JP3715243B2 - Square alkaline storage battery and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a prismatic alkaline storage battery and a method for manufacturing the same, and more particularly to a thin prismatic alkaline storage battery and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, with the rapid progress of portable and cordless devices, there is an increasing demand for secondary batteries that are small, lightweight, and have high energy density. In particular, in the audio market using a square battery as a main power source, particularly an MD player, the playback time exceeds a maximum of 100 hours, and it is not important to further increase the capacity of the battery. In the future, thinning of the battery will be particularly important, and the spread of lithium secondary batteries that can be easily thinned is promoted.
[0003]
However, if the alkaline storage battery represented by nickel-hydrogen storage battery or nickel-cadmium storage battery can be made thin like a square lithium ion battery, it will take advantage of its low cost and high reliability, and the lithium secondary battery will be used in the market. Differentiation from the secondary battery can be achieved. In these alkaline storage batteries, in consideration of the balance between the positive electrode capacity and the negative electrode capacity and the battery characteristics, the negative electrode plate disposed outside the electrode plate group is brought into contact with the battery case.
[0004]
[Problems to be solved by the invention]
However, since the conventional prismatic alkaline storage battery is provided with a gas discharge mechanism on the positive electrode terminal side, the structure of the sealing plate on the positive electrode terminal side is complicated and is composed of many parts (generally eight or more points). For this reason, if a new metal mold is produced for each component of the sealing plate in order to make the battery thinner, a great investment is generated, and the design change of the battery is not easy.
[0005]
Further, in the conventional prismatic alkaline storage battery, the sealing plate on the positive electrode side is sealed by laser welding. However, since the area of the upper part of the battery is not sufficient when performing laser welding, a gasket or the like containing nylon as a main component is used. The insulating material may be deformed by the influence of laser heat. For this reason, there is a possibility that the electrolytic solution leaks from a gap generated by the deformation of the sealing insulator during charging and discharging of the battery.
[0006]
In order to solve the above-described problems, an object of the present invention is to provide a low-cost and highly reliable thin prismatic alkaline storage battery and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a prismatic alkaline storage battery according to the present invention includes a prismatic case having one open end, a cap formed on the other end opposite to the one end of the case, A prismatic alkaline storage battery comprising an arranged electrode plate group and a sealing plate that seals the one end, the electrode plate group comprising a positive electrode plate, a negative electrode plate, and a separator, wherein the negative electrode and the case are in contact with each other. The cap portion includes a gas exhaust port and a safety valve and functions as a negative electrode terminal. The sealing plate and the positive electrode plate are electrically connected to each other, and the sealing plate is coated with a resin at the outer periphery. The case is sealed by caulking the case at a portion where the sealing plate is disposed, and the one end is bent in a dogleg shape toward the resin. . In the present specification, “rectangular alkaline storage battery” means an alkaline storage battery using a rectangular parallelepiped case or a rectangular parallelepiped case with rounded corners.
[0008]
Moreover, the manufacturing method of the prismatic alkaline storage battery of the present invention is as follows.
(I) producing an electrode plate group comprising a positive electrode plate and a negative electrode plate that are alternately stacked with a separator interposed therebetween so that the negative electrode plate is positioned at both ends;
(Ii) inserting the electrode plate group into a rectangular case whose one end is an open end having a stepped portion ;
( Iii ) placing a metal sealing plate functioning as a positive electrode terminal, the outer peripheral portion of which is coated with a resin, on the stepped portion;
( IV ) sealing the one end with the sealing plate by bending the one end of the case into a U -shape toward the resin while squeezing a portion protruding by the step portion on the outer surface of the case ;
Forming a cap portion having a gas exhaust port and a safety valve at the other end opposite to the one end of the case and functioning as a negative electrode terminal.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
(Embodiment 1)
Embodiment 1 demonstrates an example about the prismatic alkaline storage battery of this invention. A schematic cross-sectional view of the prismatic alkaline storage battery 10 of Embodiment 1 is shown in FIG.
[0011]
The prismatic alkaline storage battery 10 includes a case 11, a cap portion 12, an electrode plate group 13 (illustration of a cross section is omitted), and a sealing plate 14.
[0012]
The case 11 has a rectangular shape (a rectangular parallelepiped shape or a rectangular parallelepiped shape with rounded corners). The case 11 is usually made of a conductive metal. One end 11a of the case 11 is opened. Further, a gas vent hole 11h is formed at the other end of the case 11 opposite to the one end 11a. In the case 11, it is preferable that the shape of the cross section perpendicular to the longitudinal direction (the direction connecting the positive electrode terminal and the negative electrode terminal) is a rectangular shape with rounded corners (hereinafter sometimes referred to as an oval cross section). . By using the case having such a shape, the reliability when the case 11 is caulked and sealed can be improved.
[0013]
The cap portion 12 is formed in the gas vent hole 11 h of the case 11. The cap unit 12 includes a cap 12a formed with a gas exhaust port (not shown) and a safety valve. When the internal pressure of the battery rises above a certain value, the gas inside the battery is released through the gas vent hole 11h and the gas exhaust port 12. Although FIG. 1 shows a case where the safety valve is a rubber valve body 12b as an example, the structure of the safety valve is not limited to this. The cap 12a is formed of a conductive metal, and the cap portion 12 functions as a negative electrode terminal.
[0014]
The electrode plate group 13 includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate and the negative electrode plate are laminated with the separator interposed therebetween so that the negative electrode plate is located at both ends. Such a laminated body can be formed, for example, by alternately laminating positive and negative plates that are coated with separators on both sides. The laminate may be formed by bending a negative electrode plate that is twice as long as the positive electrode plate and placing the positive electrode plate therebetween. The negative electrode plates disposed at both ends of the electrode plate group are electrically connected to the cap portion 12 which is a negative electrode terminal by contacting the case 11. The positive electrode plate, the negative electrode plate, and the separator are selected according to a battery to be manufactured (for example, a nickel-cadmium storage battery or a nickel-hydrogen storage battery), and can be manufactured using a known material.
[0015]
The sealing plate 14 seals one end 11 a of the case 11. FIG. 1 shows a case where a sealing plate 14 made of a metal flat plate 14b whose outer peripheral portion is coated with a resin 14a is used as an example of the sealing method. In this case, the case 11 can be sealed by caulking the case 11 at the portion where the sealing plate 14 is disposed. The sealing plate 14 and the positive electrode plate are electrically connected by a metal tab 15. As shown in FIG. 1, an insulating frame 16 is preferably disposed between the electrode plate group 13 and the sealing plate 14 so that the electrode plate group 13 and the sealing plate 14 do not contact each other. The sealing method is not limited to the method shown in FIG. For example, the outer periphery of the one end 11a of the case 11 may be covered with a resin, and the case 11 may be crimped by placing a sealing plate on a portion where the resin is formed.
[0016]
In the prismatic alkaline storage battery of Embodiment 1, the number of components of the sealing plate can be reduced because the gas discharge mechanism is not formed in the portion that seals the case. Further, in this battery, the negative electrode terminal can be formed by welding a cap into which a valve body functioning as a safety valve is inserted into the case. Furthermore, in this battery, sealing can be easily performed by caulking the case in which the sealing plate is inserted. For this reason, the prismatic alkaline storage battery of the first embodiment can be easily changed in design and manufactured at low cost with high productivity. In addition, unlike the conventional prismatic alkaline storage battery that seals by laser welding, this prismatic alkaline storage battery has no damage to the sealing part due to heat, so that liquid leakage does not occur even after repeated charge and discharge cycles, In addition, the reliability when stored for a long time can be improved.
[0017]
(Embodiment 2)
Embodiment 2 demonstrates an example about the manufacturing method of the square alkaline storage battery of this invention. In addition, what was demonstrated in Embodiment 1 can be used for the structural member of the battery used in Embodiment 2. FIG.
[0018]
In the manufacturing method of Embodiment 2, first, an electrode plate group including a positive electrode plate and a negative electrode plate that are alternately stacked with separators interposed therebetween so that the negative electrode plate is positioned at both ends is prepared (step (i)). Specifically, for example, after covering both surfaces of the positive electrode plate with a separator, the negative electrode plate and the positive electrode plate may be alternately laminated. The positive electrode plate is, for example, an active material made of a metal oxide and kneaded with water and a water-soluble binder to produce an active material paste, and a strip-like sponge-like metal having a space in which the paste is three-dimensionally connected. It can be formed by filling a porous body, drying and pressing, and then cutting it into a predetermined size. The negative electrode plate can be formed, for example, by applying a paste containing a hydrogen storage alloy to a core material such as a punching metal, drying and pressing, and then cutting to a predetermined size.
[0019]
Next, the electrode plate group is inserted into a rectangular case with one end opened (step (ii)). The negative electrodes located at both ends of the electrode plate group are in contact with the case. As the case, the case 11 described in the first embodiment can be used.
[0020]
Next, one end (opening) of the case is sealed with a sealing plate that functions as a positive electrode terminal (step (iii)). Sealing can be performed by the method described in the first embodiment. Usually, a step of connecting a metal tab connected to the positive electrode terminal to the sealing plate before the sealing is performed.
[0021]
Finally, after injecting an electrolytic solution from the degassing hole 11h of the case 11, a battery is obtained by forming the cap portion 12 at the other end of the case 11. The step of injecting the electrolytic solution and forming the cap portion is not necessarily performed in the last step.
[0022]
According to the manufacturing method of Embodiment 2, the prismatic alkaline storage battery described in Embodiment 1 can be easily manufactured. In this manufacturing method, unlike a conventional manufacturing method in which sealing is performed by laser welding of a sealing plate, a battery that is not affected by deformation of the sealing portion due to heat can be manufactured.
[0023]
【Example】
Hereinafter, an example of manufacturing a prismatic nickel-hydrogen storage battery will be described as an example of the present invention.
[0024]
The positive electrode plate was produced by the following method. First, 100 parts by weight (parts by weight) of nickel hydroxide and 0.2 parts by weight of carboxymethyl cellulose as a binder were added with water so as to be 25% by weight of the total paste, and kneaded to obtain a paste-like positive electrode An active material was prepared. The paste-like active material was filled into a nickel sponge substrate and dried, and then pressed to increase the packing density, and cut into a width of 15 mm, a thickness of 0.8 mm, and a length of 55 mm to produce a positive electrode plate. Thereafter, ultrasonic waves were applied to the positive electrode plate to peel off the active material on the upper side of the electrode plate with a width of 2 mm, and then a tab (nickel lead) having a thickness of 80 μm was welded to the peeled portion. Thus, the positive electrode plate 22 to which the tab 21 was connected was produced. This positive electrode plate 22 was covered with a separator 23 mainly composed of polypropylene with the tab 21 extended, and its outer peripheral end was sealed by thermal welding. In this way, a positive electrode plate 22 whose both surfaces were coated with the separator 23 was produced.
[0025]
The negative electrode plate 24 was produced by applying a paste containing a hydrogen storage alloy powder to a core material made of punching metal and cutting it to a width of 15 mm, a thickness of 0.2 mm, and a length of 113 mm. The negative electrode plate 24 was folded in two, and the positive electrode plate 22 sealed with the separator 23 was sandwiched between them to produce an electrode plate group 25.
[0026]
As shown in FIG. 2A, the electrode plate group was inserted into a case 26 having a gas vent hole 26h. As the case 26, a rectangular case made of nickel-plated iron and having an elliptical cross section (outer dimensions: horizontal 17 mm, vertical 65 mm, thickness 4 mm) was used.
[0027]
Thereafter, as shown in FIG. 2B, a resin frame 27 and a flat plate (sealing body) 28 also serving as a positive electrode terminal were inserted below the electrode plate group, and then the opening was crimped to seal. The outer periphery of the flat plate 28 is covered with resin, and the tab 21 and the flat plate 28 are welded before sealing. The sealing is performed by squeezing the opening 26a whose end is processed as shown in FIG. 3 (a) using a die 31 from the degassing hole 26h side of the case 26 as shown in FIG. 3 (b). As shown in c), the case end was bent into a dogleg shape.
[0028]
Thereafter, after alkaline electrolyte solution is vacuum-injected from the gas vent hole 26h of the case 26, the cap 29a having the rubber valve element 29b inserted therein is placed around the gas vent hole 26h of the case 26 as shown in FIG. Resistance welded. In this way, a rectangular nickel-hydrogen storage battery of the present invention (hereinafter also referred to as battery A) having an HF17 / 67 size and a nominal capacity of 800 mAh was produced.
[0029]
On the other hand, as a comparative example, a rectangular nickel-hydrogen storage battery (hereinafter also referred to as battery B) was produced using a conventional sealing method. The battery B uses a conventional battery case whose bottom is not opened. As shown in FIG. 4, the opening of the case 41 is sealed with a conventional sealing plate 42 having a gas discharge mechanism. Sealing was performed by laser welding the sealing plate 42 to the case 41 after connecting the positive electrode plate and the sealing plate 42 with a nickel lead.
[0030]
In order to compare the battery A of the present invention with the battery B of the comparative example, 50 pieces of each were produced. After the initial charge and discharge for each of the battery A and battery B, in order to confirm the leakage resistance, the battery A and the battery B are left in a constant temperature bath at a temperature of 65 ° C. and a humidity of 90%, and a long-term reliability test is performed in a high temperature humidified state It was. The result is shown in FIG.
[0031]
As is clear from FIG. 5, in the battery B of the comparative example, the leakage reaction was confirmed 2% after about 2 weeks from the start of standing, and 6% after 35 days. On the other hand, in the battery A of the present invention, a battery in which a liquid leakage reaction was observed even after 35 days from standing was not confirmed.
[0032]
When the battery B of the comparative example in which the liquid leakage reaction was confirmed was investigated, dissolution of the insulator in the sealing portion was observed, and the liquid leakage reaction was confirmed from this site. In this comparative example, when the sealing plate was welded with a laser, the gasket that insulates the positive electrode terminal was melted by the influence of the heat of the laser and the confidentiality was impaired. Moreover, when the diameter of the nugget connecting the battery case and the lid body was reduced during laser welding, a pinhole was generated conversely, and the generation of the pinhole could not be suppressed by changing the setting of the laser welding conditions.
[0033]
In the battery A of the example, since no laser is used, there is no harmful effect seen in the battery B of the comparative example, and the reliability is also compared with the battery B from the result of the long-term reliability test. There was no leakage reaction and the confidentiality was greatly improved. This is because, in the battery A, the compressibility of the case end that is crimped to the square shape and the flat plate covered with the insulator is maintained, and in particular, the case at the corner portion by making the battery case elliptical in cross section. It is considered that the secrecy is significantly improved as compared with the battery B of the comparative example.
[0034]
Although the embodiments of the present invention have been described above by way of examples, the present invention is not limited to the above-described embodiments, and can be applied to other embodiments based on the technical idea of the present invention.
[0035]
【The invention's effect】
As described above, in the prismatic alkaline storage battery and the manufacturing method thereof according to the present invention, a gas discharge mechanism is provided on the negative electrode terminal side to form a convex terminal portion, and sealing is performed with a flat sealing plate. As a result, the number of components can be greatly reduced as compared with a conventional sealing plate having a gas discharge mechanism, and a battery that can be easily changed in design and manufactured at low cost is obtained. Further, since the battery of the present invention does not require thermal welding using a laser at the time of sealing, sealing is easy and damage to the sealing plate due to the heat of the laser can be prevented.
[0036]
Therefore, according to the present invention, it is easy to reduce the thickness to a level (6 mm or less) that does not exist in a conventional prismatic alkaline storage battery, and it is a low-cost and long-term reliable thin that can be differentiated even in a lithium ion-based market. Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a prismatic alkaline storage battery of the present invention.
FIG. 2 is a perspective view schematically showing an example of a method for producing a prismatic alkaline storage battery of the present invention.
3 is a schematic cross-sectional view showing an example of a step of the manufacturing method shown in FIG. 2. FIG.
FIG. 4 is a perspective view of a prismatic alkaline storage battery of a comparative example.
FIG. 5 is a graph showing the results of long-term reliability tests for the prismatic alkaline storage batteries of the present invention and comparative examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Square alkaline storage battery 11, 26 Case 11a One end 11h, 26h Gas vent hole 12 Cap part 12a, 29a Cap 12b, 29b Rubber valve body 13, 25 Electrode plate group 14 Sealing plate 14a Resin 14b Flat plate 15, 21 Tab 16, 27 Frame Body 22 Positive electrode plate 23 Separator 24 Negative electrode plate 28 Flat plate (sealing body)

Claims (4)

A rectangular case having one end opened, a cap portion formed on the other end opposite to the one end of the case, an electrode plate group disposed in the case, and a sealing plate for sealing the one end A prismatic alkaline storage battery comprising:
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator,
The negative electrode and the case are in contact with each other;
The cap portion includes a gas exhaust port and a safety valve and functions as a negative electrode terminal,
The sealing plate and the positive electrode plate are electrically connected ;
The sealing plate is a metal flat plate whose outer periphery is coated with a resin,
The case is sealed by caulking the case at a portion where the sealing plate is disposed,
The one end is a prismatic alkaline storage battery that is bent in a dogleg shape toward the resin .   2. The prismatic alkaline storage battery according to claim 1, wherein the positive electrode plate and the negative electrode plate are alternately stacked with the separator interposed therebetween so that the negative electrode is located at both ends. The prismatic alkaline storage battery according to claim 1 or 2 , wherein the sealing plate and the positive electrode plate are electrically connected by a metal tab. (I) producing an electrode plate group comprising a positive electrode plate and a negative electrode plate that are alternately stacked with a separator interposed therebetween so that the negative electrode plate is positioned at both ends;
(Ii) inserting the electrode plate group into a rectangular case whose one end is an open end having a stepped portion ;
( Iii ) placing a metal sealing plate functioning as a positive electrode terminal, the outer peripheral portion of which is coated with a resin, on the stepped portion;
( IV ) sealing the one end with the sealing plate by bending the one end of the case into a U -shape toward the resin while squeezing a portion protruding by the step portion on the outer surface of the case ;
A method of manufacturing a prismatic alkaline storage battery, comprising: forming a cap portion having a gas exhaust port and a safety valve at the other end opposite to the one end of the case and functioning as a negative electrode terminal.

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