JP2012054099A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery which has improved safety by suppressing heat generation during an external short circuit without reducing performance in normal use.SOLUTION: A nickel-hydrogen battery has an internal resistance of 70 mΩ or less and comprises a PTC thermistor 20 which is so configured that a temperature rise during an external short circuit of the battery at an ambient temperature of 23±2°C does not exceed 45°C. Since a surface of the PTC thermistor 20 is provided with a flexible protective film 25, the PTC thermistor 20 is protected from an oxygen component and an alkaline component filling a battery case.

Description

  The present invention relates to a battery, and more particularly to a small battery such as an AA battery widely used in the market.

In recent years, small batteries of AA size batteries have been very widely used in the market of electrical appliances and toys. Examples of such small batteries include alkaline storage batteries such as manganese dry batteries, alkaline manganese dry batteries, nickel dry batteries, and nickel metal hydride batteries.
By the way, it is known that in such a small battery, if the battery is externally short-circuited, excessive current flows inside the battery and heat is generated.
Therefore, even when the battery is short-circuited externally, various batteries have been developed that can prevent excessive current by using a resistance element and suppress heat generation (see Patent Documents 1 to 3).

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

However, the batteries as disclosed in Patent Documents 1 to 3 have a problem that the normal use performance of the battery is lowered when the resistance value of the resistance element is high.
In addition, the battery disclosed in Patent Document 2 has a structure in which a resistance element is disposed outside the battery, and thus heat generation outside the battery by the resistance element is large, which is not preferable.
In addition, a PTC (positive temperature coefficient) thermistor as a resistance element is incorporated along with another hard member. However, in this configuration, the expansion change of the insulating polymer in the PTC thermistor is hindered, and an excess current is generated. There is a problem that it cannot be sufficiently prevented and heat generation cannot be sufficiently suppressed.

In addition, in a battery having a structure in which a PTC thermistor is disposed in an electrode group as disclosed in Patent Document 3, there is a concern that heat generated by charging and discharging of the battery may affect PTC physical properties. That is, by arranging the PTC thermistor on the electrode plate 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 becomes close to Trip (resistance increase) by normal charging and discharging. In this case, the PTC thermistor has a problem that the resistance at the initial stage tends to gradually increase during use, and the resistance recovery after Trip deteriorates.
The present invention has been made on the basis of the above-mentioned circumstances, and an object of the present invention is to provide a battery that improves safety by suppressing heat generation during an external short circuit without deteriorating normal use performance. There is.

In order to achieve the above object, the battery of claim 1 is characterized in that the internal resistance is 70 mΩ or less and the temperature rise at the time of external short-circuiting of the battery at an ambient temperature of 23 ± 2 ° C. does not exceed 45 ° C.
A battery according to claim 2 is an AA battery according to claim 1.
A battery according to claim 3 is a nickel-metal hydride battery according to claim 1 or 2.

  A battery according to claim 4 is the nickel hydride battery according to claim 3, further comprising a case having a positive electrode terminal and a negative electrode terminal on an outer surface portion, and a positive electrode plate, a negative electrode plate, and a separator inside the case. And at least one of the terminals and the electrode plate corresponding to the terminal are electrically connected by a conductive member disposed in the case, and the conductive member has a PTC thermistor in a portion exposed to the case space. The PTC thermistor is interposed, and is coated with a protective layer having flexibility to protect from oxygen components and alkali components contained in the gas atmosphere filling the case space.

According to the battery of claim 1, by suppressing the internal resistance of the battery to 70 mΩ or less, the operating voltage at the time of 740 mA discharge during normal battery use is ensured to be 1.20 V or more so as not to deteriorate the normal use performance. In addition, a battery with high safety can be realized by suppressing the temperature rise at the time of external short-circuiting of the battery at an ambient temperature of 23 ± 2 ° C. from exceeding 45 ° C.
According to the battery of claim 2, since the battery is an AA type battery, the AA type battery is very widely used in the market of electrical appliances, toys, etc., and is thus very widely used. The present invention can be suitably applied to a battery.
According to the battery of claim 3, since the battery is a nickel metal hydride battery, the nickel metal hydride battery is very widely used in the market of electrical appliances and toys. The present invention can be preferably applied.

According to the battery of claim 4, when the battery is a nickel metal hydride battery, the resistance value is obtained by combining the structure in which the PTC thermistor is disposed in the case space where the expansion change easily occurs and the structure in which the flexible protective layer is coated. The deterioration of the PTC thermistor due to the oxygen component and the alkali component contained in the gas atmosphere can also be prevented without hindering the expansion change of the PTC thermistor that causes an increase in the temperature.
In this way, by disposing a PTC thermistor coated with a flexible protective layer in the case space of the nickel metal hydride battery, while suppressing the heat generation during an external short circuit without deteriorating normal use performance. A highly safe battery can be realized.

1 is a partially cutaway perspective view showing an overall structure of a nickel metal hydride battery according to an embodiment of the present invention. Sectional drawing which shows the PTC thermistor interposed in the positive electrode tab of the nickel hydride 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 partially cutaway perspective view of a battery applied to the present invention, for example, an AA nickel metal hydride battery which is one of the AA alkaline storage batteries, and FIG. 2 shows the structure of the positive electrode side of the nickel hydrogen battery. An enlarged cross-sectional view is shown. Here, the size of the AA nickel metal hydride battery is 49.2 to 50.5 mm in height and 13.5 to 14.5 mm in outer diameter. In the figure, reference numeral 1 denotes a cylindrical case of a 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 includes, for example, alkaline electrolysis between a strip-shaped positive plate 6 filled with nickel hydroxide particles, for example, a strip-shaped negative plate 7 filled with a hydrogen storage alloy. It is composed of a laminated plate 9 wound in a spiral shape with an insulating separator 8 holding the liquid interposed. Of course, each wound part is insulated with 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 electrode current collecting member 13 is connected to the sealing module 4 via a conductive member, here a positive electrode tab 15, disposed in a case space 2 a formed between the electrode group 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 (positive temperature coefficient) thermistor 20 is interposed in a tab portion of the positive electrode tab 15 arranged in the case space 2a. 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 20 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 the 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 down, 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 charging and discharging, and an alkali component (alkaline) provided by an electrolyte (not shown) in 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 configured in this way has undergone 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 recovers normally (or the battery discharge ends), the resistance value of the PTC thermistor 20 returns to a small 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 FIGS. 2 and 3A and 3B, erosion by the oxygen component of the PTC thermistor itself is prevented. . 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. Protect the erosion of the department.

This is because the protective layer 25 protects the PTC thermistor 20 itself (resin) and the soldered portion 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. The heat generation of the nickel metal hydride battery can be suppressed.
Therefore, the safety of the nickel metal hydride battery can be sufficiently ensured by using the PTC thermistor 20.

Examples of the battery according to the present invention will be given below. In addition, various conventional batteries are listed as comparative examples.
Here, as shown in Table 1 and Table 2 below, change the battery type, internal resistance, presence / absence of PTC thermistor, connection short circuit resistance, operating voltage at 740mA discharge, battery external at ambient temperature 23 ± 2 ° C We investigated the temperature rise at the time of short circuit in the battery, the presence or absence of leakage after the short circuit, and the possibility of reuse after the short circuit. Table 1 shows the case where the connection short circuit resistance is 2.5 mΩ, and Table 2 shows the case where the connection short circuit resistance is 100 mΩ.

<Example 1>
A nickel metal hydride battery having the above-described configuration and having an internal resistance of 25 mΩ was prepared.
<Example 2>
A nickel metal hydride battery having the above-described configuration and having an internal resistance of 70 mΩ was prepared.
<Comparative Example 1>
A nickel-metal hydride battery having a PTC thermistor and an internal resistance of 80 mΩ was prepared.
<Comparative example 2>
A nickel-metal hydride battery having a PTC thermistor and an internal resistance of 130 mΩ was prepared.

<Comparative Example 3>
A nickel-metal hydride battery having no PTC thermistor and an internal resistance of 23 mΩ was prepared.
<Comparative example 4>
An alkaline manganese battery having no PTC thermistor and an internal resistance of 110 mΩ was prepared.
<Comparative Example 5>
A manganese battery having no PTC thermistor and an internal resistance of 400 mΩ was prepared.
<Comparative Example 6>
A nickel battery having no PTC thermistor and an internal resistance of 100 mΩ was prepared.

As described above, according to the first and second embodiments of the battery according to the present invention, the internal resistance was set to 25 mΩ or 70 mΩ, that is, the internal resistance was set to 70 mΩ or less, so that 740 mA discharge during normal battery use was achieved. Operating voltage of 1.20V or more, and the PTC thermistor function enables the ambient temperature to be 23 ± 2 ° C regardless of whether the short circuit resistance is 2.5 mΩ or 100 mΩ. The temperature rise at the time of the external short circuit in can be prevented from exceeding 45 ° C., and the official standard value (for example, ST standard of the Japan Toy Association) can be sufficiently satisfied.
Moreover, according to Examples 1 and 2 of the battery according to the present invention, there is no leakage after short circuit, and re-use after short circuit is possible without any problem.

Therefore, according to the battery of the present invention, a highly safe battery can be realized without deteriorating normal use performance and suppressing heat generation during an external short circuit.
In addition, nickel metal hydride batteries, AA batteries, and particularly AA nickel metal hydride batteries are widely used in the market of electrical appliances and toys. Therefore, the present invention is suitable for such widely used batteries. Can be applied to.
This is the end of the description of the battery according to the present invention, but the present invention is not limited to the above embodiment.
For example, although the case where the battery is a nickel metal hydride battery has been described in the above embodiment, the battery is not limited to the nickel metal hydride battery as long as the same effect as the nickel metal hydride battery can be obtained.

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)

  A battery characterized in that the internal resistance is 70 mΩ or less, and the temperature rise during external short-circuiting at an ambient temperature of 23 ± 2 ° C. does not exceed 45 ° C.   The battery according to claim 1, wherein the battery is an AA size battery.   The battery according to claim 1, wherein the battery is a nickel metal hydride battery. The nickel-metal hydride battery 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 corresponds to at least one terminal and the terminal Conducted between the electrode plates by a conductive member disposed in the case,
The conductive member has a PTC thermistor interposed in a portion exposed to the case space,
4. The battery according to claim 3, wherein the PTC thermistor is coated with a protective layer having flexibility to protect from oxygen components and alkali components contained in a gas atmosphere filling the case space.

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