Power storage module and method for manufacturing the same

Abstract

To suppress occurrence of a variation in high rate resistances between a plurality of power storage devices included in a power storage module.SOLUTION: A power storage module 100 disclosed herein includes a plurality of sub modules 10A-10E. The plurality of sub modules 10A-10E each include: a device group 20 in which a plurality of flat square power storage devices 1 are arranged; and a restraint member 30 restraining the device group 20. Each device group 20 is built by a plurality of power storage devices 1 having an approximated amount of surplus electrolytic solution. In each restraint member 30, a restraint pressure to the device group 20 to be restrained is set based on a temperature T during charging / discharging of the device group 20 to be restrained and an amount of reference surplus liquid RS of the device group 20 to be restrained.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed herein relates to a power storage module and a method for manufacturing the power storage module.

Background Art

[0002] Conventionally, for power sources for vehicle driving and the like, power storage devices such as lithium ion secondary batteries have been used. This power storage device is constructed, for example, by housing an electrode body and an electrolytic solution inside a battery case. At this time, most of the electrolytic solution has penetrated inside the electrode body. In addition, this type of power storage device may be used in the form of a power storage module (battery pack) in which a plurality of power storage devices are electrically connected. As conventional technical documents related to this, Patent Documents 1 to 4 can be cited.

[0003] For example, Patent Document 1 discloses a power storage module having a plurality of sub-modules and a housing that houses the plurality of sub-modules at predetermined positions. In Patent Document 1, each of the plurality of sub-modules includes a device group (cell group) in which a plurality of power storage devices (single cells) are arranged, and a restraining member that applies a restraining pressure in the arrangement direction to restrain the device group. And, there is a region in the housing that is likely to become relatively low in temperature, and the sub-module arranged in the region that is likely to become low in temperature is configured such that the restraining pressure of the restraining member is relatively lower than that of other sub-modules. Patent Document 1 describes that by reducing the restraining pressure in the sub-module in the region (low temperature region) where the high rate resistance is likely to decrease in this way, the high rate resistance (increase in resistance when high rate charge and discharge are repeated) of the plurality of power storage devices included in the power storage module can be equalized.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] However, in the power storage module described in Patent Document 1 above, variations in high-rate tolerance may occur among a plurality of power storage devices included in one device group. As a result of various studies by the inventor on such problems, it was confirmed that the amount of electrolyte solution (excess electrolyte solution) that does not penetrate into the electrode body affects the high-rate tolerance. From this, it was found that if there are variations in the amount of excess electrolyte solution among a plurality of power storage devices within one device group, variations in high-rate tolerance may occur within the device group even when an appropriate restraint pressure is applied in units of the device group. [Means for Solving the Problems]

[0006] In order to solve the above problems, a power storage module having the following configuration is provided by the technology disclosed herein.

[0007] The power storage module disclosed herein includes a plurality of sub-modules. Each of the plurality of sub-modules includes a device group in which a plurality of flat rectangular power storage devices are arranged such that the flat surfaces face each other between adjacent power storage devices, and a restraint member that restrains the device group along the arrangement direction of the power storage devices. Further, each of the device groups includes one reference device arbitrarily selected from a plurality of power storage devices included in the device group, and a reference excess liquid amount R that is the amount of excess electrolyte solution (hereinafter, also referred to as "excess electrolyte solution amount R") of the reference device S ​​​​​​​​When taking it as 100%, it is provided with other power storage devices in which the liquid volume of the surplus electrolytic solution is within the range of 90% to 110%. And each of the restraint members is based on the temperature T during charge and discharge of the device group to be restrained and the reference surplus liquid volume R of the reference device of the device group to be restrained S Based on this, the restraint pressure on the device group to be restrained is set.

[0008] The method for manufacturing a power storage module disclosed herein manufactures a power storage module including a plurality of sub-modules. Each of the plurality of sub-modules includes a device group in which a plurality of flat rectangular power storage devices are arranged such that flat surfaces face each other between adjacent power storage devices, and a restraint member that restrains the device group along the arrangement direction of the power storage devices. And the method for manufacturing this power storage module includes a temperature distribution prediction step of predicting the temperature distribution in the power storage module when a plurality of power storage devices are charged and discharged, and the reference surplus liquid volume R which is the surplus electrolytic solution volume of an arbitrarily selected reference device S When taking it as 100%, a preparation step of preparing a plurality of device groups in which the surplus electrolytic solution volume of other power storage devices is within the range of 90% to 110%, the temperature T during charge and discharge of the device group to be restrained, and the reference surplus liquid volume R of the reference device of the device group to be restrained S And a restraint step of restraining each of the said device groups with a restraint pressure based on this.

[0009] In the technology disclosed herein, when constructing each of a plurality of device groups, one reference device is selected, and the surplus electrolytic solution volume R of the reference device is regarded as the "reference surplus liquid volume R S ". And the surplus electrolytic solution volume R of other power storage devices included in this device group is controlled within the range of 90% to 110% of the reference surplus liquid volume R S . As a result, since a device group can be constructed with a plurality of power storage devices having approximate surplus electrolytic solution volumes R, variations in high-rate resistance within the device group can be suppressed. In addition, in the technology disclosed herein, not only the temperature T during charge and discharge, but also the reference surplus liquid volume R of the reference device SA confinement pressure taking this into account is set. As a result, a more appropriate confinement pressure can be applied to each device group, so that the high-rate tolerance of the power storage module can be more appropriately leveled.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, a power storage module according to an embodiment of the technology disclosed herein will be described. In the following description, members and parts having the same function in the drawings are denoted by the same reference numerals. Note that the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. Also, matters other than those specifically mentioned in this specification and matters necessary for implementing the technology disclosed herein (for example, the configuration and manufacturing method of the electrode body and the electrolytic solution) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field.

[0012] In addition, the "power storage device" as used in this specification is a concept that includes a device in which a charge carrier moves between a pair of electrodes (a positive electrode and a negative electrode) through an electrolytic solution to cause a charge and discharge reaction. That is, the power storage device in the technology disclosed herein includes secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and capacitors such as lithium-ion capacitors and electric double-layer capacitors.

[0013] <First Embodiment> FIG. 1 is a plan view schematically showing a power storage module according to this embodiment. FIG. 2 is a side view schematically showing the power storage module according to this embodiment. FIG. 3 is a perspective view schematically showing a power storage device in this embodiment. FIG. 4 is a cross-sectional view schematically showing the power storage device in this embodiment. In the following description, the reference signs L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, upper, and lower, respectively. Also, the reference signs X, Y, and Z in the drawings represent the short side direction, long side direction, and vertical direction of the power storage device, respectively. The short side direction X is also the arrangement direction of the power storage devices. However, these are merely directions for convenience of explanation and do not limit the installation form of the power storage module in any way. Hereinafter, the power storage module 100 according to this embodiment will be described with reference to FIGS. 1 to 4.

[0014] 1. Sub-module As shown in FIGS. 1 and 2, the power storage module 100 according to this embodiment has a plurality (five in the figure) of sub-modules 10A to 10E. The number of sub-modules included in the power storage module is not particularly limited and can be appropriately increased or decreased in consideration of the target performance. As an example, the number of sub-modules is about 2 to 15. As will be described in detail later, the power storage module disclosed herein is configured such that the restraint pressure on the power storage device can be individually set in sub-module units. For this reason, as the number of sub-modules (the number of divisions of the power storage module) with respect to the total number of power storage devices increases, it becomes easier to equalize the high-rate tolerance of the entire power storage module.

[0015] Each of the plurality of sub-modules 10A to 10E includes a device group 20 and a restraint member 30. Hereinafter, each of the device group 20 and the restraint member 30 will be described.

[0016] (1) Device group The device group 20 is constructed by arranging a plurality of flat rectangular power storage devices 1 such that the flat surfaces 1a face each other between adjacent power storage devices 1. As shown in FIGS. 1 and 2, in this embodiment, one device group 20 is constructed by arranging five power storage devices 1. However, the number of power storage devices 1 included in one device group 20 is not particularly limited and can be appropriately increased or decreased in consideration of the intended performance. For example, the number of power storage devices 1 included in one device group 20 may be about 20 to 30. Furthermore, the number of power storage devices 1 included in each device group 20 may be the same or different between the respective device groups 20.

[0017] Also, as shown in FIGS. 3 and 4, each of the power storage devices 1 included in the device group 20 includes a battery case 2, an electrode body 3, and an electrolytic solution 4.

[0018] The battery case 2 is a container that houses the electrode body 3 and the electrolytic solution 4. For the battery case 2, a material having a predetermined rigidity (for example, aluminum steel, etc.) can be used, for example. Also, a positive electrode terminal 2a and a negative electrode terminal 2b are provided on the upper surface of the battery case 2. As shown in FIG. 4, the positive electrode terminal 2a and the negative electrode terminal 2b are conductive members that extend to the inside of the battery case 2. And the positive electrode terminal 2a is electrically connected to the positive electrode (not shown) of the electrode body 3. Also, the negative electrode terminal 2b is electrically connected to the negative electrode (not shown) of the electrode body 3. Also, although not shown in FIGS. 1 and 2, in the power storage module 100 according to this embodiment, the positive electrode terminals 2a and the negative electrode terminals 2b of two adjacent power storage devices 1 are electrically connected by a connection member (such as a bus bar). Thereby, a plurality of power storage devices 1 included in the power storage module 100 can be electrically connected in series.

[0019] The electrode body 3 is a power generation element of the energy storage device 1. The electrode body 3 is configured by opposing a positive electrode and a negative electrode via a separator. As an example of the specific structure of the electrode body 3, a wound electrode body, a laminated electrode body, etc. can be mentioned. The wound electrode body forms a long laminate by laminating a long strip-shaped separator, a long strip-shaped positive electrode, and a long strip-shaped negative electrode, and is formed by winding the long laminate in the longitudinal direction. Further, the laminated electrode body is formed by laminating a plurality of short sheet-shaped separators, short sheet-shaped positive electrodes, and short sheet-shaped negative electrodes. Note that the detailed materials of each member (positive electrode, negative electrode, separator, etc.) constituting the electrode body 3 can be adopted from conventionally known materials without particular limitation, and since the technology disclosed herein is not limited, detailed description is omitted.

[0020] The electrolytic solution 4 is a liquid material that has penetrated inside the electrode body 3. In other words, the electrolytic solution 4 is interposed between the positive electrode and the negative electrode of the electrode body 3. And in this energy storage device 1, charge carriers move between the positive electrode and the negative electrode through the electrolytic solution 4, thereby performing charge and discharge. Note that the components of the electrolytic solution 4 can be adopted from conventionally known components without particular limitation, and since the technology disclosed herein is not limited, detailed description is omitted.

[0021] Note that if poor penetration of the electrolytic solution 4 into the electrode body 3 occurs, an appropriate charge and discharge reaction may not occur. For this reason, in a general energy storage device 1, more electrolytic solution 4 than the volume of the internal space of the electrode body 3 is injected into the battery case 2. As a result, inside the energy storage device 1, an electrolytic solution 4 (excess electrolytic solution 4a) that does not penetrate into the electrode body 3 is generated. As shown in FIG. 4, this excess electrolytic solution 4a exists around the electrode body 3 (typically, between the battery case 2 and the electrode body 3).

[0022] (2) Restraining member Next, the restraint member 30 will be described. As shown in FIGS. 1 and 2, the restraint member 30 is a member that restrains the device group 20 along the arrangement direction of the power storage devices 1 (the short side direction X of the power storage devices 1). With this restraint member 30, it is possible to prevent displacement from occurring in each power storage device 1. The restraint member 30 in the present embodiment includes a restraint band 32 and a restraint plate 34. The restraint band 32 is a belt-like member that clamps and restrains a plurality of power storage devices 1. Further, the restraint plate 34 is a pair of plate-like members arranged so as to sandwich one device group 20. By arranging the device group 20 between the pair of restraint plates 34 and tightening the restraint band 32, a uniform restraint pressure can be applied to the device group 20 (a plurality of power storage devices 1).

[0023] Also, the power storage module 100 according to the present embodiment includes a restraint pressure change mechanism that individually changes the restraint pressure of the restraint members 30 of the plurality of sub-modules 10A to 10E. Thereby, the restraint pressure applied to each device group 20 of the sub-modules 10A to 10E can be individually changed. As an example of this restraint pressure change mechanism, there is a worm gear 36 as shown in FIG. 2. The worm gear 36 includes a worm 36a attached so as to span both ends of the restraint band 32, and a worm wheel 36b that is a gear fitted to the worm 36a. In such a restraint pressure change mechanism, by rotating the worm wheel 36b, the worm 36a can be advanced and retracted along the arrangement direction X, and the tightening pressure of the restraint band 32 (the restraint pressure applied to the device group 20) can be changed.

[0024] 2. Cooling Device Note that the power storage module 100 according to the present embodiment includes a cooling device 50. The cooling device 50 shown in FIG. 1 includes an intake port 51, an exhaust port 52, an air-cooling fan 53, and a cooling control device 54.

[0025] The intake port 51 is provided on one side (front F side) in the arrangement direction X of the power storage device 1. An air-cooling fan 53 is attached to the intake port 51. The air-cooling fan 53 is configured to send wind (air) from the outside to the inside of the power storage module 100 through the intake port 51. The configuration of the air-cooling fan 53 is not limited, but for example, it includes an electric motor (not shown). Next, the cooling control device 54 is connected to the electric motor of the air-cooling fan 53. Predetermined first temperature and a second temperature lower than the first temperature are set in the cooling control device 54. Then, when the temperature inside the power storage module 100 becomes equal to or higher than the first temperature, the cooling control device 54 operates the air-cooling fan 53. Thereby, low-temperature air is supplied into the power storage module 100 through the intake port 51. The temperature inside the power storage module 100 can be measured by a temperature sensor 60 described later.

[0026] And on the other side (rear Rr side) in the arrangement direction X of the power storage module 100, an exhaust port 52 is provided. The air supplied from the intake port 51 passes through the inside of the power storage module 100 while cooling the power storage device 1, and then is discharged from the exhaust port 52. Then, when the temperature inside the power storage module 100 falls below the second temperature by the above-described cooling operation, the cooling control device 54 stops the air-cooling fan 53. Thereby, it is possible to prevent the power storage device 1 from being cooled more than necessary.

[0027] Note that the above-described cooling device 50 is an air-cooling type cooling device that uses air as a refrigerant. However, the configuration of the cooling device is not particularly limited. For example, the cooling device may be a liquid-cooling type cooling device that uses a liquid as a refrigerant. However, from the viewpoint of reducing the cost required for the cooling operation of the power storage device 1, the air-cooling type cooling device 50 as in the present embodiment is preferable. Further, the power storage module 100 according to the present embodiment may include a housing that houses the sub-modules 10A to 10E. And in the power storage module 100 provided with such a housing, it is particularly preferable to provide the cooling device having the above-described configuration. Thereby, it is possible to suppress a large increase in the temperature inside the housing due to heat generation accompanying charging and discharging of the power storage device 1.

[0028] 3. Configuration related to control of high-rate tolerance By the way, in the power storage module 100 with the above configuration, a deviation in temperature distribution is likely to occur during charge and discharge. Specifically, when the power storage device 1 generates heat during charge and discharge, adjacent power storage devices 1 heat each other. As a result, in the central part in the array direction X, a chain reaction of heat generation occurs between the power storage devices 1, so that the temperature T during charge and discharge is likely to become a relatively high temperature region. On the other hand, both end portions in the array direction X (the front F portion and the rear Rr portion in FIG. 1) have higher heat dissipation than the central portion, so that the temperature T during charge and discharge is likely to become a relatively low temperature region. In particular, in the power storage module 100 having the cooling device 50, the temperature T at both end portions in the array direction X close to the intake port 51 and the exhaust port 52 is particularly likely to decrease. And when such a deviation in temperature distribution occurs, variations in high-rate tolerance occur among the plurality of power storage devices 1 included in the power storage module 100. Specifically, in the low temperature region, the high-rate tolerance of the power storage device 1 is likely to be relatively low. On the other hand, in the high temperature region, the high-rate tolerance of the power storage device 1 is likely to be relatively high.

[0029] Also, in the power storage module 100 with the above configuration, variations in high-rate tolerance may occur in each power storage device 1 depending on the liquid volume of the excess electrolyte 4a (excess electrolyte volume R). Specifically, in the electrode body 3 of a general power storage device 1, expansion and contraction of the negative electrode occur during high-rate charge and discharge. And when the negative electrode expands, the electrolyte 4 is discharged from the inside of the electrode body 3 to the outside. On the other hand, when the negative electrode contracts, the excess electrolyte 4a penetrates into the electrode body 3. Here, the electrolyte 4 that has penetrated into the electrode body 3 contains charge carriers released from the positive electrode. For this reason, in the power storage device 1 with a large excess electrolyte volume R, when the electrolyte 4 is discharged to the outside of the electrode body 3, the concentration of the charge carriers in the electrolyte 4 decreases significantly. And when the negative electrode contracts, the excess electrolyte 4a with a low concentration of charge carriers penetrates into the electrode body 3. As described above, the power storage device 1 containing a large amount of the excess electrolyte 4a has a tendency for the high-rate tolerance to be low because there may be a shortage of charge carriers inside the electrode body 3 during high-rate charge and discharge and the battery resistance may increase significantly.

[0030] And, when variations occur in the high-rate tolerance of the plurality of power storage devices 1 due to any of the above-described causes, it becomes difficult to perform charge and discharge control in consideration of the high-rate tolerance. Specifically, if the charge and discharge of the entire power storage module 100 are controlled based on the power storage device 1 with high high-rate tolerance, the deterioration of the power storage device 1 with low high-rate tolerance may progress rapidly. For this reason, when constructing the power storage module 100 with a plurality of power storage devices 1 having variations in high-rate tolerance, it becomes necessary to use the power storage device 1 with low high-rate tolerance as a reference. However, if the power storage device 1 with low high-rate tolerance is used as a reference, the power storage device 1 with high high-rate tolerance cannot be fully utilized. In order to suppress such variations in high-rate tolerance, the power storage module 100 according to the present embodiment is configured as follows.

[0031] First, each of the device groups 20 in the present embodiment is constructed by a plurality of power storage devices 1 with approximate surplus electrolyte amounts R. Here, "the surplus electrolyte amounts (surplus electrolyte amounts R) in the device group are approximate" in this specification means that when the surplus electrolyte amount R (reference surplus amount R S ) of arbitrarily selected one power storage device (reference device 1X) is taken as 100%, the surplus electrolyte amount R of the other power storage devices 1Y is within the range of 90% to 110% (preferably 95% to 105%, more preferably 98% to 102%). In this way, when constructing one device group 20 with power storage devices 1 having approximate surplus electrolyte amounts R, it is possible to suppress the occurrence of variations in high-rate tolerance within one device group 20.

[0032] Next, each of the restraining members 30 in the present embodiment has the temperature T during charge and discharge of the device group 20 to be restrained and the reference surplus amount R of the device group 20 to be restrained SBased on this, the restraint pressure on the device group 20 to be restrained is set. As described above, as causes of variations in high-rate tolerance, the temperature T during charge and discharge and the excess electrolyte amount R are cited. In the present embodiment, the restraint pressure considering these causes is individually applied to each of the plurality of device groups 20. Thereby, variations in high-rate tolerance among each of the sub-modules 10A to 10E (device group 20) can be suppressed.

[0033] As described above, in the present embodiment, the restraint pressure on each device group 20 is set based on the temperature T during charge and discharge and the reference excess liquid amount R. S Thereby, it is possible to suppress variations in high-rate tolerance among the plurality of device groups 20. Further, in the present embodiment, each device group 20 is constructed of a plurality of power storage devices 1 with approximate excess electrolyte amounts R. Thereby, variations in high-rate tolerance within one device group 20 can be suppressed. As a result, according to the present embodiment, the high-rate tolerance in the entire power storage module 100 can be suitably leveled.

[0034] Note that, as described above, the power storage device 1 arranged in the low-temperature region tends to have relatively low high-rate tolerance. On the other hand, when the restraint pressure by the restraint member 30 is decreased, the high-rate tolerance in the device group 20 restrained by the restraint member 30 tends to improve. For this reason, it is preferable that each of the restraint members 30 lowers the restraint pressure on the device group 20 in the low-temperature region where the temperature T during charge and discharge is relatively low, and raises the restraint pressure on the device group 20 in the high-temperature region where the temperature T during charge and discharge is relatively high. Thereby, variations in high-rate tolerance caused by the temperature T during charge and discharge can be reduced.

[0035] In addition, a power storage device 1 with a large excess electrolyte amount R also tends to have relatively low high-rate tolerance. For this reason, the restraint pressure on the device group 20 with a relatively large reference excess liquid amount R of the reference device 1X is lowered, and the reference excess liquid amount R S is relatively large, and the restraint pressure on the device group 20 is lowered, and the reference excess liquid amount R SIt is preferable to increase the restraint pressure on the device group 20 with a relatively small amount. This can reduce the variation in high-rate tolerance caused by the excess electrolyte amount R.

[0036] Also, the device group 20 with a relatively low temperature T during charge and discharge is preferably constructed with the power storage device 1 having a relatively small excess electrolyte amount R. Further, the device group 20 with a relatively high temperature T during charge and discharge is preferably constructed with the power storage device 1 having a relatively large excess electrolyte amount R. This can cancel out the variation in high-rate tolerance caused by the temperature T during charge and discharge and the variation in high-rate tolerance caused by the excess electrolyte amount R, so that it is easier to equalize the high-rate tolerance of the entire power storage module 100.

[0037] Note that the reference excess liquid amount R of each of the plurality of device groups 20 S may be different or the same. As described above, in the power storage module 100 according to the present embodiment, for each of the plurality of device groups 20, the restraint pressure is set individually based on the temperature T and the reference excess liquid amount R S during charge and discharge. Therefore, even if there is a variation in the reference excess liquid amount R in units of the device group 20 S , an appropriate restraint pressure corresponding to the variation in the reference excess liquid amount R S can be applied to each device group 20. However, the reference excess liquid amount R of each of the plurality of device groups 20 S is preferably approximated to a certain extent. For example, when the reference excess liquid amount R of arbitrarily selected one device group 20 S is set to 100%, the reference excess liquid amount R of the other device groups 20 S is preferably in the range of 50% to 150% (more preferably 70% to 130%, particularly preferably 80% to 120%). This can reduce the variation in high-rate tolerance caused by the excess electrolyte amount R, so that it is easier to equalize the high-rate tolerance of the entire power storage module 100.

[0038] 4. Control mechanism of the restraint member Note that the power storage module 100 according to this embodiment is configured to be able to immediately adjust the restraint pressure in accordance with fluctuations in the temperature distribution during charge and discharge. Specifically, this power storage module 100 includes a temperature sensor 60 that measures the temperature T during charge and discharge within the power storage module, and a control unit 70 that controls the restraint pressure of each restraint member 30.

[0039] For the temperature sensor 60, sensors that can be used for this type of temperature measurement can be used without particular limitation. As an example of this temperature sensor 60, a thermocouple, a thermistor, or the like is used. In this embodiment, the temperature sensor 60 is installed by predicting the temperature distribution during charge and discharge. As described above, in the power storage module 100 according to this embodiment, the central portion in the arrangement direction X where the chain-like heat generation of the power storage device 1 can occur tends to become high temperature. On the other hand, both ends in the arrangement direction X close to the cooling device 50 tend to become low temperature. Therefore, the temperature sensors 60 in this embodiment are attached to the most upstream sub-module 10A, the central sub-module 10C, and the most downstream sub-module 10E. And each temperature sensor 60 transmits the measured temperatures of the sub-modules 10A, 10C, 10E to the control unit.

[0040] The control unit 70 typically includes a ROM (Read Only Memory) that stores a program for performing restraint pressure control, a CPU (Central Processing Unit) that can execute the program, and a RAM (random access memory) that temporarily stores data. Further, the control unit includes an input port to which the measurement result of the temperature sensor 60 is input, and an output port that outputs a drive signal to the restraint members 30 (worm gears 36) of each sub-module 10A to 10E.

[0041] And the control unit 70 in this embodiment includes a pressure calculation unit 72, a liquid volume storage unit 74, and a correction unit 76. The measurement result of the temperature sensor 60 is input to the pressure calculation unit 72 via the input port. Then, the pressure calculation unit 72 individually calculates the restraint pressure of the restraint member 30 of each sub-module 10A to 10E based on the measurement result of the temperature sensor 60. Next, the reference surplus liquid volume R S of each of the plurality of device groups 20 is stored in the liquid volume storage unit 74. The reference surplus liquid volume R S stored in this liquid volume storage unit 74 is information based on, for example, the manufacturing history of the power storage device 1. And the correction unit 76 corrects the restraint pressure calculated by the pressure calculation unit 72 based on the reference surplus liquid volume R S . Then, the control unit 70 transmits the corrected restraint pressure to the restraint member 30 (worm gear 36). Thereby, an appropriate restraint pressure considering both the temperature T during charge and discharge and the reference surplus liquid volume R S can be applied to each device group 20.

[0042] Further, the control unit 70 may include a temperature distribution storage unit 78 in which distribution information indicating the tendency of the temperature distribution of the power storage module 100 is recorded. In this case, the control unit 70 calculates the temperature T during charge and discharge of each of the sub-modules 10A to 10E based on the measurement result of the temperature sensor 60 and the distribution information. In this way, by using the pre-recorded distribution information, even if the number of temperature sensors 60 is reduced, the temperature T during charge and discharge of each of the sub-modules 10A to 10E can be accurately calculated. As a result, the number of components can be reduced and the manufacturing cost can be reduced. Note that the distribution information to be recorded in the temperature distribution storage unit 78 can be obtained in advance by preliminary experiments or the like. For example, in this preliminary experiment, it is preferable to attach a temperature sensor to each sub-module and obtain the detailed temperature distribution when charging and discharging. Thereby, more accurate distribution information can be obtained.

[0043] <Other Embodiments> The above describes one embodiment (the first embodiment) of the power storage module disclosed herein. However, the above-described first embodiment is not intended to limit the technology disclosed herein, and various modifications can be made. Hereinafter, other embodiments of the technology disclosed herein will be described.

[0044] 1. Regarding the temperature distribution In the first embodiment, the control unit 70 includes a temperature distribution storage unit 78, and calculates the temperature T during charging and discharging of each of the sub-modules 10A to 10E based on the measurement results of the temperature sensors 60 and the distribution information. However, even when the distribution information is not recorded, the restraint pressure of each sub-module can be appropriately adjusted. For example, by increasing the number of temperature sensors, the temperature distribution of the power storage module can be accurately grasped even when the distribution information has not been recorded in advance.

[0045] In addition, in the power storage module 100 according to the first embodiment, a temperature distribution occurs in which the central portion in the array direction X becomes a high-temperature region and both end portions in the array direction X become low-temperature regions. However, this temperature distribution is an example of the temperature distribution of the power storage module and is not intended to limit the technology disclosed herein. Specifically, the temperature distribution of the power storage module varies depending on various conditions such as the number of power storage devices, charging and discharging conditions, and the configuration of the cooling device. For example, when an air intake of the cooling device is provided near the center in the array direction, a low-temperature region may occur in the central portion in the array direction. Therefore, when implementing the technology disclosed herein, it is preferable to conduct preliminary experiments or the like to investigate the temperature distribution of the power storage module in advance.

[0046] 2. Regarding the restraint member As described above, in the first embodiment, the restraint member 30 including the restraint band 32 is used. However, the structure of the restraint member does not limit the technology disclosed herein, and various structures can be adopted.

[0047] As another example of the restraining member, there is a frame body 38 as shown in FIG. 5. Since the power storage device 1 tends to expand during charging and discharging, when charging and discharging are performed with a plurality of power storage devices 1 accommodated in the accommodating portion 38a of the frame body 38, a restraining pressure along the arrangement direction X is generated due to the expansion of the power storage device 1. When using this frame body 38 as a restraining member, it is preferable to vary the width W of the accommodating portion 38a of the frame body 38 for each sub-module. Specifically, when using a frame body 38 with a small width W of the accommodating portion 38a, the restraining pressure applied to each power storage device 1 increases. On the other hand, when using a frame body 38 with a large width W of the accommodating portion 38a, the restraining pressure applied to each power storage device 1 decreases. Therefore, by adjusting the width W of the accommodating portion 38a based on the temperature T and the reference surplus liquid amount R during charging and discharging S it is possible to suppress variations in high-rate tolerance among the plurality of device groups 20.

[0048] Also, as shown in FIG. 6, each of the plurality of sub-modules may include a buffer plate 39 that is restrained by a restraining member 30 together with the device group 20 (a plurality of power storage devices 1). According to such a configuration, the restraining pressure on the device group 20 can be controlled by adjusting the thickness t of the buffer plate 39. Specifically, when the thickness t of the buffer plate 39 is increased, the restraining pressure on the device group 20 tends to increase. On the other hand, when the thickness t of the buffer plate 39 is decreased, the restraining pressure on the device group 20 tends to decrease. Therefore, by adjusting the thickness t of the buffer plate 39 based on the temperature T and the reference surplus liquid amount R during charging and discharging S it is possible to suppress variations in high-rate tolerance among the plurality of device groups 20.

[0049] In the first embodiment, a worm gear 36 is used as the restraining pressure changing mechanism. However, the structure of the restraining pressure changing mechanism is not particularly limited as long as the restraining pressure can be individually adjusted for each sub-module. For example, instead of the worm gear, a driving device such as an actuator may be attached to the restraining band. Also, as shown in FIG. 6, when changing the restraining pressure by adjusting the thickness t of the buffer plate 39, the spring constant of the buffer plate 39 may be changed, or a piezo element that changes the thickness t of the buffer plate 39 may be used.

[0050] 3. Adjusting means for the restraint pressure (1) Manual adjustment Further, in the first embodiment, a control unit 70 for controlling the restraint pressure of each of the plurality of restraint members 30 is provided. However, the power storage module disclosed herein may not be provided with a control unit. For example, a structure in which a restraint pressure changing mechanism (such as a worm gear) can be manually operated, and a display means (such as an indicator) showing an appropriate restraint pressure based on the temperature T during charge and discharge and the reference surplus liquid amount R S If it is provided, the restraint pressure for each device group can be manually adjusted to an appropriate value. Even when adopting a structure for performing such manual restraint pressure adjustment, the high-rate resistance of the entire power storage module can be appropriately leveled.

[0051] (2) Adjustment of the restraint pressure in the manufacture of the power storage module Further, the power storage module 100 according to the first embodiment is configured to be able to adjust the restraint pressure of each restraint member 30 during charge and discharge. However, the technology disclosed herein is not limited to such a form. For example, when manufacturing the power storage module, the temperature T during use is predicted, and the restraint pressure may be set in advance based on the predicted temperature T and the reference surplus liquid amount R S That is, the technology disclosed herein includes a method for manufacturing a power storage module.

[0052] Specifically, as shown in FIG. 7, the method for manufacturing this power storage module includes a temperature distribution prediction step S10, a preparation step S20, a restraint step S30, and a module construction step S40. Hereinafter, with reference to the power storage module 100 having the structure shown in FIG. 8, the method for manufacturing the power storage module according to the present embodiment will be described. Note that the power storage module 100 shown in FIG. 8 has the same structure as the power storage module 100 shown in FIG. 1 except that it does not include a temperature sensor 60 and a control unit 70.

[0053] (a) Temperature distribution prediction step S10 In this step, the temperature distribution in the power storage module 100 when a plurality of power storage devices 1 are charged and discharged is predicted. In this temperature distribution prediction step S10, it is preferable to predict the temperature distribution in the power storage module 100 during charging and discharging by a preliminary experiment or a simulation using commercially available analysis software. For example, it is preferable to construct a preliminary test module simulating the power storage module 100 to be manufactured, measure the temperature distribution, and predict the temperature distribution in the power storage module 100 based on the results of this actual measurement.

[0054] (b) Preparation process S20 In this step, the reference excess electrolyte volume R, which is the excess electrolyte volume R of an arbitrarily selected reference device 1X, is S When the amount R of surplus electrolyte solution of the other power storage devices 1F is set to 100%, a plurality of device groups 20 are prepared in which the amount R of surplus electrolyte solution of the other power storage devices 1F is within a range of 90% to 110%. This makes it possible to obtain a plurality of device groups 20 made up of a plurality of power storage devices 1 having similar amounts R of surplus electrolyte solution. Note that the preparation step S20 in this embodiment includes an surplus liquid amount acquisition step S22, an surplus liquid amount determination step S24, a grouping step S26, and a device group creation step S28. Each step will be described below.

[0055] (b-1) Excess liquid volume acquisition process S22 In the surplus liquid amount acquisition step S22, the surplus electrolyte amount R of each of the multiple electricity storage devices 1 to be used is acquired. In this step, it is only necessary to acquire the surplus electrolyte amount R, and the means for acquiring this is not particularly limited. For example, the surplus electrolyte amount R may be predicted based on the manufacturing history of the electricity storage device 1. Also, an X-ray transmission image of the electricity storage device 1 to be used may be acquired, and the surplus electrolyte amount R may be measured based on the X-ray transmission image.

[0056] (b-2) Excess liquid volume determination step S24 In the excess electrolyte amount determination step S24, it is determined whether the excess electrolyte amounts R of all the electricity storage devices 1 to be used are similar to each other. Specifically, in this step, first, the average value R of the excess electrolyte amounts of all the electricity storage devices 1 to be used is calculated. Ave Then, calculate the average value of the excess electrolyte amount R AveWhen taking it as 100%, it is determined whether or not the surplus electrolyte amount R of all the power storage devices 1 exists within the range of 90% to 110%. And when the surplus electrolyte amount R of all the power storage devices 1 is within the range of 90% to 110% of the above average value R Ave (S24's YES), it can be said that the surplus electrolyte amounts R are approximated (there is no variation) in all the power storage devices 1 scheduled for use. In this case, the manufacturing process proceeds to the device group creation step S28. On the other hand, when the surplus electrolyte amount R of some of the power storage devices 1 is outside the range of 90% to 110% of the above average value R Ave (S24's NO), it can be said that there is a variation in the surplus electrolyte amount R among the plurality of power storage devices 1 scheduled for use. In this case, the manufacturing process proceeds to the grouping step S26.

[0057] (b-3) Grouping step S26 In this step, a group in which a plurality of power storage devices 1 with approximated surplus electrolyte amounts R are gathered is created. Specifically, first, one power storage device 1 is arbitrarily selected from among the plurality of power storage devices 1 scheduled for use and set as the reference device 1X. Next, when taking the surplus electrolyte amount R (reference surplus amount R S ) of this reference device 1X as 100%, other power storage devices 1Y with the surplus electrolyte amount R within the range of 90% to 110% are selected. Then, the reference device 1X and the other power storage devices 1Y are made into a group for forming one device group 20. Note that in this step, the same number of groups as the number of device groups 20 to be formed (5 in FIG. 8) are created.

[0058] (b-4) Device group creation step S28 In this process, storage devices 1 with approximated surplus electrolyte amounts R are arranged to form a device group 20. Here, when the grouping process S26 is performed as the previous process, the storage devices 1 in the same group created in advance are arranged. As a result, the device group 20 can be formed using a plurality of storage devices 1 with approximated surplus electrolyte amounts R. On the other hand, in the surplus liquid amount determination process S24, when it is determined that the surplus electrolyte amounts R of all the storage devices 1 scheduled to be used are approximated (YES in S24), a plurality of arbitrary storage devices 1 may be selected from all the storage devices 1 to form the device group 20.

[0059] (c) Restraining process S30 In this process, each of the created plurality of device groups 20 is restrained by a restraining member 30. As a result, sub-modules 10A to 10E including the device group 20 and the restraining member 30 are constructed. Here, in the manufacturing method according to the present embodiment, based on the temperature T during charge and discharge and the reference surplus liquid amount R S the restraining pressure for each of the plurality of device groups 20 is individually set. Since the procedure for setting this restraining pressure has already been described, duplicate explanations are omitted. When the restraining pressure is set in advance when manufacturing the power storage module 100 as in the present embodiment, it is preferable to perform a preliminary test for preliminarily investigating various factors that affect high-rate resistance. Examples of the measurement items in this preliminary test include the relationship between the temperature T during charge and discharge and high-rate resistance, and the relationship between the surplus electrolyte amount R and high-rate resistance.

[0060] (d) Module construction process S40 In this process, a plurality of sub-modules 10A to 10E are arranged along the arrangement direction X, and each storage device 1 is electrically connected by a connection member. As a result, a power storage module 100 including a plurality of sub-modules 10A to 10E is constructed. And the power storage module 100 constructed by the above procedure has a device group 20 constructed of storage devices 1 with approximated surplus electrolyte amounts R, so the variation in high-rate resistance within one device group 20 is suppressed. Furthermore, this power storage module 100 is based on the temperature T during charge and discharge and the reference surplus liquid amount RS Based on this, the restraint pressure on each device group 20 is preset. As a result, even when on-vehicle control during charge and discharge is not performed using a control unit or the like, variations in high-rate tolerance among the plurality of device groups 20 can be suppressed.

[0061] [Test Example] Hereinafter, test examples related to the technology disclosed herein will be described. Note that the following test examples are tests that obtained findings leading to the technology disclosed herein. That is, the technology disclosed herein is not naturally limited by the following test examples.

[0062] In this test example, a plurality of power storage devices with different amounts of excess electrolyte R were constructed, and the high-rate tolerance of each was confirmed. Specifically, first, power storage devices (lithium-ion secondary batteries, Examples 1 to 4) in which an electrode body and an electrolyte were housed inside a battery case were produced. And in this test example, the liquid volume of the electrolyte injected into the battery case was made different for each of Examples 1 to 4. And when each power storage device was checked 350 hours after the injection of the liquid, as shown in Table 1, the amount of excess electrolyte was different in each example. Note that the "amount of excess electrolyte" in Table 1 is the ratio with the amount of excess electrolyte in Example 1 (5 cc) taken as 100% (reference value). Also, the configuration (electrode body, etc.) excluding the amount of excess electrolyte R is common to all power storage devices.

[0063] Next, in a temperature environment of 25°C, the power storage device was adjusted to a state of SOC 50%, and a constant current discharge was performed at 150 A for 10 seconds, and the discharge resistance was measured. Next, the battery voltage drop ΔV that dropped in 10 seconds was read, and based on the battery voltage ΔV and the discharge current value (150 A), the IV resistance (initial resistance) was calculated. Then, in a temperature environment of 25°C, the power storage device was adjusted to a state of SOC 50%, and after constant current charging at a charging rate of 150 A for 10 seconds, it was paused for 5 seconds, and then after constant current discharge at a discharge rate of 10 A for 150 seconds, and then paused for 5 seconds, one charge-discharge cycle was defined as such, and this was repeated 1000 cycles to conduct a high-rate durability test. Then, after the high-rate durability test, the IV resistance was measured in the same way as the initial resistance, and the resistance increase rate was calculated from the ratio of the IV resistance after the durability test to the initial resistance (IV resistance after the durability test / initial resistance). The results are shown in Table 1. Note that Table 1 shows the relative values when the resistance increase rate of Example 1 is taken as 1.00 (reference).

[0064]

Table 1

[0065] As shown in Table 1, in Example 2 where the excess electrolyte amount was decreased from Example 1, a tendency for the high-rate tolerance to improve was confirmed. On the other hand, in Examples 3 and 4 where the excess electrolyte amount was increased from Example 1, a tendency for the high-rate tolerance to decrease was confirmed. From this, it was found that the high-rate tolerance of the power storage device is also affected by the excess electrolyte amount, so it is difficult to suppress the variation in high-rate tolerance only by adjusting the restraint pressure according to the temperature during charge and discharge. And this excess electrolyte amount is a factor that varies in one power storage device unit, different from the temperature distribution during charge and discharge. Therefore, in order to suppress the variation in high-rate tolerance caused by the excess electrolyte amount, it is understood that it is necessary to construct one device group with a plurality of power storage devices with approximate excess electrolyte amounts.

[0066] Although the technologies disclosed herein have been described in detail above, these are merely examples and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes of the specific examples exemplified above. That is, the technologies disclosed herein include the forms described in Items 1 to 5 below.

[0067] <Item 1> A power storage module including a plurality of sub-modules, Each of the plurality of sub-modules, A device group in which a plurality of flat rectangular power storage devices are arranged such that flat surfaces face each other between adjacent power storage devices, A restraining member that restrains the device group along the arrangement direction of the power storage devices and Each of the device groups, One reference device arbitrarily selected from a plurality of the power storage devices included in the device group, A reference surplus liquid amount R that is the amount of surplus electrolyte of the reference device S When taken as 100%, other power storage devices in which the amount of surplus electrolyte is in the range of 90% to 110% and Each of the restraining members has a restraining pressure set for the device group to be restrained based on the temperature T during charge and discharge of the device group to be restrained and the reference surplus liquid amount R of the reference device of the device group to be restrained S A power storage module.

[0068] <Item 2> Each of the restraining members reduces the restraining pressure on the device group with a relatively low temperature T during charge and discharge and increases the restraining pressure on the device group with a relatively high temperature T during charge and discharge. The power storage module according to Item 1.

[0069] <Item 3> Each of the restraining members reduces the restraining pressure on the device group with a relatively large reference surplus liquid amount R S and reduces the restraining pressure on the device group with a relatively large reference surplus liquid amount R SThe power storage module according to item 1 or 2, which increases the restraint pressure on the device group with relatively few devices.

[0070] <Item 4> A temperature sensor for measuring the temperature inside the power storage module, A control unit for controlling the restraint pressure of each of the plurality of restraint members and comprising The control unit is a pressure calculation unit that calculates the restraint pressure of each of the plurality of restraint members based on the measurement result of the temperature sensor, A liquid volume storage unit in which the reference surplus liquid volume R S of each of the plurality of device groups is stored, Based on the reference surplus liquid volume R S a correction unit that corrects the restraint pressure calculated by the pressure calculation unit The power storage module according to any one of items 1 to 3, comprising

[0071] <Item 5> A method for manufacturing a power storage module including a plurality of sub-modules, Each of the plurality of sub-modules is a device group in which a plurality of flat rectangular power storage devices are arranged such that flat surfaces face each other between adjacent power storage devices, A restraint member that restrains the device group along the arrangement direction of the power storage devices and comprising A temperature distribution prediction step of predicting the temperature distribution inside the power storage module when the plurality of power storage devices are charged and discharged, A preparation step of preparing a plurality of device groups in which the surplus electrolyte volume of other power storage devices is in the range of 90% to 110% when the reference surplus electrolyte volume R S which is the surplus electrolyte volume of an arbitrarily selected reference device is set to 100%, A restraint step of restraining each of the device groups with a restraint pressure based on the temperature T during charging and discharging of the device group to be restrained and the reference surplus liquid volume R S of the reference device of the device group to be restrained A method for manufacturing a power storage module, including

Explanation of symbols

[0072] 1 Power storage device 1X Reference device 1a Flat surface 2 Battery case 2a Positive electrode terminal 3 Electrode body 4 Electrolyte 4a Excess electrolyte 10A~10G Sub-module 20 Device group 2b Negative electrode terminal 30 Restraining member 32 Restraining band 34 Restraining plate 36 Worm gear 36a Worm 36b Worm wheel 38 Frame body 38a Accommodating part 39 Buffer plate 50 Cooling device 51 Intake port 52 Exhaust port 53 Air-cooling fan 54 Cooling control device 60 Temperature sensor 70 Control unit 72 Pressure calculation unit 74 Liquid volume memory unit 76 Correction unit 78 Temperature distribution memory unit 100 Power storage module

Claims

1. A power storage module including a plurality of submodules, each of the plurality of the submodules includes a device group in which a plurality of flat rectangular power storage devices are arranged such that flat surfaces face each other between adjacent power storage devices, and a restraint member that restrains the device group along the arrangement direction of the power storage devices, and each of the device groups includes one reference device arbitrarily selected from the plurality of power storage devices included in the device group, The reference surplus liquid volume R, which is the liquid volume of the surplus electrolytic solution of the reference device Ｓ when taken as 100%, and another power storage device in which the liquid volume of the surplus electrolytic solution is within the range of 90% to 110% and Each of the restraint members is based on the temperature T during charging and discharging of the device group to be restrained and the reference surplus liquid amount R of the reference device of the device group to be restrained. Ｓ A power storage module in which the restraint pressure on the device group to be restrained is set.

2. The power storage module according to claim 1, wherein each of the restraint members reduces the restraint pressure on the device group having a relatively low temperature T during charge and discharge and increases the restraint pressure on the device group having a relatively high temperature T during charge and discharge.

3. Each of the restraining members reduces the restraining pressure on the device group with a relatively large reference surplus liquid volume R Ｓ and increases the restraining pressure on the device group with a relatively small reference surplus liquid volume R Ｓ The power storage module according to claim 2.

4. A temperature sensor that measures the temperature inside the power storage module, and a control unit that controls the restraint pressure of each of the plurality of restraint members, and the control unit includes a pressure calculation unit that calculates the restraint pressure of each of the plurality of restraint members based on the measurement result of the temperature sensor, The reference surplus liquid volume R of each of the plurality of the device groups Ｓ and a liquid volume storage unit that stores the same the reference surplus liquid amount R Ｓ a correction unit that corrects the restraint pressure calculated by the pressure calculation unit based on and the power storage module according to claim 3.

5. A method for manufacturing a power storage module including a plurality of submodules, each of the plurality of the submodules includes a device group in which a plurality of flat rectangular power storage devices are arranged such that flat surfaces face each other between adjacent power storage devices, and a restraint member that restrains the device group along the arrangement direction of the power storage devices, and includes a temperature distribution prediction step of predicting the temperature distribution inside the power storage module when the plurality of power storage devices are charged and discharged, Reference surplus liquid amount R, which is the surplus electrolyte amount of an arbitrarily selected reference device Ｓ A preparation step of preparing a plurality of device groups in which the surplus electrolyte amounts of other power storage devices are within the range of 90% to 110% when the reference surplus liquid amount R is set to 100%; The temperature T during charging and discharging of the device group to be constrained, and the reference surplus liquid amount R of the reference device of the device group to be constrained Ｓ A constraining step of constraining each of the device groups with a constraining pressure based on the above and the method for manufacturing a power storage module.

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