metal case, the battery case accommodating the positive electrode, the negative electrode, the separator, and the alkaline electrolyte; wherein the negative electrode further contains a surfactant that is adsorbed to the surface of the zinc alloy powder when not discharging, and that is quickly desorbed from the surface of the zinc alloy powder at the start of discharging without interfering with the movement of ions in the alkaline electrolyte."

[0004] JP 2008-34375 A

[0005] The invention described in Patent Document 1 aims to provide an alkaline dry battery that is excellent in leakage resistance and discharge performance, in which gas generation is suppressed without inhibiting the negative electrode reaction (paragraph 0009 of Patent Document 1). However, alkaline dry batteries have problems not only with gas generation during normal charge and discharge, but also with hydrogen gas generation during overdischarge. One of the objectives of the present disclosure is to provide an alkaline dry battery that generates less hydrogen gas during overdischarge.

[0006] One aspect of the present disclosure relates to an alkaline dry battery including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode contains zinc alloy particles as a negative electrode active material, and the electrolyte contains an additive represented by the following formula (a):

[0007] (In formula (a), n is a natural number of 3 or more and 7 or less, and m is a natural number of 3 or more and 7 or less.)

[0008] According to the present disclosure, an alkaline dry battery that generates less hydrogen gas during overdischarge is obtained. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0009] Fig. 1 is a partially exploded cross-sectional view schematically showing an example of an alkaline dry battery according to Embodiment 1. Fig. 2 is a graph showing some of the evaluation results in Examples.

[0010] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the invention of the present disclosure can be implemented. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or greater and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0011] (Alkaline dry battery) The alkaline dry battery according to this embodiment may be referred to as an "alkaline dry battery (AB)" below. The alkaline dry battery (AB) includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode contains zinc alloy particles as a negative electrode active material. The electrolyte contains an additive represented by the following formula (a). The additive represented by the following formula (a) may be referred to as an "additive (A)" below.

[0012] (In formula (a), n is a natural number of 3 or more and 7 or less, and m is a natural number of 3 or more and 7 or less.)

[0013] When alkaline batteries are over-discharged, excessive elution of the zinc alloy (negative electrode active material) in the negative electrode causes cracks in the zinc alloy surface, forming a new surface. It is thought that protons in the electrolyte come into contact with this new surface, causing reduction and generating hydrogen gas.

[0014] Patent Document 1 discloses polyoxyethylene alkyl ether phosphate ester as an example of a surfactant for suppressing gas generation. However, polyoxyethylene alkyl ether phosphate ester was insufficient in suppressing hydrogen gas generation during overdischarge. Polyoxyethylene alkyl ether phosphate ester has a hydrophilic group in its side chain, which gives it a strong adsorption force to the surface of a zinc alloy. Therefore, it is believed that almost the entire amount of the added polyoxyethylene alkyl ether phosphate ester is adsorbed to the surface of the zinc alloy before discharge. In this case, the newly formed surface during overdischarge cannot be covered with polyoxyethylene alkyl ether phosphate ester, and hydrogen gas generation cannot be sufficiently suppressed.

[0015] In the alkaline dry battery (AB) according to the present disclosure, an additive (A) represented by formula (a) is used as an additive for the electrolyte. Because the additive (A) has a linear alkyl group instead of a hydrophilic polyoxyethylene group, its adsorption to the surface of the zinc alloy is not very strong. Therefore, it is believed that there is excess additive (A) in the electrolyte to which the additive (A) is added that is not adsorbed to the surface of the zinc alloy. This excess additive (A) can cover the newly formed surface of the zinc alloy during overdischarge. Therefore, it is believed that the use of the additive (A) can effectively suppress hydrogen gas generation during overdischarge.

[0016] When additive (A) has an alkyl group with 3 or less carbon atoms, i.e., when at least one of n and m is 2 or less, the effect of suppressing hydrogen gas generation is reduced. This is thought to be because when the alkyl group has 3 or less carbon atoms, the surface of the zinc alloy is not sufficiently coated with additive (A). When additive (A) has an alkyl group with 9 or more carbon atoms, i.e., when at least one of n and m is 8 or more, the effect of suppressing hydrogen gas generation is reduced. This is thought to be because the increased molecular weight of the additive makes it difficult for the additive to migrate into and coat cracks that occur in the zinc alloy during overdischarge.

[0017] The alkyl group contained in the additive (A) is a linear alkyl group. Since a linear alkyl group has a higher density per molecular volume than a branched alkyl group, the area where the additive molecules can be adsorbed onto the zinc alloy surface increases, resulting in a significant increase in coverage.

[0018] In the above formula (a), n and m each range from 3 to 7. The sum of n and m ranges from 6 to 14. n and m may each range from 3 to 5. It is preferable that the absolute value of the difference between n and m is small. The absolute value of the difference between n and m may be 2 or less, or 1 or less.

[0019] In the above formula (a), the following conditions (1) and / or (2) may be satisfied: (1) n and m are equal, and (2) n and m are each in the range of 3 to 5.

[0020] By making n and m equal, hydrogen gas generation during overdischarge can be particularly suppressed. This is thought to be because increasing the symmetry of the molecule makes it easier for additive (A) to adsorb to the newly formed surface of the zinc alloy. Also, when n and m are each in the range of 3 to 5, additive (A) also easily adsorbs to the newly formed surface of the zinc alloy, making it possible to particularly suppress hydrogen gas generation during overdischarge.

[0021] In formula (a), n and m may each be 3. By making n=m=3, it is possible to particularly suppress the generation of hydrogen gas during overdischarge.

[0022] The ratio Wa / Wz of the mass Wa of the additive (A) in the electrolyte to the mass Wz of the zinc alloy particles in the negative electrode is 50 ppm (50 × 10 －６ ) or more, 100 ppm or more, or 500 ppm or more, and may be 2000 ppm or less, 1500 ppm or less, 1000 ppm or less, or 800 ppm or less. The mass Wz of the zinc alloy particles is the total mass of all zinc alloy particles contained in the negative electrode. The mass Wa of the additive (A) is the total mass of the additive (A) in all the electrolyte solutions present in the battery housing. The mass of the additive (A) adsorbed to the zinc alloy particles is also included in the mass Wa as the additive (A) in the electrolyte solution (the same applies to the additive (B) described below). The ratio Wa / Wz is 100 ppm (100 × 10 －６ )~1000ppm (1000×10 －６ ) (for example, in the range of 500 ppm to 1000 ppm). The ratio Wa / Wz and the ratio Wb / Wz described below are ratios in the alkaline battery before use. The ratios Wa / Wz and Wb / Wz may be determined from the mass ratios of materials used in manufacturing the alkaline battery.

[0023] The alkaline dry battery (AB) according to the present disclosure includes a positive electrode, a negative electrode, a separator, and an electrolyte, and may include other components as needed. Components other than the additive (A) may be those used in known alkaline dry batteries. Examples of the components of the alkaline dry battery (AB) other than the additive (A) are described below, but the components of the alkaline dry battery (AB) are not limited to these examples.

[0024] (Positive Electrode) The positive electrode contains a positive electrode active material and, if necessary, further contains other additives (such as a binder and a conductive material). The positive electrode can be formed by pressure-molding a positive electrode mixture into a cylindrical body (positive electrode pellet). The positive electrode mixture contains, for example, a positive electrode active material, a conductive material, and an alkaline electrolyte, and, if necessary, further contains a binder. After being housed in a battery case, the positive electrode pellet may be pressed so as to adhere to the wall of the battery case. The alkaline electrolyte used to prepare the positive electrode may or may not contain the additive (A) described above.

[0025] Manganese dioxide can be used as the positive electrode active material. A preferred example of manganese dioxide is electrolytic manganese dioxide, but natural manganese dioxide or chemical manganese dioxide may also be used. The crystal structure of manganese dioxide can be α-type, β-type, γ-type, δ-type, ε-type, η-type, λ-type, or ramsdellite-type.

[0026] The manganese dioxide powder may have an average particle size (D50) in the range of 25 μm to 60 μm, which facilitates filling of the positive electrode and diffusibility of the electrolyte within the positive electrode. In this specification, the average particle size refers to the median diameter (D50) at which the cumulative volume reaches 50% in a volume-based particle size distribution. The median diameter can be determined, for example, using a laser diffraction / scattering particle size distribution analyzer.

[0027] From the viewpoint of moldability and suppression of expansion of the positive electrode, the BET specific surface area of ​​manganese dioxide is, for example, 20 m 2 / g to 50m 2 The BET specific surface area can be measured, for example, by using a specific surface area measuring device based on a nitrogen adsorption method.

[0028] The conductive material may 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 may be in powder form. The average particle size (D50) of the conductive material may be in the range of 3 μm to 20 μm. The content of the conductive material in the positive electrode may be in the range of 3 parts by mass to 10 parts by mass (for example, in the range of 5 parts by mass to 9 parts by mass) per 100 parts by mass of manganese dioxide.

[0029] A silver compound may be added to the positive electrode to absorb hydrogen generated inside the battery. Examples of silver compounds include silver oxide (Ag ２ O, AgO, Ag ２ O ３ etc.), silver-nickel composite oxide (AgNiO ２ ) etc.

[0030] (Negative Electrode) The negative electrode contains zinc alloy particles (zinc alloy powder) as a negative electrode active material. From the viewpoint of corrosion resistance, the zinc alloy may contain at least one selected from the group consisting of 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 viewpoint 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.

[0031] The zinc alloy powder may have an average particle size (D50) in the range of 100 μm to 200 μm (for example, in the range of 110 μm to 160 μm) from the viewpoint of the filling property of the negative electrode and the diffusibility of the electrolyte in the negative electrode.

[0032] The negative electrode may be a gelled negative electrode, which can be produced, for example, by mixing negative electrode active material particles, a gelling agent, and an alkaline electrolyte.

[0033] The gelling agent may be a known gelling agent used in the field of alkaline batteries. For example, a water-absorbent polymer may be used as the gelling agent. Examples of gelling agents include polyacrylic acid and sodium polyacrylate. The amount of gelling agent may be in the range of 0.5 to 2.5 parts by mass per 100 parts by mass of the negative electrode active material.

[0034] To the negative electrode, an additive such as a surfactant may be added to enhance the reaction efficiency on the surface of the negative electrode active material. Examples of the surfactant include polyoxyalkylene group-containing compounds and phosphate esters. From the viewpoint of dispersing the additive more uniformly in the negative electrode, it is preferable to add the additive in advance to the alkaline electrolyte used to prepare the negative electrode. The above-mentioned additive (A) may or may not be added to the alkaline electrolyte used to prepare the negative electrode.

[0035] To improve corrosion resistance, a compound containing a metal with a high hydrogen overvoltage, such as indium or bismuth, may be added to the negative electrode as appropriate.

[0036] (Negative Electrode Current Collector) The alkaline dry battery (AB) may include a negative electrode current collector inserted into the negative electrode. The material of the negative electrode current collector may be a metal (single metal or alloy). The material of the negative electrode current collector preferably contains copper, and may also be an alloy containing copper and zinc (e.g., brass). The negative electrode current collector may be plated, for example with tin, as necessary.

[0037] (Separator) The separator prevents short-circuiting between the positive electrode and the negative electrode. An insulating porous sheet can be used as the separator. For example, a nonwoven fabric primarily composed of fibers or a microporous film made of resin can be used as the separator. Examples of fiber materials include cellulose, rayon, polyvinyl alcohol, etc. The nonwoven fabric may be formed by blending cellulose fibers and polyvinyl alcohol fibers, or may be formed by blending rayon fibers and polyvinyl alcohol fibers. Examples of microporous film materials include resins such as cellophane and polyolefin. The thickness of the separator may be in the range of 200 μm to 300 μm. The separator may be formed by stacking multiple porous sheets. Alternatively, the separator may be formed by wrapping a single porous sheet twice or more (for example, twice).

[0038] (Electrolyte) As the electrolyte (alkaline electrolyte), for example, an alkaline aqueous solution containing potassium hydroxide is used. The concentration of potassium hydroxide in the alkaline electrolyte is preferably in the range of 30 to 50 mass % (for example, in the range of 30 to 40 mass %). The alkaline electrolyte may contain lithium hydroxide (LiOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), etc.

[0039] As described above, the additive (A) is added to the electrolyte solution. The additive (A) can be added to the electrolyte solution by dissolving it in the electrolyte solution. The electrolyte solution may contain additives other than the additive (A) (such as a surfactant). The use of a surfactant can improve the dispersibility of the negative electrode active material particles. The surfactant may be one of those exemplified for the negative electrode. The content of the surfactant in the alkaline electrolyte is typically in the range of 0 to 0.5% by mass (for example, 0 to 0.2% by mass).

[0040] The electrolytic solution may further contain an additive (B). The additive (B) is a compound containing a hydrocarbon group and an amino group bonded to the hydrocarbon group. The additive (B) may also be a compound containing a hydrocarbon group, an amino group bonded to the hydrocarbon group, and a hydroxyl group bonded to the hydrocarbon group. The number of carbon atoms in the hydrocarbon group is preferably in the range of 1 to 4 (e.g., in the range of 2 to 3). The hydrocarbon group may be a saturated hydrocarbon group or a linear saturated hydrocarbon group. The additive (B) may also be a compound represented by the following formula (b):

[0041] (In formula (b), R １ is an alkylene group having 1 to 4 carbon atoms (e.g., 2 to 3 carbon atoms).

[0042] In formula (b), R １ is an ethylene group (-CH ２ -CH ２ That is, the additive (B) may be 2-aminoethanol (H ２ N-CH ２ -CH ２ —OH).

[0043] Additive (B) contains a highly polar amino group, which strongly interacts with the charge on the zinc alloy surface and adsorbs to the zinc alloy surface, which is thought to be why it can cover the exposed surface of the zinc alloy that cannot be covered by additive (A).

[0044] The ratio Wb / Wz of the mass Wb of the additive (B) in the electrolyte to the mass Wz of the zinc alloy particles in the negative electrode may be in the range of 20 ppm to 200 ppm (e.g., 50 ppm to 150 ppm). By setting the ratio Wb / Wz to 20 ppm or more (e.g., 50 ppm or more), hydrogen gas generation can be particularly suppressed. On the other hand, since the amino group contains hydrogen atoms, the ratio Wb / Wz is preferably 200 ppm or less (e.g., 150 ppm or less). The additive (B) may or may not be added to the electrolyte used to prepare the electrodes (positive electrode, negative electrode).

[0045] (Battery Housing) The battery housing is composed of a battery case and a sealing body that seals the opening of the battery case. The sealing body is composed of a negative electrode terminal plate and a gasket. The battery case has a cylindrical shape with a bottom. The negative electrode terminal plate has a roughly disk-like shape. For example, a nickel-plated steel plate is used for the metal case. To reduce the contact resistance between the positive electrode and the battery case, the inner surface of the battery case may be coated with a carbon film. The negative electrode terminal plate can be made of the same material as the metal case, for example, a nickel-plated steel plate. The negative electrode terminal plate functions as the negative electrode terminal. The battery case functions as the positive electrode terminal.

[0046] Examples of the gasket material include polyamide, polyethylene, polypropylene, polyphenyl ether, polyphenylene ether, etc. From the viewpoint of corrosion resistance to alkaline electrolyte, the gasket material is preferably polyamide-6,6, polyamide-6,10, polyamide-6,12, or polypropylene.

[0047] (Method for manufacturing alkaline dry battery (AB)) The method for manufacturing the alkaline dry battery (AB) is not particularly limited. The alkaline dry battery (AB) may be manufactured by a known method, except for adding the additive (A) to the electrolyte solution. For example, the alkaline dry battery (AB) may be manufactured by the procedure described in the examples below.

[0048] An example of an embodiment according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the alkaline dry battery of the example described below. Furthermore, the components of the alkaline dry battery of the example described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment.

[0049] (Embodiment 1) Fig. 1 shows a partially exploded cross-sectional view of an alkaline dry battery 10 according to Embodiment 1. The alkaline dry battery 10 is a cylindrical battery having an inside-out structure. The alkaline dry battery 10 includes a battery case 1 and, disposed within the battery case 1, a positive electrode 2, a negative electrode (gelled negative electrode) 3, a separator 4, a sealing unit 9, and an electrolyte (not shown). The electrolyte includes the additive (A) described above.

[0050] The battery case 1 is a cylindrical case with a bottom and functions as a positive electrode terminal. The positive electrode 2 has a cylindrical shape with a hollow portion in the center. The positive electrode 2 is disposed so as to contact the inner wall of the battery case 1. In the example shown in FIG. 1 , the positive electrode 2 is formed by stacking two cylindrical positive electrode pellets.

[0051] The separator 4 is composed of a cylindrical portion 4a and a bottom portion 4b that closes one end of the cylindrical portion 4a. The cylindrical portion 4a is disposed along the inner surface of the hollow portion of the positive electrode 2, separating the positive electrode 2 from the negative electrode 3. The bottom portion 4b is disposed at the bottom of the hollow portion of the positive electrode 2, separating the negative electrode 3 from the battery case 1.

[0052] The opening of the battery case 1 is sealed by a gasket 5 and a negative electrode terminal plate 7 of 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. The negative electrode terminal plate 7 functions as a negative electrode terminal. The negative electrode current collector 6 has a nail shape with a head and a body. The negative electrode current collector 6 contains, for example, copper, and may be made of an alloy containing copper and zinc, such as brass. The negative electrode current collector 6 may be plated with tin or other plating as necessary. The body of the negative electrode current collector 6 is inserted into a 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.

[0053] 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. Most of the outer surface of the battery case 1 is covered with an exterior label 8. The battery case 1, gasket 5, and negative electrode terminal plate 7 constitute a battery housing. The positive electrode 2, negative electrode 3, separator 4, and electrolyte (not shown) are disposed within the battery case 1. The gasket 5 in FIG. 1 has an annular thin-walled portion 5a.

[0054] (Additional Notes) The above description discloses the following technologies: (Technology 1) An alkaline dry battery comprising: a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode contains zinc alloy particles as a negative electrode active material, and the electrolyte contains an additive represented by the following formula (a): (In formula (a), n is a natural number of 3 or more and 7 or less, and m is a natural number of 3 or more and 7 or less) (Technology 2) The alkaline dry battery according to Technology 1, wherein in formula (a), n and m are equal. (Technology 3) The alkaline dry battery according to Technology 1 or 2, wherein in formula (a), n and m each fall within the ranges of 3 to 5. (Technology 4) The alkaline dry battery according to any one of Technology 1 to 3, wherein a ratio Wa / Wz of a mass Wa of the additive in the electrolyte solution to a mass Wz of the zinc alloy particles in the negative electrode falls within the range of 100 ppm to 1000 ppm.

[0055] The alkaline dry battery of the present disclosure will be described in further detail with reference to examples.

[0056] (Experiment 1) In Experiment 1, a plurality of alkaline dry batteries containing different electrolyte solutions were fabricated and evaluated.

[0057] Battery A1 was fabricated according to the following steps (1) to (4). (1) Preparation of Electrolyte (Alkaline Electrolyte) An alkaline aqueous solution containing potassium hydroxide (concentration 33% by mass), zinc oxide (concentration 2% by mass), and additive (A) represented by formula (a) was prepared as the alkaline electrolyte. A compound in which n = m = 3 in formula (a) was used as additive (A). Additive (A) was added so that the ratio W / Wz of the mass of the additive W to the mass Wz of the zinc alloy particles (negative electrode active material) was the value shown in Table 1.

[0058] (2) Preparation of Positive Electrode Manganese dioxide (positive electrode active material) and graphite (conductive material) were mixed to obtain a mixture. They were mixed at a mass ratio of manganese dioxide:graphite = 100:6. For the manganese dioxide, electrolytic manganese dioxide powder (average particle size: 40 μm) was used. For the graphite, graphite powder (average particle size (D50): 8 μm) was used.

[0059] The electrolyte solution was added to the mixture, thoroughly stirred, and then compression-molded into flakes to obtain a positive electrode mixture. The mass ratio of the mixture to the electrolyte solution was 100:1.5. The electrolyte solution used was the same as the alkaline electrolyte solution prepared in (1) above, except that the additive (A) was not added.

[0060] Next, the flake-like positive electrode mixture was crushed into granules, which were then classified using a 10-100 mesh sieve to obtain granules. The obtained granules were pressure-molded into a hollow cylindrical shape (height 10.8 mm) to obtain positive electrode pellets. Four such positive electrode pellets were produced.

[0061] (3) Preparation of Negative Electrode A negative electrode active material, an electrolyte, and a gelling agent were mixed to obtain a gelled negative electrode. The electrolyte was the same as the alkaline electrolyte prepared in (1) above, except that additive (A) was not added. The negative electrode active material was a powdered zinc alloy (average particle size: 130 μm) containing 0.02 mass% indium, 0.01 mass% bismuth, and 0.005 mass% aluminum. The gelling agent was a mixture of cross-linked branched polyacrylic acid and highly cross-linked chain sodium polyacrylate. The mass ratio of the negative electrode active material, electrolyte, and gelling agent in the gelled negative electrode was negative electrode active material:electrolyte:gelling agent = 100:50:1.

[0062] (4) Assembly of Battery A1 Using the above components, an alkaline dry battery was assembled as follows. The battery assembly procedure is described with reference to FIG. 1 . First, a coating agent (product name: Bunny Height) manufactured by Nippon Graphite Co., Ltd. was applied to the inner surface of a bottomed cylindrical case made of nickel-plated steel sheet to form a carbon coating approximately 10 μm thick, thereby obtaining a battery case 1. Next, four positive electrode pellets were inserted vertically into the battery case 1 and pressed to form a positive electrode 2 in close contact with the inner wall of the battery case 1. Next, a separator 4 was placed inside the positive electrode 2. The separator 4 was a nonwoven fabric sheet made primarily of rayon fiber and polyvinyl alcohol fiber. Next, the alkaline electrolyte prepared in (1) above was poured into the inside of the separator 4, allowing it to impregnate. This state was left for a predetermined time, allowing the alkaline electrolyte to permeate through the separator 4 into the positive electrode 2. Then, a gelled negative electrode 3 was filled inside the separator 4.

[0063] The negative electrode current collector 6 was formed by pressing ordinary brass into a nail shape and then tin-plating the surface. The head of the negative electrode current collector 6 was electrically welded to a negative electrode terminal plate 7 made of nickel-plated steel. The body of the negative electrode current collector 6 was then press-fitted into the central through-hole of a gasket 5 made primarily of polyamide-6,12. In this way, a sealing unit 9 consisting of the gasket 5, negative electrode current collector 6, and negative electrode terminal plate 7 was produced.

[0064] Next, the sealing unit 9 was placed in the opening of the battery case 1. At this time, the body of the negative electrode current collector 6 was inserted into the negative electrode 3. Next, the opening edge of the battery case 1 was crimped to the peripheral edge of the negative electrode terminal plate 7 so as to sandwich the gasket 5, thereby sealing the opening of the battery case 1. In this way, the positive electrode 2, the negative electrode 3, the separator 4, and the alkaline electrolyte were placed in the battery housing.

[0065] Next, the outer surface of the battery case 1 was covered with an exterior label 8. In this manner, a battery A1 (alkaline dry battery) was produced.

[0066] (Batteries A2 to A7, Batteries C1 to C6) Batteries A2 to A7 and Batteries C1 to C6 were fabricated by the same method and under the same conditions as those for fabricating Battery A1, except that the type and amount (ratio W / Wz) of additives added to the electrolyte were changed as shown in Table 1. In the fabrication of Battery C1, no additives were added to the electrolyte.

[0067] (Battery Evaluation) Two of the fabricated batteries A1 were connected in series, and a 10 Ω resistor was connected. Battery A1 was discharged until the total voltage of the two batteries dropped to 1.2 V. Next, the 10 Ω resistor was changed to a 1 Ω resistor, and the two batteries A1 were maintained in series for 36 hours. After that, a hole was drilled in the battery A1 that had undergone polarity inversion due to overdischarge, and the hydrogen gas accumulated inside the battery was collected and its volume (amount of hydrogen gas generated) was measured. Similar evaluations were performed on the other batteries.

[0068] The measurement results are shown in Table 1. In Table 1, the values ​​of n and m respectively represent the values ​​of n and m in formula (a). The ratio W / Wz shown in Table 1 represents the ratio of the mass W of the additives (compounds of formulas (a), (b), and (c)) in the electrolyte to the mass Wz of the zinc alloy particles. The amount of hydrogen gas generated V in Table 1 is a relative value when the amount of hydrogen gas generated in battery C1 is taken as 100. As shown in Table 1, additive (A) represented by formula (a) and additive (B) represented by formula (b) were added to the electrolyte of battery A7. Additive (B) represented by formula (b) contained 2-aminoethanol (H ２ N-CH ２ -CH ２ In the preparation of battery A7, the ratio Wa / Wz of the mass of additive (A) to Wz of the mass of zinc alloy particles was 500 ppm, and the ratio Wb / Wz of the mass of additive (B) to Wz of the mass of zinc alloy particles was 100 ppm. The additive added to the electrolyte solution of batteries C2 and C3 was a compound represented by the following formula (c). The additive added to the electrolyte solution of battery C4 was 2-aminoethanol (H ２ N-CH ２ -CH ２ -OH) was used.

[0069]

[0070]

[0071] Batteries A1 to A7 are alkaline dry batteries (AB) according to the present disclosure. Batteries C1 to C6 are comparative examples. A lower amount of hydrogen gas generated V during overdischarge is preferable. As shown in Table 1, the amount of hydrogen gas generated V for batteries A1 to A7 was significantly smaller than the amount of hydrogen gas generated V for batteries C1 to C6. Thus, the alkaline dry batteries (AB) according to the present disclosure were able to suppress hydrogen gas generation during overdischarge.

[0072] Figure 2 shows the evaluation results for batteries A2, A4 to A6, and C5 to C6, which used the additive represented by formula (a) and had a W / Wz ratio of 500 ppm. The horizontal axis in Figure 2 represents the value of n + m. In Figure 2, the additives for batteries other than battery A4 were additives where n = m. As shown in Table 1 and Figure 2, when the value of n + m was in the range of 6 to 14, the amount of hydrogen gas generated V was smaller when n = m. When n = m and n and m were each in the range of 3 to 5, the amount of hydrogen gas generated V was even smaller. When n = m = 3, the amount of hydrogen gas generated V was particularly small.

[0073] As is clear from the comparison between Battery A2 and Battery A7, the generation of hydrogen gas during overdischarge was particularly suppressed by adding Additive (A) and Additive (B) to the electrolyte solution.

[0074] The present disclosure is applicable to alkaline dry batteries. While the present invention has been described with reference to presently preferred embodiments, such disclosure should not be construed as limiting. Various modifications and variations will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Therefore, the appended claims should be construed to cover all modifications and variations that do not depart from the true spirit and scope of the present invention.

[0075] 2: Positive electrode 3: Negative electrode 4: Separator 5: Gasket 6: Negative electrode current collector 7: Negative electrode terminal plate 9: Sealing unit 10: Alkaline dry battery

Claims

1. An alkaline dry battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode contains zinc alloy particles as a negative electrode active material, and the electrolyte contains an additive represented by the following formula (a): (In formula (a), n is a natural number of 3 or more and 7 or less, and m is a natural number of 3 or more and 7 or less.) 2. The alkaline dry battery according to claim 1, wherein in formula (a), n and m are equal.

3. The alkaline dry battery according to claim 1 or 2, wherein in said formula (a), said n and said m are each in the range of 3 to 5.

4. The alkaline dry battery according to claim 1 or 2, wherein the ratio Wa / Wz of the mass Wa of the additive in the electrolyte to the mass Wz of the zinc alloy particles in the negative electrode is in the range of 100 ppm to 1000 ppm.