JPS6327824B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electrode active material holder for a battery.

Battery electrodes can be roughly divided into paste type and pressure molding type used in secondary batteries and primary batteries such as lead batteries and alkaline batteries, active material electrodes such as clad type lead batteries and pocket type alkaline batteries. There are two methods: a method in which batteries are stored in a container, and a method in which alkaline batteries are sintered.

Each of these three methods has its advantages and disadvantages, and the paste or pressure molding method is easy to manufacture, low cost, and has excellent performance.
When used in secondary batteries, there is a problem in terms of lifespan. In addition, methods of storing in a container such as a clasp type or a pocket type are superior in terms of lifespan, but have problems in performance and cost. The final sintering ceremony is performance,
Although it has an excellent lifespan, the manufacturing method is complicated, so there is a cost problem.

However, when looking at batteries as a whole, low cost is still a big attraction, so paste type or pressure molding type are currently the mainstream.

The paste type or pressure molding type is extremely simple to manufacture because a conductive material or a binder is added to the battery active material powder as necessary to make it into a paste or to form an electrode in a semi-dry state. However, if the amount of binder is increased to increase the bonding strength of the active material, the electrical resistance will increase and the performance will deteriorate, so this type of electrode has a relatively low strength and the active material will deteriorate due to repeated charging and discharging. There is a lot of room for improvement in terms of service life, as the electrodes often fall off or swell.

On the other hand, in the case of the sintering method, a sintered body with very small pores is filled with active material in the form of a salt solution, and this is converted into an active material by electrolysis, thermal decomposition, alkali immersion, etc. Therefore, the bonding force to the sintered substrate is strong, and since the active material is held within the micropores, it is difficult to fall off and has a long life. It also has excellent properties because it has many contact areas and is highly conductive. However, due to the complexity of manufacturing, the cost is higher than methods in which the active material is directly pasted or pressurized.

One attempt to suppress these drawbacks of the sintered type, bring the characteristics and lifespan closer to those of the sintered type, and bring the price closer to the paste type is a method that uses foamed metal as the core material and directly fills it with active material. It is. This foam metal, for example, sold under the name Selmet by Sumitomo Electric Industries, Ltd., has a porosity of 90 to 97.
% and much larger compared to 78-84% of traditional sintering type. The pores have a size of 50 to 300μ, which allows them to be directly filled with active material powder, and because they have a three-dimensional structure, the active material to be filled can be contained in the skeleton.

From this, it is possible to make the characteristics and lifespan similar to sintered electrodes, but there are problems with voltage drop during large current discharge and strength when wound in a spiral shape when used in cylindrical batteries, and cracks may occur during winding. However, there remain problems such as damage. This is because foamed metal has a high porosity. This is due to the small proportion of metal, low conductivity, and low strength. In order to prevent these problems, the skeleton could be made larger, but this would reduce both the porosity and the pore diameter, and the characteristics of the foamed metal would be lost.

The present invention provides a simple and effective means for solving these problems without impairing the features of foam metal. The present invention provides a method for manufacturing an electrode active material support having a wire or band-like structure in which thin plates are integrated.

That is, after fixing wires or strips of natural or synthetic resin onto a foamed resin board, the entire body is plated with metal.In this way, the resin wires or strips can be used as a core material with a simple operation. A retained foamed metal can be obtained. Moreover, the resin wire or band-like plate is plated and integrated with the foamed metal part by the plated metal. This method is lighter overall and cheaper than using metal wires or strip plates, which have already been proposed. Even if resin is used instead of metal as the core material, since it is plated on top of it, a continuous layer of metal is formed in the same way as when metal wires or strips are used, which improves conductivity and strength. I found out that it was accepted.

In this case, as the foamed resin, known polyurethane, polystyrene, urea resin, polyvinyl chloride, etc. are used. Wires or bands (thin thin plates) of natural or synthetic resins include lines or bands of cotton, cellulose acetate, polyamide, polyester, vinyl chloride-acrylonitrile copolymer, etc., as well as polyvinyl chloride, polypropylene,
A strip plate made of polyethylene or the like is used. These wires or strips of resin may be bonded to the foamed resin surface with an adhesive, and if a thermoplastic resin is used as the foamed resin, the wires or strips of resin may have a higher melting point than the foamed resin. Using a band-shaped plate, the wire or the band-shaped plate may be heated to a higher temperature than the foamed resin and heat welded. The advantage of integrating with adhesive is that it is possible to achieve sufficient integration, and in the case of heat welding, the portion of the foamed resin that comes into contact with the resin wire or strip plate melts and shrinks due to heat, so there is no damage to the surface. Even when applied, the wire or band-shaped plate is partially embedded in the foamed resin plate, and the integration is sufficiently achieved after metal plating.

Electrode active material supports that use resin wires or strips as core materials are superior to previously proposed holders that use screen, expanded metal, or perforated plates as core materials. Almost the same effect can be expected even if the proportion occupied by the core material is reduced, and it also has advantages such as saving on the material cost occupied by the core material and further simplifying the production of the electrode active material support. Furthermore, it is possible to reduce weight and cost more than using metal wires or strip-shaped plates.

Furthermore, the thickness of the resin wire is not so limited when using the electrode as a flat plate, but when winding it in a spiral shape, there is a problem if it is too thick, so in the case of a wire, the outer diameter is 0.05 ~0.5
About mm is good. Also, the thickness of the strip plate is 0.05~0.3
mm, and the width is preferably about 1 to 5 mm. Also, in extreme cases, the spacing between the wires or strips may vary between electrodes 1 and 2.
It is effective to use one per sheet, but it is usually best to hold them at intervals of about 5 to 50 mm.

Regarding metal plating on the foamed resin plate after integrating the resin wire or strip plate, the known methods of electroless plating and then electrolytic plating are suitable for the present invention, which requires relatively thick plating. This plating connects the wire or band-shaped plate and the foamed resin plate with the plating metal, forming a continuous metal body plated on the line or band, and this layer is integrated with the foamed metal part. This is an extremely effective means for improving conductivity and strength.

Another effective use of this active material holder is alkaline batteries, in which case it is preferable to use nickel for the plating. When a skeleton is formed by nickel plating and the active material is held in it and wound in a spiral, heating is not effective because heat annealing after plating improves the flexibility and mechanical strength of the plating metal. In this case, the raw material foamed resin is decomposed and removed by heating, resulting in an active material support structure made of hollow metal.

In this way, an electrode active material support in which a metal wire or band structure is integrated with a foamed metal is obtained.
In addition to being easy to fill with active materials and having a long life,
Polarization at high discharge is small, and it is also possible to wind it in a spiral shape.

Examples of the present invention will be described below.

As shown in Figure 1A, it is made of polyamide wire with a wire diameter of 0.3 mm and coated with a benzene solution of polystyrene resin on one side of a 2.0 mm thick foamed urethane resin plate 1 with a porosity of about 95% and spaces 2. Glue wire 3 at 5mm intervals. At this time, the polyamide wire 3 is passed between the pressure rollers so that it is slightly sunk into the resin plate 1 as shown in FIG. 1B.

This is subjected to known nickel electroless plating and then electrolytic nickel plating to form a nickel plating with a total thickness of about 25μ. Then, it is washed with water and dried to form an electrode active material support, and the space 2 is filled with the active material for use. In order to make the holding body even lighter,
The case of further heat treatment will be described.
First, the plated holder is heated in air at a temperature of 600° C. for 20 minutes to decompose and remove the resin, thereby making the resin wire hollow as shown at 3' in FIG. 1B. It is then heated in hydrogen at 900°C for 15 minutes. This heating improves the strength of the nickel skeleton, softens the hollow metal wire 3' and gives it flexibility, making it convenient for winding into a spiral shape. Of course, these steps can be performed continuously.

In this way, the porosity is 96% and the thickness is about 2.1mm.
Foamed nickel having a line structure at 5 mm intervals is obtained. Then, after applying pressure to the lead plate attachment part,
Filled with 83 parts by weight of nickel hydroxide, 10 parts by weight of nickel powder, and 7 parts by weight of cobalt powder made into a paste with an aqueous solution of carboxymethyl cellulose, and further impregnated with a fluorine resin aqueous dispersion with a resin content of 4%. Pressurize the whole thing so that the height is about 1.1mm. The electrode thus obtained is cut into two size pieces. In this case, the direction of the line (or band) should be parallel to the length direction of the electrode.

After attaching a lead wire to the nickel electrode thus obtained, it was chemically converted and wound into a spiral shape by a known method to assemble a AA-size nickel-cadmium sealed battery. This battery is called A. On the other hand, as a comparative example, a foamed polyurethane resin was plated with nickel, and hereinafter a battery using a nickel electrode obtained in the same manner as described above is designated as B, and a battery using a conventional structural type nickel electrode is designated as C.

FIG. 2 shows the discharge curve of each battery at 500 mA discharge, and FIG. 3 shows the characteristics at 3 A discharge. As is clear from both sides, the capacity at 500 mA is A=B>C, and the voltage of B is slightly inferior to that of A and C. At 3A discharge, the capacity is A>B=
C, and the voltage is A=C>B. Note that this result was the average value of 10 batteries for each battery.

As described above, according to the method of the present invention, an electrode with excellent voltage and capacity can be obtained. The reason that B is inferior in terms of 3A discharge capacity is thought to be due to cracks that occurred when it was formed into a spiral shape, and also due to its slightly lower conductivity in terms of voltage.

Furthermore, in a life test by repeatedly charging at a rate of 10 hours and discharging at a rate of 1 hour, we investigated the point at which the initial capacity decreased to 60% as the lifespan, and found that A maintained 85% after 1300 cycles. B decreased to 60% after 1250 cycles, and C decreased to 60% after 1280 cycles. In this case, B is the one where the crack has had a negative impact on the lifespan, and the reason why A is better than C is that C
In A, since it is a sintered body of powder, the powder particles form the skeleton of the electrode base, whereas in A, it is a foamed metal, so the metal is continuously connected, and the corrosion resistance of the base is affected. This seems to be due to the fact that the active material is superior in terms of properties and there is less shedding of the active material.

In addition, when the present invention is applied to flat electrodes used for moving or stationary use, the voltage characteristics are improved to the same level as the sintered type, and the capacity is approximately 1.3 times higher.
It was also observed that the lifespan was improved by approximately 1.5 times.

As detailed above, when the present invention is applied to nickel electrodes for alkaline batteries, it has extremely excellent effects, but cadmium electrodes also have the same effect.
A similar effect can also be observed for lead batteries by using foamed metal containing lead as a main component and forming a lead wire structure.

[Brief explanation of the drawing]

Figure 1A is a schematic plan view of a foamed resin plate with resin wires fixed before nickel plating, Figure 1B is a schematic cross-sectional view, and Figure 2 is a 500mA discharge of a nickel-cadmium battery using various nickel electrodes. FIG. 3 is a diagram showing a discharge curve at 3A discharge. 1...Urethane foam resin plate, 2...Space, 3...
...Polyamide wire.

Claims (1)

[Claims] 1. An electrode active material holder for a battery, characterized in that wires 3 or band-like plates made of natural or synthetic resin are fixed to a foamed resin plate 1, and then metal plating is applied to the whole. Manufacturing method. 2. Claim 1, wherein the foamed resin board 1 is one selected from the group consisting of polyurethane, polystyrene, urea resin, and polyvinyl chloride.
A method for producing an electrode active material holder for a battery as described in 1. 3 The wire 3 or strip of natural or synthetic resin is made of cotton, cellulose acetate, polyamide,
The method for producing an electrode active material holder for a battery according to claim 1, wherein the holder is selected from the group consisting of polyester and vinyl chloride-acrylonitrile copolymer. 4. The method of manufacturing an electrode active material holder for a battery according to claim 1, wherein the means for fixing the wire 3 or the strip plate to the foamed resin plate 1 is adhesive or thermal welding. 5. The method for producing a battery electrode active material holder according to claim 1, wherein the metal plating is nickel plating. 6. A wire 3 or band-like plate made of natural or synthetic resin is fixed to a foamed resin plate 1, and then metal plating is applied to the whole of the plate, followed by heating to decompose and remove the resin content and annealing the metal part. A method for manufacturing an electrode active material holder for batteries. 7. The method of manufacturing an electrode active material holder for a battery according to claim 6, wherein the means for fixing the wire 3 or the strip plate to the foamed resin plate 1 is adhesion or thermal welding. 8. The method for producing a battery electrode active material holder according to claim 6, wherein the metal plating is nickel plating.