JPS61203559A - Manufacture of alkaline storage battery - Google Patents

Abstract

PURPOSE:To prevent any scattering of an active material powder by treating the surface of a pasted cadmium electrode containing cadmium oxide as the main active material with an aqueous solution of a water-soluble macromolecular compound to form a thin layer of the compound on the surface. CONSTITUTION:After an active material powder principally composed of cadmium oxide is mixed with a dispersion medium such as aqueous PVA solution and a binder such as polyethylene to prepare a paste, the paste is applied to a core material. After that, an aqueous solution of a water-soluble macromolecular compound such as carboxymethylcellulose with a concentration of 0.5-1.5wt% is applied to the surface of the paste-coated material before drying the thus formed body, thereby making a cadmium electrode for an alkaline storage battery such as a nickel cadmium storage battery. Since the surface of the electrode is covered by a thin film of the water-soluble macromolecular compound, the electrode has increased mechanical strength and any scattering of the active material powder is prevented. Therefore, it is possible to improve the environment of manufacturing without influencing battery performance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing alkaline storage batteries such as nickel-cadmium storage batteries, and is particularly characterized by forming a thin layer of water-soluble polymer on the surface of a nickel-cadmium electrode. The present invention relates to a method of manufacturing an alkaline storage battery.

Problems to be Solved by the Prior Art and the Invention Cadmium negative electrode plates used in alkaline storage batteries generally include a sintered electrode plate in which a porous substrate made of sintered carbonyl nickel powder is impregnated with an active material. Cadmium oxide, nickel powder, thickener, resin.

There is a paste-type electrode plate in which a dispersion medium is added to a mixture of fibers, etc. to form a paste having an appropriate viscosity, and this is coated on a conductive core. In general, paste-type electrode plates require fewer manufacturing steps and are therefore cheaper than sintered-type electrode plates.
On the other hand, there were problems in that the mechanical strength of the electrode plate was weak, the active material powder was easily scattered, and - the working environment was poor during electrode plate manufacture and battery assembly.

Means to Solve the Problem When manufacturing alkaline storage batteries, the surface of a paste-type cadmium electrode whose main active material is cadmium oxide is treated with an aqueous solution of a water-soluble polymer to form a thin layer of water-soluble polymer on the surface. It is characterized by forming.

The cadmium electrode is manufactured by a conventional method before the surface of the electrode plate is treated with an aqueous solution of a water-soluble polymer to form an i1 layer of a water-soluble polymer on the surface. For example, an active material powder containing cadmium oxide as a main component and metal cadmium or nickel powder is mixed with a dispersion medium such as a PVA aqueous solution and a binder such as polyethylene or fiber, and then water is added to form a paste. This was applied to a current collector core made of gold film (for example, a porous steel plate plated with nickel) and dried to produce a cadmium electrode.

Next, the cadmium electrode prepared above is manufactured by treating it with an aqueous solution of a water-soluble polymer and drying it.

Methods for treating the surface of a cadmium electrode with an aqueous solution of a water-soluble polymer include coating with a brush, coating with a roller, or spraying in the form of a mist, which can uniformly apply an aqueous solution of a water-soluble polymer to the surface of the cadmium electrode. Any method is fine.

CMC, MC, or PvA are used as water-soluble polymers, and each of these has different characteristics.

In other words, compared to MC and PVA, CMC dissolves in the form of strings of molecular chains, so the strength of the i1 layer at the same -m degree is weak and a relatively large amount must be added, but CMC is ionic. Therefore, it is easily dissolved in the electrolyte and does not hinder the diffusion of the electrolyte and oxygen gas, so it has a high ratio /i5[? t
It does not adversely affect battery performance such as gas absorption performance.

MO' for this? 1PVA dissolves with the molecular chain fully extended compared to CMC, so the strength of the thin layer at the same concentration is strong and the amount added can be relatively small.
PVA- and PVA- are non-ionic and stable in the electrolyte, but by reducing the amount added, there is less interference with the diffusion of the electrolyte and oxygen gas, improving high rate discharge and gas absorption performance. Does not adversely affect battery performance.

The concentration of such an aqueous solution of water-soluble polymer is 0.5 to 1.
A concentration of up to 5 wt% is used, and concentrations below this range are not preferred because the resulting thin layer of water-soluble polymer tends to be weak and easily peel off.

On the other hand, if ζ exceeds the above range, the water-soluble polymer layer formed on the electrode surface becomes thick, which adversely affects battery performance such as gas absorption performance and high rate discharge performance.

Appropriate types and concentrations of water-soluble polymers applied to the electrode surface vary depending on the type of electrode, but for the reasons mentioned above, it is important that the water-soluble polymer um is strong and does not adversely affect battery performance. Those that are not available are selected as appropriate.

Function: Since the surface of the electrode obtained according to the method of the present invention is covered with a thin layer of water-soluble polymer, the mechanical strength of the electrode plate is strong, and the scattering of the active material powder is almost completely suppressed. This is completely prevented, and the working environment during electrode plate manufacturing and battery assembly is significantly improved. Furthermore, by appropriately selecting the type and degree of water-soluble polymer, battery performance such as high rate discharge and gas absorption performance will not be adversely affected.

Example (a) Production of cadmium negative electrode plate Active material powder consisting of 100 parts by weight of cadmium oxide powder, 10 parts by weight of metal cadmium powder and 7 parts by weight of nickel powder, 0.5 part by weight of potassium citrate, part by weight of MC011, 1.11 parts of single meter nylon fibers were added and thoroughly mixed, and then 30 parts by weight of water was added to form a paste. This paste was applied to a current collector core made of nickel-plated porous steel plate and dried to form a paste-type cadmium electrode (60G++n
x300im x 0.7m+Ilt) was manufactured.

On the surface of the obtained paste-type cadmium electrode,
0. 0,5. 1,0. 1.5. After applying a 2.0 wt% CMC aqueous solution uniformly with an O-ra and drying it,
A cadmium negative electrode plate was manufactured by cutting it into predetermined dimensions.

(b) Production of nickel-cadmium storage battery Each cadmium negative electrode plate produced as described above is combined with a nickel positive electrode plate cut to a predetermined size, and wound into a spiral shape through a separator to form a nickel-plated cylinder. Insert it into a can, pour potassium hydroxide with a ratio of 1.25 m as an electrolyte, attach a pressure gauge to the top, and make the volume 11.
A sealed cylindrical nickel-cadmium storage battery of 1800 mAh was fabricated.

(c) Comparison of properties The results of the scattering state of active material powder during cutting of the cadmium negative electrode plate produced as described above and during battery assembly are shown in the table.

As shown in the table above, by selecting the concentration of the CMC aqueous solution to be at least 0.swt%, it is possible to completely prevent the active material powder from scattering during electrode plate manufacture and battery assembly.

Next, each storage battery produced as described above was heated at 20°C.
After charging at 0.1C for 16 hours and discharging to 0.8V/cell at 0.2C in an atmosphere of
, , 0.2C, 0.50C, the internal pressure of the battery was read at the end of charging when the battery was charged to 160% at each current, and the gas absorption performance was investigated. The results are shown in Figure 1. In the figure, characteristic A uses a conventional cadmium negative electrode plate that has not been treated with a CMC aqueous solution, and characteristics B, C, D, and E are obtained by changing the concentration of the CMC aqueous solution to o, swt%, and 1.0w, respectively.
t%, 1.5wt%, and 2.0wt% cadmium negative electrode plates were used.

As is clear from this figure, the higher the concentration of the CMC aqueous solution, especially 2 wt%, the worse the gas absorption performance becomes.

Furthermore, if the a degree of the CMC aqueous solution is low, the strength of the thin layer on the surface of the cadmium negative electrode will be low, and the scattering of the active material powder will be large.

In this way, when the concentration of the CMC aqueous solution is high, the strength of the thin layer on the surface of the cadmium negative electrode is high, but the diffusion of gas and electrolyte becomes poor, and the gas absorption performance decreases. is 0, SV t%~1.
5 wt% is preferred.

Effects of the Invention As described above, in the present invention, since the surface of the cadmium electrode is covered with a thin layer of water-soluble polymer, the mechanical strength of the electrode plate is increased, the scattering of the active material powder is completely prevented, and the electrode plate is The working environment during manufacturing and battery assembly is significantly improved. Also,
By appropriately selecting the type and concentration of the water-soluble polymer, battery performance such as rate discharge and gas absorption performance will not be adversely affected.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the internal pressure characteristics in the storage battery when the CMC aqueous solution is varied by 11 degrees. Δ...Conventional product, 8~E...Invention product') r 1
Circular electric ring ((:A)

Claims (1)

[Claims] 1. The surface of a paste-type cadmium electrode containing cadmium oxide as the main active material is treated with an aqueous solution of a water-soluble polymer,
A method for producing an alkaline storage battery, characterized by forming a thin layer made of a water-soluble polymer on the surface. 2. Water-soluble polymers include carboxymethylcellulose (hereinafter referred to as CMC) and methylcellulose (hereinafter referred to as MC)
or polyvinyl alcohol (hereinafter referred to as PVA), the method for producing an alkaline storage battery according to claim 1. 3. The concentration of the water-soluble polymer aqueous solution is 0.5 wt% to 1.
The method for manufacturing an alkaline storage battery according to claim 1 or 2, wherein the content is 5 wt%.