JPS59186261A - Method for manufacture of cadmium electrode - Google Patents

Abstract

PURPOSE:To obtain a non-sintered cadmium electrode providing characteristics close to a sintered cadmium electrode under severe operating conditions while still reserving ease of manufacture, by using the active material mixture of one or both cadmium oxide and cadmium hydroxide and a specific amount of nickel powder. CONSTITUTION:An active material mixture of 70-50pts.wt., for the equivalent of cadmium oxide, of one or both of cadmium oxide and cadmium hydroxide and 30-50pts.wt. of nickel powder is spread over a core member and pressed together. As the active material, cadmium oxide having a larger apparent density and being easy for filling is more preferable, but cadmium hydroxide or mixture of both can also be used. As the nickel powder, carbonyl nickel is preferable, and as the core member, punching metal, expanded metal, net, or the like is used. As the bonding agent, hydrophilic material with low electrical resistivity such as carboxyl methyl cellulose or polyvinyl alcohol is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing non-sintered cadmium electrodes for use in nickel-cadmium storage batteries and the like.

Here are the configurations of conventional examples and their problems. This sintered electrode has an active material filled in the micropores of a sintered nickel substrate, so it has excellent battery characteristics such as large current discharge characteristics, rapid charging characteristics, and long life.

However, as is well known, the manufacturing method involved in manufacturing the sintered body and filling the active material is complicated, making it considerably more expensive than other electrodes, which has remained a major problem.

Therefore, many attempts have been made to simplify the manufacturing method and bring the performance closer to that of the sintered method, such as the non-sintered method or the pressurized method.

A structure called a paste type has been developed as an example, and has been particularly adopted in a closed type system in which a limited amount of electrolyte is used. In other words, even though it is a non-sintered type, cadmium electrodes are superior to nickel electrodes in the following ways:
This made it possible to put the electrode into practical use first. In other words, when it is discharged, it becomes cadmium hydroxide, which has no electrical conductivity, but when it is charged, it becomes metallic cadmium, which has good electrical conductivity. Furthermore, since it becomes metal when charged, the degree of swelling and falling off is extremely small even after repeated charging and discharging. These are the main reasons that made it possible to put it into practical use.These things make it possible to reduce the amount of binder required to suppress the decrease in strength.
This means that voltage drops and decreases in utilization are suppressed to some extent.

However, it cannot be denied that compared to sintered cadmium electrodes, there are differences in characteristics, especially under harsh conditions. For example, the potential during a sudden discharge such as 10C, -5°
Potential and gas absorption capacity when charged at 10°C, charge/discharge performance after long-term storage at 50"C, discharge performance after overdischarge, 50"
It can be said that there are more problems with the lifespan of ``C'' compared to the sintered type.

As a result of various studies, the main cause of these problems has been whether the active material becomes metallic cadmium with excellent conductivity during charging, or whether the active material is formed in a microporous conductive framework such as a sintered type. It was found that when insulating cadmium hydroxide is formed between metal cadmium particles, the good electrical conductivity of the sintered type is lost compared to a structure where the structure is maintained.

Purpose of the Invention The present invention relates to such a non-sintered cadmium electrode.
The object of the present invention is to provide a non-sintered cadmium electrode that has characteristics close to those of the sintered cadmium electrode even under the above-mentioned severe usage conditions, while maintaining the ease of production.

Structure of the Invention The present invention uses an active material mixture containing 30 to 50 parts by weight of nickel powder to 70 to 5 parts by weight of at least one cadmium oxide selected from the group consisting of cadmium oxide and cadmium hydroxide. The electrodes are manufactured using the same method.

In non-sintered cadmium electrodes, the mixing ratio of the conductive material in the mixture of active material raw materials such as cadmium oxide or cadmium hydroxide and nickel or graphite powder as a conductive material is calculated based on the amount of cadmium oxide in the active material raw material. In this case, the optimum weight ratio has conventionally been about 10 to 20. The reason for this is that adding a large amount of these conductive materials would reduce the amount of active material accordingly, and there was a concern that the absolute capacity would be insufficient.

However, the present inventors changed the mixing ratio of nickel to 30 to 30.
By adding a large amount such as 50% by weight, the utilization rate of the cadmium electrode is greatly improved and the conductivity is greatly improved, so although the absolute capacity is slightly reduced, it is suitable for use as a negative electrode under harsh conditions. It was discovered that the properties were significantly improved, and that it was possible to obtain properties close to those of sintered cadmium electrodes while maintaining the simplicity of the manufacturing method.

In this case, the active material is most preferably cadmium oxide, which has a large apparent density and is therefore easy to fill.Cadmium hydroxide can also be used, or both may be mixed. Further, as the nickel powder, known carbonyl nickel is preferred, and its addition ratio is 30 to 50 parts by weight, preferably 35 to 45 parts by weight. In addition, there are two types of non-sintered type: a powder press type and a paste type, and although the latter is easier to manufacture, the present invention can be applied to either of them. punching metal,
Extended metal, net, etc. are used. As the binder, polyethylene, polyvinyl chloride, fluororesin, etc. may be used, but it is preferable to use a hydrophilic material with low electrical resistance such as carboquine methyl cellulose or polyvinyl alcohol.

Description of examples A method for manufacturing a paste-type cadmium electrode will be described as an example.

First, as a paste O material, carbonyl nickel powder was mixed with cadmium oxide that had passed through 100 mm in a mixing ratio of 30, 35, 40, 45.

The mixture was mixed to 60% by weight. This mixed powder 1k
In order to increase the binding strength, 5.6 g of vinyl chloride-acrylonitrile copolymer fibers (diameter, 2 cavities, average length 5111 m) were added to No. 7 and thoroughly mixed.

To this, in order to prevent the change of cadmium oxide to hydroxide during production, a 2.2 weight-weight ethylene glycol solution of polyvinyl alcohol (f, y) 3009 was added, heated to approximately 135°C, and dissolved and mixed. do. This was used to coat a nickel-plated iron punching metal with a thickness of 0.1 mm, a hole diameter of 2 mm, and a hole pitch of 2.5 mm. Pass this between slits with a gap of 0.7 mm to a length of 0.9 m.
Obtain m-thick cadmium electrode. Then, the thickness is adjusted to 0.75 mm by passing it between rollers.

Furthermore, an amount of electricity corresponding to 20% of the filling capacity is charged in an aqueous solution of 15% by weight of caustic potash.

In this way, the obtained cadmium pole was 38 mm wide and 260 mm long.
It was cut into mm. In addition to this, a known sintered two-sokel pole (width 38 msn, length 220 pieces, thickness 0.62 mm) was used.
and a polyamide nonwoven fabric as a separator.
A cylindrical sealed battery of the same size was constructed. The capacity is based on the positive polarity rule and is nominally 2200mAh.

Further, as a comparative example, a battery was constructed using a cadmium electrode in which the mixing ratio of nickel powder to cadmium oxide was 25, 20.15% by weight.

Table 1 shows the average value (corresponding to the terminal voltage at the middle of the discharge time) of the voltage of the rapid discharge characteristics of these batteries at 35°C. Note that the battery is a battery that uses sintered cadmium electrodes.

(Leaving space below) Table 1 Next, as an example of low temperature, we performed 10 charges at -5°C for 2 hours and investigated the peak voltage until charging completion and the peak internal pressure of the voltage at that time, as shown in Table 2. Became.

In addition to Table 2, the charging and discharging characteristics after being left at high temperatures and the batteries using the overdischarged ram negative electrode showed the same characteristics as conventional batteries equipped with a sintered cadmium negative electrode.

Effects of the Invention As described above, according to the present invention, the simplicity of the manufacturing method is its i.
t, a non-sintered cadmium negative electrode comparable in properties to a sintered cadmium electrode is obtained.

Claims (1)

[Claims] At least one type of cadmium oxide selected from the group consisting of cadmium oxide and cadmium hydroxide, equivalent to 70 to 50
A method for producing a cadmium electrode, comprising the steps of applying an active material mixture containing 30 to 5 parts by weight of nickel powder to a core material and applying pressure.