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 power storage devices 100 further includes a buffer member 70 interposed between a flat surface 10a of a battery case 10 and a flat portion 20a of an electrode body 20. Of the plurality of power storage devices 100, a first power storage device 110 disposed in the low-temperature region A1 has the buffer member 70 having a thickness smaller 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 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 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 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 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 where it is likely 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

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1 above, it is not possible to make the mutual 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 tolerance of the plurality of power storage devices. Further, since a restraint member is essential for each cell group, the restraint member takes up space and the volume energy density of the entire power storage module decreases, or 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 capable of equalizing the high-rate tolerance of a plurality of power storage devices and a method for manufacturing the same.

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, an electrode body housed in the battery case and having a flat portion facing the flat surface of the battery case, and a buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body. Further, in this power storage module, when charging and discharging the plurality of power storage devices, 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 smaller total thickness of the electrode body and the buffer member than the second power storage device arranged in the high-temperature region.

[0008] Further, the present invention 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, an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case, and a buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body. And the manufacturing method of 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 thin total thickness of the electrode body and the buffer member and a second power storage device having a relatively thick total thickness of the electrode body and the buffer member, 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 relatively thin total thickness of the electrode body and the buffer member in the battery case is relatively excellent in high-rate tolerance. Therefore, in the present invention, a power storage device having a relatively thin total thickness (high high-rate tolerance) of the electrode body and the buffer member is arranged in a low-temperature region where the high-rate tolerance is likely to decrease. Thereby, the high-rate tolerance of the plurality of power storage devices can be equalized. As a result, the high-rate tolerance of the entire power storage module can be improved. Further, unlike the technology of Patent Document 1, since there is no need to be restricted by the framework of "cell group", the high-rate tolerance of each power storage device can be adjusted flexibly. Furthermore, since the number of restraint members can be reduced compared to the technology of Patent Document 1, the volume energy density and fuel consumption can also be improved.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

BEST MODE FOR CARRYING OUT THE INVENTION

[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. In addition, 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 may 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. The restraint mechanism 300 is one 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 that houses 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 arranged at both ends of the power storage module 500 in the arrangement direction X. The pair of end plates 310 sandwich a plurality of power storage devices 100 and a plurality of spacers 200 in the arrangement 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 arrangement 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, binder bars, etc. instead of the side plates 320.

[0017] The spacers 200 are each arranged here between the plurality of power storage devices 100 in the arrangement direction X. That is, in the arrangement direction X, the power storage devices 100 and the spacers 200 are alternately arranged. However, when the power storage module 500 does not include the spacers 200, the power storage devices 100 adjacent to each other in the arrangement 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 charging and discharging. 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 arrangement 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 shapes, sizes, numbers, etc. of the plurality of power storage devices 100 are not limited to the embodiments disclosed in FIG. 1 and can be changed as appropriate.

[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 for example, it may be in series, parallel, or multi-series multi-parallel. 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 in the arrangement direction X such that the long side walls 12b face each other via a 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 a 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 here has an outer shape that is flat, bottomed, and rectangular parallelepiped (rectangular). 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 outer package 12 having an opening 12h and a sealing plate (lid) 14 that seals the opening 12h. As shown in FIG. 2, the outer package 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 outer package 12 so as to close the opening 12h of the outer package 12. The battery case 10 is integrated by joining (preferably, welding) the sealing plate 14 to the periphery of the opening 12h of the outer package 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 outer package 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-out 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-out 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 ends 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 collector 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 collector 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 arrangement direction X with a bus bar or the like.

[0027] FIG. 4 is a schematic diagram showing the configuration of the electrode body 20. FIG. 5 is a schematic longitudinal sectional view taken along 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 rectangular (typically rectangular) positive electrodes and a plurality of rectangular (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 prior 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] A plurality of positive electrode tabs 22t are provided at one end (the left end in FIG. 4) in the long side direction Y of the positive electrode current collector 22c. The plurality of positive electrode tabs 22t project toward one side in the long side direction Y (the left side in FIG. 4). The plurality of positive electrode tabs 22t project in the long side direction Y beyond 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. The negative electrode 24 here 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. The negative electrode current collector 24c is here a copper foil.

[0033] A plurality of negative electrode tabs 24t are provided at one end (the right end in FIG. 4) in the long side direction Y of the negative electrode current collector 24c. The plurality of negative electrode tabs 24t project toward one side in the long side direction Y (the right side in FIG. 4). The plurality of negative electrode tabs 24t project in the long side direction Y more than the separator 26. The negative electrode tab 24t is a part of the negative electrode current collector 24c here 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] As shown in FIG. 5, the power storage device 100 includes a buffer member 70 interposed between the flat surface 10a of the battery case 10 and the flat portion 20a of the electrode body 20. The buffer member 70 in the present embodiment is a plate-like member inserted between the battery case 10 and the electrode body 20. By this buffer member 70, the high-rate tolerance of the power storage device 100 can be controlled. Specifically, as described above, when constructing the power storage module 500, a restraint pressure is applied to the power storage device 100 by the restraint mechanism 300. At this time, if the buffer member 70 is interposed between the battery case 10 and the electrode body 20, the amount of expansion of the electrode body 20 during high-rate charge and discharge can be controlled. Thereby, the high-rate tolerance of the power storage device 100 can be controlled to a desired state.

[0037] Note that the buffer member 70 is preferably formed of, for example, an insulating resin material. Examples of the material of such a buffer member 70 include polypropylene (PP), polyimide (PI), polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyethylene (PE), and the like. Further, the buffer member 70 preferably has a rigidity of a certain level or more. For example, the rigidity of the buffer member 70 is preferably 0.5 GPa or more, more preferably 1.0 GPa or more, still more preferably 2.0 GPa or more, and particularly preferably 3.0 GPa or more. On the other hand, the upper limit of the rigidity of the buffer member 70 is not particularly limited, and may be 200 GPa or less, 100 GPa or less, or 50 GPa or less. Thereby, the high-rate tolerance of the power storage device 100 can be more appropriately controlled. Note that the "rigidity" in this specification refers to the Young's modulus measured according to JIS K 7161. The rigidity of the buffer member 70 can be controlled by adjusting the material and porosity of the buffer member 70.

[0038] The composition of the non-aqueous electrolyte may be the same as that of the prior art. 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.

[0039] FIG. 6 is a plan view schematically showing the power storage module 500 and the cooling device 400. In FIG. 6, a detailed illustration of the upper surface of the power storage device 100 is omitted. As shown in FIG. 6, the cooling device 400 includes, here, 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.

[0040] 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, and 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.

[0041] 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 the temperature sensor 420, for example, 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, cold 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 the temperature sensor 420, for example, 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 410. According to such an air-cooling type cooling device 400, the power storage device 100 can be cooled at low cost.

[0042] By the way, 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 the plurality of power storage devices 100, and a low-temperature region A1 where the temperature is relatively low and a high-temperature region A2 where the temperature is relatively high may occur. Specifically, when the power storage device 100 generates heat due to charging and discharging, the 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 be relatively high. On the other hand, both ends in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 6) are more heat dissipating than the central portion, so chain-like heat generation is less likely to occur. Therefore, at both ends in the arrangement direction X, the temperature tends to be relatively low.

[0043] Particularly in the present embodiment, an intake port IP through which refrigerant (air) is supplied and an air-cooling fan 410 are disposed on the front F side in the array direction X, and an exhaust port OP is disposed on the rear Rr side in the array direction X. For this reason, both ends in the array direction X tend to be at a low temperature. Therefore, the central portion in the array direction X becomes a high-temperature region A2 with a relatively high temperature, and both ends in the array 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 array direction X where the intake port IP and the air-cooling fan 410 are disposed is most likely to be at the lowest temperature. That is, in the present embodiment, at least the front F side in the array direction X tends to become a low-temperature region A1 with a relatively low temperature.

[0044] As described in, for example, Patent Document 1 and the like, 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 be reduced 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 be accelerated. 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 pulled 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 deteriorates.

[0045] 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, in which the total thicknesses of the electrode body 20 and the buffer member 70 in the battery case 10 are different from each other, are used. Specifically, the buffer member 70 (the first buffer member 70X) of the first power storage device 110 in the present embodiment is thinner than the buffer member 70 (the second buffer member 70Y) of the second power storage device 120. As shown in the test examples described later, the inventors have confirmed that the high-rate resistance increases as the buffer member 70 becomes thinner. Therefore, in the present embodiment, the first power storage device 110 having the first buffer member 70X, which is relatively thin (improving the high-rate resistance), is arranged in the low-temperature region A1 (both end portions in the arrangement direction X) where the temperature is relatively low. Further, the second power storage device 120 having the second buffer member 70Y, which is relatively thick (reducing the 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.

[0046] 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. Further, unlike the technology of Patent Document 1, since there is no need to be restricted by the framework of the "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, there are cases where 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.

[0047] Note that the thickness of the first buffer member 70X may be 2.0 mm or less, 1.5 mm or less, 1.0 mm or less, or 0.5 mm or less. In addition, the thickness of the first buffer member 70X is preferably 0.4 mm or less, more preferably 0.3 mm or less, even more preferably 0.2 mm or less, and particularly preferably 0.1 mm or less. This can increase the high-rate tolerance of the first power storage device 110, so that the high-rate tolerance of the entire power storage module 500 can be leveled at a higher level. On the other hand, the first power storage device 110 in the power storage module disclosed herein may also include a form in which it does not have a plate-shaped buffer member 70 as shown in FIG. 5 (the thickness of the first buffer member 70X is 0 mm). Note that the "thickness of the buffer member" here is the thickness of one of the pair (two sheets) of buffer members inserted with the electrode body 20 interposed therebetween, as shown in FIG. 5.

[0048] On the other hand, the thickness of the second buffer member 70Y may be 0.1 mm or more, preferably 0.2 mm or more, more preferably 0.3 mm or more, even more preferably 0.5 mm or more, and particularly preferably 1.0 mm or more. This makes it easier for the high-rate tolerance of the second power storage device 120 to be lower than that of the first power storage device 110, so that it is easier to level the high-rate tolerance of the entire power storage module 500. On the other hand, the upper limit value of the thickness of the second buffer member 70Y is not particularly limited and may be 5 mm or less, 4 mm or less, or 3 mm or less.

[0049] Also, the thickness ratio of the second buffer member 70Y to the first buffer member 70X is preferably 3 or more, more preferably 4 or more, and particularly preferably 5 or more. This can more appropriately level the high-rate tolerance of the entire power storage module 500. On the other hand, the upper limit value of the thickness ratio of the second buffer member 70Y to the first buffer member 70X is not particularly limited and may be 20 or less, 15 or less, or 10 or less.

[0050] [Method for manufacturing a power storage module] Next, a manufacturing method of a power storage module 500 including a plurality of power storage devices 100 will be described. The power storage module 500 can be manufactured by a manufacturing method including, for example, (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.

[0051] (In Step A) the preparation step, as the plurality of power storage devices 100, a first power storage device 110 with a relatively thin thickness of the buffer member 70 and a second power storage device 120 with a relatively thick thickness of the buffer member 70 are prepared. In the present embodiment, (Step A) the preparation step includes, in this order, (A-1) a buffer member preparation step of preparing the buffer member 70, (A-2) an accommodation step of accommodating the electrode body 20 and the buffer member 70 in the battery case 10, and (A-3) a conditioning step.

[0052] (In (A-1) the buffer member preparation step, the buffer member 70 to be used for each of the first power storage device 110 and the second power storage device 120 is prepared. For example, a relatively thin first buffer member 70X for the first power storage device 110 and a relatively thick second buffer member 70Y for the second power storage device 120 are prepared. Also, a plurality of buffer members 70 having the same thickness may be prepared, and the number of buffer members 70 used for each of the first power storage device 110 and the second power storage device 120 may be made different. Further, when manufacturing the first power storage device 110 without the buffer member 70, it is not necessary to prepare the first buffer member 70X. Note that the buffer member 70 may be purchased as a commercially available product or may be manufactured by a conventionally known method.

[0053] (A-2) In the accommodation process, the separately prepared electrode body 20 is accommodated in the battery case 10 together with the buffer member 70. 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. Next, the electrode body 20 and the buffer member 70 are accommodated inside the battery case 10. At this time, it is preferable to attach the buffer member 70 to the flat portion 20a of the electrode body 20. In the production of the first power storage device 110, the first buffer member 70X with a small thickness is used. On the other hand, in the production of the second power storage device 120, the second buffer member 70Y with a large thickness is used. 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 and the buffer member 70 are 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 from the liquid injection hole 15 of the sealing plate 14. Thereby, a precursor (battery assembly) of the power storage device 100 is produced. In the produced battery assembly, as shown in FIG. 5, the flat surface 10a of the battery case 10 and the flat portion 20a of the electrode body 20 face each other, and the buffer member 70 is interposed between the flat surface 10a of the battery case 10 and the flat portion 20a of the electrode body 20.

[0054] (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 of the buffer member 70 can be prepared.

[0055] (Project B) In the temperature distribution prediction process, the temperature distribution within the power storage module 500 when a plurality of power storage devices 100 are charged and discharged is predicted. That is, for example, in the aspect 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 change 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 of the low temperature region A1 (the length in the array direction X) can also change depending on, for example, the number of power storage devices 100, the charge and discharge conditions, etc. Therefore, it is preferable to predict the temperature distribution within the power storage module 500 during charge and discharge by means of a preliminary experiment or a simulation using commercially available analysis software. In particular, it is preferable to construct a power storage module for preliminary testing that mimics 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.

[0056] In a preferred embodiment, first, a plurality of power storage devices for preliminary testing 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 testing, a power storage module for preliminary testing that mimics the power storage module 500 is assembled. Next, the plurality of power storage devices for preliminary testing are actually charged and discharged (preferably at a high rate), and the temperature distribution at this time is acquired. The charge and 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 divided, for example, into a low temperature region A1 and a high temperature region A2 (for example, divided into two parts).

[0057] (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 buffer member 70X is arranged in the region separated from the low-temperature region A1. On the other hand, the second power storage device 120 having the second buffer member 70Y is arranged in the region 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.

[0058] [Use of the power storage module] The power storage module 500 can be used for various purposes. 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. For example, plug-in hybrid electric vehicles (PHEV), hybrid electric vehicles (HEV), battery electric vehicles (BEV), etc. can be mentioned. 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.

[0059] Hereinafter, several test examples related to the present invention will be described, but the present invention is not intended to be limited to such test examples.

[0060] In this test example, a plurality of power storage devices with different thicknesses of the buffer member were constructed, and the high-rate tolerance of each was confirmed. Specifically, first, power storage devices (lithium-ion secondary batteries, Examples 1 to 4) were fabricated with a buffer member interposed between the battery case and the electrode body. Note that a polypropylene sheet was used as the buffer member. And as shown in Table 1, in this test example, the thickness of the buffer member was varied among Examples 1 to 4. Note that the "thickness of the buffer member" in Table 1 is the ratio with the thickness of the buffer member in Example 1 (one side: 0.1 mm) taken as 1 (reference value). Also, the configurations other than the buffer member (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.

[0061] 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 paused for 5 seconds, and then constant current discharging was performed at a discharging rate of 10 A for 150 seconds and then paused for 5 seconds. One cycle of charge and discharge was defined as such, and this was repeated 1000 times to conduct a high-rate durability test. And 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).

[0062]

Table 1

[0063] As shown in Table 1, it was confirmed that as the thickness of the buffer member 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 thin buffer member is relatively superior in high-rate tolerance compared to a power storage device having a thick buffer member.

[0064] 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 also 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.

[0065] (1) For example, in the above-described embodiment, the thickness of the buffer member 70 is made different between the first power storage device 110 and the second power storage device 120. However, the technology disclosed herein only needs to relatively reduce the total thickness of the electrode body 20 and the buffer member 70 in the first power storage device 110, and is not limited to the above-described embodiment. For example, after making the thickness of the buffer member 70 constant, the thickness of the electrode body 20 may be made different between the first power storage device 110 and the second power storage device 120. Further, the thicknesses of both the buffer member 70 and the electrode body 20 may be made different from each other. Considering the mechanism of controlling the high-rate resistance by adjusting the degree of expansion of the electrode body 20 during high-rate charge and discharge, it is understood that the high-rate resistance can be leveled in any of the above cases.

[0066] (2) For example, in the above-described embodiment, in the (step A) preparation step, a power storage device 100 was manufactured in which the total thickness (the thickness of the buffer member 70) of the electrode body 20 and the buffer member 70 was intentionally made different. However, the embodiments of the present invention are 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 total thickness of the electrode body 20 and the buffer member 70 varies, within a predetermined acceptable range.

[0067] 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 power storage devices such as lithium-ion secondary batteries, identification information may be attached 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, date of manufacture, etc., information regarding the structure of the electrode body and the buffer member.

[0068] In this case, in the (process A) preparation process, (1-a) an acquisition process of reading the identification information attached to a large number of recovered power storage devices respectively to obtain information regarding the total thickness of the electrode body and the buffer member, and (1-b) a sorting process of sorting out a first power storage device 110 having a relatively thin total thickness of the electrode body and the buffer member and a second power storage device 120 having a relatively thick total thickness of the electrode body and the buffer member from among the plurality of power storage devices may be included. Such a manufacturing method of the power storage module can also be grasped as a reuse method (reuse method) of the power storage device. Note that in this specification, the "optical symbol" is a general term for information media that store information by a combination of a portion with high optical reflectivity and a portion with low optical reflectivity, and is a concept including 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.).

[0069] (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 relatively low temperatures, and the central part in the array direction X is a relatively high-temperature region A2 with a relatively high temperature. However, it is not limited to this. As described above, the temperature distribution within 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. Further, 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 furthermore, 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 complex, 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.

[0070] (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.

[0071] In such cases, as shown in FIG. 7, a first power storage device 110 with a relatively thin total thickness of the electrode body 20 and the buffer member 70 (high high-rate resistance) is arranged at the center of the array direction X in the low-temperature region A1, and a second power storage device 120 with a relatively thick total thickness of the electrode body 20 and the buffer member 70 (low high-rate resistance) is arranged at both ends of the array direction X in the high-temperature region A2.

[0072] (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 a high cooling capacity, as shown in FIGS. 8 and 9 respectively, the temperature distribution in the power storage modules 500b and 500c can be such that the front F part in the array direction X becomes a low-temperature region A1 with a relatively low temperature, and the rear Rr part in the array direction X becomes a high-temperature region A2 with a relatively high temperature.

[0073] In such cases, as shown in FIGS. 8 and 9, a first power storage device 110 with a relatively thin total thickness of the electrode body 20 and the buffer member 70 (high high-rate resistance) 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 a relatively thick total thickness of the electrode body 20 and the buffer member 70 (low high-rate resistance) is arranged at the rear Rr part in the array direction X in the high-temperature region A2.

[0074] 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 first power storage devices 110 and the number of second power storage devices 120 included in the power storage module 500 may be the same or different.

[0075] (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 in more detail than in FIG. 6. That is, both end portions in the array direction X (front F portion and 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.

[0076] In such a case or the like, as shown in FIG. 10, first power storage devices 110 with a relatively thin total thickness of the electrode body 20 and the buffer member 70 (high high-rate tolerance) 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 a relatively thick total thickness of the electrode body 20 and the buffer member 70 (low high-rate tolerance) 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 total thickness is thinner than that of the second power storage device 120 and thicker 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 such that the total thickness of the electrode body 20 and the buffer member 70 gradually decreases from the central portion in the array direction X toward both end portions.

[0077] 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 herein can be exerted at a high level, and the high-rate tolerance of the entire power storage module 500 can be improved better.

[0078] (4) For example, in the above-described embodiment, it is used as the plate-shaped buffer member 70 (see FIG. 5). However, the buffer member 70 only needs to have a portion interposed between the flat surface 10a of the battery case 10 and the flat portion 20a of the electrode body 20, and is not limited to a plate-shaped member. For example, the buffer member 70 may be a box-shaped member as shown in FIG. 11. This box-shaped buffer member 70 includes a bottom surface portion 72, a pair of front surface portions 74, and a pair of side surface portions 76. First, the bottom surface portion 72 is a plate-shaped member having a rectangular plane. Next, each of the pair of front surface portions 74 is a rectangular plate-shaped member extending upward U in the height direction Z from the long side of the bottom surface portion 72. And each of the pair of side surface portions 76 is a rectangular plate-shaped member extending upward U in the height direction Z from the short side of the bottom surface portion 72. When the box-shaped buffer member 70 is housed inside the battery case 10, the front surface portion 74 of the box-shaped buffer member 70 faces the flat surface 10a of the battery case 10. Also, the bottom surface portion 72 faces the bottom of the battery case 10 (the bottom wall 12a of the exterior body 12). Further, the side surface portion 76 faces the side surface of the battery case 10 (the short side wall 12c of the exterior body 12). And when the electrode body 20 is housed inside this box-shaped buffer member 70, a part (front surface portion 74) of the buffer member 70 is interposed between the flat surface 10a of the battery case 10 and the flat portion 20a of the electrode body 20. At this time, by adjusting the thickness of the front surface portion 74, the high-rate tolerance of the power storage device 100 can be controlled. Note that the buffer member in the technology disclosed here is not limited to either the plate-shaped buffer member shown in FIG. 5 or the box-shaped buffer member shown in FIG. 11. That is, in the technology disclosed here, both the plate-shaped buffer member and the box-shaped buffer member may be used in combination. In this case, the plate-shaped buffer member may be interposed between the box-shaped buffer member and the electrode body and / or between the box-shaped buffer member and the battery case.

[0079] 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, an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case, and a buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body. 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 during charging and discharging of the plurality of power storage devices. Here, among the plurality of power storage devices, the first power storage device disposed in the low-temperature region has a smaller total thickness of the electrode body and the buffer member than the second power storage device disposed in the high-temperature region. Power storage module. Item 2: The power storage module according to Item 1, wherein the first power storage device has a thinner buffer member than the second power storage device. Item 3: The power storage module according to Item 1 or 2, wherein the thickness of the buffer member of the first power storage device is 0 mm to 2.0 mm. Item 4: The power storage module according to any one of Items 1 to 3, wherein the thickness of the buffer member of the second power storage device is 0.1 mm to 3.0 mm. Item 5: In the power storage module, there is a medium-temperature region having a temperature higher than that of the low-temperature region and lower than that of the high-temperature region between the low-temperature region and the high-temperature region. Among the plurality of power storage devices, the third power storage device disposed in the medium-temperature region has a larger total thickness of the electrode body and the buffer member than the first power storage device and a smaller total thickness of the electrode body and the buffer member than the second power storage device. 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: The power storage module according to any one of Items 1 to 6, wherein the buffer member is a plate-shaped buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body. Item 8: The buffer member is a box-shaped buffer member including a front surface portion facing the flat surface of the battery case, a bottom surface portion facing the bottom of the battery case, and a side surface portion facing the side surface of the battery case, and the electrode body is accommodated inside the box-shaped buffer member. The power storage module according to any one of Items 1 to 7. Item 9: A method for manufacturing a power storage module including a plurality of power storage devices, wherein each of the plurality of power storage devices includes a flat rectangular battery case, an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case, and a buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body. As the plurality of power storage devices, a first power storage device having a relatively thin total thickness of the electrode body and the buffer member, and a second power storage device having a relatively thick total thickness of the electrode body and the buffer member are prepared. A preparation step, 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, and based on the temperature distribution, arranging the first power storage device in a low temperature region where the temperature is relatively low, and arranging the second power storage device in a high temperature region where the temperature is relatively high to construct the power storage module. A method for manufacturing a power storage module including a construction step.

Explanation of Signs

[0080] 10 Battery case 20 Electrode body 22 Positive electrode 24 Negative electrode 70 Buffer member 100 Power storage device 110 First power storage device 120 Second power storage device 130 Third power storage device 300 Restraint 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 has a flat rectangular battery case, an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case, and a buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body, and 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, wherein, among the plurality of power storage devices, a first power storage device disposed in the low temperature region has a smaller total thickness of the electrode body and the buffer member 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 buffer member than the second power storage device.

3. The power storage module according to claim 2, wherein the thickness of the buffer member of the first power storage device is 0 mm to 2.0 mm.

4. The power storage module according to claim 2, wherein the thickness of the buffer member of the second power storage device is 0.1 mm to 3.0 mm.

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 is higher than that of the low temperature region and lower than that of the high temperature region. Among the plurality of power storage devices, a third power storage device disposed in the medium temperature region has a larger total thickness of the electrode body and the buffer member than the first power storage device and a smaller total thickness of the electrode body and the buffer member 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. The power storage module according to any one of claims 1 to 6, wherein the buffer member is a plate-shaped buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body.

8. The buffer member has a front portion facing the flat surface of the battery case, a bottom portion facing the bottom of the battery case, and side portions facing the sides of the battery case, and is a box-shaped buffer member, and the electrode body is accommodated inside the box-shaped buffer member. The power storage module according to any one of claims 1 to 6.

9. A method for manufacturing a power storage module including a plurality of power storage devices, ​ Each of the plurality of power storage devices includes: a flat rectangular battery case; an electrode body accommodated in the battery case and having a flat portion facing the flat surface of the battery case; a buffer member interposed between the flat surface of the battery case and the flat portion of the electrode body; and has a preparation step of preparing, as the plurality of power storage devices, a first power storage device having a relatively thin total thickness of the electrode body and the buffer member, and a second power storage device having a relatively thick total thickness of the electrode body and the buffer member; 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; a construction step of constructing the power storage module by arranging the first power storage device in a relatively low-temperature region and the second power storage device in a relatively high-temperature region based on the temperature distribution; A method for manufacturing a power storage module, comprising the steps of:

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