JP2011090873A - Flat secondary battery module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the safety of a flat secondary battery module suitable for large current charging and discharging that is used as a power supply for an electric vehicle, etc. <P>SOLUTION: The flat secondary battery module comprises a plurality of stacked unit cells and a current blocking unit, wherein the current blocking unit has an electric path blocking mechanism that blocks an electric path by using an expansion force of an adjacent unit cell adjacent to the current blocking unit, and the unit cells are flat. In the flat secondary battery module, a bypass circuit that is connected in parallel to each of the unit cells and has a bypass resistance section and a switch section and a charge/discharge control unit having a bypass control and output section are provided. The switch section is connected to the bypass control and output section and the charge/discharge control unit has a unit cell voltage detection unit for detecting a terminal voltage of each unit cell. The bypass control and output unit controls the open/close of the switch section in such a manner that the remaining capacity of the adjacent unit cell may be larger than that of the other unit cells. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flat secondary battery module.

  Conventionally, a secondary battery for high-current charge / discharge applications used as a power source for an electric vehicle or a hybrid vehicle uses a module in which many so-called cylindrical sealed single cells (for example, 40 to 100) are connected in series, In order to improve vibration resistance, the electrode group built in the unit cell is configured by winding an electrode and a separator around a core made of resin instead of an air core.

  In order to withstand charge / discharge caused by a large current, a special device is required for the current collecting structure.

  In Patent Document 1 and Patent Document 2, a cylindrical secondary battery in which a large number of tabs (lead pieces) are provided at the ends of the long sides of an electrode, and these tabs are joined to a current collecting member by means such as ultrasonic welding. Is disclosed.

  Patent Document 3 discloses a secondary battery module having a single battery having a flexible member as a battery container or a plurality of single cells connected in series or series-parallel in a stacked state with the flexible member as a battery container. A first connecting member formed so as to face the single battery or the single battery arranged on one side among the plurality of single cells, and the single battery or the one Pushing sesame having a protruding portion that is disposed between the unit cell disposed on the side and the first connection member and that can penetrate a through hole formed in the first connection member, and the first connection A second connecting member disposed on the opposite side of the member to the push sesame and facing the first connecting member and having a joint with the first connecting member, the first and second Either one of the connecting members is disposed on the single battery or the one side And the other one is connected to an external output terminal, and when either the single cell or the plurality of single cells expands, the pushing sesame protrudes A secondary battery module is disclosed in which a portion penetrates a through hole formed in the first connecting member and the joint portion is broken.

  In Patent Document 4, in a battery group control device that controls a battery group in which a plurality of secondary batteries are connected in series, the no-load voltage of each of the secondary batteries is measured when the battery group control device is activated. A no-load voltage measuring means, a bypass circuit having a resistance and a switch for capacity adjustment, connected in parallel to each of the secondary batteries, and bypassing a charge / discharge current flowing through each of the secondary batteries, A time for bypassing the charging / discharging current flowing through each of the secondary batteries is calculated so that the remaining capacity of each of the secondary batteries is substantially equal, and a switch of the corresponding bypass circuit corresponding to the calculated time Control means for controlling the on-state of the secondary battery, the control means converts the no-load voltage of each of the secondary batteries measured by the no-load voltage measuring means into a remaining capacity, and Calculate the average value For a secondary battery in which the difference between the converted remaining capacity and the calculated average value of the remaining capacity exceeds a preset value, the remaining capacity and the average value of the remaining capacity at the time of charge / discharge of the battery group A battery group control device is disclosed in which a charge / discharge current flowing through the secondary battery is bypassed by controlling a switch of a corresponding bypass circuit to be in an ON state for a time corresponding to the difference in the amount of electricity.

Japanese Patent Laid-Open No. 11-312537 Japanese Patent Application Laid-Open No. 11-312510 JP 2008-153203 A JP 2007-244142 A

  Since a plurality of cylindrical batteries have low space occupancy and poor volumetric efficiency when they are arranged, a so-called flat battery using a flat container has been proposed and has a surface area compared to a cylindrical battery of the same volume. Therefore, a secondary effect of excellent heat dissipation performance can be obtained.

  In the case of a conventional sealed cylindrical battery, in the unlikely event that it becomes overcharged due to a failure or misuse of the charging device, it is installed inside the battery using the increase in internal pressure due to gas generation at the time of overcharging. It was easy to incorporate a mechanism that cuts off the current before the explosion occurred by breaking the fragile part.

  However, a so-called flat battery using a laminated battery or a flat metal container suffers from thinness, and it is difficult to incorporate such a current interrupting mechanism in each single cell. For this reason, in the unlikely event that an overcharged state occurs, there is a problem that the current cannot be interrupted and eventually fire or explosion occurs.

  On the other hand, the flat container has a feature that when the internal pressure rises, the flat side surface expands greatly compared to the cylindrical container.

  Therefore, the inventor has already cut off the electric circuit using the expansion force when the internal pressure of the single cell rises due to overcharging and the container expands adjacent to the single cell located at the end of the module. The mechanism which performs is proposed (patent document 3).

  However, the capacity of the unit cell cannot be avoided to some extent in manufacturing. For this reason, when a unit cell having a relatively large capacity is arranged adjacent to the current interrupting mechanism, even if connected in series and charged / discharged at the same current value, it is less likely to be overcharged than other unit cells. become.

  Therefore, Patent Document 3 has proposed a method in which the capacity of a single cell adjacent to the current interrupt mechanism is made 3% to 9% smaller than the capacity of other single cells. However, the method of creating and incorporating two types of single cells having slightly different capacities in advance is troublesome from the viewpoint of manufacturing and is not a desirable solution.

  An object of the present invention is to improve the safety of a flat secondary battery module suitable for large current charge / discharge used as a power source for an electric vehicle or the like.

  The flat secondary battery module of the present invention includes a plurality of stacked unit cells and a current interrupting unit, and the current interrupting unit utilizes the expansion force of an adjacent unit cell adjacent to the current interrupting unit. A flat secondary battery module in which the unit cell is a flat type, and is connected in parallel to each unit cell, and has a bypass resistor unit and a switch unit. A bypass circuit and a charge / discharge control unit having a bypass control output unit are installed, the switch unit is connected to the bypass control output unit, and the charge / discharge control unit detects a terminal voltage of each unit cell. And the bypass control output unit controls opening and closing of the switch unit, and controls the remaining capacity of the adjacent unit cells to be larger than the remaining capacity of the other unit cells. The And butterflies.

  ADVANTAGE OF THE INVENTION According to this invention, the safety | security of the flat secondary battery module suitable for large current charging / discharging can be improved.

It is a schematic block diagram which shows the secondary battery module which is an Example by this invention. It is a schematic block diagram which shows the bypass circuit of the cell which concerns on this invention. It is a schematic block diagram which shows the secondary battery system containing the charging / discharging control apparatus which concerns on this invention. It is a schematic block diagram which shows the secondary battery module which is another Example by this invention. It is a schematic block diagram which shows the secondary battery module which is another Example by this invention.

  The present invention relates to a module composed of a flat secondary battery, and more particularly to a large capacity flat secondary battery module suitable for a power source of a hybrid vehicle or an electric vehicle.

  In the flat secondary battery module of the present invention, a single battery having a single capacity is used. However, the battery measures the no-load voltage of each unit cell at the time of system startup by utilizing the fact that the terminal voltage varies depending on the remaining capacity. Here, the remaining capacity is an amount representing a state of charge (SOC) of the battery, and the larger the value, the more the battery is charged.

  Since the system can store a conversion table or conversion formula between the terminal voltage and the remaining capacity obtained in advance, the remaining capacity can be known from the no-load voltage of each unit cell. . Based on this, the remaining capacity of a unit cell (hereinafter also referred to as an adjacent unit cell) adjacent to a current blocking mechanism (also referred to as a current blocking unit) is made larger than the remaining capacity of other unit cells. Then, the time for turning on the bypass circuit provided in each unit cell is calculated, and the adjustment operation is performed.

  As a result, the unit cells adjacent to the current interruption mechanism are kept in a slightly higher charge state than the other unit cells.

  It is desirable that the remaining capacity of the adjacent unit cell is controlled to be 3 to 9% higher than the remaining capacity of the other unit cells.

  When the unit cell container is formed of an aluminum alloy or the like, it is desirable to provide an air flow path between adjacent unit cells.

  According to the present invention, even if there is a slight variation in the capacity of the unit cells, this can be compensated. In other words, in the unlikely event that the charging state of the module continues due to a failure of the charging device, the unit cell adjacent to the current interruption mechanism is first overcharged, and the container expands due to the pressure of the gas generated inside. The electric current interruption mechanism (current interruption part) is actuated to reliably interrupt the electric circuit.

  In addition, as a system which interrupts | blocks an electric circuit, the system which breaks an electric circuit mechanically using the expansion force of the adjacent cell adjacent to a current interruption part is desirable. This method can also be called a mechanism for interrupting an electric circuit (electric circuit interrupting mechanism).

  Hereinafter, the present invention will be described in detail with reference to examples.

1. Production of Single Battery A so-called lithium secondary battery using lithium transition metal composite oxide as the positive electrode active material and carbon particles as the negative electrode active material was produced. The positive electrode and the negative electrode were wound through a separator and accommodated in a flat container using a laminate film containing an aluminum foil as an intermediate layer, and then an electrolytic solution was injected to obtain a unit cell. The design capacity of the unit cell is 10 Ah.

2. Production of Module FIG. 1 is a schematic configuration diagram showing a secondary battery module according to an embodiment of the present invention.

  In this figure, eight unit cells 1 are stacked and connected in series to form a battery group, which is accommodated in a module frame 2 made of aluminum alloy. In addition, a current interrupting unit 11 is installed in a part of the module frame 2 adjacent to the unit cell 1 constituting one end of the battery group. The current interrupting part 11 includes a conductive plate 5 having a push block 4 and a narrow part 6 and a fixing plate 7 provided with a protruding part 8. The fixing plate 7 is fixed to the inner wall of the module frame 2. A pressure plate 3 is attached to the unit cell 1 constituting one end of the battery group.

  A positive electrode terminal 9 and a negative electrode terminal 10 are drawn out of the module frame 2 from the battery group.

  When the battery group expands, the pressing plate 4 is pushed by the pressure receiving plate 3, and the conductive plate 5 is broken at the narrow portion 6. Thereby, the supply of current to the battery group is interrupted.

  FIG. 2 is a schematic configuration diagram showing a bypass circuit of a unit cell according to the present invention.

  In this figure, the bipolar terminals 28 and 29 of the unit cell 21 are connected to the bypass circuit 22 by lead wires 101 (vinyl-coated wires). The bypass circuit 22 is connected to the charge / discharge control unit 25.

  The bypass circuit 22 includes a bypass resistor unit 23 and a switch unit 24, and the bypass resistor unit 23 and the switch unit 24 are connected in series. A field effect transistor (Field Effect Transistor, FET) is used as the switch unit 24 of the bypass circuit 22.

  Here, one bypass circuit 22 may be collectively installed as an integrated circuit (IC) or the like for one unit cell 21, or a plurality of bypass circuits 22 corresponding to the plurality of unit cells 21. May be collectively installed as one integrated circuit (IC) or the like. In addition, a plurality of bypass circuits 22 and a charge / discharge control unit 25 may be collectively installed as one integrated circuit (IC) or the like for a battery group in which a plurality of unit cells 21 are connected in series.

  The bypass circuit 22 is connected to the A / D conversion unit 27 of the charge / discharge control unit 25. The switch unit 24 of the bypass circuit 22 is connected to the bypass control output unit 26 of the charge / discharge control unit 25. The bypass control output unit 26 controls opening and closing of the bypass resistor.

  In addition, the charge / discharge control unit 25 includes a single cell voltage detection unit that detects a terminal voltage of each single cell 21.

3. Production of Charge / Discharge Control Device FIG. 3 is a schematic configuration diagram showing a secondary battery system including a charge / discharge control unit according to the present invention.

  In this figure, the secondary battery system 34 includes a battery group including eight unit cells 21, a bypass circuit 22 connected in parallel to each unit cell 21, and a charge / discharge control unit 25. A current interrupting unit 33 is connected to one end of the battery group, and a positive electrode terminal 31 and a negative electrode terminal 32 are provided at both ends of the battery group.

  The charge / discharge control unit 25 measures the terminal voltage of each unit cell 21 at the time of system startup, and is based on a conversion table that represents a correlation between the terminal voltage calculated in advance and recorded and the remaining capacity. The terminal voltage is converted into the remaining capacity.

  The unit cells 21 located at both ends of the battery group are referred to as adjacent unit cells. Control is performed so that the remaining capacity of the adjacent unit cell is kept higher than that of the other unit cells 21 by a signal from the bypass control output unit 26 (see FIG. 2) connected to the adjacent unit cell.

  In the present embodiment, the unit cell corresponds to a terminal voltage of about 0.01 V in the charged state range of 30 to 70% and a remaining capacity of 1%.

  In this embodiment, the design capacity of the unit cell 21 is 10 Ah. 1% of this design capacity corresponds to 0.1 Ah.

  The required discharge amount of each unit cell 21 required to keep the state of charge of the unit cell 21 adjacent to the current interrupting unit 33 3-9% higher than the state of charge of the other unit cells is the above correlation. Can be easily calculated from

  In this embodiment, the average terminal voltage of the single cells 21 in the charged state range of 30 to 70% is 3.6 V, and the bypass resistance connected to each single cell 21 is 56Ω, so that the electric power equivalent to 1% In order to discharge the amount of 0.1 Ah, the bypass circuit 22 may be turned on for about 93 minutes.

  Five types and 20 of the secondary battery modules shown in FIG. 1 were produced, and the effect of the current interruption mechanism when overcharged was examined.

  Except for the single cell adjacent to the current interruption mechanism, select 10 ± 0.05Ah and use only the single cell adjacent to the current interruption mechanism by gradually increasing the length of the electrode during winding. It was changed from 10 Ah to 11.2 Ah.

  The module thus obtained is charged and discharged at 1 C, and is left to stand for about 1 hour after adjusting the remaining capacity of the adjacent unit cells to be 3 to 9% larger than the remaining capacity of the other unit cells. Then, it was put into continuous charging at 1C. The results are as shown in Table 1. Here, 1C is a 1-hour rate charge / discharge current value (unit is A), and is 10A in this embodiment.

表中、○は電流遮断機構により安全に電流を遮断できたことを示し、×は電流遮断機構が作動する前にいずれかの単電池が破裂または発火に至ったことを示している。

In the table, ◯ indicates that the current can be safely interrupted by the current interrupting mechanism, and × indicates that one of the cells has ruptured or ignited before the current interrupting mechanism is activated.

  If the difference between the remaining capacities is 9%, even if the capacity of the unit cell adjacent to the current interrupting mechanism is 1.2 Ah, that is, 12% larger than the other unit cells, the current interrupting mechanism is activated before firing. The electric circuit was cut off and it was possible to stop it safely. If the difference between the capacity of the adjacent unit cell and the other unit cell was 0.4 Ah, that is, 4%, the remaining capacity difference could be safely stopped even if the difference was 3%.

  Since the variation in capacity at the time of actual cell manufacturing is about ± 3% at most, the configuration of this embodiment can ensure sufficient safety.

  If the difference between the remaining capacities is larger than 12%, the life of the unit cell adjacent to the current interruption mechanism is impaired, which is not desirable.

  In the secondary battery module of FIG. 1, the current interrupting unit 11 is incorporated at one end of the battery group. In order to obtain a more reliable operation, the current interrupting unit 11 is interrupted at both ends of the battery group as shown in FIG. 4. It is desirable to incorporate the part 11. If either one of the current interrupting units 11 operates, the charge / discharge current is interrupted, so that the operation becomes more reliable and the safety can be further improved.

  In general, in the case of a cylindrical battery, a current interrupting unit is incorporated in every single cell. On the other hand, in the case of the flat secondary battery module according to the present invention, if a module is formed by connecting three or more single cells in series, even if current interrupting parts are incorporated at both ends, The number of parts can be reduced as compared with the case of the cylindrical battery in which the current interrupting part is incorporated in all the unit cells, and the effect of cost reduction can be obtained.

  In FIGS. 1 and 4, a laminated battery is shown as an example. However, in the case of a flat battery using a metal container such as an aluminum alloy, when the internal pressure rises, the plane portion of the side wall becomes larger than in the case of a cylindrical battery. Since it expands, the present invention can be applied to a flat secondary battery module of a metal container in exactly the same manner.

  FIG. 5 is a schematic configuration diagram showing a flat secondary battery module using a metal container such as an aluminum alloy.

  In the present embodiment, an air flow path 51 having a width of 2 mm is provided between each unit cell 1. This is for cooling the unit cell 1 that generates heat. In this case, the module frame 2 functions as an air duct, and air is circulated through the air flow path 51 by blowing air to the module frame 2 by a fan or the like, and the unit cell 1 is cooled by forced convection heat transfer. .

  In the case of the present embodiment, even if the unit cells 1 installed at the ends other than the both ends of the module expand, the unit cells 1 (adjacent unit cells) installed at both ends of the module due to the shape change of the expanded unit cell 1. There may be a time difference before reaching the action of pushing out in the direction of the current interrupting part 11, and it may be difficult to operate the current interrupting part 11 before the expanded unit cell 1 bursts.

  For this reason, it is necessary to control the remaining capacity so that the single cells 1 (adjacent single cells) installed at both ends of the module expand first. By performing this control, that is, control for maintaining the remaining capacity of the adjacent unit cells to be larger than that of the other unit cells 1 by using the bypass circuit 22 and the charge / discharge control unit 25 shown in FIG. The charging operation of the secondary battery module can be safely stopped.

  1: single cell, 2: module frame, 3: pressure receiving plate, 4: push sesame, 5: conductive plate, 6: narrow portion, 7: fixing plate, 8: protrusion, 9: positive electrode terminal, 10: negative electrode terminal, 11: Current interruption part.

Claims (4)

  A plurality of unit cells stacked and a current interrupting unit, the current interrupting unit having an electric circuit interrupting mechanism that interrupts an electric circuit by using an expansion force of an adjacent unit cell adjacent to the current interrupting unit; A flat secondary battery module in which the unit cell is a flat type, and is connected in parallel to each unit cell, and includes a bypass circuit having a bypass resistor unit and a switch unit, and a charging unit having a bypass control output unit. A discharge control unit is installed, the switch unit is connected to the bypass control output unit, the charge / discharge control unit has a single cell voltage detection unit for detecting a terminal voltage of each single cell, The bypass control output unit controls the opening and closing of the switch unit, and controls the remaining capacity of the adjacent unit cell to be larger than the remaining capacity of the other unit cells.   The flat secondary battery module according to claim 1, wherein the electric circuit breaking mechanism mechanically breaks the electric circuit using an expansion force of the adjacent unit cell.   3. The flat secondary battery module according to claim 1, wherein the remaining capacity of the adjacent unit cells is controlled to be 3 to 9% more than the remaining capacity of the other unit cells.   The flat secondary battery module according to any one of claims 1 to 3, wherein an air flow path is provided between the unit cells.

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