JP2014053153A - Power storage module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage module capable of restraining a capacity maintenance rate from declining along with an increase in the number of charge and discharge cycles.SOLUTION: Provided is a power storage module 10 comprising a secondary battery group 12 in which a plurality of lithium ion secondary cells 11 having an electrode assembly accommodated in a case are juxtaposed, a restraining device for applying a restraint force in juxtaposed direction to the secondary battery group 12, and a restraint force change mechanism for changing the restraint force applied to the secondary battery group 12 by the restraining device, wherein a control unit 45 determines whether a change in a capacity maintenance rate SOH relative to a change in the number of charge and discharge cycles in the secondary battery group 12 is equal to or greater than a preset threshold, and, on condition that the result of the determination is positive, controls a restraint force change mechanism 40 to increase the restraint force.

Description

  The present invention relates to a power storage module including a power storage device group in which a plurality of power storage devices are arranged in parallel.

  2. Description of the Related Art Conventionally, in a power storage module mounted on a vehicle or the like, a plurality of power storage devices are arranged (stacked) in parallel to form a power storage device group, thereby achieving space saving while securing electric capacity and output voltage. Has been done. In such a power storage module, each power storage device is sandwiched between pressing members disposed at both ends of the power storage device group in the juxtaposed direction so that each power storage device does not move in a direction orthogonal to the direction in which the power storage devices are juxtaposed, Restraining is performed (for example, Patent Document 1).

  Here, each power storage device is formed by housing an electrode assembly in which electrodes having active material layers provided on the surface of a metal foil overlap each other in a layered manner. For this reason, in an electrical storage module, when an electrode assembly expand | swells with charging / discharging, there exists a possibility that the binding force provided to each electrical storage apparatus between press members may become high.

  On the other hand, in the power storage module of Patent Document 1, the current value I flowing through the power storage device group is periodically detected, and the dimensions of the piezo elements are changed based on the detected current value I, so Is adjusted to suppress an increase in binding force accompanying expansion of the electrode assembly housed in the case of each power storage device. For this reason, in patent document 1, it suppresses that the electrolyte impregnated by the active material layer is pushed out by an excessive restraining force and is depleted, and the capacity retention rate as the power storage device group is reduced.

JP 2010-160981 A

  However, in Patent Document 1, although there is an effect on a relatively gradual decrease in capacity maintenance rate due to electrolyte depletion, it is against an abrupt decrease in capacity maintenance rate due to separation of the active material layer from the metal foil of the electrode. The effect is limited. For this reason, it is expected to further suppress the decrease in the capacity maintenance rate as the number of charge and discharge cycles increases.

  This invention was made paying attention to the problem which exists in the said prior art, The objective is the electrical storage module which can suppress that a capacity | capacitance maintenance factor falls with the increase in the cycle number of charge and discharge. It is to provide.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided with a plurality of power storage devices in which an electrode assembly in which an electrode provided with an active material layer on a surface of a metal foil is layered is accommodated in a case. A power storage module comprising: a power storage device group; a restraint device that applies a restraining force to the power storage device group in a juxtaposed direction; and a restraint force change mechanism that changes the restraint force by the restraint device. Capacity maintenance rate detecting means for detecting a capacity maintenance rate of the device, a ratio of a change amount of the capacity maintenance rate to a change amount of the number of charge and discharge cycles in the power storage device, or a cumulative charge amount and the power storage in the power storage device On condition that the determination means for determining whether or not the amount of change in the capacity maintenance rate with respect to any one of the accumulated discharge amounts in the apparatus is equal to or greater than a predetermined threshold, and the determination means make an affirmative determination And gist that and a restraining force control means for increasing the restraining force by controlling the restraining force changing mechanism.

  According to this, the ratio of the amount of change in the capacity maintenance rate to the amount of change in the number of charge and discharge cycles in the power storage device, or the capacity maintenance rate for either the cumulative charge amount in the power storage device or the cumulative discharge amount in the power storage device When the amount of change is equal to or greater than a predetermined threshold, the binding force of the power storage device group is increased. For this reason, the metal foil and the active material layer are brought into close contact with each other by the binding force applied to each power storage device, and a rapid decrease in capacity maintenance rate due to the separation of the active material layer from the metal foil of the electrode can be suppressed. . Therefore, it can suppress that a capacity | capacitance maintenance factor falls with the increase in the frequency | count of a charge and discharge cycle.

  Invention of Claim 2 is an electrical storage module of Claim 1, Comprising: The said restraint force control means is 1.2 times or more of restraint force before the said judgment means affirmatively determines the restraint force 1 Increase to 7 times or less.

  According to this, since the restraining force is increased to 1.2 times or more of the restraining force before the determination means makes an affirmative determination, the metal foil and the active material layer can be brought into close contact with each other and 1.7 times or less. By doing so, it is possible to suppress depletion of the electrolyte in the active material layer due to excessive binding force.

  The invention according to claim 3 is the power storage module according to claim 1 or 2, wherein the restraining force control means sets the restraining force to a predetermined restraining force when the determination means does not make an affirmative determination. Let it be maintained.

  According to this, if the determination means does not make an affirmative determination, the restriction force is maintained at a predetermined restriction force lower than the restriction force when the determination means makes an affirmative determination. It is possible to suppress the increase in the capacity, thereby suppressing a relatively gradual decrease in the capacity maintenance rate accompanying the depletion of the electrolyte. Therefore, it is possible to further suppress a decrease in the capacity maintenance rate of the power storage device.

  Invention of Claim 4 is an electrical storage module of any one of Claims 1-3, Comprising: The said electrical storage apparatus is a secondary battery. According to this, as a power storage module including the secondary battery group, it is possible to suppress a decrease in capacity maintenance rate with an increase in the number of charge and discharge cycles.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that a capacity | capacitance maintenance factor falls with the increase in the number of cycles of charge and discharge.

The top view which shows an electrical storage module typically. The front view which shows an electrical storage module typically. The left view which shows an electrical storage module typically. The right view which shows an electrical storage module typically. The block diagram which shows the electrical constitution of an electrical storage module. The flowchart which shows a binding force change process. Explanatory drawing which shows the relationship between a capacity maintenance rate and the square root of the number of cycles.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, a power storage module 10 mounted on a vehicle includes a power storage device in which a plurality of lithium ion secondary batteries (hereinafter simply referred to as “secondary batteries”) 11 as power storage devices are arranged in parallel. A secondary battery group 12 is provided as a group.

  Each secondary battery 11 includes an electrode assembly 13 and a metal (for example, aluminum) case 14 that accommodates the electrode assembly 13. Each secondary battery 11 is a prismatic secondary battery in which the case 14 has a flat and substantially rectangular box shape.

  In the electrode assembly 13, rectangular sheet-like positive and negative electrodes each having an active material layer containing an active material capable of removing and inserting lithium ions provided on the surface of a metal foil are alternately stacked with a separator interposed therebetween. This is a stacked electrode assembly. In the following description, the “stacking direction” simply means the stacking direction (overlapping direction) of the electrodes in the electrode assembly 13.

  Further, in the case 14, one of four walls positioned in a direction orthogonal to the stacking direction of the electrode assembly 13 is positively connected to the electrode assembly 13 to extract electric power to the outside. A terminal 15 and a negative electrode terminal 16 are projected. Hereinafter, the outer surface of the wall on which the positive electrode terminal 15 and the negative electrode terminal 16 are provided is referred to as a terminal forming surface 11a.

  In the secondary battery group 12, the secondary batteries 11 are arranged side by side along the stacking direction in the electrode assembly 13, with the wall provided with the positive electrode terminal 15 and the negative electrode terminal 16 arranged on the same direction side. ing. That is, the parallel direction D1 of the secondary batteries 11 in the secondary battery group 12 coincides with the stacking direction. Each secondary battery 11 is connected in series by electrically connecting the positive electrode terminal 15 and the negative electrode terminal 16 of the adjacent secondary battery 11 with a metal plate (bus bar) 18.

  Further, the secondary battery group 12 is placed on the rectangular flat plate-like support base 21 extending along the juxtaposed direction D1, with the opposite surface of the terminal forming surface 11a being in contact therewith. Ribs 21a extending along the juxtaposed direction D1 are provided at both edges of the support stand 21 in the juxtaposed direction D1 and in a direction orthogonal to the direction perpendicular to the surface of the support stand 21 (hereinafter referred to as the width direction D2). Each is provided. The support base 21 restricts the secondary battery group 12 from moving in the width direction D2 by disposing the secondary battery group 12 between the ribs 21a.

  In addition, a metal first holding member 23 and a second holding member 24 each having a flat rectangular plate shape stand vertically with respect to the support base 21 at both ends of the support base 21 in the juxtaposed direction D1. While maintaining the installed state, it is supported so as to be movable along the juxtaposed direction D1. The holding members 23 and 24 are assembled to the support base 21 so as not to move in a direction perpendicular to the surface of the support base 21.

  The first holding member 23 is disposed on one end (base end) side of the secondary battery group 12 in the juxtaposition direction D1, while the second holding member 24 is disposed on the other end (tip end) side. Further, the holding members 23 and 24 have a length along the direction perpendicular to the surface of the support base 21 smaller than each secondary battery 11. For this reason, the end surface 23a of the first holding member 23 on the side opposite to the support base 21 and the end surface 24a of the second holding member 24 are in the state where the secondary battery group 12 is placed on the support base 21. It is located on the support base 21 side from the terminal forming surface 11 a of the battery 11.

The end surface 23 a of the first holding member 23 is provided with a plurality of (three in this embodiment) fixing portions 26 that fix the base end of the piano wire 25 as a metal wire to the first holding member 23. . Incidentally, piano wire 25 is a tensile strength, for example, 2000N / mm ² or more 3000N / mm ² or less, preferably 2000N / mm ² or more 2310N / mm ² or less, the tensile strength as compared to general steel plate Are better. Each piano wire 25 has a wire diameter of, for example, 0.26 mm or more and 1.2 mm or less, preferably 0.8 mm or more and 1.2 mm or less.

  Each fixing portion 26 has a rectangular flat plate-like base portion 26a extending along the juxtaposed direction D1, and a wall-like locking portion 26b erected from an edge portion of the base portion 26a on the second holding member 24 side. . The distal end portion of the locking portion 26 b is further bent toward the side opposite to the second holding member 24.

  As shown in FIGS. 1 and 3, in each fixing portion 26, a groove portion 26 c is formed at the center of the locking portion 26 b in the width direction D <b> 2 so as to be cut out from the distal end portion toward the base portion 26 a. The width of the groove 26 c is slightly larger than the wire diameter of the piano wire 25 and smaller than the spherical metal ball member 25 a fastened to the base end of the piano wire 25.

  Then, the piano wire 25 is inserted into the groove portion 26c in the locking portion 26b of each fixing portion 26 with the ball member 25a disposed on the opposite side of the locking portion 26b from the second holding member 24. It has been stopped. Each piano wire 25 is fixed so that the ball member 25a is brought into contact with the locking portion 26b by the tension (tension) and is not easily detached from the fixing portion 26. For this reason, in this embodiment, the spherical member 25a of the piano wire 25 is located on the support base 21 side from the terminal forming surface 11a of each secondary battery 11.

  Each fixing unit 26 is provided with a tension measuring device 30 that detects the tension of the piano wire 25. The tension measuring device 30 includes a piezoelectric element (piezo element) (not shown), and is configured to apply vibration to the piano wire 25 by applying a voltage to the piezoelectric element. The tension measuring device 30 includes a microphone (not shown), and is configured to output a detection signal corresponding to vibration (sound wave) generated on the piano wire 25 by the microphone.

  In addition, a plurality of (three in this embodiment) support members 31 are provided on the end surface 23 a of the first holding member 23 to support the piano wire 25 at a position in contact with the terminal forming surface 11 a of each secondary battery 11. Yes. Each support member 31 is paired with each fixed portion 26 on the second holding member 24 side of each fixed portion 26. As shown in FIG. 2, each support member 31 has a wall shape standing from the edge on the second holding member 24 side in the first holding member 23, and its tip surface forms a terminal of each secondary battery 11. Located on the same plane as the surface 11a.

  As shown in FIG. 1, a pair of regulating walls 31 a extending along the parallel direction D <b> 1 is provided on the front end surface of each support member 31. The regulation wall 31a is arranged slightly spaced from the wire diameter of the piano wire 25, and the piano wire 25 is arranged between the regulation walls 31a. For this reason, each regulation wall 31a has controlled that the piano wire 25 moves to the width direction D2.

  As shown in FIGS. 1, 2, and 4, the tip of each piano wire 25 has a plurality of the second holding members 24 provided in pairs with the fixing portions 26 (this embodiment). Are fixed to the three winding portions 33. Each winding portion 33 is made of a metal having a substantially cylindrical shape extending along the width direction D <b> 2, and is supported so as to be rotatable around its axis in the storage portion 35 that opens on the end surface 24 a of the second holding member 24. Yes.

  In the center of each winding part 33 in the width direction D2, an insertion hole 33a that penetrates in a direction orthogonal to the axial direction of the winding part 33 and through which the tip of the piano wire 25 is inserted is provided. And each piano wire 25 is being fixed to each winding part 33 by each winding up by the winding part 33 in the state which made the front-end | tip penetrate the insertion hole 33a. Therefore, in the present embodiment, the tip end of the piano wire 25 is located closer to the support base 21 than the terminal forming surface 11a of each secondary battery 11.

  The end surface 24a of the second holding member 24 is provided with a plurality of (three in this embodiment) support members 31 that support the piano wire 25 at a position in contact with the terminal forming surface 11a of each secondary battery 11. Yes. Each support member 31 makes a pair with each winding part 33 on the first holding member 23 side of each winding part 33. Note that the support members 31 provided on the second holding member 24 have the same configuration as the support members 31 provided on the first holding member 23, and thus description thereof is omitted.

  Accordingly, in the present embodiment, each piano wire 25 is spanned between the support member 31 provided on the first holding member 23 and the support member 31 provided on the second holding member 24, thereby each secondary battery. 11 terminal formation surface 11a is slightly touched. Each piano wire 25 is only slightly in contact with the terminal forming surface 11a of each secondary battery 11, and can vibrate relatively freely.

  As described above, in the power storage module 10 of the present embodiment, each piano wire 25 connects the holding members 23 and 24 to each other, and sandwiches the secondary battery group 12 between the holding members 23 and 24 by tension. A binding force is applied in the installation direction D1. In other words, each piano wire 25 is arranged so as to span both ends of the secondary battery group 12 in the juxtaposed direction D1. Moreover, each piano wire 25 of this embodiment is on the terminal formation surface 11a from which the positive electrode terminal 15 and the negative electrode terminal 16 of each secondary battery 11 protrude among the surfaces extended along the parallel direction D1 in the secondary battery group 12. Be placed.

  Further, a worm wheel 37 disposed in the second holding member 24 is coupled to the rotation shaft of each winding portion 33 so as to be integrally rotatable around the axis of each winding portion 33. Each worm wheel 37 has a substantially columnar shape extending in the juxtaposed direction D <b> 1 in the second holding member 24, and is supported so as to be rotatable around an axis perpendicular to the axis of the winding portion 33. 38 are meshed with each other. Each worm gear 38 is connected to an output shaft of a motor 39 such as a stepping motor fixed to the surface of the second holding member 24 opposite to the first holding member 23.

  In the present embodiment, the tension of the piano wire 25 fixed between the fixed portion 26 and the winding portion 33 by driving each motor 39 and rotating the winding portion 33 in the winding direction of the piano wire 25. Can be adjusted high, and the binding force of the secondary battery group 12 can be increased. On the other hand, in this embodiment, by rotating the winding part 33 in the reverse direction, the tension of the piano wire 25 can be adjusted to be low, and the binding force of the secondary battery group 12 can be reduced.

  As described above, in the present embodiment, the winding unit 33, the worm wheel 37, the worm gear 38, and the motor 39 constitute the binding force changing mechanism 40 that changes the binding force of the secondary battery group 12. In the present embodiment, the support base 21 (retaining members 23 and 24), the piano wires 25, the fixing portions 26, and the binding force changing mechanisms 40 are arranged in parallel with the secondary battery group 12 in the direction D1. A restraining device (variable fixing device) 41 that applies a restraining force to is configured.

  As shown in FIG. 5, the power storage module 10 includes a positive external terminal 10 a electrically connected to the positive terminal 15 of the secondary battery 11 connected to the positive end of the secondary battery group 12, and a negative end. A negative electrode external terminal 10b electrically connected to the negative electrode terminal 16 of the secondary battery 11 connected to

  Note that the vehicle device 44 is electrically connected to the power storage module 10 via the external terminals 10a and 10b. The vehicle device 44 is, for example, an electric motor as a load that consumes power or a power generation device that supplies power to the secondary battery group 12. In addition, when the power storage module 10 of the present embodiment is mounted on a vehicle or the like, the power storage module 10 can be housed in a battery housing portion having a supply passage for supplying a heat medium and a discharge passage for discharging the heat medium. .

Next, the electrical configuration of the power storage module 10 will be described.
The power storage module 10 is provided with a controller (controller) 45 that is integrally provided with a central processing unit (CPU) and a storage device (memory) (not shown). The control unit 45 is provided in the power storage module 10 such as the inside of the first holding member 23, for example.

  The storage device of the control unit 45 detects (estimates) the control program for controlling charging and discharging of the secondary battery group 12 and the operation of the binding force changing mechanism 40 and the capacity maintenance rate SOH of the secondary battery group 12. ) Is stored, and processing results (information) by the central processing unit are stored. Further, the central processing unit of the control unit 45 executes various processes according to the control program stored in the storage device, and controls, for example, discharging and charging of the secondary battery group 12 and the operation of the binding force changing mechanism 40. .

  Each tension measuring device 30 is connected to the control unit 45. The control unit 45 is configured to apply a voltage to the piezoelectric element incorporated in each tension measuring device 30 to apply vibration to the piano wire 25 and is output from a microphone incorporated in each tension measuring device 30. The detection signal can be input. The controller 45 is connected to a motor 39 of each binding force changing mechanism 40, and is configured to be able to rotate the winding unit 33 by driving each motor 39.

  The control unit 45 is connected to a voltage sensor 47 that detects the voltage value V of the secondary battery group 12, and is configured to be able to input a detection signal that the voltage sensor 47 outputs in accordance with the voltage value V. ing. The voltage sensor 47 is provided in the power storage module 10.

  The control unit 45 is connected to a current sensor 48 that detects a current value I that flows when the secondary battery group 12 is charged and discharged, and the current sensor 48 detects that the current value I is output according to the current value I. A signal can be input. The current sensor 48 is provided in the power storage module 10.

  Further, a temperature sensor 49 that detects the temperature T of the secondary battery group 12 is connected to the control unit 45, and a detection signal that is output according to the temperature T can be input. . The temperature sensor 49 is provided close to the secondary battery group 12 in the power storage module 10, for example.

  Next, a process in which the control unit 45 calculates (detects) the capacity maintenance rate SOH of the secondary battery group 12 will be described. The control unit 45 calculates the capacity maintenance rate SOH for each charging and discharging cycle of the secondary battery group 12 (hereinafter referred to as “charging / discharging cycle”).

  The control unit 45 calculates the open circuit voltage OCV of the secondary battery group 12 based on the voltage value V detected by the voltage sensor 47, the current value I detected by the current sensor 48, and the equivalent circuit parameter of the secondary battery group 12. To do. In addition, the equivalent circuit parameter of the secondary battery group 12 can be estimated from the voltage value V and the current value I. Then, control unit 45 refers to map data configured in advance by associating open circuit voltage OCV and charge rate SOC by experiments or the like, and calculates charge rate SOC from open circuit voltage OCV.

  Further, the control unit 45 calculates the capacity maintenance rate SOH of the secondary battery group 12 from the charging rate SOC and the internal resistance (internal resistance of an equivalent circuit parameter) R of the secondary battery group 12. Specifically, the control unit 45 refers to map data configured by associating the charging rate SOC, the internal resistance R of the secondary battery group 12 and the capacity maintenance rate SOH in advance through experiments or the like, and determines the charging rate SOC. The capacity maintenance ratio SOH is calculated from the internal resistance R of the secondary battery group 12.

  Since the relationship between the charging rate SOC, the internal resistance R, and the capacity maintenance rate SOH differs depending on the temperature T of the secondary battery group 12, a plurality of map data is prepared for each temperature T. Then, the control unit 45 selects map data corresponding to the temperature T detected by the temperature sensor 49, and calculates the capacity maintenance rate SOH with reference to the selected map data.

  In addition, the control unit 45 causes the storage device to store the capacity maintenance rate SOH calculated in each cycle number in association with the number of charge and discharge cycles in the secondary battery group 12. Therefore, the control unit 45 serves as a capacity maintenance rate detection unit that detects the capacity maintenance rate SOH of the secondary battery group 12.

  Next, a binding force changing process in which the control unit 45 changes the binding force of the secondary battery group 12 by the binding device 41 will be described. In addition, the control part 45 performs a binding force change process for every predetermined period (for example, 10 seconds).

  As shown in FIG. 6, the control unit 45 changes the capacity maintenance rate SOH calculated by subtracting the capacity maintenance rate SOH in the previous 200 charge / discharge cycles from the capacity maintenance rate SOH in the current charge / discharge cycle. Is determined to be 5% or more (step S1). In addition, the capacity | capacitance maintenance factor SOH in the present charging / discharging cycle and the charging / discharging cycle 200 times before is acquired from a memory | storage device.

  That is, in step S1, the control unit 45 determines whether or not the ratio of the amount of change in the capacity maintenance rate SOH to the amount of change in the number of cycles of charging and discharging in the secondary battery group 12 is equal to or greater than a predetermined threshold value. The control unit 45 functions as a determination unit.

  When the determination result of step S1 is negative (when the amount of change is not 5% or more), the control unit 45 has a predetermined binding force applied to the secondary battery group 12 in the juxtaposition direction D1. It is determined whether it is within one range (for example, 1000N or more and 1500N or less) (step S2).

  Specifically, in step S <b> 2, the control unit 45 controls each tension measuring device 30 to apply vibration to the piano wire 25, and based on the detection signal input from the tension measuring device 30, each piano wire 25. The frequency (basic frequency) of the vibration generated in

  Next, in addition to the frequency of each specified piano wire 25, the control unit 45 adds the length of the piano wire 25 stored in advance (the support member 31 of the first holding member 23 and the second holding member 24 in this embodiment). The tension generated in the piano wire 25 is calculated based on the separation distance of the support member 31 and the linear density of the piano wire 25. The control unit 45 calculates the binding force applied to the secondary battery group 12 based on the tension generated in each piano wire 25, and the calculated binding force is in the first range. It is determined whether or not.

  If the determination result of step S2 is affirmative, the control unit 45 ends the binding force change process. That is, the control unit 45 maintains the binding force of the secondary battery group 12 without changing it. On the other hand, when the determination result of step S2 is negative, the control unit 45 controls the motor 39 of each restraint force change mechanism 40 based on the restraint force calculated in step S2 and restrains it to be in the first range. The force is changed (step S3).

  Specifically, in step S <b> 3, when the calculated binding force of the secondary battery group 12 is less than the lower limit value of the first range, the control unit 45 controls the motors 39 in the direction of winding the piano wires 25. The winding unit 33 is rotated. On the other hand, when the calculated binding force of the secondary battery group 12 exceeds the upper limit value of the first range, the control unit 45 controls each motor 39 and rotates the winding unit 33 in the direction in which each piano wire 25 is sent out. . Thereafter, the control unit 45 ends the binding force changing process.

  When the determination result in step S1 is affirmative (when the amount of change is 5% or more), the control unit 45 determines that the binding force applied to the secondary battery group 12 is a second range (for example, 1300 N) determined in advance. Whether or not 1950 N or less) is determined in the same manner as in step S2 (step S4). If the determination result of step S4 is affirmative, the control unit 45 ends the binding force changing process. That is, the control unit 45 maintains the binding force of the secondary battery group 12 without changing it.

  On the other hand, when the determination result of step S4 is negative, the control unit 45 controls the motor 39 of the restraint force change mechanism 40 in the same manner as the process of step S3 based on the restraint force calculated in step S4. Restraint force is changed so that it may become the 2nd range (Step S5). Thereafter, the control unit 45 ends the binding force changing process.

  In the present embodiment, the second range (lower limit value and upper limit value) is 1.2 times or more and 1.7 times or less, preferably 1.3 times or more and 1 times the first range (lower limit value and upper limit value). .5 times or less. When the binding force of the secondary battery group 12 is 1.2 times or more, in the electrode assembly 13 of each secondary battery 11, the metal foil of the electrode and the active material layer are brought into close contact, and the active material layer is peeled off. A sudden decrease in the capacity maintenance rate SOH associated with can be suppressed. Furthermore, when the binding force of the secondary battery group 12 is set to 1.3 times or more, it is possible to more suitably suppress a rapid decrease in the capacity retention rate SOH accompanying the peeling of the active material layer.

  Further, when the binding force of the secondary battery group 12 is 1.7 times or less, it is possible to suppress the electrolyte from being pushed out from the active material layer and to be exhausted, and to suppress the capacity maintenance rate SOH from decreasing. . Furthermore, when the binding force of the secondary battery group 12 is 1.5 times or less, it is possible to more suitably suppress the decrease in the capacity retention rate SOH accompanying the electrolyte depletion in the active material layer. The control unit 45 of the present embodiment functions as a restraint force control unit that controls the restraint force changing mechanism 40 to increase the restraint force on condition that the determination result in step S1 is affirmative.

  In addition, in the control part 45, the length of the piano wire 25 mentioned above, the line density of the piano wire 25, and the 1st, 2nd range (restraint value) of the piano wire 25 are operated by operating the operation means which is not illustrated. ) Is configured so that the operator can set.

Next, the operation of the power storage module 10 configured as described above will be described.
When the ratio of the amount of change in the capacity retention rate SOH to the amount of change in the number of charge and discharge cycles in the secondary battery group 12 is equal to or greater than a predetermined threshold, the binding force of the secondary battery group 12 is increased. For this reason, due to the binding force applied to each secondary battery 11, the metal foil and the active material layer are brought into close contact with each other, and the sudden decrease in capacity maintenance rate SOH caused by the separation of the active material layer from the metal foil of the electrode Can be suppressed.

  In addition, when the ratio of the amount of change in the capacity maintenance rate SOH to the amount of change in the number of cycles is less than the threshold by repeatedly executing the binding force changing process every predetermined period, the binding force of the secondary battery group 12 Is maintained in the first range lower than the second range. For this reason, in the electrical storage module 10, it is possible to suppress a relatively gradual decrease in the capacity maintenance rate SOH accompanying the depletion of the electrolyte.

  The above measures the capacity retention rate SOH when the charge / discharge cycle is repeated for the power storage module 10 of the present invention and the power storage module of the comparative example that does not perform steps S1, S4, and S5 in the binding force change process. Confirmed by that.

  FIG. 7 shows the relationship between the capacity retention rate SOH and the square root of the number of cycles of charging and discharging with a constant current of 1 C (number of charging / discharging cycles). In FIG. 7, the capacity maintenance rate SOH of the power storage module 10 of the present invention is indicated by a solid line, and the capacity maintenance rate SOH of the power storage module of the comparative example is indicated by a dashed line.

  As shown in FIG. 7, in the power storage module of the comparative example, the square root of the number of cycles until the capacity maintenance ratio SOH becomes 80% was 18, whereas in the power storage module 10 of the present invention, the square root of 25 or more. there were. Therefore, in the electrical storage module 10 of this invention, compared with the electrical storage module of the comparative example, it was confirmed that it can suppress that capacity | capacitance maintenance factor SOH falls with the increase in the number of cycles.

  Moreover, in the electrical storage module 10, the binding force can be changed by adjusting the tension of each piano wire 25, and the secondary battery group 12 can be simply and suitably fixed. Moreover, since the piano wire 25 is excellent in tensile strength, the wire diameter can be reduced while increasing the binding force. For this reason, when the electrical storage module 10 is accommodated in the battery accommodating portion as described above, it is possible to suppress the obstruction of the flow of the heat medium as compared with the configuration in which the secondary battery group 12 is restrained by the belt-shaped member.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) When the ratio of the amount of change in the capacity retention rate SOH to the amount of change in the number of charge and discharge cycles in the secondary battery group 12 is equal to or greater than a predetermined threshold, the binding force of the secondary battery group 12 increases. Is done. For this reason, due to the binding force applied to each secondary battery 11, the metal foil and the active material layer are brought into close contact with each other, and the sudden decrease in capacity maintenance rate SOH caused by the separation of the active material layer from the metal foil of the electrode Can be suppressed. Therefore, it is possible to suppress a decrease in the capacity maintenance rate SOH as the number of cycles increases.

  (2) Since the binding force of the secondary battery group 12 is increased to 1.2 times or more of the binding force before the determination result of step S1 in the binding force changing process becomes affirmative, the metal foil, the active material layer, In addition, the electrolyte can be prevented from being depleted in the active material layer due to an excessive binding force.

  (3) The restraining force of the secondary battery group 12 is a restraining force determined in advance lower than the restraining force (second range) when the determination result in step S1 in the restraining force changing process is not affirmative. 1st range). For this reason, it is possible to suppress a relatively gradual decrease in the capacity maintenance rate SOH accompanying the depletion of the electrolyte, and to further suppress a decrease in the capacity maintenance rate SOH of the secondary battery group 12.

(4) As the power storage module 10 including the secondary battery group 12, the capacity maintenance rate SOH can be prevented from decreasing as the number of cycles increases.
(5) Since the binding force of the secondary battery group 12 is changed based on the capacity maintenance rate SOH, the capacity maintenance rate SOH is compared with, for example, a configuration in which the binding force is changed based on the current value I or the voltage value V. It is possible to change the restraining force in conjunction with the decrease in the capacity, and more reliably suppress the decrease in the capacity maintenance rate SOH.

  (6) Among the metal wires, the piano wire 25 having particularly excellent tensile strength is used. Therefore, each secondary battery 11 can be more reliably fixed by setting the tension of the piano wire 25 to a high tension. Moreover, it can suppress that the flow of a heat exchange medium (heat medium) is prevented compared with the structure which provides a strip | belt-shaped member.

  (7) Since the piano wire 25 is arranged on the terminal forming surface 11a from which the positive electrode terminal 15 and the negative electrode terminal 16 of each secondary battery 11 protrude, the piano wire 25 is arranged on a surface different from the terminal forming surface 11a. Compared with the configuration, the portion protruding from the power storage module 10 can be reduced, and the power storage module 10 can be downsized.

The embodiment is not limited to the above, and may be embodied as follows, for example.
In the binding force changing process, the control unit 45 may perform only the processes in steps S4 and S5 after making an affirmative determination in step S1. According to this, when the capacity maintenance rate SOH recovers by exceeding 5% as the restraining force increases, it is possible to prevent the restraining force from being suppressed by the processes of steps S2 and S3.

  The second range (lower limit value and upper limit value) of the binding force may be appropriately changed as long as it is a binding force that exceeds one time the first range (lower limit value and upper limit value). However, from the viewpoint of suppressing the decrease in the capacity retention rate SOH, it is preferable to configure as in the above embodiment.

  In step S1 of the binding force change process, the control unit 45 may make a determination based on the amount of change in the capacity maintenance rate SOH per cycle number. That is, it may be determined whether or not the ratio of the change amount of the capacity maintenance rate SOH to the change amount of the cycle number is equal to or greater than a predetermined threshold value. Further, the threshold value may be changed.

  In step S <b> 1 of the binding force change process, the control unit 45 changes the capacity maintenance rate SOH detected for a part of the secondary batteries 11 that are one or more of the secondary batteries 11 constituting the secondary battery group 12. The determination may be made based on the amount.

  In step S1 of the binding force change process, the control unit 45 stores in advance in the storage device the amount of change in the capacity maintenance rate SOH calculated in association with the accumulated charge amount or accumulated discharge amount in the secondary battery group 12. The determination may be made based on the amount of change in the capacity maintenance rate SOH with respect to the accumulated charge amount or accumulated discharge amount that is a predetermined amount less than the current time.

○ In steps S2 and S4 of the binding force changing process, it may be determined whether or not it matches a predetermined threshold value.
○ The number of sets of the fixing portion 26 and the binding force changing mechanism 40 (the number of piano wires 25) may be changed. Further, the piano wire 25 may be provided on a surface different from the terminal formation surface 11 a of each secondary battery 11, or may not be in contact with the terminal formation surface 11 a of each secondary battery 11.

  The restraint force changing mechanism 40 may appropriately change its configuration as long as the tension of the piano wire 25 can be adjusted by winding each piano wire 25. Further, the restraint force changing mechanism 40 applies a voltage to, for example, a piezoelectric element disposed between the wall portion fixed to the support base 21 and the second holding member 24 to expand and contract the piezoelectric element. Therefore, the configuration may be such that the binding force of the secondary battery group 12 is changed. That is, if the binding force of the secondary battery group 12 can be changed, the configuration of the binding force changing mechanism 40 can be changed as appropriate.

  The tension measuring device 30 may be a different type of tension measuring device. For example, the tension measuring device 30 may be a load measuring device that detects a load (tension) applied from the piano wire 25 and outputs a detection signal corresponding to the load. Alternatively, the tension measuring device 30 may output a detection signal corresponding to the vibration generated in the piano wire 25 due to a change in voltage generated in the piezoelectric element after the vibration is applied, instead of the microphone.

In the secondary battery group 12, a spacer may be provided between the secondary batteries 11.
The shape of each fixing portion 26 may be appropriately changed as long as the piano wire 25 can be fixed.
As long as it can fix to the fixing | fixed part 26 and the restraint force change mechanism 40, each piano wire 25 may not be provided with the spherical member 25a.

The respective holding force changing mechanisms 40 may be provided on the first holding member 23, and the fixing portions 26 may be provided on the second holding member 24.
If the secondary battery group 12 can be configured in parallel, the shape of each secondary battery 11 (case 14) may be changed.

The electrode assembly 13 may be a wound electrode assembly in which a belt-like positive electrode and a negative electrode are wound with a belt-like separator 20 interposed therebetween.
The power storage module 10 may be a power storage module having a power storage device group in which power storage devices such as a nickel hydride secondary battery and an electric double layer capacitor are arranged in parallel.

O You may actualize in the electrical storage module 10 used other than a vehicle.
Hereinafter, a technical idea that can be grasped from the above embodiment will be additionally described.
(A) The restraining device is a metal that connects the holding members disposed at both ends of the power storage device group in the juxtaposed direction and holds the power storage device group to the holding member by tension. 5. The power storage module according to claim 1, wherein the restraint force changing mechanism changes the restraint force by adjusting a tension of the metal wire.

  (B) The power storage module according to the technical idea (i), wherein the metal wire is a piano wire.

  D1 ... Parallel arrangement direction, 10 ... Power storage module, 11 ... Lithium ion secondary battery (secondary battery, power storage device), 12 ... Secondary battery group (power storage device group), 13 ... Electrode assembly, 14 ... Case, 23 ... 1st holding member (holding member), 24 ... 2nd holding member (holding member), 25 ... Piano wire (metal wire), 40 ... Restraint force change mechanism, 41 ... Restraint device, 45 ... Control part (capacity maintenance rate) Detection means, determination means, restraint force control means).

Claims (4)

A power storage device group in which a plurality of power storage devices in which an electrode assembly in which an electrode having an active material layer provided on the surface of a metal foil is layered is accommodated in a case is arranged in parallel, and is constrained in the parallel direction to the power storage device group A power storage module comprising: a restraining device that applies force; and a restraining force changing mechanism that changes the restraining force of the restraining device,
Capacity maintenance rate detection means for detecting a capacity maintenance rate of the power storage device;
The ratio of the amount of change in the capacity maintenance rate to the amount of change in the number of cycles of charging and discharging in the power storage device, or the capacity maintenance rate for any one of the cumulative charge amount in the power storage device and the cumulative discharge amount in the power storage device Determining means for determining whether or not the amount of change is equal to or greater than a predetermined threshold;
A power storage module comprising: a restraint force control means for controlling the restraint force changing mechanism to increase the restraint force on condition that the determination means makes an affirmative determination.   2. The power storage module according to claim 1, wherein the binding force control unit increases the binding force to 1.2 times or more and 1.7 times or less of a binding force before the determination unit makes an affirmative determination.   The power storage module according to claim 1 or 2, wherein the restraining force control means maintains the restraining force at a predetermined restraining force when the determination means does not make an affirmative determination.   The power storage module according to claim 1, wherein the power storage device is a secondary battery.