alkaline batteries

Abstract

This alkaline dry cell comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a liquid electrolyte included in the positive electrode, the negative electrode, and the separator. The positive electrode includes manganese dioxide. The half width W of the 110-plane diffraction peak is at most 2.4° in the X-ray diffraction pattern of the manganese dioxide. The negative electrode includes a powder of a negative electrode active material including zinc. Of all of the particles in the powder, the proportion taken up by particles that have a particle size of at most 75 µm is at least 33 mass%. The thickness of the separator is 150-210 µm, inclusive.

Description

[Technical Field]

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

[0002] Alkaline batteries (alkaline manganese batteries) are widely used because they have a larger capacity and can extract a larger current than manganese batteries. Improvements to the battery components are being considered to improve the performance of alkaline batteries.

[0003] Patent Document 1 proposes an alkaline dry battery comprising a negative electrode containing zinc powder, an electrolyte, a separator, and a positive electrode, wherein the zinc powder contains 60 to 80 wt % of first zinc particles having a particle size of more than 75 μm and not more than 425 μm and 40 to 20 wt % of second zinc particles having a particle size of not more than 75 μm.

[0004] In Patent Document 2, a crosslinked highly water-absorbent polymer compound having a carboxyl group is added to a wet-laid nonwoven fabric containing alkali-resistant fibers at a rate of 5.0 to 45.0 g / m 2 The separator for alkaline batteries is formed by laminating a wet-laid nonwoven fabric containing alkali-resistant fibers to a substrate on which the crosslinked highly water-absorbent polymer compound is adhered and crosslinked, and the silicate compound is contained in the crosslinked highly water-absorbent polymer compound in an amount of 1.0 × 10 per unit area of ​​the separator. -4 ~10mg / cm 2 There has been proposed a separator for an alkaline battery in which the separator is added so as to contain the metal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-151539 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-227067 Summary of the Invention

[0006] If the separator thickness is reduced to improve the performance of alkaline batteries, an internal short circuit may occur when the battery is stopped during discharge.

[0007] An alkaline dry battery according to one aspect of the present disclosure includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution contained in the positive electrode, the negative electrode, and the separator, wherein the positive electrode contains manganese dioxide, and the manganese dioxide has an X-ray diffraction pattern in which the half width W of a diffraction peak of a 110-plane is 2.4° or less; the negative electrode contains a powder of a negative electrode active material containing zinc, and a proportion of particles having a particle size of 75 μm or less to all particles in the powder is 33 mass% or more; and the separator has a thickness of 150 μm or more and 210 μm or less.

[0008] According to the present disclosure, it is possible to suppress the occurrence of an internal short circuit when an alkaline battery is paused during discharge. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a partially cross-sectional front view of an alkaline dry battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] An alkaline dry battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution contained in the positive electrode, the negative electrode, and the separator. The positive electrode contains manganese dioxide as a positive electrode active material, and the negative electrode contains a negative electrode active material containing zinc. In this specification, the electrolyte solutions contained in the positive electrode, the negative electrode, and the separator are also referred to as the "positive electrode electrolyte," the "negative electrode electrolyte," and the "separator electrolyte," respectively.

[0011] By reducing the thickness of the separator, it is possible to increase the amount of active material packed in the battery and reduce the internal resistance, but on the other hand, an internal short circuit may occur during a pause in discharging, shortening the discharge time. The present inventors investigated the above-mentioned internal short circuit and obtained the following findings.

[0012] As the battery discharge progresses (the amount of discharged electricity increases), the positive electrode expands and becomes more porous. The expansion of the positive electrode also compresses the separator, causing some of the electrolyte in the separator to move to the positive electrode, reducing the amount of electrolyte in the separator. Furthermore, once discharge has progressed to a certain extent, the pH of the electrolyte in the separator decreases. If the separator is thin, the amount of electrolyte in the separator is likely to decrease during discharge, and the pH is likely to decrease.

[0013] The decrease in pH of the electrolyte in the separator is presumably due to a unique effect of manganese dioxide that occurs as the amount of electrolyte in the separator decreases. Below, we will discuss this unique effect of manganese dioxide, which is opposite to what is generally expected.

[0014] When the solution it comes into contact with is basic, manganese dioxide in the positive electrode neutralizes the solution by releasing more protons as the pH of the solution approaches neutrality. In contrast, when the solution is strongly basic with a low proton concentration, the amount of protons released by manganese dioxide decreases. Therefore, when the separator in contact with the positive electrode contains a large amount of strongly basic electrolyte, the pH of the electrolyte in the separator hardly decreases. On the other hand, as the battery discharge progresses and the amount of electrolyte in the separator decreases, the proton concentration of the electrolyte in the separator tends to increase even if the amount of protons released by manganese dioxide is small. As a result, the amount of electrolyte in the separator decreases, and the amount of protons released by manganese dioxide increases exponentially, making the pH of the electrolyte in the separator more likely to decrease. Surprisingly, the pH can sometimes drop to around 9.

[0015] During discharge, zinc ions are generated at the negative electrode, increasing the zinc ion concentration in the electrolyte in the negative electrode. During a pause in discharge, the expansion of the positive electrode stops, causing a portion of the electrolyte in the negative electrode, containing a high concentration of zinc ions, to slowly and gradually migrate to the separator, which contains an electrolyte with a lowered pH, resulting in the diffusion of many zinc ions into the electrolyte in the separator. Meanwhile, the solubility of zinc ions in aqueous solution is significantly lower when the pH is in the neutral range, e.g., 9 to 10, than when the aqueous solution has a high pH. Therefore, during a pause in discharge, countless conductive zinc oxide microcrystals precipitate in the gaps between the fibers that make up the separator, acting as a P-type semiconductor and causing an internal short circuit. When the separator is thin, the electrolyte in the separator is likely to decrease, causing the pH to drop to near neutral, leading to the precipitation of these microcrystals within the separator. Furthermore, the short distance between the positive and negative electrodes also makes an internal short circuit more likely. The electrolyte before discharge is usually strongly alkaline with a pH of about 15, and about 5 mass % of zinc, calculated as zinc oxide, can dissolve in the electrolyte.

[0016] The smaller the half-width of the diffraction peak of the 110 plane in the X-ray diffraction pattern of manganese dioxide, the lower the expansion rate of the positive electrode (manganese dioxide), which tends to suppress the migration of the electrolyte in the separator to the positive electrode during discharge.

[0017] The greater the proportion of fine particles (particles with a particle size of 75 μm or less) in the negative electrode active material particles contained in the negative electrode, the greater the surface area of ​​the negative electrode active material contained in the negative electrode, which tends to increase the negative electrode's ability to retain electrolyte, thereby suppressing the migration of electrolyte in the negative electrode to the separator when the battery is at rest.

[0018] Although the amount and molecular weight of the gelling agent also affect the electrolyte retention capacity of the negative electrode, it is believed that the surface tension of the negative electrode active material has a greater effect on the migration of electrolyte in the negative electrode to the separator during pauses in discharge than the amount of gelling agent added, etc. The amount of gelling agent added, etc., can affect the migration of electrolyte between the negative electrode and the separator and positive electrode during the storage period from immediately after battery manufacture until the start of use.

[0019] Based on the above findings, the present inventors have conducted extensive research focusing on the half-value width W and the proportion of fine particles, and have found that when the thickness of the separator is reduced to 210 μm or less, internal short circuits during pauses in discharge can be suppressed by setting the half-value width W and the proportion of fine particles within specific ranges.

[0020] That is, an alkaline dry battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte (alkaline electrolyte) contained in the positive electrode, negative electrode, and separator. The positive electrode contains manganese dioxide, and the half-width W of the diffraction peak of the 110 plane in the X-ray diffraction pattern of the manganese dioxide is 2.4° or less. The negative electrode contains a powder of a negative electrode active material containing zinc, and the proportion of particles with a particle size of 75 μm or less (hereinafter also referred to as "fine particles") to all particles in the powder is 33 mass% or more. The thickness T of the separator is 150 μm or more and 210 μm or less.

[0021] When the half-width W is 2.4° or less and the proportion of fine particles is 33% by mass or more, reducing the separator thickness T to 210 μm or less enables high capacity and reduced internal resistance, and also suppresses internal short circuits during pauses in discharge. However, when the separator thickness T is less than 150 μm, the distance between the positive and negative electrodes becomes small and the mechanical strength of the separator decreases, which can damage the separator if the battery is dropped, etc., and can cause internal short circuits.

[0022] (positive electrode) The positive electrode contains manganese dioxide as a positive electrode active material. Electrolytic manganese dioxide is usually used as the positive electrode active material, and examples of the crystal structure of electrolytic manganese dioxide include the γ type.

[0023] The half-width W of the diffraction peak of the 110 plane in the X-ray diffraction pattern of manganese dioxide is 2.4° or less, preferably 1.8° to 2.4°, and more preferably 1.9° to 2.3°. When the half-width W is 1.8° or more, a decrease in the diffusion rate of hydrogen ions within the manganese dioxide crystals and a resulting decrease in heavy-load discharge performance are suppressed.

[0024] When the half-width W is small, the crystallite size is large, and the expansion rate of the crystal particles due to H atoms entering the crystal lattice where Mn atoms and O atoms are arranged at specific sites during discharge is small, thereby suppressing the expansion of the positive electrode during discharge.

[0025] The "110 plane diffraction peak" is seen at a diffraction angle 2θ of approximately 22±1°, and is a diffraction peak that is attributed to the 110 plane when manganese dioxide is assumed to have a ramsdellite structure. The "half width W" is the full width at half maximum (FWHM).

[0026] The half-value width W is determined by the following method.

[0027] An unused (undischarged) battery was disassembled, and the positive electrode was collected, washed with water, dried, and then pulverized to obtain a powder sample. The obtained powder sample was subjected to powder X-ray diffraction measurement using CuKα radiation. The half-width W of the diffraction peak of the 110 plane was calculated using the X-ray diffraction pattern obtained by the above measurement (vertical axis: X-ray diffraction intensity, horizontal axis: diffraction angle 2θ).

[0028] (Negative electrode) The negative electrode contains zinc or a zinc alloy as a negative electrode active material. From the viewpoint of corrosion resistance, the zinc alloy preferably contains at least one selected from the group consisting of indium, bismuth, and aluminum. The zinc alloy preferably contains 100 ppm or more and 280 ppm or less of indium, 60 ppm or more and 200 ppm or less of bismuth, and 10 ppm or more and 80 ppm or less of aluminum.

[0029] The negative electrode active material is usually used in powder form. From the viewpoint of the packing property of the negative electrode and the diffusibility of the alkaline electrolyte in the negative electrode, the average particle size of all particles of the negative electrode active material powder is, for example, 80 μm or more and 200 μm or less, and preferably 100 μm or more and 150 μm or less.

[0030] In this specification, the average particle size refers to the median diameter (D50) in the volume-based particle size distribution. The average particle size is determined, for example, using a laser diffraction and / or scattering particle size distribution analyzer.

[0031] The proportion of fine particles in the total particles in the powder of the negative electrode active material contained in the negative electrode is 33% by mass or more, preferably 33% by mass or more and 55% by mass or less, and more preferably 36% by mass or more and 46% by mass or less. When the proportion of fine particles is 55% by mass or less, the reactivity is appropriately high, the increase in battery temperature during an external short circuit is suppressed, and safety is easily ensured.

[0032] The fine particles have a particle size of 75 μm or less and are capable of passing through a sieve with an opening of 75 μm (200 mesh). The greater the proportion of fine particles in the powder of the negative electrode active material, the greater the contact area between the negative electrode active material and the electrolyte, making it easier for the discharge reaction to proceed and improving the electrolyte retention capacity of the negative electrode.

[0033] The proportion of fine particles to all particles in the powder of the negative electrode active material contained in the negative electrode can be determined as follows.

[0034] Disassemble an unused (undischarged) battery, remove the negative electrode, remove the negative electrode active material powder from the negative electrode, and measure its mass W0. Then, use a sieve to separate fine particles (particles with a particle size of 75 μm or less) from the negative electrode active material powder, and measure their mass W1. Calculate W1 / W0 × 100 as the proportion of the fine particles.

[0035] The negative electrode active material powder is extracted from the negative electrode as follows. First, a sufficient amount of distilled water is added to the negative electrode and stirred to wash the negative electrode active material. Specifically, the negative electrode active material is precipitated in distilled water, and the supernatant liquid containing components other than the negative electrode active material (gelling agent, electrolyte, etc.) is removed. This process is repeated several times. Next, the negative electrode active material is washed with absolute ethanol to remove any traces of moisture adhering to the negative electrode active material, and then dried at 100°C for a short period of time. This prevents oxidation of the surface of the negative electrode active material.

[0036] (separator) A nonwoven fabric is preferably used as the separator. For example, a nonwoven fabric sheet containing cellulose fibers and polyvinyl alcohol fibers is used as the separator. The nonwoven fabric sheet is obtained, for example, by blending cellulose fibers and polyvinyl alcohol fibers as the main components. Examples of cellulose fibers include rayon fibers (regenerated fibers). The content of polyvinyl alcohol fibers in the nonwoven fabric is, for example, 25 parts by mass or more and 150 parts by mass or less per 100 parts by mass of cellulose fibers.

[0037] The thickness T of the separator is 150 μm or more and 210 μm or less, and preferably 170 μm or more and 200 μm or less. Note that the thickness T of the separator here means the thickness of the separator in a state where it has absorbed the electrolyte inside the battery, and corresponds to the distance between the positive electrode and the negative electrode inside the battery.

[0038] A cylindrical separator is usually used as the separator disposed between the positive electrode and the negative electrode. The cylindrical separator may be formed by winding a single substrate sheet having a thickness of t (μm) X times into a cylindrical shape. Alternatively, the cylindrical separator may be formed by winding a laminated sheet having X layers of substrate sheets each having a thickness of t (μm) into a cylindrical shape in a single layer. When the thickness t is the thickness of the substrate sheet in a state where the electrolyte solution has been absorbed in the battery, t × X is the thickness T. When the separator has a portion P1 where one end of the substrate sheet where the winding starts and the other end of the substrate sheet where the winding ends overlap each other, the thickness T of the separator refers to the thickness of the portion other than the portion P1.

[0039] The thickness T of the separator is determined as follows.

[0040] For an unused (before discharge) battery, an X-ray CT image of the cross section of the power generating elements (positive electrode, negative electrode, and separator, including the electrolyte) contained in the battery is obtained by computed tomography (CT). Using the cross-sectional image, the distances between the positive electrode and negative electrode sandwiching the separator contained in the battery (excluding portion P1, if any) are measured at 10 arbitrary points, and the average value of these distances is calculated to be the thickness T.

[0041] The density of the separator is 0.22 g / cm 3 More than 0.29g / cm 3 or less. In this case, sufficient mechanical strength is ensured, damage to the separator during the battery manufacturing process or when the battery is dropped, etc. is suppressed, and even a small thickness can sufficiently separate the positive electrode and the negative electrode. The density of the separator is calculated by dividing the mass of the separator by the volume of the separator. The mass of the separator above refers to the mass of the separator in a dry state that does not contain electrolyte. The mass of the separator is calculated by removing the separator from the battery, washing it with water to remove the electrolyte, drying it, and then measuring its mass. The volume of the separator is calculated based on the area of ​​the separator and the thickness T described above. The area of ​​the separator is calculated by removing the separator from the battery and measuring the longitudinal and lateral dimensions of the separator.

[0042] The electrolyte may be, for example, an aqueous potassium hydroxide solution. The content of potassium hydroxide in the electrolyte is, for example, 30% by mass or more and 50% by mass or less. The electrolyte may further contain zinc oxide. The content of zinc oxide in the electrolyte is, for example, 1% by mass or more and 5% by mass or less. The contents (mass%) of potassium hydroxide and zinc oxide in the electrolyte respectively refer to the ratio (percentage) of the mass of potassium hydroxide and zinc oxide contained in the electrolyte relative to the mass of the entire electrolyte.

[0043] The alkaline dry battery according to this embodiment will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the following embodiment. Furthermore, appropriate modifications are possible within the scope of the effects of the present disclosure. Furthermore, the present disclosure can be combined with other embodiments.

[0044] FIG. 1 is a front view of a horizontal half cross section of an alkaline dry battery 10 according to an embodiment of the present disclosure.

[0045] As shown in FIG. 1, an alkaline dry battery 10 includes a power generating element including a hollow cylindrical positive electrode 2, a gelled negative electrode 3 disposed within the hollow portion of the positive electrode 2, a separator 4 disposed therebetween, and an alkaline electrolyte 11. The power generating element is housed within a cylindrical metal case 1 with a bottom that also serves as the positive electrode terminal. The case 1 may be made of, for example, a nickel-plated steel plate. The positive electrode 2 is disposed in contact with the inner wall of the case 1. To improve adhesion between the positive electrode 2 and the case 1, the inner surface of the case 1 is preferably coated with a carbon film.

[0046] The cylindrical separator 4 with a bottom is composed of a cylindrical separator 4a and a bottom 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 cylindrical separator 4a is arranged between the positive electrode and the negative electrode, and has a thickness of 150 μm or more and 210 μm or less. The bottom 4b is arranged at the bottom of the hollow portion of the positive electrode 2, separating the negative electrode 3 from the case 1.

[0047] The electrolyte 11 permeates at least the positive electrode 2, the negative electrode 3, and the separator 4, and therefore includes at least the positive electrode electrolyte 11p, the negative electrode electrolyte 11n, and the separator electrolyte 11s contained in the positive electrode 2, the negative electrode 3, and the separator 4, respectively.

[0048] The opening of the case 1 is sealed with a sealing unit 9. The sealing unit 9 includes a resin gasket 5, a negative electrode terminal plate 7 that also serves as a negative electrode terminal, and a negative electrode current collector 6. The gasket 5 has a locally thin annular thin-walled portion 5a. When the internal pressure of the battery exceeds a predetermined value, the thin-walled portion 5a breaks, releasing gas to the outside of the battery. The negative electrode current collector 6 is inserted into the negative electrode 3. The negative electrode current collector 6 is 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, if necessary. The negative electrode current collector 6 has a nail-like shape with a head and a body. The body is inserted into a through-hole provided in a central cylindrical portion of the gasket 5, and 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 open end of the case 1 is crimped onto the flange on the periphery of the negative electrode terminal plate 7 via the outer peripheral end of the gasket 5. The outer surface of the case 1 is covered with an exterior label 8.

[0049] The positive electrode 2 contains manganese dioxide as a positive electrode active material and an electrolyte solution. The manganese dioxide contained in the positive electrode 2 has an X-ray diffraction pattern in which the half width W of the diffraction peak of the 110 plane is 2.4° or less.

[0050] In the preparation of the positive electrode, manganese dioxide is used in the form of powder. The average particle size of manganese dioxide is, for example, 25 μm or more and 55 μm or less, preferably 32 μm or more and 50 μm or less. In this case, good battery performance is easily obtained. The particle size of manganese dioxide can be adjusted by pulverization, classification, etc.

[0051] The positive electrode active material may contain, in addition to manganese dioxide, other manganese oxides, oxides of Ni, etc. In this case, the proportion of manganese dioxide in the positive electrode active material may be, for example, 50% by mass or more, or 75% by mass or more.

[0052] The positive electrode 2 may contain a conductive agent in addition to manganese dioxide and an electrolyte. Examples of the conductive agent include carbon black such as acetylene black, and conductive carbon materials such as graphite. Examples of graphite that can be used include natural graphite and artificial graphite. The conductive agent may be in a fibrous form, but is preferably in a powder form. The average particle size of the conductive agent can be selected, for example, from a range of 5 nm to 50 μm. When the conductive agent is carbon black, the average particle size of the conductive agent is preferably 5 nm to 40 nm, and when the conductive agent is graphite, the average particle size is preferably 3 μm to 50 μm.

[0053] The graphite content in the positive electrode may be 3 parts by mass or more and 8 parts by mass or less, and preferably 4 parts by mass or more and 7 parts by mass or less, per 100 parts by mass of the total of manganese dioxide and graphite. When the graphite content is 7% by mass or less, a sufficient amount of manganese dioxide is likely to be filled, and good battery performance is likely to be obtained.

[0054] The positive electrode 2 can be obtained, for example, by pressure-molding a positive electrode mixture containing a positive electrode active material, a conductive agent, and an electrolyte solution into pellets. The positive electrode mixture may be first formed into flakes or granules, classified as necessary, and then pressure-molded into pellets. After the pellets are placed in a case, they may be subjected to secondary pressure using a predetermined tool so as to adhere to the inner wall of the case. The positive electrode (positive electrode mixture) may further contain other components (for example, polytetrafluoroethylene) as necessary.

[0055] The density of manganese dioxide in the positive electrode is, for example, 2.70 g / cm 3 More than 3.10g / cm 3 is preferably 2.80 g / cm or less. 3 More than 3.05g / cm 3The density of manganese dioxide in the positive electrode can be calculated by dividing the mass of manganese dioxide contained in the positive electrode by the volume of the positive electrode. The mass of manganese dioxide contained in the positive electrode can be calculated by removing the positive electrode from the battery, thoroughly dissolving it in acid, removing the insoluble matter, recovering the solution, determining the Mn content in the solution using inductively coupled plasma atomic emission spectroscopy (ICP atomic emission spectroscopy), and converting it to MnO2. The volume of the positive electrode can be calculated based on the outer diameter, inner diameter, and height of the positive electrode measured in an X-ray CT image of the battery.

[0056] The density of the positive electrode is, for example, 2.85 g / cm 3 More than 3.30g / cm 3 Preferably, it is 2.90 g / cm or less. 3 More than 3.20g / cm 3 The density of the positive electrode can be calculated by dividing the mass of the positive electrode by the volume of the positive electrode. The mass of the positive electrode is the mass of the positive electrode including the positive electrode electrolyte 11p, and can be calculated by removing the positive electrode from the battery and measuring its mass. The volume of the positive electrode can be calculated by the method described above.

[0057] The negative electrode 3 is in a gel state and contains a powder of a negative electrode active material, an electrolyte, and a gelling agent. The proportion of fine particles (particles with a particle size of 75 μm or less) to all particles in the powder of the negative electrode active material contained in the negative electrode 3 is 33 mass % or more.

[0058] The gelling agent may be any known gelling agent used in the field of alkaline batteries, without particular limitation, such as a water-absorbent polymer. Examples of such gelling agents include polyacrylic acid and sodium polyacrylate. The amount of gelling agent added may be 0.5 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the negative electrode active material.

[0059] The separator is preferably made of the nonwoven fabric exemplified above, but may also be made of a microporous film such as cellophane. The bottom 4b may be made of the cylindrical separator 4a exemplified above.

[0060] 1, the bottomed cylindrical separator 4 is composed of a cylindrical separator 4a and a bottom 4b, but is not limited to this. A bottomed cylindrical one-piece separator may also be used, and separators of known shapes used in the field of alkaline batteries can be used.

[0061] [Example] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0062] Examples 1 to 35 and Comparative Examples 1 to 26 An AA cylindrical alkaline battery 10 (LR6) shown in FIG. 1 was fabricated according to the following procedure.

[0063] (Preparation of positive electrode) A mixture of 94.3 parts by weight of positive electrode active material and 5.7 parts by weight of graphite powder (average particle size 8 μm), totaling 100 parts by weight, was prepared by adding 0.2 parts by weight of polytetrafluoroethylene. 2 parts by weight of electrolyte was added to 100.2 parts by weight of the mixture, thoroughly stirred, and then compression-molded into flakes to obtain a positive electrode mixture. The electrolyte used was a KOH aqueous solution (40% by weight) containing 2% by weight of ZnO.

[0064] The flake-like positive electrode mixture was crushed into granules, which were then classified using a 10 to 100 mesh sieve. A predetermined amount of the granules was then pressure-molded into a predetermined hollow cylindrical pellet having an outer diameter of 13.65 mm and a height of 21.7 mm, and two of these positive electrode pellets were placed in a battery case.

[0065] The positive electrode active material was a γ-type manganese dioxide powder (average particle size 40 μm) synthesized by electrolysis. By appropriately adjusting the current value during electrolysis, the half-width W of the diffraction peak of the 110 plane in the powder X-ray diffraction pattern of manganese dioxide using CuKα radiation was set to the values ​​shown in Tables 1 to 3.

[0066] (Preparation of negative electrode) A gelled negative electrode was obtained by mixing 100 parts by weight of negative electrode active material, 49 parts by weight of electrolyte, and 1 part by weight of gelling agent. The negative electrode active material was zinc alloy powder containing 0.02% by weight of indium, 0.01% by weight of bismuth, and 0.0045% by weight of aluminum. The gelling agent was a mixture of cross-linked branched polyacrylic acid and highly cross-linked chain sodium polyacrylate. The electrolyte was a KOH aqueous solution (concentration: 33% by weight) containing 2% by weight of ZnO.

[0067] The zinc alloy powder was sieved to obtain a coarse powder having a particle size of more than 75 μm and 500 μm or less, and a fine powder having a particle size of 75 μm or less, and then the mixing ratio of the coarse powder and the fine powder was appropriately adjusted to obtain the fine powder content in the zinc alloy powder as shown in Tables 1 to 3. The average particle size of the zinc alloy powder was in the range of 100 μm or more and 150 μm or less.

[0068] (Alkaline battery assembly) Two positive electrode pellets were inserted vertically into the case 1, and then pressure was applied to form a positive electrode 2 in close contact with the inner wall of the case 1. The case 1 was a cylindrical case (outer diameter 14.0 mm, height 49.9 mm) with a bottom and made of nickel-plated steel sheet, the inner surface of which was covered with a carbon film.

[0069] A cylindrical separator 4 with a bottom was placed inside the positive electrode 2, and a predetermined amount of electrolyte was poured into the case 1 and absorbed into the separator 4. The separator 4 was composed of a cylindrical separator 4a and a bottom 4b. The cylindrical separator 4a and bottom 4b were made of a nonwoven fabric sheet primarily composed of a 1:1 mass ratio of rayon fiber and polyvinyl alcohol fiber. The cylindrical separator 4a was formed by wrapping the nonwoven fabric sheet twice. The thickness of the bottom 4b was 140 μm. The electrolyte used to impregnate the separator (to inject into the case) was the same as the electrolyte used to prepare the negative electrode. This was left for a predetermined time, allowing the electrolyte to permeate through the separator 4 into the positive electrode 2. A predetermined amount of gelled negative electrode 3 was then filled inside the separator 4.

[0070] The thickness T of the cylindrical separator 4a was set to the values ​​shown in Tables 1 to 3 by changing the thickness of the nonwoven fabric sheet. The amount of the positive electrode 2 and the negative electrode 3 packed in the battery was adjusted appropriately according to the thickness T of the cylindrical separator 4a. The amount of the positive electrode 2 packed was adjusted by changing the inner diameter of the positive electrode pellet. The mass ratio of the positive electrode and the negative electrode packed in the battery was kept constant. The smaller the thickness T, the greater the amount of the positive and negative electrodes packed.

[0071] A sealing unit 9 consisting of a gasket 5, a negative electrode terminal plate 7, and a negative electrode current collector 6 was placed in the opening of the case 1. At this time, the body of the negative electrode current collector 6 was inserted into the negative electrode 3. The open end of the case 1 was crimped to the peripheral edge of the negative electrode terminal plate 7 via the gasket 5, sealing the opening of the case 1. The outer surface of the case 1 was covered with an exterior label 8. In this way, an alkaline dry battery 10 was produced. In the table, A1 to A35 are the batteries of Examples 1 to 35, and B1 to B26 are the batteries of Comparative Examples 1 to 26.

[0072] The density of manganese dioxide in the positive electrode 2 is 2.93 to 2.96 g / cm 3 The density of the positive electrode 2 was 3.10 g / cm 3 The density of the cylindrical separator 4a was 2.7 g / m 3 It was.

[0073] The following evaluations were carried out for each of the batteries of the Examples and Comparative Examples.

[0074] [Evaluation 1: Internal short circuit occurrence rate during discharge] Intermittent discharge was performed in an environment of 20±1°C, with a constant current discharge of 250 mA for 1 hour, followed by a 23-hour rest period. The discharge time until the closed-circuit voltage of the battery reached 0.9 V was measured. Note that the discharge time is the total discharge time at 250 mA, excluding rest periods. If the discharge time was less than 8.5 hours, it was determined that an internal short circuit had occurred during discharge. Intermittent discharge was performed on each of the six batteries, and the number of batteries that had experienced an internal short circuit during discharge was counted. The evaluation results are shown in Tables 1 to 3.

[0075] [Table 1]

[0076] [Table 2]

[0077] [Table 3]

[0078] In batteries A1 to A35, which had separator thicknesses of 210 μm or less, half-widths W of 2.4° or less, and fine particles accounting for 33 mass% or more of the total particles in the zinc alloy powder, no internal short circuits were observed. In batteries A1 to A35, the separator thickness was small, at 210 μm or less, and the loading amounts of positive and negative electrodes could be increased.

[0079] In batteries B1 to B16 and B18 to B26, in which the separator thickness was 210 μm or less, the half-width W exceeded 2.4° and / or the proportion of fine particles to the total particles in the zinc alloy powder was less than 33 mass%, and some batteries experienced internal short circuits.

[0080] In battery B17, no internal short circuit occurred, but the thickness of the separator was greater than 210 μm, so the filling amounts of the positive and negative electrodes were reduced. [Industrial Applicability]

[0081] The alkaline dry battery according to the present disclosure is suitable for use as a power source for, for example, portable audio devices, electronic games, lights, and the like. [Explanation of symbols]

[0082] 1 case 2 Positive electrode 3 negative electrode 4 Separator 4a Cylindrical separator 4b bottom 5 Gasket 5a Thin wall part 6 Negative electrode current collector 7 Negative terminal plate 8. Exterior Label 9 Sealing unit

Claims

1. a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution contained in the positive electrode, the negative electrode, and the separator; the positive electrode comprises manganese dioxide; the half-value width W of the diffraction peak of the 110 plane in the X-ray diffraction pattern of the manganese dioxide is 2.4° or less; the negative electrode contains a powder of a negative electrode active material containing zinc, a ratio of particles having a particle size of 75 μm or less to all particles in the powder is 33 mass% or more; The thickness of the separator is 150 μm or more and 210 μm or less.

2. 2. The alkaline battery according to claim 1, wherein the half-value width W is 1.8° or more and 2.4° or less.

3. 3. The alkaline dry battery according to claim 1, wherein the proportion of the particles having a particle size of 75 μm or less is 33% by mass or more and 55% by mass or less.

4. 3. The alkaline dry battery according to claim 1, wherein the separator has a thickness of 170 μm or more and 200 μm or less.

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