JPS58225582A - Button-type air cell - Google Patents

Abstract

PURPOSE:To enhance the preservation performance and the electric discharge characteristic of a button-type air cell by regulating the wettability of a positive catalyst by restricting the density of catalyst packed into a core member to within a specified range. CONSTITUTION:A positive catalyst 5 principally consists of active carbon, graphite and managnese oxide. In preparing it, after 1 part by weight of carbon (active carbon plus graphite) and 1.5 parts by weight of managanese oxide are preliminary mixed, wet mixing is performed by using 2.4 times the total quantity of these principal components of water. Next, 1 part by weight of the thus prepared wet mixture is mixed with 0.2-0.4 part by weight of the solid component (tetrafluoroethylene) of an aqueous fluorine-resin dispersion. Then the thus obtained mixture is applied to and packed into a core member by means of a roller. Next, thus obtained catalyst is dried under condition of 60-80 deg.C, and the thickness is restricted so that the packing density of the catalyst becomes 0.95- 1.21g/cm<3> by performing roller press again. After that, the thus pressed positive catalyst 5 is punched into a diameter which can be placed in a case 1, and thermally treated below the melting point of tetrafluoroethylene.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a button-type air battery.

Conventional configurations and their problems Recently, with the aging of the population, the popularity of hearing aids has gradually increased. Conventionally, mercury batteries have been mainly used as a power source for hearing aids. However, the R44 type has 2oomA.
Due to the low battery capacity and battery capacity, it is necessary to dispose of the batteries in about two weeks, and there is a growing demand for batteries with even higher capacity.

Therefore, so-called button-type batteries that use oxygen in the air as the positive electrode active material, zinc as the negative electrode via a separator, and alkaline aqueous solution as the electrolyte have attracted attention.

This battery is characterized by the use of an oxygen-activated catalyst instead of the jTE electrode active material as in conventional batteries. Therefore, only a small volume is required for the positive electrode active material, and the filling amount of the negative electrode active material can be increased by that amount.

However, since the battery case has holes for air intake, the catalyst formulation and leakage resistance are important points.

Conventionally, there have been two methods for producing catalysts: (1) a dry method and (2) a wet method. The former is a method in which activated carbon, graphite, manganese oxide, ethylene tetrafluoride powder, etc. are mixed in a dry state, the mixed powder is press-molded together with a core material forming a current collector in a mold, and then heat-treated. On the other hand, the latter is a method in which activated carbon, graphite, and manganese oxide are premixed, an aqueous dispersion of tetrafluoroethylene is added as a binder to make it wet, and the mixture is applied to the core material using a roller and then dried. be. However, the dry method is not suitable for mass production due to the difficulty in handling the materials, and also lacks uniform mixing properties due to the difference in specific gravity between the powders. On the other hand, the wet method does not have these points and is relatively commonly used. - However, even in this wet method, there was a problem that there were many variations in catalyst properties, making it difficult to obtain a satisfactory positive electrode for a button-type air battery.

Purpose of the Invention As a result of various studies on catalyst characteristics, the present invention has revealed that it is greatly influenced by the packing density of the core material, and by setting the packing density within a predetermined range, it is possible to improve the catalyst characteristics in button-type air cells. This is aimed at improving battery storage characteristics.

The structure of the invention, that is, the present invention has a catalyst packing density of 0.95 in the core material.
~1,21 y7 ca suppresses wetting of the positive electrode catalyst and improves storage stability and discharge characteristics.

DESCRIPTION OF EMBODIMENTS As an example of the present invention, an R44 type (public house, capacity 400 mA h Ml, 6 gates, height 6.4 m) will be described below as an example of the present invention.
m) button type air battery will be explained as an example. FIG. 1 is a half-sectional view of the battery of the present invention. In the figure, 1 is a positive electrode case with air holes 2 formed in its bottom surface. 3 is air diffusion paper, 4 is a water-repellent membrane made of Teflon, and 5 is a positive electrode catalyst, which is a feature of the present invention. Its composition is mainly composed of activated carbon, graphite, and manganese oxide, and its weight ratio is premixed with manganese oxide at a ratio of 1.5 to 1 of the total amount of carbon (activated carbon + graphite). Wet mix with 2.4 parts by weight of water. The amount of water added is preferably in the range of 2.2 to 2.6 times. The reason for this is that if it is less than 2.2 times, the viscosity becomes high, and when the net is applied to the core material with a roller, the net will meander, making it difficult to apply uniformly. On the other hand, if it is 2.6 times or more, the water content is too high and water is pushed out during coating, resulting in poor n1 workability and the mixture and water separate, making it difficult to maintain a uniform composition. Therefore, 2.2 to 2.64 times is preferable. Add the above-mentioned aqueous dispersion of fluororesin to the wet mixture prepared in this way at a ratio of 0.2 to 0.4 to 1 part of the mixture in terms of solid content (tetrafluoroethylene). Add and mix.

This mixture is applied and filled onto the core material using a roller. The thickness of the catalyst at this time was regulated to 0.5rrvn. This is the thickest dimension allowed to maximize the capacity of a button-type air battery, and is also suitable in terms of battery characteristics.

Next, the catalyst was dried at 60-8oC and the packing density of the catalyst was reduced to 0.95F m3 by roller press again.
The thickness was regulated to be ~1.21p/Q-.

The packing density of the catalyst in this core material significantly affects the catalyst properties. That is, it was found from the discharge characteristic curve shown in FIG. 2 that the filling density during this period was the most rapid.

The positive electrode catalyst 5 pressurized in this way is punched to a diameter that fits into the case 1 and is below the melting point of tetrafluoroethylene, here 260 mm.
It was heat treated with C. In FIG. 1, 6 is a separator, 7 is a nonwoven fabric that is a liquid-containing material, 8 is a negative electrode active material made of zinc, 9 is a sealing plate, 10 is a gasket made of nylon,
11 This is a seal paper to prevent oxygen from entering the battery system in order to improve storage characteristics. The electrolyte used was a 10 molar caustic potassium aqueous solution saturated with zinc oxide.

Next, let the packing density of the positive electrode catalyst core material be 0.859/cA/? :, R44 type air battery A, 0.95
y/CrA battery B, 1.10ji/cm battery C, 1,219/crd battery and 1.
A battery E with a concentration of 309/cl was prepared and a bacterial comparison was performed.

1 Initial Static Characteristics The open circuit voltage was measured by measuring the battery voltage 5 minutes after the sticker paper was removed. From the results in this table, the open circuit voltage in the closed state is the same for each configuration, but the internal resistance is the highest in A, which has a low catalyst packing density, and the battery voltage 5 minutes after the seal paper is removed (return voltage) As is clear from FIG. 2, the higher the catalyst packing density, the faster the speed.

2. Storage characteristics: 4 at a temperature of 60C for the three types of batteries A, C, and E mentioned above.
The battery was stored for 0 days, and its storage characteristics were investigated by comparing the battery voltage 5 minutes after the sticker paper was removed with that immediately after manufacture.

As a result, the initial voltage of battery A was 1.390V, and the voltage was 1.360V after storage. Also, battery E is initial 1
．． The high voltage was 420V, but it was 1.360V after storage.
When this battery was disassembled, it was found that the positive electrode catalyst was significantly wetted by 1%.

On the other hand, battery C had a high initial voltage of 1.420 V, and maintained a voltage of 1.400 V after storage, although it slightly deteriorated.

Furthermore, the closed circuit voltage when loaded with 620Ω is 1.280 for battery C.
V ca-) 7j (For D K, both batteries A and E are 1
．． It showed 240V, confirming whether the catalyst had deteriorated after storage.

Effects of the Invention Accordingly, the present invention improves catalyst characteristics and battery storage customization by setting the packing density for the core material of the catalyst in the positive electrode to 0.95 to 1.21 y/cdl. .

[Brief explanation of the drawing]

FIG. 1 is a half-sectional view of a button-type air cell according to an embodiment of the present invention, and FIG. 2 is a diagram showing the discharge characteristics of the same cell. 1...Positive electrode case, 2...Air hole, 5
・・Positive electrode catalyst, 6... Separator, 7...
... Impregnating material, 8... Negative electrode active material. Name of agent: Patent attorney Toshio Nakao and 1 other person

Claims (1)

[Claims] The positive electrode includes a positive electrode whose core material is filled with an oxygen-activated catalyst, a separator, and a negative electrode zinc active material, and the positive electrode has a packing density of the catalyst with respect to the core material of 0.95-1.219/crl.
A button-type air battery.