JPH10116607A - Manufacture of battery positive electrode mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode mixture which can be measured with precision by a dry measure resulting from small particle diameters and small dispersion, and is excellent in a discharge characteristic even under a heavy load resulting from a high porosity. SOLUTION: A device is provided with a nearly cylindrical vessel 1 as pointing its center axis in a vertical direction, a disc 3 which is contained in the vessel 1 as pointing its center axis to be a rotation shaft in the vertical direction and is equipped with protruding stirring blades on its top face, and dry means which causes hot air to ventilate upward through a gap between the inside face of the vessel 1 and the side face of the disc 3 from under the disc 3. Using the device, as rotating the disc 3, and causing the hot air to ventilate upward through the gap between the side face of the disc 3 and the inside face of the vessel 1, powder-like positive electrode active material is thrown onto the disc 3, and simultaneously liquid binder is sprayed on the disc 3 so that the powder- like positive electrode active material and the binder are stirred and kneaded. The same is further granulated into spherical.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a positive electrode mixture for a battery.

[0002]

2. Description of the Related Art Conventionally, a granular positive electrode mixture is granulated by batch-type stirring granulation in which a mixture containing an active material, a binder, and a conductive material at a predetermined mixing ratio is stirred and kneaded by a stirring blade. Had been made. The positive electrode is produced by drying the positive electrode mixture thus obtained, measuring the mixture by so-called square cutting, and then press-molding the mixture into pellets. After the positive electrode mixture is filled into a predetermined volume of the cell, the partition bar is moved along the upper edge of the cell, thereby leveling the upper surface of the filled positive electrode mixture and removing excess positive electrode mixture. It is to be removed. In recent years, the use of batteries for small devices such as electronic desk calculators and wristwatches has increased, and there has been a demand for smaller and thinner batteries. For this reason, the amount of the positive electrode mixture used per battery is extremely reduced, and it is necessary to reduce the variation in the amount of the positive electrode mixture between the individual batteries. Further, a positive electrode mixture having high reaction efficiency and excellent discharge characteristics even under a high load has been demanded.

In order to meet these demands, it is required that the particle size of the granulated positive electrode mixture be 40 to 500 μm. When the particle size is smaller than 40 μm, the dispersion of the measured values at the time of cutting is increased due to aggregation. On the other hand, when the particle size is larger than 500 μm, the specific surface area becomes smaller, and the high-load discharge characteristics of a battery manufactured using the same become lower. Therefore, by lowering the porosity of the grains,
It is required to increase the specific surface area. However, the granulated product of the positive electrode mixture obtained by the batch type stirring granulation described above had a large particle size and a low porosity. Furthermore, since the dispersion of the particle diameter is large within the same lot or between lots, when this is weighed by square cutting, the dispersion of the weight is large.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a positive electrode mixture which can reduce the particle size of the granulated product of the positive electrode mixture, reduce the dispersion, and measure accurately by dividing. . Another object of the present invention is to provide a positive electrode mixture having a high porosity and excellent discharge characteristics even under a high load.

[0005]

In order to solve the above problems, the present invention provides a binder containing a powdery positive electrode mixture and a binder on the upper surface of a rotating disk having a stirring blade. Supply,
These are instantaneously and uniformly kneaded with a disk to produce a positive electrode mixture granulated product. The disk is disposed in a sealed container with the central axis serving as the rotation axis directed vertically, and the dry hot air flows upward through the gap between the side surface of the disk and the outer surface of the container. The powdered positive electrode mixture and binder supplied on the rotating disk are agitated by a stirrer blade and hot air, granulated into a sphere, can be accurately measured by cutting, and have discharge characteristics even under high load discharge. It is possible to obtain a positive electrode mixture granulated product having an excellent particle size of 40 to 500 μm and a high porosity in a short time.

According to this method, it is possible to obtain a granulated product having a smaller particle size and less variation as compared with a case of granulating by a conventional batch type stirring granulator, which is particularly desirable as a positive electrode mixture for a battery. Granules within the particle size range of 40 to 500 µm can be obtained instantaneously with good yield. In addition, the obtained positive electrode mixture is stirred and mixed instantaneously as compared with that obtained by a batch type stirring and mixing type granulator, and thus a soft and high porosity granulated product is obtained. As a result, a battery having excellent liquid absorbing properties of the electrolytic solution and excellent discharge performance even under high load discharge can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a positive electrode mixture for a battery according to the present invention comprises the steps of: forming a substantially cylindrical container having a central axis oriented vertically; A disk having a stirring blade protruding from the upper surface and a drying means for flowing hot air upward from the lower side of the disk to the gap between the inner surface of the container and the side surface of the disk. Using, while rotating the disk, and flowing hot air upwards into the gap between the side of the disk and the outer surface of the container, put the powdered positive electrode active material on the disk, at the same time on the disk By spraying a liquid binder, the powdery positive electrode active material and the binder are stirred and kneaded, and a step of granulating into a spherical shape is included. Further, it is preferable that the active material is at least one selected from the group consisting of metal oxides, sulfides, halides, and carbon halides.

[0008]

An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a granulating apparatus used in this embodiment. The substantially cylindrical container 1 is made of stainless steel, and is arranged with its axial direction oriented vertically. Inside the container 1, a stainless steel disk 3 is arranged with its central axis coinciding with the central axis of the container 1. Disk 3 has a diameter of 300 mm and a height of 50 mm
Then, it is rotated by a motor (not shown) connected below. A triangular pyramid-shaped stirring blade 4 made of stainless steel and having a height of 40 mm is attached to the upper surface of the disk 3 in four directions equally dividing the upper surface from the center. A supply port 5 from a raw material supply device 10 and a spray nozzle 2 from a tank 7 are arranged at an upper portion of the container 1.

Using this granulator, a positive electrode mixture was prepared as follows. A mixed powder obtained by mixing 5 kg of manganese dioxide and 300 g of expanded graphite was put into the mixture feeder 10, and the mixed powder was continuously supplied from the supply port 5 to the upper surface of the disk 3 rotating at 5000 rpm. Also, an aqueous dispersion of polytetrafluoroethylene as a binder is charged into the tank 7, and at the same time as the mixed powder is supplied, 1 part by weight of polytetrafluoroethylene is added to 100 parts by weight of manganese dioxide. From the spray nozzle 2 continuously on the upper surface of the disk 3.

The supplied mixture and the binder are uniformly stirred by a stirring blade 4 arranged on the upper surface of the rotating disk 3.
Kneaded. The mixture to which the centrifugal force is applied by the rotation of the disc 3 is thrown toward the inner wall of the container 1, and the dried 120 ° C. sent from the hot air generator 11 is passed through the gap between the container 1 and the disc 3. Hot air is blowing up continuously,
The mixture is blown up with the airflow without falling down through this gap. When it falls on the disc 3 again, it is stirred again. Thus, the mixed powder and the binder are uniformly mixed and granulated into a sphere. The fine particles dispersed in the airflow are sucked and removed by the bag filter 12. The positive electrode mixture thus granulated was taken out from the outlet 13. The obtained positive electrode mixture was weighed so as to be 450 mg by sectioning. Then, this was press-molded into a pellet at a pressure of ² to 4 ton / cm ² and dried again at 250 ° C. with hot air to obtain a positive electrode pellet.

Comparative Example As a comparative example, an aqueous dispersion of manganese dioxide, expanded graphite and polytetrafluoroethylene was prepared using manganese dioxide in the same manner as in the above-mentioned example, using a batch-type stirring mixer as a conventional production method. 1 by weight of expanded graphite and polytetrafluoroethylene
The mixture obtained at a ratio of 00: 6: 1 was mixed for 15 minutes, and the mixture was dried at 150 ° C. for 16 hours to obtain a positive electrode mixture. The obtained positive electrode mixture was cut into 450
Weighed to give mg. Then add 2-4 tons /
Pressure molding into pellets at a pressure of ² cm ²
And dried with hot air to obtain a positive electrode pellet.

With respect to the positive electrode mixtures of Examples and Comparative Examples,
Each of the above-mentioned square-cut weighings was performed 10,000 times, and these were weighed to check the dispersion of the measured values. Table 1 shows the results.

[0013]

[Table 1]

As is clear from Table 1, the positive electrode mixture produced by the method of the present invention has a small variation in the measured value by the square cutting method.

Next, as shown in FIG. 2, each of the positive electrode mixtures of Examples and Comparative Examples was used, as shown in FIG.
A coin-type lithium battery of 6 mm was produced. Inside the stainless steel battery case 20 also serving as a positive electrode terminal, a positive electrode pellet 25 is disposed in close contact with the battery case 20. A separator 24 made of a polypropylene nonwoven fabric impregnated with a non-aqueous electrolyte is disposed on the positive electrode pellet 25. The opening of the battery case 20 is sealed by a stainless steel sealing plate 21 also serving as a negative electrode terminal, and the negative electrode active material 22 made of metallic lithium bonded to the inside of the sealing plate 21 is press-bonded to a separator 24. I have. A gasket 23 made of polypropylene having a surface coated with a sealant 26 is sandwiched between the battery case 20 and the sealing plate 21,
The battery is sealed by caulking the opening end of the battery case 20 inward.

The coin-type batteries using the positive electrode mixtures of Examples and Comparative Examples were subjected to continuous discharge (high-load discharge) at a temperature of 20 ° C. with a load of 1 kΩ as a load. The result is shown in FIG. At an ambient temperature of 20 ° C., 40
Discharge was performed for 15 seconds using a load of 0Ω as a load, and a voltage change (closed circuit voltage characteristic) due to the load was examined. FIG. 4 shows the results.

From FIG. 3, it is confirmed that the battery of the example has a higher battery voltage at the time of high-load discharge and a higher discharge capacity than the battery of the comparative example. As shown in FIG. 4, the battery of the example has a smaller closed-circuit voltage characteristic than the battery of the comparative example. This is considered to be due to the fact that, in the batteries of Examples, the porosity of the positive electrode mixture was high, so that the reaction of the active material inside the positive electrode proceeded more easily than in the conventional battery of Comparative Example.

The positive electrode mixture granules obtained by this production method have a small variation in particle size, and can be accurately measured. In addition, since the battery is soft, porous and has a large specific surface area, a battery having excellent discharge characteristics can be obtained even under high load discharge.

In the above embodiment, manganese dioxide was used as an example of the main active material of the positive electrode mixture, and an organic electrolyte battery using the same was described. However, copper oxide and silver chromate were used in the same manner as manganese dioxide. The same applies to the case where a metal oxide such as, or a carbon halide such as fluorocarbon is used as a main active material. In addition to the organic electrolyte battery, a battery of this type can be sufficiently applied to an alkaline battery and a Lucranche battery as well as an organic electrolyte battery.

[0020]

According to the present invention, it is possible to provide a porous positive electrode mixture having a small variation in measured values obtained by the square cutting method and having excellent liquid absorbing properties. Therefore, by using this, it is possible to provide a battery with small variation among individuals and excellent discharge characteristics.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a granulator used in an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a coin-type lithium battery using the positive electrode mixture of the embodiment.

FIG. 3 is a characteristic diagram showing battery voltage characteristics when the battery and the battery of the comparative example are continuously discharged under a high load.

FIG. 4 is a characteristic diagram showing closed circuit voltage characteristics of the battery and a battery of a comparative example. DESCRIPTION OF SYMBOLS 1 Container 2 Spray nozzle 3 Disk 4 Stirrer blade 5 Supply port 7 Tank 10 Raw material supply device 11 Hot air generator 12 Bag filter 13 Discharge port 20 Battery case 21 Sealing plate 22 Negative active material 23 Gasket 24 Separator 25 Positive electrode pellet 26 Sealant layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fumio Oo 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A substantially cylindrical container having a central axis oriented vertically and a circle having a stirring blade protruding from an upper surface and housed inside the container with a central axis serving as a rotation axis oriented vertically. Plate, from below the disk, using a device equipped with a drying means for flowing hot air upward to the gap between the inner surface of the container and the side surface of the disk, rotate the disk, and The powdery positive electrode active material and the conductive material are charged onto the disk while flowing hot air upward through the gap between the side surface of the disk and the outer surface of the container, and at the same time, liquid binding is performed on the disk. A method for producing a positive electrode mixture for a battery, comprising a step of stirring and kneading the positive electrode active material, the conductive material and the binder by spraying an agent, and granulating the mixture into a spherical shape. 2. The method according to claim 1, wherein the active material is at least one selected from the group consisting of metal oxides, sulfides, halides and carbon halides.