JPS5951464A - Production method of positive electrode for alkaline cell - Google Patents

Abstract

PURPOSE:To improve the strength of an electrode by adding cobalt to active material mixed powder when coating a support body made of a porous steel plate, etc. with mixed powder mainly composed of nickel hydroxide to form a positive electrode. CONSTITUTION:Cobalt powder is added to the mixed powder of nickel hydroxide powder and nickel powder serving as a conductive material, and it is made into a paste status by use of a carboxymethyl-cellulose aqueous solution, then polytetrafluoroethylene powder is added to make it into a clay status. It is coated on both faces of a nickel net serving as a core material, which is then molded by pressure to form a positive electrode for an alkaline cell. Accordingly, cobalt improves the binding feature between grains of nickel hydroxide powder and between grains and a support body when cobalt is oxidized to generate cobalt hydroxide or cobalt oxyhydroxide during charging, thereby the strength of the electrode is increased and the discharge performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temporary manufacturing method in which a mixed powder containing nickel hydroxide as a living body is applied to an active material support such as a porous steel plate. By adding
The purpose is to obtain a total of 111N.

Alkaline battery IE! The 11m method of the 1ili religion is:
This method is usually called the reduced field impregnation method.
A method is used in which L4tliF is impregnated with IIIE, treated with an alkaline aqueous solution, and then washed with hot water and dried, which are repeated. However, the amount of active material filled in one operation is small, and the amount filled gradually decreases from the second operation onwards, so it is usually necessary to repeat the operation 4 to 10 times. The drawback is that the process for manufacturing T rice is complicated and the economic cost is high. Also,
Since the porosity of the substrate was about 80%, the energy efficiency was low and disadvantageous.

Therefore, in recent years, attention has been paid to a method in which a sponge-like porous body made of nickel metal having a three-dimensionally continuous structure is directly filled with a positive active material in the form of a paste.

A porous nickel porous material having a three-dimensional continuous structure has a high porosity of 90 to 98% and high mechanical strength. Moreover, since the pore diameter is large, filling this porous body with active material IJ5 makes it possible to increase the mt of the positive plate, and the filling method is simple, allowing a continuous process, which is economically advantageous. However, if the pore diameter of the sponge-like porous nickel material is too large, sufficient electrical bonding properties between the porous nickel material as a current collector and the active material powder and between the active material particles may not be obtained. However, if the pore diameter of the porous body is too small, it will take a long time to fill the active material.

Another drawback is that the sponge-like porous nickel material is expensive.

Therefore, a method can be considered in which the active material is applied in the form of a paste to both sides of a support such as a porous steel plate.

In this case, the manufacturing process is extremely simple and economically advantageous, and the energy efficiency is also extremely high, but on the other hand, the active material tends to fall off easily, and in some cases, the active material may peel off from the support. It has the disadvantage of being This is thought to be due to the fact that the binder in the paste alone does not provide sufficient binding force between the active material particles.

To solve this drawback, apply an active material to the T.
Attempts have been made to increase the binding force by immersing the adhesive in an aqueous binder solution, but this has not been found to be sufficiently effective.

The invention is based on the discovery that when cobalt is added to the active material, the strength of FHVI and the binding force of the active material are increased, the peeling of the active material is greatly reduced, and the discharge performance is significantly improved. It is something.

Examples of the present invention and its effects will be described in detail below. The formal mask according to the present invention was manufactured as follows. First, cobalt powder was added to a mixed powder of 80 parts of nickel hydroxide powder and 20 parts of nickel powder as a conductive material, and one powder was made into a paste with 0.61 J carboxymethylcellulose aqueous solution. Further, polytetrafluoroethylene powder was added to this paste in an amount of 4% based on the total active material to form a clay-like material. This clay-like active material was applied to both sides of a 20-mesh nickel net with a wire diameter of 0.2 m to a thickness of about 11111 mm.
It was dried at ℃ for 1 hour and then pressure-molded to a thickness of 0.68 ℃ and 1 ml to obtain a porcelain board. One of this positive plate, two sintered cadmium negative VU temporary plates, and 8.0.1.250 (20'C) potassium hydroxide water solution as electrolyte.
A flattened type battery was made using 11g of liquid and charged at 0.1OA for 16 hours.
Discharge the mercuric oxide electrode to 1 Ov to find the active material utilization rate.

FIG. 1 shows the relationship between the amount of cobalt added and the active material utilization rate. It can be seen from the figure that significant effects can be obtained when the amount of cobalt added is 5% or more.

In cases c and 2, the strength of the negative plate increased as the cobalt charge increased. In addition, in the case of the Jeongmyo board that did not contain cobalt, the active material was peeled off from the support at the end of the photovoltaic period, so that discharge could not be performed.

Next, one positive PII temporary sheet according to the present invention and one conventionally known paste-type cadmium negative temporary sheet were manufactured with the amount of cobalt added at 10%, and were spirally wound through a nylon nonwoven fabric separator, and electrolyzed. 8. into the liquid. G.

A sealed nickel-cadmium battery according to the present invention with a nominal W12.5AhO was fabricated using a 1.800 (20"C) potassium hydroxide aqueous solution.
5 - Manufacture a battery IBI using a conventional method using a positive plate that does not contain balt. These batteries are 0. 16 in IOA
Figure 2 shows the discharge characteristics when the time-based photoelectric γ is discharged to t, OV with l, QCA. From the figure, it can be seen that the battery according to the present invention (41 is a battery manufactured by a conventional method (IJ) has significantly improved discharge performance.

FIG. 8 shows the change in the range of discharge capacity when 20 batteries of the same type were manufactured and repeated charging and discharging cycles under the same conditions as above. From the figure, the electrode according to the present invention
It can be seen that it is also excellent in terms of life performance.

Why does adding cobalt improve temporary strength?
Although it is not certain whether the I-plate performance improves, it is thought that this is due to the following reasons. In other words, the conventional positive plate uses only fine powder of fluororesin added to a paste-like active material to obtain binding strength between the active material particles and between the active material and the support, so that the active material swells during charging. The active material easily falls off due to the generation of gas and, in the worst case, peels off from the support. However, when cobalt is added to the active substance and cobalt according to the present invention is oxidized during charging and cobalt hydroxide or cobalt oxyhydroxide is produced, it becomes oxidized. It is believed that the strength is improved by improving the bonding properties between the particles of the nickel powder and between the particles and the support.

As stated above, the present invention improves the temporary strength of a self-contained plate produced by adhering the active material to a support such as a porous steel plate by adding the active material fζ cobalt, and discharges It can significantly improve performance.

4. Drawings) @ m r, r Explanation The first appendix shows the relationship between the amount of cobalt added and the active material utilization rate. FIG. 2 is a comparison diagram of 1OA discharge characteristics of batteries according to the method and a comparison diagram of changes in the range of the amount of tg released with charge/discharge cycles.

A... Battery according to the present invention, B... Conventional method 7- lol 1 concave ρ 5 to /
A 2゜Kobelt Expansion-! (%) Bowl Z Figure θ /, Oz, Q Capacity (Ah)

Claims (1)

[Claims] Nickel hydroxide powder as an active material, nickel powder as a conductive material, and polytetrafluoroethylene powder and cobalt powder as a binder are mixed, and a paste such as a carboxymethylcellulose aqueous solution is added to the mixed powder to form a paste. 1. A method for producing a 1ETo plate for an alkaline battery, which is characterized in that it is coated on a conductive support such as a porous steel plate or a wire mesh, and then dried.