JPH0554891A - Paste type cadmium anode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To enhance the oxygen-gas absorption performance and the high rate discharge characteristics of an alkaline storage battery based on the use of a paste type cadmium anode plate, by providing a conductor layer composed of a furnace black powder and a thermally gelatinizable cellulose derivative adhesive paste on the surface of the paste type cadmium anode plate for alkaline battery. CONSTITUTION:100 parts by weight of water, 5 weight part of furnace black powder (specific surface area 1475m<2>/g, DBP oil absorption 3.3ml/g), and 5 parts by weight of methyl cellulose are mixed while agitated, to prepare a carbon powder suspension. This suspension is applied thin onto the surface of the formed paste type cadmium anode plate and is dried to obtain a complete anode plate. This anode plate is combined with a sintered type cathode plate to prepare a sealed type nickel/cadmium battery. The furnace black preferably has a specific surface area of 1000 to 1500m<2>/g, and DBP oil absorption of 3 to 5ml/g. Further, the adhesive paste preferably is hydroxypropyl methyl cellulose, or hydroxy propyl cellulose, in addition to methyl cellulose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in oxygen gas absorption performance of a paste type cadmium cathode plate used in a sealed alkaline storage battery and an improvement in high rate discharge characteristics of a battery using the cathode plate.

[0002]

2. Description of the Related Art Conventionally, a paste type cadmium cathode plate for an alkaline storage battery is a cadmium oxide, a cadmium hydroxide,
A paste, a solvent, reinforcing fibers, etc. are added to an active material powder made of metal cadmium, etc., and these are kneaded to form a paste,
This paste is applied to both surfaces of a conductive core material such as a nickel-plated iron perforated plate and dried. Therefore, compared with the sintered cadmium cathode plate, the manufacturing process can be simplified and the active material filling amount can be increased, so that the energy density can be increased.

However, since the paste-type cadmium cathode plate has the above-mentioned structure, it does not have a conductive network of a nickel-sintered body like that of the sintered type in the active material layer, and
Since cadmium hydroxide, which is a discharge product, has low conductivity, metal cadmium generated during charging tends to be unevenly distributed in a highly conductive part, particularly in the vicinity of the core material. When the battery is overcharged, oxygen gas is generated from the anode plate and absorbed by the reaction represented by the following formula (1) at the cathode plate, but this reaction easily occurs on the surface of the cathode plate. As described above, the paste type cadmium cathode plate in which metal cadmium is hard to be generated on the surface of the electrode plate has a drawback that the oxygen gas absorption performance is low.

[0004]

## STR00001 ## Cd + 1 / 2O ₂ + H ₂ O → Cd (OH) _{2 In} order to solve this drawback, Japanese Patent Laid-Open No. 60-63875 and Japanese Patent Laid-Open No. 60-202666 disclose a paste type cadmium cathode plate surface. It has been proposed to form an acetylene black-containing layer and increase the conductivity of the surface of the electrode plate so that metal cadmium is also generated on the surface of the electrode plate during charging to improve the oxygen gas absorption performance.

[0005]

However, in the case of forming an acetylene black-containing layer on the surface of a paste type cadmium cathode plate, a suspension in which acetylene black and a paste for preventing falling are uniformly dispersed in a solvent. Is used to immerse the cathode plate in the suspension or to apply the suspension to the surface of the cathode plate. In order to ensure the homogeneity of the coating layer, the suspension needs to be sufficiently stirred to improve the dispersibility, but the stirring causes the chain structure of acetylene black to collapse, which lowers the conductivity. However, there is a problem that sufficient oxygen gas absorption performance cannot be obtained. If the coating layer is thickened to ensure conductivity, the oxygen gas permeability will deteriorate and the diffusion of the electrolyte will be hindered, which will not only reduce the oxygen gas absorption performance, but also the battery voltage characteristics during high-rate discharge. There was a problem that

An object of the present invention is to eliminate the above problems, to further improve the oxygen gas absorption performance, and to provide a paste type cadmium cathode plate which is excellent in high rate discharge characteristics.

[0007]

In order to solve the above problems, the paste type cadmium cathode plate for an alkaline storage battery of the present invention has an active material containing at least one of cadmium oxide, cadmium hydroxide and metal cadmium as a main active material. On the surface of the material layer,
BET specific surface area of 1000 to 1500 m ² / g, dibutyl phthalate oil absorption (hereinafter referred to as “DBP oil absorption”) is 3 to
A conductive layer comprising a furnace black powder of 5 ml / g and a heat-gelling cellulose dielectric paste is provided, which is favorably used as a heat-gelling cellulose derivative paste. Any one of methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, or a mixture thereof is used.

[0008]

According to the present invention, as a result of intensive studies, the conductive layer provided on the surface of the cathode plate is composed of a furnace black powder having a high specific surface area and a high DBP oil absorption amount and a cellulose derivative paste which is heat-gelled to obtain an oxygen gas. It is based on the finding that the absorption performance is further improved, and at the same time, the high rate discharge characteristic is also improved. Having a high specific surface area indicates that there are many micropores that cannot penetrate the electrolyte, and that oxygen gas has good permeability in the conductive layer and that it has a high DBP oil absorption has a chain structure or a hollow structure. It shows that the structure is well developed, the conductivity is not deteriorated even by stirring during the preparation of the suspension for forming the conductive layer, and it is possible to effectively generate metal cadmium on the surface of the cathode plate. Since the liquid retaining property of the liquid is good, the diffusion of the electrolytic solution at the time of high-rate discharge is good, and further, by using the cellulose derivative paste which thermally gels, after applying the above suspension to the surface of the cathode plate, Since the shrinkage and the densification of the coating layer during drying are suppressed, it is considered that the main reason is that the above-mentioned gas permeability and electrolyte retaining property are maintained.

[0009]

EXAMPLE An example of the present invention will be described. [Example 1] Cadmium oxide powder, nylon reinforcing fiber,
A paste type cadmium cathode plate prepared by the conventional method of mixing a polyvinyl alcohol paste and an ethylene glycol solvent to form a paste, coating it on a nickel-plated iron perforated plate, and drying it in an aqueous sodium hydroxide solution. It was formed by charging and discharging a nickel plate as a counter electrode, then washed with water and dried. On the other hand, 100 parts by weight of water,
Furnace black powder a (specific surface area 1475 m ² /
g, DBP oil absorption amount 3.3 ml / g) 5 parts by weight, and methyl cellulose 5 parts by weight were charged into a spiral mixer, and 15
A carbon powder suspension was prepared by stirring and mixing at 0 rpm for 1 hour. A carbon powder suspension was thinly applied to the surface of the formed paste type cadmium cathode plate so as to have a coating amount of 6 to 7 mg / cm ² , and dried to obtain a completed cathode plate. This cathode plate was wound in combination with a sintered anode plate produced by a known method via a nylon non-woven fabric separator, and was wound together with an alkaline electrolyte in a battery case to have a nominal capacity of 120.
A 0 mAh sealed nickel-cadmium battery A was produced. Further, the furnace black b (specific surface area 1270 m ² / g, DBP oil absorption of 4.5 ml / g) was used in place of the furnace black a used in the carbon powder coating layer on the surface of the cathode plate of the battery A. A battery B having a structure was produced.

Example 2 In the battery A of Example 1,
Except that the methylcellulose paste used for the carbon coating layer on the surface of the cathode plate was replaced with hydroxypropylmethylcellulose and hydroxypropylcellulose, and the viscosity of the carbon powder suspension was adjusted to be the same as in Example 1, the same constitution was obtained. Batteries C and D were produced respectively.

Comparative Example 1 A battery E having the same structure as in Example 1 except that the carbon powder coating layer was not provided on the surface of the cathode plate was manufactured.

[Comparative Example 2] In Example 1, instead of the furnace black used for the carbon coating layer on the surface of the cathode plate, acetylene black (specific surface area 64 m ² / g, DB
A battery F having the same configuration was prepared except that a P oil absorption amount of 1.2 ml / g) was used.

[Comparative Example 3] In the battery A of Example 1,
Batteries having the same configuration except that carboxymethyl cellulose that did not gel heat was used in place of the methyl cellulose paste using the carbon coating layer on the surface of the cathode plate, and the viscosity of the carbon powder suspension was adjusted to be the same as in Example 1. G was made.

The batteries A to G thus produced were provided with an opening, and the pressure gauge was attached in a sealed state.
Then, the battery was charged with a current of 1.2 A (1 C), and the internal pressure change of the battery at that time was measured. Table 1 shows the battery internal pressure after 2.5 hours. In addition, charging is performed at a current of 1 C for each 1.
Table 1 also shows the discharge capacities up to a battery voltage of 1 V when discharged at 1.2 A, 3.6 A, and 6 A after 5 hours of discharge.

[0015]

[Table 1]

The following can be seen from Table 1.

Batteries A to D, F, and G having a carbon coating layer on the surface of the cathode plate had apparently lower battery internal pressures as compared with Battery E having no carbon coating layer, and the oxygen gas of the cathode plate was reduced. Absorption performance is improved.

The carbon coating layer on the surface of the cathode plate has a BET specific surface area of 1000 to 1500 m ² / g and a DBP oil absorption of 3 to
The batteries A to D of the present invention using 5 ml / g of furnace black have a lower battery internal pressure than the comparative battery F using acetylene black and are excellent in oxygen gas absorption performance. Further, it is excellent in that the capacity is not decreased in the high rate discharge.

Batteries A to D of the present invention in which a heat-gelling cellulose derivative paste is used in the carbon coating layer on the surface of the cathode plate.
In comparison with Comparative Battery G, which uses a carboxymethyl cellulose paste that does not gel thermally, the internal pressure of the battery is even lower and the oxygen gas absorption performance is excellent. Further, it is excellent in that the capacity is not decreased in the high rate discharge.

As described above, the battery of the present invention is superior to the comparative example in the oxygen gas absorption performance during charging and also in the high rate discharge performance. This is because the conductive layer on the surface of the cathode plate has high conductivity, metal cadmium is likely to be generated on the surface, and the gas permeability of the conductive layer and the liquid retaining property of the electrolytic solution are good. It is shown that the cathode plate of (1) has both.

[0021]

As described above, the paste-type cadmium cathode plate for an alkaline storage battery according to the present invention is a cellulose derivative which has a high specific surface area and a high DBP oil absorption amount on the surface of the active material layer and a thermal gelation. Since a conductive layer made of a paste is provided, compared with the conventional conductive layer using acetylene black, the oxygen gas absorption performance of the cathode plate is further improved, and the capacity is less reduced even at high rate discharge. Is. This excellent property is made possible only by combining the physical properties of the carbon powder used for the conductive layer and the properties of the paste according to the purpose.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taisuke Kuroda 1-1-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Shin-Kindo Electric Co., Ltd. (72) Inventor Yuuki Tsuji 2-1-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 1 Shinshin Todo Electric Co., Ltd.

Claims (2)

[Claims] 1. A cathode plate in which a conductive layer made of carbon powder is provided on the surface of an active material layer containing at least one of cadmium oxide, cadmium hydroxide and metal cadmium as a main active material. BET specific surface area 1000
~1500m ² / g, DBP oil absorption amount 3-5 ml / g in a first black powder and cellulose dielectric paste fee for an alkaline storage battery paste type cadmium negative electrode plate, characterized in that it consists of thermogelling. 2. A heat-gelling cellulose derivative paste is methylcellulose, hydroxypropylmethylcellulose,
The paste type cadmium cathode plate for an alkaline storage battery according to claim 1, which is one of hydroxypropyl cellulose or a mixture thereof.