JP2002260623A - Sealed battery and manufacturing method of battery seal member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery having little dispersion of valve operation pressure and high reliability. SOLUTION: The sealed battery is provided with a container 1; a power generation element stored in the container 1; a sealing plate 7 disposed at an opening of the container 1 and opened with a gas removal hole 9; an electrode terminal disposed so as to surround the gas removal hole 9 of the sealing plate 7; an elastic valve element 8 disposed in a space surrounded by the electrode terminal and the sealing plate 7 and closing the gas removal hole 9 by a surface 14 contacted with the sealing plate 7. It is characterized that in the elastic valve element 8, an area, faced to at least the gas removal hole and a periphery edge of the gas removal hole, of the surface 14 contacted with the sealing plate 7 curved outwardly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery and a method for manufacturing a battery sealing member.

[0002]

2. Description of the Related Art A sealed alkaline storage battery typified by a nickel cadmium storage battery or a nickel hydride storage battery is frequently used as a power supply for a portable electronic device. When this sealed alkaline storage battery is exposed to abnormal conditions such as misuse such as overcharging or throwing it into fire,
There is a danger that the internal pressure will rise sharply due to gas generation accompanying the battery reaction. For this reason, sealed alkaline storage batteries are required to discharge gas inside in response to pressure rise due to gas generation inside the battery, and to prevent rupture of metal outer cans and popping out of sealing bodies. Is provided.

[0003] As a gas discharge mechanism, it is preferable to use a return type in which the valve is opened to release the gas to the outside when the internal pressure of the battery reaches a predetermined value or more, and thereafter, it can be closed again. As a sealed alkaline storage battery having a return-type gas discharge mechanism, those in which a gas discharge mechanism is provided in a sealing member are frequently used.Specifically, a container, and a power generation element housed in the container, A sealing plate disposed at the opening of the container, and having a gas exhaust hole, an electrode terminal disposed on the sealing plate so as to surround the gas exhaust hole, the electrode terminal and the sealing plate. There is known an elastic valve body which is disposed in a compressed state in an enclosed space and closes the gas exhaust hole of the sealing plate. FIG. 6 shows an example of the elastic valve element. The elastic valve element 21 has a columnar shape and has a flange 22 at one end. End face 23 of elastic valve element 21
Is in contact with the sealing plate and has a planar shape.

[0004] The above-mentioned sealing member having a return type gas discharge mechanism is, for example, after an elastic valve body is housed in an electrode terminal,
The sealing plate is placed on the electrode terminal, and the sealing plate is attached to the electrode terminal by, for example, welding or caulking. According to such a method, the sealing member can be easily assembled.

[0005]

However, according to the elastic valve element 21 in which the surface 23 in contact with the sealing plate has a planar shape, the displacement of the sealing plate and the displacement of the electrode terminal caused when assembling the sealing member are caused. Since the stress applied to the elastic valve body 21 tends to fluctuate due to the deviation of the position of the elastic valve body or the variation of the sitting state in the above, there arises a problem that the variation of the valve operating pressure increases. If the valve operating pressure moves to the high pressure side, it tends to burst when the internal pressure rises sharply due to the delay of the gas discharge timing. Cause a decrease in

On the other hand, it has been proposed to form a cylindrical projection 24 in a region of the end face 23 of the elastic valve body 21 which faces the gas vent hole of the sealing plate. Since the stress applied to the elastic valve body 21 is likely to fluctuate due to the displacement of the sealing plate or the elastic valve body, the variation in the valve operating pressure is large.

An object of the present invention is to provide a highly reliable sealed battery having less variation in valve operating pressure.

An object of the present invention is to provide a method for manufacturing a battery sealing member having a small variation in valve operating pressure.

[0009]

A sealed battery according to the present invention has a container, a power generating element housed in the container, and a gas vent hole disposed in an opening of the container. A sealing plate, an electrode terminal disposed so as to surround the gas vent hole of the sealing plate, and a gas vent disposed on a surface surrounded by the electrode terminal and the sealing plate and in contact with the sealing plate. In a sealed battery comprising an elastic valve element closing a hole, the elastic valve element has a surface facing at least the gas vent hole and a peripheral edge of the gas vent hole in a surface in contact with the sealing plate. It is characterized by being curved outward.

The method for manufacturing a battery sealing member according to the present invention is characterized in that an electrode terminal having a cap-shaped terminal portion, a sealing plate having a gas vent hole, and at least a part of a surface in contact with the sealing plate are provided. Preparing an elastic valve body that is curved outward, a step of housing the elastic valve body in the terminal portion of the electrode terminal, and the gas vent hole and the peripheral edge of the gas vent hole on the electrode terminal. A step of arranging the gas vent hole of the sealing plate with the elastic valve body so as to face the curved portion of the elastic valve body, and fixing the sealing plate to the electrode terminal. It is a feature.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cylindrical alkaline secondary battery which is an example of a sealed battery according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a cross-sectional view of an essential part showing an example of a cylindrical alkaline secondary battery according to the present invention, FIG. 2 is a cross-sectional view showing an elastic valve body of a sealing member of the secondary battery of FIG. 1, and FIG. Sectional view for explaining a method of assembling a sealing member of a secondary battery,
FIG. 4 is a cross-sectional view and a plan view showing another example of the elastic valve body of the sealing member of the secondary battery of FIG.

That is, an electrode group 5 formed by spirally winding a positive electrode 2 and a negative electrode 3 in a cylindrical metal container 1 having a bottom also serving as a negative electrode terminal with a separator 4 interposed therebetween. Is stored. The negative electrode 4 includes:
It is arranged at the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. Therefore, the power generation elements including the electrode group 5 and the alkaline electrolyte are accommodated in the container 1.

A sealing member 6 provided with a gas discharge mechanism is disposed at an upper opening of the container 1. The sealing member 6
Includes a sealing plate 7, a positive electrode terminal, and an elastic valve body 8.
The sealing plate 7 has a circular shape and is concave near the center, and a circular vent hole 9 is opened in the concave portion. The positive electrode terminal has a cap-shaped terminal portion 10 and a flange portion 11 extending to a lower end of the terminal portion 10. The plurality of gas discharge holes 12
It is open near the boundary between the terminal portion 10 and the flange portion 11. The positive electrode terminal is arranged on the sealing plate 7 such that the terminal portion 10 surrounds the gas vent hole 9 of the sealing plate 7. The elastic valve element 8 is
It is cylindrical and has a flange 13 at one end. Collar 13
Is a member for positioning the elastic valve element 8 in the positive electrode terminal portion 10. The end surface 14 of the elastic valve element 8 is curved outward so that the maximum protruding portion C exists in a region facing the gas vent hole 9, and has a hemispherical curved surface in FIGS. 1 and 2. . The elastic valve element 8 is arranged in a compressed state in a space formed by fixing the positive electrode terminal and the sealing plate 7, and a maximum protruding portion (central portion) C of the outwardly curved end face 14 is closed. The gas vent hole 9 is closed so as to face the gas vent hole 9 of the plate 7. The elastic valve element 8 is
For example, it can be formed from a rubber-based material containing a terpolymer (EPDM) of an ethylene-propylene-non-conjugated diene compound. The elastic valve body 8 formed of this rubber-based material has advantages of being excellent in alkali resistance and durability, hardly causing cracks, and having excellent heat resistance due to its high softening point. Ring-shaped insulating gasket 15
Is disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate 7 is connected to the container 1 through the gasket 15 by caulking to reduce the diameter of the upper opening inward. And airtightly fixed.

One end of the strip-shaped positive electrode lead 16 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 7.

An example of a method of assembling the sealing member 6 having the gas discharge mechanism will be described with reference to FIG. That is, the positive electrode terminal is placed with the terminal portion 10 facing down, and the elastic valve body 8 is stored in the terminal portion 10 with the flange portion 13 facing down. Next, the sealing plate 7 is arranged on the flange portion 11 of the positive electrode terminal, and the gas vent hole 9 of the sealing plate 7 is opposed to the central portion C of the curved surface 14 of the elastic valve body 8. Closed by body 8,
The elastic valve body 8 was pressurized by the sealing plate 7 to be in a compressed state, and a resilient elastic force was generated in the elastic valve body 8. Subsequently, while the compressed state of the elastic valve body 8 is maintained, the flange 11 of the positive electrode terminal and the sealing plate 7 are integrated by welding to obtain a sealing member 6 having a gas discharge mechanism. In FIG. 3 described above, the positive electrode terminal and the sealing plate are fixed by welding, but the positive electrode terminal and the sealing plate can be fixed by caulking.

According to the cylindrical alkaline secondary battery as described above, the end face 14 of the elastic valve body 8 is curved outward so that the maximum protruding portion C exists in a region facing the gas vent hole 9. Therefore, the compressive stress can be concentrated on a portion of the elastic valve body 8 facing the gas vent hole 9 and in the vicinity thereof. As a result, when the sealing plate 7 is fixed to the positive electrode terminal in a slightly inclined state, or when the elastic valve body 8 in the terminal portion 10 of the positive electrode terminal is displaced, the fluctuation of the compressive stress is reduced. Sealing plate 7 and elastic valve element 8
Irrespective of the presence or absence of the position shift, an appropriate valve operating pressure can always be maintained.

Therefore, when exposed to an abnormal environment such as misuse such as overcharging or throwing into a fire and generating gas and the internal pressure rises sharply, the elastic valve body 8 can be pushed up quickly. Gas can be released to the outside through the gap created between the pushed-up elastic valve element 8 and the sealing plate 7, the gap between the sealing plate 7 and the positive electrode terminal, and the gas discharge hole 12 of the positive electrode terminal. 1 may burst or the sealing member 6
It is possible to prevent accidents such as blowing away. In addition, the valve does not operate at the time of slight gas generation without danger of rupture, and leakage of the alkaline electrolyte can be prevented, so that an excellent charge / discharge cycle life can be secured.

Further, after the elastic valve element 8 is accommodated in the terminal portion 10 of the positive electrode terminal, the sealing plate 7 is formed on the positive electrode terminal so that the gas vent hole 9 and its peripheral edge face the curved surface 14 of the elastic valve element 8. When the sealing member 6 having a gas discharge mechanism is obtained by a method of closing the gas vent hole 9 of the sealing plate 7 with the elastic valve body 8 and fixing the sealing plate 7 to the positive electrode terminal, the sealing plate 7 is inclined. In this state, it is likely to be fixed to the positive electrode terminal or the position of the elastic valve element 8 in the terminal portion 10 is likely to be shifted. Can be manufactured with good mass productivity.

In FIGS. 1 to 3 described above, an example in which the end face 14 of the elastic valve body 8 is curved outward has been described. For example, as shown in FIG. 14 can be used in which only the gas vent hole 9 of the sealing plate 7 and the region X facing the periphery thereof are curved outward.

In FIGS. 1 to 3 described above, the number of gas vent holes 9 in the sealing plate 7 is one, but it is possible to use two or more.

Further, in FIGS. 1 to 4 described above, an example in which the present invention is applied to a cylindrical alkaline secondary battery has been described, but the sealed battery according to the present invention is not limited to such a structure.
For example, the present invention can be similarly applied to a rectangular alkaline secondary battery in which a laminate including a positive electrode and a negative electrode and a separator disposed between the positive electrode and the negative electrode is housed in a bottomed rectangular cylindrical container. However, in the cylindrical alkaline secondary battery, the cap-shaped terminal portion 10 of the positive electrode terminal has a round shape, whereas in the square alkaline secondary battery, the cap-shaped terminal portion has a square shape. It is desirable that the flange of the valve body be rectangular in accordance with the shape of the terminal.

Hereinafter, the positive electrode, the negative electrode, the separator, and the alkaline electrolyte will be described.

1) Positive electrode A positive electrode containing nickel hydroxide as an active material can be used.

The positive electrode 2 is manufactured by, for example, a method described below.

A paste is prepared by kneading the nickel hydroxide powder, a conductive material, a binder, and water as necessary, and after filling the conductive substrate with the paste, drying and rolling. Obtain a positive electrode.

As the nickel hydroxide powder, a nickel hydroxide powder in which at least one metal selected from zinc and cobalt is eutectic, or a non-eutectic nickel hydroxide powder can be used.

A conductive layer containing cobalt oxyhydroxide (CoOOH) can be formed on the surface of the nickel hydroxide. When a conductive layer is formed, a conductive material need not be added to the paste.

Examples of the conductive material include metallic cobalt and cobalt compounds (for example, cobalt oxides such as CoO and cobalt hydroxides such as Co (OH) ₂ ).
And the like. As the conductive material, one or more selected from the above-described types can be used. The conductive material may be added to the paste in the form of powder or a layered material covering the surface of the nickel hydroxide powder. To the paste, both a nickel hydroxide powder whose surface is coated with a conductive material and a powder of a conductive material may be added.

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

As the conductive substrate, for example, a two-dimensional substrate such as a mesh-like, sponge-like, fiber-like, or felt-like porous metal body or a punched metal made of nickel, stainless steel, or nickel-plated metal is used. Having irregularities on the periphery of the hole.

2) Negative electrode As the negative electrode, for example, a cadmium electrode or a hydrogen storage alloy electrode can be used. Among them, it is preferable to use one containing a hydrogen storage alloy.

A negative electrode containing a hydrogen storage alloy is prepared by, for example, kneading a hydrogen storage alloy powder, a conductive material and a binder in the presence of water to prepare a paste, filling the paste into a conductive substrate, and drying the paste. After that, it is produced by applying a press.

The hydrogen storage alloy preferably contains at least a rare earth element and nickel. One or more kinds of rare earth elements can be used. Among them, rare earth elements include La, Pr, Ce,
One or more elements selected from Nd and Sm are preferred.

Examples of the hydrogen storage alloy containing at least a rare earth element and nickel include LaNi ₅ , MmNi
₅ (Mm is misch metal), LmNi ₅ (Lm is La
Enriched misch metal), and multi-element materials in which part of Ni of these alloys is replaced with at least one element selected from Al, Mn, Co, Ti, Cu, Zn, Zr, Cr and B be able to. Among them, the general formula LmN
_{i v Co w Mn x Al y} Zr z ( However, Lm is at least one more rare earth elements, the atomic ratio v, w, x, y and z
Are expressed as 5.0 ≦ v + w + x + y + z ≦ 5.4). In particular, L
m preferably contains La. Among them, La, P
Those containing r, Ce and Nd are preferred.

The average particle size of the hydrogen storage alloy powder is 20
It is preferable to set the range to 70 μm.

Examples of the binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene, polyvinyl alcohol (PVA), and styrene butadiene rubber (SB).
R) and the like.

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

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

3) Separator Examples of the separator include a nonwoven fabric made of polyamide fiber, a nonwoven fabric made of polyolefin fiber such as polyethylene and polypropylene, or a nonwoven fabric provided with a hydrophilic functional group.

4) Alkaline Electrolyte As the alkaline electrolyte, for example, a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
A mixture of potassium hydroxide (KOH) and LiOH, KOH
And a mixed solution of LiOH and NaOH.

[0041]

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

(Example 1) A steel flat plate was pressed and then nickel-plated to obtain the structure shown in FIG. 1 described above. A sealing plate 7 having a thickness of 0.6 mm and a gas vent hole 9 having a diameter of 1.8 mm was opened in the portion.

On the other hand, after kneading a mixture containing an organic peroxide, a vulcanization accelerator and a processing aid in addition to EPDM as a main component, the mixture is press-molded at about 170 ° C. to obtain the above-mentioned mixture. An elastic valve body 8 having the structure shown in FIG. 2, having a cylindrical shape with a diameter R of 5 mm, having a flange 13 at one end, and having a hemispherical curved end surface 14 was obtained. The height H of the central portion (maximum protruding portion) C of the elastic valve body 8 was 2.5 mm, and the height h of the end portion was 2.3 mm. Further, the hardness of the elastic valve body 8 was set to 79 degrees.

A positive electrode having the above-described structure shown in FIG. 1 was obtained by pressing a flat steel plate having a thickness of 0.3 mm and then performing nickel plating on the surface.

Next, the positive electrode terminal was placed with the terminal portion 10 facing down, and the elastic valve element 8 was housed in the terminal portion 10 with the flange portion 13 facing down. Next, the sealing plate 7 is arranged on the flange 11 of the positive electrode terminal, and the gas vent hole 9 of the sealing plate 7 is
The gas vent hole 9 of the sealing plate 7 was closed by an elastic valve body 8 in a state where the gas vent hole 9 was opposed to the maximum projecting portion C of No. 4, and the elastic valve body 8 was pressurized by the sealing plate 7 to be in a compressed state. Subsequently, the flange 11 of the positive electrode terminal is maintained while the compressed state of the elastic valve body 8 is maintained.
And the sealing plate 7 were integrated by resistance welding to obtain a sealing member 6 having a gas discharge mechanism.

(Comparative Example) After kneading a mixture containing an organic peroxide, a vulcanization accelerator and a processing aid in addition to EPDM as a main component, the mixture was subjected to pressure molding at about 170 ° C. An elastic valve body 21 having the structure shown in FIG. 6 was obtained. That is, the elastic valve body 21 had a cylindrical shape with a diameter R of 5 mm, had a flange 22 at one end, and had a planar end face 23. The height of the elastic valve body 21 is 2.
5 mm. Further, the hardness of the elastic valve body 21 was set to 79 degrees.

Next, the same positive electrode terminal as that described in Example 1 was placed with the terminal portion 10 facing down, and the elastic valve body 21 was housed in the terminal portion 10 with the flange portion 22 facing down. Subsequently, a sealing plate 7 similar to that described in the first embodiment is arranged on the flange portion 11 of the positive electrode terminal, and the gas vent hole 9 of the sealing plate 7 is closed with the end surface 23 of the elastic valve body 21. The elastic valve body 21 was pressurized to a compressed state. Subsequently, while the compressed state of the elastic valve body 21 was maintained, the flange 11 of the positive electrode terminal and the sealing plate 7 were integrated by resistance welding to obtain a sealing member having a gas discharge mechanism.

With respect to the obtained sealing members of Example 1 and Comparative Example, the valve operating pressure (the internal pressure of the battery at which the elastic valve body operates) was measured at an ambient temperature of 25 ° C., and the results are shown in FIG. In FIG. 5, the horizontal axis represents the valve operating pressure (MPa), and the vertical axis represents the number of batteries having a specific valve operating pressure.

As is apparent from FIG. 5, the sealing member of the first embodiment having the elastic valve body whose surface in contact with the sealing plate is curved outward has a valve operating pressure distribution range of 2.40 to 3.00 M.
It can be seen that the distribution range of the valve operating pressure is 1.80 to 3.50 MPa for the sealing member of the comparative example including the elastic valve body having a flat surface in contact with the sealing plate, while the pressure is Pa. Moreover, the sealing member of Example 1 is 2.60 to 2.70 MPa.
It can be seen that the measurement frequency at 2.60 MPa to 2.70 MPa is less than 40, while the measurement frequency at 2.60 to 2.70 MPa is less than 40. From these results, Example 1
It can be seen that the sealed battery provided with the sealing member of the above can reduce the variation of the valve operating pressure as compared with the comparative example.

(Example 2) In addition to EPDM as a main component, a mixture containing an organic peroxide, a vulcanization accelerator and a processing aid was kneaded, followed by pressure molding at about 170 ° C. An elastic valve body 8 having the structure shown in FIG. 4 was obtained. That is, the elastic valve element 8 has a cylindrical shape with a diameter R of 5 mm, has a flange 13 at one end, and has a circular area facing the gas vent hole 9 of the sealing plate 7 and the peripheral edge of the end face 14. Only X was curved outward. The curved region X was a hemispherical curved surface, and the diameter r of the curved region X was 3 mm. The height H of the central portion (maximum protruding portion) C of the elastic valve body 8
Was 2.5 mm, and the height h at the end was 2.3 mm.
Further, the hardness of the elastic valve body 8 was set to 79 degrees.

Next, the same positive electrode terminal as that described in Example 1 was placed with the terminal portion 10 facing down, and the elastic valve body 8 was housed in the terminal portion 10 with the flange portion 13 facing down. Continued,
The sealing plate 7 similar to that described in the first embodiment is disposed on the flange 11 of the positive electrode terminal, and the gas vent hole 9 of the sealing plate 7 and the periphery thereof are opposed to the curved region X of the elastic valve body 8 to vent the gas. The hole 9 was closed with an elastic valve element 8, and the elastic valve element 8 was pressed by the sealing plate 7 to be in a compressed state. Subsequently, while maintaining the compressed state of the elastic valve body 8, the flange portion 11 of the positive electrode terminal and the sealing plate 7 were integrated by resistance welding to obtain a sealing member 6 having a gas discharge mechanism.

When the valve operating pressure of the obtained sealing member of Example 2 was measured at an ambient temperature of 25 ° C., the distribution range of the valve operating pressure was 2.10 to 3.10 MPa, which was smaller than that of the comparative example. Could be smaller.

[0053]

As described above, according to the sealed battery of the present invention, it is possible to reduce variations in valve operating pressure, satisfy both safety and life characteristics, and improve reliability. It has remarkable effects such as improvement. Further, according to the method for manufacturing a battery sealing member according to the present invention, a remarkable effect is obtained such that a highly reliable sealing member having a small variation in valve operating pressure can be obtained by a simple method.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a cylindrical alkaline secondary battery as an example of a sealed battery according to the present invention.

FIG. 2 is a sectional view showing an elastic valve body of a sealing member of the secondary battery of FIG.

FIG. 3 is a sectional view for explaining a method of assembling the sealing member of the secondary battery of FIG. 1;

FIG. 4 is a schematic view showing another example of the elastic valve body of the sealing member of the secondary battery of FIG. 1;

FIG. 5 is a characteristic diagram showing a distribution of a valve operating pressure for the sealing members of Example 1 and Comparative Example.

FIG. 6 is a sectional view showing an elastic valve body of a sealing member of a comparative example.

FIG. 7 is a cross-sectional view showing a conventional elastic valve body of a sealing member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Separator, 5 ... Electrode group, 7 ... Sealing plate, 8 ... Elastic valve body, 9 ... Gas vent hole, 10 ... Positive electrode terminal part, 11 ... Flange part, 12 ... gas discharge holes, 13 ... flanges, 14 ... outwardly curved surfaces, 15 ... insulating gaskets.

Claims (2)

[Claims] 1. A container, a power generating element housed in the container, a sealing plate arranged at an opening of the container and having a gas vent hole, and a gas vent hole of the sealing plate. A hermetically sealed valve comprising: an electrode terminal disposed so as to surround; and an elastic valve element disposed in a space surrounded by the electrode terminal and the sealing plate and closing the gas vent hole on a surface in contact with the sealing plate. In the sealed battery, the elastic valve body is characterized in that at least a region facing a periphery of the gas vent hole and the gas vent hole in a surface in contact with the sealing plate is curved outward. battery. 2. An electrode terminal having a cap-shaped terminal portion, a sealing plate having a gas vent hole, and an elastic valve body having at least a part of a surface in contact with the sealing plate curved outward. Preparing and storing the elastic valve body in the terminal portion of the electrode terminal; and forming the sealing plate on the electrode terminal such that the gas vent hole and the periphery thereof face the curved portion of the elastic valve body. And a step of closing the gas vent hole of the sealing plate with the elastic valve body, and fixing the sealing plate to the electrode terminal.