JPS6040669B2 - nickel electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-competitive nickel electrode used in nickel-cadmium storage batteries, nickel-zinc storage batteries, etc., and aims to improve the utilization rate of active materials.

Conventionally, this type of nickel positive electrode is made by molding a powder mixture of an active material such as nickel hydroxide or nickel oxide, a conductive material such as phosphorescent graphite or nickel metal powder, and a synthetic resin binder in appropriate amounts as a core material. After obtaining a molded body by molding the mixture into a paste or by applying a mixture made into a paste with a binder solution into a mold, the binder is heated to harden or heated to the melting point of the synthetic resin. It was manufactured by heating.

There is also a method in which a porous base bone having open cells is filled with a paste mixture and compressed under pressure. The manufacturing method of these non-sintered electrodes eliminates the need for a high-temperature reduction furnace to obtain a sintered substrate or the complicated process of converting active material salt into active material, unlike competitively bonded electrodes, and requires less preparation. All that is needed is a machine, pressure rollers, and other small equipment, and electrodes can be manufactured at low cost.

However, in terms of plate performance, these electrodes are inferior in terms of lifespan, high rate charge/discharge characteristics, and utilization rate compared to solidly connected type electrodes, and among these, improvement in utilization rate has been particularly desired. Conventionally, methods for improving the utilization rate of this type of nickel electrode include using a caustic alkaline aqueous solution containing lithium hydroxide as the electrolyte, and adding cobalt compounds, such as oxides and hydroxides, to the electrode. There are known methods to do this, but they are not yet sufficient. As a result of various studies on methods for improving the utilization rate of non-accumulation type nickel electrodes, the present invention has found that a configuration in which metallic nickel powder is used as the frost guiding layer and metallic cobalt or cobalt alloy powder is added is extremely effective. This is based on the discovery that That is, as shown in the examples below, compared to electrodes in which graphite is used as the conductive material and metallic cobalt is added, and electrodes in which metallic nickel is used as the conductive material and no metallic cobalt is added, electrodes in which metallic nickel is used as the conductive material and metallic cobalt is not added. Electrodes to which powder is added have dramatically improved utilization rates.

The reason for this is thought to be as follows. First, we investigated using the voltage-current scanning method and found that cobalt has an anode current (
This has the effect of lowering the potential at which the oxidation current begins to flow and shifting the oxygen generation potential toward the anode.

Such an effect is not seen when nickel is added alone. This trend is facilitated by the addition of both nickel and cobalt. This means that it becomes easier for the charging current to flow, making it easier to be charged, thus increasing the charging efficiency. Further, as a result of X-ray diffraction, in the coexistence of nickel and cobalt, the generation of y-Ni on day 00 during charging is suppressed, and the generation of B-Ni on day 00 is promoted.

When charging the active material, the more 8-Nj00 days are generated, the higher the utilization rate becomes, and the generation of y-Ni00 days tends to lower the utilization rate, and the addition of cobalt and nickel increases the y-N
This reduces the generation of i00 days and improves the utilization rate. In this way, the addition of cobalt and nickel exhibits an extremely superior effect than the addition of each alone due to the interaction between the two.

The present invention will be explained below with reference to Examples.

10 parts by weight of nickel hydroxide, 10 parts by weight of metallic nickel powder, and 5 parts by weight of metallic cobalt powder with a particle size that can pass through a 350-mesh sieve are slurried in a 2% by weight aqueous solution of carboxymethyl cellulose to form an open-cell, highly porous solution. After filling the nickel base with a method such as vacuum impregnation, it was dried and pressed to obtain a nickel electrode.

Figure 1 shows the nominal capacity 165 ratio h using this nickel positive electrode.
This shows an Ah nickel-cadmium storage battery.

1 is a paste-type negative electrode plate in which a few percent of synthetic monofilament paper is mixed with binders such as cadmium oxide and ethylene glycol, applied to a nickel net, dried and pressed, and has a capacity approximately twice that of the positive electrode capacity. I used something.

2 is a separator made of polyamide nonwoven fabric, which is connected to the negative electrode 1.
It is interposed between the positive electrode 3 and the positive electrode 3, and has a structure in which it protrudes from the ends of the positive and negative electrode plates on the 1st to 4th sides.

3 is a nickel positive electrode plate with a capacity of 1900 to 220 m.

4 is the lead of positive electrode 3, which is protected by an insulating tube.
It is designed to be electrically conductive to the sealing plate 5 by spot welding, and the sealing plate 5 becomes a positive electrode current collector.

6 is welded to the lead outer can 7 of the negative electrode 1, and the outer can 7 serves as a negative electrode current collector.

8 is a lower insulator, 9 is an upper insulator plate, and has a hole through which the positive electrode lead passes.

Reference numeral 10 denotes an insulating gasket which is seamed between the tip of the outer can 7 and the sealing plate 5 to maintain a sealed structure.

11 is a safety valve.

Note that a 7N KOH aqueous solution was used as the electrolyte. In the battery configured above, the current using the nickel electrode of the example is defined as A.

In addition, as a comparative example, B was obtained by increasing the amount of cobalt powder to 7 parts by weight and using phosphorescent graphite instead of nickel powder in the positive electrode mixture composition of the example, C was obtained by excluding cobalt powder, and C was obtained by excluding cobalt powder. The product excluding nickel powder is marked as ○. Figure 2 shows that for these batteries, 20±
A comparison of characteristics when charging at a 10 hour rate (0.1 C) at 2° C. and discharging at a 5 hour rate (0.1 C) is shown.

In addition, the following table shows a comparison of the actual utilization rate with respect to the theoretical amount of electricity calculated by examining the time until the battery voltage drops below 1.0 V under the same conditions as above and calculating the M(OH) as 28 eggs Ah per 21 evenings.
As is clear from the above results, the effect of the combination of cobalt and nickel is extremely large.

In the embodiment, a highly porous nickel matrix with open cells was used as the core material, but punched metal or metal net may also be used. Furthermore, the effect remains the same even if a cobalt-based alloy is used instead of cobalt powder. As for the amount of metallic cobalt or cobalt alloy added, even if 15% by weight or more is added, an increase in capacity cannot be expected due to the relationship between the packing density of the active material and the utilization rate, so the practical upper limit is 15% by weight or more. The lower limit is about 0.0% by weight.

When using metallic cobalt powder or cobalt alloy powder, the larger the particle size, the lower the degree of effect for the same amount added. The finer the particles, the more effective they are, so the particle size is preferably 100 mesh or less. In addition,
Although the case where Ni(OH)2 is used as the active material has been described, the same effect can be obtained when using nickel oxide or nickel oxyhydroxide as the host material. As described above, according to the present invention, in order to improve the utilization rate of non-sintered nickel electrodes,
Significant effects can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a nickel-cadmium battery used in an example of the present invention, and FIG. 2 shows a comparison of discharge characteristics of batteries using various nickel electrodes. Figure 1 Figure 2

Claims (1)

[Claims] 1 A non-sintered electrode in which a mixture containing at least a nickel compound as an active material, a conductive material, and a binder is supported on a conductive core material, the conductive material being a metallic nickel powder, and the mixture containing A nickel electrode characterized by a mixture of metallic cobalt or cobalt alloy powder.