JPS6324304B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an anode mixture for alkaline batteries, in which a dry mixed mixture powder of manganese dioxide and conductive material such as graphite is fluidized and stirred using hot air, and polystyrene (hereinafter referred to as PS) or polystyrene (hereinafter referred to as PS) or By dissolving polyvinyl chloride (hereinafter referred to as PVC) in tetrahydrofuran (hereinafter referred to as THF) in a weight ratio of 0.2 to 3 parts per 100 parts of the mixture powder and spraying it, then drying with hot air at a temperature of 45 to 66°C. The purpose is to create a granular anode mixture with improved fluidity and moldability into pellets, etc. In recent years, electronic devices such as electronic watches, cameras, and calculators that are powered by button-type silver oxide batteries, mercury batteries, and alkaline manganese batteries have come into widespread use. Accordingly, there is a strong demand for thinner batteries. Particularly noteworthy is the demand for alkaline manganese batteries that use manganese dioxide, which is a cheap anode material, and there is a strong desire for alkaline manganese batteries that are compatible with silver oxide batteries and mercury batteries. However, with this type of alkaline manganese battery,
Due to weighing errors during weighing and molding of the anode mixture and the large size ratio of the anode mixture pellet (pellet thickness to pellet outer diameter), pellet cracking and cracking occur, which is an important problem in battery manufacturing. I was getting used to it. A typical example of the conventional manufacturing method for anode mixture is (a)
Either manganese dioxide and graphite are mixed, pressure-molded, coarsely crushed and passed through a sieve to obtain granules of a specified particle size, or (b) a mixture of manganese dioxide and graphite is mixed with carboxymethyl cellulose, polyacrylic After adding a binder such as an acid salt and an alkaline electrolyte and stirring, this is sprayed into a high temperature atmosphere.
There are methods of drying and sieving. However (a)
In this method, considering the fluidity and moldability of the mixture powder, the yield of the mixture with the desired particle size is low, and the obtained granular powder is easily disintegrated. Particles are finely pulverized in the hopper of a molding machine, and the state of the powder tends to be uneven when it is filled into a mold. Furthermore, variations in the filling amount tend to occur,
There is also large variation in the performance of batteries that have become products. In method (b), manganese dioxide is introduced into a high temperature atmosphere during the drying process after mixing and stirring to form a mixture, and manganese dioxide is exposed to high temperatures (150°C or higher), resulting in deterioration of the battery voltage and discharge performance. It was giving bad results. In addition, it is extremely difficult to narrow the particle size range of granular powder, and the particle shape is amorphous.
There was a problem with the fluidity of the mixture in the molding machine. Furthermore, in both methods (a) and (b), the conductive agent is not completely mixed uniformly, so some mass-produced batteries may contain less conductive agent than the specified mixing ratio, and the amount filled within the same volume may vary. This caused internal resistance defects. The present invention improves the above-mentioned conventional drawbacks by using PS or PVC dissolved in THF as a binder. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 1 kg of mixed powder of manganese dioxide and graphite was first
The mixture 3 is placed in the fluidized granulator 1 shown in the figure, and hot air 2 at 50°C is blown upward from the bottom of the fluidized drying tower of this granulator at a flow rate of 2 m ³ /min to fluidize the mixture 3. THF solution 500ml containing 20g of PS while stirring
g at nozzle 4 with a flow rate of 20 g/min and a pressure of 1.0 Kg/cm ^2.
It was supplied by spraying. After the spraying was completed, hot air at 50° C. was sent to dry it for 5 to 10 minutes to obtain a granular anode mixture. In the figure, 5 is an exhaust filter, and 6 is a filter cloth for preventing the mixture 3 and the granular mixture from falling off. Example 2 20g for 1kg of mixed powder of manganese dioxide and graphite
500 g of THF in which PVC was dissolved was sprayed and supplied under the same conditions as in Example 1 to obtain a granular anode mixture. The anode mixtures according to Examples 1 and 2 were molded using a commercially available pellet molding machine that weighs using the square cutting method. Table 1 shows the standard deviation values of the weights of each 100 pellets. However, in this case, the standard value of pellet weight is 100
mg.

[Table] As is clear from Table 1, the anode mixture according to the present invention can achieve about twice the improvement in weight accuracy compared to the conventional one. This is because the granular anode mixture of the present invention is moderately larger than the conventional anode mixture and has a narrow particle size range, as shown in Figure 2.
This is because the particle shape becomes close to spherical due to the collision between the fluidized column wall and the particles during fluidized granulation, which improves the fluidity of the mixture powder. This is extremely important in battery manufacturing. In addition, when obtaining a granular anode mixture, the temperature during hot air drying is also important;
If it is lower than ℃, THF will not dry properly.
The granulated particles are wet and heavy, and have irregular particle sizes. On the other hand, if the drying temperature is higher than 66° C., THF evaporates quickly, so adhesion between manganese dioxide and graphite and growth of secondary particles are not successful, resulting in a wide particle size distribution. Therefore, the boiling point of THF used as a binder solvent is 66
℃, and considering its vapor pressure, a suitable drying temperature for the anode mixture is 45 to 66°C, and within this temperature range, the problem of voltage deterioration due to the thermal influence of manganese dioxide can be solved. Also PS or
If the amount of PVC added is less than 0.2 parts by weight per 100 parts by weight of the anode mixture, the binder effect will not appear and pellets cannot be formed well. Also 3.0
When the amount is larger than the weight part, the physical properties of PS and PVC, such as hydrophobicity and non-conductivity, appear, and the electron conduction network necessary for the battery anode is inhibited, resulting in high electrical resistance.
Moreover, the mixture becomes difficult to wet with the electrolytic solution, and the effect on battery performance is not sufficient. is a binding agent
When PS and PVC are stored in a strong alkali, they are oxidized by depolarizing agents such as manganese dioxide, and the chain molecules do not break and the holding power of the anode mixture becomes insufficient, and the depolarizing ability is maintained. It also does not cause a decrease in FIG. 3 shows a half-sectional view of a button-type alkaline manganese battery formed using the granular anode mixture obtained in the example of the present invention described above. 7 in the figure is an anode formed from a granular anode mixture using PS or PVC as a binder according to the present invention;
Reference numeral 8 denotes a gel cathode, which is generally made of zinc chloride powder mixed with a sizing agent that swells with an electrolytic solution, such as a sodium salt of carboxymethyl cellulose, as a thickener. 9 is a separator mainly made of a cellulose-based substance; 10 is a liquid-containing material made of a cellulose-based substance;
11 is a nickel-plated iron anode case, 12
1 is a nylon gasket, and 13 is a sealing plate that also serves as a cathode terminal. LR1120 button-type alkaline manganese battery made with this configuration (diameter 11.6 mm, thickness 2.0 mm)
Table 2 shows the initial performance and discharge performance of 100 units. These characteristics are equivalent to batteries using conventional anode mixtures, and there is no problem in terms of battery performance even if the mixture is granulated using PS or PVC as a binder.In fact, the variation in discharge capacity is small. It's summery.

[Table] As mentioned above, in addition to the characteristics of the granular anode mixture, in the method of the present invention, the preparation of the anode mixture and the granulation into granules are performed in the same process, and the desired particle size can be obtained. The sieving process can be omitted, resulting in an excellent manufacturing process in terms of manufacturing costs and man-hours.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a fluidized granulator used in the examples of the present invention, Figure 2 is a diagram showing the particle size distribution of the granular anode mixture in the present invention, and Figure 3 is a diagram showing the particle size distribution of the granular anode mixture obtained by the present invention. 1 is a half-sectional view of an alkaline manganese battery using a granular anode mixture. 3...Mixture powder of manganese dioxide and graphite, 7
……anode.

Claims (1)

[Claims] 1 A binder in which polystyrene or polyvinyl chloride is dissolved in tetrahydrofuran at a weight ratio of 0.2 to 3 parts per 100 parts of the mixture powder while dry-mixing a mixture powder of manganese dioxide and conductive material while fluidizing and stirring it with hot air. A method for producing an anode mixture for an alkaline battery, comprising spraying and supplying a solution and then drying with hot air at a temperature of 45 to 66°C to obtain a granular anode mixture.