JPS61104563A - Silver oxide battery - Google Patents

Abstract

PURPOSE:To prevent any increase of the internal resistance of a silver oxide battery which might result from prolonged storage and inhibit voltage reductions occuring during high-rate electric discharge by using a conductive auxiliary agent prepared by mixing a silver oxide powder with flake silver particles and a graphite powder. CONSTITUTION:After 100pts.wt. of a silver oxide powder is combined with 3-5pts.wt. of flake silver particles of 0.1mum thickness and 5mum particle diameter and 0.5-1.5pts. wt. of a graphite powder, the thus prepared mixture is compressed and molded to make a pellet 1. Then the pellet 1 and a positive ring 3 are placed in a positive case 2 and then the thus formed body is compressed and molded to make a positive electrode. Next, after a negative mixture 4 prepared by mixing 100pts.wt. of an amalgamated zinc powder with 5pts.wt. of sodium polyacrylate is placed in a negative case 5, a liquid electrolyte prepared by dissolving 5wt% of zinc oxide in an aqueous sodium hydroxide solution is poured into the negative case 5. After that, a separator 6 consisting of a porous polyethylene film and a liquid-holding material consisting of a nonwoven nylon fabric are placed between the pellet 1 and the negative mixture 4, thereby assembling a silver oxide battery. As the internal resistance of this battery does not increase even when it is stored for a long period, the battery can be suitably used as a power source for a watch or a similar device.

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 active material containing silver oxide as a main ingredient.

Conventional Structure and Problems Conventionally, button-shaped silver oxide batteries using a positive electrode active material containing silver oxide as a main ingredient have been commercialized, but batteries using zinc as a negative electrode have been commercialized. This positive electrode body uses a mixture of silver oxide powder and silver powder as a conductive agent. This is obtained by mixing spherical silver powder with a weight ratio of about 7, and compression molding the mixture. Also,
In recent years, there has been a demand for button-shaped silver oxide batteries to have higher electrical capacity as equipment that uses them as a power source become smaller and thinner.

As one measure for increasing the electric capacity, the present inventors have previously proposed the use of a positive electrode body that is compression-molded by mixing silver oxide powder with flaky silver powder. If this method is adopted, the electric capacity can be increased by 1.15 times compared to the former method. However, the problem with batteries using this positive electrode body is that the internal resistance of the battery increases when stored for a long period of time. This is because when the above-mentioned stored battery is discharged, the voltage drop becomes significant, especially when high rate discharge is performed.

OBJECTS OF THE INVENTION The purpose of the present invention is to improve conduction aids to prevent increases in battery internal resistance due to long-term storage and to eliminate voltage drop during high rate discharge.

Structure of the Invention The present invention is a mixture of silver oxide powder, flaky silver powder and graphite powder, and preferably 3 pieces of flaky silver powder.
~5% by weight, graphite powder 'io, and 5~1.6% by weight. By doing so, the conductivity between the silver oxide powders can be maintained even after long-term storage, and the internal resistance of the battery can be stabilized.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail. - Silver oxide powder, 3 parts by weight of flaky silver powder with a thickness of 0.1 μm and a particle size of 571 m, and 0.3% by weight of graphite powder were completely mixed and compression molded at 2 tons, as shown in the figure. Pellets 1 are made, and this is inserted into the positive electrode case 2 together with the positive electrode ring 3, and the positive electrode body is made by compression molding using 3 tons.Next, a negative electrode mixture is prepared by mixing 5 parts by weight of sodium polyacrylate with frozen zinc powder. Fill agent 4 into negative electrode case 6 and hydroxylate)
An electrolytic solution in which 5% by weight of zinc oxide F is dissolved in an 8 mol/L aqueous solution of IJ is injected, and a separator 6 made of a porous polyethylene film and an impregnated material 7 made of a nylon nonwoven fabric are inserted to assemble the battery. Ta. 8 is a gasket made of nylon. This battery (referred to as IL-a) is then mixed with silver oxide by 3 parts by weight of flaky silver powder and 0.6 parts by weight of graphite powder, compression molded, and assembled in the same manner as in 2. A battery prepared by mixing 3% by weight of flaky silver powder and 1% by weight of graphite is designated as B. A battery assembled in the same manner by mixing 3% by weight of flaky silver powder and 1% by weight of graphite is designated as C.
．． A battery assembled by mixing 5 parts by weight was designated as f: d, and a battery assembled by mixing 3 parts by weight of flaky silver powder and 1 part by weight of graphite was designated as e. Next, as a comparative example, a battery IF was prepared by mixing only 3 parts by weight of the flaky silver powder with silver oxide powder and forming a wire, and assembled in the same manner as above. Each battery a at this time
-f had a diameter of 9.6 μm and a thickness of 2 m. Note that, as the graphite used here, phosphorous graphite powder having an average particle diameter of 6 μm was used.

These batteries a-f were subjected to storage tests. Generally, one year of storage at room temperature is equivalent to storage for 60"020 days.
Two years at room temperature is equivalent to storage at 60"C for 40 days. Therefore, in order to shorten the test period, an accelerated storage test at 60"C was conducted. The internal resistance of the battery thus measured is shown in Table 1.

(Hereinafter referred to as Gold White) 6 Vane 6 From the above results, flaky silver powder 3 weight ratio and graphite powder 0
．． Battery a, which is a mixture of 3 weight cells, and battery f, which is a conventional product, are 6
The internal resistance after storage at 0″C has increased, but batteries b to e
There was almost no increase.

The reason for the increase in internal resistance is that silver oxide dissolves in the electrolytic solution and becomes silver oxide ions during storage, and these silver oxide ions adhere to the separator 6 and cause clogging. However, in batteries b to e containing 0.5% by weight or more of graphite i, the diffusion of silver acid ions is stopped by 1511, so that no increase in internal resistance occurs.

Next, each battery was stored at -10°C after storage for 60"080 days, and a 55elQ discharge test was conducted by connecting a 1.6Ω load resistor. Shown in the table.

Completion Be-7 From the above results, the conventional battery f that does not contain graphite and the graphite i0
．． For the 3 weight ratio mixed high humidity battery a, the voltage was 1.20V or less. This is less than the voltage required to drive a watch or the like. On the other hand, batteries b to e in which 0.5 weight percent or more of graphite was mixed maintained a voltage of 1.20 V or more.

Next, when the filling electric capacity of the positive electrode body of each of the above-mentioned batteries was compared, the values shown in Table 3 were obtained.

Table 3 From the above results, it can be seen that as the amount of graphite is increased by 1 or more, the filling capacitance decreases. Unfortunately, the currently used cathode body made by moistening 7 weights of spherical silver powder has a capacity of 58 mAh, and in order not to reduce the capacity compared to the current cathode body, the amount of graphite added must be less than 1.5 weight factor. There is. The internal resistance due to storage can be completely suppressed by 10 W by mixing 3 weights of crushed silver flake powder, but even if a large amount is mixed, a significant reduction in internal resistance cannot be expected, and on the contrary, the amount of silver oxide powder decreases. Since this results in a decrease in capacity and an increase in cost, the practical upper limit for the mixing amount is considered to be 5 parts by weight.

From the above, it can be seen that batteries S, C, and D, in which 3 to 6 parts by weight of flaky silver powder and 0.5 to 1.5 parts by weight of graphite powder are mixed with silver oxide powder, are stable even after long-term storage. There is no increase in internal resistance, the high rate discharge characteristics are good, and the decrease in capacity can be minimized.

Effects of the Invention As described above, according to the present invention, there is no increase in internal resistance even after long-term storage, and it is possible to provide a battery with characteristics comparable to those at the time of assembly, making it possible to provide a silver oxide battery suitable as a power source for watches, etc. can get.

[Brief explanation of drawings]

The figure shows a cross-sectional view of a button-shaped silver oxide battery according to the invention. 1...Positive electrode pellet, 2...Positive electrode case, 3...Positive electrode ring, 4...Negative electrode mixture, 5...Negative electrode case , 6... separator, 7... including FF [, a... ga 9
Base 7 skates.

Claims (1)

[Claims] 3-5% by weight of flaky silver powder, 0.5% of graphite powder
A silver oxide battery using silver oxide powder mixed with ~1.5% by weight as a positive electrode active material.