JP2006269345A - Overvoltage detecting method, device, and battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily detect the occurrence of an overvoltage-state cell in a battery pack or an assembled battery having a laminate outer package cell. <P>SOLUTION: A plurality of laminate outer package cells 100 are laminated on its thickness direction, a pressure sensor 120 are inserted into one of laminate surfaces between adjoining laminate outer package cells and surface pressure (contact pressure) acting on the laminate surface is measured in a laminate body of such a laminate outer package cell. When a detected contact pressure is over a threshold, generation of overvoltage is distinguished at least at a laminate outer package cell. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and apparatus for detecting an overvoltage in a secondary battery, and more particularly, a method and apparatus for detecting an overvoltage in a secondary battery covered with a laminate, and the generation of an overvoltage cell by such a method. The battery pack.

  In recent years, secondary batteries such as lithium ion batteries and nickel metal hydride batteries have been widely used, and these secondary batteries are also used as power sources for driving electric motors in hybrid electric vehicles and the like. It is becoming.

  In power applications such as electric motor drive, it is required that a high voltage and a large current can be supplied. However, the voltage output from the unit cell (unit battery) of the secondary battery is a relatively low voltage determined by the type of the secondary battery, such as 3.6 V for a lithium ion battery. In addition, since the unit cell itself cannot be made so large in order to allow the unit cell to operate stably, the current that can be output from the unit cell is also larger than the current required for driving an electric motor or the like. It is getting smaller. Further, there is a limit to the capacity value that can be realized by one unit cell. Therefore, in order to obtain a required voltage, current, or capacity value, it is common to configure an assembled battery by connecting a plurality of unit cells of a secondary battery in parallel and / or in series. . In the following description, a battery in which a plurality of secondary battery cells are connected is referred to as an assembled battery, and a battery pack in which the battery pack is accommodated in a container is referred to as a battery pack. The battery pack may incorporate a control circuit for managing charge / discharge with respect to the assembled battery constituting the battery pack.

  In an assembly such as a battery pack having a plurality of cells, in order to increase the battery capacity per volume, it is effective to increase the volume that the cells effectively occupy in the assembly. It is preferable that the gap formed between the cells when the cells are accumulated is small. It is also preferable to suppress an increase in mass due to the exterior of the cell. As a battery that is lightweight and thin and can improve space utilization efficiency, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-203524) discloses a metal layer such as aluminum and a heat-weldable resin layer as an adhesive layer. Thus, a battery using a laminate material laminated as a thin laminate for an exterior body has been developed. Such a laminate generally has a structure in which both surfaces of a thin metal layer such as aluminum are covered with a thin resin layer, is resistant to acids and alkalis, and is lightweight and flexible.

  FIG. 1 shows an example of a flat battery having a laminate material as an outer package, that is, a laminate outer battery 100. Here, a flat battery configured as a lithium ion battery is shown. In the exterior body 101 made of a laminate material, an electrode group in which a positive electrode and a negative electrode are sandwiched by separators and an electrolyte solution are hermetically stored. A positive electrode terminal 103 connected to the positive electrode extends from one side of the outer package 101, and a negative electrode connected to the negative electrode from a side facing the side where the positive electrode terminal 103 extends. A terminal 104 extends.

  In order to achieve a desired voltage, current, and capacity value, such a laminate-clad battery 100 is laminated in the thickness direction, and the plurality of laminate-clad batteries are connected in series and / or in parallel. And you have a battery pack.

FIG. 2 is a cross-sectional view illustrating a battery pack that uses a laminated battery as a cell. In the illustrated example, six laminated exterior batteries 100 are stacked to form one set, and a plurality of such stacked sets are accommodated in the battery case 110. The wiring form between the laminate-sheathed batteries is not shown in FIG. 2 because various types are conceivable depending on the desired voltage value and capacity value. The bottom plate 111 of the battery case 110 is in contact with the bottom surface of the lowermost layered laminated battery, and the top plate 112 of the battery case 110 is the upper surface of the uppermost layered laminated battery. It is in contact. In order to properly hold and fix the laminate-clad battery 100 in the battery case 110, that is, to prevent the laminated shape of the laminate-clad battery 100 from being deformed and the individual batteries from moving, The distance between the bottom plate 111 and the top plate 112 is determined according to the thickness and the number of stacked layers of each laminated outer battery 100. When the laminated outer battery is housed in the battery case 110 and the battery pack is assembled, Torque management is performed when at least one of the top plates 112 is screwed to the main body of the battery case 110 so that the surface pressure, that is, the contact pressure on the laminated surfaces of the laminated exterior batteries 100 is within a predetermined range. This surface pressure is, for example, about ^2.5 N / cm ² .

  By the way, in an assembled battery (or battery pack) in which cells are connected in series to output a voltage larger than the voltage between the terminals of the unit cell, charging is the lowest in series connection of cells constituting the assembled battery. This is done by connecting the potential terminal and the highest potential terminal to the charging power source. However, the state of charge and the remaining capacity vary from cell to cell due to the influence of variations in characteristics among the cells constituting the assembled battery. Therefore, in an assembled battery having tens or hundreds of cells, in order to effectively use the battery capacity of the entire assembled battery while preventing the occurrence of overcharged or overdischarged cells, It is not enough to control the charge and discharge by monitoring the voltage, and measure the terminal voltage for each cell or for several cells, and for each individual cell or for several cells. It is necessary to grasp the charge state of each cell. A battery pack made of such an assembled battery has a measurement circuit that measures the terminal voltage for each cell or a group of several cells, and a battery pack that is connected to the battery pack according to the measurement result of the measurement circuit. A control circuit for controlling charging / discharging is often incorporated.

Moreover, in an assembled battery, overvoltage may occur in a specific cell even if the assembled battery as a whole is not fully charged due to variations in characteristics between cells or generation of defective cells. . When an overvoltage is generated in the secondary battery, the electrolytic solution is decomposed, which may cause leakage of the electrolytic solution or rupture of the secondary battery. It is necessary to maintain the assembled battery so that cells in an overvoltage state do not occur, and to be able to quickly detect when cells in an overvoltage state occur. The occurrence of overvoltage can also be detected based on the terminal voltage measured by the above-described measurement circuit incorporated in the battery pack. For example, Patent Document 2 (Japanese Patent Laid-Open No. 2001-102092), Patent Document 3 (Japanese Patent Laid-Open No. Hei 8). -14280) and Patent Document 4 (Japanese Patent Laid-Open No. 8-140272), a pressure sensor is provided inside the cell based on the fact that the pressure rises due to decomposition of the electrolytic solution inside the cell in an overvoltage state. An assembled battery (battery pack) is disclosed that detects the occurrence of an overvoltage cell based on a detection result from a sensor.
JP 2002-203524 A JP 2001-102092 A JP-A-8-14280 Japanese Patent Laid-Open No. 8-140272

  As described above, the occurrence of an overvoltage cell in a battery pack or an assembled battery is performed by using a measurement circuit for measuring a terminal voltage for each cell or a group of several cells for charge / discharge control. Can be detected. However, in order to prevent electrolyte leakage and cell rupture, it is necessary to be able to reliably detect cells in an overvoltage state. From that point of view, it is separate from the terminal voltage measurement circuit for charge / discharge control. It is preferable to be able to detect cells in an overvoltage state. In particular, even when a failure occurs in the terminal voltage measurement circuit or the like, it is preferable that the occurrence of an overvoltage cell can be detected to prevent danger.

  The method of detecting an overvoltage cell by measuring the internal pressure of the cell can be executed independently from the terminal voltage measurement circuit for charge / discharge control. In order to detect the occurrence of an overvoltage condition, it is necessary to measure the internal pressure in all cells, and a pressure sensor must be provided in each cell. Therefore, in a battery pack that combines several hundred cells, Is not a realistic method in terms of cost and manufacturing.

  Accordingly, an object of the present invention is to provide an overvoltage detection method and apparatus capable of easily detecting the occurrence of an overvoltage cell in a battery pack or an assembled battery, and a battery pack protected by such an overvoltage detection method. There is.

  The overvoltage detection method of the present invention is an overvoltage detection method for detecting the occurrence of overvoltage in at least one laminate-coated battery constituting a laminate in which a plurality of laminate-coated batteries are laminated in the thickness direction. The contact pressure on at least one laminated surface between the laminated exterior batteries or the contact pressure on the contact surface between the laminated body and the holding member that holds the laminated body is detected, and the contact pressure exceeds a predetermined threshold value. In this case, it is determined that an overvoltage has occurred.

  Another overvoltage detection method of the present invention is an overvoltage detection method for detecting the occurrence of an overvoltage in a laminate-clad battery, wherein the contact pressure at the contact surface between the laminate-clad battery and the holding member that holds the laminate-clad battery is detected. When the contact pressure exceeds a predetermined threshold value, it is determined that an overvoltage has occurred.

  An overvoltage detection device of the present invention is an overvoltage detection device that detects the occurrence of overvoltage in at least one laminate-covered battery constituting a laminate in which a plurality of laminate-wrapped batteries are stacked in the thickness direction. A pressure sensor that is disposed on at least one laminated surface between laminated exterior batteries or a contact surface between the laminated body and a holding member that holds the laminated body, and detects a contact pressure on the laminated surface or the contact surface; and a contact pressure And determining means for determining that an overvoltage has occurred when the value exceeds a predetermined threshold value.

  The battery pack of the present invention includes a laminate in which a plurality of laminate-clad batteries are laminated in the thickness direction, and the laminate is accommodated, and a predetermined contact pressure is applied along the lamination direction of the laminate-clad batteries in a state where no overvoltage occurs. Arranged on the contact surface between the battery case to be applied to the laminate and the laminated outer battery in the laminate, or the contact surface between the laminate and the battery case, and the contact pressure on the laminate surface or the contact surface is adjusted. A pressure sensor to detect, a determination means for determining that an overvoltage has occurred when the contact pressure exceeds a predetermined threshold, and a determination to determine whether an overvoltage has occurred. And a blocking means for blocking the charging / discharging path.

  In the present invention, the exterior of the laminated battery has flexibility, and when an overvoltage is applied to the extent that the electrolyte solution in the battery is decomposed, the exterior is expanded by the gas generated by the decomposition of the electrolyte solution. It was made with attention. By detecting the swelling of the exterior as an increase in contact pressure, it is possible to detect an overvoltage in the laminated exterior battery.

  In particular, when a laminate is configured by laminating a plurality of laminate-clad batteries, an overvoltage is generated in any one laminate-clad battery and the exterior swells, whereby each laminate between laminate-clad batteries in the laminate is obtained. The contact pressure increases on all of the surfaces and the contact surfaces between the holding member that holds the laminate and the laminate. This increase in contact pressure can be detected by placing a pressure sensor on at least one laminated surface between the laminate-clad batteries or any contact surface between the laminated body and the battery case. As a result, if one pressure sensor is provided for each laminate, it is possible to reliably detect the occurrence of overvoltage even in an assembled battery or battery pack composed of a large number of laminated exterior batteries.

  The present invention has an effect that it is possible to reliably detect an overvoltage associated with the decomposition of the electrolytic solution only by detecting an increase in the contact pressure due to the expansion of the exterior of the laminated battery. In particular, when a laminate is configured by laminating a plurality of laminate-clad batteries, it is possible to reliably and easily detect the occurrence of overvoltage cells in the laminate by measuring the contact pressure at one location for each laminate. can do. As a result, the number of sensors for detecting overvoltage can be greatly reduced. Moreover, since the detection of the overvoltage cell according to the present invention is performed separately from the measurement of the voltage between terminals of each laminated battery, when the overvoltage detection is performed by monitoring the voltage between terminals for charge / discharge control. In this case, a double detection means for detecting an overvoltage is configured, and it becomes possible to more reliably prevent damage to the battery due to the overvoltage.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a perspective view for explaining the principle of the overvoltage detection method according to the present invention.

  In the present invention, it is assumed that a laminated battery is used as a battery constituting an assembled battery or a battery pack. Then, a plurality of laminate-clad batteries 100 are laminated in the thickness direction, and in such a laminate of laminated-clad batteries, a pressure sensor is provided on any one of the laminated surfaces (contact surfaces) between adjacent laminated-clad batteries. 120 is inserted and the surface pressure (contact pressure) acting on the laminated surface is measured. As described above, the laminated body of the laminate-clad battery 100 is housed in the battery case, and the torque management is performed so that the surface pressure on the laminated surface, that is, the contact pressure is within a predetermined range. When is in a normal state, the pressure value indicated by the pressure sensor 120 should be the managed surface pressure value.

  Here, it is assumed that overvoltage has occurred in any of the laminated laminate batteries 100. The degree of overvoltage can be various, such as minor or serious, but in the case of a serious overvoltage that leads to liquid leakage or rupture in the secondary battery, the electrolyte in the secondary battery Decomposition occurs, and gas (in many cases, hydrogen) is generated in the secondary battery. When an overvoltage is generated in the laminate-clad battery 100 and gas is generated inside the battery, the laminate that is the exterior of the battery has flexibility, so that the entire laminate-clad battery 100 expands by the amount of the generated gas. Become. When one of the laminate-cased batteries 100 in the battery case expands, as described above, the laminate of the laminate-cased battery 100 is fixed in the battery case so that the height of the laminate does not change. As a result, the surface pressure on the laminated surface of the laminated battery 100 increases. As the surface pressure increases, the pressure value detected by the pressure sensor 120 also increases. Therefore, by detecting an increase in the pressure value detected by the pressure sensor 120, specifically, when the pressure value detected by the pressure sensor 120 exceeds a predetermined threshold value, the pressure sensor 120 is caught. It can be determined that in any of the laminate-coated batteries 100 constituting the laminated body, an overvoltage that accompanies decomposition of the electrolytic solution has occurred.

  Note that the battery case expands or contracts due to a change in ambient temperature, and the surface pressure on the laminated surface of the laminate-coated battery 100 may change due to the influence. Therefore, according to the method of the present embodiment, overvoltage such as generation of overvoltage cells in the battery pack having the laminated battery 100, particularly accompanied by decomposition of the electrolytic solution, regardless of changes in ambient temperature or the like. The generation of cells can be reliably detected.

  FIG. 4 shows the configuration of the battery pack according to the embodiment of the present invention. Here, six laminated exterior batteries 100 are stacked to form one set, and a plurality of such stacked sets are accommodated in the battery case 110. This battery pack is the same as that shown in FIG. 2, but a pressure sensor for measuring the surface pressure on one of the laminated surfaces between the adjacent laminated outer batteries 100 on the laminated surface. 120 is provided so as to be sandwiched between the laminated exterior batteries 100 on both sides. As the pressure sensor 120, for example, a sensor using a piezoelectric element can be used. The pressure sensor 120 may be disposed not on the laminated surface between the laminated exterior batteries 100 but on the contact surface with the bottom layer 111 of the laminated exterior batteries 100 laminated with the bottom plate 111 of the battery case 110. Alternatively, the battery case 110 may be disposed on the contact surface with the top layer of the laminated exterior battery 100 laminated with the top plate 112 of the battery case 110. In the illustrated case, the battery case 110 functions as a pressing member that holds the laminated battery 100 and the pressure sensor 120 so that the laminated battery 100 and the pressure sensor 120 are closely stacked. Become.

  FIG. 5 is a circuit diagram showing an example of the configuration of the battery pack as an electric circuit.

  The battery pack includes a battery pack including a plurality of secondary battery cells and a charge / discharge control circuit for the battery pack. As described below, the battery pack according to the present embodiment includes a laminate. An overvoltage detection circuit that detects the occurrence of an overvoltage cell based on the pressure detection value from the pressure sensor 120 disposed on the laminated surface of the exterior battery 100 is also provided.

  An assembled battery 151 is configured by connecting a plurality of laminated exterior batteries 100 in series. For the charge / discharge management, a voltage measuring unit 152 that measures a terminal voltage for each of several cells (laminated exterior batteries) is connected to the assembled battery 151. The positive electrode of the assembled battery 151 is connected to the positive terminal 155 of the battery pack via the charge / discharge control circuit 153 and the cutoff circuit 154. The negative electrode of the assembled battery 151 is directly connected to the negative terminal 156 of the battery pack. The charging / discharging control circuit 153 controls charging / discharging of the assembled battery 151 by controlling a current passing therethrough. In particular, the charging / discharging control circuit 153 supplies the assembled battery 151 to the assembled battery 151 according to the voltage measurement result in the voltage measuring unit 152. Control the charging current. The cutoff circuit 154 electrically disconnects the positive terminal 155 of the battery pack and the assembled battery 151 in an emergency or the like. The voltage measurement result in the voltage measurement unit 152 is also supplied to the state output terminal 157 of the battery pack as a state signal indicating the state of charge of the assembled battery 151.

  The discrimination circuit 158 receives a pressure detection signal from the pressure sensor 120 arranged on the laminated surface of the laminated battery 100 constituting the assembled battery 151 as described above, and the surface pressure on the laminated surface is a predetermined threshold value. Judge whether or not. The determination circuit 158 outputs an alarm signal to the cutoff circuit 154 and also to an alarm output terminal 159 of the battery pack when the detected surface pressure exceeds a predetermined threshold value. The determination circuit 158 does not output an alarm signal when the pressure detection value by the pressure sensor 120 does not exceed a predetermined threshold value.

  In such a battery pack, when an overvoltage is not generated in the laminated exterior battery constituting the assembled battery 151, the pressure measurement value in the pressure sensor 120 is also within the threshold value. Therefore, the interruption circuit 154 remains in a conductive state, and the assembled battery 151 is normally charged / discharged. On the other hand, when an overvoltage occurs in any laminated battery in the assembled battery 151 and the pressure detection value of the pressure sensor 120 exceeds the threshold value, an alarm signal is output from the determination circuit 158, and this alarm signal As a result, the cutoff circuit 154 changes to the cutoff state. As a result, the assembled battery 151 is electrically disconnected from the external circuit, and further, it is possible to prevent liquid leakage and rupture in the laminated exterior battery due to the progress of overcharge and the like. Further, since the alarm signal is also transmitted to the external circuit via the alarm output terminal 159, it is possible to execute appropriate processing on the external circuit side.

  In this battery pack, since the pressure sensor 120 and the discrimination circuit 158 are provided separately from the voltage measuring unit 152 that measures the voltage for charge / discharge control, a severe overvoltage accompanying the decomposition of the electrolyte is doubled. Therefore, the overvoltage can be detected more reliably. Even when a failure occurs in which the charge / discharge control circuit 153 cannot properly control the charging current, the interruption circuit 154 can reliably prevent the overcharge from proceeding. That is, double prevention means for overvoltage and overcharge are configured.

It is a perspective view which shows the structure of a lamination exterior battery. It is sectional drawing explaining the conventional battery pack which consists of a laminate-clad battery. It is a perspective view explaining the principle of the overvoltage detection method based on this invention. It is sectional drawing explaining the battery pack of one Embodiment of this invention. It is a circuit diagram which shows an example of a structure as an electric circuit of a battery pack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Laminated exterior battery 110 Battery case 111 Bottom plate 112 Top plate 120 Pressure sensor 151 Battery assembly 152 Voltage measurement part 153 Charge / discharge control circuit 154 Shut-off circuit 158 Discrimination circuit

Claims (7)

An overvoltage detection method for detecting the occurrence of overvoltage in at least one laminate-coated battery constituting a laminate in which a plurality of laminate-coated batteries are stacked in the thickness direction,
Detecting a contact pressure on at least one laminate surface between the laminate-clad batteries in the laminate, or a contact pressure on a contact surface between the laminate and a holding member holding the laminate,
An overvoltage detection method for determining that an overvoltage has occurred when the contact pressure exceeds a predetermined threshold value. An overvoltage detection method for detecting the occurrence of overvoltage in a laminated battery,
Detecting the contact pressure at the contact surface between the laminate-clad battery and the holding member that holds the laminate-clad battery;
An overvoltage detection method for determining that an overvoltage has occurred when the contact pressure exceeds a predetermined threshold value.   3. The overvoltage detection according to claim 1, wherein the holding member fixes the stacked body so that a predetermined contact pressure is applied to the stacked body along a stacking direction of the laminated exterior battery in a state where no overvoltage is generated. Method. An overvoltage detection device for detecting occurrence of overvoltage in at least one laminate-coated battery constituting a laminate in which a plurality of laminate-coated batteries are stacked in the thickness direction,
Arranged on at least one laminate surface between the laminate-clad batteries in the laminate or a contact surface between the laminate and a holding member that holds the laminate, and contact at the laminate surface or the contact surface A pressure sensor for detecting pressure;
A determining means for determining that an overvoltage has occurred when the contact pressure exceeds a predetermined threshold;
An overvoltage detection device.   The overvoltage detection device according to claim 4, wherein the holding member fixes the stacked body so that a predetermined contact pressure is applied to the stacked body along a stacking direction of the laminated exterior battery in a state where no overvoltage is generated. A laminate in which a plurality of laminated exterior batteries are laminated in the thickness direction;
A battery case that holds the laminate and holds the laminate so that a predetermined contact pressure is applied to the laminate along the lamination direction of the laminate-coated battery in a state where no overvoltage occurs, and
Pressure that is disposed on at least one laminated surface between the laminated exterior batteries in the laminated body, or a contact surface between the laminated body and the battery case, and detects a contact pressure on the laminated surface or the contact surface. A sensor,
A determining means for determining that an overvoltage has occurred when the contact pressure exceeds a predetermined threshold;
When it is determined that the overvoltage has occurred, a blocking unit that blocks a charging / discharging path to each laminate-sheathed battery,
Having a battery pack.   The battery pack according to claim 6, wherein the laminated outer battery is a lithium ion secondary battery.

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