JPH05314981A - Alkaline storage battery and manufacture thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the cost of alkaline storage batteries and improve high rate discharge characteristics. [Constitution] A positive electrode plate is prepared by using carbon hydroxide as a conductive agent and water glass as a binder in nickel hydroxide which is a positive electrode active material. [Effect] With this configuration, it is possible to significantly reduce the amount of expensive cobalt hydroxide and reduce the cost, and it is possible to significantly improve the high-rate discharge characteristics as compared with the battery using the conventional carbon-added positive electrode. Becomes

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery which uses hydrogen storage alloy or cadmium for the negative electrode and nickel hydroxide for the positive electrode active material and is inexpensive and excellent in high rate discharge characteristics, and a method for producing the same.

[0002]

2. Description of the Related Art An alkaline storage battery using a hydrogen storage alloy or cadmium for a negative electrode and nickel hydroxide for a positive electrode active material is well known as a battery excellent in high rate discharge. The hydrogen storage alloy and cadmium of the negative electrode are substances having good conductivity during discharge. On the other hand, in the positive electrode, the conductivity of nickel oxyhydroxide generated by charging is good, but the conductivity of nickel hydroxide, which is a discharge product, is poor. Therefore, cobalt hydroxide is added to the positive electrode mixture in order to improve the conductivity from the nickel hydroxide particles in the positive electrode to the nickel substrate, which is a current collector, and especially the frequently used foamed nickel.
Cobalt hydroxide turned into cobalt oxyhydroxide having good conductivity during charging, which improved conductivity between the nickel hydroxide particles and the nickel current collector, enabling high rate discharge.
However, it has been a problem to increase the cost and further improve the high rate discharge characteristics by using the cobalt compound. Therefore, it has been attempted to add carbon such as graphite to the positive electrode mixture and make an aqueous paste using carboxymethyl cellulose as a binder to make a positive electrode plate from this, but it has not been possible to improve the high-rate discharge characteristics. It was

[0003]

However, in such an aqueous paste using such a conventional carboxymethyl cellulose as a binder, carbon is dispersed well and it is well arranged around nickel hydroxide which is an active material. However, since carboxymethyl cellulose gradually dissolves in an alkaline electrolyte and decomposes, carbon that is dispersed and arranged well is liberated from around the active material and falls off, so that there is a problem that conductivity cannot be imparted to the active material. there were.

The present invention is intended to solve such problems, and an object thereof is to improve an aqueous paste of a positive electrode active material, to reduce the cost of an alkaline storage battery, and to improve high rate discharge characteristics. ..

[0005]

To solve this problem, the present invention provides a reversible negative electrode such as a hydrogen storage alloy or cadmium, a positive electrode made of nickel hydroxide, and an alkaline storage battery using an alkaline aqueous solution as an electrolyte, It is characterized in that carbon as a conductive agent and water glass as a binder are used for the positive electrode.

Further, as a method for producing a positive electrode, carbon as a conductive agent and water glass as a binder are previously made into a paste by using water, and nickel hydroxide is added to and mixed with an aqueous paste, which is then dried to produce a positive electrode. It was done.

[0007]

A conventional positive electrode mixture for an alkaline storage battery is composed of, for example, 100 g of nickel hydroxide, 8 g of metallic cobalt, 6 g of cobalt hydroxide and 3 g of zinc oxide.
/ 117 g, that is, a theoretical electric capacity of 0.247 Ah / g. Metallic cobalt is added in order to make the negative electrode extra charged as compared with the positive electrode, that is, to make a battery with positive electrode capacity regulation. Cobalt hydroxide is added to improve the high-rate discharge characteristics of the battery, and zinc oxide is added to suppress the structural change of nickel hydroxide into gamma-nickel hydroxide to prolong the service life.

In the present invention, carbon is used as the conductive agent and water glass is used as the binder in the positive electrode in order to improve the high rate discharge characteristics while reducing the amount of cobalt hydroxide.

Even in a paste using water glass as a binder and water, carbon is well dispersed, and a paste obtained by adding nickel hydroxide to this is filled in a nickel current collector and dried, so that the active material is surrounded by the paste. Carbon is firmly fixed. Moreover, once dried, the binder is stable even in alkaline electrolyte, so carbon is not released,
Since the active material is provided with sufficient conductivity, the amount of cobalt hydroxide in the positive electrode can be reduced, the cost can be reduced, and the high rate discharge characteristics can be improved.

In the present invention, when a positive electrode is produced using the above substances, carbon as a conductive agent and water glass as a binder are previously made into a paste by using water, and nickel hydroxide is added to and mixed with the paste. An aqueous paste is filled and dried to form a positive electrode.

It is not preferable to add water glass as a binder to nickel hydroxide and carbon as a conductive agent, and then to make an aqueous paste at once by using water, and to fill and dry this to make a positive electrode. This is because the degree of improvement in high rate discharge characteristics is reduced in the battery using the positive electrode manufactured by this method. It is considered that a part of the surface of nickel hydroxide which is an active material is covered with sodium silicate which is a component of water glass.

On the other hand, in the method of the present invention in which carbon as a conductive agent and water glass as a binder are made into a paste by using water, and nickel hydroxide is added to and mixed with the paste, the binder and the active material are mixed. It is considered that the action is reduced to some extent and good high rate discharge characteristics can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A nickel-hydrogen battery according to an embodiment of the present invention will be described below with reference to the drawings.

The positive electrode was prepared by adding 0.4 g of artificial graphite as a conductive agent to water glass as a binder so that the solid content of sodium silicate was 0.4 g, and further adding water to form a paste. It was Separately, powders of nickel hydroxide, metallic cobalt, cobalt hydroxide, and zinc oxide, which were weighed at a weight ratio of 100: 8: 2: 3, were mixed well. After adding 20 g of the mixed powder to the above paste and kneading the mixture, 60 mm in width, 81 mm in length, and 3.1 g of foamed nickel having a weight of 3.1 g,
After filling this paste and drying at 45 ° C, the thickness is 1.74 m.
It was compressed to m to obtain a positive electrode plate. A nickel plate as a lead was spot-welded to the corner of the positive electrode plate. At this time, the amount of nickel hydroxide on one positive electrode plate was 17.7 g and the theoretical capacity was 5.11.
It is Ah. Five positive electrode plates were used for the test battery.

As the hydrogen storage alloy for the negative electrode, an alloy MmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 containing a misch metal (Mm) with a lanthanum content of 10%, which is an AB ₅ alloy, was used.
Water was added to 19.4 g of this alloy to form a paste. Width 6
This paste was filled in nickel foam having a length of 0 mm, a length of 81 mm, and a weight of 3.1 g, dried, and then compressed to a thickness of 1.20 mm to obtain a negative electrode plate. A nickel plate as a lead was spot-welded to the corner of the negative electrode plate. The theoretical discharge capacity of one negative plate is 5.63 Ah. Six negative plates were used for the test battery.

The battery of this example was arranged such that the negative electrode and the positive electrode were arranged in this order with the negative electrode on the outside through the sulfonation-treated polypropylene nonwoven fabric separator. The negative electrode lead was spot-welded to the nickel negative electrode terminal, and the positive electrode lead was spot-welded to the nickel positive electrode terminal. The thickness of these plates is 3 mm
Made of acrylonitrile-styrene resin and has a vertical dimension of 1
It was put in a case of 08 mm, width 69 mm, and width 18 mm.
An aqueous solution of potassium hydroxide having a specific gravity of 1.3 was used as an electrolyte.
cc was added.

A sealing plate made of acrylonitrile-styrene resin attached with a safety valve operating at 2 atm was adhered to the case with epoxy resin. After that, the positive electrode terminal and the negative electrode terminal were pressed and fixed to the sealing plate via an O-ring to form a sealed battery. The battery of this example is referred to as battery A.

Separately, as a battery of a conventional example, powders of nickel hydroxide, metallic cobalt, cobalt hydroxide, zinc oxide, and metallic cobalt weighed at a weight ratio of 100: 8: 6: 3 were thoroughly mixed, and then 20 g of mixed powder. Was added to form a paste. 60 mm wide and 81 m long, similar to the battery A of this embodiment.
This paste was filled in 3.1 g of nickel foam having a weight of 3.1 g, dried, and then compressed to a thickness of 1.74 mm to obtain a positive electrode plate.
A nickel plate as a lead was spot-welded to the corner of the positive electrode plate. At this time, the theoretical capacity of one positive electrode plate is 4.94 Ah. Similarly, five positive electrode plates were used for the battery. As the negative electrode, the same electrode plate as the battery 5 of the above-mentioned embodiment was used. Thereafter, an active material holder was filled in the same manner as the battery A of this example, and a battery was similarly constructed. This conventional battery is referred to as battery B.

In the battery of the conventional example, the weight ratio of nickel hydroxide of the positive electrode to metallic cobalt, cobalt hydroxide, and zinc oxide is the same as that of the battery A of this embodiment.
The same amount of 0.4 g of artificial graphite and 0.4 g of carboxymethyl cellulose as a binder were added to a paste prepared by adding water, and a positive electrode plate was prepared in the same manner as the battery A of this example, and the same. A battery made using the negative electrode plate is referred to as a battery C. The theoretical capacity per positive electrode plate is 5.11 Ah.

Further, as a comparative example, the weight ratio of nickel hydroxide of the positive electrode to metallic cobalt, cobalt hydroxide and zinc oxide is the same as that of the battery A of this example, and 20 g of this mixed powder is 0.4
g of artificial graphite and water glass as a binder were added so that the solid content of sodium silicate was 0.4 g, and water was added to form a paste at one time. Using this paste, a positive electrode and a battery were formed in the same manner as battery A. The battery of this comparative example is designated as D. The theoretical capacity per positive electrode plate is 5.11
It is Ah.

After sealing these batteries, the rate was 15 at a rate of 10 hours.
Five cycles of initial charging and discharging were performed, in which the battery was charged for an hour and discharged at a rate of 2 hours until the voltage became 1.0V. Then 2 at 20 ℃
A charging / discharging cycle was repeated, in which the battery was charged at a time rate of 3 hours and discharged at the same rate until the terminal voltage became 1V.

The batteries are A, C, D batteries and 12.8A, B.
Was 12.4 A. Table 1 shows the positive electrode utilization rate of each of the above batteries, and FIG. 1 shows the discharge curve.

[0023]

[Table 1]

From these results, it can be seen that the battery A of the present embodiment can obtain similar high rate discharge characteristics as compared with the battery B of the conventional example even if the amount of expensive cobalt hydroxide used is greatly reduced. As shown in FIG. 1, the discharge capacity of the battery A is larger than that of the battery B because the battery A can increase the weight ratio of the active material even if the positive electrode mixture has the same weight.

Further, it can be seen that in the battery C using the positive electrode composed of the conventional paste containing carbon and carboxymethyl cellulose, the discharge characteristics are poor at a high rate discharge.

Further, as compared with Comparative Example D, the production method of the present invention, that is, the method of forming a paste in advance and adding the active material thereto, obtains a good high rate discharge characteristic for the reason described in the section of the action. You can see that.

In this example, acetylene black was effective as the conductive agent carbon added to the positive electrode in addition to artificial graphite. The amount of nickel hydroxide added is 1
1.5 to 10 parts by weight is suitable for 100 parts by weight, and if it is less than this, the high rate discharge characteristics are deteriorated, and if it is more than 100 parts by weight, there is no hindrance to high rate discharge, but the positive electrode activity per weight is high. The decrease in the filling capacity of the substance becomes large. Further, the weight of the binder added at this time was 1.5 to 10 parts by weight in proportion to the amount of carbon.

The types of water glass as a binder were good for both water glass Nos. 1 and 2. In addition, although the example in which the hydrogen storage alloy is used as the negative electrode has been described in the present embodiment, the same effect can be obtained by using gallium or zinc.

[0029]

As is apparent from the above description of the embodiments, according to the present invention, a positive electrode containing nickel hydroxide as an active material is used with carbon as a conductive agent and water glass as a binder. In an alkaline storage battery, the amount of cobalt hydroxide can be significantly reduced, cost can be reduced, and high rate discharge characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing discharge characteristics of a battery A of this example, conventional batteries B and C, and a battery D of a comparative example.

[Explanation of symbols]

 A Battery of the Present Invention B Battery of Conventional Example C Battery of Conventional Example D Battery of Comparative Example

Front page continued (72) Inventor Katsunori Komori 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A reversible negative electrode, a positive electrode containing nickel hydroxide as a main component, and an electrolyte containing an alkaline aqueous solution as a main component, wherein carbon as a conductive agent and water glass as a binder are used for the positive electrode. Alkaline storage battery. 2. A carbon paste as a conductive agent and water glass as a binder are prepared in advance using water to form a paste, and an aqueous paste prepared by adding nickel hydroxide to the paste is mixed into an active material holder and dried. The method for manufacturing an alkaline storage battery according to claim 1, wherein the positive electrode is manufactured by using the above method.