JPS5827624B2 - Collection and reuse method of anode active material for silver oxide batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering and reusing the anode active material of a discharged silver oxide battery.

Conventionally, silver oxide alone or a mixture of silver oxide and manganese dioxide has been used as the positive electrode active material for □ oxide batteries.

However, when silver oxide is used alone, the electromotive force drops sharply at the end of battery discharge, so it is not possible to predict so-called capacity exhaustion based on the decrease in battery output voltage.

For this reason, especially in silver oxide batteries used as power sources for recent electronic watches, a mixture of silver oxide and manganese dioxide is used as an anode active material in order to slow down the drop in electromotive force at the end of discharge. There is a growing tendency to do so.

Therefore, it has been considered to recover and reuse the expensive □ from silver oxide batteries, which are consumed in extremely large amounts. However, in the conventional recovery and reuse method, as shown on the right side of the flowchart in the figure, First, nitric acid is added and filtered to separate the graphite from the anode mixture containing finished metallic silver, lower manganese dioxide, and graphite, and sodium geode is added to the filtrate containing silver nitrate and manganese nitride to separate the silver nitrate from silver chloride. Replaced with 1
．． 5. Extract this with the precipitate and I~ [-1 After the purification and reduction process, recover only the expensive metallic silver and recover it (7) Reuse the recovered metallic silver with l-silver oxide and i~ was common.

1~ or I~, such conventional methods require a lot of time and money to separate metallic silver and lower manganese dioxide, are inefficient, and increase recovery costs, so the goal of resource conservation cannot be fully achieved. I couldn't do it.

Furthermore, it has been pointed out that when a mixture of silver oxide and manganese dioxide is used as an anode active material in a silver oxide battery, the state of the mixture causes large variations in the closed circuit voltage, especially during load.

The present invention was made in order to improve the drawbacks of slanting.
The purpose is to efficiently and economically recover the anode active material from discharged silver oxide batteries, and to provide an anode active material with excellent discharge capacity and closed circuit voltage with little variation.

That is, according to the method for recovering and reusing an anode active material for silver oxide batteries according to the present invention, a discharged anode mixture mainly composed of silver oxide and manganese dioxide is dissolved in nitric acid, and a filtration process is performed to produce Kuroori, etc. The conductive material is separated, a caustic powder solution is added to the PK to co-precipitate silver and manganese oxides, and after drying, a conductive agent is mixed into the co-precipitate.

According to a preferred embodiment, 100 kg of a discharged anode mixture mainly composed of silver oxide and manganese dioxide is dissolved in nitric acid, conductive agents such as graphite are separated by a filtration process, and about 20 kg of the discharged anode mixture is dissolved in this furnace liquid. ~25 wt % caustic soda solution 2501 is added and reacted with stirring to coprecipitate silver and manganese oxides, and the coprecipitate is filtered and washed and then dried at about 100'C.

Next, graphite is added as a conductive agent to the co-precipitated oxide of silver and manganese obtained in this way [-After thorough mixing, an anode mixture with a desired particle size is obtained through rolling granulation and knotting processes, and molded. It is pressed into a pellet and used as an anode for a silver oxide battery.

Next, an anode mixture formed into pellets using the coprecipitated oxide according to the above example was prepared using a 40 wt % caustic potassium aqueous solution as an electrolytic shield and granular zinc chloride as a cathode active material.
The method was applied to an IS G13 type battery, and the following battery characteristics were measured.

1. Measurement of closed circuit voltage under 100Ω load at 20°C and -10°C A battery using the coprecipitated oxide according to the present invention as an anode active material is A, a conventional anode active material mixed with silver oxide and manganese dioxide A battery using the substance is designated as B, and the measurement results are shown in Table 1.2.

Incidentally, in both A and B, the content ratios of silver oxide, manguin dioxide, and graphite as a conductive agent are the same.

Table 1. Closed circuit voltage with 100Ω load at 20℃
n-=100 Table 2. Closed circuit voltage at 1,000 load towards -40°CK
n-=100 As is clear from Tables 1 and 2, the average closed circuit voltage (X) of the silver oxide battery using the coprecipitated oxide according to the present invention as the anode active material is higher than that of the conventional one. , and its standard deviation was smaller than that of the conventional method, with less variation.

This is because the mixture of silver oxide and manganese dioxide obtained by coprecipitation has a higher packing density during pellet formation than the conventional mixture of silver oxide and manganese dioxide, which is a mechanical mixture of silver oxide and manganese dioxide. It is thought that this improves the contact condition between the two and reduces the internal resistance of the battery.

In addition, the standard deviation is smaller for the silver oxide and manganese dioxide mixture obtained by coprecipitation than for the conventional mixture.
This is thought to be because the mixing state is good and the dispersion of both substances is small.

As described above, when the coprecipitated oxide according to the present invention is used as a mixed anode material for a battery, the battery's performance is improved compared to when a mixture of separately prepared silver oxide and manganese dioxide is used. This made it possible to significantly improve the function and quality of the buttons.

■Measurement of discharge capacity under a 6.5 Ω load at 20°C Silver oxide battery A using the coprecipitated oxide according to the present invention and a conventional positive electrode active material made of a mixture of silver oxide and manganese dioxide Table 3 shows the discharge capacity of silver oxide battery B in continuous discharge at 6.5 Ω at 20°C.

Table 3. 6.5 Discharge capacity n=10 for Ω continuous discharge
0 As is clear from Table 3, the discharge capacity of Battery A using the coprecipitated oxide according to the present invention is about 5% better than Battery B using the conventional mixture.

This is also considered to be because the packing density of the coprecipitated oxide according to the present invention during molding is greater than that of the conventional one, and therefore the amount of anode active material packed per unit volume is increased.

By the way, S shown in Tables 1 to 3 above indicates the standard deviation commonly used in statistics, and its value was determined using the calculation method shown below.

That is, the sum of squares of the differences between each measured value (Xl, X2, . . .) and its average value (X) is called the deviation sum of squares or sum of squares and is expressed by S.

The standard value difference S is the square root of this deviation sum of squares S divided by the number of data n.

This standard deviation S represents the degree of variation in individual data; for example, if X1=X, s=0, which means that there is no variation at all.

First, the smaller the value of S, the smaller the variation.

Therefore, for example, to explain Table 1, there is a difference in the absolute value of can be said to be small.

The figure compares the process of recovery and reuse using the method according to the present invention and the process of recovery and reuse using the conventional method. According to the method of the invention, a battery with higher performance and higher quality than before can be obtained from a discharged anode with extremely fewer and simpler steps than conventional methods,
Therefore, the purpose of resource saving can be fully achieved.

As described above, the method for recovering and reusing the anode active material for silver oxide batteries according to the present invention is to dissolve the discharged anode mixture mainly composed of silver oxide and manganese dioxide in nitric acid, and then use conductive materials such as graphite through a filtration process. By separating the agent, adding caustic soda solution to the furnace liquid to coprecipitate silver and manganese oxides, and mixing the co-precipitate with a conductive agent after drying, anode activation can be performed from a discharged silver oxide battery. The material can be recovered efficiently and economically, and an anode active material having excellent discharge capacity and closed circuit voltage with little variation can be obtained, and therefore the purpose of resource saving can be fully achieved.

[Brief explanation of drawings]

The figure is a flowchart showing an embodiment of the method of the present invention in comparison with a conventional method.

Claims (1)

[Claims] 1 Dissolve the discharged anode mixture, which mainly consists of silver oxide and manganese dioxide, in nitric acid, separate the conductive agent such as black oxide through a filtration process, and add a caustic alkaline solution to the P solution to dissolve the oxides of silver and manganese. A method for recovering and reusing a positive electrode active material for a silver oxide battery, characterized by co-precipitating the and mixing the co-precipitate with a conductive agent after drying.