JP2001135310A - Producing method of paste hydrogen absorption alloy electrode, and producing method of angular alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a paste hydrogen absorption alloy electrode which can prevent bent of the electrode when a conductive board is pressure formed after a paste containing hydrogen absorption alloy is applied to one side thereof and then dried. SOLUTION: A method for producing a paste hydrogen absorption alloy electrode comprises a step for applying a paste which contains hydrogen absorption alloy on one side of a conductive board 1 and drying the paste to form a hydrogen absorption alloy containing layer 2, a step for pressure forming the boards on which the hydrogen absorption alloy containing layer is formed, while they are piled with the conductive board 1 sides thereof facing each other, and a step for peeling the piled boards each having the hydrogen absorption alloy containing layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a paste-type hydrogen storage alloy electrode and a method for producing a prismatic alkaline secondary battery.

[0002]

2. Description of the Related Art As a prismatic nickel-metal hydride secondary battery which is an example of a prismatic alkaline secondary battery, for example, a battery having a structure as shown in FIG. 5 is known.

As shown in FIG. 5, an electrode group 12 is housed in a metal container 11 having a bottomed rectangular cylindrical shape and also serving as a negative electrode terminal. The electrode group 12 is formed by alternately stacking a nickel positive electrode 14 and a paste-type hydrogen storage alloy negative electrode 15 housed in a bag-shaped separator 13 such that the outermost layer is the negative electrode 15. Each negative electrode 15 has a structure in which a hydrogen storage alloy-containing layer is supported on both surfaces of a conductive substrate having a two-dimensional structure such as punched metal. The alkaline electrolyte is contained in the container 11. The sealing member 16 having a positive electrode terminal and an explosion-proof function includes a rectangular sealing plate 18 having a gas vent hole 17 opened, and the sealing plate 1.
A cap-shaped positive electrode terminal 19 disposed on the upper surface 8 so as to cover the gas vent hole 17, and a space surrounded by the sealing plate 18 and the positive electrode terminal 19 so as to cover the gas vent hole 17. And a rubber safety valve 20. A plurality of gas vent holes 21 are opened in the positive electrode terminal 19. A bottomed rectangular cylindrical insulating gasket 22 having an opening at the bottom is disposed in a compressed state between the container 11 and the sealing plate 18, and fixes the sealing member 16 to the container 11 by caulking. One end of the positive electrode lead 23 is
4 and the other end is connected to the lower surface of the sealing plate 18.

In such a rectangular nickel-metal hydride secondary battery, the current collection of the negative electrode 15 of the electrode group 12 is performed by bringing the outermost negative electrode 15 into contact with the inner surface of the container 11. The outermost negative electrode 15 has a structure in which the hydrogen storage alloy-containing layer is supported on both surfaces of the conductive substrate as described above, and among the two hydrogen storage alloy-containing layers, the negative electrode 15 contributes to the charge / discharge reaction. This is on the side facing the positive electrode 14 with the separator 13 interposed therebetween, and the hydrogen storage alloy-containing layer in contact with the inner surface of the container 11 hardly contributes to the charge / discharge reaction.

[0005] For this reason, of the hydrogen storage alloy-containing layer of the outermost negative electrode 15, the one in contact with the container 11 is deleted, and the conductive substrate is brought into direct contact with the inner surface of the container 11 to form the negative electrode. Improvement of large current discharge characteristics by increasing current collection efficiency has been performed. Further, it has been studied to improve the charge / discharge characteristics by increasing the volume of other constituent members by the amount of the hydrogen storage alloy-containing layer being removed. For example, increasing the capacity of the positive electrode to increase the capacity or increasing the amount of the alkaline electrolyte to increase the cycle life has been performed.

[0006]

However, a paste containing the hydrogen storage alloy was applied to one side of the conductive substrate having a two-dimensional structure, and the negative electrode having the hydrogen storage alloy-containing layer only on one side was dried. If the paste and the conductive substrate are later manufactured by rolling by, for example, a roller press, there is a problem that the negative electrode is warped because the ductility (elongation rate) differs between the paste and the conductive substrate. The warpage of the negative electrode occurs more remarkably when the press pressure is increased in order to increase the density of the hydrogen storage alloy-containing layer. As a result, when storing the electrode group in the container, the warped negative electrode of the outermost layer is easily rubbed by the container, and the hydrogen storage alloy-containing layer is partially peeled off or chipped, resulting in an internal short circuit and a reduction in the negative electrode capacity. Invite.

By the way, JP-A-10-255834 and JP-A-10-321824 disclose:
There is disclosed a prismatic nickel-metal hydride secondary battery in which a core of a negative electrode in an outermost layer of an electrode group is brought into contact with an inner surface of a container.

According to the present invention, there is provided a method of manufacturing a paste-type hydrogen-absorbing alloy electrode capable of preventing a warp when applying a paste containing a hydrogen-absorbing alloy to one surface of a conductive substrate, drying and applying a pressure. It is intended to provide.

Further, the present invention can smoothly accommodate an electrode group whose outermost surface is a conductive substrate in a container, is excellent in current collection efficiency of a negative electrode, and has a high capacity and a long life. An object of the present invention is to provide a method of manufacturing a prismatic alkaline secondary battery capable of producing a prismatic alkaline secondary battery capable of improving discharge characteristics at a high yield.

[0010]

According to a method of manufacturing a paste-type hydrogen storage alloy electrode according to the present invention, a paste containing a hydrogen storage alloy is applied to one surface of a conductive substrate and dried to form a layer containing the hydrogen storage alloy. Forming, press-forming in a state where the substrate on which the hydrogen storage alloy-containing layer has been formed is superposed such that the surfaces on the conductive substrate side face each other, and forming the hydrogen storage alloy-containing layer superimposed. Peeling off the formed substrate.

The method for manufacturing a prismatic alkaline secondary battery according to the present invention is characterized in that a positive electrode and a negative electrode are alternately laminated via a separator, and an outermost layer is a negative electrode; A negative electrode of the outermost layer has a conductive substrate and a hydrogen storage alloy-containing layer held on one surface of the conductive substrate, and the surface on the conductive substrate side is an inner surface of the container. Forming a hydrogen storage alloy-containing layer by applying a paste containing a hydrogen storage alloy to one surface of a conductive substrate and drying the same, in the method of manufacturing a prismatic alkaline secondary battery disposed in the electrode group so as to be in contact with the electrode group. And the step of forming the hydrogen storage alloy-containing layer-formed substrate,
Pressing the outermost layer with the hydrogen-absorbing alloy-containing layer on which the hydrogen-absorbing alloy-containing layer is formed, and pressing the outermost layer by superposing the outermost layer on the conductive substrate. Is characterized in that the negative electrode is manufactured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a paste-type hydrogen storage alloy electrode according to the present invention will be described.

(First Step) A paste containing a hydrogen storage alloy is applied to one surface of a conductive substrate and dried to form a hydrogen storage alloy-containing layer.

Examples of the conductive substrate include those having a two-dimensional structure such as punched metal, expanded metal, and nickel net.

The paste is prepared, for example, by kneading a hydrogen storage alloy powder, a conductive material and a binder in the presence of water.

As the hydrogen storage alloy, for example, La
Ni _5, MmNi ₅ (Mm is misch metal), LmN
i ₅ (Lm is a La-enriched misch metal), and part of Ni of these alloys is Al, Mn, Co, Ti, Cu, Z
Examples thereof include a multi-element-based compound substituted with at least one element selected from n, Zr, Cr and B. Among them, the general formula LnNi _w Co _x Al _{y M} n _z (provided that
Ln is a rare earth element, atomic ratio w, x, y, and z are respectively 3.30 ≦ w ≦ 4.50, 0.50 ≦ x ≦ 1.10.
0.20 ≦ y ≦ 0.50, 0.05 ≦ z ≦ 0.20,
And the total value is 4.90 ≦ w + x + y + z ≦ 5.50
Is preferably used. More preferable values of the atomic ratio w, x, y, z are 3.80 ≦ w ≦ 4.20, 0.70 ≦ x ≦ 0.90, respectively.
0.30 ≦ y ≦ 0.40, 0.08 ≦ z ≦ 0.13,
And the total value is 5.00 ≦ w + x + y + z ≦ 5.20
It is.

Examples of the binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polytetrafluoroethylene and the like.

As the conductive material, for example, graphite,
Carbon black or the like can be used.

(Second step) Pressure forming is performed in a state where the substrates on which the hydrogen-absorbing alloy-containing layer has been formed are overlapped so that the surfaces on the conductive substrate side face each other.

The pressure molding is performed, for example, by a roller press,
It can be performed by a flat plate press or the like.

It is preferable that the density of the hydrogen storage alloy-containing layer after the pressure molding be in a range of 4.6 g / cm ³ or more.

The pressure molding may be performed after the substrate on which the hydrogen storage alloy-containing layer is formed is cut into a desired size.
Alternatively, it may be cut into a desired size after pressure molding.

(Third Step) By peeling off the superposed substrate on which the hydrogen storage alloy-containing layer is formed, a paste-type hydrogen storage alloy electrode in which the hydrogen storage alloy-containing layer is held on one side of the conductive substrate is obtained.

Hereinafter, a method for manufacturing the prismatic alkaline secondary battery according to the present invention will be described.

(First Step) A positive electrode and a paste-type hydrogen storage alloy negative electrode in which a hydrogen storage alloy-containing layer is held on both surfaces of a conductive substrate are alternately laminated with a separator interposed therebetween. The paste-type hydrogen storage alloy negative electrode manufactured by the above-described method is arranged so that the hydrogen storage alloy-containing layer faces the positive electrode with the separator interposed therebetween to obtain an electrode group.

For the positive electrode, for example, a paste containing an active material containing nickel hydroxide, a conductive agent, a binder and water is prepared, and the paste is filled in a current collector, which is dried and pressed. It is produced by doing. The conductive agent can be added to the paste as a powder or as a coating covering the surface of the active material.

As the active material containing nickel hydroxide as a main component, for example, nickel hydroxide particles, zinc,
Nickel hydroxide particles in which at least one metal selected from cobalt, bismuth and copper is eutectic can be used.

As the conductive agent, for example, at least one selected from cobalt and a cobalt compound can be used. Examples of the cobalt compound include dicobalt trioxide (Co ₂ O ₃ ), cobalt monoxide (CoO), and cobalt hydroxide {Co (OH) ₂ }.

Examples of the binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polytetrafluoroethylene, and polyvinyl alcohol.

The current collector may be a two-dimensional substrate such as a mesh-like, sponge-like, fiber-like, or felt-like porous metal body made of nickel, stainless steel, or nickel-plated metal, or a punched metal. Having irregularities on the periphery of the hole.

A paste type hydrogen storage alloy negative electrode in which a hydrogen storage alloy-containing layer is held on both surfaces of a conductive substrate is prepared by kneading a hydrogen storage alloy powder together with a conductive agent, a binder and water to prepare a paste, for example. The paste is manufactured by applying the paste to both surfaces of a conductive substrate, drying the paste, and then pressing the paste.

As the separator, for example, a nonwoven fabric made of a polyamide fiber or a nonwoven fabric made of a polyolefin fiber such as polyethylene or polypropylene provided with a hydrophilic functional group can be used.

(Second Step) The electrode group is housed in a bottomed rectangular cylindrical metal container also serving as a negative electrode terminal such that the outermost conductive substrate is in contact with the inner surface of the container.

(Third Step) After injecting the alkaline electrolyte into the container, a sealing treatment or the like is performed to obtain a prismatic alkaline secondary battery.

As the alkaline electrolyte, for example, sodium hydroxide (NaOH) and lithium hydroxide (LiO
H), a mixed solution of potassium hydroxide (KOH) and LiOH, a mixed solution of KOH, LiOH and NaOH, and the like.

According to the method of manufacturing the paste-type hydrogen storage alloy electrode according to the present invention described above, the paste containing the hydrogen storage alloy is applied to one surface of the conductive substrate and dried to form the hydrogen storage alloy-containing layer. After that, the hydrogen storage alloy-containing layer-formed substrate is subjected to pressure molding in a state of being overlapped so that the surfaces on the conductive substrate side face each other, so that the hydrogen storage alloy-containing layer is formed on both sides of the conductive substrate. Pressure forming can be performed in the arranged state, and the difference in ductility between the conductive substrate and the hydrogen storage alloy-containing layer at the time of pressing can be reduced, thereby preventing the hydrogen storage alloy electrode from warping. be able to. Next, by peeling off the superposed substrate on which the hydrogen storage alloy-containing layer is formed, a paste-type hydrogen storage alloy electrode in which the hydrogen storage alloy-containing layer is held on one side of the conductive substrate is obtained. Therefore, according to the present invention, it is possible to prevent warpage at the time of press molding in a case where the hydrogen storage alloy-containing layer is held on one surface of the conductive substrate by a simple method.

Further, according to the method of manufacturing a prismatic alkaline secondary battery of the present invention, a separator is interposed between a positive electrode and a paste-type hydrogen storage alloy negative electrode having a hydrogen storage alloy-containing layer on both surfaces of a conductive substrate. After alternately laminating, the paste-type hydrogen storage alloy negative electrode manufactured by the above-described method is disposed on the laminate such that the hydrogen storage alloy-containing layer faces the positive electrode with the separator interposed therebetween to form an electrode group. Since the electrode group is manufactured, the electrode group whose outermost surface is the negative electrode conductive substrate can be smoothly stored in the container, and damage to the hydrogen storage alloy-containing layer during storage can be avoided. Therefore, it is possible to produce a prismatic alkaline secondary battery having excellent current collection efficiency of the negative electrode, high high current discharge characteristics, and capable of improving characteristics such as high capacity and long life at a high yield. it can.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

(Example) <Preparation of paste-type hydrogen storage alloy negative electrode A> 1 part by weight of carboxymethyl cellulose, 3 parts by weight of polytetrafluoroethylene and 1 part by weight of carbon powder were added to 95 parts by weight of hydrogen storage alloy powder, and A paste was prepared by kneading with 50 parts by weight. This paste was applied to one side of a punched metal having a thickness of 60 μm as a conductive substrate and dried to form a hydrogen storage alloy-containing layer. Next, by cutting into a desired size, as shown in FIG. 1A, a substrate having an alloy-containing layer on which a hydrogen-absorbing alloy-containing layer 2 is held on a strip-shaped conductive substrate 1 except for the upper end is formed. One pair was prepared, and the surfaces on the conductive substrate 1 side were opposed to each other.

Next, as shown in FIG. 1B, a pair of substrates on which an alloy-containing layer had been formed were overlapped so that the surfaces on the conductive substrate 1 side face each other, and a roller press 3 was performed. Subsequently, as shown in FIG. 1C, the superposed substrate having the alloy-containing layer formed thereon was peeled off to form a hydrogen-absorbing alloy-containing layer 2 having a density of 5.0 g / cm ^{3 on} one surface of the conductive substrate 1. Was obtained to obtain a paste-type hydrogen storage alloy negative electrode A having a thickness of 0.18 mm. The obtained negative electrode A had no warpage.

<Preparation of Paste Type Hydrogen Storage Alloy Negative Electrode B>
A paste prepared in the same manner as that described for the negative electrode A is applied as a conductive substrate to both surfaces of a punched metal having a thickness of 60 μm, dried, cut into a desired size, and subjected to a roller press. A paste type hydrogen storage alloy negative electrode B having a thickness of 0.3 mm in which a hydrogen storage alloy containing layer having a density of 5.0 g / cm ³ is held on both surfaces of the conductive substrate by applying
I got

Next, as shown in FIG.
mm of a paste-type nickel positive electrode 4 is covered with a separator 5 made of a nonwoven fabric made of hydrophilized polypropylene fiber and having a thickness of 0.15 mm, and such a positive electrode and the negative electrode B are alternately laminated such that the outermost layer becomes a positive electrode. After that, the surface of the negative electrode A on the side of the hydrogen storage alloy-containing layer 2 is
The electrode group 6 having a theoretical capacity of 700 mAh was prepared by arranging the electrode group 6 so as to face the positive electrode 4 with the interposition therebetween.

Subsequently, the electrode group 6 was used as a metal container 7 (having a thickness of 6.1 mm) having a bottomed rectangular cylindrical shape also serving as a negative electrode terminal.
The longer width is 48.0 mm and the shorter width is 17.
0 mm) so that the outermost conductive substrate 1 of the electrode group 6 was in contact with the inner surface on the long side of the container.
Subsequently, a prismatic nickel-metal hydride secondary battery was manufactured by injecting an alkaline electrolyte into the container and performing sealing treatment and the like.

(Comparative Example 1) <Preparation of Paste-Type Hydrogen Storage Alloy Negative Electrode C> A paste prepared in the same manner as in the above-described negative electrode A was prepared by using the same punched metal as described in the above-described negative electrode A. Was coated on one side and dried to form a hydrogen storage alloy-containing layer. Next, after cutting to a desired size, by performing a roller press without performing the above-described superposition, the hydrogen storage alloy-containing layer having the same density as the negative electrode A described above is held on one surface of the conductive substrate. Negative electrode A described above
A paste-type hydrogen storage alloy negative electrode C having a thickness similar to that of the above was obtained.

Next, after the same positive electrode and the negative electrode B as described in the above-described embodiment are alternately laminated so that the outermost layer becomes the positive electrode, the negative electrode C is provided on both sides thereof with the hydrogen-absorbing alloy-containing layer. An electrode group having a theoretical capacity of 700 mAh was prepared by arranging such that the side surface faces the positive electrode with the separator interposed therebetween.

A prismatic nickel-metal hydride secondary battery was manufactured in the same manner as in the above-described embodiment except that such an electrode group was used.

Regarding the secondary batteries of Example and Comparative Example 1,
When the number of damaged (chipped, peeled off from the conductive substrate) layers in the hydrogen-absorbing alloy-containing layer when the electrode group was stored in the container was measured and the defective rate was calculated, the example was 0%. On the other hand, in Comparative Example 1, it was 30%.

An electrode group was prepared in the same manner as in the above-described embodiment except that only a negative electrode having a hydrogen storage alloy-containing layer supported on both surfaces of a conductive substrate was used, and a prismatic nickel-metal hydride secondary battery was assembled. (Comparative Example 2) The rate characteristics were compared with the example. That is, the secondary batteries of Example and Comparative Example 2 were charged at 1 C, -dv (10 mV), and then charged at each rate (1 C, 2 C, 3 C, 4 C, 5 C).
The discharge capacity when 0 V was discharged was measured, and the results are shown in FIG. However, in the secondary battery of Comparative Example 2, when the negative electrode B described in the above example is used as it is, the capacity ratio between the positive electrode and the negative electrode is different from that in the example. The thickness of the hydrogen storage alloy-containing layer was adjusted so as to be similar.

As is apparent from FIG. 4, the secondary battery of the embodiment in which the outermost surface of the electrode group is a conductive substrate is the secondary battery of Comparative Example 2 in which the outermost surface of the electrode group is a layer containing a hydrogen storage alloy. It can be seen that the rate of decrease in the discharge capacity when the discharge rate was increased was lower than that in the case of FIG.

[0050]

As described above, according to the method of manufacturing a paste-type hydrogen storage alloy electrode according to the present invention, a paste containing a hydrogen storage alloy is applied to one surface of a conductive substrate, dried, and then press-formed. There is a remarkable effect that the warpage at the time of performing can be prevented by a simple method. Further, according to the method for manufacturing the prismatic alkaline secondary battery according to the present invention, the outermost surface can be smoothly housed in the container with the electrode group being the negative electrode conductive substrate. A remarkable effect is exhibited, such as a prismatic alkaline secondary battery having high large current discharge characteristics and capable of improving characteristics such as high capacity and long life at a high yield.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a method of manufacturing a paste-type hydrogen storage alloy electrode according to an embodiment.

FIG. 2 is a process chart for explaining a method of manufacturing a prismatic nickel-metal hydride secondary battery of an example.

FIG. 3 is a process chart for explaining a method for manufacturing a prismatic nickel-metal hydride secondary battery of an example.

FIG. 4 is a characteristic diagram showing a relationship between a discharge rate and a discharge capacity in the square nickel-metal hydride secondary batteries of Example and Comparative Example 2.

FIG. 5 is a cross-sectional view showing a conventional prismatic alkaline secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hydrogen storage alloy containing layer, 2 ... Conductive substrate, 3 ... Roller press, 4 ... Positive electrode, 5 ... Separator, 6 ... Electrode group, 7 ... Container.

Claims (2)

[Claims] A step of applying a paste containing a hydrogen storage alloy to one surface of the conductive substrate and drying the paste to form a layer containing the hydrogen storage alloy; Paste-type hydrogen comprising: a step of performing pressure molding in a state where the substrates are overlapped so that the surfaces on the sides are opposed to each other; and a step of peeling off the substrate on which the hydrogen-absorbing alloy-containing layer has been overlapped. Manufacturing method of occlusion alloy electrode. 2. An electrode group comprising a positive electrode and a negative electrode alternately stacked with a separator interposed therebetween, and an outermost layer comprising a negative electrode, and a bottomed rectangular cylindrical container in which the electrode group is housed. The negative electrode has a conductive substrate and a hydrogen storage alloy-containing layer held on one surface of the conductive substrate, and is disposed in the electrode group such that the surface on the conductive substrate side is in contact with the inner surface of the container. Forming a hydrogen-absorbing alloy-containing layer by applying a paste containing a hydrogen-absorbing alloy to one surface of a conductive substrate and drying the paste, and forming the hydrogen-absorbing alloy-containing layer on the conductive substrate. A method comprising the steps of: performing pressure molding in a state where the substrates are superimposed so that the surfaces on the conductive substrate side face each other; and peeling off the superposed hydrogen storage alloy-containing layer-formed substrate. Previous A method for producing a prismatic alkaline secondary battery, comprising producing the negative electrode of the outermost layer.