JPS612272A - Positive plate for sealed cylindrical nickel-cadmium battery - Google Patents

Abstract

PURPOSE:To increase active material utilization of a nonsintered nickel positive plate by containing nickel flakes in an active material mainly comprising nickel hydroxide. CONSTITUTION:5-25wt% of nickel flakes to the total active material are contained in an active material mainly comprising nickel hydroxide powder. Thereby, active material utilization of a paste type positive plate is increased to a similar level to that of a sintered positive plate. Therefore, the capacity of nickel positive plate is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positive electrode plate for a cylindrical sealed nickel-cadmium storage battery.

Conventional Structures and Problems Conventionally, there are two types of positive electrode plates for sealed cylindrical nickel-cadmium storage batteries, which are roughly classified based on the manufacturing process. One of them is the so-called sintering method,
A slurry of nickel powder is deposited on a fully conductive core material, sintered to form a porous substrate, and the micropores are filled with nickel hydroxide chemically, electrochemically, or using both. This is a method of converting it into an active material and using it as a positive electrode. In the case of this type of positive electrode, since the substrate as a conductor ultimately occupies a large volume in the entire positive electrode plate, it has the advantage of high utilization of the active material that has entered the micropores of the substrate. It has the disadvantage that the amount of active material that can be filled in is limited. t
i. In order to maintain the uniformity of the positive electrode plate required in battery design, complicated quality control is required in manufacturing.

The other method is a manufacturing method called a non-sintering method or a paste method. Unlike the method of filling the active material in the case of the sintering method, which uses an aqueous solution of nickel salt such as nickel nitrate, this method uses nickel hydroxide, which is the final active material, directly and conductively by physical means. This is a method of holding it on a solid substrate.

In other words, an active material mainly composed of nickel hydroxide is directly kneaded with water or other solvent to form a paste, and then applied to a conductive core material or placed in a porous metal foam having a three-dimensional structure. In this method, the positive electrode plate is prepared by filling the molten metal into the molten metal. According to this manufacturing method, there is no substrate that occupies a large volume as seen in the sintering method, so the amount of active material can be increased with the same plate volume, increasing the absolute plate capacity. can be done.

In addition, it saves money on conductive substrates that require precision in the manufacturing process, and
Since the filling method is simple, it also has a great advantage in terms of cost. However, as seen in the sintered type, there is a drawback that the utilization rate of the active material is significantly lower than that of the sintered type because there is no conductive substrate around the active material.

Therefore, in order to improve the utilization rate, conductive materials such as nickel powder and cobalt powder and substances considered to be electrochemical catalysts have been added to the active material paste mainly consisting of nickel hydroxide. The conductive network is insufficient, and the utilization rate is still inferior to the sintered type, resulting in the problem that the paste type's advantage of high capacity cannot be fully utilized.

OBJECTS OF THE INVENTION The object of the present invention is to provide a paste-type positive electrode plate that solves the problems of the conventional example described above and has a high utilization rate.

Structure of the Invention In order to achieve the above-mentioned object, the present invention is a nickel positive electrode plate containing nickel flakes in a half-shaded shape in an active material mainly composed of nickel hydroxide powder, preferably with respect to the whole material. This is a non-sintered nickel positive electrode plate characterized by containing 5 to 25% by weight of nickel flakes.

This positive electrode plate improves the active material utilization rate as a paste type positive electrode plate to the same level as that of a sintered type positive electrode plate, and as a result, it is possible to increase the capacity of the nickel positive electrode.

Hereinafter, practical examples of the present invention will be explained.

Description of actual sister example A part of 80M-N nickel hydroxide powder with an average particle size of about 70 μm, 5 parts by weight of carbonyl nickel powder with an average particle size of 3 μm, 6 parts by weight of carbonyl cobalt powder with an average particle size of 6 μm, and a planar Average diameter 25 μm.

Water is added to a powder mixture with 10 parts by weight of scale-shaped nickel flakes having a thickness of 0.8 μm to prepare a paste foreshadowing hardware having a water content of 25 parts by weight. This n' is filled into a foamed nickel porous body having a three-dimensional structure, and after drying, it is pressure-molded to a thickness of 0.7 mm. This product was immersed in an aqueous suspension of 7 base resins with a solid content concentration of about 2 seconds and then dried to give a width of 39 mm.
aM, the positive electrode plate was obtained by cutting into length 68 ends. At the same time, a conventional nickel positive electrode plate was obtained by replacing all 10 parts by weight of the scale-shaped nickel flakes with carbonyl nickel powder as the composition of the mixed powder in the above example, so that the total amount of carbonyl nickel was 16 parts by weight.

The actual sister example and the conventional positive electrode plate were combined with a known paste-type cadmium negative electrode plate with a nylon nonwoven fabric sandwiched between them.
Wind it up in the opposite direction, and use it as an electrolyte with a ratio of M1.5oKO.
Aqueous H solution was injected to assemble 12 KR-AA size batteries, and their positive electrode utilization rates were measured. In addition, battery capacity plate] As a constant condition, 60℃ in a 20C atmosphere
After charging for 15 hours with a current of mA, 1 in the same 20C atmosphere.
Battery voltage 1. at 20mA. The discharge capacity was calculated based on the discharge time when discharging at OV4.

The results are shown in FIG. In FIG. 1, a shows a discharge curve of a real-life example in which strip-shaped nickel flakes are included in the active material paste, and a discharge curve of a conventional method that does not contain nickel flakes.

It can be seen that the utilization rate is higher when nickel flakes are included. This was also observed in electrode plates obtained by applying paste on the core material. Possible causes of this are that the flaky nickel pieces are dispersed in the active material in an amorphous order without any directionality, and come into contact with the foam metal substrate as a surface or wire, or the flakes may come into contact with the foam metal substrate. This is because the electrical conductivity can be maintained sufficiently by contacting each other, and as in the case of carbonyl nitride powder alone, the electrical conductivity can only be increased by point contact, and nickel hydroxide Compared to the case where nickel is incorporated into the powder and cannot maintain contact with other nickel powder, the utilization rate is greatly improved. Furthermore, when nickel flakes and carbonyl nickel powder are mixed at the same time, the nickel flakes become the main conductive skeleton, and the carbonyl nickel powder, which has a small particle size, acts as a bridge between the details, creating a network between the two conductive materials. The utilization rate will further improve. The appropriate amount of nickel flakes is 5 to 25% by weight of the total active material, and as shown in FIG. 2, when the amount of nickel flakes is less than 6% by weight, no significant improvement in utilization rate is observed. On the contrary, 25
If the weight ratio is exceeded, the utilization rate increases, but the increase in volume causes the problem of lowering the actual volume N'fr of the electrode plate.

Further, unless the size of the nickel flakes is larger than the carbonyl nickel powder, the effect cannot be expected at fL. That is, the effect appears when the planar average diameter is 10 μm or more, but when it is 5 μm or more, it is too thick, resulting in poor dispersion in the electrode plate and also causing short circuits. Regarding the thickness, when the thickness is 0.5 μm or less, the conductivity deteriorates and there is no effect, and when the thickness is 5.0 μm or more, the volumetric loss becomes more of a problem.

Effects of the invention As described above, the non-sintered nickel positive electrode plate containing scale-shaped nickel flakes in the active material mainly composed of nickel hydroxide has a significantly improved active material utilization rate, and is superior to the sintered type. It is possible to obtain the same utilization rate, and it is also possible to increase the capacity of batteries.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the discharge capacity of a positive electrode plate obtained by an actual winding example of the present invention, and FIG. 2 is a diagram showing the relationship between the content of nickel flakes in the active material and the active material utilization rate. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) A positive electrode plate for a sealed cylindrical nickel-cadmium storage battery, characterized in that an active material mainly composed of nickel hydroxide contains nickel flakes having a scale shape. (2) The positive electrode plate for a sealed cylindrical nickel-cadmium storage battery according to claim 1, wherein the scale-shaped nickel flakes are added in an amount of 5 to 30% by weight based on the total amount of active material. (3) The size of the nickel flakes is a planar average diameter of 1
The cylindrical sealed nickel according to claim 1 or 2, which has a thickness of 0 to 50 μm and a thickness of 0.5 to 5.0 μm.
Positive electrode plate for cadmium storage batteries.