JP4857710B2 - Battery pack and vehicle equipped with the same - Google Patents

Description

  The present invention relates to an assembled battery in which a plurality of battery units are connected and a vehicle equipped with the assembled battery, and more particularly to an assembled battery having a balance circuit for adjusting a potential difference between single cells and a vehicle equipped with the battery.

  2. Description of the Related Art In recent years, attention has been focused on flat secondary batteries (hereinafter referred to as flat batteries) that satisfy demands for weight reduction and thinning as various power sources. The flat battery includes a power generation element, an electrode tab, and a laminate film. The power generation element is formed by laminating a plurality of unit cell layers each including a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer alternately with a current collector. The electrode tab is connected to the power generation element and guides the current of the power generation element. Two laminate films are prepared and sealed by sandwiching the power generation element. Here, a part of the electrode tab is pulled out of the laminate film and functions as an electrode of a flat battery (see, for example, Patent Document 1).

  When such a flat battery is applied to an electric vehicle, a hybrid vehicle, or the like that requires high output, a plurality of single battery layers are connected in series to form a power generation element, thereby improving the overall output. Furthermore, by connecting the flat batteries in parallel, the battery capacity is increased and the sustainability is improved.

In a flat battery formed by connecting a plurality of unit cell layers in series, a balance circuit is connected to each unit cell layer. The balance circuit is connected to each unit cell layer via a connection terminal drawn out from each unit cell layer to the outside of the laminate film. The balance circuit discharges the high-voltage unit cell layer appropriately according to the voltage difference between the unit cell layers connected in series, thereby preventing voltage variation between the unit cell layers.
JP 2003-229117 A

  However, when flat batteries are connected in parallel as described above, it is necessary to connect a balance circuit for each cell layer. That is, as many balance circuits as the number of unit cell layers are required. For this reason, there are problems that there are many balance circuits and the cost becomes high.

  Moreover, not only flat batteries, but also when a plurality of single cells are connected in series to form a battery unit and the battery units are connected in parallel, a balance circuit is required to equalize the voltage for each single cell. is there. Therefore, similarly, there is a problem that the cost increases.

  The present invention has been made in view of the above problems, and an object thereof is to provide an assembled battery that can reduce an increase in cost due to a balance circuit.

  The assembled battery of the present invention is an assembled battery in which a plurality of battery units formed by connecting a plurality of chargeable / dischargeable cells in series are connected in parallel, and connected in the same order in the series connection of the battery units. A balance circuit that is commonly connected in parallel to the unit cells and that adjusts a potential difference between the unit cells included in the battery unit.

According to the assembled battery of the present invention, since the common balance circuit is provided for the cells in the same order in series connection, the balance circuit is provided for each battery without providing a balance circuit for each of the cells in the same order. It can be shared by the units, and the potential difference between the single cells included in the battery unit can be adjusted. Since the balance circuit can be shared, the number of balance circuits can be reduced, and the cost of the assembled battery can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 is a perspective view showing a battery pack to which a balance circuit is applied, FIG. 2 is a partial cross-sectional view of a bipolar battery taken along line 2-2 in FIG. 1, FIG. 3 is a schematic configuration diagram of a voltage regulator, and FIG. FIG. 3 is a circuit diagram showing a balance circuit. In the following, an assembled battery having four bipolar batteries is illustrated.

  As shown in FIG. 1, the assembled battery 100 includes a plurality of bipolar batteries 10 (battery units) and a voltage regulator 60.

  The internal configuration of the bipolar battery 10 is as shown in FIG.

  In the bipolar battery 10, a positive electrode active material layer 12 and a negative electrode active material layer 13 are formed at the center of both surfaces of the current collector 11 except for both ends. The positive electrode active material layer 12 and the negative electrode active material layer of the current collector 11 are formed. 13 has a structure in which a single cell layer 15 is formed with a separator 14 interposed therebetween, and a plurality of the single cell layers 15 are stacked in the same order. A material in which the positive electrode active material layer 12 is formed on one surface of the current collector 11 and the negative electrode active material layer 13 is formed on the other surface is referred to as a bipolar electrode 16. The current collectors 11 at both ends are connected to the electrodes 30 a and 30 b of the entire bipolar battery 10.

  Here, the separator 14 is, for example, a polymer skeleton formed of a resin selected from the group consisting of a polyester resin, an aramid resin, and a polyolefin resin, either alone or in combination. The separator 14 constitutes an electrolyte layer by holding a gel electrolyte or a liquid electrolyte containing an electrolytic solution of about several to 98% by weight. Moreover, the separator 14 can also hold | maintain an electrolyte by being formed with a solid electrolyte itself.

  As described above, the separators 14 and the bipolar electrodes 16 are alternately stacked to form the battery element 20.

  The battery element 20 is connected to electrode tabs 30a and 30b for drawing current. The positive electrode tab 30a is connected to the positive electrode side of the battery element 20, and the negative electrode tab 30b is connected to the negative electrode side. As shown in FIG. 1, the electrode tabs 30 a and 30 b are drawn out from opposite sides of the exterior 40.

  In addition, a connection terminal 50 is connected to each current collector 11 of the battery element 20. The connection terminals 50 are attached to the current collector while being shifted in position so as not to contact each other. As a result, as shown in FIG. 1, the connection terminals 50 are drawn side by side along the side of the exterior 40.

  The exterior 40 is formed by two laminate sheets 41. The laminate sheet 41 has a three-layer structure in which both surfaces of an aluminum layer are covered with a resin layer. At least one of the laminate sheets 41 is processed into a medium-high shape in order to provide a space that encloses the battery element 20. The edge of the laminate sheet 41 is bonded by heat fusion or the like. Thereby, the battery element 20 is sealed inside the exterior 40.

  The bipolar battery 10 is electrically connected in parallel via a bus bar 25.

  As shown in FIG. 1, the voltage adjustment device 60 is connected to each connection terminal 50 of the bipolar battery 10 via a wiring 61. Although a part of the wiring 61 is omitted in FIG. 1, the number of wirings 61 is actually provided as many as the number of connection terminals 50.

  As shown in FIG. 3, the main body 70 of the voltage adjusting device 60 includes a balance circuit 71 that adjusts the voltage between the unit cell layers 15, and a resistor 72 provided around the balance circuit 71. The voltage adjusting device 60 is connected in parallel with the unit cell layer 15 in each bipolar battery 10 shown as a series connection of the unit cell layers 15 via the connection terminals 50 and the wiring 61 described above.

  The balance circuit 71 is connected in parallel with the bipolar battery 10. Here, the balance circuit 71 is composed of the unit cell layers 15 connected in the same order among the unit cell layers 15 connected in series in the bipolar battery 10, for example, four units of the first layer from the top. The battery layer 15 is commonly connected in parallel.

  The balance circuit 71 is, for example, a circuit as shown in FIG. The balance circuit 71 is configured such that when charging, when the unit cell layer 15 becomes equal to or higher than a predetermined voltage, for example, 3.6 V or more, a current flows through the unit cell layer 15 so as to bypass the unit cell layer 15. The potential difference between the layers 15 is adjusted. Further, at times other than charging, the unit cell layer 15 having a higher voltage than the other unit cell layers 15 is discharged, and the voltages between the unit cell layers 15 connected in series are made uniform.

  The resistor 72 is provided on a conductive path between the balance circuit 71 and each cell layer 15. Resistor 72 limits the current through balance circuit 71.

  Next, the operation of the voltage regulator 60 will be described. For ease of explanation, attention is paid to the balance circuit 71 and the resistor 72 in the region surrounded by the dotted line R in FIG. 3, that is, the balance circuit 71 and the resistor 72 connected to the unit cell layers 15 in the same order in series connection. Now, the operation of the voltage adjusting device 60 will be described.

  FIG. 5 is a circuit diagram showing an extracted portion indicated by a dotted line in FIG.

  In FIG. 5, the resistance value of the total resistance 72 is 125Ω, and the balance circuit 71 bypasses the current when the voltage of the unit cell layer 15 becomes 3.6 V or more. Further, it is assumed that a micro short circuit occurs in the single cell layer 15A at the left end in the drawing, and a self discharge of 0.8 mA per 1 Ah of capacity occurs.

  Since the balance circuit 71 is connected in parallel with each unit cell layer 15, a current flows so as to bypass the unit cell layer 15 having a voltage of 3.6 V or more during charging. In this way, by providing the balance circuit 71, it is possible to prevent each cell layer 15 from being overcharged.

  Further, since the single cell layer 15A self-discharges by 0.8 mA per capacity 1 Ah, a potential difference is generated with the other single cell layers 15 after a while. When the predetermined potential difference is reached, a current flows from the single battery layer 15 other than the self-discharged single battery layer 15A to the single battery layer 15A, and the single battery layer 15A is charged. Here, the predetermined potential difference at which charging between the cell layers 15 is started varies depending on the resistance value of the resistor 72 around the balance circuit 71. In the case of the example shown in FIG. 5, since the resistance 72 is set to 125Ω, charging between the single battery layers 15 is started when the potential difference becomes 0.2V.

When charging between the single cell layers 15 starts, current is sent from each single cell to the single cell layer 15A by 0.2 mA per capacity 1 Ah, and the single cell layer 15A is charged with a total current of 0.6 mA. Therefore, the place where the single cell layer 15A discharges by 0.8 mA is suppressed to the discharge of 0.2 mA.

  How the voltage is balanced in the entire assembled battery 100 by the voltage regulator 60 will be described in more detail with reference to FIGS. 6 and 7.

  FIG. 6 is a circuit diagram of an assembled battery to which the voltage regulator is applied, and FIG. 7 is a diagram showing a relationship between time and voltage in the assembled battery.

  In FIG. 6, one single cell layer 15A is self-discharged by a micro short circuit. A group of single battery layers 15 included in the same bipolar battery 10 as the single battery layer 15A is referred to as group B. A group of unit cell layers 15 included in other bipolar batteries 10 connected in the same order as the unit cell layer 15A is referred to as a group C. The other 15 cell layer groups are set as group D.

  The entire battery pack 100 is charged and left as it is. After a while, due to self-discharge of the single cell layer 15A, a potential difference of 0.2 V is generated between the single cell layer 15A and the entire group B, and the entire groups C and D. Subsequent voltage displacement of each group is as shown in FIG.

  Since there is a potential difference between the single cell layer 15A and the entire group B and the entire groups C and D, current flows from the groups C and D to the single cell layer 15A and the group B via the wiring 61 of the voltage regulator 60. . As a result, the unit cell layer 15A and each unit cell layer 15 of the group B are charged.

  In the single cell layer 15A, the rate of voltage drop due to self-discharge is relaxed, and the voltage gradually drops. On the other hand, the voltage of group B increases. Then, the potential difference between the unit cell layer 15A and the group B increases.

  When the potential difference between the unit cell layer 15A and the group B is expanded, the potential difference as a whole of the unit cell layer 15A and the group B and the groups C and D is balanced (time t1). When balanced, charging from groups C and D stops.

  At this time, the single battery layer 15A is not charged from the groups C and D, and thus self-discharge is not reduced. However, there is a large potential difference between the cell layer 15A and the group C. Therefore, charging from the group C to the single cell layer 15A starts by the operation described with reference to FIG. Thereby, the discharge of the cell layer 15A is continuously reduced.

  In the example shown in FIG. 6, the discharge of the single battery layer 15A is reduced to about 1/4 of the self-discharge. Due to charging of the single cell layer 15A, the voltage of the group C also decreases in the same manner as the single cell layer 15A. As the voltage decreases, the balance circuit 71 adjusts the voltage between the unit cell layers 15 by decreasing the voltages of the groups B and D. That is, since the voltage drop of the single cell layer 15A is ¼ of the case of self-discharge, the single cell layers 15 of the groups B and D are discharged by the balance circuit 71 with the same discharge current.

  When the balance circuit 71 is simply attached to each unit cell layer 15 as in the prior art, the other unit cell layers 15 are also discharged by the balance circuit 71 in the same manner as the self-discharge of the unit cell layer 15A. On the other hand, when the voltage adjusting device 60 is applied, the self-discharge of the single cell layer 15A and the discharge of the other single cell layers 15 can be reduced to 1/4 of the conventional one. Therefore, the time required to deviate from the voltage range that can be used as the assembled battery 100 and reach a failure can be four times that of the conventional battery.

  As described above, by applying the voltage regulator 60 that combines the balance circuit 71 and the resistor 72, the following effects can be obtained.

  Since the balance circuit 71 is provided in common to the single battery layers 15 in the same order of different bipolar batteries 10, the balance circuit 71 is compared to the case where the balance circuit 71 is attached to each single battery layer 15 as in the prior art. Can be reduced. Therefore, the manufacturing cost of the assembled battery 100 can be reduced.

  Further, since the resistor 72 is provided around the balance circuit 71, the current flowing through the balance circuit 71 is limited, and the balance circuit 71 can be prevented from being destroyed.

  In addition, when a predetermined potential difference is generated between the unit cell layers 15 due to the provision of the resistor 72, charging of the unit cell layer 15A that is self-discharged between the unit cell layers 15 is started. Therefore, since the single battery layer 15A that is self-discharged can be charged by another single battery layer 15, the discharge of the single battery layer 15A can be reduced. Even if one single cell layer 15 loses power of a predetermined ratio or more of the capacity, it cannot be used as the assembled battery 100 as a whole. However, since the discharge can be reduced by applying the voltage adjusting device 60, as a result, even if a minute short circuit occurs in one single cell layer 15, the time until failure occurs is increased. In addition, by charging after the failure is detected, the time from the failure detection until the battery becomes unusable becomes longer, and the battery can be used for a certain amount of time after the failure.

  In the above embodiment, the value of the resistor 72 provided in the voltage regulator 60 is set to 125Ω, but is not limited to this. The resistance value may be any value as long as it satisfies the following condition.

  The first condition is a lower limit value of the resistance value. The lower limit value of the resistance value is not less than a value necessary for protecting the balance circuit 71 by limiting the current flowing into the balance circuit 71. For example, a resistance 72 having a conductivity of 0.1 S or more per 1 Ah of capacitance is preferable.

  The second condition is an upper limit value of the resistance value. Depending on the resistance value of the resistor 72, the potential difference when charging between the cell layers 15 is started differs. In the above example, the resistance value of the resistor 72 is set so that the unit cell layer 15A is charged when the potential difference between the unit cell layer 15A and the other unit cell layer 15 becomes 0.2V. However, at least when the potential difference is 0.3 V or more, charging may be performed. This is because, if the potential difference becomes too large and charging between the single cell layers 15 is started, a certain single cell layer 15 becomes unusable immediately. In this case, the meaning of charging between the cell layers 15 is lost. Therefore, it is considered to balance so that 50% of the maximum capacity is lost by self-discharge in about 3 months. Then, it is preferable that the resistance value is 0.0001 S or less per 1 Ah of capacitance.

  In summary, the resistance value of the resistor 72 is preferably 0.1S to 0.0001S.

(Modification 1)
Next, a modification of the above embodiment will be described.

  In the above embodiment, the case where a plurality of bipolar batteries 10 are arranged side by side and connected in parallel has been described. However, a plurality of bipolar batteries 10 may be stacked in the stacking direction of the separator 14 and the bipolar electrode 16 and connected in parallel. Also in this case, the voltage regulator 60 can be applied.

FIG. 8 is a perspective view showing an assembled battery in which two bipolar batteries are stacked and connected in parallel, and FIG.
FIG. 10 is a cross-sectional view of the assembled battery taken along line 9-9, and FIG. 10 is a side view of the assembled battery.

  In the assembled battery 80 of Modification 1 shown in FIG. 8, two bipolar batteries 10 are stacked and connected in parallel. As shown in FIG. 9, the assembled battery 80 includes a positive electrode plate 81 that contacts both outermost layers of the stack, and a negative electrode plate 82 that is disposed at the center of the stack.

  The two bipolar batteries 10 are arranged symmetrically with respect to the negative electrode plate 82. That is, in any bipolar battery 10, the current collector 11, the negative electrode active material layer 13, the separator 14, and the positive electrode active material layer 12 are sequentially laminated from the negative electrode plate 82 to the positive electrode plate 81.

  As shown in FIGS. 8 and 10, a connection terminal 84 is attached to each bipolar electrode 16 on the same side. For example, the connection terminal 84 is formed integrally with the current collector 11 by projecting a part of the current collector 11. Alternatively, the connection terminal 84 may be fixed with a part interposed between the current collector 11 and the positive electrode active material layer 12 or the negative electrode active material layer 13.

  In the same bipolar battery 10, each connection terminal 84 is attached at a different position when viewed in a plane orthogonal to the stacking direction. However, between the bipolar batteries 10 on the upper and lower sides of the negative electrode plate 82, the connection terminals 84 for connecting the single battery layers 15 arranged in the same order in series connection in parallel to the balance circuit 71 are viewed in a plane orthogonal to the stacking direction. Installed in the same position. For example, as shown in FIG. 10, attention is paid to the unit cell layer 15 closest to the negative electrode plate 82, that is, the unit cell layer 15B connected in the lowest order in series connection. The connection terminal 84A connected to the negative electrode active material layer 13 side of the unit cell layer 15B extends at the same position when viewed in a plane orthogonal to the stacking direction. Further, the connection terminal 84B connected to the positive electrode active material layer 12 side of the single cell layer 15B extends at the same position when viewed in a plane orthogonal to the stacking direction. The connection terminals 84C are attached to the same position, and the connection terminals 84D are also attached to the same position.

  As shown by a dotted line in FIG. 10, the connection terminals 84 </ b> A, the connection terminals 84 </ b> B, the connection terminals 84 </ b> C, and the connection terminals 84 </ b> D are connected, and the balance circuit 71 is connected between them. 15 are connected in parallel. The resistor 72 is not shown.

  According to such an assembled battery of Modification 1, in addition to the effects of the above embodiment, the following effects can be obtained.

  Since the connection terminals 84 are attached to the unit cell layers 15 of the same rank in the same position as viewed in a plane orthogonal to the stacking direction, the balance circuit 71 can be easily connected in parallel. Here, the balance circuit 71 is connected by spot welding, ultrasonic welding, solder, or the like.

  Moreover, in the assembled battery 80 of a modification, since the bipolar batteries 10 are stacked and connected in parallel, the assembled battery can be reduced in size.

  Note that the connection terminal 84 is preferably point-symmetric with respect to the center of each bipolar battery 10 indicated by the intersection of the virtual lines in FIG. As described above, if the positions where the connection terminals 84 are connected are regularly determined, even when the bipolar battery 10 is arranged above and below the negative electrode plate 82 as shown in FIG. If attention is paid to the stacking order of the electrodes 16, the connection terminals 84 can be easily aligned.

(Modification 2)
Furthermore, the modification of the said embodiment is demonstrated.

  In the said embodiment, the case where the bipolar battery 10 which connected the several cell layer 15 in series was further connected in parallel was demonstrated. However, the voltage regulator 60 can be applied to other forms. For example, the voltage regulator 60 includes a parallel connection of the bipolar battery 10 including the single battery layer 15 and a series connection battery group (battery unit) formed by connecting a plurality of independent single batteries different from the single battery layer 15 in series. It can also be applied to assembled batteries.

  FIG. 11 is a diagram showing an assembled battery in which a bipolar battery and a series-connected battery group are connected in parallel.

  In the second modification, the voltage regulator 60 is applied to the assembled battery 90 in which bipolar batteries, which are different types of batteries, and a series-connected battery group are connected in parallel.

  Here, it is assumed that the bipolar battery 10 shown in FIG. 11 includes three cell layers 15 connected in series inside. Further, the connection terminal 50 connected to the negative electrode of the single cell layer 15 in the lowermost layer in the bipolar battery 10 is drawn to the lowermost side in FIG. The connection terminal 50 connected to the positive electrode of the lowermost cell layer 15 and the negative electrode of the middle cell layer is drawn second from the bottom in FIG. As described above, in FIG. 11, it is assumed that the connection terminals 50 are connected in order from the lower electrode, and are drawn in order from the lower side in FIG. 11.

  The series-connected battery group 91 is configured by connecting a plurality of independent batteries 92 in series. Each battery 92 is manufactured to have substantially the same voltage as the unit cell layer 15 positioned in the same order in series connection in the bipolar battery 10.

  In the second modification, as shown in FIG. 11, the cell layers 15 and the batteries 91 having the same rank in the series connection in the bipolar battery 10 and the series connection battery group 91 are connected in parallel with the balance circuit 71.

  As described above, the voltage regulator 60 can also be applied to different types of batteries, that is, the bipolar battery 10 and the series-connected battery group 91. In this case, the voltage of each cell layer 15 and the battery 92 is balanced by a small balance circuit 71, and even if some of the cell layers 15 and the battery 92 are short-circuited, the other cells 15, 92 The time until failure can be extended by charging.

  The assembled batteries 80, 90, 100 of the above embodiment can be mounted on a vehicle and used as a driving power source. A vehicle using the assembled batteries 80, 90, 100 as a motor power source is an automobile whose wheels are driven by a motor, such as an electric vehicle or a hybrid vehicle.

  For reference, FIG. 12 shows a schematic diagram of an automobile 110 on which the assembled battery 100 is mounted. The assembled battery 100 mounted on the automobile has the characteristics described above. For this reason, an automobile having the assembled battery 100 mounted thereon can reduce manufacturing costs because it has few balance circuits.

It is a perspective view which shows the assembled battery to which the balance circuit is applied. It is a partial cross section figure of the bipolar battery shown along the 2-2 line of FIG. It is a schematic block diagram of a voltage regulator. It is a circuit diagram which shows a balance circuit. It is a circuit diagram which extracts and shows the part shown with the dotted line of FIG. It is a circuit diagram of an assembled battery to which the voltage regulator is applied. It is a figure which shows the relationship between time and voltage in an assembled battery. It is a perspective view which shows the assembled battery which laminated | stacked two bipolar batteries and connected in parallel. It is sectional drawing of the assembled battery shown along the 9-9 line of FIG. It is a side view of an assembled battery. It is a figure which shows the assembled battery which connected the bipolar battery and the series connection battery group in parallel. It is the schematic of the motor vehicle carrying an assembled battery.

Explanation of symbols

10 ... Bipolar battery,
11 ... current collector,
12 ... positive electrode active material layer,
13 ... negative electrode active material layer,
14 ... separator
15, 15A ... single cell layer,
16: Bipolar electrode,
20 ... Battery element,
30a ... positive electrode tab,
30b ... negative electrode tab,
40 ... exterior,
50, 84 ... connection terminals,
60 ... Voltage regulator,
61 ... wiring,
70 ... body,
71 ... Balance circuit,
72 ... resistance,
80, 90, 100 ... assembled battery,
92 ... Battery,
110: Car.

Claims (7)

A battery unit in which a plurality of chargeable / dischargeable cells are connected in series, and a plurality of battery units connected in parallel,
A battery pack having a balance circuit that is connected in parallel to the cells connected in the same order in series connection of the battery units and adjusts a potential difference between the cells in the same order included in the battery unit. . It further includes a resistor provided on a conductive path that connects the balance circuit and the unit cell in parallel,
2. The assembled battery according to claim 1, wherein the resistor has at least a resistance value sufficient to prevent a current greater than a current value at which the balance circuit is destroyed from flowing into the balance circuit.   The assembled battery according to claim 2, wherein the resistor has a resistance equal to or lower than a resistance value through which a current flows when a potential difference between the cells in the same order becomes 0.3V. As the battery unit,
At least one bipolar battery;
Other bipolar batteries or series connected battery groups or a combination thereof connected in parallel to the bipolar battery,
Including
The bipolar battery is formed by alternately laminating a bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte layer. The unit cell is composed of a material layer, the electrolyte layer, and the negative electrode active material layer,
The assembled battery according to any one of claims 1 to 3, wherein the series-connected battery group includes a plurality of unit cells configured in series. The battery units are all the bipolar batteries,
The bipolar batteries are stacked in the stacking direction of the bipolar electrode and the electrolyte layer,
Each of the bipolar electrodes of the bipolar battery is provided with a connection terminal for connecting the cells of each rank and the balance circuit in parallel,
5. The assembled battery according to claim 4, wherein the connection terminals for connecting the single cells of the same order in the bipolar battery in parallel to the balance circuit are attached at the same position when viewed in a plane orthogonal to the stacking direction. .   The assembled battery according to claim 5, wherein the plurality of connection terminals are attached to the same side with respect to each of the bipolar electrodes, and are located on a point object with respect to the center of the stack.   A vehicle comprising the assembled battery according to any one of claims 1 to 4 as a driving power source.

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