JPS59167968A - Silver oxide cell - Google Patents

Abstract

PURPOSE:To eliminate problem of increasing internal resistance after long term storage, by forming carbon porous film between silver layer formed on the surface of positive pole mainly composed of bivalent silver oxide and positive pole ring. CONSTITUTION:The bottom face of positive pole agent mold 1 mainly composed of bivalent silver oxide powder is applied with macromolecular organic solution to form a macromolecular film 2 then immersed in reductive solution to reduce silver oxide on the exposed surface of mold thus to form carbon porous film 4 at the portion where reduced silver 3 and positive pole ring 6 will contact. Said positive pole agent 1 is pressure molded together with positive pole ring 6 into positive pole case 5 to produce a positive pole assembly. Consequently if reduced silver 3 and bivalent silver oxide in positive pole agent 1 react during long term storage to convert highly conductive silver into insulative univalent silver oxide, porous film 4 of highly conductive carbon will maintain conductive state resulting in a silver oxide cell having low internal resistance even after long term storage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a button-shaped silver oxide battery using a positive electrode mainly composed of divalent silver oxide powder.

Button-shaped silver oxide batteries using electrode active materials are already known, and many proposals have been made for batteries using zinc as the negative electrode. Normally, when this divalent silver oxide powder is used as a positive electrode, the potential of divalent silver oxide (1, sV) is initially shown as the discharge potential, and then the potential (1, sV) of monovalent silver oxide (Aq20) is shown as the discharge potential.
5V) and a two-stage discharge potential, making it unsuitable as a power source for watches, etc. Therefore, in order to solve the above problem, the following method has been proposed. That is, a polymer coating is formed as an insulating layer on the bottom of a molded body made by mixing a divalent silver oxide active material and a forming aid, and the side and top surfaces are reduced with a reducing solution to form a silver layer, which is then used as a positive electrode. This method involves crimping the ring together with the positive electrode case. The above-mentioned silver layer is for the purpose of increasing the discharge potential to one level, and the interface between the silver layer and divalent silver oxide reacts to generate monovalent silver oxide, and this monovalent silver oxide is initially discharged and silver is generated. That's sweet, this silver reacts with divalent silver oxide and becomes 1
Silver oxide is produced, and by repeating this process,
One stage of discharge becomes possible.

However, when using the above method, when assembled into a battery and stored for a long period of time, the silver layer reduced by the reducing solution gradually reacts with divalent silver oxide to become monovalent silver oxide. . Silver is a good electrical conductor (specific resistance; 1.6
X10-8Ω·m) becomes monovalent silver oxide (specific resistance: 108Q□m), which is close to an insulator. Current collection to the positive electrode ring becomes insufficient, and the internal resistance of the battery increases. For this reason,
The voltage at the beginning of discharge becomes low, causing problems such as inoperability when used as a power source for watches, etc.

OBJECTS OF THE INVENTION The present invention aims to solve the problem of increase in internal resistance that occurs when stored for a long period of time as described above.

Structure of the Invention The present invention is characterized in that a porous carbon film is formed between the silver layer formed on the surface of the positive electrode and the positive electrode ring as described above.

The battery of the present invention can be made, for example, as follows. That is, a polymeric organic solvent solution is applied to the bottom of a positive electrode mixture molded body containing divalent silver oxide powder as the main ingredient, dried to form a polymer film, and then immersed in a reducing solution to expose the molded body. Silver oxide on the surface is reduced to silver, and a porous carbon film is formed in the area where the reduced silver and the positive electrode ring come into contact. This positive electrode mixture is compression molded into a positive electrode case together with a positive electrode ring to form a positive electrode assembly.

According to the present invention, it is possible to provide a silver oxide battery with low internal resistance even during long-term storage.

Description of Examples A positive electrode mixture prepared by mixing 90 parts by weight of divalent silver oxide powder, 8 parts by weight of monovalent silver oxide powder, and 2 parts by weight of polytetrafluoroethylene powder as a molding aid was first compression molded. Make a beret 1 as shown in Figure a. A 10% by weight solution of polyvinyl chloride in tetrahydrofuran is applied to one side of the pellet 1 and dried to form a polyvinyl chloride coating 2 as shown in FIG. Next, after being immersed in a double layered methanol solution of hydrazine for 10 minutes, it is dried, and as shown in FIG. reduce to

Next, as shown in Fig. 1d, carbon paint (Bunny Height IV96 manufactured by Nippon Graphite Industries Co., Ltd.) was applied around the upper surface of the silver layer 3 and on the side surfaces to form a porous layer with a coating amount of 5 mg of carbon after drying. A coating 4 was formed, the product was inserted into a positive electrode case 5, a positive electrode ring 6 was inserted into the upper part, and compression molding was carried out to obtain the structure shown in FIG. 1e. This positive electrode assembly is designated as A.

As a comparative example, a polyvinyl chloride film 2 was formed on the bottom surface of a pellet 1 similar to the above as shown in Figure 2a, and a 10% polyvinyl chloride coating 2 was formed in a methanol solution by weight of hydrazine.
After being immersed for a minute, it was dried to form a reduced silver layer 3, resulting in the structure shown in FIG. 2C. This was inserted into the positive electrode case 5, the positive electrode ring 6 was inserted into the upper part, and compression molding was performed to obtain the structure shown in FIG. 2d. This positive electrode assembly is designated as B.

Next, using each of the above positive electrode assemblies A and B, a diameter of 9.6 mm was prepared.
, button type batteries a and b having a thickness of 2+nnl were constructed.

FIG. 3 shows battery a. 7 is a mixture of frozen zinc powder and carboxymethylcellulose at a ratio of 2 parts by weight, which is filled into a sealing plate 8, and an electrolytic IQTr solution in which 5 parts by weight of zinc oxide is dissolved in an 8 mol/l aqueous solution of sodium hydroxide+. This is a negative electrode constructed by injecting liquid. 9 is a separator made of porous polyethylene film, 10 is an impregnated material made of nylon nonwoven fabric,
11 is a gasket. Note that 5 μl of the same electrolytic solution as above was injected into the positive electrode. This battery is designated as a, and a battery constructed in the same manner using positive electrode assembly B is designated as b.

These batteries were subjected to storage tests. Generally, 60 for one year at room temperature
If stored at ℃ for 20 days, it will remain at room temperature for 2 years at 60℃.
It is said to be equivalent to storage at ℃ for 40 days. Therefore, in order to shorten the test period, the test was performed using the above method of storage at 60°C. The battery internal resistance thus measured is shown in the following table.

The above results are the results of storing 30 battery cans. From this result, battery a according to the present invention has almost no change in internal resistance even when stored at 60°C for 60 days (equivalent to storage at room temperature for 3 years), and battery a according to the conventional method shows almost no change when stored at 60°C. It can be seen that the internal resistance of the battery increases and varies greatly.

Next, the battery stored at 60° C. for 60 days was subjected to a low temperature test, which is one of the conditions under which it can be used as a power source for a watch. This involves lowering the temperature of the battery to -10°C and discharging 2KQ, which is a time-opening load. As a result of the above-mentioned low-temperature test, all batteries a exhibited a voltage of 1.25 V or more.

However, only two batteries showed 1.25V or more, while the others showed 1.25V or less. This voltage of 25V is the voltage necessary to operate the watch.

From the above test results, the battery of the present invention has a stable internal resistance even after long-term storage, and can be used as a power source for a watch. This is an effect of providing the carbon porous film 4 between the reduced silver 3 and the positive electrode ring 6. Conventionally, when stored for a long period of time, the reduced silver 3 and the divalent silver oxide of the positive electrode mixture 1 react, and the silver, which is a good conductor, changes to monovalent silver oxide, which is close to an insulator. This is because it is difficult for electrons to flow into the positive electrode ring 6. However, the battery of the present invention has a porous coating 4 of carbon, which is a good conductor, and can maintain a state in which electrons can easily flow even if the battery changes to monovalent silver oxide as in the conventional case.

Effects of the Invention As described above, the present invention provides a silver oxide battery that can maintain stable internal resistance even after long-term storage, satisfies low-temperature tests, and is suitable as a power source for watches.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the manufacturing process of the positive electrode part in an example of the present invention, FIG. 2 is a diagram showing the manufacturing process of the positive electrode part of a comparative example, and FIG. 3 is a cross-sectional view of the main parts of the battery according to the present invention. A side view is shown. DESCRIPTION OF SYMBOLS 1... Positive electrode mixture molded body, 2... Polymer coating, 3... Reduced silver, 4... Porous carbon coating, 5... ...Positive electrode case, 6...Positive electrode ring, 7...Negative electrode, 8...Negative electrode case, 9
...Separator, 10...Impregnating material, 11 Gasket 0 Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure/ Figure 2/

Claims (1)

[Claims] A polymer coating is formed on the bottom surface of a positive electrode mixture molded body mainly composed of divalent silver oxide powder, and a silver layer is formed on the side and top surfaces, and a porous carbon coating is placed between this silver layer and the positive electrode ring. A silver oxide battery characterized by the following features: