JP2008251591A - Capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor that is used for vehicles or the like and is provided with an inexpensive valve to surely discharge and detect gas. <P>SOLUTION: An element 1 is housed together with an organic electrolyte 3 in a case 2, and the opening of the case 2 is sealed by a sealing substance 4. In such a capacitor, a gas transmitting member 5 for transmitting a gas produced in the capacitor and a reversible valve 6 for discharging the gas transmitting the gas transmitting member 5 to the outside are provided, and a sensor 7 is provided between the gas transmitting member 5 and the reversible valve 6. Thus, the capacitor having a simplified structure that is equipped with a valve capable of reliable operation can be provided at low cost. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a capacitor used for various electronic devices, a backup power source for a hybrid vehicle or a fuel cell vehicle, a regenerative power source, or a power storage device.

  A capacitor using an organic electrolytic solution has a withstand voltage of 2.0 V or more because a decomposition voltage of the organic electrolytic solution is higher than that of a capacitor using an aqueous electrolytic solution. In addition, a capacitor using an organic electrolytic solution containing a lithium salt as an electrolyte and having lithium ions reversibly inserted and removed from the negative electrode has a withstand voltage of 3.0 V or more. Capacitors using these organic electrolytes have the advantage of high energy density because they have a withstand voltage higher than the electrolysis voltage of water.

  However, even in a capacitor using an organic electrolyte, a weak decomposition current flows due to the presence of activated carbon used as a polarizable electrode, an electrolyte, or a trace amount of water that invades, and it decomposes during a long-term use period. Gas is generated. For this reason, in order to prevent explosion from internal pressure rise due to these generated gases, a commercially available capacitor has a structure that can release the generated gas to the outside when the pressure exceeds a certain level. A typical method is to install a gas permeable member that does not transmit liquid but allows gas to pass between a metal case housing a capacitor element together with an organic electrolyte and the outside. Silicon gas, polytetrafluoroethylene, or the like is used as the gas permeable member.

  In recent years, with the increase in energy density, the amount of activated carbon and electrolyte contained in the capacitor cell has increased, and as a result, the amount of gas generated has increased, and the gas required to be released from the gas permeable member to the outside. The amount is increasing. However, gas permeable members generally have a problem that when the gas permeability is increased, gas penetration from the outside, specifically, water vapor permeability is increased, and the withstand voltage is lowered in a capacitor using an organic electrolyte. To do.

  In order to solve this, a structure in which a gas is released between a metal case and the outside using a reversible valve instead of a gas permeation valve has begun to be adopted. The reversible valve has a function that opens the valve when the pressure inside the case exceeds a certain pressure (working pressure), and allows the gas to escape to the outside. And has a function of maintaining the sealing performance. However, in applications where a high voltage is required, such as automobile applications, it is necessary to connect a plurality of capacitor cells in series. However, a reversible valve having a complicated structure is generally more expensive than a gas permeable member. In addition, providing reversible valves in all cells is problematic in terms of cost.

  On the other hand, in the environment where the capacitor is used, specifically, in a high-temperature and high-humidity atmosphere, it is conceivable that the trace amount of moisture that has already been introduced increases. Although the increase in the amount of moisture permeated after itself does not cause a serious problem for the capacitor, in some cases, a problem arises that the decomposition current is increased and the deterioration rate is increased. For these problems, by detecting the capacity decrease and resistance increase caused by the above degradation, feedback to the charge / discharge system, specifically by reducing the applied voltage to suppress the decomposition current, etc., A method of slowing down the deterioration speed to a required speed can be taken. Further, depending on the deterioration state, it is possible to prompt the system to exchange the capacitor itself by issuing a signal.

  However, rather than detecting the capacitance decrease and resistance increase as these capacitor characteristics, if it is possible to detect the moisture mixing that causes them and the increase in the amount of gas generated thereby, feedback to the charge / discharge system is applied earlier. Although it is possible to construct a more reliable system, no technology that can be realized at low cost has been found so far.

  FIG. 4 is a longitudinal sectional view showing a configuration of a sealed power storage device using a non-aqueous power storage element as an example of a conventional capacitor. In FIG. 4, 10 is an exterior body, and 11 is a plurality in the exterior body 10. The electric double layer capacitor in which the individual is housed, 12 is a current extraction terminal joined to the electric double layer capacitor 11, and the electric double layer capacitor 11 is housed in a bag-like case 13 formed of a polypropylene film, The opening of the case 13 is not sealed.

  The exterior body 10 includes a box body 14 having an opening in the upper portion and a lid body 15 placed so as to cover the opening of the box body 14, and a gap between the box body 14 and the lid body 15. In addition, the gap between the current extraction terminal 12 joined to the electric double layer capacitor 11 and the current extraction terminal opening 16 provided in the lid 15 includes a polyolefin-based compound and has a moisture barrier property. It is sealed with a sealing material 17 that is liquid thermosetting.

  The conventional sealed power storage device configured as described above can be manufactured with high productivity and has excellent moisture barrier properties, so that the electrical characteristics can be stably maintained over a long period of time. (Patent Document 1).

  On the other hand, in the secondary battery, various techniques for releasing the generated gas to the outside have been proposed, and FIG. 5 is a schematic diagram showing the configuration of the battery module of the assembled battery as an example. , 26 is a rectangular battery case serving as an outer frame containing six battery cells (20, 21, 22, 23, 24, 25). The square battery case 26 and the six battery cells A communication passage 27 is formed between them.

  In addition, an exhaust terminal 28 is formed in the square battery case 26, and a collective safety valve 29 is provided in the exhaust terminal 28. Between the battery cells (20, 21, 22, 23, 24, 25) and the communication passage 27, inter-cell safety valves (30, 31, 32, 33, 34, 35) are provided. The operating pressure in the inter-cell safety valve is set lower than the operating pressure of the collective safety valve 29.

  The conventional assembled battery configured in this manner prevents damage to each battery cell using the inter-cell safety valve without affecting the influence of the abnormal cell in which hydrogen gas is generated on other normal cells, and the collective safety valve 29 Can be used to prevent the rectangular battery case 26 of the battery module from being damaged.

  Further, since the inter-cell safety valve is smaller and cheaper than the collective safety valve 29 and is attached to the communication passage 27 in units of battery cells, the size of the assembled battery is not increased and the production cost is not increased. Thus, it is possible to provide a low-cost assembled battery that can extend the life of the battery (Patent Document 2).

  FIG. 6 is a cross-sectional view showing a configuration of a main part of a detection mechanism of an overdischarge detection device for a sealed alkaline secondary battery as an example of this type of conventional art. In FIG. 6, 40 is a cell, 41 is a cell. The battery case 42 is a gas release valve for releasing hydrogen gas and oxygen gas generated in the cell battery case 41 to the outside, and a plurality of the cells 40 having such a structure are connected and modularized. Is.

  The gas release valve 42 includes a chamber 43 formed in an upper portion of the cell 40, a spring 44 and a valve body 45 provided in the chamber 43, and the space in the chamber 43 and the cell electric power via the valve body 45. A passage 46 that communicates with the tank 41 and a passage 47 that communicates the space in the chamber 43 to the outside. In the passage 47, a thin film 48 that is broken by a gas of a predetermined pressure generated in the cell battery 41 is formed. It is arranged.

  On the other hand, the chamber 43 provided in the cell 40 communicates with the chambers of the other plurality of cells modularized by the communication cover 49a, and the communication covers 49a to 49h are connected to the joints 50a to 50h. A thin film 52 that is broken by a gas having a predetermined pressure generated in the cell battery case 41 is disposed in the joint portions 50a to 50h. A chamber 53 is connected to the other end of the conduit 51. The chamber 53 is provided with a hydrogen gas sensor 54 for detecting hydrogen gas in the introduced gas, and releases the hydrogen gas to the outside. An opening 55 is formed for this purpose.

  The conventional overdischarge detection device for a sealed alkaline secondary battery configured as described above can detect the overdischarge state of the sealed alkaline secondary battery at an early stage. In addition, when the sealed alkaline secondary battery has a plurality of cells, it is possible to identify a cell in an overdischarged state, and to reliably detect the overdischarged state. It was possible (Patent Document 3).

As prior art document information related to the invention of this application, for example, Patent Documents 1 to 3 are known.
JP 2005-142416 A JP 2004-39582 A JP-A-9-45376

  However, the conventional capacitor shown in Patent Document 1 has a configuration in which the entire exterior body 10 is sealed with the moisture-blocking sealing material 17 without sealing the single electric double layer capacitor 11 alone. Although there is a merit that the cost can be reduced because the capacitor 11 is not provided with a valve, the internal pressure rises because there is no means for releasing the gas generated inside the outer casing 10 by being generated inside the electric double layer capacitor 11 to the outside. Cannot solve problems that sometimes occur.

  Further, when the electric double layer capacitor 11 alone is not sealed, gas generation inside the electric double layer capacitor 11, deterioration of the current collector due to the rising of the electrolytic solution, and the like, and further, the degree of progress of each of the electric double layer capacitors 11 are There is a problem in that the entire characteristics are affected by the most deteriorated electric double layer capacitor 11 because it varies between the multilayer capacitors 11.

  Moreover, in the conventional secondary battery shown in Patent Document 2, although safety is improved by providing the inter-cell safety valve 30 and the collective safety valve 29 in the battery cell 20 and the battery module, respectively, the battery cell 20 Since all the cells must have the inter-cell safety valve 30, there is a problem that the cost increases.

Further, in the conventional secondary battery shown in Patent Document 3, it is possible to detect the generation of hydrogen gas by opening the gas release valve 42, but this is a considerable amount of hydrogen released at once. It is applicable only when sensing is easy, and is not applicable when the main generated gas is an inert gas such as CO ₂ and the generated amount is small like an electric double layer capacitor. When the gas release valve 42 is an irreversible valve, moisture from the outside air enters after the valve is opened, and therefore there is a problem that it cannot be applied to those using an organic electrolyte.

  SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and to provide an inexpensive capacitor having a self-recovering type valve capable of reliably releasing and detecting gas generated in the capacitor. It is.

  In order to solve the above problems, the present invention provides a gas permeation that allows gas generated inside a capacitor to pass through in a capacitor in which the element is housed in a case together with an organic electrolyte and the opening of the case is sealed with a sealing member. Means (1) and gas permeation means (2) for releasing the gas permeated through the gas permeation means (1) to the outside, and gas generation between the gas permeation means (1) and the gas permeation means (2) In this configuration, a quantity detection means is provided.

  As described above, the capacitor according to the present invention includes a self-returning type valve constituted by the gas permeation means (1) and the gas permeation means (2). The effect that the provided capacitor can be provided at low cost is obtained.

(Embodiment 1)
Hereinafter, with reference to the first embodiment, the invention described in the first, third, fifth, and seventh to ninth aspects of the present invention will be described.

  FIG. 1 is a schematic diagram showing the configuration of a capacitor according to Embodiment 1 of the present invention. In FIG. 1, 1 is an element, and this element 1 is mainly composed of activated carbon on a current collector made of metal foil. A pair of positive and negative electrodes on which a polarizable electrode layer is formed is formed by laminating or winding each electrode with a polarizable electrode layer facing each other with a separator interposed therebetween.

  2 is a case in which the element 1 is housed together with the organic electrolyte 3, 2 a is an internal space that is not filled with the organic electrolyte 3 in the case 2, and 2 b is an upper space of the case 2. The space between 4 and the reversible valve 6 is shown.

  4 is a sealing body that seals the opening of the case 2, and 5 is a gas permeable member as a gas permeable means (1) provided in the sealing body 4, and the gas permeable member 5 is permeable to liquid. Although it does not, it can permeate gas.

  6 is a reversible valve as gas permeation means (2) provided on the upper surface of the upper space 2b of the case 2, and 7 is a sensor as gas generation amount detection means provided in the upper space 2b of the case 2, As this sensor 7, a pressure sensor or a gas sensor can be used.

  The operation of the capacitor according to the present embodiment configured as described above will be described. Decomposed gas generated by the presence of a small amount of water is released through the gas permeable member 5 as the gas permeable means (1). Moreover, the pressure in the internal space 2a and the upper space 2b is always kept the same.

  Next, when the pressure in the upper space 2b in the case 2 rises due to the gas released through the gas permeable member 5, the reversible valve 6 as the gas permeable means (2) is opened and the gas is discharged to the outside. Since the pressure in the upper space 2b is reduced due to the release, the reversible valve 6 is closed to return to the original state, and thereafter the same operation is repeated.

  FIG. 2 shows the result of measuring the amount of gas generation and the pressure fluctuation in the upper space 2b with the sensor 7. By providing the sensor 7, the pressure at which the reversible valve 6 operates, the number of operations, etc. As a result, the output of the sensor 7 can be fed back to a charge / discharge circuit of a capacitor (not shown) to perform charge / discharge control, thereby extending the service life. Is.

  More specifically, when the time change of the amount of generated gas increases, it is determined that the decomposition current has increased, and the maximum voltage applied to the capacitor is reduced. Preferably, by continuously monitoring the amount of gas generated after lowering the maximum voltage, it is fed back to the desired maximum voltage (for example, if the gas generation amount drops significantly, the maximum voltage is increased again; if the gas generation amount is still high) The maximum voltage is further reduced, or an external signal is output as a deterioration rate abnormality). Further, since the sensor 7 does not touch the electrolytic solution 3, the reliability of the output is high.

  As described above, the capacitor according to the present embodiment is configured as a self-recovering type valve by the gas permeable member 5 and the reversible valve 6, so that it can be reliably operated with a simple configuration, and further, degassing and suppression of moisture mixing It is possible to provide a capacitor having a highly reliable valve capable of satisfying both of these requirements at a low cost.

  In the present embodiment, the gas permeable member 5 is used as the gas permeable means (1) and the reversible valve 6 is used as the gas permeable means (2). However, the present invention is limited to this. Instead of this, a reversible valve may be used as the gas permeable means (1).

  The element 1 in the present invention includes a positive electrode in which a polarizable electrode layer mainly composed of activated carbon is formed on a current collector made of metal foil, and an electrode mainly composed of a carbon material on the current collector made of metal foil. It is also possible to use a layer formed by laminating or winding a negative electrode on which a layer is formed, with a separator interposed therebetween, with each electrode layer facing each other. Even if it is, the same effect can be obtained.

(Embodiment 2)
The second and sixth aspects of the present invention will be described below with reference to the second embodiment.

  In this embodiment, the capacitor described with reference to FIG. 1 in the first embodiment is modularized, and the other configuration is the same as that of the first embodiment. Detailed description thereof will be omitted, and only different parts will be described below with reference to the drawings.

  FIG. 3 is a schematic diagram showing the configuration of the capacitor according to the second embodiment of the present invention. In FIG. 3, 8 is a cell in which the element 1 is housed in a case (not shown) together with the organic electrolyte 3. Each of the cells 8 is provided with a gas permeable member 5 as a gas permeable means (1), and a plurality (two in the present embodiment) of the cells 8 configured in this manner are provided in the outer case 9. And each cell 8 is electrically connected.

  6 is a reversible valve as gas permeation means (2) provided above the upper space 9b of the outer case 9, and 7 is a sensor as gas permeation means (2) provided in the upper space 9b of the outer case 9. is there.

  The operation of the capacitor according to this embodiment configured as described above will be described. The decomposed gas generated in the plurality of cells 8 due to the presence of a small amount of water is the gas permeable member 5 as the gas permeable means (1). Therefore, the pressures in the internal space 9a and the upper space 9b that are not filled with the organic electrolyte 3 in the case are always kept the same.

  Next, when the pressure in the upper space 9b in the exterior case 9 rises due to the gas released through the gas permeable member 5, the reversible valve 6 as the gas permeable means (2) is opened, and the gas is externally supplied. Accordingly, the pressure in the upper space 9b is reduced, and the reversible valve 6 is closed to return to the original state, and thereafter the same operation is repeated.

  The capacitor according to the present embodiment configured as described above is provided only with the gas permeable member 5 as the gas permeable means (1) for each cell 8 when the plurality of cells 8 are connected to form a module. Since only one reversible valve 6 as the gas permeation means (2) needs to be provided in the outer case 9, in addition to the effect obtained by the capacitor according to the first embodiment, it can be configured at a lower cost. This is a special effect.

  It should be noted that the gas diffusion coefficient of the gas permeable member 5 as the gas permeable means (1) is set to be the same in the gas permeable member 5 provided in each cell 8, so that the moisture content of all the cells 8 is increased. It is averaged, and the variation variation between the cells 8 can be equalized. As a result, when each cell 8 is connected in series, the most deteriorated cell 8 is not pulled, and as a result, a long life as a module can be achieved. .

  The capacitor according to the present invention has an effect that a capacitor having a highly reliable valve capable of reliable operation with a simple configuration can be provided at low cost, particularly in a hybrid vehicle or a fuel cell vehicle. It is useful as a backup power source or for regeneration.

The schematic diagram which showed the structure of the capacitor by Embodiment 1 of this invention Characteristic chart showing fluctuation of gas generation amount and pressure of the capacitor The schematic diagram which showed the structure of the capacitor by Embodiment 2 of this invention The longitudinal cross-sectional view which showed the structure of the sealed electrical storage apparatus using the non-aqueous electrical storage element as an example of the conventional capacitor The schematic diagram which showed the structure of the battery module of the assembled battery as an example of the conventional capacitor Sectional drawing which showed the principal part structure of the detection mechanism of the overdischarge detection apparatus of the sealed alkaline secondary battery as an example of the conventional capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Element 2 Case 2a, 9a Internal space 2b, 9b Upper space 3 Organic electrolyte 4 Sealing body 5 Gas-permeable member 6 Reversible valve 7 Sensor 8 Cell 9 Exterior case

Claims (11)

In a capacitor in which the element is housed in a case together with an organic electrolytic solution and the opening of the case is sealed with a sealing member, a gas permeable means (1) that transmits gas generated inside the capacitor, and the gas permeable means ( A capacitor provided with a gas permeable means (2) for releasing the gas that has passed through 1) to the outside, and a gas generation amount detecting means between the gas permeable means (1) and the gas permeable means (2). The element is housed in a case together with an organic electrolyte, and has a plurality of cells in which the opening of the case is sealed with a sealing member, and the plurality of cells are electrically connected and housed in an exterior case. In the capacitor, gas permeation means (1) for permeating gas generated inside the cell is provided for each cell, and gas permeation means (2) for releasing the gas permeated through the gas permeation means (1) to the outside is provided. Capacitor provided in the outer case. The capacitor according to claim 2, wherein a gas generation amount detection means is provided between the gas permeation means (1) and the gas permeation means (2). The capacitor according to claim 1 or 2, wherein a gas permeable member is used as the gas permeable means (1). The capacitor according to claim 1 or 2, wherein a reversible valve is used as the gas permeation means (2). The capacitor according to claim 1, wherein a pressure sensor or a gas sensor is used as the gas generation amount detection means. The capacitor according to claim 4, wherein gas diffusion coefficients of the gas permeable members respectively provided in the plurality of cells are the same. The capacitor according to claim 1, wherein charge / discharge control of the capacitor or cell is performed based on an output of the gas generation amount detection means. As a device, a pair of positive and negative electrodes in which a polarizable electrode layer mainly composed of activated carbon is formed on a current collector made of a metal foil is laminated with each polarizable electrode layer facing each other with a separator interposed therebetween, The capacitor according to claim 1, wherein an element configured by winding is used. As a device, a positive electrode in which a polarizable electrode layer mainly composed of activated carbon is formed on a current collector made of metal foil, and a negative electrode in which an electrode layer mainly composed of a carbon material is formed on a current collector made of metal foil. The capacitor according to claim 1, wherein an element is formed by laminating or winding with each electrode layer facing each other with a separator interposed therebetween. The capacitor according to claim 1 or 2, wherein an organic electrolytic solution containing at least a lithium salt as an electrolyte is used.

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