JP2517936C - - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a button-type zinc-air battery used as a power source for a hearing aid or the like. [Summary of the Invention] The present invention relates to an air zinc battery comprising a negative electrode active material mainly composed of zinc and an electrolytic solution, and using oxygen in the air as a positive electrode active material. By limiting the content within this range, the discharge capacity is increased, the liquid leakage resistance during discharge and during long-term storage is improved, and a highly reliable air zinc battery is provided. [Prior art] In recent years, the demand for hearing aids has been rapidly growing as a measure against hearing loss accompanying aging,
Under such circumstances, demands for a hearing aid power supply battery are increasing. Conventionally, mercury batteries have been widely used as the hearing aid power supply. The mercury battery has advantages such as a larger battery capacity, a lower cost per capacity, and a stable discharge voltage as compared with an alkaline manganese battery. The battery needs to be replaced in about a week, mercury used as an anode active material causes pollution, and the specific gravity of mercury is large. For example, a battery having a diameter of 116 mm and a height of 54 mm weighs about 3 g. There is a problem that the weight is relatively heavy. As a battery that solves these problems, a button-type zinc-air battery has attracted attention. Since the above zinc-air battery uses oxygen in the air as the positive electrode active material, it is only necessary to provide the negative electrode active material and the catalyst layer in the battery. Therefore, the internal volume of the negative electrode active material can be increased, and the capacity of the battery can be increased. A possible battery. In addition, the zinc-air battery has various advantages, such as a flat and stable discharge potential, and low pollution and light weight. [Problems to be Solved by the Invention] However, the above zinc-air battery has an air hole for taking in air on the positive electrode can side, so that during natural discharge during discharge or after overdischarge or during long-term storage, etc. Due to the increase in the volume of the negative electrode active material due to the progress of the discharge reaction, the separator containing the electrolyte is pressed against the air electrode side, causing a problem that the electrolyte leaks out from the air holes, and the reliability of the battery increases. Sex will be lost. Therefore, the present invention has been proposed in view of the above-described problems, and provides an air zinc battery having a large discharge capacity, excellent liquid leakage resistance during discharge and long-term storage, and excellent reliability. The purpose is to do so. [Means for Solving the Problems] In order to achieve the above-described object, the present invention provides an air zinc comprising a negative electrode active material mainly composed of zinc and an electrolytic solution, wherein oxygen in the air is used as a positive electrode active material. In the battery, an aqueous solution of potassium hydroxide having a concentration of 32.5 to 36.0% by weight was used as the electrolytic solution, and the amount of the electrolytic solution was 0.1 to 1 AH (ampere hour) equivalent to the negative electrode active material.
28 to 0.30 g. Here, the concentration of the aqueous potassium hydroxide solution and the content of the electrolytic solution with respect to zinc as the negative electrode active material are important. That is, the concentration of the aqueous solution of potassium hydroxide as the electrolytic solution was 32.5 to 36.0% by weight, and the amount of the electrolytic solution corresponding to 1 AH of the negative electrode active material was 0.28 to
By setting the content within the range of 0.30 g, it is possible to increase the discharge capacity and to improve the liquid leakage resistance at the time of discharge and during long-term storage. When the concentration of the electrolyte is less than 32.5% by weight, the battery capacity is reduced. When the concentration is 36.0% by weight or more, the electrolyte is leaked. Regarding the amount of electrolyte, when the amount of electrolyte per 1 AH of the negative electrode active material is less than 0.28 g, the amount of zinc increases, but the volume of the negative electrode active material expands during discharge and presses the positive electrode, resulting in insufficient oxygen supply. In addition, zinc, which is a negative electrode active material, remains as a vermilion discharge, resulting in a decrease in discharge capacity. When the amount of the electrolytic solution is 0.30 g or more, the amount of zinc decreases and the capacity cannot be increased. [Function] By using oxygen for the positive electrode active material, zinc for the negative electrode active material, and a potassium hydroxide aqueous solution of a predetermined concentration for the electrolytic solution, and limiting the amount of the electrolytic solution per 1 AH of the negative electrode active material,
The discharge capacity increases by about 10%. In addition, since the amount of the electrolytic solution is regulated to an optimum value, even if the negative electrode active material expands due to the discharge reaction or does not have an unnecessary electrolytic solution even during long-term storage, the leakage resistance is improved. EXAMPLES Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples. This embodiment is applied to a so-called 44 type (116 mm in diameter, 54 mm in height) button type air zinc battery. As shown in FIG. 1, the button-type zinc-air battery has a negative electrode active material (1) filled in a negative electrode can (6) having a volume considering expansion of the negative electrode active material due to a discharge reaction, and a separator (4). ) Is provided with a positive electrode catalyst layer (2) and a water repellent layer (3), and an air hole (8) for taking in air is formed in the positive electrode catalyst layer (2) and a positive electrode can (5) having a small volume in which air can exist. Is attached by caulking the end portion thereof via a gasket (7). The negative electrode active material (1) was mainly composed of zinc, and usually used was a mixture of zinc sulfide, an electrolytic solution, zinc oxide for controlling self-discharge of zinc, and a thickener. The zinc hydride used had a mercury content of 2% by weight. In addition, zinc oxide contains 5
% By weight. The filling rate of the negative electrode active material (1) having the above composition with respect to the battery internal volume was set to 85%. The positive electrode catalyst layer (2) is formed, for example, by using nickel porous as a current collector and pressing a mixture of carbon and manganese dioxide in a binder made of polytetrafluoroethylene resin onto the current collector. Further, the water-repellent layer (3) provided on the air contact side of the positive electrode catalyst layer (2) is made of a polytetrafluoroethylene-made porous resin or the like, and functions to prevent leakage of the electrolyte. doing. The gasket (7) is made of nylon or the like, and prevents short circuit due to contact with the positive electrode can (6) due to leakage of the negative electrode active material (1). The positive electrode can (5) has two air holes (8) with a diameter of 06 mm for taking in air. Example 1 In a button-type zinc-air battery having the above-described configuration, the concentration of the electrolytic solution was kept constant, and the amount of the electrolytic solution with respect to the capacity of the negative electrode active material was changed to change the sample battery (
Sample 1 to Sample 4 and Comparative Sample 1) were prepared. The electrolyte concentration of each sample battery,
Table 1 shows the amount of filled zinc and the amount of electrolyte. For each of the prepared sample batteries, the initial battery characteristics, discharge characteristics, and liquid leakage after storage were examined. Open circuit voltage and internal resistance for battery initial characteristics, 620Ω for discharge characteristics
The discharge capacity at the time of applying a load, the flat voltage, and the liquid leakage after discharge, and the liquid leakage after storage were as follows: 50 sample batteries were leaked after standing at 60 ° C., 90% relative humidity and 40 days. The number was checked respectively. Table 2 shows the results. The second plotted the characteristics of the discharge capacity with respect to the amount of electrolyte based on the above results.
FIG. 2, A is sample 1, B is sample 2, C is sample 3, D is sample 4, E
Respectively correspond to Comparative Sample 1. From Table 2 and FIG. 2, it can be seen that when the amount of the electrolytic solution is less than 0.28 g / AH, the amount of zinc increases, but the discharge capacity decreases. This is because it is considered that the capacity of the negative electrode active material expands during discharge and presses the positive electrode due to volume expansion, which causes a shortage of oxygen supply, and zinc, which is the negative electrode active material, remains unreacted, thereby reducing the capacity. In addition, since the amount of zinc for setting the electrolyte volume to 0.30 g / AH or more decreases, it is impossible to increase the capacity. Example 2 Next, sample batteries (samples 5 to 9 and comparative samples 2 to 5) were prepared by keeping the amount of the electrolytic solution with respect to the capacity of the negative electrode active material constant and changing the concentration of the electrolytic solution. Table 3 shows the concentration of the electrolyte, the amount of filled zinc, and the amount of the electrolyte for each sample battery. The initial characteristics, discharge characteristics, and liquid leakage after storage of each sample battery were examined. Open circuit voltage and internal resistance for battery initial characteristics, 620Ω for discharge characteristics
The discharge capacity when applying a load, the flat voltage, and the liquid leakage after discharge, and the liquid leakage after storage were as follows. The number was checked respectively. Table 4 shows the results. FIG. 3 plots the characteristics of the discharge capacity with respect to the electrolyte concentration based on the above results. In FIG. 3, F is the result of Comparative Sample 2, G is Comparative Sample 3, H is Sample 5, I is Sample 6, J is Sample 7, K is Sample 8, L is Sample 9, and M is Comparative Sample 4. And N corresponds to the comparative sample 5, respectively. From Table 4 and FIG. 3, the electrolyte solution concentration shows the largest discharge capacity in the vicinity of 34% by weight KOH, and the range of 32.5 to 36% by weight KOH is considered to be a range showing good discharge capacity. . When the electrolyte concentration is 36.5 wt% KOH or more, liquid leakage occurs, and when the electrolyte concentration is less than 32.0 wt% KOH, the discharge capacity decreases. This is because when the amount of potassium hydroxide in the surface layer of the zinc particles is around 34% by weight, it is coordinated with zinc ions and Zn (OH)
₄ easily take the ^2-form, because the discharge state is considered to better hardly become the passivation of zinc. Comparative Example The concentration of the electrolyte was 30% by weight KOH, the amount of zinc charged was 430 mAH, and the amount of the electrolyte was 0.
. A sample battery was prepared in which the electrolyte concentration and the amount of the electrolyte were set outside the range of the present invention. The prepared sample battery was examined for initial battery characteristics, discharge characteristics, and liquid leakage after storage. Open circuit voltage and internal resistance for battery initial characteristics, 620Ω for discharge characteristics
The discharge capacity when a load was applied, the flat voltage, and the liquid leakage after discharge, and the liquid leakage after storage were as follows: 50 sample batteries were leaked after standing at 60 ° C. and 90% relative humidity for 40 days. The number was checked respectively. As a result, among the initial characteristics of the battery, the open circuit voltage was 1.472 V and the internal resistance was 1.0Ω.
Met. In the discharge characteristics, the discharge capacity was 409 mAH and the flat voltage was 1.27.
V, the liquid leakage during discharge was good. Sample battery 5
Forty liquids out of zero were leaked. From these results, it can be seen that, in the comparative example, the electrolytic solution concentration and the electrolytic solution amount were out of the range of the present invention, so the discharge capacity was low, and the liquid leakage after storage was significantly deteriorated. . [Effects of the Invention] As is clear from the above description, in an air zinc battery including a negative electrode active material mainly composed of zinc and an electrolytic solution and using oxygen in the air as a positive electrode active material, the concentration of the electrolytic solution is 32. By using an aqueous solution of potassium hydroxide of 0.5 to 36.0% by weight and limiting the amount of the electrolytic solution to the range of 0.28 to 0.30 g with respect to the equivalent amount of the negative electrode active material 1AH, compared with the conventional battery. As a result, the discharge capacity can be increased by about 10%. In addition, since the amount of the electrolyte is regulated to an optimum value, even if the negative electrode active material expands due to a discharge reaction or during long-term storage, the leakage resistance is improved and the leakage of the electrolyte can be prevented. Therefore, a highly reliable zinc-air battery can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing one configuration example of an air zinc battery to which the present invention is applied. FIG. 2 is a characteristic diagram showing a relationship between the amount of the electrolyte and the discharge capacity when the amount of the electrolyte is changed with respect to the capacity of the negative electrode active material. FIG. 3 is a characteristic diagram showing a relationship between the electrolytic solution concentration and the discharge capacity when the concentration of the electrolytic solution is changed. DESCRIPTION OF SYMBOLS 1 ... Negative electrode active material 2 ... Positive electrode catalyst layer 3 ... Aqueous layer 4 ... Separator 5 ... Positive electrode can 6 ... Negative electrode can 7 ... Gasket 8 ... Air hole

Claims (1)

An air zinc battery comprising a negative electrode active material mainly composed of zinc and an electrolytic solution, wherein oxygen in the air is used as a positive electrode active material, wherein the electrolytic solution has a concentration of 32.5 to 36.0% by weight. A zinc hydroxide aqueous solution, wherein the amount of the electrolyte is 0.28 to 0.30 g relative to 1 AH of the negative electrode active material.