JP2005149837A - Battery structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery structure capable of maintaining conditions for insulation in a fuel cell stack and in a battery where a number of battery cells containing an aqueous solution are connected in series to obtain a high voltage and are semi-enclosed. <P>SOLUTION: A battery section 100 is formed by housing a battery pack of a plurality of battery modules 130 connected in series in a space formed by a battery cover 102 and a lower case 122. Humidity conditioning sheets 200, which absorbs moisture when ambient humidity is high and releases moisture when the ambient humidity is low, are placed inside the battery cover 102. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery structure such as a fuel cell stack or a secondary battery mounted on a vehicle, and in particular, in a fuel cell or in order to obtain a high voltage, a large number of battery modules are connected in series to be in a semi-sealed state. The present invention relates to a battery structure that maintains an insulating state in a secondary battery.

  A power supply unit (battery pack) having a relatively large-capacity secondary battery is mounted on a vehicle in which a vehicle is driven by a motor such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle. Such a battery pack obtains a high voltage by connecting a large number of lead storage batteries, nickel metal hydride batteries, lithium ion batteries, and the like in series.

  In general, a battery pack is integrally formed by connecting a plurality of (for example, six) single cells (for example, battery cells having an output voltage of 1.2 V) so that a necessary power capacity (voltage value) is obtained. A collective secondary battery (battery module) that is configured to be connected to each other is often used. A predetermined number of such battery modules are further connected in series to form a battery pack having a high voltage output of 200V to 300V.

  In this battery pack, the wide side surfaces of the rectangular parallelepiped battery modules are arranged so as to be opposed to each other, and the end plates are in contact with the outside of the battery case of the battery modules at both ends, and between the end plates. Are integrally connected by binding them with a restraining band.

  A battery cell (for example, a nickel metal hydride battery) accommodates an electrode plate group, which is a power generation element formed by laminating a positive electrode plate and a negative electrode plate via a separator, together with an electrolyte solution, Closed with a lid provided with a safety valve, lead out upward from one side upper end of each positive electrode plate constituting the electrode plate group, connect a positive terminal to the upper part, and similarly, upper end of the other side of each negative electrode plate The lead is drawn upward from the lead, the negative terminal is connected to the upper part, and the positive terminal and the negative terminal are attached to a lid.

  Further, a lithium ion battery having a nonaqueous electrolyte has a similar configuration when a high voltage is required. As the material of the battery container used for such a battery cell, for example, thermoplastic resin such as ABS resin, polyolefin resin such as polypropylene (PP), polyethylene (PE), etc. are used because of light weight and low cost. ing. Ordinary resins have the property of allowing moisture to permeate, and when a resin battery container is used for a lithium ion battery having a non-aqueous electrolyte, there is a problem that moisture permeated into the battery container reduces battery performance. It was. Specifically, when water is present inside the battery container of the nonaqueous electrolyte battery, the water and the nonaqueous electrolyte react to generate hydrofluoric acid, and the generated hydrofluoric acid corrodes the electrode, and the battery capacity and battery There was a problem of reducing the performance such as life.

  Japanese Patent Laid-Open No. 2002-100407 (Patent Document 1) discloses a nonaqueous electrolyte battery having a resin battery container in which a significant increase in battery weight is suppressed and a decrease in battery performance due to moisture permeation is suppressed. Disclose. This battery is a non-aqueous electrolyte secondary battery, and an electrode body having a positive electrode, a negative electrode, and a non-aqueous electrolyte, and a battery cell chamber that is formed of a resin and in which the electrode body is hermetically sealed are partitioned inside. A battery container and an adsorbent that adsorbs moisture in the battery cell chamber are provided.

This non-aqueous electrolyte secondary battery is, for example, a lithium ion battery, and according to this battery, the moisture that has permeated through a lightweight resin battery container is placed on the adsorbent by arranging an adsorbent that adsorbs moisture inside the battery. It is suppressed that the electrolyte and moisture react with each other.
Japanese Patent Laid-Open No. 2002-100407

  However, the technique disclosed in Patent Document 1 generates hydrofluoric acid by causing a reaction between moisture and a nonaqueous electrolyte, which is a problem in a secondary battery in which the electrolyte is a nonaqueous electrolyte such as a lithium ion battery. However, the hydrofluoric acid corrodes the electrode, and is merely for solving the problems such as battery capacity and battery life. Therefore, an adsorbent that only exhibits an action of adsorbing moisture is used.

  In addition to such lithium ion batteries, in particular, secondary batteries in which the electrolytic solution is an aqueous solution, such as nickel metal hydride batteries, and fuel cells having an aqueous solution in the stack, need to retain the insulating portion inside the battery. Indispensable. In particular, in the case of a secondary battery using a negative electrode active material or a nickel-based positive electrode active material, the electrolytic solution is generally an alkaline aqueous solution such as KOH and draws moisture in the air and develops conductivity. At this time, if the humidity inside the battery pack is low, such conductivity will not be exhibited, but if the humidity inside the battery pack is high, conductivity will be exhibited, and the terminals, busbars and battery pack case are electrically connected. If connected, the insulation resistance is lowered and an earth leakage path may be formed. Such a problem can become more prominent in the dew condensation state.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to provide a semi-sealed state in which a large number of battery cells including an aqueous solution are connected in series in order to obtain a high voltage. It is an object of the present invention to provide a battery structure capable of maintaining an insulating state in the battery.

  The battery structure according to the first invention is a structure of a battery mounted on a vehicle. This battery has a battery cell containing an aqueous solution. This battery structure includes storage means for storing battery cells in a closed space, and holding means for avoiding dielectric breakdown caused by the aqueous solution and maintaining a necessary insulating state. The holding means includes humidity adjusting means for expressing a moisture absorbing function and a moisture releasing function according to the ambient humidity.

  According to the first invention, for example, when the battery is composed of a large number of nickel hydride battery cells and the terminals of the battery cells are connected in series by a bus bar, the holding means includes the plurality of battery cells. When the humidity inside the storage means storing the battery cells is high, moisture is absorbed, and when the humidity is low, moisture is released. The battery cell contains an aqueous solution containing KOH, which is an electrolytic solution, in a semi-sealed state (not completely sealed because it may communicate with the outside by a pressure valve or the like, or may leak). When humidity inside the storage means is high, KOH takes in moisture in the air, and there is a possibility that the bus bar or terminal and the storage means are connected by moisture, but moisture inside the storage means is absorbed by the humidity control means. , The possibility of conduction can be eliminated, and the necessary insulation state can be maintained. On the other hand, when the humidity inside the storage means is low, the humidity control means releases moisture into the storage means. At this time, since there is little moisture in the air, even if moisture is released, there is little possibility of conduction between the bus bar or terminal and the storage means due to moisture. For this reason, moisture absorption and moisture release by the humidity control means can be repeated semi-permanently (longer than the battery life). In addition, this can be applied to secondary batteries other than nickel metal hydride batteries and fuel cell stacks. As a result, it is possible to provide a battery structure capable of maintaining an insulating state in a fuel cell stack or in a battery in which a large number of battery cells containing an aqueous solution are connected in series to obtain a high voltage and are semi-sealed. Can do.

  The battery structure according to the second invention is a structure of a secondary battery mounted on a vehicle. This secondary battery has a configuration in which a plurality of battery cells whose electrolytic solution is an aqueous solution are connected in series. This battery structure includes storage means for storing battery cells in a closed space, and holding means for avoiding dielectric breakdown caused by the electrolyte and maintaining a necessary insulating state. The holding means includes humidity adjusting means for expressing a moisture absorbing function and a moisture releasing function according to the ambient humidity.

  According to the second invention, the secondary battery is composed of a large number of nickel-metal hydride battery cells, and the terminals of these battery cells are connected in series by the bus bar, and the holding means includes the plurality of battery cells. When the humidity inside the storage means storing the battery cells is high, moisture is absorbed, and when the humidity is low, moisture is released. The battery cell contains an aqueous solution containing KOH, which is an electrolytic solution of a nickel metal hydride battery, in a semi-sealed state. When the humidity inside the storage means is high, KOH takes in moisture in the air, and there is a possibility that the bus bar or terminal and the storage means are connected by moisture, but moisture inside the storage means is absorbed by the humidity control means. , The possibility of conduction can be eliminated, and the necessary insulation state can be maintained. On the other hand, when the humidity inside the storage means is low, the humidity control means releases moisture into the storage means. At this time, since there is little moisture in the air, even if moisture is released, there is little possibility of conduction between the bus bar or terminal and the storage means due to moisture. For this reason, moisture absorption and moisture release by the humidity control means can be repeated semi-permanently (longer than the battery life). As a result, it is possible to provide a battery structure capable of maintaining an insulating state in a secondary battery in which a large number of battery cells containing a water-soluble electrolyte are connected in series to obtain a high voltage and are semi-sealed. Can do.

  In the battery structure according to the third invention, in addition to the configuration of the first or second invention, the humidity control means expresses a moisture absorption function that absorbs humidity when the surroundings are at high humidity, and the surroundings are at low humidity. If it is, it is a humidity adjustment member which expresses the moisture release function which discharge | releases humidity.

  According to the third invention, for example, by using a humidity adjusting member having both a moisture absorbing function and a moisture releasing function by a functional substance such as a highly water-absorbing polymer or zeolite as a humidity control means, A battery structure capable of maintaining an insulating state can be provided.

  In the battery structure according to the fourth invention, in addition to the configuration of the third invention, the humidity adjusting member is a humidity control sheet.

  According to the fourth invention, by providing a sheet-like humidity adjusting member containing a functional substance such as a superabsorbent polymer or zeolite in the vicinity of the battery cell terminal and the bus bar, the insulation state in the battery is semi-permanently. A battery structure that can be held can be provided.

  In the battery structure according to the fifth invention, in addition to the configuration of any one of the second to fourth inventions, the electrolyte of the secondary battery is a water-soluble battery.

  According to the fifth invention, in a nickel metal hydride battery containing a water-soluble electrolyte, for example, a sheet-like humidity adjusting member containing a functional material such as a superabsorbent polymer or zeolite is provided near the battery cell terminal and bus bar. By providing, the battery structure which can maintain the insulation state in a battery semipermanently can be provided.

  In the battery structure according to the sixth invention, in addition to the structure of any one of the second to fifth inventions, the secondary battery is a nickel metal hydride battery.

  According to the sixth invention, in a nickel metal hydride battery containing a water-soluble electrolyte, a sheet-like humidity adjusting member containing a functional material such as a superabsorbent polymer or zeolite is provided in the vicinity of the battery cell terminal and bus bar. Thus, it is possible to provide a battery structure that can maintain the insulation state in the battery semi-permanently.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  In the following description, the battery mounted on the vehicle may be not only a secondary battery but also various batteries including a fuel cell. In the following, the battery constituting the battery pack will be described as a nickel metal hydride battery. Also. The minimum unit of the battery will be described as a battery cell, a battery module in which a plurality of battery cells are connected in series, and a battery pack in which a plurality of battery modules are connected in series. In addition, these battery cells, battery modules, and battery packs are designations, and may be different designations.

  A battery structure according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a developed schematic view of the battery unit 100, and FIG. 2 is a schematic perspective view of a battery module constituting the battery pack of FIG.

  As shown in FIG. 1, the battery unit 100 has a structure in which a battery pack 120 is accommodated in an exterior member including a battery cover 102 and a lower case 122. The battery pack 120 is formed by stacking a plurality of battery modules 130. As the battery module 130, a secondary battery such as a nickel metal hydride battery can be used. The battery module 130 has a so-called square plate-like outer shape.

  The battery module 130 includes a plurality of battery cells. Specifically, as shown in FIG. 2, the battery module 130 includes an integral square battery case 138 that is a module exterior member, and six battery cells 140 to 140 that are partitioned by a partition wall inside the square battery case 138. 150. A terminal 128 is formed on the end surface of the rectangular battery case 138 in the long axis direction. On the side surface of the square battery case 138, a protrusion 152 for forming a gap as a cooling air flow path between the battery modules 130 is formed. In the battery pack 120 (see FIG. 1) in which the battery modules 130 are stacked, the protrusions 152 of the battery modules 130 come into contact with each other, and a gap is formed between the battery modules 130. In FIG. 2, the exhaust terminal 126 (see FIG. 1) is not shown, and a state in which a part of the square battery case 138 is removed is shown for explaining the battery cells 140 to 150.

  Each of the battery cells 140 to 150 basically has the same structure. The first battery cell 140 will be described as an example. The battery cell 140 sandwiches the stacked electrode body 154 and a stacked electrode body 154 configured by stacking a plurality of sheet-like electrode members in an insulated state with a separator, for example. And a pair of current collector plates 156 arranged as described above. The laminated electrode body 154 is impregnated or injected with an electrolytic solution.

  In the laminated electrode body 154, the electrode member serving as the positive electrode and the electrode member serving as the negative electrode are alternately overlapped. Moreover, the edge part of the electrode member used as a positive electrode is connected to one current collecting plate 156 collectively. And the edge part of the electrode member used as a negative electrode is connected to the other collector plate (not shown) collectively. As a result, all electrode members serving as positive electrodes and one current collecting plate 156 are electrically connected. Moreover, all the electrode members used as a negative electrode and the other collector plate will be in the electrically connected state. The battery cells 140 to 150 included in the battery module 130 are electrically connected in series. For example, when the rated voltage of each of the battery cells 140 to 150 is 1.2V, the rated voltage of the entire battery module 130 is 7.2V. The configuration of the battery cells 140 to 150 is not limited to the configuration described above, and may be another configuration.

  As shown in FIG. 1, constraining plates 116 and 118 are disposed at both ends of the battery pack 120. The restraint plates 116 and 118 are connected and fixed to each other by restraint pipes 108 and 110. The restraining plates 116 and 118 are fixed to the lower case 122. Each battery module 130 is also fixed to the lower case 122.

  On each side surface (end surface) of the battery module 130 constituting the battery pack 120, the terminal 128 for inputting / outputting current to / from the battery module 130 is formed as described above. In order to connect the terminals 128 of the battery module 130 to each other, bus bar modules 112 and 114 are disposed on the side surface of the battery pack 120. By connecting the bus bar modules 112 and 114 to the respective terminals 128 of the battery module 130, the battery modules 130 are electrically connected in series in the battery pack 120.

  On the upper surface of the battery pack 120, an exhaust terminal 126 having a built-in safety valve for exhausting hydrogen gas exhausted from the battery module 130 all at once is formed. An exhaust hose 104 connected to the exhaust terminal 126 and exhausting hydrogen gas discharged from the battery module 130 to the outside of the battery unit 100 is installed on the exhaust terminal 126. Further, a temperature sensor 124 and a harness for measuring the temperature of the battery pack 120 are arranged on the lower surface of the battery pack 120. In order to maintain the temperature of the battery pack 120 within a predetermined range in accordance with the output of the temperature sensor 124, cooling air is supplied to the battery pack 120 from the vehicle interior using a blower fan or the like.

  Since the battery module 130 includes the protrusions 152, when the battery module 130 is provided as shown in FIG. 1, a gap between the battery modules 130 is formed between the battery modules 130 by the protrusions 152. Cooling air flows through the gap from the upper side to the lower side of the battery module 130 (down flow method). The battery module 130 is cooled by the cooling air.

The battery cells 140 to 150 include a positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution. As the electrolytic solution, an alkaline aqueous solution containing KOH or the like as an electrolyte is used. When the nickel electrode is charged, OH ⁻ in the electrolyte reacts with H ⁺ diffused from the inside of the active material to generate H ₂ O. This reverse reaction proceeds during discharge.

  In battery unit 100 in the present embodiment, humidity control sheet 200 is provided to prevent terminal 128 and bus bar modules 112 and 114 from being electrically connected to battery cover 102. As shown in FIGS. 1 and 3, the humidity control sheet 200 is provided on both side surfaces of the battery module 130 based on the arrangement of the terminals 128 and the bus bar modules 112 and 114, for example, on the inner side surface of the battery cover 102. It is done.

  FIG. 4 shows the relationship between the insulation resistance and the humidity of this electrolytic solution. The tendency of the insulation resistance of the electrolyte greatly changes at a certain humidity. In a high humidity atmosphere, the insulation resistance of the electrolyte solution becomes extremely small, and it becomes conductive. On the other hand, the insulation resistance of the electrolytic solution is generally large in a low humidity atmosphere, and the insulation state is maintained without falling into a conduction state.

  The humidity control sheet 200 contains a highly water-absorbing polymer, zeolite, and the like, and has a humidity control function of keeping humidity constant by reversibility that absorbs moisture at high humidity and releases moisture at low humidity. For this reason, it becomes possible to use repeatedly compared with calcium chloride, silica gel, etc. which are not reversible.

For example, such a humidity control sheet 200 includes a highly water-absorbing polymer alone or combined with other component polymers, which is formed into a nonwoven fabric and molded into a sheet shape. Also, it is not a superabsorbent polymer, but a zeolite (ie, calibrated porous aluminum, calcium (or sodium) silicate (for example, CaO · 2Al ₂ O ₃ · 5SiO ₂ , Na ₂ O · 2Al ₂ O ₃ · 5SiO ₂ )) can retain moisture in fine voids on its surface. The moisture absorption by the zeolite is not a simple physical adsorption and thus has a very strong moisture absorption / release capacity.

  FIG. 5 shows the moisture absorption characteristics of the humidity control sheet 200. As shown in FIG. 5, the amount of moisture absorption depends on the humidity. In a high-humidity atmosphere, a hygroscopic effect is exhibited and the atmospheric humidity is lowered. On the other hand, in a low-humidity atmosphere, a moisture-releasing action is exhibited and the atmospheric humidity is increased. The battery pack 120 is housed in a space formed by the battery cover 102 and the lower case 122, but the ambient humidity varies depending on the battery usage state, vehicle usage environment, and the like. Even when the atmospheric humidity varies as described above, a state closer to the average humidity can be maintained as shown in FIG. 6 due to the humidity control characteristics of the humidity control sheet 200 shown in FIG.

  That is, the humidity control sheet 200 absorbs moisture when the humidity is high, and lowers the atmospheric humidity in the vicinity of the terminals 128 and the bus bar modules 112 and 114. Even if the electrolyte leaks from the battery cells 140 to 150, the humidity is low. Since it is low, it is possible to avoid the phenomenon of insulation deterioration due to the electrolyte. Thereafter, when the atmospheric humidity becomes low due to the usage state of the battery, the usage environment of the vehicle, etc., the moisture can be released and returned to the original state, and then the moisture can be absorbed when the atmospheric humidity becomes high. Thus, the humidity control sheet repeatedly performs the moisture absorption function and the moisture release function, and can exhibit the moisture absorption / release function for a period longer than the battery life.

  In particular, some vehicles are often left outdoors at night. In this case, condensation may occur in the space formed by the battery cover 102 and the lower case 122, resulting in high atmospheric humidity. Even in such a case, the humidity control sheet 200 can maintain an appropriate humidity (that is, an appropriate humidity that does not cause conduction by the electrolytic solution).

  As described above, in the battery structure according to the present embodiment, the battery pack is composed of a large number of nickel hydrogen battery modules, the battery module is composed of a plurality of battery cells, and the terminals of these battery modules are connected to the bus bar. They are connected in series with modules. The battery pack is housed together with the humidity control sheet in a space formed by the battery cover and the lower case. The humidity control sheet absorbs moisture when the humidity inside the space formed by the battery cover storing the battery pack and the lower case is high, and releases moisture when the humidity is low. The battery cell contains an aqueous solution containing KOH, which is an electrolytic solution of a nickel metal hydride battery. Even if the electrolyte leaks out, if the humidity is high, the KOH may take in moisture from the air, and there is a possibility that the bus bar, terminals, and cover are connected by moisture. Since the moisture in the space formed by is absorbed, the possibility of conduction can be eliminated. Thereby, a required insulation state can be maintained. On the other hand, when the humidity inside the space formed by the battery cover and the lower case is low, moisture is released from the humidity control sheet. At this time, since the humidity inside the space is low, there is little possibility of conduction between the bus bar or terminal and the cover due to moisture. For this reason, the humidity control sheet can repeat moisture absorption and release semi-permanently. As a result, to provide a battery structure capable of maintaining an insulating state in a secondary battery in which a large number of battery cells including a water-soluble electrolyte are connected in series to obtain a high voltage and are in a semi-sealed state Can do.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a development schematic diagram of the battery pack concerning this embodiment. It is a perspective schematic diagram of the battery module which comprises the battery pack of FIG. It is sectional drawing of the battery pack of FIG. It is a figure which shows the relationship between electrolyte solution humidity and insulation resistance. It is a figure which shows the moisture absorption characteristic of a humidity control sheet. It is a figure which shows the humidity state in a battery pack.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Battery part, 102 Battery cover, 104 Exhaust hose, 108,110 Restraint pipe, 112,114 Bus bar module, 116,118 Restraint plate, 120 Battery pack, 122 Lower case, 124 Temperature sensor, 126 Exhaust terminal, 128 terminal, 130 Battery module, 138 square battery case, 140-150 battery cell, 200 humidity control sheet.

Claims (6)

A structure of a battery mounted on a vehicle, wherein the battery has a battery cell containing an aqueous solution,
Storage means for storing the battery cells in a closed space;
Holding means for avoiding dielectric breakdown caused by the aqueous solution and holding a necessary insulating state,
The battery means includes a humidity control means for expressing a moisture absorbing function and a moisture releasing function according to ambient humidity. A structure of a secondary battery mounted on a vehicle, wherein the secondary battery has a configuration in which a plurality of battery cells whose electrolyte is an aqueous solution are connected in series,
Storage means for storing the battery cells in a closed space;
A holding means for avoiding dielectric breakdown caused by the electrolyte and holding a necessary insulating state,
The battery means includes a humidity control means for expressing a moisture absorbing function and a moisture releasing function according to ambient humidity.   2. The humidity adjusting member is a humidity adjusting member that expresses a moisture absorbing function that absorbs humidity when the surroundings are at high humidity and expresses a moisture releasing function that emits humidity when the surroundings are at low humidity. Or the battery structure of 2.   The battery structure according to claim 3, wherein the humidity adjusting member is a humidity control sheet.   The battery structure according to claim 2, wherein the electrolyte solution of the secondary battery is water-soluble.   The battery structure according to claim 2, wherein the secondary battery is a nickel metal hydride battery.

Images