Alkaline battery and method for manufacturing an alkaline battery

Abstract

To provide an alkaline battery, and a method for manufacturing an alkaline battery.SOLUTION: An alkaline battery accommodates a positive electrode, a negative electrode, a separator, and an electrolytic solution in a container. The electrolytic solution is a potassium hydroxide aqueous solution with a concentration of 40-50%. The negative electrode is formed of a gel-like negative electrode mixture including a negative electrode active material and an alkaline aqueous solution, and the alkaline aqueous solution is an alkaline aqueous solution including potassium hydroxide and sodium hydroxide at a molar ratio within a range of 89:11 to 96:4. The positive electrode is formed of a positive electrode mixture including silver oxide and manganese dioxide, and the blending ratio of manganese dioxide in the positive electrode mixture is 25 to 50 mass%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an alkaline battery and a method for manufacturing an alkaline battery. [Background technology]

[0002] Silver oxide batteries, which use silver oxide as the positive electrode active material, are small and have high capacity. Taking advantage of these characteristics, their application is expanding beyond conventional uses such as watches and calculators to include medical devices. Silver oxide batteries are being improved to meet various requirements, such as cost and electrical characteristics, for application in these new uses. For example, Patent Document 1 discloses a technique for defining the particle size of the negative electrode zinc (the percentage of particles passing through a 330 mesh) in a silver oxide battery for medical device applications used for short periods in heavy-load environments, with the aim of improving heavy-load characteristics. Patent Document 1 also discloses the electrical resistance value of the separator (5~30 mΩ·in 2 It has been shown that by defining ), the closed-circuit voltage characteristics after 1 minute and 10 minutes under predetermined conditions can be obtained. Furthermore, it is stated that by making the negative electrode non-gel-like, the ion migration speed can be kept high, thereby improving heavy-load characteristics, and the battery capacity can be increased by increasing the proportion of zinc-based particles in the negative electrode. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2006-252899 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the positive electrode active material of alkaline batteries, it is possible to consider using manganese dioxide or other materials that are cheaper than silver oxide in combination with silver oxide to reduce costs and make them easier to apply to new uses. In such alkaline batteries, in order to obtain the same electrical characteristics as the aforementioned silver oxide batteries, it is necessary to improve the efficiency of the electrode discharge reaction compared to conventional batteries. Also, silver oxide (7.143 g / cm³) 3 Manganese dioxide (5.02 g / cm³) has a lower specific gravity than manganese dioxide. 3 Adding ) makes it difficult to increase the pellet density, and the battery height tends to increase. If one tries to address this, it becomes impossible to increase the amount of positive electrode material that can be used, which leads to the problem of not being able to obtain sufficient discharge capacity.

[0005] Therefore, the present invention aims to provide an alkaline battery that has excellent discharge characteristics and can be made low-cost. [Means for solving the problem]

[0006] (1) The alkaline battery according to the present invention is an alkaline battery that contains a positive electrode, a negative electrode, a separator, and an electrolyte in a container, wherein the electrolyte is a potassium hydroxide aqueous solution with a concentration of 40-50%, the negative electrode is a gel-like negative electrode mixture containing a negative electrode active material and an alkaline aqueous solution, the alkaline aqueous solution is an alkaline aqueous solution containing potassium hydroxide and sodium hydroxide in a molar ratio of 89:11-96:4, and the positive electrode is a positive electrode mixture comprising a positive electrode active material containing silver oxide and manganese dioxide, wherein the blending ratio of manganese dioxide in the positive electrode mixture is 50% by mass or less.

[0007] By incorporating manganese dioxide in a suitable ratio of 50% by mass or less relative to the positive electrode mixture, while reducing costs, and by providing a 40-50% potassium hydroxide aqueous solution as the electrolyte, and by setting the molar ratio of potassium hydroxide to sodium hydroxide in the gel-like negative electrode electrolyte to a suitable ratio of 89:11 to 96:4, an alkaline battery with excellent discharge characteristics even under heavy load conditions can be provided.

[0008] (2) In the alkaline battery described in (1) of the present invention, it is preferable that the electrolyte is an aqueous potassium hydroxide solution with a concentration of 44 to 50%.

[0009] If a potassium hydroxide aqueous solution with a concentration of 44-50% is used as the electrolyte, it is possible to reliably provide alkaline batteries with excellent discharge characteristics even under heavy load conditions.

[0010] (3) In the alkaline battery according to (1) or (2) of the present invention, it is preferable that the blending ratio of manganese dioxide in the positive electrode mixture is 25 to 44% by mass.

[0011] By setting the manganese dioxide blending ratio to 25-44% by mass, the amount of expensive silver oxide used can be reduced, thereby reliably lowering costs, while also providing alkaline batteries with excellent discharge characteristics even under heavy load conditions.

[0012] (4) In the alkaline battery according to any of (1) to (3) of the present invention, the electrical resistivity of the separator is 250 mΩ·cm 2 The following is preferable:

[0013] The electrical resistivity of the separator is 250 mΩ·cm. 2 By following the steps below, it is possible to reliably obtain alkaline batteries with excellent discharge characteristics even under heavy load conditions.

[0014] (5) In the alkaline battery according to any of (1) to (4) of the present invention, it is preferable that the container comprises a positive electrode can, a negative electrode can, and a gasket that seals the positive electrode can and the negative electrode can.

[0015] A button-type alkaline battery can be provided, which has the aforementioned positive and negative electrodes, a separator, and an electrolyte inside a container consisting of a positive electrode container and a negative electrode container. This alkaline battery is low-cost and has excellent discharge characteristics even under heavy load conditions.

[0016] (6) The manufacturing method of the alkaline battery according to the present invention is a method for manufacturing an alkaline battery that houses a positive electrode, a negative electrode, a separator, and an electrolytic solution in a container. The method includes a gel-like negative electrode mixture containing a mixed aqueous solution formed by mixing an aqueous potassium hydroxide solution with a concentration of 45% and an aqueous sodium hydroxide solution with a concentration of 27% so that the mass ratio of potassium hydroxide to sodium hydroxide is 88:12 to 95:5, and a negative electrode active material, and a positive electrode mixture composed of a positive electrode active material containing silver oxide and manganese dioxide. The positive electrode is composed of a positive electrode mixture in which the mixing ratio of manganese dioxide is 50% by mass or less, and an electrolytic solution composed of an aqueous potassium hydroxide solution with a concentration of 40 to 50%. The method is characterized by housing the positive electrode, the negative electrode, the separator, and the electrolytic solution in the container.

[0017] Manganese dioxide is blended in a suitable ratio of 50% by mass or less with respect to the positive electrode mixture, and while aiming for cost reduction, an aqueous potassium hydroxide solution with a concentration of 40 to 50% is used as the electrolytic solution. By mixing and using an aqueous potassium hydroxide solution and an aqueous sodium hydroxide solution as the electrolytic solution contained in the negative electrode so that the mass ratio is 88:12 to 95:5, the molar ratio of potassium hydroxide to sodium hydroxide in the negative electrode mixture can be set to a suitable ratio of 89:11 to 96:4, and an alkaline battery with excellent discharge characteristics can be manufactured even under heavy load conditions. In addition, by setting the potassium hydroxide added to the negative electrode mixture to 95% by mass or less, the handling property of the negative electrode mixture can be made good.

[0018] (7) In the alkaline battery according to the present invention described in (6), it is preferable to use an aqueous potassium hydroxide solution with a concentration of 44 to 50% as the electrolytic solution.

[0019] If an aqueous potassium hydroxide solution with a concentration of 44 to 50% is used as the electrolytic solution, an alkaline battery with excellent discharge characteristics can be surely manufactured even under heavy load conditions.

[0020] (8) In the alkaline battery according to the present invention described in (6) or (7), it is preferable to use a positive electrode in which the mixing ratio of the manganese dioxide is 25 to 44% by mass.

[0021] By setting the mixing ratio of manganese dioxide to 25 to 44% by mass, it is possible to reduce the amount of expensive silver oxide used, reliably achieve cost reduction, and manufacture an alkaline battery with excellent discharge characteristics even under heavy load conditions.

[0022] (9) In the alkaline battery according to any one of (6) to (8) of the present invention, it is preferable to use a separator having an electrical resistivity of 250 mΩ·cm 2 or less.

[0023] With an electrical resistivity of 250 mΩ·cm 2 or less, by using the following separator, it is possible to reliably manufacture an alkaline battery with excellent discharge characteristics even under heavy load conditions.

Effects of the Invention

[0024] According to the present invention, by blending manganese dioxide and silver oxide in a suitable ratio, while achieving cost reduction, making the electrolyte an aqueous potassium hydroxide solution with a suitable concentration, and adjusting the molar ratio of potassium hydroxide and sodium hydroxide contained in the negative electrode to a suitable ratio, it is possible to provide an alkaline battery with excellent discharge characteristics. By adjusting the blending ratio of manganese dioxide to a more suitable range and adjusting the molar ratio of potassium hydroxide and sodium hydroxide to a more suitable ratio, it is possible to provide an alkaline battery with even better discharge characteristics. Further, by adjusting the electrical resistivity of the separator to a low range, it is possible to provide an alkaline battery with further improved discharge characteristics.

[0025] According to the manufacturing method of the present invention, by mixing an aqueous potassium hydroxide solution and an aqueous sodium hydroxide solution with a specific concentration at a specific mass ratio, preparing a negative electrode together with a negative electrode active material, preparing a positive electrode containing a positive electrode active material in which silver oxide and manganese dioxide are blended at a specific ratio, and using an electrolyte with a specific concentration, it is possible to provide an alkaline battery with good discharge characteristics while achieving cost reduction. By adjusting the manganese dioxide content to a more suitable range and the molar ratio of potassium hydroxide to sodium hydroxide to a more suitable ratio, alkaline batteries with even better discharge characteristics can be manufactured. Furthermore, by adjusting the electrical resistivity of the separator to a lower range, alkaline batteries with even better discharge characteristics can be manufactured. [Brief explanation of the drawing]

[0026] [Figure 1] This is a perspective view showing an alkaline battery according to the first embodiment. [Figure 2] A graph showing the relationship between the molar ratio of potassium hydroxide to sodium hydroxide and the discharge capacity in the negative electrode of the alkaline battery manufactured in the example. [Figure 3] A graph showing the relationship between the electrical resistance of the separator and the discharge capacity in the alkaline battery manufactured in the example. [Figure 4] A graph showing the relationship between potassium hydroxide concentration in the electrolyte and discharge capacity in the alkaline batteries manufactured in the examples. [Figure 5] A graph showing the relationship between the manganese dioxide ratio and discharge capacity in the alkaline batteries manufactured in the examples. [Modes for carrying out the invention]

[0027] The following describes embodiments of the present invention applied to button-type alkaline batteries with reference to the drawings. Note that in the drawings used in the following description, the scale of each component may have been appropriately changed to ensure that each component is recognizable.

[0028] <First Embodiment> Figure 1 is a cross-sectional view showing a button-type alkaline battery according to a first embodiment of the present invention. The battery 1 of this embodiment is a battery in which a positive electrode mixture, a negative electrode mixture, and an electrolyte, etc., described later, are housed in a flat metal container. The metal container has a positive electrode container 2 and a negative electrode container 3.

[0029] The positive electrode can 2 is made of, for example, stainless steel (SUS) with nickel plating and is molded into a flat cylindrical shape (shallow cup shape). This positive electrode can 2 contains the positive electrode mixture 5 and functions as a positive electrode current collector. The negative electrode can 3 is made of a clad material with a three-layer structure having, for example, an outer surface layer made of nickel, a metal layer made of stainless steel (SUS), and a current collector layer made of copper, and is molded into a flat cylindrical shape (shallow cup shape). The negative electrode can 3 also has a circular opening 3a that is folded over, and a ring-shaped gasket 4 made of nylon is fitted into the opening 3a.

[0030] The negative electrode can 3 is fitted into the circular opening 2f of the positive electrode can 2 from the side of the opening 3a where the gasket 4 is attached, and the opening 2f of the positive electrode can 2 is crimped toward the gasket 4 to seal it, thereby forming a disc-shaped (button-shaped or coin-shaped) container (case) 8. A sealed space 8S is formed inside the container 8. The gasket 4 insulates and seals the positive electrode can 2 and the negative electrode can 3. The sealed space 8S contains the positive electrode mixture 5, separator 6, negative electrode mixture 7, and an electrolyte (not shown), with the positive electrode mixture 5 on the positive electrode can 2 side and the negative electrode mixture 7 on the negative electrode can 3 side, separated by the separator 6.

[0031] The positive electrode mixture 5 contains a positive electrode active material, a conductive agent, an electrolyte, a binder, and additives. The positive electrode active material is preferably one that can be used as a positive electrode active material when zinc or a zinc alloy is used as the negative electrode active material. For example, the positive electrode active material can be a mixture of silver oxide powder (Ag2O powder) and manganese dioxide powder (MnO2 powder). Silver nickelite (AgNiO2) may be further added to the positive electrode active material. Graphite can be used as a conductive additive. Hydrogen storage alloys (LaNi5) can be used as additives.

[0032] When the positive electrode active material is a mixture of silver oxide powder and manganese dioxide powder, it is preferable that the manganese dioxide is contained in the positive electrode mixture at a concentration of 50% by mass or less. The manganese dioxide content in the positive electrode mixture is preferably 25 to 50% by mass, and more preferably 25 to 44% by mass. By keeping the manganese dioxide content within the range described above, the amount of silver oxide used can be reduced, lowering costs while simultaneously improving discharge characteristics. In particular, it is possible to prevent capacity degradation at the end of discharge during high-current discharge. As an example, manganese dioxide having a MnO2 content of 91.0% or more, a particle size of 75 μm or less content of 80.0% or more, and an alkali potential of 220 mV or more can be used. In this specification, when the upper and lower limits of ingredient content are indicated using "~", unless otherwise specified, it refers to a range that includes both the upper and lower limits. Therefore, 25-50% by mass means 25% by mass or more and 50% by mass or less.

[0033] The negative electrode mixture 7 preferably contains, for example, a negative electrode active material, a thickener, an electrolyte (alkaline aqueous solution), and other additives such as zinc oxide. Zinc oxide (ZnO) functions as a conductivity stabilizer. The additives may also include viscoelastic modifiers, resin powders, and the like. For example, zinc powder or zinc alloy powder can be used as the negative electrode active material. As a thickening agent, polyacrylic acid or carboxymethylcellulose, or a mixture of polyacrylic acid and carboxymethylcellulose, is preferred. Using polyacrylic acid or carboxymethylcellulose can improve the hydrophilicity and liquid retention of the negative electrode mixture 7 in relation to the electrolyte.

[0034] The electrolyte contained in the negative electrode mixture 7 is preferably an alkaline aqueous solution, particularly a mixed aqueous solution of potassium hydroxide (KOH) aqueous solution and sodium hydroxide (NaOH) aqueous solution. When the negative electrode mixture 7 is obtained as a gel, it is preferable that it contains potassium hydroxide and sodium hydroxide in a molar ratio of 89:11 to 96:4, and more preferably in a molar ratio of 89.70:10.30 to 95.76:4.24. This negative electrode mixture 7, when combined with an electrolyte (a 30-50% KOH aqueous solution) having the composition described later, not only exhibits excellent conductivity but also allows the electrolyte to be retained around the negative electrode active material (Zn) until the end of discharge. This improves the utilization efficiency of the active material and makes it possible to provide an alkaline battery with excellent discharge characteristics.

[0035] The alkaline aqueous solution used in the negative electrode mixture 7 is a 45% potassium hydroxide aqueous solution and a 27% sodium hydroxide aqueous solution. The ratio of potassium hydroxide aqueous solution to sodium hydroxide aqueous solution added should be in the range of 88:12 to 95:5 by mass ratio, for example, it can be 91:9 by mass ratio. Based on the above relationship, potassium hydroxide and sodium hydroxide in the negative electrode mixture 7 are contained in the negative electrode mixture 7 in a molar ratio of 89:11 to 96:4, more specifically in a ratio of 89.70:10.30 to 95.76:4.24. By setting the potassium hydroxide aqueous solution addition ratio to 88-95% by mass, the desired electrical characteristics (discharge capacity) of the battery can be obtained. Furthermore, by setting the potassium hydroxide aqueous solution addition ratio to 95% by mass or less, the handling properties of the negative electrode mixture can be improved, making it easier to handle the negative electrode mixture when manufacturing alkaline batteries. To obtain such battery electrical characteristics and handling properties of the negative electrode mixture, the concentration and addition ratio of the alkaline aqueous solution can be appropriately adjusted so as to match the molar ratio of potassium hydroxide to sodium hydroxide in the negative electrode mixture 7 described above. In this specification, the concentration of alkaline aqueous solutions is expressed as a mass fraction (mass percentage concentration) unless otherwise specified.

[0036] The viscoelasticity modifier is formulated as needed to make the viscoelasticity of the negative electrode binder 7 such that good handling properties can be obtained and to improve productivity. As this viscoelasticity modifier, a resin powder that does not react with the strongly alkaline electrolyte solution is used. For example, polytetrafluoroethylene, polypropylene, polyamide, polyethylene powder, acrylic resin, etc. are used. Here, a state where there is no chemical reaction with the electrolyte solution and the electrolyte solution is not absorbed is regarded as a state where there is no reaction with the electrolyte solution.

[0037] The separator 6 is interposed between the positive electrode binder 5 and the negative electrode binder 7, and an insulating film having a large ion permeability and high mechanical strength is used. The separator 6 can be an applicable one used for the separator of the battery. Among them, those having an electrical resistivity of about 250 mΩ·cm 2 or less are preferred. The separator 6 is made of cellophane, a graft film, etc. These materials may be used in combination, or the required number of films or sheets made of the same kind of material may be stacked and used. By configuring the separator 6 from a material having an electrical resistivity of about 250 mΩ·cm 2 or less, an alkaline battery excellent in conductivity can be configured in combination with the electrolyte solution described later.

[0038] In this embodiment, an aqueous potassium hydroxide solution with a concentration of 40 to 50% can be used as the electrolyte solution filled in the container 8. The concentration of the aqueous potassium hydroxide solution is preferably 44 to 50%, and more preferably 45 to 50%. If the concentration of the electrolyte solution is within the above range, sufficient conductivity can be obtained. The higher the concentration of potassium hydroxide, the better the conductivity. However, if it exceeds 50%, there is a concern about the deterioration of conductivity, and there is a possibility that a sufficient discharge capacity cannot be obtained.

[0039] "Method for manufacturing an alkaline battery" To manufacture alkaline battery 1, a positive electrode mixture and a negative electrode mixture are prepared, an electrolyte is injected into the positive electrode container 2, and then the positive electrode mixture 5 is placed inside the positive electrode container. Next, the separator 6 and gasket 4 are assembled into the positive electrode container 2, an electrolyte is injected, the negative electrode mixture 7 is placed, and then the negative electrode container 3 is assembled and sealed to obtain alkaline battery 1. To explain in more detail, to manufacture the alkaline battery 1, a pelletized positive electrode mixture 5 is filled into a positive electrode container 2. Next, a separator 6 is laid on top of the positive electrode mixture 5, and a gasket 4 is pressed into the positive electrode container 2. Then, a gel-like negative electrode mixture 7 is placed on top of the separator 6, and after filling with electrolyte, the negative electrode container 3 is placed on top of these. Furthermore, the open edge of the positive electrode container 2 is crimped to seal the case 8, thereby obtaining the alkaline battery 1 shown in Figure 1. When placing the gel-like negative electrode mixture 7 on the separator 6, the negative electrode mixture 7, which has good handling properties and is formulated as an electrolyte with potassium hydroxide and sodium hydroxide in a molar ratio of 89:11 to 96:4, can be placed in the required amount of negative electrode mixture 7 without any problems.

[0040] The alkaline battery 1 of this embodiment incorporates manganese dioxide in a suitable ratio of 50% by mass or less relative to the positive electrode mixture, thereby reducing the amount of expensive silver oxide used and lowering costs. Furthermore, by providing a 40-50% potassium hydroxide aqueous solution as the electrolyte and setting the molar ratio of potassium hydroxide to sodium hydroxide in the electrolyte contained in the gel-like negative electrode to a suitable ratio of 89:11-96:4, capacity degradation can be prevented even under heavy load conditions until the end of discharge, providing an alkaline battery 1 with excellent discharge characteristics.

[0041] In this embodiment, an alkaline battery 1 comprising a container 8 consisting of a metal positive electrode container 2 and a negative electrode container 3 has been described. However, the container is not limited to metal; an alkaline battery may be constructed from a positive electrode container and a negative electrode container made of a laminate film of metal foil and a resin layer. The container configuration is not particularly limited, and any form of container used in general batteries may be used. [Examples]

[0042] A prototype button-type battery with an internal structure shown in Figure 1, measuring 11.6 mm in diameter and 5.4 mm in height, was fabricated and used for the tests described later. The positive electrode casing of this button-type battery is made of stainless steel, and the negative electrode casing consists of a three-layer clad material made of nickel, stainless steel, and copper. As will be described later, an alkaline battery can be prototyped by placing a positive electrode mixture, separator, negative electrode mixture, and electrolyte inside a container consisting of a positive electrode can and a negative electrode can, as shown in Figure 1, attaching a gasket, and crimping and sealing the positive electrode can.

[0043] Cathode fabrication: A cathode was fabricated in pellet form by press molding 794.0 mg of a cathode mixture, which consisted of 65.0% by mass of silver oxide (Ag2O) as the active material, 31.0% by mass of manganese dioxide (MnO2) containing an acrylic polymer as a binder, 3.0% by mass of graphite as a conductive additive, and 1.0% by mass of hydrogen storage alloy (LaNi5). In preparing this pelletized positive electrode, we also manufactured other positive electrode pellets with six different manganese dioxide content levels: 0, 25, 39, 42, 49, and 59% by mass, and used them to create prototype alkaline batteries. Fabrication of the negative electrode: A gel-like anode mixture was prepared by mixing 58.4% by mass of zinc (Zn) powder, which is the active material, 0.5% by mass of polyacrylic acid, which is the thickening agent, 2.8% by mass of carboxymethylcellulose, and 38.3% by mass of electrolyte for the anode mixture. Five different electrolytes for the negative electrode mixture were prepared using a 45% potassium hydroxide aqueous solution and a 27% sodium hydroxide aqueous solution, with the molar ratio of potassium hydroxide to sodium hydroxide in the negative electrode mixture ranging from 83:17 to 96:4, according to the mixing ratios described below. Each prototype alkaline battery was fabricated using a different electrolyte mixture. The five mixing ratios correspond to a potassium hydroxide molar ratio of 83%, 90%, 92%, 93%, and 96%.

[0044] Assembly process: 30.2 μL of a 30-50% potassium hydroxide aqueous solution was injected as the electrolyte into a positive electrode can with an outer diameter of 11.6 mm. The pellet-shaped positive electrode mixture was placed on the inner bottom surface of the positive electrode can, and two layers of cellophane and graft film laminated separators were placed on top of each other. Finally, a nylon gasket was assembled into the positive electrode can. Each prototype alkaline battery was constructed using four different compositions of potassium hydroxide aqueous solutions, as described later, as the electrolyte. Next, the negative electrode mixture was placed on the separator by leveling it off, the negative electrode container was assembled, and the container was crimped and sealed. Through the above process, a prototype button-shaped alkaline battery (so-called 44 size) with a diameter of 11.6 mm and a height of 5.4 mm was fabricated. The separators had electrical resistances of 176, 250, and 525 mΩ·cm. 2 We used different types of materials to create several prototype alkaline batteries. The electrical resistance of such separators can usually be obtained by adjusting various conditions such as the thickness of the cellophane and graft film, and the grafting rate of the graft film (the ratio of the weight of graft chains to the weight of the substrate in graft polymerization). The following tests were conducted on the several prototype alkaline batteries described above.

[0045] Constant current (10mA) discharge tests were performed on each prototype alkaline battery, and the discharge capacity value at COV 1.0V was determined. The constant current (10mA) discharge test is equivalent to a heavy load test for button-type alkaline batteries. Table 1 and Figure 2 below show the molar ratio of potassium hydroxide and the discharge capacity measurement results of the prototype alkaline batteries obtained when the molar ratio of potassium hydroxide and sodium hydroxide in the aforementioned negative electrode electrolyte was changed to produce multiple alkaline batteries. In the negative electrode mixture, the molar ratio of potassium hydroxide to sodium hydroxide is set to 100. Therefore, dividing 100 by the molar ratio of potassium hydroxide shown in Table 1 gives the molar ratio of sodium hydroxide. Two prototype alkaline batteries with different molar ratios were prepared and tested, so the obtained discharge capacity values ​​represent the average of the two prototype alkaline batteries.

[0046] [Table 1]

[0047] From the relationships shown in Table 1 and Figure 2, it was found that the electrolyte in the negative electrode mixture of alkaline batteries should preferably be an alkaline aqueous solution containing potassium hydroxide and sodium hydroxide in a molar ratio of 89:11 to 96:4. Even within the above range, it can be seen that alkaline batteries with particularly excellent discharge capacity can be obtained by selecting a range of 90:10 to 96:4.

[0048] Table 2 and Figure 3 below show the results of measuring the discharge capacity of prototype alkaline batteries obtained by fixing the molar ratio of potassium hydroxide to sodium hydroxide in the negative electrode mixture to 93, and using various separators with different electrical resistances when manufacturing alkaline batteries as described above. In the negative electrode mixture, the molar ratio of potassium hydroxide to sodium hydroxide is set to 100. Therefore, the molar ratio of sodium hydroxide is 7. In addition, two alkaline batteries using separators with different electrical resistances were prepared and subjected to testing, so the obtained discharge capacity values ​​are the average values ​​of the two prototype alkaline batteries.

[0049] [Table 2]

[0050] As shown in Table 2 and Figure 3, the electrical resistance of the separator is 500 mΩ·cm 2 Alkaline batteries exceeding a certain value have a lower discharge capacity, so the electrical resistance of the separator is 500 mΩ·cm. 2 The following is desirable: Regarding the electrical resistance of the separator, 250 mΩ·cm 2 The following conditions demonstrate that the discharge capacity can be sufficiently high.

[0051] Table 3 and Figure 4 below show the results of measuring the relationship between each prototype alkaline battery and its discharge capacity, after fabricating several prototype alkaline batteries by changing the potassium hydroxide concentration of the electrolyte contained in the container along with the positive and negative electrodes.

[0052] [Table 3]

[0053] As shown in Table 3 and Figure 4, the prototype alkaline battery with a potassium hydroxide concentration of 30% in the electrolyte showed a significant decrease in discharge capacity, while the prototype alkaline battery with a concentration of 44-50% obtained excellent discharge capacity. In light of the results in Table 3 and Figure 4, it is considered desirable to use a potassium hydroxide concentration in the electrolyte in the range of 40-50%, and to reliably obtain excellent discharge capacity, the range of 44-50% is considered desirable.

[0054] Table 4 and Figure 5 below show the results of measuring the relationship between the manganese dioxide content and discharge capacity in several prototype alkaline batteries, which were fabricated by changing the manganese dioxide content ratio in the positive electrode mixture, with respect to silver oxide and manganese dioxide that constitute the positive electrode mixture.

[0055] [Table 4]

[0056] The alkaline battery shown in Table 4 and Figure 5, with a manganese dioxide content of 0% by mass, is an alkaline battery using a positive electrode active material consisting solely of silver oxide. By replacing 50% or less by mass of silver oxide with manganese dioxide, it was possible to obtain an alkaline battery with a small rate of discharge capacity reduction. Furthermore, it was found that if the manganese dioxide content is 44% by mass or less, more specifically in the range of 25-44% by mass, an alkaline battery with almost no reduction in discharge capacity can be provided compared to the prototype alkaline battery using a positive electrode active material consisting solely of silver oxide. [Explanation of symbols]

[0057] 1...Battery, 2...Positive electrode can, 3...Negative electrode can, 4...Gasket, 5...Positive electrode mixture, 6...Separator, 7...Negative electrode mixture, 8...Container (case), 8S...Sealed space.

Claims

1. This is an alkaline battery in which a positive electrode, a negative electrode, a separator, and an electrolyte are contained within a container. The electrolyte is a potassium hydroxide aqueous solution with a concentration of 40-50%. The negative electrode consists of a gel-like negative electrode mixture containing a negative electrode active material and an alkaline aqueous solution, and the alkaline aqueous solution is an alkaline aqueous solution containing potassium hydroxide and sodium hydroxide in a molar ratio of 89:11 to 96:

4. An alkaline battery characterized in that the positive electrode consists of a positive electrode mixture comprising a positive electrode active material containing silver oxide and manganese dioxide, and the proportion of manganese dioxide in the positive electrode mixture is 50% by mass or less.

2. The alkaline battery according to claim 1, characterized in that the electrolyte is an aqueous potassium hydroxide solution with a concentration of 44 to 50%.

3. The alkaline battery according to claim 1 or 2, characterized in that the proportion of manganese dioxide in the positive electrode mixture is 25 to 44% by mass.

4. The electrical resistivity of the aforementioned separator is 250 mΩ·cm. ２ The alkaline battery according to claim 1 or 2, characterized in that it is as follows:

5. The alkaline battery according to claim 1 or 2, characterized in that the container comprises a positive electrode can, a negative electrode can, and a gasket sealing the positive electrode can and the negative electrode can.

6. This is a method for manufacturing an alkaline battery in which a positive electrode, a negative electrode, a separator, and an electrolyte are contained within a container. A negative electrode comprising a gel-like negative electrode mixture containing a negative electrode active material and a mixed aqueous solution obtained by mixing a 45% potassium hydroxide aqueous solution and a 27% sodium hydroxide aqueous solution in a mass ratio of 88:12 to 95:5, A positive electrode comprising a positive electrode mixture containing silver oxide and manganese dioxide as positive electrode active materials, wherein the proportion of manganese dioxide in the positive electrode mixture is 50% by mass or less, Prepare an electrolyte solution consisting of a 40-50% potassium hydroxide aqueous solution, A method for manufacturing an alkaline battery, characterized in that the positive electrode, the negative electrode, the separator, and the electrolyte are contained within the container.

7. The method for manufacturing an alkaline battery according to claim 6, characterized in that a potassium hydroxide aqueous solution with a concentration of 44-50% is used as the electrolyte.

8. A method for manufacturing an alkaline battery according to claim 6 or 7, characterized in that a positive electrode having a manganese dioxide blending ratio of 25 to 44% by mass is used.

9. Electrical resistivity is 250 mΩ·cm ２ A method for manufacturing an alkaline battery according to claim 6 or 7, characterized by using the following separator.

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