Alkaline dry battery

Abstract

The present disclosure provides an alkaline dry battery that can suppress the occurrence of internal short-circuiting during medium-load intermittent discharge. An alkaline dry battery according to the present disclosure comprises a hollow tubular positive electrode (2) that is provided in a battery case (1), a gel-like negative electrode (3) that is filled in a hollow part of the positive electrode (2), and a separator (4) that is disposed between the positive electrode (2) and the negative electrode (3), wherein the negative electrode (3) contains a zinc powder and a surfactant. The negative electrode (3) further contains a sulfate in the range of 0.01-0.5 mass%, in terms of sulfuric acid ions with respect to the mass of the negative electrode.

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 typically include a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an alkaline electrolyte. The positive electrode contains manganese dioxide as a positive electrode active material. Various proposals have been made to improve the performance of alkaline batteries.

[0003] Patent Document 1 discloses an alkaline battery equipped with a negative electrode gel containing zinc or a zinc alloy as the negative electrode active material, in which a linear polyoxyethylene-alkyl ether is added as a surfactant to the negative electrode gel. The surfactant adsorbs to zinc or zinc alloy particles (zinc particles) in the negative electrode gel, preventing corrosion of the zinc due to contact with the electrolyte. As a result, the alkaline battery described in Patent Document 1 is said to be able to improve leakage resistance while maintaining discharge performance.

[0004] Patent Document 2 proposes that in an alkaline battery having a positive electrode, a negative electrode containing zinc, and an electrolyte, a calcium compound or a sulfate compound is added to at least one of the positive electrode, the negative electrode, and the electrolyte to prevent a decrease in discharge voltage under heavy load discharge conditions. According to Patent Document 2, sulfate ions are converted into H ２ Since the electrolyte migrates toward the negative electrode while carrying O with it, the volume of the electrolyte near the negative electrode becomes sufficient even under heavy load discharge conditions, and a decrease in discharge voltage is suppressed.

[0005] JP 2017-69097 A JP 2001-297776 A

[0006] In alkaline batteries, zinc ions are generated during discharge. These zinc ions exist dissolved in the electrolyte in the form of zincate ions. The zincate ions precipitate as zinc oxide in the negative electrode. However, repeated intermittent discharge at medium loads can cause some of the zinc ions that do not dissolve to precipitate as zinc oxide in the separator, potentially causing an internal short circuit.

[0007] One aspect of the present disclosure relates to an alkaline dry battery including a hollow cylindrical positive electrode disposed in a battery case, a gelled negative electrode filled in the hollow portion of the positive electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the negative electrode contains zinc powder and a surfactant, and the negative electrode further contains a sulfate in a range of 0.01 to 0.5 mass % in terms of sulfate ions relative to the mass of the negative electrode.

[0008] According to the present disclosure, the occurrence of an internal short circuit during medium-load intermittent discharge can be suppressed.

[0009] 1 is a partially exploded cross-sectional view showing an example of an alkaline dry battery according to an embodiment.

[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 more 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 equal to or greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more of the materials may be used in combination.

[0011] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0012] (Alkaline dry battery) The alkaline dry battery according to this embodiment is an alkaline dry battery including a hollow cylindrical positive electrode disposed in a battery case, a gel-like negative electrode containing zinc powder filled in the hollow portion of the positive electrode, and a separator disposed between the positive electrode and the negative electrode. The negative electrode contains zinc powder and a surfactant. The zinc powder includes zinc alloy powder. From the viewpoint of preventing environmental pollution, the zinc alloy is preferably a mercury-free zinc alloy.

[0013] The surfactant contained in the negative electrode adheres to the surface of the zinc powder, suppressing side reactions (e.g., reductive decomposition of water) that occur when the zinc powder comes into contact with the electrolyte, and thus improving leakage resistance. By incorporating a surfactant into the negative electrode, an alkaline dry battery with excellent leakage resistance can be realized while maintaining discharge performance.

[0014] On the other hand, during discharge, zinc ions are generated. Zinc ions are generated in the electrolyte by the reaction shown in the following formula 1, for example, tetrahydroxyzincate (II) ions ([Zn(OH) ４ ] ２－ (hereinafter, simply referred to as "zincate ions" or "zinc ions"). These zincate ions are usually present near the surface of the zinc powder in the negative electrode and dissolved in the electrolyte. During discharge or when discharge is stopped, the zincate ions can be precipitated in the form of zinc oxide on the surface of the zinc particles of the negative electrode through the reaction shown in Formula 2 below.

[0015] Formula 1: Zn+4OH － ⇒ [Zn(OH) ４ ] ２－ + 2e － Formula 2: [Zn(OH) ４ ] ２－ ⇒ ZnO + 2OH － + 2H ２However, when a surfactant is present, the surfactant adsorbs onto the zinc surface, which may inhibit the phenomenon of zinc oxide deposition on the zinc surface during discharge or when discharge is stopped. In addition, the presence of a surfactant may localize the discharge reaction, causing localized deposition of zinc oxide. As a result, it has been found that with repeated medium-load intermittent discharge, zincate ions that are no longer dissolved in the electrolyte become zinc oxide and deposit on the separator, growing to penetrate the separator and causing an internal short circuit.

[0016] In other words, alkaline batteries that have surfactants added to the negative electrode to improve leakage resistance are prone to having a shorter discharge duration due to abnormal discharge caused by an internal short circuit when used in an environment where they are repeatedly discharged intermittently under medium load.

[0017] The negative electrode contains a sulfate. By including the sulfate in the negative electrode, internal short circuits due to zinc oxide precipitation are suppressed in a medium-load intermittent discharge environment. This allows for the realization of an alkaline dry battery with excellent medium-load intermittent discharge characteristics. The content of the sulfate in the negative electrode may be in the range of 0.01 to 0.5 mass % in terms of sulfate ions relative to the mass of the negative electrode.

[0018] The deposition of zinc oxide occurs when the OH of the electrolyte in the negative electrode is released by discharging. － This is thought to be due to the fact that zinc ions are consumed, the pH of the electrolyte drops, and the electrolyte becomes neutral, which reduces the solubility of zinc ions dissolved in the electrolyte. In particular, in an operating environment where the current is a medium load of about 250 mA to 500 mA and discharge is repeated intermittently for about one hour per day, the pH of the electrolyte drops significantly locally, making the electrolyte more likely to become neutral locally, and as a result, an internal short circuit due to the precipitation of zinc oxide is more likely to occur.

[0019] In undischarged alkaline batteries, the electrolyte is strongly alkaline, so sulfates added to the negative electrode are difficult to dissolve in the electrolyte. However, as the pH of the electrolyte in the negative electrode decreases with discharge, sulfates become more soluble, further lowering the pH of the electrolyte to the acidic side. Meanwhile, zinc ions have the lowest solubility in neutral conditions and are easily soluble in alkaline and acidic conditions. Therefore, as sulfates dissolve during medium-load intermittent discharge, the pH of the electrolyte shifts from neutral to acidic, making zinc ions more soluble and suppressing the deposition of zinc oxide.

[0020] Under heavy load (e.g., about 1 A) discharge conditions, alkaline batteries typically experience a drop in discharge voltage and reach the end of their life before the electrolyte becomes neutral, making it unlikely that internal short circuits will occur due to the deposition of zinc oxide.

[0021] The sulfate content of the negative electrode, calculated as sulfate ions, is 0.01% by mass or more relative to the mass of the negative electrode, so that the effect of suppressing internal short circuits due to zinc oxide precipitation is sufficiently obtained. On the other hand, an excessive sulfate content increases the unevenness of the sulfate distribution within the negative electrode, which increases the unevenness of the pH of the electrolyte within the negative electrode during discharge, which may actually promote internal short circuits. To suppress unevenness in the pH of the electrolyte, the sulfate content should be 0.5% by mass or less relative to the mass of the negative electrode, calculated as sulfate ions. The sulfate content may be 0.01% by mass or more and 0.5% by mass or less, 0.05% by mass or more and 0.3% by mass or less, or 0.05% by mass or more and 0.2% by mass or less, and more preferably 0.05% by mass or more and 0.15% by mass or less.

[0022] Here, the content of sulfate salt converted into sulfate ions refers to the content of sulfate ions (SO ) among the cations and sulfate ions that constitute the sulfate salt contained in the negative electrode. ４ ２－ The sulfate content is determined by disassembling an undischarged alkaline battery, collecting at least a portion (e.g., 80% or more) of the negative electrode, measuring its mass, exposing the collected negative electrode to pure water to dissolve the sulfate in the pure water, and then performing ion chromatography. ４ ２－The sulfate content converted into sulfate ions can be determined by quantifying the amount of sulfate and calculating the mass of the negative electrode.

[0023] The cation constituting the sulfate is not particularly limited as long as it does not interfere with the discharge reaction of the battery. The sulfate may be a salt of a metal cation and a sulfate ion. In terms of the significant effect of lowering the pH after dissolution, the sulfate preferably includes at least one selected from the group consisting of potassium sulfate, sodium sulfate, aluminum sulfate, aluminum potassium sulfate, calcium sulfate, zinc sulfate, and lithium sulfate, and also preferably includes a hydrate thereof.

[0024] The sulfate may be added to the separator in addition to the negative electrode. By including the sulfate in the separator, internal short circuits due to zinc oxide precipitation are further suppressed in a medium-load intermittent discharge environment, and an alkaline dry battery with excellent medium-load intermittent discharge characteristics can be realized. As described above, internal short circuits due to zinc oxide precipitation occur when the electrolyte in the separator shifts to the neutral side, so it is effective if sulfate, which affects the pH of the electrolyte, is also present in the separator.

[0025] The content of sulfate in the separator is, for example, 1 cm 2 in the region where the positive electrode and the negative electrode face each other in order to obtain a sufficiently high effect of suppressing internal short circuits. ２ On the other hand, the content of sulfate is preferably 0.08 mg or more in terms of sulfate ions per square centimeter of facing area of ​​1 cm. ２ Preferably, the amount is 1.7 mg or less in terms of sulfate ions per facing area of ​​1 cm. ２ The content of sulfate per cm is the content of sulfate per cm of a separator when a single separator is used in the region where the positive electrode and the negative electrode face each other. ２ On the other hand, when a plurality of separators are stacked to obtain a desired total thickness, or when a single separator is wound around itself multiple times to obtain a desired total thickness, the sulfate content per square centimeter of the opposing surface area is 1 cm. ２The sulfate content per 1 cm of the separator in each layer is determined in the region where the positive electrode and the negative electrode face each other. ２ A separator containing a sulfate can be produced by, for example, (i) attaching a solid sulfate to the surface of the separator substrate, (ii) applying or impregnating a separator substrate sheet with a sulfate solution and then drying the sheet to precipitate the sulfate, or (iii) using a solution containing a sulfate when producing a separator substrate by a wet process.

[0026] (Surfactant) The surfactant is not particularly limited, and may be a nonionic surfactant, an anionic surfactant, or an amphoteric surfactant. The surfactant may be any of an ether type surfactant, an ester type surfactant, and an ester-ether type surfactant. The surfactant may be a -(OC ２ H ４ ) ｎ Those having a polyoxyethylene group represented by - are preferred.

[0027] The ether surfactant may be, for example, a polyoxyalkylene glycol (e.g., polyoxyethylene polyoxypropylene glycol), a nonionic surfactant in which an oxyalkylene group (e.g., ethylene oxide) is added to a hydrocarbon having a hydroxyl group (e.g., a polyoxyalkylene alkyl ether such as polyoxyethylene alkyl ether, or a polyoxyalkylene alkylphenyl ether such as polyoxyethylene alkylphenyl ether), etc. Examples of the hydrocarbon having a hydroxyl group include alcohol compounds and phenol compounds. Examples of alcohol compounds include linear alkyl alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, heneicosanol, docosanol, tricosanol, tetracosanol, pentacosanol, hexacosanol, heptacosanol, octacosanol, nonacosanol, and triacontanol; and linear alkyl alcohols such as isopropanol, isobutanol, isohexanol, 2-ethylhexanol, isononanol, isodecanol, isotridecanol, isotetradecanol, and isotridecanoic acid. Examples of suitable phenol compounds include branched alkyl alcohols such as acontanol, isohexadecanol, isoheptadecanol, isooctadecanol, isononadecanol, isoeicosanol, isoheneicosanol, isodocosanol, isotricosanol, isotetracosanol, isopentacosanol, isohexacosanol, isoheptacosanol, isooctacosanol, isononacosanol, and isopentadecanol; linear alkenyl alcohols such as tetradecenol, hexadecenol, heptadecenol, octadecenol, and nonadecenol; branched alkenyl alcohols such as isohexadecenol and isooctadecenol; cyclic alkyl alcohols such as cyclopentanol and cyclohexanol, and aromatic alcohols such as benzyl alcohol. Examples of suitable phenol compounds include phenol, alkylphenols, monostyrenated phenol, distyrenated phenol, and tristyrenated phenol.

[0028] The ester surfactant may be a nonionic surfactant having an ester bond between a polyhydric alcohol and a higher fatty acid. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2-ethyl-2-hydroxymethyl-1,3-propanediol, trimethylolpropane, sorbitan, pentaerythritol, sorbitol, glycerin, and sucrose. Examples of higher fatty acids include linear alkyl carboxylic acids such as octylic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid (stearic acid), nonadecanoic acid, eicosanoic acid, heneicosanoic acid, and docosanoic acid; branched alkyl carboxylic acids such as 2-ethylhexanoic acid, isododecanoic acid, isotridecanoic acid, isotetradecanoic acid, isohexadecanoic acid, and isooctadecanoic acid; and linear alkenyl carboxylic acids such as octadecenoic acid, octadecadienoic acid, octadecatrienoic acid, and oleic acid. Among these, oleic acid, stearic acid, lauric acid, and myristic acid are preferred. Examples of ester-type nonionic surfactants include polyglycerin fatty acid esters, polysorbitan fatty acid esters, and sucrose fatty acid esters.

[0029] Ester-ether surfactants have both ester and ether bonds in the molecule (e.g., fatty acid methyl ester ethoxylates). Examples of ester-ether surfactants include those in which ethylene oxide is added to an ester of a fatty acid with a polyhydric alcohol such as glycerin or sorbitol, fatty acid polyethylene glycol, and fatty acid polyoxyethylene sorbitan.

[0030] The ester surfactant or ester-ether surfactant may be an anionic surfactant having an ester bond between an alcohol and sulfuric acid or phosphoric acid. The alcohol may be the above-mentioned polyhydric alcohol, and may have at least one hydroxy group. The alcohol may have an ether group. The alcohol may have a -(OC ２ H ４ ) ｎ A compound having a polyoxyethylene group represented by - and having a hydroxy group added to the terminal thereof is preferred.

[0031] The surfactant may be, for example, an ether-type nonionic surfactant in which one end of a functional group having a polyoxyethylene group is terminated with a hydroxy group (—OH). The surfactant may be, for example, a surfactant in which one end of a functional group having a polyoxyethylene group is terminated with a phosphate ester group (—OPO ３ H ２ ) or a phosphate-type anionic surfactant in which one end of a functional group having a polyoxyethylene group is a sulfonate ester group (—OSO ３ The surfactant may be a sulfonic acid type anionic surfactant terminated with H).

[0032] More specifically, the surfactant has the general formula: R １ - (OC ２ H ４ ) ｎ The compound may be a compound represented by the formula -X. １ is a hydrocarbon group having 9 to 24 carbon atoms. X is a hydroxy group (-OH), a phosphate ester group (-OPO ３ H ２ ), or a sulfonate ester group (—OSO ３ H). Polyoxyethylene group (OC ２ H ４ ) ｎ The degree of polymerization n is in the range of 2 to 20. In this case, by using a negative electrode containing a surfactant, it is easy to obtain an alkaline dry battery that has excellent leakage resistance while maintaining high discharge performance. １ may have a carbon number in the range of 12 to 24. The degree of polymerization n may be in the range of 3 to 20.

[0033] The content of the surfactant in the negative electrode is preferably in the range of 10 ppm to 500 ppm relative to the total mass of the negative electrode, which allows for both the improvement in leakage resistance due to the addition of the surfactant and the suppression of internal short circuits due to the addition of the sulfate, thereby achieving an alkaline dry battery that has excellent leakage resistance while maintaining medium-load intermittent discharge performance.

[0034] The surfactant content of the negative electrode is determined by disassembling an undischarged alkaline battery, extracting at least a portion (e.g., 80% or more) of the negative electrode, measuring its mass, exposing the extracted negative electrode to chloroform, drying the components extracted in the chloroform under a nitrogen purge, and redissolving the dried product in acetonitrile and analyzing the solution using a liquid chromatography mass spectrometer (LC / MS). For example, a ZMD mass spectrometer (Micromass) equipped with a high-performance liquid chromatograph Alliance 2690 (Waters) can be used as the LC / MS.

[0035] Examples of components of alkaline dry batteries according to the present disclosure are described in detail below.

[0036] (Positive Electrode) The positive electrode contains manganese dioxide as a positive electrode active material. The positive electrode usually contains a positive electrode active material and a conductive material, and further contains a binder as needed. The positive electrode may 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 further contains a binder as needed. After being housed in the case body, the cylindrical body may be pressed so as to adhere to the inner wall of the case body.

[0037] A preferred example of manganese dioxide as a positive electrode active material is electrolytic manganese dioxide, but natural manganese dioxide or chemical manganese dioxide may 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] (Negative Electrode) The negative electrode contains 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.

[0043] The average particle size (D50) of the zinc alloy powder may be in the range of 100 μm to 200 μm (e.g., 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. In this specification, the average particle size refers to the median diameter (D50) at which the cumulative volume is 50% in the volume-based particle size distribution. The median diameter can be determined, for example, using a laser diffraction / scattering particle size distribution analyzer.

[0044] The negative electrode includes a 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, the gelling agent, the surfactant, the sulfate, and the electrolyte. In order to more uniformly disperse the additives (gelling agent, surfactant, etc.) in the negative electrode, the additives may be added in advance to the electrolyte used to prepare the negative electrode. The electrolyte may be an alkaline electrolyte, as described below.

[0045] 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.

[0046] (Negative Electrode Current Collector) The alkaline dry battery of the present disclosure 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 needed.

[0047] (Separator) As the separator, a nonwoven fabric mainly made of fiber or a microporous film made of resin is used. Examples of fiber materials include cellulose, polyvinyl alcohol, etc. The nonwoven fabric may be formed by blending cellulose fiber and polyvinyl alcohol fiber, or may be formed by blending rayon fiber and polyvinyl alcohol fiber. Examples of microporous film materials include resins such as cellophane and polyolefin. When the separator is thin, multiple separators may be stacked to adjust the thickness to the above-mentioned range.

[0048] (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 also contain zinc oxide.

[0049] The alkaline electrolyte may contain a surfactant. Use of the surfactant can improve the dispersibility of the negative electrode active material particles. The surfactant may be any of those exemplified for the negative electrode. The content of the surfactant in the alkaline electrolyte is typically in the range of 0.001 to 0.5 mass % (for example, in the range of 0.002 to 0.2 mass %).

[0050] (Battery Housing) There are no particular limitations on the battery housing, and a housing appropriate for the shape of the battery may be used. There are no particular limitations on the shape of the alkaline dry battery according to this embodiment, and it may be cylindrical or coin-shaped (including button-shaped). The battery housing typically includes a battery case, a negative electrode terminal plate, and a gasket. For example, a cylindrical metal case with a bottom is used as the battery case. For example, a nickel-plated steel plate is used as the metal case. In order 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 may be formed from the same material as the metal case, for example, a nickel-plated steel plate.

[0051] Examples of gasket materials 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. Note that the gasket usually has an annular thin-walled portion.

[0052] 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.

[0053] 1 shows a partially exploded cross-sectional view of an alkaline battery 10 with an inside-out structure according to an embodiment of the present disclosure. The cylindrical alkaline battery 10 includes a battery case 1, and a positive electrode 2, a negative electrode (gelled negative electrode) 3, a separator 4, and an electrolyte (not shown) disposed within the battery case 1.

[0054] The battery case 1 is a cylindrical case with a bottom and functions as a positive electrode terminal. The positive electrode 2 is hollow and cylindrical, and is disposed so as to contact the inner wall of the battery case 1. The negative electrode 3 is disposed in the hollow portion of the positive electrode 2. The separator 4 is disposed between the positive electrode 2 and the negative electrode 3. The negative electrode has the above-mentioned characteristics.

[0055] The separator 4 is composed of a cylindrical separator 4a and a bottom paper 4b. The separator 4a is arranged 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 paper 4b is arranged at the bottom of the hollow portion of the positive electrode 2, separating the negative electrode 3 from the battery case 1.

[0056] 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 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. The gasket 5 has an annular thin-walled portion 5a.

[0057] 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 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 alkaline electrolyte (not shown) are disposed within the battery housing.

[0058] There are no particular limitations on the method for assembling the alkaline dry battery 10, and conventional techniques can be applied as needed.

[0059] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0060] (Technology 1) An alkaline dry battery comprising: a hollow cylindrical positive electrode disposed in a battery case; a gelled negative electrode filled in the hollow portion of the positive electrode; and a separator disposed between the positive electrode and the negative electrode, wherein the negative electrode contains zinc powder and a surfactant, and the negative electrode further contains a sulfate in a range of 0.01 to 0.5 mass % in terms of sulfate ions relative to the mass of the negative electrode.

[0061] (Technology 2) The alkaline dry battery according to Technology 1, wherein the sulfate salt includes at least one selected from the group consisting of potassium sulfate, sodium sulfate, aluminum sulfate, aluminum potassium sulfate, calcium sulfate, zinc sulfate, lithium sulfate, and hydrates thereof.

[0062] (Technique 3) The surfactant is -(OC ２ H ４ ) ｎ 3. The alkaline dry battery according to claim 1, wherein the alkaline dry battery has a polyoxyethylene group represented by the formula:

[0063] (Technology 4) The alkaline dry battery according to Technology 3, wherein the surfactant is a nonionic surfactant having a hydroxyl group (—OH).

[0064] (Technology 5) The alkaline dry battery according to Technology 3, wherein the surfactant is a phosphate-type anionic surfactant having a phosphate ester group.

[0065] (Technology 6) The alkaline dry battery according to Technology 3, wherein the surfactant is a sulfonic acid type anionic surfactant having a sulfonate ester group.

[0066] (Technology 7) The surfactant is represented by the general formula: R １ - (OC ２ H ４ ) ｎ -X, and R １ is a hydrocarbon group having 9 to 24 carbon atoms, and X is a hydroxy group (-OH), a phosphate ester group (-OPO ３ H ２ ), or a sulfonate ester group (—OSO ３ H), and a polyoxyethylene group (OC ２ H ４ ) ｎ 7. The alkaline dry battery according to any one of claims 3 to 6, wherein the degree of polymerization n is in the range of 2 to 20.

[0067] (Technology 8) The alkaline dry battery according to any one of Technologies 1 to 7, wherein the content of the surfactant contained in the negative electrode is in the range of 10 ppm to 500 ppm with respect to the total mass of the negative electrode.

[0068] Examples The alkaline dry battery of the present disclosure will be described in further detail with reference to examples.

[0069] Examples 1 to 3 and Comparative Examples 1 to 5 (1) Preparation of Electrolyte (Alkaline Electrolyte) An alkaline aqueous solution containing potassium hydroxide (concentration 33% by mass) and zinc oxide (concentration 2% by mass) was prepared as the alkaline electrolyte.

[0070] (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 (D50): 40 μm) was used. For the graphite, graphite powder (average particle size (D50): 8 μm) was used.

[0071] 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 100:2. The electrolyte solution used was the same as the alkaline electrolyte solution prepared in (1) above.

[0072] Next, the flake-like positive electrode mixture was crushed into granules, which were then classified using a 10 to 100 mesh sieve to obtain granules. The obtained granules were pressure-molded into a hollow cylindrical shape (height 10.8 mm) to obtain a positive electrode pellet (mass 2.9 g).

[0073] (3) Synthesis of surfactants Nonionic surfactants S1 to S5 were synthesized by etherification reaction of alkyl alcohol with polyethylene glycol. １ - (OC ２ H ４ ) ｎ In -X, R １ is an alkyl group having m carbon atoms (C ｍ H ２ｍ＋１ In surfactants S1 to S5, the degree of polymerization n of polyethylene glycol and / or the alkyl group R １ The carbon number m varies in the range of 2 to 20 for n and 9 to 24 for m.

[0074] In addition, a product synthesized by the etherification reaction of alkyl alcohol and polyethylene glycol was further reacted with phosphoric acid to synthesize a phosphoric acid type (phosphate ester type) anionic surfactant S6. １ - (OC ２ H ４ ) ｎ In the -X, X is a phosphate ester group (-OPO ３ H ２ ) and the alkyl group R １ The number of carbon atoms m is 12, and the degree of polymerization of polyethylene glycol n is 4.

[0075] In addition, a product synthesized by the etherification reaction of alkyl alcohol and polyethylene glycol was further reacted with sulfuric acid to synthesize a sulfonic acid type (sulfonate ester type) anionic surfactant S7. １ - (OC ２ H ４ ) ｎ In the -X, X is a sulfonate group (-OSO ３ H), wherein the alkyl group R １ The number of carbon atoms m is 18, and the degree of polymerization of polyethylene glycol n is 6.

[0076] Table 1 shows the structures of the prepared surfactants S1 to S7.

[0077]

[0078] (4) Preparation of Negative Electrode A gelled negative electrode was obtained by mixing zinc alloy powder, a gelling agent, an electrolyte, and optionally a surfactant and a sulfate. The gelling agent and the electrolyte were mixed in a mass ratio of gelling agent:electrolyte = 2.4:100. The electrolyte used was the same alkaline electrolyte as prepared in (1) above. The sulfate was zinc sulfate hydrate (ZnSO ４ ・7H ２ The surfactant used was the surfactant S1 described above. When the surfactant S1 was contained in the negative electrode, the surfactant S1 was contained in a content of 100 ppm by mass with respect to the entire negative electrode.

[0079] The content of zinc alloy powder and sulfate was 66% by mass based on the total negative electrode. The negative electrode active material 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 gelling agent was a mixture of cross-linked polyacrylic acid and partial sodium salt of cross-linked polyacrylic acid.

[0080] (5) Assembly of Alkaline Dry Battery Using the above components, an alkaline dry battery was assembled in the following manner: The procedure for assembling the battery will be described with reference to FIG.

[0081] 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 pressure was applied to form a positive electrode 2 in close contact with the inner wall of the battery case 1. A bottomed cylindrical separator 4 was then placed inside the positive electrode 2, and the alkaline electrolyte prepared in (1) above was injected to impregnate the separator 4. This state was left for a predetermined time, allowing the alkaline electrolyte to permeate through the separator 4 into the positive electrode 2. Then, 6.3 g of a gelled negative electrode 3 was filled inside the separator 4.

[0082] The separator 4 was formed using a cylindrical separator 4a and a bottom paper 4b. The cylindrical separator 4a and the bottom paper 4b were made of a nonwoven fabric sheet mainly composed of rayon fiber and polyvinyl alcohol fiber (mass ratio 1:1).

[0083] 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-6,10. 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.

[0084] 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 (not shown) were placed in the battery housing.

[0085] Next, the outer surface of the battery case 1 was covered with an exterior label 8. In this way, an alkaline dry battery was produced.

[0086] The content of sulfate added to the negative electrode was varied within a range of 0 to 1.0 mass % in terms of sulfate ions relative to the total mass of the negative electrode to produce alkaline batteries A1 to A3 according to Examples 1 to 3 and alkaline batteries B1 to B5 according to Comparative Examples 1 to 5. In alkaline batteries B1 and B2, no sulfate was added to the negative electrode. In alkaline batteries B1 and B3, no surfactant was added to the negative electrode.

[0087] (6) Evaluation [1. Leakage Resistance] The manufactured batteries were stored for 8 months in an environment at 60° C. After storage, the batteries were taken out and visually inspected for the presence or absence of leakage.

[0088] The number n1 of batteries in which leakage was confirmed was determined for 50 alkaline batteries (N=50). The proportion n1 / N of batteries in which leakage was confirmed was evaluated as the leakage rate.

[0089] [2. Medium-Load Intermittent Discharge Test] The manufactured battery was connected to a 3.9 Ω resistor via a switch, and intermittent discharge was performed with the switch turned on at a duty ratio of 1 hour per day. Specifically, the battery was discharged for 1 hour followed by a 23-hour rest cycle in an environment of 20±1°C. The above discharge cycle was repeated until the battery voltage reached 0.8 V.

[0090] For 50 alkaline batteries (N=50), the total discharge time from the start of discharge until the battery voltage reached 0.8 V or less (i.e., the total period during which the switch was on) 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, and the number n2 of batteries whose duration was less than 8 hours was calculated. The proportion n2 / N of batteries whose duration was less than 8 hours was evaluated as the incidence of internal short circuits.

[0091] Table 2 shows the evaluation results of leakage resistance and medium load intermittent discharge tests for batteries A1 to A3 and B1 to B5. Table 2 also shows the surfactants used in each battery, their content in the entire negative electrode, and the sulfate (ZnSO ４ The content of sulfate in the entire negative electrode is shown together with the evaluation results. The sulfate content represents the percentage of the mass of sulfate ions in the sulfate relative to the mass of the entire negative electrode.

[0092] As shown in Table 2, Battery B1, which did not contain either a surfactant or a sulfate in the negative electrode, had a high leakage rate. In contrast, Battery B2, which contained a surfactant in the negative electrode, had significantly improved leakage resistance compared to Battery B1 and did not leak, but the incidence of internal short circuits increased and discharge performance during medium-load intermittent discharge deteriorated.

[0093] Battery B3, which contained sulfate in the negative electrode, was able to suppress internal short circuits during medium-load intermittent discharge compared to Battery B1, and no internal short circuits occurred. However, it was prone to leakage, and the leakage rate was higher than that of Battery B1, which did not contain sulfate.

[0094] In contrast, in the batteries A1 to A3 in which sulfate was added to the negative electrode in an amount of 0.01 to 0.5 mass % in terms of sulfate ions relative to the mass of the entire negative electrode, no internal short circuit occurred, and no leakage occurred, even when a surfactant was added.

[0095] In Battery B4, the addition of sulfate to the negative electrode reduced the incidence of internal short circuits compared to Battery B2, but the sulfate content was low at 0.005 mass% in terms of sulfate ions, and internal short circuits could not be sufficiently suppressed. On the other hand, in Battery B5, the sulfate content was excessive at 1.0 mass% in terms of sulfate ions, and the incidence of internal short circuits increased compared to Battery A3. This is thought to be because the increased sulfate content led to greater unevenness in the distribution of sulfate within the negative electrode, which in turn led to greater unevenness in the pH of the electrolyte within the negative electrode, thereby promoting internal short circuits.

[0096]

[0097] Examples 4 to 11 In the preparation of the negative electrode, the sulfate added to the negative electrode was the same as that of Example 2, except that the ZnSO ４ ・7H ２O was changed to the compound shown in Table 3. Alkaline batteries A4 to A11 according to Examples 4 to 11 were fabricated and evaluated in the same manner as in Example 2, except for this. Table 3 shows the evaluation results of batteries A4 to A11 together with the evaluation result of battery A2. Table 3 also shows the type of sulfate contained in the negative electrode of each battery along with the evaluation results. The content of sulfate in each battery was 0.1% by mass, calculated as sulfate ions, relative to the mass of the entire negative electrode, and this was the same for batteries A2, A4 to A11.

[0098]

[0099] As shown in Table 3, in the batteries A4 to A11, leakage and internal short circuits were suppressed regardless of the type of sulfate added to the negative electrode.

[0100] Examples 12 to 19 In the preparation of the negative electrode, the surfactant and / or its content was changed from Example 2 to Example 13 as shown in Table 4. Alkaline batteries A12 to A19 according to Examples 13 to 20 were prepared and evaluated in the same manner as in Example 2. Table 4 shows the evaluation results of batteries A12 to A19 together with the evaluation results of batteries A2 and B3. Table 4 also shows the type of sulfate contained in the negative electrode of each battery along with the evaluation results.

[0101]

[0102] As shown in Table 4, in the batteries A12 to A19, leakage and internal short circuits were suppressed regardless of the type of surfactant. １ In battery A17 using surfactant S3 with a small carbon number m, and battery A18 using surfactant S4 with a small degree of polymerization n, a slight decrease in leakage resistance was observed. On the other hand, if the carbon number m or degree of polymerization n is large, the resistance inside the battery increases, which may lead to a decrease in discharge characteristics. From the above points, R １ The carbon number m may be 9 to 24, and more preferably 12 to 24. The degree of polymerization n may be 2 to 20, and more preferably 3 to 20.

[0103] The present disclosure can be used in alkaline batteries.

[0104] REFERENCE SIGNS LIST 1 Battery case 2 Positive electrode 3 Negative electrode 4 Separator 4a Cylindrical separator 4b Bottom paper 5 Gasket 5a Thin portion 6 Negative electrode current collector 7 Negative electrode terminal plate 8 Outer packaging label 9 Sealing unit 10 Alkaline dry battery

Claims

1. An alkaline dry battery comprising a hollow cylindrical positive electrode disposed in a battery case, a gel-like negative electrode filled in the hollow portion of the positive electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the negative electrode contains zinc powder and a surfactant, and the negative electrode further contains a sulfate in a range of 0.01 to 0.5% by mass in terms of sulfate ion with respect to the mass of the negative electrode.

2. The alkaline dry battery according to claim 1, wherein the sulfate contains at least one selected from the group consisting of potassium sulfate, sodium sulfate, aluminum sulfate, potassium aluminum sulfate, calcium sulfate, zinc sulfate, lithium sulfate, and hydrates thereof.

3. The surfactant has a polyoxyethylene group represented by -(OC ２ H ４ ). ｎ The alkaline dry battery according to claim 1 or 2.

4. The alkaline dry battery according to claim 3, wherein the surfactant is a nonionic surfactant having a hydroxy group (-OH).

5. The alkaline dry battery according to claim 3, wherein the surfactant is a phosphoric acid type anionic surfactant having a phosphate ester group.

6. The alkaline dry battery according to claim 3, wherein the surfactant is a sulfonic acid type anionic surfactant having a sulfonate ester group.

7. The surfactant has the general formula: R １ -(OC ２ H ４ ) ｎ -X, where R １ is a hydrocarbon group having 9 to 24 carbon atoms, and X contains a hydroxy group (-OH), a phosphate ester group (-OPO ３ H ２ ), or a sulfonic acid ester group (-OSO ３ H), and the degree of polymerization n of the polyoxyethylene group (OC ２ H ４ ) ｎ is in the range of 2 to 20. The alkaline dry battery according to claim 3.

8. The alkaline dry battery according to claim 1 or 2, wherein the content of the surfactant contained in the negative electrode is in the range of 10 ppm to 500 ppm with respect to the total mass of the negative electrode.

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