JP2005243414A - Sealed storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed storage battery, having a switching mechanism capable of interrupting and connecting charge current using a simple and compact structure due to changes in pressure in the interior of a battery during charge, and capable of suppressing boost in the internal pressure during rapid charging, suppressing an electrolyte solution from flying off to the outside of a system, as well as being superior in cycle characteristics. <P>SOLUTION: A sealed storage battery incorporates a switching mechanism, that performs switching ON and OFF of a circuit establishing a connection between a polar plate and an external terminal due to changes in the pressure in the interior of a storage battery during charge. The switching mechanism comprises a metallic sealing pad, and a connection terminal, and the sealing pad and the external terminal are insulated with an electrical insulating film. Normally, by the fact that the connecting terminal abuts both of the sealing pad and the external terminal, the switching mechanism is at ON state. When the pressure in the interior of the storage battery rises, electrical energization is interrupted by the fact that the connecting terminal is away from the sealing pad and the external terminal. As a result, the charge circuit of the storage of the circuit turns ON/OFF. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sealed storage battery, and has a built-in switch mechanism for controlling on / off of a circuit connecting an electrode plate and an external terminal in accordance with a change in gas pressure inside the storage battery, and is suitable for rapid charging. It is about.

Secondary batteries mainly used as power sources for portable devices include alkaline storage batteries such as nickel cadmium batteries and nickel hydride storage batteries, small sealed lead batteries, and lithium ion batteries. In particular, alkaline storage batteries are frequently used as storage batteries for cycle services because of their excellent cycle characteristics and excellent overcharge resistance and overdischarge resistance.
It is desired that charging be completed in a short time according to the user's request, and in particular, it is desired to develop a sealed storage battery adapted to rapid charging for a cycle service storage battery. In order to meet this requirement, a sealed storage battery that can complete charging in an unprecedented short time of 15 to 30 minutes has been developed.

  FIG. 4 is a cross-sectional view showing the internal structure of a conventional cylindrical alkaline storage battery 31. As shown in FIG. 4, when the gas pressure inside the storage battery rises, cap holes 32 that also serve as external terminals of the positive electrode and the sealing plate 33 have through holes 34 and 35 for releasing the gas accumulated therein. In general, the through hole 35 provided in the sealing plate 33 is hermetically sealed by the rubber valve 36. When the pressure inside the storage battery rises, the rubber valve 36 is pushed upward by the pressure, and the gas accumulated inside is discharged through the opening of the through hole 35 (pressure release mechanism). When the gas is discharged to the outside and the pressure inside the storage battery drops, the through hole 35 is sealed again by the rubber valve 36. In addition, 37 of FIG. 4 is a gasket for airtightly sealing the open end of a battery case. In the case of a nickel cadmium battery or a nickel metal hydride storage battery, a mechanism is adopted in which oxygen and hydrogen generated during charging are absorbed by an electrode plate. However, when the charging of the conventional sealed battery shown in FIG. 4 is completed in 15 to 30 minutes, the pressure release mechanism frequently operates because the absorption rate of the gas during charging cannot catch up with the generation rate, The water that constitutes the electrolyte becomes a gas and diffuses outside. Moreover, since the heat generation inside the storage battery is large during charging, the temperature of the storage battery rises, causing a decrease in performance of the storage battery.

  In order to improve the drawbacks of the conventional battery, as shown in FIG. 3, a sealed storage battery having a built-in switch mechanism for controlling on / off of a circuit connecting an electrode plate and an external terminal in accordance with a change in gas pressure inside the storage battery. 21 has been proposed. (For example, see Patent Document 1)

  In the sealed storage battery shown in FIG. 3, an electrode group is housed in the battery case 30, and a positive electrode plate 38 constituting the electrode group and a cap 29 serving as an external terminal of the positive electrode include a positive electrode lead plate 39 and a connection terminal 23. The connection terminal 23 is electrically connected via the first terminal 24 of the switch 22 and the second terminal 25 of the switch 22. The open end of the battery case 30 is hermetically sealed by a grommet 26 which is a molded body of a thermoplastic resin and a connection terminal 23 fitted in a through hole 27 provided in a central portion of the grommet 26. Normally, the first terminal 24 is pressed downward by the stress derived from the elastic deformation of the elastic body 28, the first terminal 24 and the second terminal 25 are in contact with each other, and the switch 22 is in an on state. When the pressure inside the storage battery (the gas pressure accumulated inside the storage battery) rises and exceeds a predetermined value during charging, the central portion of the grommet 26 bends upward, and the first terminal 24 of the switch 22 rises upward along with the bending. The switch 22 is turned off by moving away from the second terminal 25, and charging is temporarily interrupted. Thus, the sealed storage battery in which the storage battery is provided with a charge control function for turning on / off charging according to the pressure change inside the battery at the time of charging has an effect of suppressing an increase in battery temperature during charging.

However, according to the configuration described in Patent Document 1, a grommet 26 having a complicated structure is required instead of the gasket in order to hermetically seal the storage battery. In addition, it is necessary to secure a bending allowance of the grommet between the thin portion of the grommet 26 and the second terminal 25 of the switch, and there is a disadvantage that the volume occupied by the switch becomes large. In addition, when the thin portion of the grommet 26 does not bend uniformly, the first terminal 24 of the switch does not move in the vertical direction, so that it tilts with respect to the second terminal of the switch, and the two terminals abut and detach. There was a risk that the switch would not function properly. Furthermore, there is a possibility that the airtightness of the contact surface between the grommet 26 and the connection terminal 23 may be impaired due to repeated bending of the grommet.

  The present invention was made in view of the drawbacks of the conventional sealed storage battery, and is a storage battery having a switch mechanism capable of cutting off and energizing a charging current due to a pressure change inside the battery during charging, It is an object of the present invention to provide a sealed storage battery having a simple and compact structure that can suppress an increase in pressure inside the storage battery when rapid charging is performed.

This invention solves the said subject by making the structure of the switch mechanism and sealing of a sealed storage battery into the following structures.
The sealed storage battery according to the present invention is a sealed storage battery having a built-in switch mechanism that switches on and off a charging circuit that connects an electrode plate and an external terminal due to a pressure change inside the storage battery during charging. The sealing plate is composed of a metal sealing plate and a connection terminal, and the sealing plate and the external terminal are insulated from each other by an electrical insulating layer. Normally, the connection terminal is in contact with both the sealing plate and the external terminal, so that the switch When the mechanism is on and the internal pressure of the storage battery rises, the electrical connection between the sealing plate and the external terminal is cut off when the connection terminal is separated from the sealing plate, so that the charging circuit of the storage battery is turned on. It is a sealed storage battery that switches off. (Claim 1)

In the sealed storage battery according to the present invention, the side wall inner surface of the external terminal is perpendicular to the sealing plate, the connection terminal is columnar, the side surface abuts on the side wall inner surface of the external terminal, and is connected. 2. The sealed storage battery according to claim 1, wherein the terminal is slidable with respect to the side wall of the external terminal. (Claim 2)
The sealed storage battery according to the present invention is the sealed storage battery according to claim 2, wherein a gas discharge hole is provided in a wall surface of the external terminal. (Claim 3)
In the sealed storage battery according to the present invention, an airtight holding layer for keeping the space in the external terminal airtight is disposed on the inner surface of the external terminal, and the airtight holding layer is ruptured to cause the airtight holding layer to pass through the through hole. The sealed storage battery according to claim 3, wherein the gas can be discharged to the outside. (Claim 4)

According to the first and second aspects of the invention, a switch mechanism capable of cutting off and energizing a charging current by a pressure change inside the battery during charging, which is simple, compact and reliable. A sealed storage battery having a high switch mechanism can be provided.
According to the third aspect of the present invention, in the sealed storage battery provided with the switch mechanism, when the pressure inside the storage battery rises abnormally, the gas accumulated in the storage battery passes through the space in the external terminal. Since the gas is discharged to the outside, the gas ejection speed can be reduced, and the electrolyte can be prevented from blowing out together with the gas. In the present invention, the abnormal increase in the internal pressure of the storage battery means a phenomenon in which the pressure has exceeded the operating pressure of the switch mechanism.
According to a fourth aspect of the invention, there is provided a sealed storage battery having the switch mechanism and having excellent airtightness, and when the pressure inside the storage battery rises abnormally, the gas accumulated in the storage battery is quickly discharged. A sealed storage battery that can be discharged to the outside can be realized.

The embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a cross-sectional view of a main part of a battery for explaining a switch mechanism of a cylindrical sealed storage battery according to an embodiment of the present invention.
In FIG. 1 (a), a cap-shaped positive electrode exterior is connected to an upper open end of a metal battery case 8 containing a wound electrode group (not shown) in which a laminate of a positive electrode plate, a separator and a negative electrode plate is wound. A flange portion 2 of a terminal (hereinafter referred to as a cap) 1, a metal sealing plate 3 which is a second terminal of the switch, and an electrical insulation inserted between the flange portion 2 and the sealing plate 3 in order to insulate them. The gasket 4 which is the molded body of the film 4 and the thermoplastic resin is attached, and the end portion of the battery case 8 is caulked to be hermetically sealed (crimp seal).
The cross-section of the cap 1 is such that the inner surface of the side wall forms a straight line perpendicular to the sealing plate 3, and the space surrounded by the cap 1 and the sealing plate 3 (hereinafter referred to as the space inside the cap) is a metal that is the first terminal of the switch. A connection terminal 5 made of metal is arranged. The side surface of the connection terminal 5 is in airtight contact with the inner surface of the side wall of the cap 1 and is slidable in the vertical direction in FIG. A positive electrode lead plate 10 having the other end bonded to the positive electrode plate (not shown) is bonded to the inner surface of the sealing plate 3.

  A through-hole through which the connection terminal 5 can be inserted is provided in the central portion of the electrical insulating film 4. Normally, the connection terminal 5 is pressed by the elastic body (spring) 9 as shown in FIG. Since the pressure is pushed downward by the pressure, the lower surface of the connection terminal 5 is in contact with the outer surface (upper surface in the drawing) of the sealing plate 3, and the side surface is in contact with the inner surface of the side wall of the cap 1. 1 and the sealing plate 3 are in an electrically conductive state (switch is turned on) through the connection terminal 5.

  A small hole 6 is provided in the central portion of the sealing plate 3. For example, when the gas pressure inside the storage battery rises during charging, the connection terminal 5 slides upward due to the pressure, and FIG. As shown in (b), the connection terminal 5 and the sealing plate 3 are separated from each other, and the electrical continuity between the cap 1 and the sealing plate 3 is interrupted (the switch is turned off). While the switch is turned off during charging and the temporary charging is interrupted, the gas accumulated inside the storage battery is absorbed by the electrode, and when the pressure inside the storage battery drops, the connection terminal 5 slides downward in the figure. And the circuit is switched on and charging is resumed.

According to this embodiment, since the connection terminal 5 that is the first terminal of the switch slides along the inner surface of the side wall of the cap 1, the connection terminal 5 moves in parallel without being inclined.
Therefore, the contact and release of the connection terminal 5 and the sealing plate 3 as the second terminal of the switch are normally performed, and a highly reliable switch function can be achieved.
Further, the switch mechanism according to the present embodiment is extremely simple in structure as compared with the conventionally proposed switch mechanism shown in FIG. 3 and moves the connection terminal 5 up and down using the space in the cap. There is an advantage that the occupied volume of the switch is small. Further, the operation of the switch mechanism according to the present embodiment is due to the sliding of the connection terminal 5 and not due to the bending of the grommet shown in FIG. There exists an advantage which can maintain the airtightness of a side surface and the side wall inner surface of the cap 1 over a long period of time.

In the above-described embodiment, the example in which the flange portion 2 is a part of the cap 1 has been described. However, the cap 1 and the flange portion 2 may be separate.
In this case, the outer sealing plate 2 corresponding to the flange portion 2 and the cap 1 are joined, the inner wall of the outer sealing plate 2 is vertical, and the straight line formed by the cross section forms the inner surface of the cross section of the side wall of the cap. It is preferable to provide an opening that forms a straight line continuous with the straight line.
As a result, the connection terminal 5 smoothly slides without tilting in response to the pressure change inside the battery, and the side surface of the connection terminal 5 and the inner surface of the opening of the external sealing plate 2 can be brought into airtight contact. it can.

  The wall surface of the cap 1 is preferably provided with a gas discharge through hole 11 for discharging gas in case the pressure inside the battery rises abnormally. FIG. 1 (c) is a diagram showing a state when the gas pressure inside the storage battery has abnormally increased in the embodiment, and the connection terminal 5 slides further upward compared to FIG. 1 (b). FIG. 3 is a view showing a state in which a gas discharge through hole 11 closed by a connection terminal 5 is opened. The gas discharge port (vent) can be provided, for example, on the side wall or bottom wall of the battery case 8, but as shown in FIG. 1 (c), a gas discharge through hole 11 is provided on the side wall of the cap 1. As a result, the gas accumulated in the storage battery is discharged via the space inside the cap, so that the discharge momentum can be weakened and the electrolyte is prevented from blowing out due to the discharged gas momentum. You can also.

  In the present invention, the metal materials constituting the connection terminal 5, the sealing plate 3, and the cap 1 are not particularly limited. However, in the case of an alkaline storage battery, the corrosion resistance to the electrolytic solution is good and the contact resistance is small. In consideration of the above, it is preferable to apply nickel or nickel-plated steel. Further, although the cross-sectional shape, thickness, thickness (cross-sectional area size) of the connection terminal 5 is not particularly limited, in the switch mechanism according to the present invention, the side surface of the connection terminal 5 is connected to the cap 1. It must be brought into airtight and slidable contact with the inner wall surface. Further, when the connection terminal 5 is slid, the connection terminal 5 must be moved in parallel. In order to ensure airtightness and reduce the frictional resistance during sliding, it is preferable that the connection terminal 5 has a circular cross-sectional shape. If the thickness of the connection terminal 5 is small, it is difficult to ensure airtightness, and it is difficult to translate the connection terminal 5. On the contrary, when the thickness of the connection terminal 5 is increased, there are disadvantages that the frictional resistance is increased when the connection terminal 5 is slid and the volume occupied by the switch mechanism is increased. Considering such conditions, when applied to a cylindrical battery, the thickness of the connection terminal is preferably 0.5 to 2 mm, and more preferably 0.5 to 1 mm. In addition, if the cross-sectional area of the connection terminal 5 is small, the force to slide the connection terminal by the internal force inside the storage battery is small, which may reduce the sensitivity of the switch. There arises a drawback that the terminal 5 tends to be inclined. Considering such conditions, when a circular cross-sectional shape which is a preferable cross-sectional shape in the present invention is applied, the diameter of the connection terminal 5 is preferably 1 to 5 mm, and more preferably 1 to 3 mm.

In the present invention, as shown in FIG. 2, it is preferable to arrange an airtight holding layer 12 on the inner surface of the side wall of the cap 1. The airtight holding layer 12 functions to isolate the cap internal space from the external space and prevent foreign matter such as carbon dioxide from entering the cap internal space from the outside by scattering water from the battery. In this embodiment, it is difficult to completely prevent the electrolytic solution from entering the cap. In the case of an alkaline storage battery, when carbon dioxide enters the cap, it reacts with KOH to precipitate a carbonate (solting). When salting occurs in the cap, sliding of the connection terminal is hindered. The arrangement of the airtight holding layer 12 is effective in preventing the occurrence of salting. The hermetic holding layer 12 can be formed by fitting the molded body of the synthetic resin into a cap or attaching a synthetic resin film or metal foil.
Also. In order not to prevent the sliding of the connection terminal 5, it is preferable that the electrolyte does not enter the side surface of the connection terminal 5 and the contact surface of the airtight holding layer 12. For this purpose, the airtight holding layer 12 is preferably made of a water-repellent resin such as polytetrafluoroethylene or polypropylene. Further, as shown in FIG. 5, a coating layer 14 made of the water-repellent synthetic resin is disposed on the side surface of the connection terminal 5 except for a portion necessary for electrical connection with the external terminal (cap) 1. It is preferable to do.

Further, in the present invention, as shown in FIG. 2, when a thin portion 13 is provided in a portion of the airtight holding layer 12 that covers the gas discharge through hole 11, the pressure inside the battery rises abnormally. It is preferable that the thin portion 13 is opened smoothly by breaking.
Should the internal pressure of the battery rise abnormally, the gas accumulated in the battery is discharged through the opening.

(Production of sealed storage battery for testing)
AA-size sealed nickel-metal hydride storage battery comprising a wound electrode plate group in which a nickel electrode is applied to the positive electrode, a hydrogen storage alloy electrode is applied to the negative electrode, and a laminate composed of the positive electrode, the separator and the negative electrode is wound in a spiral shape Thus, ten sealed storage batteries having the structure shown in FIG. 1 and having a pressure switch with an operating pressure of 2 megapascals (MPa) were prepared.
When assembling the storage battery, the electrode plate group having a height of 43 mm was adopted so that the empty space above the electrode plate group was as small as possible. 1ItA (0.21A) was charged for 16 hours, allowed to stand for 1 hour, and then discharged at 0.2 ItA (0.42 A).

(Cycle test using rapid charging)
The formed storage battery is charged in a constant temperature bath at 20 ° C. with a constant current of 4 ItA (8.4 A) (15 minutes, 100% charge), and after 1 hour rest, at 1 ItA (2.1 A) Discharged. This charging / discharging was made into 1 cycle, and charging / discharging was performed repeatedly.

(Comparative Example 1)
Ten conventional sealed nickel-metal hydride storage batteries having no pressure switch function shown in FIG. 4 were prepared. As in the previous embodiment, when assembling the storage battery, the storage battery is assembled so that the free space above the electrode plate group is as small as possible, and a battery with a rated capacity of 2100 mAh can be obtained as in the first embodiment. It was. After chemical conversion, it was subjected to the same cycle test as in the above example.

(Comparative Example 2)
Ten sealed storage batteries having the pressure switch function according to the conventional proposal shown in FIG. 3 were prepared.
As in the previous example, when assembling the storage battery, the electrode plate group having a height of 41 mm was applied, and the storage battery was assembled so that the empty space above the electrode plate group was as small as possible.
The rated capacity of the obtained storage battery was 2000 mAh. In the case of Comparative Example 2, the volume occupied by the pressure switch was larger than that in the previous example, and the height of the electrode plate group had to be set small. After chemical conversion, it was subjected to the same cycle test as in the above example.

(Test results)
Table 1 shows the initial capacities of Examples, Comparative Examples 1 and 2 (discharge capacity at the first cycle of the cycle test, average value of 10).

In Comparative Example 1, it is considered that the discharge temperature was remarkably reduced because the battery temperature increased during charging, and multiple reactions such as decomposition of moisture became active and the charge acceptance was extremely reduced.
Further, in Comparative Example 2, the volume occupied by the pressure switch is large as described above, and the height of the electrode plate group has to be reduced as compared with the Example, which is influenced by the fact that the rated capacity is reduced. It is considered that the capacity is reduced even in the quick charge.

FIG. 6 shows the relationship between the number of cycles and the discharge capacity in Example and Comparative Example 1. The time when the discharge capacity fell below 38% of the initial capacity was determined as the cycle life.
The cycle life of Comparative Example 1 was 95 cycles (average of 10), whereas in the Examples, it was 509 cycles. In the comparative battery, it is considered that when the gas discharge valve is opened, the electrolyte is scattered outside the system and the internal resistance of the battery is increased, so that the capacity is quickly reduced and the cycle performance is inferior.
Although omitted in FIG. 6, the cycle life of Comparative Example 2 was 468 cycles, which was slightly inferior to the Example.

  In Comparative Example 2, since the first terminal of the switch does not move in parallel as described above and is inclined with respect to the second terminal, the on / off switching may not function normally. This is probably because the charge acceptance rate is lower than in the example, or the battery temperature rises and the deterioration of battery performance is accelerated.

  The sealed storage battery according to any one of claims 1 to 4, wherein the charging current can be cut off and connected with a simple and compact structure due to a change in the pressure in the battery at the time of charging, and the switch mechanism has high operation reliability. It is a storage battery that can suppress an increase in internal pressure during rapid charging, can suppress the electrolyte from splashing outside the system, and can realize a sealed storage battery with excellent cycle characteristics, so the industrial applicability is extremely large .

It is principal part sectional drawing which shows the structure of the switch of the sealed storage battery which concerns on this invention. It is principal part sectional drawing which shows the structure of the switch of the sealed storage battery which concerns on this invention. It is principal part sectional drawing which shows the structure of the switch of the sealed storage battery which concerns on a prior proposal. It is principal part sectional drawing which shows the structure of the sealing part of the conventional sealed storage battery. It is sectional drawing which shows the structure of the connection terminal of the sealed storage battery which concerns on this invention. It is a graph which shows the relationship between the cycle number of an example battery and a comparative example battery, and discharge capacity.

Explanation of symbols

1 External terminal 2 Flange (external sealing plate)
3 Sealing plate 4 Electrical insulating film 5 Connection terminal 6 Small hole 9 Elastic body (spring)
11 Through-hole 12 Airtight holding layer 13 Thin portion

Claims (4)

In a sealed storage battery with a built-in switch mechanism that switches on and off a charging circuit that connects an electrode plate and an external terminal due to a pressure change inside the storage battery during charging,
The switch mechanism is composed of a metal sealing plate and a connection terminal,
The sealing plate and the external terminal are insulated by an electrical insulating layer, and the switch mechanism is normally in an on state by the contact of the connection terminal to both the sealing plate and the external terminal,
A sealed storage battery characterized in that when the internal pressure of the storage battery rises, the connection terminal is separated from the sealing plate and the electrical connection between the sealing plate and the external terminal is cut off, so that the switch mechanism is switched from on to off. The side wall inner surface of the external terminal is perpendicular to the sealing plate, the connection terminal is columnar, the side surface abuts against the side wall inner surface of the external terminal, and the connection terminal is against the side wall of the external terminal. The sealed storage battery according to claim 1, wherein the battery is slidable. The sealed storage battery according to claim 2, wherein a gas discharge through hole is provided in a wall surface of the external terminal. An airtight holding layer for keeping the space inside the external terminal airtight is disposed on the inner surface of the external terminal and the connection terminal, and the gas is discharged to the outside through the through holes by generating a breakage in the airtight holding layer. The sealed storage battery according to claim 3, wherein the sealed storage battery is made possible.

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