JPS60202666A - Paste type cadmium anode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To prevent coming off of active material on the surface of an electrode plate by forming a water soluble gelling agent layer which is gelled by alkaline electrolyte on the surface of electrolyte plate. CONSTITUTION:A paste type cadmium anode plate for alkaline storage battery is formed by spreading paste mainly comprising cadmium oxide on a conductive core. A layer, having a thickness of 2-20mu, of water soluble gelling agent such as polyvinyl alcohol which forms a gelled layer by contacting alkaline electrolyte is formed on the surface of the plate. This prevents coming off of active material, and environment in battery manufacturing is improved. When 5- 150wt% of carbon powder is dispersed in gelled layer, oxygen gas absorbing ability is increased.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a paste-type power domiwam cathode plate for alkaline storage batteries, which is easy to handle and has improved high rate discharge characteristics and oxygen gas absorption performance. .

(0) Prior Art Conventionally, paste-type cadmium 9M cathode plates for alkaline storage batteries have been developed by combining metallic cadmium, which corresponds to a part of the precharge amount, and oxide, which is the main active material, as shown in Japanese Patent Laid-Open No. 58-80268. Active material powder consisting of cadmium, hydroxypropylene cellulose as a paste and polypropylene fiber as a reinforcing material. 1: In addition, a paste is obtained, and this paste is applied to both sides of the punching core and dried to produce fF. Gas absorption performance has been improved.

However, even if the electrode plate is configured as described above, it is not possible to completely prevent the active material from falling off, and by increasing the amount of glue added as a binder, the retention force of the active material is increased and the electrode plate strength is increased. can be increased, but an increase in the size impedes the inter-polar conductivity between the active material particles. Therefore, there is a limit to the amount that it can be added, and it is unavoidable to some extent that the active material powder on the surface of the electrode plate will fall off during the battery assembly process, reducing the capacity of the electrode plate and worsening the working environment. There is a problem. Furthermore, as mentioned above, in order to omit the chemical formation process, in the case of electrode plates to which metal cadmium, which is a charged product, is added as a precharge amount, a conductive matrix of metal cadmium is generated, as in the case of electrode plates that have been chemically formed. Because I haven't.

In particular, there is a problem in that metal cadmium 9 is difficult to form on the surface of the electrode plate, which easily comes into contact with the oxygen gas generated from the anode, and the oxygen gas absorption performance is poor. An object of the present invention is to provide a paste type cadmium 9M cathode plate for an alkaline storage battery in which active material particles are formed on the surface of the electrode plate by forming a water-soluble glue thin film that gels only when it comes into contact with an alkaline electrolyte on the surface layer of the plate. It is.

B) Structure of the Invention The paste-type cadmium cathode plate for alkaline storage ponds of the present invention has a paste containing cadmium oxide as a living substance applied to the surface of the electrode plate on a conductive core.

It has a water-soluble glue thin film layer that forms a gel layer in contact with an alkaline electrolyte, and the thickness of the glue thin film layer is 2.
Further effects can be obtained by using polyvinyl alcohol as a glue that forms the gel layer with a thickness of ~20 microns. In addition, in the thin film layer of the glue, the weight ratio to the glue is 5.
When 0 to 150% of carbon powder is dispersed, the oxygen gas absorption performance of the electrode plate can be greatly improved.

(e) Examples Examples of the present invention will be shown and explained below. [Example] After mixing 100 y of metal cadmium powder with an average particle size of 3 microns into 900 jF of cadmium oxide powder, which is the main active material, paste is added to this mixed powder. An active material paste is prepared by adding methyl cellulose 6F as a raw material and 10 tons of polypropylene fibers having a length of about 2 inches and a thickness of 2 deniers as a reinforcing material and thoroughly kneading the mixture. The paste thus obtained was applied to an electrode core made of punched metal, dried, and then coated with 10% polyvinyl alcohol on its surface.
The aqueous solution was uniformly sprayed and dried to obtain a master electrode plate having a thin film layer of about 8 microns on the surface of the active material 11. This master electrode plate was cut into a length of 65 mm and a width of 20011 tiA to obtain a cadmium cathode plate.

This cathode plate and an anode plate (vertical filter 31
A sealed nickel-cadmium battery having a nominal condition of 1.28H was prepared by combining a 7M% (width: 160M, thickness: 0.7M) and a nylon unlined fabric separator and adding an alkaline electrolyte.

In addition, in place of the polyvinyl alcohol used as a glue for the thin film layer formed on the surface of the cadmium cathode plate in Kameike, carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose were used as glue, and the other parts were the same, but nickel A lucadmium core pond was prepared. These batteries are designated as B, G, and D, respectively. In addition, the cathode plate table of these batteries is jl! The paste used was adjusted to have the same viscosity as the aqueous solution of polyvinyl alcohol mentioned above.

Still other examples include the aforementioned batteries A, B, and O.

Acetylene black was added in an amount corresponding to a 1:1 weight ratio to the polyvinyl alcohol used in 'a/[118] to the aqueous glue solution used to form a thin film layer on the surface of the cadmium cathode plate in step D. A nickel-cadmium battery was fabricated in the same manner as described above, except that a thin film j- containing acetylene black was formed on the surface of the cathode plate by using each of them in suspension. The song created in this way is transferred to the batteries ', B', and B, corresponding to B, O, and D, respectively.
Let O',,D' be.

[Comparative example]

A comparative battery E was prepared in the same manner as in the example battery except that no glue thin film layer was provided on the surface of the cadmium cathode plate.

The table below compares the characteristics of these batteries and the cadmium cathodes used in these batteries. Powder falling off from electrodes in the table refers to active material falling off from the cathode plate during the battery manufacturing process. ○ indicates that a small amount of active @A powder adhered to the hand, ◎ indicates that active material powder did not adhere to the hand, and ``dL battery capacity'' is 120 QmA, and the battery voltage was 1.Ov. The capacity of the battery when discharging is finished at the point in time, the internal resistance is the internal resistance of the battery in the discharged state, and the internal pressure is 1 at 660m8 at 0°C.
Shows the gas pressure inside one battery when overcharging after 8 hours of original charging.

From the above table, it can be seen that the electrode plate of the present invention clearly has less active material falling off than the comparative electrode plate. Therefore, the cadmium cathode plate of the present invention can prevent damage to the working environment during the pond manufacturing process, and can also suppress a decrease in Kameike capacity due to dropout of the active material.

In addition, the battery using the cathode plate of the present invention is superior to the comparative Ilc cells in both cell internal resistance and cell internal pressure. &9.
Looking at the operating voltage of high-rate discharge, the current is 8.0C (
The current value of 1 # of electricity flowing in 1 hour is 10
80 is 8 times that value ('1 flow), and the average operating mdL pressure is 9 comparisons per cell per cell, i = < 5 DmA. This is because the gel layer formed on the cathode plate surface increases the electrolytic m value held between the anode plate and the electrolytic a
It is presumed that the resistance decreased and the operating voltage due to high-rate radiation became redder due to this. The reason why the internal gas pressure of the battery using the plate is significantly reduced compared to the comparative battery is that the surface of the cathode plate is covered with a conductive layer due to the carbon powder dispersed in the thin film of glue on the surface of the cathode plate. Therefore, when cadmium, a highly electron-conductive metal that is a charging product in element 1, gradually forms from near the conductive core and reaches the thin film layer containing the carbon powder, This is thought to be because the thin film layer and the conductive core are electrically connected, and metal cadmium, which dissipates oxygen gas, can be generated on the surface of the cathode plate, which easily comes into contact with oxygen gas.

The thickness of the paste thin film layer on the surface of the paste-type cadmium cathode plate described above is preferably 2 to 20 microns, regardless of whether it contains carbon powder or not.
If the diameter is less than 2 microns, the effect of preventing the active material from falling off is small;
If it is 0 micron or more, it will actually increase the battery reaction resistance and increase the internal resistance. In addition, as the glue used for this glue thin film layer, any water-soluble glue that gels when dissolved in alkali IJ' can achieve almost the same effect, but polyvinyl alcohol has a film-forming property. It is preferable because it has the following advantages: it has a small content of impurities such as O and e- which are harmful to the music, it has a more appropriate degree of gelation, and it has a high affinity with alkaline electrolytes.

Further, the amount of carbon dispersed in the thin film layer of the thickening material is suitably 50 to 150% in terms of 4itZ ratio to the thickening material; if it is less than this, sufficient effect cannot be obtained due to poor conductivity; In this case, the viscosity of the paste increases, making uniform coating difficult. Note that it is more preferable to use acetylene black as the carbon powder because it contains fewer impurities.

(F) Effects of the Invention The paste-type cadmium electrode plate for alkaline storage batteries of the present invention is formed by coating a conductive core with a base material containing cadmium oxide as a living substance on the surface of the electrode plate.

It has a water-soluble glue thin film layer that forms a gel layer when in contact with an alkaline aqueous solution, which prevents the active material from falling off, which improves the working environment during TO manufacturing and suppresses capacity loss. Furthermore, the gel layer can improve the internal resistance and internal pressure of the battery after it is constructed. Furthermore, if carbon powder such as acetylene black, graphite, or activated carbon is dispersed in the thin glue film J-, the oxygen gas absorption performance can be greatly improved and the increase in gas pressure inside the battery can be suppressed to a low level.

Claims (1)

[Claims] (1) A paste containing 9 cadmium oxide as the main active material is introduced.
A paste-type cadmium cathode for an alkaline storage battery, characterized by having a water-soluble glue thin film layer that forms a gel layer in contact with an alkaline electrolyte on the surface of an electrode plate coated on an IIL core body. &. (21) Paste-type cadmium cathode plate for alkaline storage batteries according to claim 11, wherein the thickness of the thin film layer of the paste is 2 to 20 microns. (3) Claim 1, wherein the paste is polyvinyl alcohol. Paste-type cadmium cathode plate for alkaline storage batteries according to item 111 or item (2). (4) The thin film layer of glue contains 50 to 1 in weight ratio to glue.
Claim No. 1 (50% carbon powder is dispersed)
1) Item (Paste-type cadmium cathode plate for alkaline @ batteries according to any one of Item 31).