Separator and manganese dry battery comprising same

Abstract

This manganese dry battery uses a separator that includes a base material and a paste adhering to the base material, wherein the paste contains starch particles, and the starch particles include first particles that each have a depression in the surface thereof.

Description

Separator and manganese dry cell equipped therewith Cross-reference of related applications

[0001] This disclosure claims priority rights to Provisional Application 63 / 721040, filed with the United States Patent and Trademark Office on 15 November 2024, and Provisional Application 63 / 726059, filed on 27 November 2024, the entirety of which is incorporated herein by reference.

[0002] The present invention relates to a separator and a manganese dry cell equipped therewith.

[0003] In recent years, batteries have increasingly been used as power sources for high-rate devices, and improvements in the high-rate discharge characteristics of manganese dry cell batteries are desired.

[0004] Patent Document 1 proposes a manganese dry cell in which a separator coated with an adhesive is installed between a manganese dioxide positive electrode and a zinc negative electrode, characterized in that the adhesive is a mixture of starch with a torque of 1000 BU or more when held at 95°C using an 8% Brabender viscograph and starch with a torque of 1500 BU or less when held at 95°C using a 12% Brabender viscograph.

[0005] Patent Document 2 describes a manganese dry cell comprising a bottomed negative electrode zinc can, a positive electrode mixture and electrolyte filled in the negative electrode zinc can via a separator, wherein the separator consists of a wrapping paper and an adhesive adhering to the wrapping paper, the immersion rate of the wrapping paper is 500 seconds / 0.05 ml or less, and the basis weight of the wrapping paper is 55 g / m². ２ The present invention proposes a manganese dry cell in which the adhesive consists of starch, a nonionic surfactant, and a solvent, and the content of the nonionic surfactant in relation to the total weight of the starch, nonionic surfactant, and solvent is 1% by weight or more and 5% by weight or less.

[0006] Japanese Patent Publication No. 11-345602 Japanese Patent Publication No. 2004-063252

[0007] The starch in conventional separators has high swelling properties, which is insufficient for the storage characteristics of manganese dry cell batteries.

[0008] One aspect of the present disclosure relates to a separator for use in a manganese dry cell, wherein the separator comprises a base material and an adhesive adhering to the base material, the adhesive comprising starch particles, and the starch particles comprising first particles having depressions on their surface.

[0009] Another aspect of this disclosure relates to a manganese dry cell comprising a bottomed cylindrical negative electrode container containing zinc, a positive electrode mixture housed in the negative electrode container, an electrolyte, and the above-mentioned separator disposed between the negative electrode container and the positive electrode mixture.

[0010] According to this disclosure, a manganese dry cell is provided that can achieve both excellent high-rate discharge characteristics and excellent storage characteristics.

[0011] This is a longitudinal cross-sectional view of a manganese dry cell according to one embodiment of the present disclosure. This is a schematic diagram showing the structure of a separator according to one embodiment of the present disclosure. This is an SEM image of an example of a first particle. This is an SEM image of an example of a second particle.

[0012] Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings.

[0013] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0014] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0015] The separator used in the manganese dry cell according to this disclosure (hereinafter also referred to as "separator (S)") comprises a substrate and an adhesive adhering to the substrate. The adhesive contains starch particles. The starch particles include first particles having depressions (recesses) on their surface.

[0016] The first particle may have a flattened shape with a depression in the center. The first particle may have a flattened shape like a donut with a depression in the center, or it may have a shape like a red blood cell. The depression should be located on the surface of the particle as viewed from the depth direction of the depression, closer to the center of the surface than the outer edge, that is, roughly near the center of the first particle, and the center of gravity of the depression may be outside the center of gravity of the first particle. In the first particle, on the surface as viewed from the direction of the depression, the outer edge portion other than the central depression (peripheral portion) may not be depressed, or it may be depressed from the peripheral portion toward the center. If the peripheral portion is depressed, the slope of the surface of the central depression may be greater than the slope of the surface of the depression in the peripheral portion. The shape of the first particle may have a depression and a raised portion surrounding the depression (or a flattened shape). The shape of the first particle may have a depression and an annular raised portion surrounding the depression (or a flattened shape). The depressions may be formed on both sides of the first particle, or on one side. The depressions may be formed one on each side of the flattened first particle, or one on one side.

[0017] The manganese dry cell according to this disclosure comprises a bottomed cylindrical negative electrode container containing zinc, a positive electrode mixture housed in the negative electrode container, an electrolyte, and a separator (S) disposed between the negative electrode container and the positive electrode mixture.

[0018] The starch particles contained in the binder gradually swell and gelatinize (alpha-gelatinize) in the electrolyte, developing viscosity and liquid-retaining properties. Through the alpha-gelatinization of the starch particles, the binder draws the electrolyte impregnated in the positive electrode mixture to the interface between the negative electrode canister and the separator (S), promoting the discharge reaction involving the negative electrode canister. It also improves the adhesion between the separator (S) and the negative electrode canister or positive electrode mixture, reducing internal resistance and improving discharge performance. In other words, the binder improves the discharge performance (especially high-rate discharge performance) of manganese dry cell batteries from two perspectives.

[0019] However, if the starch particles swell excessively in the electrolyte, or if the binder deteriorates prematurely (beta-forming), the effect of improving the discharge performance of manganese dry cell batteries decreases in both aspects. In particular, at high temperatures above 45°C, the starch contained in conventional binders deteriorates easily, and the storage properties tend to deteriorate. Deterioration of storage properties leads to phenomena such as a decrease in high-rate discharge performance and a voltage drop from the expected voltage. Generally speaking, it can be said that improving high-rate discharge performance through alpha-forming and improving storage properties are mutually exclusive and difficult to achieve simultaneously.

[0020] In contrast, if the starch particles contained in the binder include first particles with depressions on their surface, it becomes possible to achieve both improved high-rate discharge performance and improved storage characteristics. This is thought to be because the depressions on the surface of the first particles increase the surface area of ​​the starch particles and allow a large amount of electrolyte to be held in the depressions. In other words, even when gelatinization has hardly progressed and the particle shape is generally maintained, the first particles have a high ability to draw the electrolyte into the interface between the negative electrode can and the separator, and can exert an effect that improves the discharge performance (especially high-rate discharge performance) of the manganese dry cell. Furthermore, it is thought that the crystalline structure and molecular structure of the starch in the first particles differ from those of general starch particles, and because gelatinization progresses mildly, deterioration is less likely to occur, and as a result, storage characteristics are significantly improved.

[0021] The effects of the adhesive or first particle described above become more pronounced when the adhesive is attached to at least the surface of the separator (S) (specifically, the substrate of the separator (S)) facing the negative electrode canister. This is because the moisture retention and adhesion of the electrolyte at the interface between the separator (S) and the negative electrode canister greatly affect the high-rate discharge performance. When the adhesive comes into contact with the negative electrode canister, the moisture content on the inner surface of the negative electrode canister increases, promoting improvements in high-rate discharge characteristics and storage characteristics.

[0022] The starch particles are derived from, for example, corn, but are not particularly limited. The first particle may be at least one selected from the group consisting of moist heat-treated starch particles (moist heat-treated starch) and enzyme-treated starch particles (enzyme-treated starch). Moist heat-treated or enzyme-treated starch particles have improved properties such as heat resistance and acid resistance due to changes in their molecular structure, and they become less prone to swelling in the electrolyte. Therefore, they contribute particularly to improving the storage characteristics of batteries.

[0023] The content of the first particles in the starch particles may be, for example, 10% by mass or more. When the starch particles contain 10% by mass or more of the first particles, it becomes easier to achieve both improved high-rate discharge characteristics and storage characteristics of manganese dry cell batteries. The content of the first particles in the starch particles is preferably, for example, 20% by mass to 80% by mass, and more preferably 40% by mass to 70% by mass.

[0024] The starch particles may include a second particle different from the first particle. When the thickener contains multiple types of starch particles, the gelatinization of the multiple types of starch particles proceeds gradually at different times over a long storage period, which is particularly advantageous for improving storage properties. The second particle, which is different from the first particle, is a particle with small surface depressions or no surface depressions, and may be a modified starch such as cross-linked starch or etherified starch.

[0025] The content of the second particle in the starch particles may be, for example, 20% by mass or more. When the starch particles contain the second particle at such a content, it becomes easier to further improve both the high-rate discharge characteristics and storage characteristics of the manganese dry cell.

[0026] The adhesive may be applied in a layer to at least one surface of the substrate of the separator (S). That is, the separator (S) may have an adhesive layer on at least one surface. The adhesive does not need to penetrate to the center of the separator (S) in the thickness direction. The adhesive layer can be formed by applying an aqueous slurry in which the adhesive is dispersed to at least one surface of the substrate and drying it.

[0027] The amount of adhesive adhering to the substrate (mass of the adhesive layer) is 5 g / m² per surface of the substrate. ２ More than 40g / m ２ The following is also acceptable. When the amount of adhesive adhering to the substrate is within this range, improvements in high-rate discharge characteristics and storage characteristics are promoted.

[0028] The adhesive may contain, in addition to starch particles, other components such as binders, thickeners, corrosion inhibitors, and surfactants. The binder primarily serves to adhere the starch particles to the substrate. The thickener primarily adjusts the viscosity of the aqueous slurry containing the dispersed adhesive. The corrosion inhibitor inhibits corrosion of the zinc-containing bottomed cylindrical negative electrode container. The surfactant contributes to the stability of the aqueous slurry containing the dispersed adhesive.

[0029] The binder is not particularly limited, but for example, polyvinyl alcohol, polyacrylamide, etc., can be used.

[0030] The thickening agent is not particularly limited, but examples include methylcellulose, tamarind seed gum, guar gum, and xanthan gum.

[0031] While not particularly limited, Bi compounds such as bismuth chloride and bismuth oxide can be used as anti-corrosion agents.

[0032] The surfactant is not particularly limited, but for example, a nonionic surfactant (e.g., taditol) can be used.

[0033] For the separator base material, paper materials (pulp materials) such as kraft paper are used. The thickness of the base material is, for example, 50 μm to 100 μm.

[0034] The base material may be, for example, a paper material with a basis weight (mass per unit area) of 40 g / m ２ or more and 80 g / m ２ or less.

[0035] When the thickness or basis weight of the base material is within the above range, not only is the strength and liquid absorption of the separator improved, promoting the improvement of the high-rate discharge characteristics and storage characteristics of the manganese dry battery, but the reliability is also improved.

[0036] FIG. 1 shows the structure of an example of a manganese dry battery according to an embodiment of the present disclosure. FIG. 1 is a front view of a part of the manganese dry battery in cross section.

[0037] The negative electrode can 4 is a bottomed cylindrical battery can (zinc can) made of metallic zinc or a zinc alloy. Inside the negative electrode can 4, after installing the separator 3 (separator (S)) on the side surface of the negative electrode can 4 and the bottom paper 13 on the bottom surface, the positive electrode mixture 1 is stored. A flange paper 9 is installed on the positive electrode mixture 1. The flange paper 9 is obtained by punching out cardboard in an annular shape and has a central hole that fits onto a carbon rod. In the central part of the positive electrode mixture 1, a carbon rod 2 obtained by firing a carbon material and subjected to a water-repellent treatment is inserted.

[0038] The sealing body 5 that seals the opening of the negative electrode can 4 is made of resin and has a central hole into which the carbon rod 2 is inserted. After bending the open end of the negative electrode can 4 inward, the sealing body 5 is fitted onto the carbon rod 2.

[0039] On the outer periphery of the negative electrode can 4, a resin tube 8 having heat shrinkability for ensuring insulation is arranged, and the upper end of the resin tube 8 covers the upper surface of the outer periphery of the sealing body 5. The lower end of the resin tube 8 covers the flange portion of the negative electrode terminal plate 6 made of a tin plate arranged on the bottom surface of the negative electrode can 4 via a seal ring 7. The seal ring 7 is formed by punching out cardboard impregnated with paraffin in a ring shape.

[0040] A positive electrode terminal plate 11 made of a tin plate is attached to the top of the carbon rod 2. The positive electrode terminal plate 11 has a cap-shaped portion for fitting the carbon rod and a flat flange portion. An insulating ring 12 made of resin is arranged outside the flat flange portion.

[0041] The metal exterior can 10 made of a cylindrical tin plate is disposed outside the resin tube 8, and its upper and lower ends are bent inward to clamp the insulating ring 12 and the end of the resin tube 8, respectively.

[0042] The separator 3 (separator (S)) is provided with the above-described paste. Fig. 2 schematically shows the structure of the separator 3. In the illustrated example, paste layers 32 are formed on both surfaces of the base material 31. The paste layer 32 is formed by applying a slurry in which a paste containing starch particles 301, Bi compound 302, binder 303, etc. is dispersed onto both surfaces of the base material 31 and drying it. The separator before being put into the battery is in a dry state, and the paste adheres to the base material 31 mainly by the action of the binder 303. In the assembled battery, the electrolyte penetrates into the separator (S), and the starch particles 301 in the paste hold the electrolyte, achieving the desired effect.

[0043] The starch particles preferably include first particles and second particles. Fig. 3 is a SEM image of an example of the first particles, and Fig. 4 is a SEM image of an example of the second particles. The first particles have depressions (concave portions) on their surfaces and have a flat shape like a donut with a non-penetrating center. On the other hand, the second particles do not have such depressions. The second particles can be, for example, general processed starch.

[0044] The manganese dry battery according to the present disclosure is manufactured, for example, by the following manufacturing process. Process A: After applying a slurry containing the above-described paste to at least one (preferably both) surface of the base material and drying it, a paste layer is formed on the surface of the base material to obtain a separator (S).

[0045] Process B: The separator (S) is disposed on the inner surface of the negative electrode can such that the side on which the paste layer is formed faces the inner surface of the negative electrode can.

[0046] Process C: A positive electrode mixture containing an electrolyte is filled into the negative electrode can through the separator (S). As the positive electrode mixture, for example, a mixture of manganese dioxide as a positive electrode active material, acetylene black as a conductive material, and an electrolyte is used. As the electrolyte, for example, an aqueous zinc chloride solution is used.

[0047] Step D: Insert a carbon rod into the positive electrode mixture filled in the negative electrode can. At this time, since the positive electrode mixture is pushed outward by the carbon rod, the electrolytic solution in the positive electrode mixture leaks out to the separator side and reaches the paste layer of the separator. Then, the alpha conversion of the starch particles gradually progresses.

[0048] (Supplementary Note) The following technologies are disclosed by the above description. (Technology 1) A separator used in a manganese dry battery, the separator includes a base material and a paste adhering to the base material, the paste includes starch particles, and the starch particles include first particles having depressions on the surface, separator. (Technology 2) The separator according to Technology 1, wherein the first particles are at least one selected from the group consisting of heat-moisture-treated starch particles and enzyme-treated starch particles. (Technology 3) The separator according to Technology 1 or 2, wherein the content of the first particles contained in the starch particles is 10% by mass or more. (Technology 4) The starch particles include second particles different from the first particles, and the second particles have small depressions on the surface or no depressions on the surface, the separator according to any one of Technologies 1 to 3. (Technology 5) The separator according to any one of Technologies 1 to 4, wherein the paste adheres to at least one surface of the base material in a layer. (Technology 6) The amount of the paste adhering to the base material layer is 5 g / m ２ or more and 30 g / m ２ or less, the separator according to any one of Technologies 1 to 5. (Technology 7) The separator according to any one of Technologies 1 to 6, wherein the thickness of the base material is 50 μm or more and 100 μm or less. (Technology 8) The base material is a paper material with a basis weight of 40 g / m ２ or more and 80 g / m ２ or less, the separator according to any one of Technologies 1 to 7. (Technology 9) A manganese dry battery comprising a bottomed cylindrical negative electrode can containing zinc, a positive electrode mixture housed in the negative electrode can, an electrolytic solution, and a separator according to any one of Technologies 1 to 8 disposed between the negative electrode can and the positive electrode mixture. (Technology 10) The manganese dry battery according to Technology 9, wherein the paste adheres to at least the surface of the base material facing the negative electrode can.

[0049] The following describes embodiments of the present invention in detail, but the present invention is not limited to the following embodiments.

[0050] Example 1: A AA-size manganese dry cell battery A1 was fabricated using a separator (S).

[0051] The separator (S) interposed between the positive electrode mixture and the negative electrode can consists of kraft paper (base material) and adhesive layers formed on both sides of the kraft paper. The kraft paper has a thickness of 70 μm.

[0052] The positive electrode mixture used was a mixture of manganese dioxide, acetylene black, and an electrolyte solution consisting of a 30% by weight aqueous solution of zinc chloride (zinc chloride concentration 2.2 mol / L) in a weight ratio of 50:10:40.

[0053] Here, a sizing agent layer was formed using a slurry prepared by dividing 38 parts by weight of an adhesive material having the following composition into 62 parts by weight of water.

[0054] Component 1: 50 parts by mass of starch particles (a mixture of 10 parts by mass of first particles (moist heat-treated starch particles) and 90 parts by mass of second particles (cross-linked starch)) Component 2: 5 parts by mass of polyvinyl alcohol, 40 parts by mass of polyacrylamide Component 3: 3 parts by mass of xanthan gum Component 4: 0.5 parts by mass of bismuth chloride Component 5: 1.5 parts by mass of nonionic surfactant

[0055] <Comparative Example 1> A manganese dry cell B1 was prepared in the same manner as in Example 1, except that starch particles containing 100% of the second particle (cross-linked starch) and not the first particle were used as component 1.

[0056] [Evaluation] The discharge duration was measured during high-rate discharge initially (3 days after battery fabrication) and after 3 months of storage at 45°C. Specifically, five of each battery were prepared, and continuous discharge was performed with a 3.9Ω resistor. The discharge duration until the cutoff voltage of 0.9V was reached was measured. The average discharge duration of the five batteries was then calculated. This evaluation was carried out under conditions of 20°C. The evaluation results are shown in Table 1. The evaluation results are relative values ​​with the initial discharge duration of battery B1 set to 100.

[0057]

[0058] The manganese dry cell battery described herein is useful as a power source for high-rate devices and the like.

[0059] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0060] 1. Positive electrode mixture 2. Carbon rod 3. Separator 4. Negative electrode can 5. Sealing body 6. Negative electrode terminal 7. Seal ring 8. Resin tube 9. Flange paper 10. Metal outer can 11. Positive electrode terminal plate 12. Insulating ring 13. Bottom paper

Claims

1. A separator for use in a manganese dry cell, wherein the separator comprises a base material and an adhesive adhering to the base material, the adhesive comprising starch particles, and the starch particles comprising first particles having depressions on their surface.

2. The separator according to claim 1, wherein the first particle is at least one selected from the group consisting of moist heat-treated starch particles and enzyme-treated starch particles.

3. The separator according to claim 1, wherein the content of the first particles contained in the starch particles is 10% by mass or more.

4. The separator according to claim 1, wherein the starch particles include second particles different from the first particles, and the second particles have small or no surface depressions.

5. The separator according to claim 1, wherein the adhesive is attached in a layer to at least one surface of the substrate.

6. The amount of adhesive adhering to the substrate is 5 g / m² per surface of the substrate. ２ More than 40g / m ２ The separator according to claim 1, which is as follows:

7. The separator according to claim 1, wherein the thickness of the substrate is 50 μm or more and 100 μm or less.

8. The base material has a basis weight of 40 g / m². ２ 80g / m or more ２ The separator according to claim 1, wherein the paper material is as follows:

9. A manganese dry cell comprising: a bottomed cylindrical negative electrode container containing zinc; a positive electrode mixture housed in the negative electrode container; an electrolyte; and a separator according to claim 1 disposed between the negative electrode container and the positive electrode mixture.

10. The manganese dry cell according to claim 9, wherein the adhesive is attached to at least the surface of the substrate facing the negative electrode can.

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