JP2012054098A - Alkali storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali storage battery which can prevent a positive temperature coefficient (PTC) thermistor from getting degraded by a gas atmosphere (containing oxygen and alkaline components) in a case space without hindering an expansion variation of the PTC thermistor, thanks to the use of a structure designed to place a PTC thermistor in a case space between terminals and electrodes.SOLUTION: In a portion, exposed to a case space 2a, of a conductive member 5a conducting to a terminal 5 on at least one side and a polar plate 6 corresponding to the terminal 5 is a PTC thermistor 20 interposed, the PTC thermistor being coated with a flexible protective layer 25 for protection against oxygen and alkaline components which a gas atmosphere in the case space contains. Thus the PTC thermistor itself and an adhesion section which bonds the PTC thermistor and the conductive member together are guarded against the oxygen and alkaline components contained in the gas atmosphere by the surrounding flexible protective layer. Furthermore, an expansion variation of the PTC thermistor is not hindered. In addition, PTC property or operation is in no way affected.

Description

  The present invention relates to an alkaline storage battery in which a PTC thermistor is interposed in a conductive member that conducts between a terminal on the outer surface of a case and an electrode plate inside the case.

In recent years, in the market of electrical appliances and toys, AA batteries represented by alkaline storage batteries and small batteries such as AA compatible shapes are very widely used. Examples of such a small battery include a cylindrical storage battery such as a manganese dry battery, an alkaline manganese dry battery, a nickel dry battery, and a nickel metal hydride battery.
Such a cylindrical storage battery has a structure in which a positive electrode terminal and a negative electrode terminal are provided on the outer surface portion of the case, and each member constituting an electrode group, that is, a positive electrode plate, a negative electrode plate, and a separator is accommodated inside the case.

By the way, it is known that in such an alkaline battery, if the battery is externally short-circuited, excess current flows inside the battery and heat is generated.
Therefore, many assembled batteries ensure safety by interposing a PTC (positive temperature coefficient) thermistor in the conductive path of the battery pack. This is because the PTC thermistor's characteristic that the electrical resistance increases as the internal temperature of the battery rises is used to prevent a sudden rise in temperature by suppressing the flow of current in the battery and to ensure safety. It is used for. However, only a single battery has such a structure.

  By the way, the PTC thermistor uses, for example, an insulating polymer in which conductive particles are dispersed, and the entire insulating polymer expands due to heat generated when a large current flows due to an external short circuit or the like. The flow of current is suppressed by utilizing the characteristic that the resistance value increases rapidly as the contact decreases. Of course, the insulating polymer contracts when the heat generation is eliminated and it cools down, and returns to a low resistance state again.

  Therefore, a conductive member that conducts the terminal outside the case and the electrode plate inside the case inside the case so that the thermistor characteristics are exhibited, specifically, the positive electrode terminal and the positive plate are conducted as shown in Patent Document 1. It has been studied to interpose a PTC thermistor in a portion of the positive electrode tab exposed to the case space.

  By the way, the case space between the positive electrode terminal where the PTC thermistor is disposed and the positive electrode plate is composed of an oxygen component (high pressure oxygen atmosphere) generated by a chemical reaction during charging and discharging, and an alkali component (alkaline atmosphere) provided by the electrolyte inside the battery. Both are filled with a mixed gas atmosphere.

  However, when the PTC thermistor is exposed to an oxygen atmosphere and an alkali atmosphere, the function of suppressing the current cannot be exhibited due to the influence of the oxygen component and the alkali component. Specifically, the oxygen component in the atmosphere erodes the resin of the PTC thermistor, and the alkaline component erodes the soldered portion (adhesive portion) that bonds the PTC thermistor and the positive electrode tab, deteriorating the PTC thermistor. Or the function is impaired.

  Therefore, a PTC thermistor of the type incorporated in the battery is sandwiched inside a sealing module that forms part of the case of the cylindrical storage battery as in Patent Document 2, or the electrode group electrode of the cylindrical storage battery as in Patent Document 3. In order to protect it from deterioration, it was installed inside the parts outside the case space, such as by providing it on the plate. In order to help protect the PTC thermistor, the entire sealing module and the PTC thermistor of the electrode group are also sealed with a synthetic resin member.

Japanese Patent Laid-Open No. 58-188066 Japanese Patent Laid-Open No. 10-275612 JP 2002-110137 A

  However, since the structure in which the PTC thermistor is incorporated in the electrode plate portion of the sealing module or electrode group as shown in Patent Documents 2 and 3, all are incorporated in a limited area, the PTC thermistor is placed along other hard members. To be incorporated. That is, the periphery of the PTC thermistor tends to be covered with a hard sealing module component, a hard member of an electrode group, or the like. For this reason, the PTC thermistor interferes with these components and members, the expansion change is hindered, and the function of suppressing the flow of current may not be sufficiently exhibited.

  In particular, in the structure in which the PTC thermistor is arranged in the electrode group of the battery as in Patent Document 3, there is a concern that heat generated by charging / discharging of the battery affects the PTC physical properties. That is, by arranging the PTC thermistor in the electrode portion, the PTC thermistor becomes close to a heating element, and is affected by temperature due to charging / discharging of the battery. For this reason, the PTC thermistor is close to the Trip (resistance increase reaction) temperature during normal charging and discharging. In such a case, the PTC thermistor is subject to a tendency that the initial resistance gradually increases during use, and there is a concern that the resistance recovery after Trip deteriorates.

Moreover, with the structure in which the PTC thermistor is arranged in the electrode portion, even if the positive electrode tab generates heat during a short circuit, there is a distance from the positive electrode tab to the inside of the electrode group in which the PTC thermistor is arranged. Takes time, and even if the positive electrode tab becomes Trip temperature and the PTC thermistor trips, there is a concern that the separator on the path may be melted by heat and the electrode plate may come into contact with the PTC thermistor. There is a possibility that the function to secure cannot be demonstrated.
For this reason, it is difficult to maintain the reliability of the PTC thermistor and ensure the safety of the battery by the PTC thermistor.

  Accordingly, an object of the present invention is to provide a case space between the terminal and the electrode plate in order to ensure the reliability of the PTC thermistor with a structure that does not easily change the expansion of the PTC thermistor and does not affect the physical properties and operation of the PTC. An alkaline storage battery that uses a structure in which a PTC thermistor is disposed in the PTC thermistor and prevents deterioration of the PTC thermistor due to a gas atmosphere (including oxygen and alkali components) in the case space without disturbing the expansion change of the PTC thermistor. There is to do.

In order to achieve the above object, according to the present invention, a PTC thermistor is interposed in a portion of a conductive member that conducts at least one terminal and a corresponding electrode plate and is exposed to a case space. The thermistor is coated with a flexible protective layer that protects the oxygen component and the alkali component contained in the gas atmosphere in the case space.
With this configuration, the PTC thermistor is easily expanded, and the PTC thermistor is disposed on the conductive member in the case space so that it does not affect the physical properties of the PTC or affect the resistance recovery. The thermistor itself or the bonded portion where the PTC thermistor and the conductive member are bonded is protected from oxygen components and alkali components contained in the gas atmosphere. In addition, the PTC thermistor does not hinder changes in expansion due to the flexible protective layer, so that the performance is sufficiently exhibited.

According to the second aspect of the present invention, a positive electrode tab that conducts between the positive electrode terminal and the positive electrode plate is used as the conductive member so as to be most easily used in an alkaline storage battery.
In addition to the above object, the invention of claim 3 further includes a flexible oxygen-resistant protective layer covering the periphery of the PTC thermistor, and a protective layer, so that the PTC thermistor can be sufficiently protected with a simple structure. A multilayer structure having a flexible alkali-resistant protective layer covering the oxygen protective layer was used.

  In addition to the above-mentioned object, the oxygen-resistant protective layer is coated with an epoxy resin member around the PTC thermistor so that a flexible oxygen-resistant protective layer and alkali-resistant protective layer can be easily obtained. The alkali-resistant protective layer was formed by pasting and covering a plurality of polypropylene tapes around the coat layer of the epoxy resin member.

According to the first aspect of the present invention, the combination of the structure in which the PTC thermistor is arranged in the case space that is easily changed in expansion and does not affect the physical properties and operation of the PTC, and the structure in which the film is coated with a flexible protective layer. The deterioration of the PTC thermistor caused by the oxygen component and the alkali component contained in the gas atmosphere can be prevented without impeding the expansion change of the PTC thermistor that causes an increase in resistance value, and further without affecting the PTC thermistor. .
Therefore, the safety in the alkaline storage battery can be sufficiently secured by using the PTC thermistor.

According to the second aspect of the present invention, a structure that prevents the deterioration of the PTC thermistor can be used in the most frequently used alkaline storage battery. In particular, since the PTC thermistor is disposed in the case space between the vacant positive electrode terminal and the positive electrode plate, the use of the unused case space can be expected to increase the capacity and performance of the battery. .
According to the invention of claim 3, the PTC thermistor can be sufficiently protected with a simple multilayer structure in which a flexible oxygen-resistant protective layer and a flexible alkali-resistant protective layer are used.
According to the fourth aspect of the present invention, the oxygen-resistant protective layer and the alkali-resistant protective layer can be easily formed by a simple operation, and deterioration of the PTC thermistor can be easily prevented.

The figure for demonstrating the cylindrical storage battery which concerns on one Embodiment of this invention. Sectional drawing which shows the PTC thermistor interposed in the positive electrode tab of the cylindrical storage battery. The perspective view which shows the protection structure of the PTC thermistor.

Hereinafter, the present invention will be described based on an embodiment shown in FIGS.
FIG. 1 shows a perspective view of an alkaline storage battery to which the present invention is applied, for example, a partially cut cylindrical nickel-metal hydride battery, and FIG. 2 shows an enlarged sectional view of the structure on the positive electrode side of the nickel-metal hydride battery. Yes. In the figure, reference numeral 1 denotes a cylindrical case of the nickel-metal hydride battery.
As shown in FIGS. 1 and 2, the case 1 includes a conductive cylindrical outer can 2, and a conductive disc-shaped sealing module 4 provided to close the opening of the outer can 2 (various members 4 ) And an annular insulating member 3 that insulates the opening edge of the outer can 2 from the outer peripheral portion of the sealing module 4. Case 1 is sealed.

  An electrode group is housed inside the outer can 2 constituting the case 1. As shown in FIGS. 1 and 2, the electrode group is, for example, a strip-shaped positive plate 6 filled with nickel hydroxide particles (positive electrode active material), for example, a strip-shaped positive plate filled with hydrogen storage alloy (negative electrode active material). It is composed of a laminated plate 9 wound in a spiral shape with an insulating separator 8 holding an alkaline electrolyte interposed between the negative electrode plate 7 and the negative electrode plate 7. Each part wound is insulated by an insulating member 9a so as not to be short-circuited. And the current collection terminal 7a formed in the side edge part of the negative electrode plate 7, the lower edge part of the negative electrode plate 7 here is electrically connected with the exterior can 2 via the plate-shaped negative electrode current collection member 10. . Thus, the negative electrode terminal 12 is formed on the bottom surface portion of the outer can 2.

  As shown in FIGS. 1 and 2, the current collecting terminal 6a formed on the side edge of the positive electrode plate 6, here the upper edge of the positive electrode plate 6, is a plate-shaped positive current collecting member having a through hole 13a. 13 is conducted. The positive electrode current collecting member 13 is a component that is assembled at a point immediately above the electrode group. The positive current collecting member 13 is connected to the sealing module 4 via a conductive member, here a positive electrode tab 15, disposed in the case space 2 a formed between the battery element and the sealing module 4. Thus, the convex portion 4 a formed at the center of the outer surface of the sealing module 4 is used as the positive electrode terminal 5. In the convex portion 4 forming the positive electrode terminal 5, there is incorporated a safety valve 16 for releasing the gas when the internal pressure of the battery is raised to a predetermined pressure or higher. In the figure, 16a indicates a valve body of the safety valve 16, and 16b also indicates a spring. The safety valve 16 is not a spring valve type but may be a valve structure other than that such as a rubber valve type, and may be a safety valve structure that allows gas to escape.

  As shown in FIGS. 1 and 2, a thin plate-like PTC thermistor 20 is interposed in the tab portion of the positive electrode tab 15 disposed in the case space 2 a. Specifically, the positive electrode tab 15 is separated from the central portion, for example. That is, the positive electrode tab 15 is divided into an inverted L-shaped tab portion 15 a extending from the positive electrode current collecting member 13 and a U-shaped tab portion 15 b extending from the sealing module 4. A PTC thermistor 20 is disposed between the separated tip portions of the tab portions 15a and 15b. The upper and lower surface portions (side portions) of the overlapping PTC thermistor 20 and the tip portions of the tab portions 15a and 15b are connected by bonding, for example, soldering, and the PTC thermistor 20 is interposed in the positive electrode tab 15 in series. is doing. In particular, the PTC thermistor 20 is fixed to a pair of metal plates (not shown) that form the tips of the tab portions 15a and 15b and the terminals of the PTC thermistor 20 as shown in FIG. ) Is soldered with the solder 22 through the nickel thin film 21.

  The PTC thermistor uses, for example, an insulating polymer in which conductive particles are dispersed. Now, due to the heat generated when a large current flows, such as an external short circuit, the entire insulating polymer expands, and due to the expansion, the contact of conductive particles decreases and the resistance value increases rapidly. Suppresses current flow. Note that the insulating polymer contracts when the heat generation is eliminated and it cools, and returns to a state of low resistance again.

  The PTC thermistor 20 disposed in the case space 2a has an environment in which expansion changes easily occur because there are no hard parts or members that cause interference in the immediate vicinity. Further, the PTC thermistor 20 is also in an environment in which it is difficult to affect the physical properties of the PTC or the operation. On the other hand, the PTC thermistor 20 includes a gas atmosphere filled in the case space 2a, specifically, an oxygen component (high pressure oxygen atmosphere) generated by a chemical reaction during charge / discharge and an alkali component (alkaline) provided by an electrolyte (not shown) inside the battery. Since both are exposed to a mixed gas atmosphere, there is a risk of deterioration.

  Therefore, the PTC thermistor 20 is provided with means for preventing the PTC thermistor 20 from deteriorating without impairing or affecting the function of the thermistor 20. For this means, as shown in FIGS. 1 and 2, a structure in which the PTC thermistor 20 is coated with a flexible protective layer 25 and the PTC thermistor 20 is protected from oxygen and alkali components in the gas atmosphere is used. It has been. A detailed protection structure of the PTC thermistor 20 is shown in FIGS. 2 and 3 (a) and 3 (b). In order to make the film structure easy to understand, each part of the protective layer 25 is shown slightly enlarged in the figure.

  Explaining the protective structure, as shown in FIG. 2 and FIG. 3A, the protective layer 25 includes an oxygen resistant protective layer 27 that covers the periphery of the PTC thermistor 20 and withstands oxygen components in the gas atmosphere. The multi-layer structure is formed with an alkali-resistant protective layer 29 that is provided so as to cover the oxygen-resistant protective layer 27 and can withstand an alkali component in a gas atmosphere. More specifically, the oxygen-resistant protective layer 27 has a structure in which, for example, a flexible epoxy resin member 27a [shown only in FIG. 3B] is applied around the PTC thermistor 20 including the overlapping tab portions. That is, the oxygen-resistant protective layer 27 is formed by a coat of an epoxy resin member 27a that covers the entire PTC thermistor 20 including the tab portion. Of course, other synthetic resin members other than the epoxy resin member 27a may be used as long as they are flexible and have a characteristic to withstand oxygen components.

  The alkali-resistant protective layer 29 is made of, for example, a flexible polypropylene thin film tape 30, here two polypropylene tapes 30 [shown in FIG. 3 (b)], and the coating layer of the epoxy resin member 27 a from above and below. A structure is used in which the entire periphery of the coat layer of the epoxy resin member 27a is covered by being sandwiched. That is, the alkali resistant protective layer 29 is formed of a polypropylene tape layer. Needless to say, other than the tape 30 but also a polypropylene coat, other flexible and alkali-resistant members such as nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 6T, nylon 9T, nylon M5T, nylon You may form with nylon-type members, such as 612, a polyamide-type resin, alkali-resistant rubber, a mineral synthetic resin (asphalt), etc.

  It is assumed that the nickel-metal hydride battery (alkaline storage battery) configured as described above has an external short circuit (or excessive large current charge / discharge), for example. Then, the PTC thermistor 20 expands the entire insulating polymer due to heat generated when a large current flows at the time of the short circuit, reduces the contact of the conductive particles, and rapidly increases the resistance value. Here, since the expansion of the insulating polymer is performed in the case space 2a where there is no hard member that interferes with the surroundings, it quickly rises to the required resistance value. Thereby, the flow of current is suppressed and heat generation of the battery is prevented. If the current is restored normally (or the battery discharge is completed), the resistance value of the PTC thermistor 20 returns to a low state again.

  At this time, the inside of the case space 2a is filled with a gas atmosphere in which both an oxygen component (high-pressure oxygen atmosphere) generated by a chemical reaction during charging and discharging and an alkali component (alkaline atmosphere) provided by the electrolyte in the battery are mixed. Therefore, there is a concern that the PTC thermistor 20 itself (resin) and the adhesion part (soldering part) of the PTC thermistor 20 are eroded by the component.

  Here, since the entire PTC thermistor 20 is covered with the oxygen-resistant protective layer 27 as shown in FIG. 2 and FIGS. 3A and 3B, the erosion of the PTC thermistor itself (resin) by the oxygen component is not caused. Protected. Further, since the periphery of the oxygen-resistant protective layer 27 is covered with the alkali-resistant protective layer 29, the oxygen-resistant protective layer 27 is protected from erosion by an alkaline component, and is soldered to bond the PTC thermistor 20 and the tab portion. Protects against erosion of the part (adhesive part).

This is because the protective layer 25 protects (protects) the PTC thermistor 20 itself (resin) and the soldered part (adhesive part) of the PTC thermistor 20 from oxygen components and alkali components contained in the gas atmosphere. Moreover, since the protective layer 25 has flexibility, it is not necessary to prevent the expansion change of the PTC thermistor 20.
Therefore, the PTC thermistor 20 is easy to change in expansion, and is arranged between the case space 2a which does not affect the PTC physical properties and does not affect the resistance recovery, and the coating by the flexible protective layer 25. From the combination, it is possible to sufficiently exhibit the performance of suppressing a large current without being affected by oxygen components and alkali components contained in the gas atmosphere that fills the case space 2a, and further without affecting PTC physical properties and operation. it can.

  Therefore, deterioration of the PTC thermistor 20 is prevented, and the safety of the nickel metal hydride battery (alkaline storage battery) can be sufficiently secured by the PTC thermistor 20. The PTC thermistor 20 covered with such a protective layer 25 is suitable for an alkaline storage battery (particularly a nickel metal hydride battery) having many structures in which the positive electrode tab 15 is disposed in the case space 2a. Moreover, the PTC thermistor 20 is disposed in the case space 2a between the vacant positive electrode terminal 5 and the positive electrode plate 6, so that the capacity of the battery is further increased by using the unused case space 2a. Contributes to higher performance.

  In addition, since the protective layer 25 has a multi-layer structure formed of an oxygen resistant protective layer 27 covering the PTC thermistor 20 and an alkali resistant protective layer 29 covering the oxygen resistant protective layer 27, a simple structure is used. That's okay. In particular, the oxygen-resistant protective layer 27 is formed by a coating of an epoxy resin member 27a, and the alkali-resistant protective layer 29 is formed by laminating a plurality of polypropylene tapes 30, and each layer can be easily formed. Degradation of the PTC thermistor 20 can be prevented.

  Note that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the spirit of the present invention. For example, in one embodiment, a protective layer having a two-layer structure is used. However, the present invention is not limited to this, and a multilayer protective layer or a single protective layer to which various protective components are added may be used. In one embodiment, an example in which a PTC thermistor is interposed in the positive electrode tab has been described. However, the present invention is not limited thereto, and in the case of an alkaline storage battery including a negative electrode tab, the structure of the PTC thermistor and the protective layer may be applied to the negative electrode tab. I do not care. In one embodiment, a battery structure having a positive electrode current collecting member has been described. However, a battery structure in which a positive electrode tab is directly attached to a positive electrode plate without using the positive electrode current collecting member may be used. Moreover, although this invention was applied to the nickel metal hydride battery, you may apply this invention not only to this but another alkaline storage battery.

DESCRIPTION OF SYMBOLS 1 Case 2a Case space 5 Positive electrode terminal 6 Positive electrode plate 7 Negative electrode plate 8 Separator 12 Negative electrode terminal 15 Positive electrode tab (conductive member)
20 PTC thermistor 25 Protective layer 27 Oxygen resistant protective layer 29 Alkali resistant protective layer

Claims (4)

It has a case with a positive electrode terminal and a negative electrode terminal on the outer surface, and a positive electrode plate, a negative electrode plate and a separator are accommodated in the case, and the case is between the at least one terminal and the electrode plate corresponding to the terminal. An alkaline storage battery that is conducted by a conductive member disposed therein,
The conductive member has a PTC thermistor interposed in a portion exposed to the case space,
The alkaline storage battery, wherein the PTC thermistor is coated with a protective layer having flexibility to protect from an oxygen component and an alkali component contained in a gas atmosphere filling the case space.   The alkaline storage battery according to claim 1, wherein the conductive member is a positive electrode tab that conducts between the positive electrode terminal and the positive electrode plate.   The protective layer has a multilayer structure including a flexible oxygen resistant protective layer covering the periphery of the PTC thermistor and a flexible alkali resistant protective layer covering the oxygen resistant protective layer. The alkaline storage battery according to claim 1 or 2, wherein the alkaline storage battery is provided. The oxygen resistant protective layer is formed by coating an epoxy resin member around the PTC thermistor,
The alkaline storage battery according to claim 3, wherein the alkali-resistant protective layer is formed by laminating and covering a plurality of polypropylene tapes around a coat layer of the epoxy resin member.

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