JPH03201366A - Manufacture of paste type electrode - Google Patents

Abstract

PURPOSE:To prevent a paste from being drawn during pressing process and also obtain a paste type electrode of high capacity by carrying out pressure molding of the paste in such a manner that when passed between rollers for the first time the paste is pressed to predetermined final thickness by a specific roller press. CONSTITUTION:Nickel hydroxide is used as active material and nickel powder and carboxymethyl cellulose serving as a thickener are added thereto in respective predetermined amounts and pure water is further added thereto and mixed to form a paste. The paste is packed in a nickel sintered fiber base and after drying the base is passed between two upper and lower rollers once by a two- stage roller press 100mm in diameter and having the upper and lower rollers and is pressed to predetermined final thickness 0.6mm to obtain a nickel electrode. Preferably, the diameter of each roller is 100 to 300mm. Thereby the paste is prevented from being drawn during pressing and also a paste type electrode of high capacity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement in a method for manufacturing a paste-type electrode used in an electric ground.

(Prior art and its issues a) Up until now, sintered electrodes have been mainly used as electrodes for alkaline storage batteries, typified by nickel-cadmium storage batteries. This is because sintered electrodes have a long life and excellent high rate discharge performance. However, the manufacturing method of sintered electrodes is complicated and time-consuming, and has a limit to high capacity.As an alternative method, a paste-like active material is directly applied to a conductive porous substrate with a three-dimensional structure. A paste-type electrode for filling was developed. The manufacturing method of this paste type electrode is simple and can provide an electrode with high capacity.

A common filling method is to add additives, thickeners, binders, etc. to the main active material to form a paste, and then fill the paste. It is then dried, pressed to a predetermined final thickness, and molded into a finished electrode. Generally speaking, a roller press, which is excellent in mass production, is used to press the material, and the material is pressed several times to a predetermined final thickness. However, since the three-dimensional substrate filled with this method is stretched, there is a certain -
In addition to not achieving a packing density higher than a certain value, the tensile strength is weak unlike bunched metal having a two-dimensional structure, and there is a problem that the substrate is likely to break and meander due to stretching.

The present invention has been made to solve the above problems,
The purpose is to prevent stretching during the pressing process and provide a paste-type electrode with high capacity.

[Structure of the Invention] (Means for Solving the Problems) The present invention involves filling a conductive porous substrate having a three-dimensional structure with a paste-like substance containing an active material, drying it, and then pressing the filled substrate with a roller. In this case, the above-mentioned problem is solved by setting the roll diameter of the roller press to 100+++s or more and pressing the film to a predetermined final thickness with one roller application.

Examples of the conductive porous substrate having the three-dimensional structure include foamed metal, sintered nickel fiber substrate, metal-plated fiber substrate, and the like.

The paste is made of a positive electrode active material such as nickel hydroxide, a thickener binder such as carboxymethylcellulose (CMC), methylcellulose, sodium polyacrylate, or polytetrafluoroethylene, and a solvent such as water. and a negative electrode paste consisting of a negative electrode active material such as cadmium oxide, a thickener such as polyvinyl alcohol, and a solvent such as ethylene glycol.

The reason why the diameter of the roller is set to 100 + lIm or more is that if it is less than 100 mm, not only will it not be possible to suppress the stretching sufficiently, but the filled substrate will not be caught, and the roller will stop.
This is because it may spin idly or, in some cases, the filled substrate may become torn into pieces.

The reason why it is pressed to the final thickness in one step is that if it is pressed multiple times, the capacity density will not exceed a certain window, and it will not be able to handle batteries that require high capacity.

(Function) In the present invention, if a roller press with a diameter of 100 am or more is used and a predetermined final thickness is achieved with one roller application,
A high-capacity electrode can be obtained while suppressing stretching that causes meandering and breakage. Furthermore, by suppressing stretching, curvature and meandering of the pressed three-dimensional substrate are suppressed, leading to prevention of adverse effects on subsequent processes and improvement of yield in the pressing process.

In addition, only one roller press device is required, and the complicated control between roller presses required when two or more roller presses are connected is not required, leading to a simplification of the manufacturing process.

However, the diameter of the roller is preferably 300 mm or less.

This is because if it is larger than 300 mm, the resistance during compression will be large, so that the portion that does not extend in the length direction will extend in the lateral direction, and there is a risk that it will break.

(Example) Examples of the present invention will be described in detail below.

Example 1 Nickel hydroxide was used as an active material, predetermined amounts of nickel powder as a conductive material and carboxymethyl cellulose as a thickener were added thereto, and pure water was added and mixed to prepare a paste. Next, add this paste to 6
It is filled into a nickel sintered fiber substrate measuring 0 mm x 300 mm x 1.5 mm, and after drying, it is passed through once between two upper and lower rollers using a two-stage roller press machine with a diameter of 100 mm and having upper and lower rollers. A nickel electrode was obtained by pressing to a final thickness of 0.6 mm.

Example 2 A nickel electrode was obtained in the same manner as in Example 1, except that a two-stage roller press device with a diameter of 200 mm was used.

Example 3 A nickel electrode was obtained in the same manner as in Example 1, except that a two-stage roller press device with a diameter of 300 mm was used.

Reference example except that a two-stage roller press device with a diameter of 90 mm was used.
A nickel electrode was obtained in the same manner as in Example 1.

Comparative Examples 1 to 4 Filled substrates were manufactured in the same manner as Examples 1 to 3 and the reference example, and were pressed to a predetermined final thickness of 0.6 mm by two roller runs using each two-stage roller press device. , a nickel electrode was obtained.

Examples 1 to 3 of the present invention and the reference example (A
) and Comparative Examples 1 to 4 (B) which were pressed twice, the filling capacity density and elongation rate were measured, and the results shown in FIG. 1 were obtained.

From Figure 1, for a roller with a diameter of 90 mm, it is 500+aAh.
The capacitance density is approximately 100 mAh/cc or more, but a capacitance density of 500 mAh/cc or more can be obtained with a diameter of 100 mm or more. Furthermore, the elongation rate was 117% or less for rollers with a diameter of 100 mm or more, and there was no breakage due to meandering or stretching. Furthermore, for a roller with a diameter of 90 mm,
There were cases where the roller stopped without being bitten, but 10
There was no such phenomenon at all when the distance was 0 mm or more.

In addition, in the case of electric drawing in which a predetermined final thickness was obtained by pressing twice, the elongation rate was extremely large and the filling capacity density was also low. Furthermore, when pressing three or more times, the substrate could not withstand the stretching and sometimes broke.

[Effects of the Invention] As detailed above, according to the present invention, there is less stretching during roller pressing of a paste-filled substrate, meandering can be prevented, and a predetermined paste can be filled with a high volume and melon density. A method for manufacturing a highly reliable and high capacity paste-type electrode can be provided.

[Brief explanation of drawings]

Figure 1 shows the filling capacity density of the paste and the nickel electrode after pressing for each nickel electrode of Examples 1 to 3 of the present invention, Reference Example (A), and Comparative Examples 1 to 4 (B) pressed twice. It is a characteristic diagram showing the relationship with elongation rate.

Claims (1)

[Claims] In a method for producing a paste-type electrode in which a three-dimensional conductive porous substrate is filled with a paste-like material containing an active material and then pressure-formed, the pressure-forming is performed by one roller press with a diameter of 100 mm or more. A method for manufacturing a paste-type electrode, characterized by pressing the electrode to a predetermined final thickness.