JP2003017044A - Method of manufacturing positive electrode for alkali battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a positive electrode for an alkali battery appropriate for the structure of a zinc-alkali battery having high rate discharging characteristics. SOLUTION: This method of manufacturing a positive electrode for a zinc- alkali battery has a process for agitating to mix the positive electrode composition components containing the nickel hydroxide group particles provided with a cobalt compound layer in a surface thereof, an alkali electrolyte and a binder, a process for classifying the particles obtained by compressing and crushing the agitated and mixed composition to obtain the granule, and a process for forming the granular mixture component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a positive electrode for an alkaline battery, and more particularly to a method for producing a high quality positive electrode for an alkaline battery.

[0002]

2. Description of the Related Art For example, zinc alkaline batteries are used as a power source for portable electronic devices such as portable radios and cassette recorders. In addition, this type of alkaline battery has a configuration in which the battery element (electromotive portion) has an inside-out structure or a configuration in which the battery element (electromotive portion) is a laminated plate. It is also known that the cost can be reduced when the battery element has an inside-out type structure.

That is, generally, a hollow cylindrical molded body made of a positive electrode mixture containing nickel hydroxide-based particles as a positive electrode active material and a conductive agent is used as a positive electrode, and a hollow cylinder having a bottom is formed in the hollow of the positive electrode. An inside-out type structure is adopted in which a separator is inserted and arranged, and a gelled negative electrode material containing zinc as a main component is filled in the bottomed tubular separator. Further, by adopting the inside-out type structure, productivity is improved compared to the case where a spiral type structure in which a laminate of a sheet-shaped positive electrode, a separator and a negative electrode is wound is adopted. It is possible to provide a high-capacity zinc alkaline battery at low cost.

By the way, this type of positive electrode for an alkaline battery is generally manufactured by the following procedure. That is, for 90 parts by mass of nickel hydroxide particles (positive electrode active material) having an average particle size of 5 to 15 μm, for example, 5 to 10 parts by mass of a conductive agent such as graphite powder, for example, 30 to 4 caustic potash.
2 to 5 parts by mass of an alkaline electrolyte composed of a 5% by mass aqueous solution,
And 0.01 to 1 part by mass of a binder such as CMC (carboxymethyl cellulose) are mixed by stirring. The positive electrode mixture mixture (composition) thus obtained is pressure-molded to produce a desired positive electrode, for example, a cylindrical positive electrode pellet. As the positive electrode active material, nickel hydroxide-based particles provided with a cobalt compound layer on the surface to impart conductivity may be used.

[0005]

As described above, when the battery element has the inside-out structure, the productivity and cost of the alkaline battery can be reduced as compared with the case where the battery element has the spiral structure. It is advantageous in terms. However, the inside-out structure has a problem that it is difficult to significantly increase the battery capacity because the facing area between the positive electrode and the negative electrode is smaller than that of the spiral structure and the internal volume of the battery is fixed.

As a means for increasing the capacity of the alkaline battery,
In the manufacturing process of the positive electrode, if the ratio of the positive electrode active material is extremely increased, it becomes difficult to form a uniform component system of the positive electrode mixture, and as a result, there is a risk of causing variations in the positive electrode capacity and the mass productivity of the positive electrode. And yield, or the reliability of the manufactured / manufactured battery is impaired. On the other hand, an increase in the ratio of the positive electrode active material in the positive electrode mixture, on the other hand, results in a lower utilization rate of the positive electrode active material, leading to deterioration in heavy load discharge characteristics and the like.

The main use of alkaline batteries is usually in the form of heavy load discharge, but in electronic devices using alkaline batteries as a power source, the driving load can be reduced by selecting the mode of use. A usage mode of load discharge may be adopted. It can be said that it is advantageous in terms of energy saving and resource saving if medium load discharge can be performed without causing a problem when such a driving load is reduced. That is, if an alkaline battery that has excellent heavy load discharge characteristics and excellent medium load discharge characteristics without increasing the active material appears, a highly versatile portable power supply can be provided.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a positive electrode for an alkaline battery, which is suitable for the structure of an alkaline battery having an excellent high rate discharge characteristic.

[0009]

According to the invention of claim 1, a step of stirring and mixing positive electrode composition components containing nickel hydroxide particles having a cobalt compound layer on the surface thereof, an alkaline electrolyte, and a binder, Manufacture of a positive electrode for an alkaline battery, which comprises a step of classifying particles obtained by subjecting a stirred and mixed composition to compression crushing treatment to obtain a granular mixed component, and a step of molding the granular mixed component Is the way.

The invention of claim 2 is characterized in that, in the method for producing a positive electrode for an alkaline battery according to claim 1, the mixed composition contains a carbon-based conductive agent.

A third aspect of the present invention is the method for producing a positive electrode for an alkaline battery according to the first or second aspect, characterized in that the particle size distribution of the granular positive electrode mixture is 14 to 60 mesh.

According to a fourth aspect of the present invention, in the method for producing the positive electrode for an alkaline battery according to any one of the first to third aspects, the cobalt compound layer has cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide and water. It is characterized by being formed of at least one of cobalt oxide and metallic cobalt.

The inventions of claims 1 to 4 are based on the following knowledge. That is, the present inventor, when stirring and mixing positive electrode composition components for alkaline batteries to form a molded body, the composition prepared by stirring, mixing, and subjecting to compression and crushing, and classifying the obtained particles, granules are obtained. When this is granulated and molded with this granulated composition component as a material,
It has been found that the manufacturing operation of the positive electrode is facilitated and the productivity is improved, while the filling rate and strength are increased to easily obtain a positive electrode having a high capacity and improved / improved load discharge characteristics. That is, it was confirmed that, in the production of a positive electrode for an alkaline battery, compression / crushing treatment, classification / granulation, and molding of this granule greatly affect the characteristics of the positive electrode and further the characteristics of the battery. It came to.

In the first to fourth aspects of the present invention, the nickel hydroxide-based material that mainly constitutes the positive electrode mixture is, for example, nickel hydroxide, nickel oxyhydroxide, or a nickel hydroxide-nickel oxyhydroxide mixed system (mixed system). Alternatively, they are a eutectic of zinc and cobalt. And as these nickel hydroxide type | system | group particles, generally, an average particle diameter is 5 to 1
The one having a thickness of about 5 μm is used.

In the invention of claims 1 to 4, the cobalt compound layer provided on the surface of the nickel hydroxide particles forming the positive electrode active material is, for example, cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, or hydroxide. At least one selected from cobalt and metallic cobalt.
Here, the cobalt compound layer is preferably provided with a substantially uniform film thickness as a whole, but it may be provided partially.

If necessary, the conductive agent to be added and compounded is, for example, natural graphite, synthetic graphite, carbon black particles such as Ketjen black and acetylene black.
The amount of the conductive agent in the positive electrode mixture is about 3 to 15% by mass, preferably 5 to 12% by mass, more preferably 7% by mass.
It is selected within the range of 10 to 10% by mass. Here, if the amount of the conductive agent in the positive electrode mixture is less than 3% by mass, it is difficult to obtain sufficient current collecting efficiency, and the high rate discharge characteristics tend to deteriorate. On the other hand, if it exceeds 15% by mass, the amount of the positive electrode active material is reduced, resulting in a decrease in battery capacity.

In the invention of claims 1 to 4, the alkaline electrolyte is prepared by dissolving an alkaline substance such as potassium hydroxide or sodium hydroxide in water to a concentration of about 30 to 45% by mass. The mixing ratio is such that the nickel hydroxide-based particles 9 provided with the cobalt compound layer 9
About 2 to 5 parts by mass is preferable per 0 parts by mass.

The binder includes, for example, polyvinyl alcohol, polyacrylic acid salt, CMC, methyl cellulose, alginic acid and the like, and polyacrylic acid salt is particularly preferable because it has excellent chemical resistance against alkali. And this compounding ratio is 0.0 with respect to 90 mass parts of nickel hydroxide type particles provided with the cobalt compound layer.
About 1 to 1 part by mass is preferable.

In the inventions of claims 1 to 4, stirring and mixing of the positive electrode mixture composition is performed using a general-purpose mixing container such as a universal stirring mixer. The stirring and mixing conditions are appropriately selected depending on the selection of the positive electrode mixture composition content and composition ratio. The compression / crushing after the stirring / mixing is performed by a multi-stage roller compactor such as a two-stage type, a three-stage type or a four-stage type, and the thickness of the object to be compressed is 1
The compression is performed so as to be less than or equal to mm. Then, the object to be compressed is crushed by a crusher such as a granulator.

In the invention of claims 1 to 4, the compressed and crushed positive electrode mixture composition particles or powder are selected and collected by a sieving means or the like. That is, the particle size distribution
100 to 1800 μm, preferably 150 to 1500
Selected and sampled within the range of about μm. Then, the sieved positive electrode mixture composition particles have an average particle size distribution of 14 to 60.
It is in the form of granules having a mesh size (average particle size of 250 to 1300 μm).

In the cylindrical or plate-shaped positive electrode molding by the compression crushing and classification processes, the cylindrical or plate-shaped positive electrode molded body having a high packing density and excellent mechanical strength is complicated. It can be manufactured with high yield and in mass production without requiring any operation. In addition, the mechanical strength of the molded body is greatly improved, such as in the case of a tubular shape, the breakage is significantly improved, the handling operation, for example, the defectiveness in the battery assembly process is eliminated, and the yield is improved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will be described below with reference to FIG.

Preparation of positive electrode

To 90 parts by mass of nickel hydroxide particles having a high-order cobalt layer formed on the surface thereof, 5.4 parts by mass of graphite powder and 0.1 part by mass of a binder were added, and mixed by stirring for 10 minutes using a general-purpose mixing container. . Thereafter, 4.5 parts by mass of 40% by mass potassium hydroxide aqueous solution was added, and the mixture was mixed with a general-purpose mixing container to 30
Mix for minutes to obtain a positive electrode mixture mixture. Next, this positive electrode mixture mixture was adjusted by a roller compactor having a roller diameter of 105 mm so that the thickness of the object to be compressed would be 1 mm or less and compressed. Then, this object to be compressed was crushed by a crusher. Then, using a vibrating screener, average particle size distribution 1
A granular positive electrode mixture having 4 to 60 mesh (average particle size 250 to 1300 μm) was obtained.

Next, using the granular positive electrode mixture as a material,
Outer diameter 13.3 mm, inner diameter 9.0 mm, height (length) 1
A positive electrode material mixture pellet was prepared by pressure molding into a 3.7 mm hollow cylinder. In this pressure molding process, the material is easy to handle because the material is granular.
It was mass-produced without any damage in the molding process. Also,
When the molded body (positive electrode material mixture pellets) was cut and the internal microstructure was examined, it was found to be dense and a positive dispersion of positive electrode active material particles and conductive materials was formed, improving mechanical strength. Was also recognized. Table 1 shows the average density (g / cm3) and the average crush strength (N) of the 50 molded articles.

[0026]

[Table 1]

Fabrication of negative electrode

0.01 parts by weight of indium and 0.
Zinc alloy powder 64.58 having an average particle size of 100 to 300 μm and containing 01 parts by mass and 0.003 parts by mass of aluminum
0.381 parts by mass of polyacrylic acid (gelling agent) is added to parts by mass, and the mixture is stirred and mixed for 5 minutes in a general-purpose mixing container to obtain a uniform mixed system. On the other hand, 0.0006 parts by mass of tetrabutylammonium hydroxide is added to 35 parts by mass of a 35% by mass potassium hydroxide aqueous solution in which 3.5% by mass of zinc oxide is dissolved, and stirred and mixed for 10 minutes to sufficiently disperse. Then, to this dispersion, the zinc alloy powder-based mixture was gradually added over 4 minutes, and at the same time, 200 × 10 ⁵ Pa was added.
The mixture is stirred and mixed under a reduced pressure of (150 mmHg) or less, and further stirred and mixed for 5 minutes under a reduced pressure of 13.3 × 10 ⁵ Pa (10 mmHg) or less to prepare a gelled negative electrode having a substantially uniform composition system. .

Battery assembly

Next, using the positive electrode material mixture pellets prepared above and the gelled negative electrode, a single 3 type zinc alkaline battery whose schematic structure is shown in cross section in FIG. 1 was assembled by a conventional method. . In FIG. 1, reference numeral 1 denotes a bottomed cylindrical metal can (exterior can) that also serves as a positive electrode terminal. In the hollow of the metal can 1, three positive electrode material mixture pellets are stacked and again pressure-molded. The prepared positive electrode mixture 2 is filled and mounted. Further, a bottomed cylindrical separator 3 is mounted in the hollow portion of the positive electrode mixture 2, and a gelled negative electrode 4 is filled inside the separator 3.

In the gelled negative electrode 4, one end side of a brass negative electrode current collector rod 5 is inserted and arranged, and the outer peripheral surface of the negative electrode current collector rod 5 on the other end side protruding from the gelled negative electrode 4 is inserted. , And a double annular insulating gasket 6 made of polyamide resin is arranged between the inner peripheral surface of the opening of the metal can 1. A ring-shaped metal plate 7 is fitted and arranged between the double rings of the insulating gasket 6.

Further, the cap-shaped metal sealing plate 8 also serving as the negative electrode terminal is arranged and configured to abut the tip portion of the negative electrode current collector rod 5. Here, the opening edge portion of the metal can 1 is bent inward and the metal sealing plate 8 is inserted through the insulating gasket 6.
The metal can 1 has a configuration in which the opening edge is sealed.

Comparative Example

Production of Positive Electrode for Zinc Alkaline Battery of Example
In the constitution, the positive electrode material mixture pellets are produced under the same conditions as in the example except that the compression crushing after stirring and mixing the positive electrode material mixture composition and the classification treatment and process are omitted. Using this positive electrode material mixture pellet, a positive electrode AA zinc alkaline battery is manufactured under the same conditions as in the example. The average density (g / cm3) of 50 positive electrode material mixture pellet molded bodies,
The average crush strength (N) is also shown in Table 1.

Table 2 shows the average values when the battery capacities of 50 assembled zinc-alkali batteries were measured and evaluated in a temperature atmosphere of 20 ° C. after aging for about 48 hours.
Are shown respectively. As can be seen from Table 2, in the case of the example, it was improved by about 5% as compared with the comparative example.

[0036]

[Table 2]

Further, the constant current continuous discharge time up to 0.9 V (heavy load discharge characteristic) and the constant resistance continuous resistance time of 10Ω (medium load discharge characteristic) were examined. As a result, in the case of the example, while having the heavy load discharge characteristic similar to that of the comparative example, the medium load discharge characteristic was improved by about 5% as compared with the comparative example.

It should be noted that, in the above-mentioned examples, the graphite powder in the positive electrode mixture composition was omitted, and also when the positive electrode mixture pellets were molded under the same conditions, the packing density was the same as in the above-mentioned examples. Moreover, the mechanical strength was improved, and a positive electrode exhibiting high performance could be obtained with good yield. Further, the zinc alkaline battery in which a positive electrode was assembled with the positive electrode material mixture pellets had a high capacity and exhibited excellent heavy / medium load discharge characteristics as in the case of the above-mentioned examples.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, in the above, the manufacture of the cylindrical positive electrode for the AA zinc alkaline battery is described, but it is also applicable to the manufacture of the cylindrical single 1, single 2, single 4, single 5 or flat type. Applicable.

[0040]

According to the first to fourth aspects of the present invention, by compressing and crushing the positive electrode mixture composition particles (powder) and classifying the mixture, a high packing density and excellent mechanical strength can be obtained. A plate-shaped positive electrode molded body can be easily manufactured with high yield and can be mass-produced. Then, by improving the packing density of the molded body, the positive electrode capacity is increased to contribute to the improvement of the battery capacity, while the mechanical strength is improved,
In the case of a tubular shape, the breakage is greatly improved, defects in the battery assembly process are eliminated, and the yield is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main configuration of a zinc alkaline battery according to an embodiment.

[Explanation of symbols]

1 ... Metal can (exterior can) 2 ... Positive electrode mixture 3 …… Separator 4 ... Gel negative electrode 5 ... Negative electrode current collector 6 ... Insulating gasket 7: Ring-shaped metal plate 8: Metal sealing plate

Claims (4)

[Claims] 1. A step of stirring and mixing positive electrode composition components including nickel hydroxide-based particles having a cobalt compound layer on the surface, an alkaline electrolyte, and a binder, and compression crushing treatment of the stirred and mixed composition. A method for producing a positive electrode for an alkaline battery, comprising: a step of classifying the particles obtained by the application to obtain a granular mixed component; and a step of molding the granular mixed component. 2. The method for producing a positive electrode for an alkaline battery according to claim 1, wherein the positive electrode composition component contains a carbon-based conductive agent. 3. The particle size distribution of the granular positive electrode mixture is 14 to 60.
It is a mesh, The manufacturing method of the positive electrode for alkaline batteries of Claim 1 or Claim 2 characterized by the above-mentioned. 4. The cobalt compound layer is formed of at least one of cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide and metallic cobalt. The method for manufacturing the positive electrode for an alkaline battery according to any one of claims.