JPS58128663A - Silver oxide battery - Google Patents

Abstract

PURPOSE:To increase the battery performance of a silver oxide battery, in which zinc is used as a negative active material and silver oxide is used as a positive active material, by restricting the composition of electrolyte which is used for the battery and made of an aqueous solution which principally consists of sodium hydroxide and contains zinc oxide. CONSTITUTION:A small button-type silver-oxide battery is constituted by using zinc as a negative active material, silver oxide as a positive active material, and an aqueous solution which principally consists of sodium hydroxide and contains zinc oxide as an electrolyte. In such a battery, the electrolyte is restricted to contain 20-25wt% of sodium hydroxide, and zinc oxide in a concentration from 100% to 40% of its solubility. As a result, the increase of the internal resistance during the electric-discharge process can be suppressed, and the closed-circuit voltage characteristic of the battery is enhanced. Besides, a battery with excellent electric discharge and preservation performances can be obtained.

Description

Detailed Description of the Invention The present invention is a silver oxide battery that uses silver oxide as a positive electrode active material, zinc as a negative electrode active material, and a sodium hydroxide-based aqueous solution containing zinc oxide as an electrolyte. The purpose of this technology is to reduce or stabilize internal battery resistance during discharge and improve closed-circuit voltage characteristics by using an electrolyte with a limited composition in small batteries/batteries used in electronic devices. It is something to do.

In recent years, the spread of small electronic devices such as cameras, electronic wristwatches, and hearing aids has been remarkable. As a power source for these devices, especially electronic watches, voltage stability, storage characteristics,
Due to their excellent leakage resistance, many small button-type silver oxide batteries that use an alkaline electrolyte mainly composed of sodium hydroxide are in use.

Conventionally, as the electrolyte composition of this type of silver oxide battery, an aqueous solution containing sodium hydroxide at a weight ratio of 30 to 40 and zinc oxide dissolved to its saturated state has been used.

This was mainly to prevent the deterioration of the container during storage due to elution of the cathode zinc in the strongly alkaline electrolyte and to completely prevent the generation of hydrogen gas.However, with this electrolyte composition, the maximum heavy conductivity The composition is quite different from that of 18 wt% NaOH, which has a low electrical conductivity. This increases the internal resistance as a static characteristic of the battery, and at the same time has the drawback that the internal resistance of the mixed oil increases rapidly with the depth of discharge during the discharge process. The increase in internal resistance during this discharge process is a serious drawback in terms of closed circuit voltage characteristics when applied to small electronic devices such as watches.

The present invention focused on the above points and studied the electrolyte composition in detail, and found that it contains 20 to 25% by weight of IJium hydroxide and 40% of the saturated dissolved amount of zinc oxide. By using those in the area between the quantities,
It was possible to obtain a small button-type silver oxide battery with no problems in storage stability and excellent discharge and closing voltage characteristics.

The details will be explained below along with examples.

FIG. 1 is a diagram showing changes in battery internal resistance during discharge due to differences in NaOH concentration of the electrolyte. A in the figure is NaOH
It is a battery with a concentration of 20 cycles and 30% by weight of B,
Zinc oxide is dissolved in a sol amount corresponding to the saturated solubility amount. The test is 7.9 mm in diameter and 2.9 mm in total thickness. The test was carried out using a battery of size ○ with constant resistance continuous discharge of 30KQ.

As shown in the figure, the internal resistance at the start of discharge is approximately 1.6
However, in B, the internal resistance increases sharply with the depth of discharge, and at a depth of discharge of 80 inches, it is four times that of A, and 100
It exceeds Ω. For electronic watches, especially batteries that use an alkaline electrolyte containing sodium hydroxide as the main component,
If the white part resistance becomes 50Ω or more during discharge, the device's IC or LS
Since a malfunction occurs in I, it is necessary to suppress this increase to 60Q or less.

The following table shows the relationship between the NaOH concentration, the internal resistance of the battery, and the closed circuit voltage when zinc oxide is expressed as so% of the saturated dissolved amount. When NaOH is 30% by mass or more, the internal resistance becomes very high, and the closed circuit voltage is considerably lower than when the NaOH is 26% by mass or less.

Margin below However, the closed circuit voltage is the lowest voltage when discharging a 2Ω load for 6 seconds.

Moreover, this table is for the same test conditions as in the case of FIG.

Figure 2 shows the dissolved amount of zinc oxide at each NaOH concentration in the electrolytic solution, the internal resistance at a discharge depth of 80, and the internal resistance at 60
The figure shows the relationship between the capacity deterioration rate and the capacity deterioration rate when stored for 40 days at ℃. In the figure, A is the capacity deterioration rate when the HaOH concentration is 15% by weight, 20% by weight, C is 26% by weight, H is 16% by weight, 20% by weight, and G is 26% by weight. % by weight, CH indicates the internal resistance at 30% by weight. each N
a In terms of OH concentration, the internal resistance at a discharge depth of 80 degrees does not change significantly depending on the amount of zinc oxide, but in terms of capacity deterioration, for NaOH of 20% by weight or more, the zinc oxide reaches the saturated amount of 40%. Below that, it increases rapidly. In addition, in the case of 15% by weight HaOH, there was considerable capacity deterioration even if the zinc oxide content was from 40% to saturation.

From the results below, it is found that an alkaline aqueous solution whose composition is specified as an electrolyte with a sodium hydroxide concentration of 20 to 26 weight coefficients and a zinc oxide concentration of 40 to 100 weight coefficients of the saturated dissolution amount at each NaOH concentration is used. As a result, a small button-type silver oxide battery with excellent closed-circuit voltage characteristics and excellent discharge and storage properties can be obtained.

[Brief explanation of the drawing]

Figure 1 shows changes in battery internal resistance during discharge due to differences in sodium hydroxide concentration in the alkaline electrolyte, Figure 2
The figure shows the dissolved amount of zinc oxide at each sodium hydroxide concentration in the electrolyte, the internal resistance at a depth of discharge of 80, and the 6o
It is a figure which shows the relationship with the capacity deterioration rate after 40 days of storage at °C. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 figure

Claims (1)

[Claims] A battery in which zinc is used as a negative electrode active material, silver oxide is used as a positive electrode active material, and an aqueous solution containing zinc oxide and mainly consisting of sodium hydroxide is used as an electrolytic solution, wherein the electrolytic solution composition is 20 to 26 F-i of sodium hydroxide. % and its hydroxylation) IJ
A silver oxide battery characterized in that zinc oxide is regulated between a saturated dissolution amount and 40% of the saturated dissolution amount when the zinc oxide concentration is 1.