JPH09306482A - Manufacture of hydrogen absorbing alloy electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a hydrogen absorbing alloy electrode capable of forming a paste layer of prescribed uniform thickness by using hydrogen absorbing alloy paste of low viscosity. SOLUTION: In an upper surface of a horizontally placed base stand 1, two spacers 2 of fixed thickness specifying thickness of an electrode paste layer are provided. To a region between the two spacers 2 in the upper surface of the base stand 1, a hydrogen absorbing alloy paste 3 is supplied, to adjust its thickness to thickness of the spacer 2 by a spatula 4. On the top, a punching metal 5 is mounted, and also on its top, in a position corresponding to each spacer 2, each spacer 6 is provided. To a region between the two spacers 6 in an upper surface of the punching metal 5, hydrogen absorbing alloy paste 7 is supplied, to adjust its thickness to thickness of the spacer 6 by the spatula 4.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a hydrogen storage alloy electrode used as a negative electrode of an alkaline storage battery.

[0002]

2. Description of the Related Art Recently, there is an increasing demand for alkaline storage batteries as a power source for electric vehicles and electric bicycles. In particular, among the alkaline storage batteries, the nickel-hydrogen storage battery having a hydrogen storage alloy electrode as a negative electrode has a large energy capacity, and has been attracting attention as a power source for the electric vehicles and the like.

In the hydrogen storage alloy electrode, which is the negative electrode of such an alkaline storage battery, for example, a paste containing the hydrogen storage alloy is applied to both surfaces of a core metal such as punching metal in which a large number of holes are formed in a thin metal plate. It is manufactured by It is important that the thickness of this paste be even and even. This is because if the thickness is non-uniform, the electrode reaction of the entire electrode will be non-uniform, thus deteriorating the charge / discharge characteristics of the storage battery.

In this nickel-hydrogen storage battery, a nickel electrode is used for the positive electrode and a hydrogen storage alloy is used for the negative electrode, and this hydrogen storage alloy electrochemically stores and releases hydrogen as an active material.

FIG. 5 is a diagram schematically showing a manufacturing process of a conventional hydrogen storage alloy electrode. In the figure, paste 110 is contained in paste tank 100. The paste 110 is a paste containing a hydrogen storage alloy and is prepared by kneading a hydrogen storage alloy powder, a conductive auxiliary agent, a thickener, and a binder into a paste.

The conductive auxiliary agent is added so that electricity can well pass through the paste 110 when the paste 110 is applied to the punching metal 120 which is a two-dimensional current collector to form an electrode. Yes, for example nickel (Ni)
Powder, cobalt powder, carbon powder, copper powder and the like are known.

The thickener is added in order to increase the viscosity of the paste 110, and is methylcellulose (M
C), carboxymethyl cellulose (CMC) and the like are known. The addition amount (concentration) of the thickener is determined by pulling up the punching metal 120 from the paste tank.
It is determined that the paste 110 has a viscosity sufficient to be applied to both surfaces of the punching metal 120.

[0008] Further, as the binder, after the paste 110 is applied to the punching metal 120, the punching metal 1
20 is added to bind and hold the alloy particles of the hydrogen storage alloy with each other.
Hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE) and the like are known.

The binder is generally used as a dispersion. When the strip-shaped conductive support (punching metal) 120 is pulled up from the lower side to the upper side in the paste tank 100 containing the above-mentioned paste 110, both sides of the punching metal 120 are passed when passing through the paste 110. The paste is applied to.

At this time, the addition amount (concentration) of the thickener is adjusted so that the paste 110 applied to the punching metal 120 is applied in an excessive amount. The excess paste is scraped off (removed) by the slits 130 to form a uniform paste layer having a desired thickness on both surfaces of the punching metal 120.

After that, the punching metal 120 coated with a uniform paste having a desired thickness is sent to a drying furnace,
The paste is dried. Although not shown in the drawing, a step of cutting the punching metal 120 into a predetermined length is included thereafter. The length to be cut and the width of the punching metal are appropriately determined according to the size of the battery to be manufactured.

Conventionally, as described above, a uniform paste 11 having a predetermined thickness is formed on both surfaces of the punching metal 120.
A hydrogen storage alloy electrode formed by applying 0 was manufactured.

[0013]

In the above-mentioned conventional manufacturing method, in order to give the paste 110 a sufficient viscosity, a thickening agent having a high concentration (for example, methyl cellulose (M
C) 2% solution) was added.

However, this thickener becomes a factor that hinders the gas absorption of the hydrogen storage alloy and deteriorates the electrical conductivity. This is because the thickener present inside the paste also has an adverse effect, but the components of the thickener present on and near the surface of the alloy adversely affect the hydrogen gas absorption.

Therefore, there is a problem that the performance of the hydrogen storage alloy electrode is deteriorated when the ratio of the thickener added to the paste is high. However, in the above conventional manufacturing method,
If the addition amount (concentration) of the thickener is reduced, the paste 11
Since 0 cannot obtain sufficient viscosity, the paste cannot flow onto the punching metal during pulling up, so that a sufficient amount of paste cannot be applied and the slit 130 allows the paste to have a desired uniform thickness. There wasn't.

An object of the present invention is to form a uniform hydrogen storage alloy paste layer having a predetermined thickness on both surfaces of a punching metal even if a hydrogen storage alloy paste having a low viscosity and a low ratio of a thickener to be added is used. A method of manufacturing a hydrogen storage alloy electrode is provided.

[0017]

According to a first aspect of the present invention, there is provided a method for manufacturing an electrode, wherein a two-dimensional current collector, which is a metal core of an electrode, is leveled, and another horizontal surface is provided on the lower surface of the two-dimensional current collector. Using a spacer having a predetermined uniform thickness provided on the surface, a uniform paste having the same thickness as the spacer is applied, and a spacer having the same shape as the spacer is formed on the upper surface of the two-dimensional current collector. A uniform paste having the same thickness as the spacer is applied by using.

According to a second aspect of the present invention, in the electrode manufacturing method, the paste continuously supplied on the conveyor belt having the first spacers of a predetermined thickness on the upper surfaces of both ends is used as a reference for the first spacers. To a predetermined thickness, the two-dimensional current collector is placed horizontally on the first spacer, and the paste having the predetermined thickness is applied to the lower surface of the two-dimensional current collector to form a two-dimensional current collector. A second spacer is arranged on the upper surface of the body at a position corresponding to the first spacer, and the paste supplied to the upper surface of the two-dimensional current collector is made to have a predetermined thickness with reference to the second spacer, and the two-dimensional current collector is formed. The paste having a predetermined thickness applied to the lower surface and the upper surface of the electric body is dried in a drying oven.

In the electrode manufacturing method according to the above-mentioned claims 1 and 2, in the state where the two-dimensional current collector, which is the core metal of the electrode, is horizontal, the lower surface and the upper surface thereof are each on a horizontal surface (two-dimensional current collector). The top surface of the or other horizontal surface such as a conveyor belt)
The paste supplied to the substrate is adjusted to have a uniform thickness by using a spacer having a predetermined thickness provided on the surface.

Therefore, even if a paste having a low ratio of the thickener to be added and a low viscosity is used, the paste does not run down and the thickness cannot be adjusted,
A paste having a predetermined uniform thickness can be applied to both surfaces of the two-dimensional current collector.

From the above, it is possible to reduce the solution concentration of the thickener added to the paste to, for example, 0.2 to 0.5%. As described above, the performance of the electrode can be improved by manufacturing the electrode by reducing the addition rate of the thickener that causes the deterioration of the performance of the electrode.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a basic method for manufacturing a hydrogen storage alloy electrode.

The hydrogen storage alloy electrode is manufactured in the order of (a), (b), (c) and (d) of FIG. First,
In FIG. 1A, a spacer 2 having a predetermined thickness is fixed at a predetermined position on the upper surface of the base 1. The thickness of the spacer 2 is the same as the thickness of the hydrogen storage alloy paste applied to the punching metal.

Next, in FIG. 1B, after supplying the hydrogen storage alloy paste 3 between the two spacers 2, the excess paste is removed by a spatula 4 to flatten the surface of the paste 3. The thickness of the hydrogen storage alloy paste 3 is adjusted to the thickness of the spacer 2.

Subsequently, in FIG. 1C, a punching metal 5 is placed on the hydrogen storage alloy paste 3 (and the two spacers 2) having a uniform thickness (thickness of the spacer 2), and further. The spacers 6 are placed and fixed on the positions corresponding to the respective spacers 2 thereon. Spacer 2 and spacer 6
Have the same shape.

Finally, in FIG. 1D, the hydrogen storage alloy paste 7 is applied on the punching metal 5, and the spatula 4 is used again so that the thickness of the paste 7 becomes uniform with the thickness of the spacer 6. To

Thereafter, by drying, the hydrogen storage alloy paste having a predetermined thickness is bound to both surfaces of the punching metal 5. Here, FIGS. 2A and 2B show a composition table of the hydrogen storage alloy paste in the related art and the present embodiment.

In the present embodiment, the hydrogen storage alloy paste is composed of 76% hydrogen storage alloy powder, 4% nickel (Ni) powder as a conduction aid, and 19% methylcellulose solution as a thickening agent. As an agent, for example, polytetrafluoroethylene (PTFE) is kneaded to produce 1%.

The composition of the hydrogen storage alloy pastes 3 and 7 according to the present embodiment shown in FIG. 2 (a) differs from the composition of the conventional paste shown in FIG. 2 (b) in that the methylcellulose solution added as a thickener is used. Is 0.3% (conventionally 2% solution).

By adding such a thickening agent having a low concentration, the viscosities of the hydrogen storage alloy pastes 3 and 7 are smaller than those of the conventional ones, but the horizontal base 1 as described above is used.
It has sufficient viscosity to perform the work of making its thickness uniform above.

Since the solution concentration of the thickener is low, the components of the thickener contained in the hydrogen storage alloy electrode are reduced,
The deterioration of the performance of the hydrogen storage alloy electrode, which is caused by the component of the thickener, can be suppressed more than ever before. Conversely speaking, the performance of the hydrogen storage alloy electrode is improved as compared with the conventional one.

Next, a mass production method of electrodes to which the above electrode production method is applied will be described. FIG. 3 is a structural diagram of the hydrogen storage alloy electrode manufacturing apparatus according to the present embodiment, and FIG.
Is a top view, and FIG. 3B is a side view.

In the drawing, the rotating sheet 11 with primary spacers is provided with primary spacers 11a having a predetermined thickness at both ends of the upper surface (outer surface) of the rotating sheet 11b which is rotated counterclockwise by the rotating roller 12. It is a conveyance belt (belt conveyor) having the above configuration.

The paste supply unit 13 supplies the hydrogen storage alloy paste 13a onto the rotating sheet 11b between the two primary spacers 11a. For example, as shown in FIG. 3A, the paste supply unit 13 has a configuration in which the paste supply pipes are arranged in a row in the lateral direction of the rotating sheet 11b.

The primary knife 14 is a spatula for making the hydrogen storage alloy paste 13a placed on the rotary sheet 11b uniform in thickness (thickness of the primary spacer 11a). The primary knife 14 is arranged at a position where the linear tip of the primary knife 14 contacts the upper surface of the primary spacer 11a.

The punching metal supply roll 15 continuously supplies the punching metal 16 onto the hydrogen storage alloy paste 13a adjusted to the thickness of the primary spacer 11a by the above-mentioned primary knife 14, and a long strip of punching metal is formed. It is wound on a roll and is drawn out to be supplied horizontally between the rotating sheet 11 with the primary spacer and the secondary spacer 17.

The secondary spacer 17 is, for example, a spacer having the same thickness and width as the primary spacer 11a, and serves as a reference for making the hydrogen storage alloy paste supplied to the upper surface of the punching metal 16 have a uniform thickness. It is a thing. As shown in FIG. 3A, the secondary spacers 17 are provided at positions corresponding to the respective primary spacers 11a,
Each of the secondary spacers 17a and 17b is rotated clockwise by a plurality of rollers 18a to 18f.

The plurality of rollers 18a to 18f rotate the secondary spacer 17 in the clockwise direction, and the lower four rollers 18a to 18d press the punching metal 16 downward via the secondary spacer 17. As a result, the punching metal 16 has the primary spacer 11 at both ends.
The position a is fixed by being pressed between a and the secondary spacer 17 and the position is fixed, and the primary spacer 11a and the secondary spacer 17 are conveyed from the right to the left in the drawing as the primary spacer 11a and the secondary spacer 17 rotate.

The paste supply unit 19 supplies the hydrogen storage alloy paste 19a to the upper surface of the punching metal 16 and is the same as the paste supply unit 13 described above.
The secondary knife 20 is a spatula for making the hydrogen storage alloy paste supplied to the upper surface of the punching metal 16 to have a uniform thickness, and its tip is on the upper surface of the secondary spacer 17, as with the primary knife 14. It is arranged at the position where it abuts.

The drying furnace 21 dries the hydrogen storage alloy pastes 13a and 19a coated on both surfaces of the punching metal 16 with a predetermined uniform thickness. In the hydrogen storage alloy electrode manufacturing apparatus having the above structure, the hydrogen storage alloy paste 13
a and 19a have the same composition as the hydrogen storage alloy pastes 3 and 7 of FIG. 1 and contain 0.3% of methyl cellulose as a thickener.
It is a paste to which a solution is added.

In the above electrode manufacturing apparatus, the punching metal 16 which is the conductive support of the electrode is fed in the horizontal direction while the hydrogen storage alloy paste 1 having a predetermined thickness is formed on both surfaces thereof.
3a and 19a are applied. Like this
While supplying the punching metal 16 in the horizontal direction and carrying the hydrogen storage alloy pastes 13a, 19a in the horizontal direction above and below the punching metal 16, the punching metal 16 is adjusted to have a predetermined uniform thickness by the primary and secondary spacers and the primary and secondary knives. Because
Even using a hydrogen storage alloy paste with a low concentration of thickener,
Can be applied without problems. And the drying oven 21
After being dried with, the binder, such as polytetrafluoroethylene (PTFE), binds and holds the punching metal 120 and the alloy particles of the hydrogen storage alloy, so that the paste layer does not peel off.

By producing an electrode using a paste having a low concentration of the thickener thus added (a small amount of methylcellulose (MC) added), the proportion of methylcellulose contained in the produced hydrogen storage alloy electrode is reduced. As a result, the electrode performance such as reactivity, electric conductivity and hydrogen gas absorption is improved as compared with the conventional one.

FIG. 4 is a graph showing the results of performance experiments of the battery using the electrode manufactured by the method of this embodiment and the electrode manufactured by the conventional method. The horizontal axis of the graph shown in the figure is the discharge rate [C], and the vertical axis is the MH alloy utilization rate [%]. The discharge rate [C] represents the reciprocal of the t-hour rate discharge, and for example, 0.2C in the figure corresponds to the 5-hour rate discharge. Similarly, 1 [C] is 1 hour rate discharge, 2 [C] is 0.
It is a 5-hour rate discharge. The MH alloy utilization rate [%] represents the capacity of each hourly rate discharge as a percentage with the capacity of the five hourly rate discharge as a reference (100%).

As shown in the graph of the figure, both the electrode produced by the production of this embodiment and the electrode produced by the conventional method have a discharge rate [C] of 5 hours rate discharge (0.2 [C]). The utilization factor decreases as the value increases, but the electrode produced by the conventional method has a greater reduction rate.

As described above, the performance of the electrode prepared by the method of this embodiment is higher than that of the electrode prepared by the conventional method. This is methyl cellulose (MC) contained in the alloy
This is because the amount was reduced and the factors that hinder the reactivity and electrical conductivity were reduced. Moreover, the hydrogen gas absorption of the hydrogen storage alloy is also improved.

In the above embodiment, the description was made assuming that the solution concentration of methyl cellulose, which is a thickener, is 0.3%.
According to the electrode manufacturing method of the present invention, it can be manufactured under the condition that the solution concentration of methyl cellulose is 0.2 to 0.5%.

[0047]

As described above, according to the electrode manufacturing method of the present invention, the viscosity is lowered by reducing the addition amount of the thickener which is one of the factors that deteriorates the performance of the hydrogen storage alloy electrode. Even if the hydrogen storage alloy paste is used, the paste having a predetermined uniform thickness can be applied to both surfaces of the punching metal.

Therefore, the factors that deteriorate the performance of the hydrogen storage alloy electrode are reduced, so that the performance is improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a basic method for manufacturing a hydrogen storage alloy electrode according to an embodiment.

FIG. 2 is a diagram comparing the compositions of the hydrogen storage alloy paste in the conventional and the present embodiment.

3A and 3B are structural views of the hydrogen storage alloy electrode manufacturing apparatus according to the present embodiment, where FIG. 3A is a top view and FIG. 3B is a side view.

FIG. 4 is a graph showing the results of performance experiments of batteries using the electrode manufactured by the method of the present embodiment and the electrode manufactured by the conventional method.

FIG. 5 is a diagram schematically showing a manufacturing process of a conventional hydrogen storage alloy electrode.

[Explanation of symbols]

 1 Base 2 Spacer 3 Hydrogen Storage Alloy Paste 4 Spatula 5 Punching Metal 6 Spacer 7 Hydrogen Storage Alloy Paste 11 Rotating Sheet with Primary Spacer 12 Rotating Roller 13 Paste Supply Section 13a Hydrogen Storage Alloy Paste 14 Primary Knife 15 Punching Metal Supply Roller 16 Punching Metal 17 Secondary spacer 18 Roller 19 Paste supply section 19a Hydrogen storage alloy paste 20 Secondary knife 21 Drying furnace 100 Paste tank 110 Hydrogen storage alloy paste 120 Conductive support (punching metal) 130 Slit

Claims (4)

[Claims] 1. A method for producing a hydrogen storage alloy electrode, comprising applying a paste containing a hydrogen storage alloy to both surfaces of a two-dimensional current collector, wherein the two-dimensional current collector is horizontal and On the lower surface, a uniform paste having the same thickness as the spacer is applied using a spacer having a predetermined uniform thickness provided on another horizontal surface, and on the upper surface of the two-dimensional current collector, A method for manufacturing a hydrogen storage alloy electrode, characterized in that a spacer having the same shape as the spacer is used and a uniform paste having the same thickness as the spacer is applied. 2. A method of manufacturing a hydrogen storage alloy electrode, comprising applying a paste containing a hydrogen storage alloy to both surfaces of a two-dimensional current collector, the method comprising: a conveyor belt having first spacers each having a predetermined thickness on both upper surfaces thereof. The paste continuously supplied to the first
Of the spacer to the predetermined thickness, the two-dimensional current collector is placed horizontally on the first spacer, the paste of the predetermined thickness on the lower surface of the two-dimensional current collector. The second spacer is applied at a position corresponding to the first spacer on the upper surface of the two-dimensional current collector, and the paste supplied to the upper surface of the two-dimensional current collector with the second spacer as a reference. A method for producing a hydrogen storage alloy electrode, which comprises setting a predetermined thickness and drying a paste having a predetermined thickness applied to the lower surface and the upper surface of the two-dimensional current collector in a drying furnace. 3. The method for producing a hydrogen storage alloy electrode according to claim 1, wherein the paste has a solution concentration of a thickener added to 0.2 to 0.5%. 4. A hydrogen storage alloy electrode manufacturing apparatus in which a paste containing a hydrogen storage alloy is applied to both surfaces of a two-dimensional current collector, and a transport method in which primary spacers having a predetermined uniform thickness are provided at both ends of the upper surface thereof. A belt, a linear knife having a linear tip portion abutting on the upper surface of the primary spacer, and a primary knife that continuously supplies the paste onto the conveyor belt to a predetermined uniform thickness, the paste and the primary spacer A two-dimensional current collector supply means for supplying the two-dimensional current collector, a secondary spacer provided at a position corresponding to each of the primary spacers on the supplied two-dimensional current collector, and a linear shape A secondary knife whose tip portion is in contact with the upper surface of the secondary spacer and which makes the paste continuously supplied onto the two-dimensional current collector have the same uniform thickness as the secondary spacer; Characteristic hydrogen Storage alloy manufacturing equipment.