JPS641909B2 - - Google Patents

Description

[Detailed Description of the Invention] 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, and clad type and pressure molding type used in lead batteries and alkaline batteries. There are methods such as a pocket type in which the active material is stored in a container, and there is also a sintered type for alkaline batteries.

Each of these three methods has its advantages and disadvantages, and the paste or pressure type is easy to manufacture, low cost, and has excellent performance.
When used in secondary batteries, there is a problem in terms of lifespan. Furthermore, although the method of storing the battery in a container is superior in terms of service life, it has problems in performance and cost. The last type of sintering method has excellent performance and longevity, but 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 or pressure molding types are currently the mainstream.

The paste type or pressure molding type is extremely simple to manufacture because the battery active material powder is made into a paste by adding a conductive material or a binder as necessary, or is made into 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, the active material in the sintered body with very small pores is filled with its salt solution, and this is converted into the active material, so the bonding force to the sintered base is large. Moreover, since the active material is retained 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 the manufacturing process, 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 foamed metal, such as the one sold under the name Selmet by Sumitomo Electric, has a porosity of 90-97%, which is much larger than the 78-84% of conventional sintered metal, and the pore size is 50%. It has a size of ~300μ, which allows it to be directly filled with active material powder, and has a three-dimensional structure, so it can contain the filled active material in its 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 used in cylindrical batteries, and cracks occur during winding. Furthermore, there remain problems such as damage. In either case, this is due to the fact that foamed metal has a large porosity and a small proportion of metal, and this is due to its low conductivity and low strength. In order to prevent these problems, it would be better to make the skeleton larger, but
If this happens, both the porosity and the pore diameter will become small, and the features of foamed metal will 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 integrated battery electrode active material holder.

That is, a metal wire or band is fixed on or within one side of a foamed resin plate, and the whole is plated with metal. In this way, a foamed metal holding a metal wire or band as a core material can be obtained with a simple operation. Moreover, the metal wire or band is integrated with the foam metal by plating metal.

In this case, as the foamed resin, well-known polyurethane, polystyrene, urea resin, polyvinyl chloride, etc. are used, and this electrode active material holder is the most effective metal wire or strip (thin thin plate) for alkaline batteries. As the material, nickel, iron, stainless steel, etc. are used. Further, these metal wires or bands may be bonded to the foamed resin surface with an adhesive, or if a thermoplastic resin is used, the metal wires or bands may be heated and then thermally welded.
The advantage of integrating with adhesive is that it can be integrated sufficiently, and in the case of heat welding,
Heat melts and shrinks the part of the foamed resin that comes in contact with the metal wire or band, so even if it is applied to the surface, the metal wire or band will be partially embedded in the foamed resin board, and it will not be integrated after metal plating. It is important that the In addition, when inserting into a foamed resin plate, it is better to use a wire. Although this method is extremely preferable as an electrode active material holder, it is somewhat complicated to operate, so in many cases it is preferable to insert it into the surface of the former. It is sufficient to integrate them.

Electrode active material holders with metal wires or strips as core materials have a higher core material than active material holders with previously proposed screens, expanded metals, or perforated plates as core materials. Almost the same effect can be expected even if the ratio is reduced, and it also has advantages such as saving on the material cost of the core material and simplifying the production of the electrode active material holder.

Furthermore, the thickness of the metal wire is not so limited when the electrode is used as a flat plate, but when it is wound in a spiral shape, there is a problem that the resistance during winding increases if it is too thick. The outer diameter is preferably about 0.05 to 0.5 mm. Further, the thickness of the metal strip is preferably 0.05 to 0.3 mm, and the width thereof is preferably about 1 to 5 mm. As for the spacing between the metal wires or bands, in extreme cases even one metal wire per electrode may be effective, but normally it is best to keep them at intervals of about 5 to 50 mm.

Regarding metal plating on the foamed resin plate after integrating the metal wire or band, a known method of applying electroless plating and then electrolytic plating is not suitable for the present invention, which requires relatively thick plating. This plating allows the metal wire or band to be connected to the foamed resin plate, and is an extremely effective means for integrating the metal wire or band with the foamed metal.

As already mentioned, the most effective application for such an electrode active material holder is an alkaline battery, and therefore nickel plating is preferable as the metal plating. For metal wires or bands, nickel,
I mentioned that iron, stainless steel, etc. are superior, but
For example, if the only issue is strength for spiral winding, metals such as copper wire, which are not harmful to alkaline batteries, can also be used.

Furthermore, when the skeleton is formed by metal plating as described above, heating is effective because the strength is improved by heating and annealing in an inert atmosphere after plating. The appropriate heating temperature for annealing in the case of nickel plating is 750 to 850°C. In this case, the raw material foamed resin is heated at a temperature below the annealing temperature and has a structure in which it is decomposed and removed.

As described above, according to the present invention, an electrode active material holder in which a metal wire or band is integrated with a foamed metal can be obtained, which is easy to fill with active material, has a long life, and has small polarization at high discharge. , it is also possible to wind it in a spiral shape.

Hereinafter, the present invention will be explained with reference to examples thereof.

As shown in Figure 1A, on one side of a 2.0 mm thick urethane resin board 1 with a porosity of about 95% and a space 2,
Nickel wires 3 with a wire diameter of 0.3 mm coated with a benzene solution of polystyrene resin are glued at intervals of 10 mm.
At this time, pressure is applied between the rollers to integrate the nickel wire so that it is lightly sunk into the resin plate 1.

FIG. 1B is a cross-sectional view of a foamed urethane resin plate into which the nickel wire 3 is slightly recessed.

This was subjected to known nickel electroless plating and then electrolytic plating to form nickel plating with a total thickness of about 25 μm. By washing this with water and drying it, an active material holder having a nickel plating layer connected to the foamed urethane resin plate 1 and the nickel wire 3 is obtained. In addition, this active material support was heated to 600℃ in the air.
When heated for 20 minutes to decompose and remove the resin content, and then heated in hydrogen for 15 minutes at 900℃, the nickel strength of the skeleton increases due to the annealing effect of heating, and the nickel wire softens and becomes more flexible. This makes it convenient for winding in a spiral shape. Of course, these steps can be performed continuously.

With this method, the porosity is about 96% and the thickness is about 2.1mm.
An active material holder made of foamed nickel with integrated nickel wire is obtained. Next, after pressurizing the lead plate mounting area, it is filled with a paste made of 82 parts by weight of nickel hydroxide, 12 parts by weight of nickel powder, and 6 parts by weight of cobalt powder with an aqueous solution of carboxymethyl cellulose, and then filled with a paste made from an aqueous solution of carboxymethyl cellulose. After impregnating with spargeon (resin content: 4% by weight), pressure is applied so that the thickness becomes approximately 1.1 mm. The electrode thus obtained is cut into two size pieces. In this case, the metal wire (or band) should be parallel to the long direction of the electrode. After attaching a lead plate to the nickel electrode thus obtained, it was chemically formed and wound into a spiral shape using a known method to assemble a AA-size nickel-cadmium sealed battery. This battery is called A. As comparative examples, B is a battery using a nickel electrode obtained in the same manner as above except that the metal wire is not integrated, and C is a battery using a conventional sintered nickel electrode.

Fig. 2 shows the discharge curve when each battery was discharged with a current of 400 mA, and Fig. 3 shows the characteristics when discharging at 3 A. As is clear from both figures,
The capacity at 400mA is A=B>C, and the voltage is B
is slightly inferior to A and C. At 3A discharge, the capacity becomes A>B=C, and the voltage becomes A=C>B. Note that this result was the average value of 10 batteries for each battery. As described above, the electrode according to the present invention has excellent voltage and capacity. The reason why B is inferior in terms of 3A capacity is probably due to the cracks that occurred when it was wound in a spiral shape, and it is also probably 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 cracks have had a negative effect on the lifespan, and A is better than C.
Since it is a sintered body, the powder particles form a skeleton as an electrode active material holder, whereas
This seems to be due to the fact that in A, the metals are continuously connected and the active material holder has excellent corrosion resistance, and there is less chance of the filled active material falling out.

In addition, in the case of flat electrodes used for mobile or stationary use, the voltage characteristics can be improved to the same level as the sintered type, the capacity can be improved by about 1.3 times, and the life span can be improved by about 1.5 times. Admitted.

As detailed above, it has extremely excellent effects as a nickel electrode for alkaline batteries. The same effect can also be obtained when applied to cadmium poles.
Furthermore, similar effects can be obtained for lead batteries by using a foamed metal containing lead as a main component and by using an acid-resistant metal such as lead wire.

[Brief explanation of drawings]

FIG. 1A is a schematic plan view showing an active material holder before metal plating in an example of the present invention, FIG. 1B is a schematic cross-sectional view thereof, and FIG. Figure 3 is a diagram comparing the characteristics at 3A discharge. 1... Foamed resin board, 2... Space, 3... Nickel wire.

Claims (1)

[Claims] 1. An electrode active material holder for a battery, characterized in that a foamed resin plate 1 to which a metal wire 3 or a metal band is fixed is plated with metal, the resin is decomposed and removed by heating, and then the plated metal is annealed by heating. manufacturing method.