Alkaline battery

Abstract

To restrain liquid spill of alkaline battery for a long period of time.SOLUTION: An alkaline battery includes a bottomed cylindrical case having an opening end portion, a power generating element accommodated in the case, and a sealing unit for sealing the opening end portion. The power generating element includes a hollow cylindrical positive electrode, a negative electrode filled in the hollow of the positive electrode, and a separator interposed between the positive electrode and the negative electrode. The opening end portion has an annular groove that is recessed inward and supports the sealing unit, and the end face of the negative electrode on the opening end portion side is covered with a gel-like shielding layer. The gel-like shielding layer contains an alkaline electrolyte and cross-linked polyacrylic acid. The content of the cross-linked polyacrylic acid in the gel-like shielding layer is 2.0% by mass or more and 3.0% by mass or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an alkaline dry battery.

Background Art

[0002] Patent Document 1 proposes an "alkaline battery including: (a) a housing; (b) a cathode within the housing, defining an anode cavity and having an upper surface adjacent to the cavity; (c) an anode deposited within the anode cavity; (d) a separator between the anode and the cathode; (e) an alkaline electrolyte in contact with the anode and the cathode; and (f) a protective layer deposited on the upper surface of the cathode", and an "alkaline battery further including a gel deposited on the anode within the cavity, the material of the gel including a predetermined amount of electrolyte also present within the anode and a gelling agent including a predetermined amount".

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a high demand for extending the recommended usage period of alkaline dry batteries. For example, from the perspective of improving reliability as an emergency power source during disasters, a recommended usage period of more than 10 years has been required. To extend the recommended usage period, further improvement in the liquid leakage resistance of the battery is necessary.

Means for Solving the Problems

[0005] One aspect of the present disclosure relates to an alkaline dry battery including a bottomed cylindrical case having an open end, a power generation element housed in the case, and a sealing unit for sealing the open end. The power generation element includes a hollow cylindrical positive electrode, a negative electrode filled in the hollow of the positive electrode, and a separator interposed between the positive electrode and the negative electrode. The open end has an annular groove recessed inward to support the sealing unit. An end face of the negative electrode on the open end side is covered with a gel-like shielding layer. The gel-like shielding layer contains an alkaline electrolyte and crosslinked polyacrylic acid. The content of the crosslinked polyacrylic acid in the gel-like shielding layer is 2.0% by mass or more and 3.0% by mass or less.

Advantages of the Invention

[0006] According to the present disclosure, leakage of the alkaline dry battery is suppressed.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure can be obtained. Note that known battery components may be applied to components other than the characteristic parts of the present disclosure. In this specification, when referring to the "range from numerical value A to numerical value B", this range includes numerical value A and numerical value B. For example, "A to B mol%" is synonymous with "A mol% or more and B mol% or less". In the following description, when the lower limit and upper limit of a numerical value regarding a specific physical property or condition are exemplified, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not greater than the upper limit. When a plurality of materials are exemplified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0009] In addition, the present disclosure includes combinations of matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims. That is, as long as no technical contradiction occurs, matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims can be combined.

[0010] The type of the alkaline dry battery according to the present disclosure is not particularly limited, and for example, any of single 1 type to single 4 type may be used, or others may also be used.

[0011] The alkaline dry battery according to an embodiment of the present disclosure includes a bottomed cylindrical case having an opening end, a power generation element housed in the case, and a sealing unit that seals the opening end of the case. The power generation element has a hollow cylindrical positive electrode, a negative electrode filled in the hollow of the positive electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator are impregnated with an alkaline electrolyte. The bottomed cylindrical case has a cylindrical side portion and a bottom portion. The opening end of the case (side portion) has an annular groove recessed inward to support the sealing unit.

[0012] The sealing unit includes, for example, a negative electrode terminal plate, a nail-shaped negative electrode current collector, and a gasket. The negative electrode terminal plate closes the opening of the battery case and functions as a negative electrode terminal. The sealing unit may have an explosion-proof function. The negative electrode terminal plate may have a gas vent hole for discharging gas to the outside when the internal pressure of the battery rises above a certain level and the explosion-proof function is activated. The negative electrode current collector includes, for example, a flange portion having a joint surface joined to the negative electrode terminal plate and a columnar body portion.

[0013] The gasket includes, for example, a boss portion having a through hole penetrating the body portion, an outer peripheral portion in contact with the opening end portion of the case, and a connecting portion connecting the boss portion and the outer peripheral portion. The connecting portion may have a thin portion having an explosion-proof function. The thin portion breaks when the internal pressure of the battery rises above a certain level. In that case, the gas is discharged to the outside through the gas vent hole.

[0014] In order to improve the liquid leakage resistance of the battery, conventionally, efforts have been made to improve the corrosion resistance of the zinc alloy in the negative electrode. Also, efforts have been made to improve the corrosion resistance by adding a corrosion inhibitor to the negative electrode. Further, efforts have been made to improve the shielding property of the separator to suppress impurities moving from the positive electrode to the negative electrode.

[0015] However, as a result of a detailed analysis of batteries that leaked during long-term storage, it was found that minute cracks were formed at the opening end portion of the case of the alkaline dry battery. The minute cracks are formed in a portion recessed inside the annular groove when forming an annular groove for supporting the sealing unit at the opening end portion of the case. Metal ions elute from the minute cracks. When the metal ions migrate and reach the negative electrode, hydrogen gas is generated along with the precipitation of the metal. Since this phenomenon progresses slowly, it did not pose a problem when the storage period was about 5 years. However, as the recommended use period is extended and alkaline dry batteries are stored for more than 10 years, the internal pressure of the battery increases, and the explosion-proof function of the sealing unit or the gasket may be activated, leading to liquid leakage.

[0016] In this embodiment, the end face on the opening end side of the negative electrode is covered with a gel-like shielding layer. The gel-like shielding layer does not necessarily need to completely cover the end face on the opening end side of the negative electrode. However, it is preferable that the gel-like shielding layer covers most (for example, 90% or more) of the end face on the opening end side of the negative electrode. The gel-like shielding layer preferably covers at least the annular region adjacent to the positive electrode via the separator among the end faces on the opening end side of the negative electrode.

[0017] The gel-like shielding layer may be a layer that physically suppresses the movement of metal ions. Also, the gel-like shielding layer may be a layer that captures metal ions. The action of capturing metal ions may be a chemical interaction between the carboxyl group of crosslinked polyacrylic acid and metal ions. The gel-like shielding layer only needs to have the effect of delaying the arrival of metal ions eluted from the recessed portion inside the annular groove to the negative electrode.

[0018] The gel-like shielding layer is a layer that contains an alkaline electrolyte and crosslinked polyacrylic acid and does not contain a negative electrode active material (zinc or a zinc alloy). Such a gel-like shielding layer is approximated to the physical properties of the negative electrode except for not containing a negative electrode active material. Therefore, the gel-like shielding layer containing an alkaline electrolyte and crosslinked polyacrylic acid has excellent adhesion to the end face on the opening end side of the negative electrode. Also, the gel-like shielding layer containing an alkaline electrolyte and crosslinked polyacrylic acid does not substantially inhibit the battery reaction of the negative electrode.

[0019] Crosslinked polyacrylic acid acts as a gelling agent for alkaline electrolytes. It is necessary to use crosslinked polyacrylic acid as the gelling agent for the gel-like shielding layer that shields metal ions. Crosslinked polyacrylic acid is polyacrylic acid crosslinked in a network form. The network structure of crosslinked polyacrylic acid has a high effect of physically suppressing the movement of metal ions and is likely to exhibit the effect of chemically capturing metal ions. On the other hand, if a crosslinked polyacrylate in which the carboxyl group is in a salt form (for example, -COONa) is used as the gelling agent, almost no gelling effect can be obtained in the alkaline electrolyte, and a network structure suitable for shielding metal ions is not formed. Therefore, it is difficult to physically suppress the movement of metal ions and chemically capture metal ions. The carboxyl group of crosslinked polyacrylic acid needs to be in the acid form (-COOH). Also, if non-crosslinked polyacrylic acid is used as the gelling agent, for example, since non-crosslinked polyacrylic acid cannot form a network structure, the effect of shielding metal ions cannot be sufficiently obtained.

[0020] The content of crosslinked polyacrylic acid in the gel-like shielding layer is 2.0 mass% or more and 3.0 mass% or less. The state of the gel-like shielding layer changes significantly depending on the content of crosslinked polyacrylic acid. For example, even if the content of crosslinked polyacrylic acid in the gel-like shielding layer differs by only 0.1 mass%, the viscoelasticity of the gel-like shielding layer can change significantly. Therefore, when the content of crosslinked polyacrylic acid in the gel-like shielding layer is less than 2.0 mass%, the gel-like shielding layer does not have sufficient effects of physically suppressing the migration (movement) of metal ions and capturing metal ions, and it is difficult to prevent liquid leakage due to gas generation in the long term. Also, when the content of crosslinked polyacrylic acid in the gel-like shielding layer exceeds 3.0 mass%, it becomes difficult to cover the end face on the opening end side of the negative electrode with a gel-like shielding layer in a good state.

[0021] The content of crosslinked polyacrylic acid may be 2.0% by mass or more and 2.6% by mass or less. When the content of crosslinked polyacrylic acid exceeds 2.6% by mass, the action of physically suppressing the migration (movement) of metal ions and the action of capturing metal ions tend to saturate gradually. The content of crosslinked polyacrylic acid may be 2.2% by mass or more and 2.6% by mass or less.

[0022] The content of crosslinked polyacrylic acid in the above gel-like shielding layer refers to the content as crosslinked polyacrylic acid with carboxyl groups in acid form. As long as the content of crosslinked polyacrylic acid in the gel-like shielding layer is within the above-mentioned range, additionally, crosslinked polyacrylic acid in salt form (crosslinked polyacrylate) may be included. Also, a part of the carboxyl groups of the monomer units contained in crosslinked polyacrylic acid may be in salt form. In that case, it is only necessary that the content in the gel-like shielding layer of the mass of the acid form portion calculated from the number of moles of the monomer units in acid form contained in crosslinked polyacrylic acid is within the above-mentioned range.

[0023] The 0.5% neutralization viscosity of crosslinked polyacrylic acid at 25 °C may be, for example, 40000 mPa·s to 65000 mPa·s. Here, the "0.5% neutralization viscosity" means the viscosity of an aqueous solution obtained by neutralizing an aqueous solution containing 0.5% by mass of crosslinked polyacrylic acid, and it is a measured value by a B-type viscometer. As the neutralizing agent, an aqueous sodium hydroxide solution (NaOH concentration is 18% by mass) can be used. For example, using 500 g of the neutralized aqueous solution, measure the viscosity after 5 minutes at a temperature of 25 °C and a rotation speed of 60 rpm with a B-type viscometer.

[0024] From the viewpoint of effectively suppressing gas generation, the residual acrylic acid monomer content in crosslinked polyacrylic acid is preferably 1000 ppm or less by mass ratio. Also, the iron content that may be contained as an impurity is preferably 12 ppm or less.

[0025] The alkaline electrolyte used for the gel-like shielding layer may be the same as or different from the alkaline electrolyte impregnated into the positive electrode, negative electrode, and separator. The alkaline electrolyte contains water and an alkali dissolved in the water, and may contain zinc oxide. As the alkali, for example, potassium hydroxide is used. The alkaline electrolyte used for the gel-like shielding layer may be, for example, an aqueous solution containing 30 to 40% by mass of potassium hydroxide and 1 to 3% by mass of zinc oxide.

[0026] The gel-like shielding layer is formed by a gel-like mixture obtained by dissolving crosslinked polyacrylic acid in the alkaline electrolyte. For example, after arranging the positive electrode in the case, an annular groove for supporting the sealing unit is formed at the open end of the case (side portion). After arranging the separator and the gel-like negative electrode, a gel-like mixture of the alkaline electrolyte and crosslinked polyacrylic acid is injected onto the end face of the negative electrode on the open end side of the case. Then, the open end is sealed with the sealing unit, and the open end is caulked to the gasket of the sealing unit to be sealed. Note that the timing of forming the annular groove is not limited to the above, and it may be performed at any timing before placing the sealing unit.

[0027] The gel-like shielding layer may further contain a resin additive having alkali resistance. The resin additive helps to inhibit the contact between metal ions and the negative electrode. As the resin additive, resin particles may be used. The average particle diameter of the resin particles is, for example, 1000 μm or less, may be 200 μm to 800 μm, or may be 400 μm to 600 μm. The average particle diameter of the resin particles is the median diameter in the particle size distribution measured by a laser diffraction scattering type particle size distribution measuring device.

[0028] The resin material constituting the resin particles only needs to have alkali resistance, and examples include polyolefin resins, fluororesins, acrylic resins, etc. For example, polyethylene resin particles, polypropylene resin particles, polytetrafluoroethylene resin particles, etc. may be used.

[0029] As a resin additive, a chelating resin may be used. A chelating resin refers to a resin into which a functional group that forms a chelate (complex) with a metal ion has been introduced. A chelating resin captures a metal ion by forming a chelate with the metal ion. The functional group that forms a chelate may have two or more electron-donating elements such as N, S, O, and P. The chelating resin may be, for example, an iminodiacetic acid type, a polyamine type, a methylglucamine type, or the like.

[0030] In the gel-like shielding layer, the mass ratio of the resin additive to the total of the alkaline electrolyte, the crosslinked polyacrylic acid, and the resin additive is, for example, 20% by mass to 80% by mass, and may also be 40% by mass to 60% by mass.

[0031] From the viewpoint of sufficiently securing the volume of the negative electrode and enhancing the action of physically suppressing the migration (movement) of metal ions and the action of trapping metal ions, the thickness of the gel-like shielding layer is, for example, 0.3 mm to 1.5 mm, and may also be 0.5 mm to 1.0 mm.

[0032] In the case of a single-type alkaline dry battery, the mass of the gel-like shielding layer accommodated in the battery may be about 0.2 g to 1.0 g. In the case of a double-type alkaline dry battery, the mass of the gel-like shielding layer accommodated in the battery may be about 0.1 g to 0.8 g. In the case of a triple-type (LR6) alkaline dry battery, the mass of the gel-like shielding layer accommodated in the battery may be about 0.02 g to 0.2 g. In the case of a quadruple-type alkaline dry battery, the mass of the gel-like shielding layer accommodated in the battery may be about 0.01 g to 0.1 g.

[0033] The end face on the opening end side of the positive electrode (hereinafter, also simply referred to as the "end face of the positive electrode") is preferably flush with the first face in contact with the negative electrode of the gel-like shielding layer or is located on the opening end side of the first face. Thereby, the movement of metal ions eluted from the case and reaching the end face of the positive electrode is physically suppressed by the gel-like shielding layer and is easily trapped by the gel shielding layer.

[0034] The end face of the positive electrode is more preferably flush with the second face on the opening end side of the gel-like shielding layer or located on the opening end side of the second face. Thereby, the movement of metal ions eluted from the case and reaching the end face of the positive electrode is physically suppressed by the gel-like shielding layer with a higher probability and is more likely to be trapped by the gel shielding layer.

[0035] Hereinafter, embodiments of the present invention will be further described with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments.

[0036] FIG. 1 shows a half-sectional view of an example of the internal structure of an alkaline dry battery 10 according to an embodiment. FIG. 2 is a half-sectional view showing an example of the internal structure of an alkaline dry battery according to another embodiment. FIG. 3 is a half-sectional view showing an example of the internal structure of an alkaline dry battery according to still another embodiment. FIG. 4 is a half-sectional view showing an example of the internal structure of an alkaline dry battery according to still another embodiment.

[0037] The cylindrical alkaline dry battery 10 includes a case 1, a hollow cylindrical positive electrode 2 disposed in the case 1, a negative electrode (gel-like negative electrode) 3 filled in the hollow of the positive electrode 2, a separator 4, and an alkaline electrolyte (not shown). The positive electrode 2, the negative electrode 3, the separator 4, and the alkaline electrolyte constitute a power generation element. The alkaline dry battery 10 has an inside-out type structure.

[0038] The case 1 is a bottomed cylindrical case and functions as a positive electrode terminal. The case 1 is obtained, for example, by press-molding a steel plate having a nickel plating layer on the inner surface into a predetermined shape. The outer peripheral surface of the case 1 is covered with an exterior label 8. A conductive film may be formed on the inner surface of the case 1. The hollow cylindrical positive electrode 2 is disposed so as to contact the inner wall of the case 1. The end face of the negative electrode 3 on the opening end side of the case 1 is covered with a gel-like shielding layer 12. The first face of the gel-like shielding layer 12 that contacts the negative electrode is in close contact with the negative electrode 3, and the gel-like shielding layer 12 is integrated with the negative electrode 3. The gel-like shielding layer 12 contains an alkaline electrolyte and crosslinked polyacrylic acid. The content of crosslinked polyacrylic acid in the gel-like shielding layer is 2.0% by mass or more and 3.0% by mass or less.

[0039] In FIG. 1, the end face of the positive electrode 2 is located on the opening end side with respect to the first face in contact with the negative electrode 3 of the gel-like shielding layer 12. Further, the end face of the positive electrode 2 is located between the first face of the gel-like shielding layer 12 and the second face on the side opposite to the first face (opening end side). In FIG. 2, the end face of the positive electrode 2 is flush with the first face of the gel-like shielding layer 12. In FIG. 3, the first face of the gel-like shielding layer 12 is located on the opening end side with respect to the end face of the positive electrode 2. In FIG. 4, the end face of the positive electrode 2 is flush with the second face of the gel-like shielding layer 12.

[0040] The configurations of FIGS. 2 and 3 are preferable from the viewpoint of increasing the capacity of the negative electrode. On the other hand, the configurations of FIGS. 1 and 4 are preferable from the viewpoint of enhancing the action of suppressing the movement of metal ions eluted from the case 1 to the negative electrode 3. From the same viewpoint, it is more preferable that the end face of the positive electrode 2 is located on the opening end side with respect to the second face of the gel-like shielding layer 12.

[0041] The separator 4 is composed of a cylindrical separator 4a and a bottom paper 4b. The cylindrical separator 4a is disposed not only between the positive electrode 2 and the negative electrode 3 but also between the positive electrode 2 and the gel-like shielding layer 12. The separator 4a is disposed along the hollow inner surface of the positive electrode 2 and separates the positive electrode 2 and the negative electrode 3. The bottom paper 4b is disposed at the hollow bottom of the positive electrode 2 and separates the negative electrode 3 and the battery case 1.

[0042] The opening end of the 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 having a cylindrical body portion 6a and a flange portion (head portion) 6b. The flange portion 6b of the negative electrode current collector 6 is welded to the central flat portion of the inner surface of the negative electrode terminal plate 7 at its joint surface. The negative electrode current collector 6 is obtained, for example, by pressing a brass wire into a nail shape of a predetermined dimension. The negative electrode terminal plate 7 is obtained, for example, by press-forming a steel plate having a nickel plating layer or a steel plate having a tin plating layer into a predetermined shape.

[0043] The gasket 5 includes a boss portion 5a, an outer peripheral portion 5c, and a connecting portion 5b that connects the boss portion 5a and the outer peripheral portion 5c. The outer peripheral portion 5c is interposed between the outer peripheral edge portion of the negative electrode terminal plate 7 and the opening end portion of the case 1, and has a role of sealing between the negative electrode terminal plate 7 and the opening end portion of the battery case 1. The opening end portion of the case 1 is caulked to the outer peripheral edge portion of the negative electrode terminal plate 7 through the outer peripheral portion 5c of the gasket 5.

[0044] A thin portion (not shown) is formed in the connecting portion 5b as an explosion-proof valve. The thin portion is configured such that when an abnormal battery internal pressure is reached, stress is intensively applied and it breaks, and the internal gas is discharged. Near the flange of the negative electrode terminal plate 7, a gas vent hole 7h is provided to release gas to the outside when the explosion-proof function by the thin portion of the gasket 5 is activated.

[0045] The body portion 6a of the negative electrode current collector 6 is inserted into a through hole provided in the boss portion of the gasket 5 and is inserted into the negative electrode 3. A sealing agent 11 is interposed between the gasket 5 and the negative electrode current collector 6.

[0046] Hereinafter, the specific configuration of the power generation element of the alkaline dry battery will be further described. For the positive electrode 2, for example, a molded body of a mixture containing a positive electrode active material, a conductive agent, and an alkaline electrolyte is used. To the mixture, a binder such as polyethylene powder and a lubricant such as stearate may be added. As the positive electrode active material, manganese dioxide powder, nickel oxyhydroxide powder, etc. are used. As the conductive agent, graphite powder etc. are used.

[0047] For the gel-like negative electrode 3, a negative electrode of a conventionally known alkaline dry battery may be used. The negative electrode 3 can be, for example, a mixture containing a negative electrode active material, an alkaline electrolyte, and a gelling agent. As the negative electrode active material, zinc alloy powder is used. As the gelling agent, polyacrylic acid, a partial sodium salt of polyacrylic acid, etc. are used. To the mixture, a metal compound with a high hydrogen overvoltage such as indium or bismuth and a surfactant may be added to improve the corrosion resistance of the zinc alloy.

[0048] For the separator 4, for example, a nonwoven fabric mainly composed of polyvinyl alcohol fibers and rayon fibers is used.

[0049] The positive electrode 2, the gel-like negative electrode 3, and the separator 4 each contain an alkaline electrolyte. As the alkaline electrolyte, for example, an aqueous solution containing 30 to 40% by mass of potassium hydroxide and 1 to 3% by mass of zinc oxide is used.

[0050] (Appendix) The following technology is disclosed by the above description. (Technology 1) A bottomed cylindrical case having an opening end portion, A power generation element housed in the case, A sealing unit for sealing the opening end portion, Comprising, The power generation element includes a hollow cylindrical positive electrode, a negative electrode filled in the hollow of the positive electrode, and a separator interposed between the positive electrode and the negative electrode. The opening end portion has an annular groove recessed inward to support the sealing unit. The end face of the negative electrode on the opening end side is covered with a gel-like shielding layer. The gel-like shielding layer contains an alkaline electrolyte and crosslinked polyacrylic acid. An alkaline dry battery in which the content of the crosslinked polyacrylic acid in the gel-like shielding layer is 2.0% by mass or more and 3.0% by mass or less. (Technology 2) The alkaline dry battery according to Technology 1, wherein the content of the crosslinked polyacrylic acid is 2.0% by mass or more and 2.6% by mass or less. (Technology 3) The alkaline dry battery according to Technology 1 or 2, wherein the end face of the positive electrode on the opening end side is flush with the first face in contact with the negative electrode of the gel-like shielding layer or is located on the opening end side of the first face. (Technology 4) The end face of the positive electrode on the opening end side is flush with the second face of the gel-like shielding layer on the opening end side, or is located on the opening end side of the second face, according to the alkaline dry battery described in Technology 1 or 2. (Technology 5) The gel-like shielding layer further contains a resin additive having alkali resistance, according to the alkaline dry battery described in any one of Technologies 1 to 3.

[0051] Hereinafter, embodiments of the present invention will be further described based on examples, but the present invention is not limited to the examples. Here, an alkaline dry battery of a single size (LR6) having the structure shown in FIG. 1 was manufactured.

[0052] 《Example 1》 (1) Preparation of alkaline electrolyte As the alkaline electrolyte, an aqueous solution containing 33% by mass of potassium hydroxide (KOH) and 2% by mass of zinc oxide (ZnO) was used.

[0053] (2) Preparation of positive electrode Electrolytic manganese dioxide powder with an average particle size of 35 μm and graphite powder with an average particle size of 15 μm were mixed at a mass ratio of 94:6. 2 parts by mass of the alkaline electrolyte was added to 100 parts by mass of the mixture, and after sufficient stirring, it was compression molded to obtain a flaky positive electrode mixture. After pulverizing the flaky positive electrode mixture into granules, it was pressure molded into a hollow cylindrical pellet, and the obtained pellet was used as the positive electrode 2.

[0054] In order to intentionally create a situation where iron eluted from Case 1, 0.06 g of an aqueous solution containing 20% by mass of iron (II) sulfate heptahydrate was applied to the end face of the positive electrode on the opening end side of Case 1.

[0055] (3) Preparation of negative electrode A gelling agent (a mixture of polyacrylic acid and a partial sodium salt of polyacrylic acid), an alkaline electrolyte, and zinc alloy powder with an average particle size of 110 μm were mixed at a mass ratio of 0.8:34.2:65.0 to obtain a gel-like negative electrode 3.

[0056] (4) Assembly of battery A case 1 made of a steel plate having a bottomed cylindrical shape and a nickel plating layer on the inner surface was prepared. A positive electrode 2 was inserted into the case 1, and the positive electrode 2 was brought into close contact with the inner wall of the case 1 by a pressing jig. An annular groove for supporting a predetermined sealing unit was formed at the open end of the case 1. A bottomed cylindrical separator 4 was disposed in the hollow of the positive electrode 2. A nonwoven fabric mainly composed of polyvinyl alcohol fibers and rayon fibers was used for the separator 4. After injecting an alkaline electrolyte into the separator 4 and allowing a predetermined time to elapse, the gel-like negative electrode 3 was filled into the separator 4.

[0057] (5) Formation of gel-like shielding layer 98 parts by mass of the alkaline electrolyte prepared in (1) above and 2 parts by mass of crosslinked polyacrylic acid (manufactured by Sumitomo Seika Chemicals Co., Ltd., Aqupec HV-505E), which is a gelling agent, were mixed to prepare a gel-like mixture. 0.1 g of the gel-like mixture was filled so as to cover the end face on the open end side of the negative electrode 3, and a gel-like shielding layer 12 having a crosslinked polyacrylic acid content of 2% by mass was formed. The filling amount of the negative electrode was adjusted so that the end face of the positive electrode 2 was positioned between the first surface and the second surface of the gel-like shielding layer 12. The 0.5% neutralization viscosity of the crosslinked polyacrylic acid at 25°C was 50,000 mPa·s. The viscosity of the gel-like mixture measured with a B-type viscometer under the conditions of a temperature of 25°C and a rotation speed of 30 rpm was 3000 mPa·s.

[0058] (6) Sealing of open end A predetermined sealing unit was disposed so as to close the open end of the case 1, the open end of the case 1 was bent inward, and caulked to the negative electrode terminal plate via a gasket to complete the battery A1.

[0059] Examples 2 to 6, Comparative Example 2 Batteries A2 to A6 of Examples 2 to 6 and battery B2 of Comparative Example 2 were completed in the same manner as in Example 1, except that the content of crosslinked polyacrylic acid (gelling agent) in the gel-like shielding layer 12 and the viscosity of the gel-like mixture at 25°C were changed as shown in Table 1.

[0060] Comparative Example 1 An alkaline dry battery B1 of Comparative Example 1 was completed in the same manner as in Example 1, except that a gel-like shielding layer 12 was not provided on the end face on the open end side of the negative electrode 3.

[0061] 《Comparative Example 3》 The content rate of crosslinked polyacrylic acid (gelator: Carbopol 940 manufactured by Lubrizol) in the gel-like shielding layer 12 was changed to 1.9% by mass, and the gel-like shielding layer 12 was further added with 0.1% by mass of a polymer having hydrolyzable polyacrylonitrile grafted onto the starch main chain (Waterlock A221 obtained from Grain Processing Corporation). The viscosity of the gel-like mixture measured with a B-type viscometer under the conditions of a temperature of 25°C and a rotation speed of 30 rpm was 2,600 mPa·s. An alkaline dry battery B3 of Comparative Example 3 was completed in the same manner as in Example 1, except for the above.

[0062] 《Comparative Example 4》 The content rate of crosslinked polyacrylic acid (gelator) in the gel-like shielding layer 12 was changed to 1.5% by mass, and the gel-like shielding layer 12 was further added with 0.5% by mass of a polymer having hydrolyzable polyacrylonitrile grafted onto the starch main chain. The viscosity of the gel-like mixture at 25°C was changed to 600 mPa·s. An alkaline dry battery B4 of Comparative Example 4 was completed in the same manner as in Comparative Example 3, except for the above.

[0063] 《Comparative Example 5》 Instead of crosslinked polyacrylic acid, the sodium (Na) salt of crosslinked polyacrylic acid (gelator: Sunfresh DK-500B manufactured by Sanyo Chemical Industries, Ltd.) was used. The viscosity of the gel-like mixture measured with a B-type viscometer under the conditions of a temperature of 25°C and a rotation speed of 30 rpm was 370 mPa·s. An alkaline dry battery B5 of Comparative Example 5 was completed in the same manner as in Example 1, except for the above.

[0064] For this Example and the following Examples, 20 alkaline dry batteries were produced respectively. Batteries A1 to A6 are the batteries of Examples 1 to 6, and batteries B1 to B5 are the batteries of Comparative Examples 1 to 5.

[0065] [Evaluation 1] Twenty alkaline dry batteries of each example were stored at a temperature of 45 °C for 40 days (equivalent to 10 years at room temperature), and the amount of gas generated inside the battery was measured by the water displacement method. Table 1 shows the relative values when the amount of gas generated in Comparative Example 1 was set to 100. The smaller the numerical value of the relative value, the greater the effect of suppressing gas generation, and it can be judged as good if it is 60 or less.

[0066]

Table 1

[0067] 《Example 7》 The filling amount of the negative electrode was adjusted so that the end face of the positive electrode 2 was flush with the first surface of the gel-like shielding layer 12 as shown in FIG. 2. Except for the above, the battery A7 of Example 7 was completed in the same manner as in Example 1.

[0068] 《Example 8》 The filling amount of the negative electrode was adjusted so that the first surface of the gel-like shielding layer 12 was positioned closer to the opening end of the case 1 than the end face of the positive electrode 2 as shown in FIG. 3. Except for the above, the battery A8 of Example 8 was completed in the same manner as in Example 1.

[0069] 《Example 9》 The filling amount of the negative electrode was adjusted so that the second surface of the gel-like shielding layer 12 was flush with the end face of the positive electrode 2 as shown in FIG. 4. Except for the above, the battery A9 of Example 9 was completed in the same manner as in Example 1.

[0070] [Evaluation 2] Twenty alkaline dry batteries of each example were stored at a temperature of 45 °C for 40 days (equivalent to 10 years at room temperature), and the amount of gas generated inside the battery was measured by the water displacement method. Table 2 shows the relative values when the amount of gas generated in Comparative Example 1 was set to 100.

[0071]

Table 2

[0072] 《Example 10》 To 50 parts by mass of the gel-like mixture, 50 parts by mass of polyethylene resin particles (manufactured by Corpheric, specific gravity 1 g / cm 3 , particle size 425 - 500 μm) as an alkali-resistant resin additive were mixed. Except for filling 0.1 g of the resulting mixture (i.e., 0.05 g of the gel-like mixture and 0.05 g of the polyethylene resin particles) to cover the end face on the opening end side of the negative electrode 3, the battery A10 of Example 10 was completed in the same manner as in Example 1.

[0073] 《Example 11》 To 50 parts by mass of the gel-like mixture, 50 parts by mass of a chelating resin having a methylglucamine group (manufactured by Mitsubishi Chemical Corporation, DIAION CRB05, average particle size 500 μm) as an alkali-resistant resin additive were mixed. Except for filling 0.1 g of the resulting mixture (i.e., 0.05 g of the gel-like mixture and 0.05 g of the chelating resin) to cover the end face on the opening end side of the negative electrode 3, the battery A11 of Example 11 was completed in the same manner as in Example 1.

[0074] [Evaluation 3] Twenty alkaline dry batteries of each example were stored at a temperature of 45°C for 40 days (equivalent to 10 years at normal temperature), and the amount of gas generated in the battery was measured by the water displacement method. Table 3 shows the relative values when the amount of gas generated in Comparative Example 1 was taken as 100.

[0075]

Table 3

Industrial Applicability

[0076] The alkaline dry battery according to the present disclosure can suppress leakage over a long period of time, and thus is useful as a power source for various electronic devices.

Explanation of Reference Numerals

[0077] 1: Battery case, 2: Positive electrode, 3: Gel-like negative electrode, 4: Separator, 5: Gasket, 5a: Boss part, 5b: Connecting part, 5c: Outer peripheral part, 6: Negative electrode current collector, 6a: Barrel part, 6b: Flange part, 7: Negative electrode terminal plate, 7h: Gas vent hole, 8: Exterior label, 9: Sealing unit, 10: Alkaline dry battery, 11: Sealing agent, 12: Gel-like shielding layer

Claims

1. A bottomed cylindrical case having an open end, A power generation element housed in the case, A sealing unit for sealing the open end, and comprising, The power generation element includes a hollow cylindrical positive electrode, a negative electrode filled in the hollow of the positive electrode, and a separator interposed between the positive electrode and the negative electrode, The open end has an annular groove recessed inward to support the sealing unit, The end face of the negative electrode on the open end side is covered with a gel-like shielding layer, The gel-like shielding layer contains an alkaline electrolyte and crosslinked polyacrylic acid, An alkaline dry battery in which the content of the crosslinked polyacrylic acid in the gel-like shielding layer is 2.0% by mass or more and 3.0% by mass or less.

2. The alkaline dry battery according to claim 1, wherein the content of the crosslinked polyacrylic acid is 2.0% by mass or more and 2.6% by mass or less.

3. The alkaline dry battery according to claim 1, wherein the end face of the positive electrode on the open end side is flush with the first face in contact with the negative electrode of the gel-like shielding layer or is located on the open end side of the first face.

4. The alkaline dry battery according to claim 1, wherein the end face of the positive electrode on the open end side is flush with the second face on the open end side of the gel-like shielding layer or is located on the open end side of the second face.

5. The alkaline dry battery according to claim 1, wherein the gel-like shielding layer further contains a resin additive having alkali resistance.

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