JPS6081765A - Manufacturing method for paste type cadmium negative electrode plate - Google Patents

Abstract

PURPOSE:To increase absorption capability of the captioned electrode plate and strength thereof by providing a conductive layer make of carbon powder on the surface of a pasty active material layer mainly composed of a cadmium active material with which an electrode core body is coated, and thereafter charging said layer with quantity of electricity less than specific % of electrode plate capacity. CONSTITUTION:An electrode core body 2 is coated with paste 1 yielded by mixing cadmium oxide and a binder, etc., and dried, and thereby a paste type cadmium electrode plate is formed. The electrode plate is dipped in a conductive coating material, dried, and thereby an electrode plate including a thin carbon powder layer 3 on its surface is made, pressed and formed. The resultant elec- trode plate is forced to pass through a forming device, charged with quantity of electricity less than 60% of electrode plate capacity, washed and dried to obtain a finished electrode plate. A negative electrode plate constructed in such a way can allow metallic cadmium to exist on its surface even if the amount of charging for formation is small, improving its capability of absorbing oxigen gas for economical use thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing a paste-type cadmium cathode plate used in alkaline storage batteries, particularly sealed alkaline storage batteries.

(b) Conventional technology Paste-type cadmium cathode plates used in sealed alkaline storage batteries are generally made of metal cadmium by chemical conversion in order to improve the ability to absorb oxygen gas generated from the anode due to overcharging and to ensure predetermined discharge characteristics. It is being generated.

Conventional chemical conversion methods include a method in which power is supplied directly from a six-core body that holds the active material, or a method in which power is continuously supplied from the surface of the electrode plate via a rotating roll.
When cadmium oxide and cadmium hydroxide, which have low conductivity, are charged in an alkaline solution, metal cadmium, which is a charging product, is generated from around the electrode core in each of the above chemical conversion methods. When used in a lucadmium storage battery, the cathode capacity is made larger than the anode capacity so that even when the anode is fully charged, an unsleeping portion remains on the cathode, so metal cadmium is present on the cathode surface, causing separation. It has become. Therefore, the oxygen gas generated from the anode due to overcharging is absorbed only after passing through the surface of the electrode plate, which has poor air permeability, resulting in a problem that the oxygen gas absorption ability is reduced.

1. Purpose of the Invention In view of the above, the present invention provides a base type cadmium cathode plate in which the strength of the electrode plate surface is increased and the oxygen gas absorption ability is improved by forming metal cadmium on the electrode plate surface. That is.

(C) Structure of the Invention The paste-type cadmium cathode plate of the present invention is produced by providing a conductive layer made of carbon powder on the surface of a paste-like active material layer mainly composed of cadmium active material applied to an electrode core, and then applying a conductive layer to the electrode core. Metallic cadmium is generated on the surface of the electrode plate by charging the battery with an amount of electricity that is 60% or less of the capacity.

Example 3 Paste-type cadmium electrode plates prepared in the conventional manner by mixing cadmium oxide and a binder, etc., and applying the mixture to a bare electrode core and drying were prepared by Nippon Graphite Industries (Kiku). After dipping in the conductive paint Bunny Hate BP-333 and drying it, a plate with thin carbon powder on the plate surface is created.
This electrode plate was suppressed to 0.62 [73]. The electrode plate of the present invention thus created is carbon powder of about 20 to 0 μm @
It had a This electrode plate will be used as an electrode plate. Further, as a comparison, a paste-type cadmium electrode plate produced by the conventional method in the above-mentioned embodiment was used, and this electrode plate was pressed and shaped into a shape of 62 yxs to obtain an electrode plate B. 1 and 2 are cross-sectional views of these electrode plates and B.

In the figure, (1) shows the active material 1, (2) shows the electrode core, and (3) shows the carbon powder layer.

FIG. 5 is a schematic diagram of the chemical conversion equipment, which is composed of power supply rollers (6) and (7), a rotating roller (8), a battery case (9), a pair of counter electrodes (10), and an electrolyte all. , the electrode plate (12 receives power from the power supply rollers (6) and (7) m
It is charged while passing between a pair of opposite poles.

The electrode plates N and BY were passed through this chemical conversion device, charged to about 35% of the capacity of the electrode plates, and then washed with water.

By drying, completed electrode plates K and B' were obtained. FIGS. 3 and 4 are cross-sectional views of the electrode plate and B. FIG.

In the figure, (4) shows the cadmium active material in an uncharged state, and (5) shows the cadmium active material in a charged state, and components common to those in FIGS. 1 and 2 are given the same reference numerals. As is clear from FIGS. 3 and 4, the comparative electrode plate B' has metallic cadmium in a charged state around the electrode core (2), whereas the electrode plate of the present invention has Metallic cadmium is produced in the irradiation process.

Next, these poles @K and B' are processed using a known sintering method "QA".
QOm eight charge, snake 0°C2AOmA charge'? The gas pressure inside the pond was measured. The results are shown in Figures 6 and 7. In the figure, K and I represent batteries using electrode plates K and B'. It can be seen that FIGS. 6 and 7.

Considering the reason for this, 2. During chemical formation, current flows through the carbon powder 1 (d + 31) in the electrode plate of the present invention, and charging progresses inside from the part that contacts the carbon powder layer (3), so that the metal cadmium It is formed on the surface layer of the polar coffin.

When a sealed needle-type gel-cadmium storage battery using this electrode plate is charged, when oxygen is generated from the anode due to overcharging, it comes into contact with the metal cadmium present on the cathode plate surface 2, which easily comes into contact with oxygen, and is absorbed inside the battery. This is thought to be because the increase in gas pressure was suppressed. In addition, since metal cadmium is formed near the electrode plate surface 1 and forms a matrix of metal cadmium, the electrode plate strength is increased compared to the conventional partial charging.

Peeling of the electrode plate when used by winding the electrode plate in a spiral shape.

In addition, since it has a conductive coating made of carbon powder, the resistance to power supply from the electrode plate surface is reduced, and a low source voltage can be achieved. Since it is smooth, it is easy to insert the stagnant body into the outer can.

As described above, the cathode plate produced by the manufacturing method of the present invention (2) can have metal cadmium present on the electrode plate surface even by applying a small amount of chemical charge, which improves the oxygen gas absorption ability. However, even with the conventional manufacturing method, if chemical charging is performed that exceeds 60% of the plate capacity, metallic cadmium generated by charging will appear on the surface of the FI plate, which is the purpose of Ichiki's invention. However, in the manufacturing method of the present invention, especially when the amount of charge electricity is 60 or less, the performance of the cathode plate is greatly improved compared to that of the conventional method. There is a difference, and the amount of chemical charging is also small, making it economical.

Next, when comparing the method of the present invention with a conventional method in which metallic cadmium is generated on the surface of the cathode plate by bringing a metal plate into contact with the surface of the cathode plate and charging Metal cadmium is converted to cadmium hydroxide in a discharged state, deteriorating its ability to absorb oxygen gas pressure.1 In contrast, in the electrode plate of the present invention, metal cadmium generated as the center of the bipolar core during charging is converted to cadmium hydroxide on the cathode surface. When reaching a part of the carbon powder 1
Since metal cadmium is gradually generated along the electrode plate surface, the metal cadmium on the surface of the electrode plate does not disappear due to repeated charging and discharging, and has excellent oxygen gas absorption ability over a long period of time.
Maintain p.

Also, compared to the results when metal powder was used for the conductive layer formed on the surface of the electrode plate.

(2) In the case of a base having cadmium as the metal powder, the effect cannot be maintained because the metal cadmium as the conductive IC 11 directly participates in the charge/discharge reaction as described above.

■ When using aluminum, lead-tin, lead, copper, etc., the conductive layer disappears as it dissolves into the alkaline electrolyte.
loses its effect. In addition, 9-curved lead forms needle-like crystals on the cathode surface through charging and discharging reactions, causing short circuits within the battery and shortening the battery life. Lead accelerates deterioration of the electrode plate capacity, and copper -Cu2+ (→ The reaction of Cu promotes self-discharge of the battery.

■ When iron-nickel, cobalt, platinum, etc. are used, the hydrogen overvoltage is small, causing significant hydrogen gas to be generated from the cathode during overcharging, which can destroy the sealed internal system of the battery.

■ Gold, silver, and other metals that are produced in small amounts are much more expensive than carbon powder, making it difficult to put them to practical use.

■ Other sin Metals close to metal elements and substances called conductive metal oxides are also not effective because they have low electrical conductivity and are less effective, or are expensive.

On the other hand, carbon powder is (1) stable in alkaline electrolyte, (2) does not participate in charge/discharge reactions and does not have any adverse effect on battery characteristics, and (3) produces significant hydrogen gas due to reduction in hydrogen overvoltage. (4) It is inexpensive. In this way, carbon powder is superior to metal powder and can be said to be the most effective material.

Also carbon powder or its @turbidity? When fibrous carbon is used instead of coating, the uniformity of the electrode plate surface L is poor, so the effect on the oxygen gas absorption capacity is small, and the conductive layer is Since the thickness is large, it is disadvantageous from the viewpoint of energy density.

Fuzzing of carbon fiber can cause a short circuit inside the battery.

It's inappropriate.

Effects of the Invention As described above, since the electrode core of the present invention is filled with an electric charge of less than cadmium active material, it has advantages such as increased oxygen gas absorption ability, increased electrode plate strength, and lowered chemical power supply voltage. It is possible to provide a paste-type cadmium cathode plate with excellent performance.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the electrode plate according to the present invention and a comparative electrode plate before chemical charging; FIGS. 3 and 4 are cross-sectional views of the electrode plate according to the present invention and a comparative electrode plate after chemical charging; FIG. 5 is a schematic diagram of the chemical conversion apparatus, and FIGS. 6 and 7 are drawings showing the relationship between charging time and battery internal gas pressure. (1)...active material weight, (2)...nuclear body, (3)
... Dasaku powder +1. (,11...Active material in uncharged state, (5)...Active material in charged state. Fig. 6 Rainbow electric time pJ (hcyrrs) Fig. 7. Figure tip, electric, leap ゛1° pa)

Claims (1)

[Claims] (1) A conductive layer made of carbon powder on the surface of a paste-like active material layer mainly made of cadmium active material applied to the electrode core? A method for producing a paste-type cadmium cathode plate, which is characterized in that, after being provided, a qi storm of 60% or less of the capacity of the plate is charged.