JPS5875768A - Manufacture of pasted electrode for battery - Google Patents

Abstract

PURPOSE:To increase both the utilization rate and the life of a pasted electrode for a battery by fixing a pasty positive material principally consisting of nickel hydroxide over a perforated plate used as a core member, and pressing them until the core member is extended. CONSTITUTION:The symbol 1 represents a core member made of a perforated plate. The symbol 2 represents mixture powder which principally consists of nickel hydroxide 2' used as an active material, contains nickel and a graphite, and contains an additive which enhances the utilization rate and the charge efficiency of nickel, such as cobalt or cobalt oxide, according to necessity. The symbol 3 represents a fiber. When the unextended core member 1 is extended by being moved in the direction indicated by the arrow, the hole 1' of the core member 1 deforms into the hole 1''. Here, such an extremely high pressure that extends the perforated plate 1 should be applied to the core member, since a high characteristic and an increased life similar to those of a sintered electrode cann't be realized only by pressing the core member through rollers. Owing to such press as above, the discharge characteristic and the life of a pasted electrode are improved, and the capacity of the electrode can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing paste-type electrodes, particularly nickel electrodes, for use in alkaline electrodes.

In batteries used as various power sources, in systems that use alkaline aqueous solutions as electrolytes, positive electrodes include nickel electrodes, silver oxide electrodes, manganese dioxide electrodes, air electrodes, etc., and negative electrodes include cadmium electrodes, iron rods, hydrogen electrodes, etc. and so on.

Among positive electrodes, nickel electrodes are the most commonly used because they are particularly stable in alkaline aqueous solutions, have excellent charge/discharge reversibility, can be expected to have a long life, and are also excellent in terms of utilization. ing. In particular, nickel-cadmium batteries have been put into practical use as secondary batteries next to lead batteries, and demand is expected to continue to grow significantly in the future. Further, nickel-zinc batteries and nickel-iron batteries are being developed particularly for use in electric vehicles, and nickel-hydrogen batteries have entered the practical stage for special uses, mainly for space use.

As described above, nickel electrodes are widely used, and the electrode structure used to be a pocket type, but recently the sintered type has become mainstream. As is well known, the pocket type is obtained by mechanically filling a steel container with many holes with nickel hydroxide and a conductive material such as graphite.

Therefore, although the electrode has a robust appearance, the active material exists only in contact with the conductive material and the container (pocket), so polarization during large current discharge is large and the utilization rate is low. Become. In addition, under harsh conditions such as rapid charging, the lifespan will be shortened.

On the other hand, in the sintered type, the active material is firmly attached and embedded in the sintered body with micropores, so there are fewer problems like the pocket type described above, and it is difficult to handle large currents. Significant improvements have been made in terms of discharge characteristics, rapid charging characteristics, and lifespan.

Therefore, it can be said that the sintered type has reached the ideal stage from the viewpoint of characteristics alone. However, the production of sintered bodies,
The process for filling active materials is complicated.
The problem is that it is considerably more expensive than the pocket type. Instead of the sintering method, a method has been developed in which a foamed metal with a large pore size and porosity is used as an active material support and the active material is directly injected into the support, which at least simplifies the process of filling the active material. .

An even simpler method is the so-called paste method, which uses a two-dimensional porous material such as a net, perforated plate, or expanded metal as the core material, and mixes the active material and binder to form a paste. Apply a layer of paint, smooth it by passing it through slits or between rollers, and after drying,
Pressure is applied as necessary. This method is ideal as a manufacturing method because the core material is extremely inexpensive and filling with the active material is easy, and many proposals have been made. Paste-type electrodes have a long history, and although the manufacturing method is slightly different, paste-type lead electrode plates are extremely widely used. Cadmium electrodes have also been put into practical use.

The following are the reasons why nickel electrodes have not been put into practical use despite many proposals.

(1) Nickel, that is, neither nickel oxyhydroxide used as an active material during charging nor nickel hydroxide used during discharge are excellent conductors. Therefore, it is necessary to separately add a conductive material, and even if it is added, it is difficult to improve the utilization rate. Moreover, if too much is added, the absolute capacity will become small.

b) Naturally, the volume of the active material changes due to repeated charging and discharging, but nickel electrodes undergo severe swelling.

The above-mentioned factors mainly prevent the widespread practical application of paste-type nickel electrodes.

In other words, various binders have been considered in the past as a method of first increasing the strength and preventing the swelling as described in (2) and the accompanying shedding of the active material. As a binder, polyethylene, polypropylene, polyvinyl chloride, polystyrene,
Examples include fluorine resins, polyvinyl alcohol, carboxymethyl cellulose, and ethyl cellulose. Of course, the former is superior in terms of electrolyte resistance and oxidation resistance, but if a large amount is added to improve the strength, the voltage characteristics will be inferior and the utilization rate will also decrease. To suppress this, nickel powder, graphite, etc. were added, but if too much was added, the proportion occupied by the active material would decrease, and if too little was added, the utilization rate would be low.

On the other hand, as a binder, polyethylene, polyethylene,
For polystyrene, etc., either a method of adding it to nickel hydroxide in the form of a solution or a method of adding it in the form of a powder and then heating and melting it is adopted. Regarding fluororesin, there are two methods: adding it in powder form and adding it in the form of a dispersion. In addition, in the case of disno and rubber products, when this is added to nickel hydroxide and mixed, the fluororesin becomes fibrous, and the whole material has rubber-like elasticity and strength. There is also.

The addition of binders described below and other electrolyte-resistant fibers can improve the properties and life of paste-type or pressurized nickel electrodes, so-called non-sintered nickel electrodes, to some extent, but conventional It is far inferior to the sintered type, so it has not been widely used in practice.

The present invention provides an excellent manufacturing method that brings the discharge characteristics and lifespan closer to those of the sintering method while retaining the advantage of the paste method in that it can be manufactured easily. That is, in the present invention, a paste positive electrode material mainly composed of nickel hydroxide is attached to a perforated plate as a core material, and a forming process and a pressurizing process are performed by passing it between rollers. It is characterized by applying pressure until it is stretched.

FIG. 1 schematically shows an electrode according to the invention.

1 is a core material made of a perforated plate. 2 is a powder mainly containing an active material, that is, nickel hydroxide 2', which contains nickel, graphite, and, if necessary, additives such as cobalt and cobalt oxide to improve the utilization rate and charging efficiency of nickel. 3 is fiber.

FIG. 2 shows the core material before stretching. When the core material is moved in the direction of the arrow and stretched, the holes 1' in the core material become as shown in 1v).

Conventionally, the most common method of applying pressure is to pass it between rollers. However, by simply applying pressure through the two rows, it was not possible to obtain properties and lifespan close to those of the sintered electrode. Therefore, this pressure is applied to the extreme 11 so that the perforated plate serving as the core material is stretched.

This pressurization improved discharge characteristics and lifespan, and also made it possible to increase capacity. In addition, in the case of this stretching, it is preferable to use a commonly used perforated plate, for example, one with a thickness of about 0.5 to 1.5 and a porosity of 40 to 60, and the stretching ratio is preferably 4 to 15%. I understand.

Next, the present invention will be explained by examples.

A AA size sealed nickel-cadmium storage battery was used as a battery for performance comparison. The cadmium negative electrode manufactured as follows was used. First, a paste mainly composed of cadmium oxide is applied to both sides of a perforated iron metal, passed through a slit set to a predetermined thickness, and then subjected to a drying process to achieve the desired thickness.

, 7wrI electrode plates were obtained. Thereafter, it was partially charged in an aqueous solution of 10% by weight of caustic potassium to convert a part of the dmium oxide into metal cadmium, and after washing with water and drying, it was pressurized to a thickness of 0.665 mm.

A polyamide nonwoven fabric was used as the separator, and 6.3 cc of a small amount of lithium hydroxide dissolved in a 25% by weight aqueous solution of caustic potash was used as the electrolyte per cell.

The paste for forming the nickel positive electrode is 200 mets/
- to nickel hydroxide of a particle size that passes through a sieve,
Carbonyl nickel 100F, graphite 40p and diameter 0.1
A 3-weight polyaqueous solution of acrylonitrile-vinyl chloride copolymer fiber 2011 with a length of 3 to 5+ m* and metal cobalt 60y1 carboxymethylcellulose was added to the above mixed powder by 1 part to 9 parts and kneaded together. The core material is a 0.1-thick iron plate with a hole diameter of 2 and a center-to-center pitch of 3.
A punched metal with rm holes and nickel plating was used. The above paste is applied to both sides of this core material, passed through a slit, and the thickness after drying is 1.0
It was set to ±0.06 mm. Then 200% of cobalt acetate
f/R, immersed in an aqueous solution, dried, immersed in an aqueous solution of caustic potash, and added cobalt hydroxide by a method of converting cobalt acetate into cobalt hydroxide. These placing plates were first cut into a width of 120 meters and a length of 680 m+n. Then, pressure was applied between the rollers and the material was stretched to 4 inches in the length direction. The thickness of the electrode was 0.7III11. This electrode was further cut into two pieces. In this case the width is 3
I made the length 220 torso with 8+a+. A battery was constructed by combining this with a cadmium electrode and a polyamide nonwoven fabric as a separator. This battery is called A. Then, pressure was applied until it was stretched by 8% in the length direction. The thickness of the electrode is 0.66
It was m. Similarly, in this case, the length is 1 longer than A, making it 230. This battery is called B. Further pressure was applied until the film was stretched by 12%. What is the thickness? , 61 layers. In this case, the length was 240 vans.

This is called battery C. Finally, pressure was applied until it was stretched by 15 inches. The thickness was 0.57m+. This used a length of 265 pieces. Recharge the battery.

For comparison with these batteries A-D, batteries A' to D' were added in which the thickness and length of the electrodes were the same as those of A-D, respectively, and the batteries were pressurized to the extent that they did not stretch. The following table shows the charging capacity of each battery, the utilization rate at each discharge time, and the button charging time.
, 1sc, discharge is. , 3C, and the cycle life is defined as the life when the capacity decreases to 60% of the initial capacity.

As is clear from this table, applying pressure until the electrode is stretched does not damage the electrode, but improves both the utilization rate and the lifespan.

As described above, in the manufacturing method of paste-type electrodes for batteries,
By using a perforated plate, which is stronger than a screen or expanded metal, as the porous conductor and applying pressure with a roller to the extent that it is stretched, it is possible to improve the utilization rate and life of the electrode.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross section of an electrode according to the present invention, FIG. 2 is a plan view of the perforated plate before stretching, and FIG. 3 is a plan view after stretching. 1...Perforated plate, 1', 1"...hole, 2...
... Powder mainly consisting of active material, 3... Fiber.

Claims (1)

[Claims] 0) A paste mainly consisting of an active material is attached to a conductive porous body made of a perforated plate, the paste coating layer is smoothed through a slit, and the conductive porous body is stretched between rollers. A method for manufacturing paste-type electrodes for batteries, which is characterized by pressurizing up to 100%. (2) The thickness of the conductive porous body is 0.09 to 0.12 mm,
The method for producing a paste-type electrode for a battery according to claim 1, wherein the porosity is 60 to 60 inches. (3) The method for manufacturing a battery paste electrode according to claim 1, wherein the stretching ratio of the conductive porous body is 4 to 16%.