Electric storage module and method for manufacturing the same

Abstract

To provide a power storage module with a novel configuration, capable of leveling high rate resistances of a plurality of power storage devices.SOLUTION: A power storage module 500 includes a plurality of power storage devices 100. A low-temperature region A1 with relatively low temperature and a high-temperature region A2 with relatively high temperature exist in the power storage module 500 when the plurality of power storage devices 100 are charged and discharged. Each of the plurality of power storage devices 100 includes: a flat square battery case 10; and an electrode body 20 that is accommodated inside the battery case 10 and has a flat portion 20a facing a flat surface 10a of the battery case 10. Of the plurality of power storage devices 100, a first power storage device 110 disposed in the low-temperature region A1 has the flat surface 10a of the battery case 10 having a rigidity lower than that of a second power storage device 120 disposed in the high-temperature region A2.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a power storage module including a plurality of power storage devices and a method for manufacturing the same.

Background Art

[0002] Conventionally, in power sources for vehicle drive and the like, a power storage module formed by electrically connecting a plurality of power storage devices (single cells) has been widely used. As related prior art documents, Patent Documents 1 and 2 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 cell group in which a plurality of power storage devices (single cells) are arranged, and a restraint member that applies a restraint pressure in the arrangement direction to restrain the cell group. And, there is a region in the housing that tends to become relatively low in temperature, and the sub-module arranged in the region that tends to become low in temperature is configured such that the restraint pressure of the restraint member is relatively lower than that of other sub-modules. Patent Document 1 describes that by reducing the restraint pressure on the power storage device in a region (a region that tends to become low in temperature) 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 can be equalized.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in the above Patent Document 1, it is not possible to make the restraint pressures different for a plurality of power storage devices included in one cell group. Therefore, according to the study by the present inventors, when a temperature distribution occurs within the cell group, it may be difficult to equalize the high-rate resistance of the plurality of power storage devices. Further, since a restraint member is essential for each cell group, the restraint member is bulky and the volumetric energy density of the entire power storage module decreases. For example, when the power storage module is mounted on a moving body such as a vehicle, there is a risk that the weight increases and the fuel consumption deteriorates.

[0006] The present invention has been made in view of the above circumstances, and its main object is to provide a power storage module having a novel configuration and a method for manufacturing the same, which can equalize the high-rate resistance of a plurality of power storage devices.

Means for Solving the Problems

[0007] According to the present invention, there is provided a power storage module including a plurality of power storage devices. Each of the plurality of power storage devices included in this power storage module has a flat rectangular battery case and an electrode body housed in the battery case and having a flat portion facing the flat surface of the battery case. Further, in this power storage module, when the plurality of power storage devices are charged and discharged, there are a low-temperature region where the temperature relatively decreases and a high-temperature region where the temperature relatively increases. And in this power storage module, among the plurality of power storage devices, the first power storage device arranged in the low-temperature region has a lower rigidity of the flat surface of the battery case than the second power storage device arranged in the high-temperature region.

[0008] The present invention also provides a method for manufacturing a power storage module including a plurality of power storage devices. Each of the plurality of power storage devices included in this power storage module has a flat rectangular battery case and an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case. And the method for manufacturing this power storage module includes a preparation step of preparing, as a plurality of power storage devices, a first power storage device having a relatively low rigidity of the flat surface of the battery case and a second power storage device having a relatively high rigidity of the flat surface of the battery case, a temperature distribution prediction step of predicting the temperature distribution in the power storage module when the plurality of power storage devices are charged and discharged, and a construction step of constructing the power storage module by arranging the first power storage device in a relatively low-temperature region where the temperature is relatively low and the second power storage device in a relatively high-temperature region where the temperature is relatively high based on the temperature distribution.

[0009] As a result of various studies by the present inventors, it has been found that a power storage device having a low rigidity of the flat surface of the battery case is relatively excellent in high-rate resistance. Therefore, in the present invention, a power storage device having a relatively low rigidity (high high-rate resistance) of the flat surface is arranged in a low-temperature region where the high-rate resistance is likely to decrease. Thereby, the high-rate resistance of a plurality of power storage devices can be leveled. As a result, the high-rate resistance of the entire power storage module can be improved. Further, unlike the technique of Patent Document 1, since there is no need to be restricted by the framework of "cell group", the high-rate resistance of individual power storage devices can be flexibly adjusted. Furthermore, since the number of restraint members can be reduced as compared with the technique of Patent Document 1, the volume energy density and fuel consumption can also be improved.

Brief Description of the Drawings

[0010]

Figure 1

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[0011] Hereinafter, preferred embodiments of the technology disclosed herein will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention (for example, general configurations and manufacturing processes of power storage modules and power storage devices that do not characterize the present invention) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The power storage module disclosed herein can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field.

[0012] In the following drawings, members and parts having the same function are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified. Also, the notation "A to B" indicating a range in this specification includes the meaning of "A or more and B or less" as well as the meaning of "preferably greater than A" and "preferably less than B".

[0013] [Power Storage Module] FIG. 1 is a perspective view schematically showing a power storage module 500. The power storage module 500 here includes a plurality of power storage devices 100, a plurality of spacers 200, and a restraint mechanism 300. However, the plurality of spacers 200 and the restraint mechanism 300 are not essential and can be omitted in other embodiments.

[0014] In the following description, the reference signs L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, up, and down, respectively, and the reference signs X, Y, and Z in the drawings represent the short side direction, the long side direction orthogonal to the short side direction, and the up-down direction of the power storage device 100, respectively. The short side direction X is also the arrangement direction of the power storage devices 100. However, these are merely directions for convenience of explanation and do not limit the installation form of the power storage module 500 in any way.

[0015] The restraint mechanism 300 is a member that restrains a plurality of power storage devices 100. There is one restraint mechanism 300 here. The restraint mechanism 300 is configured to apply an equal restraint pressure from the arrangement direction X to all the power storage devices 100 and the spacers 200. The restraint mechanism 300 includes a pair of end plates 310, a pair of side plates 320, and a plurality of screws 330. The pair of end plates 310 and the pair of side plates 320 can also be regarded as a housing for accommodating a plurality of power storage devices 100. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal.

[0016] A pair of end plates 310 are disposed at both ends of the power storage module 500 in the array direction X. The pair of end plates 310 sandwich a plurality of power storage devices 100 and a plurality of spacers 200 in the array direction X. A pair of side plates 320 bridge the pair of end plates 310. The pair of side plates 320 are fixed to the end plates 310 by a plurality of screws 330 such that the restraint load is about 10 to 15 kN, for example. Thereby, a uniform restraint load is applied to the plurality of power storage devices 100 from the array direction X, and the plurality of power storage devices 100 are integrally held. However, the configuration of the restraint mechanism is not limited to this. The restraint mechanism 300 may include, for example, a plurality of restraint bands, binding bars, etc. instead of the side plates 320.

[0017] The spacers 200 are each disposed here between the plurality of power storage devices 100 in the array direction X. That is, in the array direction X, the power storage devices 100 and the spacers 200 are arranged alternately. However, when the power storage module 500 does not include the spacers 200, the power storage devices 100 adjacent to each other in the array direction X may be in contact (in direct contact). The spacer 200 preferably includes a porous structure portion through which a fluid (typically a gas such as air) can pass.

[0018] The power storage device 100 is a device capable of repeated charge and discharge. In this specification, the “power storage device” is a concept that includes secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors such as lithium-ion capacitors and electric double-layer capacitors. The plurality of power storage devices 100 are arranged here between the pair of end plates 310 along the array direction X (in other words, the thickness direction X of the power storage device 100). The plurality of power storage devices 100 are preferably restrained by the restraint mechanism 300. Note that the shape, size, number, etc. of the plurality of power storage devices 100 are not limited to the embodiments disclosed in FIG. 1 and can be appropriately changed.

[0019] Although illustration is omitted here, when the power storage module 500 is used, a plurality of power storage devices 100 are electrically connected to each other by a conductive member such as a bus bar. The connection method is not particularly limited, and may be, for example, series, parallel, or multi-series multi-parallel, etc. In a preferred embodiment, a plurality of power storage devices 100 are connected in series. Thereby, for example, the output characteristics can be preferably improved to a level suitable for use in a moving body such as a vehicle. Also, in the case of series connection, deterioration of the performance of some of the power storage devices 100 is likely to lead to deterioration of the performance of the entire power storage module 500. Therefore, it is particularly effective to apply the technology disclosed herein.

[0020] FIG. 2 is a perspective view of the power storage device 100. As can be seen from FIGS. 1 and 2, the plurality of power storage devices 100 are all flat rectangular shapes and are of the same shape here. The plurality of power storage devices 100 are arranged such that the long side walls 12b described later are parallel to each other. The plurality of power storage devices 100 are arranged side by side in the arrangement direction X such that the long side walls 12b face each other via the spacer 200 here.

[0021] FIG. 3 is a schematic longitudinal sectional view taken along line III-III of FIG. 2. As shown in FIG. 3, the power storage device 100 includes, here, a battery case 10, an electrode body 20, a positive electrode terminal 30, a negative electrode terminal 40, and a non-aqueous electrolyte (not shown). The power storage device 100 is configured by housing the electrode body 20 and the non-aqueous electrolyte in the battery case 10 to which the positive electrode terminal 30 and the negative electrode terminal 40 are attached. The power storage device 100 is typically a non-aqueous electrolyte secondary battery and is a lithium ion secondary battery here. When the power storage device 100 is a lithium ion secondary battery, it is particularly effective to apply the technology disclosed herein.

[0022] The battery case 10 is a container that houses the electrode body 20 and the non-aqueous electrolyte. As shown in FIG. 2, the battery case 10 has an outer shape that is flat, bottomed, and rectangular parallelepiped (rectangular) here. The material of the battery case 10 may be the same as those conventionally used, and there is no particular limitation. The battery case 10 is made of, for example, aluminum, aluminum alloy, iron, iron alloy, or the like. As shown in FIG. 3, the battery case 10 includes an exterior body 12 having an opening 12h, and a sealing plate (lid body) 14 that seals the opening 12h. As shown in FIG. 2, the exterior body 12 includes a substantially rectangular bottom wall 12a having a long side and a short side, a pair of long side walls 12b extending from the long side of the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the short side of the bottom wall 12a and facing each other. The long side wall 12b is flat.

[0023] The sealing plate 14 is a plate-like member. The sealing plate 14 is substantially rectangular. As shown in FIG. 3, the sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The battery case 10 is integrated by joining (preferably, welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed. The sealing plate 14 is provided with a liquid injection hole 15 and two terminal lead-out holes 18 and 19. The liquid injection hole 15 is for injecting the non-aqueous electrolyte after assembling the sealing plate 14 to the exterior body 12. The liquid injection hole 15 is sealed by a sealing member 16. The terminal lead-out holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z.

[0024] The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the long side direction Y (the left end in FIGS. 2 and 3), and the negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIGS. 2 and 3). As shown in FIG. 3, the positive electrode terminal 30 and the negative electrode terminal 40 respectively extend from the inside to the outside of the sealing plate 14 through the terminal lead holes 18 and 19. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are caulked to the peripheral portion surrounding the terminal lead holes 18 and 19 of the sealing plate 14 by caulking. Caulking portions 30c and 40c are formed at the ends on the side of the outer package 12 of the positive electrode terminal 30 and the negative electrode terminal 40 (the lower end in FIG. 3). Thereby, the positive electrode terminal 30 and the negative electrode terminal 40 are fixed to the sealing plate 14.

[0025] As shown in FIG. 3, the positive electrode terminal 30 is electrically connected to the positive electrode tab group 23 of the electrode body 20 via the positive electrode current collecting portion 50 inside the outer package 12. The positive electrode terminal 30 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90. The negative electrode terminal 40 is electrically connected to the negative electrode tab group 25 of the electrode body 20 via the negative electrode current collecting portion 60 inside the outer package 12. The negative electrode terminal 40 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90.

[0026] As shown in FIGS. 2 and 3, plate-shaped positive electrode external conductive members 32 and negative electrode external conductive members 42 are attached to the outer surface of the sealing plate 14. The positive electrode external conductive member 32 is electrically connected to the positive electrode terminal 30. The negative electrode external conductive member 42 is electrically connected to the negative electrode terminal 40. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are members to which conductive members such as bus bars for electrically connecting a plurality of power storage devices 100 to each other are attached. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are insulated from the sealing plate 14 by the external insulating member 92. The power storage module 500 is connected in series, for example, by electrically connecting the positive electrode external conductive member 32 of one power storage device 100 and the negative electrode external conductive member 42 of the other power storage device 100 among the power storage devices 100 adjacent to each other in the array direction X with a bus bar or the like.

[0027] FIG. 4 is a schematic diagram showing the configuration of the electrode body 20. Further, FIG. 5 is a schematic longitudinal sectional view taken along the line V-V of FIG. 3. As shown in FIG. 4, the electrode body 20 includes a positive electrode 22, a negative electrode 24, and a separator 26. Here, the electrode body 20 is a wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are laminated via a strip-shaped separator 26 and wound around a winding axis WL. The electrode body 20 has a flat outer shape. As shown in FIGS. 3 and 5, the electrode body 20 is housed inside the battery case 10 (outer package 12). At this time, as shown in FIG. 5, the flat portion 20a of the flat-shaped electrode body 20 faces the flat surface 10a of the battery case 10 (the long side wall 12b of the outer package 12). Note that the electrode body 20 only needs to have a flat portion 20a facing the flat surface 10a of the battery case 10, and is not limited to the wound electrode body shown in FIG. 4. For example, the electrode body 20 may be a laminated electrode body in which a plurality of square (typically rectangular) positive electrodes and a plurality of square (typically rectangular) negative electrodes are stacked in an insulated state.

[0028] The configuration of the positive electrode 22 may be the same as that of the related art. Here, the positive electrode 22 includes a positive electrode current collector 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed on at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is preferably made of metal, and more preferably made of a metal foil. Here, the positive electrode current collector 22c is an aluminum foil.

[0029] On one end (the left end in FIG. 4) of the positive electrode current collector 22c in the long side direction Y, a plurality of positive electrode tabs 22t are provided. The plurality of positive electrode tabs 22t protrude toward one side (the left side in FIG. 4) in the long side direction Y. The plurality of positive electrode tabs 22t protrude in the long side direction Y more than the separator 26. The positive electrode tab 22t is here a part of the positive electrode current collector 22c and is made of a metal foil (aluminum foil). The plurality of positive electrode tabs 22t are laminated at one end (the left end in FIG. 4) in the long side direction Y to form a positive electrode tab group 23. The positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collecting portion 50.

[0030] The positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material capable of reversibly occluding and releasing charge carriers. Examples of the positive electrode active material include lithium transition metal composite oxides. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as various additive components such as a binder and a conductive material.

[0031] The positive electrode protective layer 22p is provided at the boundary portion between the positive electrode current collector 22c and the positive electrode active material layer 22a in the long side direction Y. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (for example, alumina). The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additive components.

[0032] The configuration of the negative electrode 24 may be the same as that of the prior art. Here, the negative electrode 24 has a negative electrode current collector 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector 24c. The negative electrode current collector 24c is strip-shaped. The negative electrode current collector 24c is preferably made of metal, and more preferably made of a metal foil. Here, the negative electrode current collector 24c is a copper foil.

[0033] At one end (the right end in FIG. 4) of the negative electrode current collector 24c in the long side direction Y, a plurality of negative electrode tabs 24t are provided. The plurality of negative electrode tabs 24t protrude toward one side in the long side direction Y (the right side in FIG. 4). The plurality of negative electrode tabs 24t protrude in the long side direction Y more than the separator 26. Here, the negative electrode tab 24t is a part of the negative electrode current collector 24c and is made of a metal foil (copper foil). The plurality of negative electrode tabs 24t are laminated at one end (the right end in FIG. 4) in the long side direction Y to form a negative electrode tab group 25. The negative electrode tab group 25 is provided at a position symmetric to the positive electrode tab group 23 in the long side direction Y. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collecting portion 60.

[0034] The negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the negative electrode current collector 24c. The length Ln of the negative electrode active material layer 24a in the long side direction Y is preferably the same as or longer than the length Lp of the positive electrode active material layer 22a in the long side direction Y. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly occluding and releasing charge carriers. Examples of the negative electrode active material include carbon materials such as graphite. The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as various additive components such as a binder, a thickener, and a dispersant.

[0035] The separator 26 is disposed between the positive electrode 22 and the negative electrode 24. The separator 26 is a member that insulates the positive electrode 22 and the negative electrode 24. The configuration of the separator 26 may be the same as that of the prior art. The length Ls of the separator 26 in the long side direction Y is preferably the same as or longer than the length Ln of the negative electrode active material layer 24a in the long side direction Y. As the separator 26, for example, a resinous porous sheet (micro-porous membrane) made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. The separator 26 may be provided with a functional layer (for example, an adhesive layer or a heat-resistant layer) on the surface of the porous sheet.

[0036] The configuration of the non-aqueous electrolyte may be the same as that of the conventional one. The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt (electrolyte salt). The non-aqueous solvent is, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as lithium hexafluorophosphate (LiPF6) or lithium bis(fluorosulfonyl)imide (LiFSI). The non-aqueous electrolyte may further contain additives as necessary. The non-aqueous electrolyte is typically liquid, but may also be gel-like. Further, in other embodiments, the power storage device 100 may be provided with a solid electrolyte instead of the non-aqueous electrolyte. In that case, the separator 26 can be omitted.

[0037] FIG. 6 is a plan view schematically showing the power storage module 500 and the cooling device 400. In FIG. 6, detailed illustration of the upper surface of the power storage device 100 is omitted. As shown in FIG. 6, the cooling device 400 here includes an intake port IP, an exhaust port OP, an air-cooling fan 410, a temperature sensor 420, and a control device 430. The cooling device 400 is an air-cooling type cooling device that uses air as a refrigerant here. However, in other embodiments, the cooling device 400 may be a liquid-cooling type cooling device that uses a liquid refrigerant.

[0038] In the present embodiment, the intake port IP is provided on one side (front F side) in the arrangement direction X of the power storage module 500. The exhaust port OP is provided on the other side (rear Rr side) in the arrangement direction X. The air-cooling fan 410 is attached to the intake port IP. The air-cooling fan 410 is configured to send wind (air) to the intake port IP. The configuration of the air-cooling fan 410 is not limited, but for example, it includes an electric motor (not shown). The temperature sensor 420 is arranged at the center in the XY plane of the power storage module 500 here. The temperature sensor 420 is, for example, a thermocouple or a thermistor.

[0039] The control device 430 is electrically connected to the temperature sensor 420 and the electric motor of the air-cooling fan 410. When it is detected by, for example, the temperature sensor 420 that the temperature inside the power storage module 500 has reached a predetermined first temperature or higher, the control device 430 operates the air-cooling fan 410. As a result, low-temperature air outside the power storage module 500 is supplied into the power storage module 500 from the intake port IP, and an air flow AF is generated inside the power storage module 500. The supplied air passes through the inside of the power storage module 500 while cooling the power storage device 100, and is discharged from the exhaust port OP. When it is detected by, for example, the temperature sensor 420 that the temperature inside the power storage module 500 has reached a predetermined second temperature or lower, the control device 430 stops the air-cooling fan 460. According to such an air-cooling type cooling device 400, the power storage device 100 can be cooled at low cost.

[0040] Incidentally, according to the study by the present inventors, inside the power storage module 500 provided with a cooling mechanism such as the cooling device 400, for example, a temperature distribution occurs during charging and discharging of a plurality of power storage devices 100, and a low-temperature region A1 where the temperature relatively becomes low and a high-temperature region A2 where the temperature relatively becomes high may occur. Specifically, when the power storage device 100 generates heat due to charging and discharging, adjacent power storage devices 100 heat each other. As a result, in the central portion in the arrangement direction X, a chain-like heat generation occurs between the power storage devices 100, and the temperature tends to become relatively high. On the other hand, both end portions in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 6) are more heat dissipative than the central portion, and thus chain-like heat generation hardly occurs. Therefore, at both end portions in the arrangement direction X, the temperature tends to become relatively low.

[0041] Particularly in this embodiment, an intake port IP through which refrigerant (air) is supplied and an air-cooling fan 410 are arranged on the front F side in the arrangement direction X, and an exhaust port OP is arranged on the rear Rr side in the arrangement direction X. For this reason, both ends in the arrangement direction X tend to become low in temperature. Therefore, the central portion in the arrangement direction X becomes a high-temperature region A2 with a relatively high temperature, and both ends in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 6) tend to become low-temperature regions A1 with a relatively low temperature. In particular, the front F portion in the arrangement direction X where the intake port IP and the air-cooling fan 410 are arranged is most likely to become the lowest in temperature. That is, in this embodiment, at least the front F side in the arrangement direction X is likely to become a low-temperature region A1 with a relatively low temperature.

[0042] As described in Patent Document 1 and the like, for example, when such a temperature distribution occurs in the power storage module 500, variations may occur in the high-rate tolerance of the power storage device 100. Specifically, the high-rate tolerance of the power storage device 100 may decrease in the low-temperature region A1. In this case, if the charge and discharge of the entire power storage module 500 are controlled based on the high-rate tolerance of the power storage device 100 in the low-temperature region A1, the high high-rate tolerance of the power storage device 100 in the high-temperature region A2 cannot be fully utilized. On the other hand, if the high-rate tolerance of the power storage device 100 in the high-temperature region A2 is used as a reference, a high voltage is applied to the power storage device 100 in the low-temperature region A1, and high-rate degradation is likely to accelerate. Thus, when a temperature distribution occurs in the power storage module 500, the high-rate tolerance of the entire power storage module 500 may decrease due to being restricted by the high-rate tolerance of the power storage device 100 in the low-temperature region A1. Furthermore, when the power storage module is mounted on a moving body such as a vehicle, there is also a possibility that the fuel consumption may deteriorate.

[0043] Therefore, in the power storage module 500 according to the present embodiment, the first power storage device 110 and the second power storage device 120 with different rigidities of the flat surface 10a of the battery case 10 are used. Specifically, the first power storage device 110 in the present embodiment is configured such that the thickness T (see FIG. 5) of the flat surface 10a of the battery case 10 is thinner than that of the second power storage device 120. As shown in the test examples described later, the inventors of the present invention have confirmed that the high rate resistance increases as the thickness T of the flat surface 10a of the battery case 10 decreases. Therefore, in the present embodiment, the first power storage device 110 with relatively high high rate resistance is arranged in the low temperature region A1 (both ends in the arrangement direction X) where the temperature is relatively low. In addition, the second power storage device 120 with relatively low high rate resistance is arranged in the high temperature region A2 (the central portion in the arrangement direction X) where the temperature is relatively high.

[0044] According to such a configuration, the high rate resistance of the plurality of power storage devices 100 can be leveled at a high level. As a result, the acceleration of deterioration can be suppressed, and the high rate resistance of the entire power storage module 500 can be improved. In addition, unlike the technology of Patent Document 1, since there is no need to be restricted by the framework of "cell group", the high rate resistance of the plurality of power storage devices 100 can be flexibly adjusted according to the temperature distribution in the power storage module 500. Therefore, in some cases, the high rate resistance of the plurality of power storage devices 100 can be leveled with higher accuracy than the technology of Patent Document 1. Furthermore, since the number of the restraint mechanisms 300 can be reduced compared with the technology of Patent Document 1, the volume energy density and the fuel consumption can also be improved. In addition, the number of parts can be reduced, and the manufacturing cost can be reduced.

[0045] Note that the thickness T1 of the flat surface 10a of the battery case 10 of the first power storage device 110 (hereinafter also referred to as the "first battery case") is preferably 1.25 mm or less, more preferably 1.0 mm or less, still more preferably 0.75 mm or less, and particularly preferably 0.5 mm or less. Thereby, the high-rate tolerance of the first power storage device 110 can be more suitably improved, and the high-rate tolerance of the entire power storage module 500 can be leveled at a higher level. On the other hand, the thickness T1 of the flat surface 10a of the first battery case is preferably 0.25 mm or more, more preferably 0.3 mm or more, still more preferably 0.35 mm or more, and particularly preferably 0.4 mm or more. Thereby, the problem of poor welding between the sealing plate 14 and the battery case 10 can be prevented.

[0046] On the other hand, the thickness T2 of the flat surface 10a of the battery case 10 of the second power storage device 120 (hereinafter also referred to as the "second battery case") is preferably 0.5 mm or more, more preferably 0.75 mm or more, still more preferably 1.0 mm or more, and particularly preferably 1.25 mm or more. Thereby, since the high-rate tolerance of the second power storage device 120 is likely to be lower than that of the first power storage device 110, it becomes easier to level the high-rate tolerance of the entire power storage module 500. On the other hand, the thickness T2 of the flat surface 10a of the second battery case is preferably 2.25 mm or less, more preferably 2.0 mm or less, still more preferably 1.75 mm or less, and particularly preferably 1.5 mm or less. Thereby, the problem of a decrease in energy density can be prevented.

[0047] Also, the thickness ratio (T2 / T1) of the flat surface of the second battery case to the first battery case is preferably adjusted as appropriate from the viewpoint of leveling the high-rate tolerance in the entire power storage module 500. As an example, the above thickness (T2 / T1) is preferably 1.1 or more, more preferably 1.2 or more, and particularly preferably 1.3 or more. Thereby, the high-rate tolerance of the entire power storage module 500 can be more appropriately leveled. On the other hand, the upper limit value of the above thickness ratio (T2 / T1) is preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less. Thereby, the problem of poor welding between the sealing plate 14 and the battery case 10 and the problem of a decrease in energy density can be prevented.

[0048] [Method for manufacturing a power storage module] Next, a method for manufacturing a power storage module 500 including a plurality of power storage devices 100 will be described. The power storage module 500 can be manufactured, for example, by a manufacturing method including: (Step A) a preparation step of preparing a first power storage device 110 and a second power storage device 120; (Step B) a temperature distribution prediction step of predicting the temperature distribution within the power storage module 500; and (Step C) a construction step of constructing the power storage module 500 by combining the first power storage device 110 and the second power storage device 120. The manufacturing method disclosed herein may further include other steps at any stage. Note that the order of (Step A) the preparation step and (Step B) the temperature distribution prediction step is not particularly limited. For example, (Step B) the temperature distribution prediction step may be performed after (Step A) the preparation step, or (Step A) the preparation step may be performed after (Step B) the temperature distribution prediction step.

[0049] (Step A) In the preparation step, as the plurality of power storage devices 100, a first power storage device 110 having a relatively thin thickness T of the flat surface 10a of the battery case 10 and a second power storage device 120 having a relatively thick thickness T of the flat surface 10a of the battery case 10 are prepared. In the present embodiment, (Step A) the preparation step includes, in this order: (A-1) a case preparation step of preparing the battery case 10; (A-2) a housing step of housing the electrode body 20 in the battery case 10; and (A-3) a conditioning step.

[0050] (A-1) In the case preparation step, a plurality (at least two types) of battery cases 10 (outer packages 12) having different thicknesses T of the flat surface 10a are prepared. Specifically, as the battery case 10 for the first power storage device 110, a first battery case having a relatively thin thickness T of the flat surface 10a is prepared. On the other hand, as the battery case 10 for the second power storage device 120, a second battery case having a relatively thick thickness T of the flat surface 10a is prepared. Each battery case 10 may be purchased as a commercially available product or manufactured by a conventionally known method.

[0051] (A-2) In the accommodation process, the separately prepared electrode body 20 is accommodated in the battery case 10. In a preferred embodiment, first, the positive electrode tab group 23 of the electrode body 20 is joined to the positive electrode current collector 50, and the negative electrode tab group 25 of the electrode body 20 is joined to the negative electrode current collector 60. Thereby, the sealing plate 14 and the electrode body 20 are integrated. Then, after inserting the electrode body 20 into the opening 12h of the exterior body 12, the opening on the upper surface of the exterior body 12 is sealed with the sealing plate 14. Thereby, the electrode body 20 is accommodated inside the battery case 10. Next, the sealing plate 14 is welded to the periphery of the opening 12h of the exterior body 12 to integrate the exterior body 12 and the sealing plate 14. Next, the electrolytic solution is injected into the battery case 10 through the liquid injection hole 15 of the sealing plate 14. Thereby, a precursor (battery assembly) of the power storage device 100 is produced.

[0052] (A-3) In the conditioning process, the produced battery assembly is charged at least once. Preferably, the produced battery assembly is charged and discharged at least once. The charging and discharging of the battery assembly can be performed in the same manner as in the prior art. Typically, an external power source is connected between the positive electrode terminal 30 and the negative electrode terminal 40, and charging or discharging is performed until the terminals reach a predetermined state of charge (SOC). Then, the battery case 10 is hermetically sealed. In the above manner, the first power storage device 110 and the second power storage device 120 with different thicknesses T of the flat surface 10a of the battery case 10 can be prepared.

[0053] (Project B) In the temperature distribution prediction process, the temperature distribution within the power storage module 500 is predicted when a plurality of power storage devices 100 are charged and discharged. That is, for example, in the mode as shown in FIG. 6, both end portions in the array direction X (particularly the front F portion in the array direction X) are likely to be low-temperature regions A1. However, the temperature distribution within the power storage module 500 can also vary depending on the configuration of the cooling device 400 (for example, the intake port IP, the exhaust port OP, the installation position and number of the air-cooling fans 410) and the heat dissipation path. Also, for example, the range (the length in the array direction X) of the low-temperature region A1 can vary depending on, for example, the number of power storage devices 100 and the charge-discharge conditions. Therefore, it is preferable to predict the temperature distribution within the power storage module 500 during charge and discharge by means of preliminary experiments or simulations using commercially available analysis software. In particular, it is preferable to construct a power storage module for preliminary tests simulating the power storage module 500, measure the temperature distribution actually, and predict the temperature distribution within the power storage module 500 based on the actual measurement.

[0054] In a preferred embodiment, first, a plurality of power storage devices for preliminary tests different from the first power storage device 110 and the second power storage device 120 manufactured in the preparation process are prepared, and temperature sensors are attached to each of them. Next, using the plurality of power storage devices for preliminary tests, a power storage module for preliminary tests simulating the power storage module 500 is assembled. Next, the plurality of power storage devices for preliminary tests are actually charged and discharged (preferably at high rate charge and discharge), and the temperature distribution at this time is acquired. The charge-discharge conditions are preferably conditions assuming the actual usage mode. Then, based on the acquired temperature distribution, the temperature distribution within the power storage module 500 is predicted and, for example, divided into a low-temperature region A1 and a high-temperature region A2 (for example, divided into two parts).

[0055] (Project C) In the construction process, based on the temperature distribution predicted in the temperature distribution prediction process, the first power storage device 110 and the second power storage device 120 are arranged to construct the power storage module 500. Specifically, the first power storage device 110 having the first battery case is arranged in the area separated from the low-temperature region A1. On the other hand, the second power storage device 120 having the second battery case is arranged in the area separated from the high-temperature region A2. Then, for example, together with a plurality of spacers 200, the first power storage device 110 and the second power storage device 120 are constrained by the constraint mechanism 300 and held integrally. In this way, the power storage module 500 can be constructed.

[0056] [Applications of the Power Storage Module] The power storage module 500 can be used for various applications. Since it has excellent high-rate resistance, it can be preferably used as a power source (driving power source) for motors mounted on vehicles that require high output, such as passenger cars, trucks, etc. The type of vehicle is not particularly limited, and examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), etc. By mounting the power storage module 500 on a moving body such as a vehicle, the fuel consumption (electricity cost) of the moving body can be improved.

[0057] Hereinafter, some test examples related to the present invention will be described, but the present invention is not intended to be limited to such test examples.

[0058] In this test example, a plurality of power storage devices with different thicknesses of the flat surface of the battery case were constructed, and the high-rate resistance of each was confirmed. Specifically, as shown in Table 1, three types of power storage devices (lithium-ion secondary batteries, Examples 1 to 3) with different thicknesses of the flat surface of the battery case were fabricated. Note that the "thickness of the flat surface" in Table 1 is the ratio with the thickness of the flat surface of Example 1 (0.5 mm) taken as 1 (reference value). Also, the configurations other than the battery case (such as the electrode body) are common to all the power storage devices. Next, in a temperature environment of 25 °C, the power storage device was adjusted to a state of SOC 50%, 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 this battery voltage ΔV and the discharge current value (150 A), the IV resistance (initial resistance) was calculated.

[0059] Next, in a temperature environment of 25 °C, the power storage device was adjusted to a state of SOC 50%, constant current charging was performed at a charging rate of 150 A for 10 seconds, then it was paused for 5 seconds, and then constant current discharge was performed at a discharge rate of 10 A for 150 seconds, followed by a 5-second pause. One cycle of such charge and discharge was defined as one cycle, and this was repeated 1000 times 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).

[0060]

Table 1

[0061] As shown in Table 1, it was confirmed that as the thickness of the flat surface of the battery case decreased, the resistance increase rate after the high-rate durability test tended to decrease. From the above, it was found that a power storage device having a battery case with a thin flat surface is relatively superior in high-rate resistance compared to a power storage device having a battery case with a thick flat surface.

[0062] The preferred embodiments of the present invention have been described above, but the above embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the content disclosed in this specification and common general knowledge in the art. The technology described in the claims includes various modifications and changes of the above-exemplified embodiments. For example, it is possible to replace a part of the above-described embodiments with other modified examples, and it is also possible to add other modified examples to the above-described embodiments. Further, if the technical features are not described as essential, they can be appropriately deleted.

[0063] (1) For example, in the above-described embodiment, the thickness of the flat surface 10a of the battery case 10 is made different between the first power storage device 110 and the second power storage device 120. However, the technology disclosed herein may be such that the rigidity of the flat surface 10a of the battery case 10 of the first power storage device 110 is made lower than that of the flat surface 10a of the battery case 10 of the second power storage device 120. That is, the technology disclosed herein is not limited to the form of making the thickness of the flat surface 10a of the battery case 10 different as described above. For example, even when the thickness of the flat surface 10a is made constant, if the material of the battery case 10 is made different, the rigidity of each battery case 10 of the first power storage device 110 and the second power storage device 120 can be made different. Considering the mechanism of controlling the high-rate resistance by adjusting the expansion amount of the electrode body during high-rate charge and discharge, it is understood that the high-rate resistance can be leveled even in the above-described form.

[0064] Note that the ratio of the rigidity of the flat surface of the second battery case to the rigidity of the flat surface of the first battery case is preferably 1.2 or more, more preferably 1.45 or more, and particularly preferably 1.7 or more. Thereby, the high-rate resistance of the entire power storage module 500 can be more appropriately leveled. On the other hand, the upper limit value of the above-described rigidity ratio is preferably 16 or less, more preferably 9 or less, and particularly preferably 4 or less. Note that, similar to the above-described thickness ratio (T2 / T1) of the flat surface, it is preferable to appropriately adjust the ratio of the rigidity of the flat surface from the viewpoint of leveling the high-rate resistance in the entire power storage module 500.

[0065] (2) For example, in the above-described embodiment, in the (process A) preparation process, a power storage device 100 was manufactured in which the rigidity (thickness of the flat surface 10a) of the flat surface 10a of the battery case 10 was intentionally made different. However, the embodiment of the present invention is not limited to this. For example, it is also possible to select and prepare the first power storage device 110 and the second power storage device 120 from among a number of power storage devices in which the rigidity of the flat surface 10a of the battery case 10 varies, within a predetermined acceptable range.

[0066] As a specific example, when a used power storage device (which may be in the state of a power storage module) is recovered from the market and reused, that is, when the power storage device 100 is a reused product. In recent years, for example, power storage devices such as lithium-ion secondary batteries may be provided with identification information from the perspective of traceability and the like. In one example, an optical symbol readable by a reading device is attached to the surface of the power storage module (for example, the sealing plate 14). Alternatively, a small substrate containing identification information is mounted inside the power storage device or the like. The identification information may include, in addition to ID information such as model number, manufacturer name, country of manufacture, name of manufacturing factory, and date of manufacture, information regarding the structure of the battery case.

[0067] In this case, the (process A) preparation process may include: (1-a) an acquisition process of respectively reading the identification information attached to a number of recovered power storage devices to obtain information regarding the rigidity of the flat surface of the battery case; and (1-b) a sorting process of sorting out from among the plurality of power storage devices the first power storage device 110 having a relatively low rigidity of the flat surface of the battery case and the second power storage device 120 having a relatively high rigidity of the flat surface of the battery case. Such a method for manufacturing a power storage module can also be understood as a method for reusing a power storage device (reuse method). Note that in this specification, the "optical symbol" is a general term for an information medium that stores information by a combination of a portion with a high optical reflectance and a portion with a low optical reflectance, and includes two-dimensional symbols such as QR code (registered trademark), data matrix, and data tag (also referred to as two-dimensional code, two-dimensional barcode, etc.).

[0068] (3) For example, in the embodiment of FIG. 6 described above, both ends in the array direction X (the front F part and the rear Rr part in FIG. 6) are relatively low-temperature regions A1 with a low temperature, and the central part in the array direction X is a relatively high-temperature region A2 with a high temperature. However, it is not limited to this. As described above, the temperature distribution in the power storage module 500 can vary depending on the configuration of the cooling device 400 (for example, the intake port IP, the exhaust port OP, the installation position and number of the air-cooling fans 410), the number of power storage devices 100, the charge-discharge conditions, and the like. Also, in the embodiment of FIG. 6 described above, the inside of the power storage module 500 is divided into two temperature regions, a low-temperature region A1 and a high-temperature region A2, and further, the temperature distribution is symmetric with respect to the array direction X. However, it is not limited to this. For example, the inside of the power storage module 500 can also be divided into three or more temperature regions. In that case, in the embodiment of FIG. 6, the low-temperature region A1 on the rear Rr side in the array direction X may be set as a medium-temperature region A3 that is higher in temperature than the low-temperature region A1 and lower in temperature than the high-temperature region A2. Also, when the cooling path and the heat dissipation path are complicated, the temperature distribution may be random, for example, the low-temperature region A1 and the high-temperature region A2 may appear alternately. Hereinafter, several specific modification examples will be described with reference to FIGS. 7 to 10. Note that in FIGS. 7 to 10, the illustration of the cooling device is omitted.

[0069] (First Modification Example) FIG. 7 is a plan view of a power storage module 500a according to the first modification example. As described above, it is known that chain heat generation is likely to occur between the power storage devices 100 at the central part in the array direction X. Therefore, although not shown in FIG. 7, an intake port IP through which a refrigerant (air) is supplied and / or an air-cooling fan 410 may be additionally installed at the central part in the array direction X, and the central part may be strongly cooled. Then, as shown in FIG. 7, the temperature distribution of the power storage module 500a is, contrary to FIG. 6, such that the central part in the array direction X becomes a relatively low-temperature region A1, and both ends in the array direction X (the front F part and the rear Rr part in FIG. 7) may become relatively high-temperature regions A2.

[0070] In such cases, as shown in Fig. 7, a first power storage device 110 with relatively low rigidity (high high-rate resistance) of the flat surface 10a of the battery case 10 is arranged at the center of the array direction X in the low-temperature region A1, and a second power storage device 120 with relatively high rigidity (low high-rate resistance) of the flat surface 10a of the battery case 10 is arranged at both ends of the array direction X in the high-temperature region A2.

[0071] (Second and third modified examples) Fig. 8 is a plan view of a power storage module 500b according to the second modified example. Fig. 9 is a plan view of a power storage module 500c according to the third modified example. For example, when the air-cooling fan 410 installed on the front F side in the array direction X of Fig. 6 is powerful and has high cooling capacity, as shown in Figs. 8 and 9 respectively, the temperature distribution within the power storage modules 500b and 500c can be such that the front F part in the array direction X becomes a relatively low-temperature region A1, and the rear Rr part in the array direction X becomes a relatively high-temperature region A2.

[0072] In such cases, as shown in Figs. 8 and 9, a first power storage device 110 with relatively low rigidity (high high-rate resistance) of the flat surface 10a of the battery case 10 is arranged at the front F part in the array direction X in the low-temperature region A1, and a second power storage device 120 with relatively high rigidity (low high-rate resistance) of the flat surface 10a of the battery case 10 is arranged at the rear Rr part in the array direction X in the high-temperature region A2.

[0073] Also, the distribution between the low-temperature region A1 and the high-temperature region A2 can vary depending on, for example, the number of power storage devices 100, charge and discharge conditions, etc. Therefore, the low-temperature region A1 and the high-temperature region A2 may be provided uniformly in the array direction X as shown in Fig. 8, or may be provided non-uniformly in the array direction X as shown in Fig. 9. In other words, the number of the first power storage devices 110 and the number of the second power storage devices 120 included in the power storage module 500 may be the same or different.

[0074] (Fourth Modification Example) FIG. 10 is a plan view of a power storage module 500d according to the fourth modification example. As shown in FIG. 10, the temperature distribution of the power storage module 500d is here divided more detailedly than in FIG. 6. That is, both end portions in the array direction X (the front F portion and the rear Rr portion in FIG. 7) are low-temperature regions A1 where the temperature is relatively low, the central portion in the array direction X is a high-temperature region A2 where the temperature is relatively high, and between the low-temperature region A1 and the high-temperature region A2 is a medium-temperature region A3 where the temperature is higher than that of the low-temperature region A1 and lower than that of the high-temperature region A2.

[0075] In such a case or the like, as shown in FIG. 10, first power storage devices 110 with relatively low rigidity (high high-rate resistance) of the flat surface 10a of the battery case 10 are arranged at both end portions in the array direction X that are the low-temperature regions A1, and second power storage devices 120 with relatively high rigidity (low high-rate resistance) of the flat surface 10a of the battery case 10 are arranged at the central portion in the array direction X that is the high-temperature region A2. A third power storage device 130, whose rigidity of the flat surface 10a is lower than that of the second power storage device 120 and higher than that of the first power storage device 110, is arranged in the medium-temperature region A3 that is intermediate between the low-temperature region A1 and the high-temperature region A2. In other words, in the order of the high-temperature region A2, the medium-temperature region A3, and the low-temperature region A1, here, a plurality of power storage devices 100 may be arranged so that the rigidity of the flat surface 10a of the battery case 10 gradually decreases from the central portion in the array direction X toward both end portions.

[0076] Note that in FIG. 10, the inside of the power storage module 500 is divided into three temperature regions, but it is of course possible to divide it into four or more temperature regions. By thus finely dividing the inside of the power storage module 500 according to the temperature distribution, the effects of the technology disclosed here are exhibited at a high level, and the high-rate resistance of the entire power storage module 500 can be improved better.

[0077] As described above, specific aspects of the technology disclosed here include those described in the following items. Item 1: A power storage module including a plurality of power storage devices, each of the plurality of power storage devices having a flat rectangular battery case and an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case. In the power storage module, there are a low-temperature region where the temperature relatively decreases and a high-temperature region where the temperature relatively increases when the plurality of power storage devices are charged and discharged. Here, among the plurality of power storage devices, the first power storage device arranged in the low-temperature region has a lower rigidity of the flat surface of the battery case than the second power storage device arranged in the high-temperature region. A power storage module. Item 2: The power storage module according to Item 1, wherein the first power storage device has a thinner thickness of the flat surface than the second power storage device. Item 3: The power storage module according to Item 1 or 2, wherein the thickness of the flat surface of the first power storage device is 0.25 mm to 1.25 mm. Item 4: The power storage module according to any one of Items 1 to 3, wherein the thickness of the flat surface of the second power storage device is 0.5 mm to 2.25 mm. Item 5: In the power storage module, there is a medium-temperature region between the low-temperature region and the high-temperature region, and the temperature in the medium-temperature region is higher than that in the low-temperature region and lower than that in the high-temperature region. Among the plurality of power storage devices, the third power storage device arranged in the medium-temperature region has a higher rigidity of the flat surface than the first power storage device and a lower rigidity of the flat surface than the second power storage device. The power storage module according to any one of Items 1 to 4. Item 6: The power storage module according to any one of Items 1 to 5, wherein the first power storage device and the second power storage device are connected in series. Item 7: A method for manufacturing a power storage module including a plurality of power storage devices, wherein each of the plurality of power storage devices has a flat rectangular battery case and an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case. As the plurality of power storage devices, a first power storage device with a relatively low rigidity of the flat surface of the battery case and a second power storage device with a relatively high rigidity of the flat surface of the battery case are prepared. A temperature distribution prediction step of predicting the temperature distribution in the power storage module when the plurality of power storage devices are charged and discharged, and based on the temperature distribution, arranging the first power storage device in a relatively low-temperature region and the second power storage device in a relatively high-temperature region to construct the power storage module. A method for manufacturing a power storage module including a construction step.

Explanation of Signs

[0078] 10 Battery case 20 Electrode body 22 Positive electrode 24 Negative electrode 100 Power storage device 110 First power storage device 120 Second power storage device 130 Third power storage device 300 Constraint mechanism 400 Cooling device 410 Air-cooling fan 500 Power storage module A1 Low-temperature region A2 High-temperature region A3 Medium-temperature region

Claims

1. A power storage module including a plurality of power storage devices, each of the plurality of power storage devices comprising: a flat rectangular battery case; and an electrode body housed in the battery case and having a flat portion facing the flat surface of the battery case, wherein in the power storage module, when the plurality of power storage devices are charged and discharged, there are a low temperature region where the temperature relatively decreases and a high temperature region where the temperature relatively increases, and among the plurality of power storage devices, a first power storage device disposed in the low temperature region has a lower rigidity of the flat surface of the battery case than a second power storage device disposed in the high temperature region. A power storage module.

2. The power storage module according to claim 1, wherein the first power storage device has a thinner thickness of the flat surface than the second power storage device.

3. The power storage module according to claim 2, wherein the thickness of the flat surface of the first power storage device is 0.25 mm to 1.25 mm.

4. The power storage module according to claim 2, wherein the thickness of the flat surface of the second power storage device is 0.5 mm to 2.25 mm.

5. In the power storage module, there is a medium temperature region between the low temperature region and the high temperature region, where the temperature is higher than that of the low temperature region and lower than that of the high temperature region, and among the plurality of power storage devices, a third power storage device disposed in the medium temperature region has a higher rigidity of the flat surface than the first power storage device and a lower rigidity of the flat surface than the second power storage device. The power storage module according to claim 1.

6. The power storage module according to claim 1, wherein the first power storage device and the second power storage device are connected in series.

7. A method for manufacturing a power storage module including a plurality of power storage devices, each of the plurality of power storage devices comprising: a flat rectangular battery case; and an electrode body housed in the battery case and having a flat portion facing the flat surface of the battery case, wherein a preparation step of preparing, as the plurality of power storage devices, a first power storage device having a relatively low rigidity of the flat surface of the battery case and a second power storage device having a relatively high rigidity of the flat surface of the battery case; a temperature distribution prediction step of predicting a temperature distribution in the power storage module when the plurality of power storage devices are charged and discharged. Based on the temperature distribution, a construction step of constructing the power storage module by arranging the first power storage device in a relatively low-temperature region and arranging the second power storage device in a relatively high-temperature region A method for manufacturing a power storage module, including the above steps.

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