Electric storage module and method for manufacturing the same

Abstract

To provide a power storage module with a novel configuration that can equalize the high-rate resistance of multiple power storage devices.SOLUTION: A power storage module 500 disclosed herein includes a plurality of power storage devices 100. The power storage module 500 includes a low temperature region A1 where the temperature is relatively low and a high temperature region A2 where the temperature is relatively high during charging and discharging of the plurality of power storage devices 100, and among the plurality of power storage devices 100, a first power storage device 110 arranged in the low temperature region A1 has a separator with a higher porosity than a second power storage device 120 arranged in the high temperature region A2.SELECTED DRAWING: Figure 5

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 driving and the like, a power storage module formed by electrically connecting a plurality of power storage devices (single cells) has been widely used. As a related prior art document, Patent Document 1 can be cited.

[0003] For example, Patent Document 1 discloses a power storage module having a plurality of sub-modules and a housing for accommodating 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 restraining member that applies a restraining 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 restraining pressure of the restraining member is relatively lower than that of the other sub-modules. Patent Document 1 describes that by reducing the restraining 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

Patent Document 3

Patent Document 4

Patent Document 5

[0005] In the technology described in the above Patent Document 1, for a plurality of power storage devices included in one cell group, the mutual restraint pressure cannot be made different. Therefore, according to the study by the present inventors, when a temperature distribution occurs in the cell group, it may be difficult to equalize the high-rate resistance of the plurality of power storage devices. In addition, since a restraint member is essential for each cell group, the restraint member is bulky and the volume 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 capable of equalizing the high-rate resistance 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, wherein each of the plurality of power storage devices has a positive electrode, a negative electrode, and a separator, 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. Among the plurality of power storage devices, a first power storage device disposed in the low-temperature region has a higher porosity of the separator than a second power storage device disposed in the high-temperature region.

[0008] Further, according to the present invention, there is provided a method for manufacturing a power storage module including a plurality of power storage devices, each of the plurality of power storage devices having a positive electrode, a negative electrode, and a separator. This manufacturing method includes a preparation step of preparing, as the plurality of power storage devices, a first power storage device having a relatively high porosity of the separator and a second power storage device having a relatively low porosity of the separator; 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 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.

[0009] As a result of various studies by the present inventors, it has been found that a power storage device with a high porosity of the separator is relatively superior in high-rate tolerance compared to a power storage device with a low porosity of the separator. Therefore, in the present invention, a power storage device with a relatively high porosity (superior in high-rate tolerance) 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, it is not necessary to be confined within the framework of a "cell group", so the high-rate tolerance of individual power storage devices 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 efficiency can also be improved.

[0010] Although not particularly related to the technology disclosed herein, Patent Documents 2 to 6 each describe a range of suitable porosity of the separator for a power storage device.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

MODE FOR CARRYING OUT THE INVENTION

[0012] 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 herein and common general knowledge in the relevant field.

[0013] 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".

[0014] [Power Storage Module] FIG. 1 is a perspective view schematically showing a power storage module 500. The power storage module 500 includes, here, 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.

[0015] 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.

[0016] 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 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.

[0017] 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, bind bars, etc. instead of the side plates 320.

[0018] The spacers 200 are respectively 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 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 array direction X may be in contact (direct contact). The spacer 200 preferably includes a porous structure portion through which a fluid (typically a gas such as air) can pass.

[0019] The power storage device 100 is a device capable of repeated charge and discharge. In this specification, the "power storage device" is a concept including 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 disposed 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. However, 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 changed as appropriate.

[0020] 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. 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. Further, 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.

[0021] 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 the spacer 200 here.

[0022] 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 a battery case 10, an electrode body 20, a positive electrode terminal 30, and a negative electrode terminal 40 here. Although illustration is omitted, the power storage device 100 further includes a non-aqueous electrolyte here. 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 non-aqueous electrolyte secondary battery (particularly a lithium ion secondary battery), it is particularly effective to apply the technology disclosed herein.

[0023] 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 here flat, bottomed, and rectangular parallelepiped (square) in shape. 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.

[0024] 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, 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, 19 penetrate the sealing plate 14 in the vertical direction Z.

[0025] The positive electrode terminal 30 is disposed at one end in the long side direction Y of the sealing plate 14 (the left end portion in FIGS. 2 and 3), and the negative electrode terminal 40 is disposed at the other end in the long side direction Y of the sealing plate 14 (the right end portion 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 end portion in FIG. 3). Thereby, the positive electrode terminal 30 and the negative electrode terminal 40 are fixed to the sealing plate 14.

[0026] 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 through 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 through 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.

[0027] 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 by a bus bar or the like.

[0028] FIG. 4 is a schematic diagram showing the configuration of the electrode body 20. 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. Here, the electrode body 20 is disposed inside the exterior body 12 in such a direction that the winding axis WL is substantially parallel to the long side direction Y. However, in other embodiments, the electrode body 20 may be disposed inside the exterior body 12 in such a direction that the winding axis WL is substantially parallel to the vertical direction Z. Further, 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.

[0029] 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 may 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.

[0030] A plurality of positive electrode tabs 22t are provided at one end (the left end in FIG. 4) of the positive electrode current collector 22c in the long side direction Y. The plurality of positive electrode tabs 22t protrude toward one side in the long side direction Y (the left side in FIG. 4). The plurality of positive electrode tabs 22t protrude in the long side direction Y more than the separator 26. Here, the positive electrode tab 22t is 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.

[0031] 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.

[0032] 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.

[0033] The configuration of the negative electrode 24 may be the same as that of the conventional one. 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 in a strip shape. 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.

[0034] A plurality of negative electrode tabs 24t are provided at one end (the right end in FIG. 4) of the negative electrode current collector 24c in the long side direction Y. 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 more in the long side direction Y 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.

[0035] 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 in the long side direction Y of the negative electrode active material layer 24a is preferably the same as or longer than the length Lp in the long side direction Y of the positive electrode active material layer 22a. 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.

[0036] 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 length Ls in the long side direction Y of the separator 26 is preferably the same as or longer than the length Ln in the long side direction Y of the negative electrode active material layer 24a. As the separator 26, for example, a porous sheet (micro-porous membrane) made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. The separator 26 may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). The total thickness (average thickness) of the separator 26 is preferably 5 to 25 μm, and more preferably 10 to 20 μm.

[0037] The separator 26 may be provided with a functional layer (for example, an adhesive layer or a heat resistance layer (Heat Resistance Layer: HRL), etc.) on the surface of the porous sheet made of resin. The heat resistance layer is, for example, a layer containing an inorganic filler such as alumina or boehmite and a binder such as an acrylic resin. The adhesive layer contains a binder such as an acrylic resin and is, for example, a layer that is adhered (for example, pressure-bonded) to the opposing positive electrode 22 or negative electrode 24 by heating or pressing treatment. The configuration of the heat resistance layer and the adhesive layer may be the same as in the prior art.

[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. In other embodiments, the power storage device 100 may include a solid electrolyte instead of the non-aqueous electrolyte.

[0039] FIG. 5 is a plan view schematically showing the power storage module 500 and the cooling device 400. In FIG. 5, detailed illustration of the upper surfaces of the spacer 200 and the power storage device 100 is omitted. As shown in FIG. 5, 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-cooled type cooling device that uses air as a refrigerant here. However, in other embodiments, the cooling device 400 may be a liquid-cooled 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, but it includes, for example, 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 electric motor of the temperature sensor 420 and 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, 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 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-cooled cooling device 400, the power storage device 100 can be cooled at low cost.

[0042] 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 decreases and a high-temperature region A2 where the temperature relatively increases 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 be 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. 5) are more heat dissipative than the central portion, so chain-like heat generation is less likely to occur. Therefore, at both end portions in the arrangement direction X, the temperature tends to be relatively low.

[0043] 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 array direction X, and an exhaust port OP is arranged 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. 5) 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 arranged is most likely to be at the lowest temperature. That is, in this 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 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 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 technology disclosed herein, as the plurality of power storage devices 100, a first power storage device 110 and a second power storage device 120 with different porosity of the separator 26 are used. The first power storage device 110 has a higher porosity of the separator 26 than the second power storage device 120. Although details will be described later, as a result of the study by the present inventors, it has been confirmed that the higher the porosity of the separator 26 of the power storage device 100, the higher the high-rate tolerance. Therefore, in the present embodiment, in the low-temperature region A1 where the temperature is relatively low, here at both ends in the arrangement direction X (the front F part and the rear Rr part in FIG. 5), the first power storage device 110 having a relatively high porosity of the separator 26 (high high-rate tolerance) is arranged. Further, in the high-temperature region A2 where the temperature is relatively high, here at the central part in the arrangement direction X, the second power storage device 120 having a relatively low porosity of the separator 26 (low high-rate tolerance) is arranged.

[0046] According to such a configuration, the high-rate tolerance 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 tolerance of the entire power storage module 500 can be improved. Further, different from 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 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 tolerance 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 restraint mechanisms 300 can be reduced compared to the technology of Patent Document 1, the volume energy density and fuel consumption can also be improved. In addition, the number of parts can be reduced, and the manufacturing cost can be reduced.

[0047] The porosity (%) of the separator 26 can be calculated from the following formula: [1 - (apparent density / true density)] × 100. The true density can be calculated based on the density and content ratio of the components of the separator 26. The apparent density can be calculated from the weight and volume of the separator 26. Note that the porosity of the separator 26 here refers to the porosity of the entire separator 26. For example, when the separator 26 has a functional layer, it is the porosity including the functional layer. The porosity of the separator 26 can be adjusted, for example, by changing the type of resin and manufacturing conditions of the porous sheet (see, for example, Patent Documents 2 to 6). Further, when the separator 26 has a heat-resistant layer as a functional layer, the porosity can also be adjusted by changing the type, particle diameter, and manufacturing conditions of the material (for example, inorganic filler) constituting the heat-resistant layer, or by performing a pressing process after forming the heat-resistant layer on the porous sheet.

[0048] When there are a plurality of the first power storage devices 110 and the second power storage devices 120 as in the present embodiment, it is preferable that the porosity of the separator 26 is relatively higher in any of the plurality of first power storage devices 110 than in the plurality of second power storage devices 120. Also, although not particularly limited, from the viewpoint of balancing the energy density and high-rate tolerance at a high level, in both the first power storage device 110 and the second power storage device 120, the porosity of the separator 26 is preferably in the range of generally 30 to 80%, more preferably in the range of 40 to 70%, even more preferably in the range of 40 to 65%, and, for example, in the range of 45 to 60%. In particular, by setting the porosity to a predetermined value or less, the high-rate charging characteristics of the power storage module 500 can be improved.

[0049] Depending on the temperature distribution within the power storage module 500, in one embodiment, for the first power storage device 110, the porosity of the separator 26 may be generally 50% or more, for example, in the range of 50 to 65%, 53 to 60%. For the second power storage device 120, the porosity of the separator 26 may be generally 40% or more, for example, in the range of 40 to 55%, 45 to 53%. In particular, by setting the porosity to a predetermined value or more, the movement (liquid flow) of the electrolytic solution during high-rate charge and discharge becomes smooth, and the high-rate tolerance can be improved.

[0050] The difference in porosity between the separator 26 of the first power storage device 110 and the separator 26 of the second power storage device 120 is a design matter that is appropriately adjusted depending on, for example, the temperature distribution within the power storage module 500. Therefore, although not particularly limited, when the temperature distributions of the first power storage device 110 and the second power storage device 120 are significantly different, for example, the difference in porosity of the separator 26 between the first power storage device 110 and the second power storage device 120 is preferably 1% or more, more preferably 3% or more, for example, 5% or more. By setting the difference in porosity to a predetermined value or more, the effects of the technology disclosed herein can be more significantly exhibited. The above difference in porosity may be, for example, 20% or less, 10% or less. Thereby, the high-rate charge characteristics of the first power storage device 110 and the second power storage device 120 can be accurately equalized. When there are a plurality of the first power storage devices 110 and the second power storage devices 120, the above difference in porosity may be the difference between the average porosity of the plurality of first power storage devices 110 and the average porosity of the plurality of second power storage devices 120.

[0051] In one embodiment, the first power storage device 110 and the second power storage device 120 have the same properties (such as thickness and configuration) other than the porosity of the separator 26. Among them, it is preferable that the first power storage device 110 and the second power storage device 120 have the same thickness of the separator 26 (manufacturing errors, etc. may be tolerated). Thereby, it becomes easier to equalize the battery performance other than the high-rate tolerance between the first power storage device 110 and the second power storage device 120.

[0052] In one embodiment, the first power storage device 110 and the second power storage device 120 are made of the same type of resin that constitutes the separator 26. This makes it easier to equalize battery performance other than high-rate tolerance between the first power storage device 110 and the second power storage device 120. In a preferred embodiment, in both the first power storage device 110 and the second power storage device 120, the separator 26 is made of a polyolefin resin (e.g., PE and / or PP). This can sufficiently ensure the flexibility of the separator 26. In another preferred embodiment, in both the first power storage device 110 and the second power storage device 120, the separator 26 includes a resin base material layer and a heat-resistant layer formed on the base material layer. This can suppress the heat shrinkage of the separator 26.

[0053] However, in other embodiments, properties of the separator 26 other than the porosity (e.g., thickness and structure), and the type of resin that constitutes the separator 26 may be different between the first power storage device 110 and the second power storage device 120. For example, the thicknesses of the separators 26 of the first power storage device 110 and the second power storage device 120 may be different from each other. More specifically, the thickness of the separator 26 of the first power storage device 110 may be greater or smaller than that of the second power storage device 120. Also, the separator 26 of one of the first power storage device 110 and the second power storage device 120 (e.g., the second power storage device 120) may include a functional layer (e.g., a heat-resistant layer), while the separator 26 of the other (e.g., the first power storage device 110) may not include a functional layer (e.g., a heat-resistant layer). In particular, when the second power storage device 120 disposed in the high-temperature region A2 includes a heat-resistant layer, heat shrinkage of the separator 26 can be suppressed in the high-temperature region A2, contributing to an improvement in the safety of the power storage module 500.

[0054] In one embodiment, it is preferable that the configurations of the first power storage device 110 and the second power storage device 120 other than the separator 26, such as the positive electrode 22, the negative electrode 24, and the composition of the non-aqueous electrolyte, are all the same. This makes it easier to equalize battery performance (e.g., energy density) other than high-rate tolerance between the first power storage device 110 and the second power storage device 120.

[0055] [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 is 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. 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, (Step A) the preparation step may be performed after (Step B) the temperature distribution prediction step, or both steps may be performed simultaneously. Also, the manufacturing method disclosed herein may further include other steps at any stage.

[0056] (In Step A) the preparation step, as the plurality of power storage devices 100, a first power storage device 110 having a relatively high porosity of the separator 26 and a second power storage device 120 having a relatively low porosity of the separator 26 are prepared. In the present embodiment, (Step A) the preparation step includes, in this order: (A-1) an electrode body manufacturing step of manufacturing an electrode body 20; (A-2) a housing step of housing the electrode body 20 and a non-aqueous electrolyte in a battery case 10; and (A-3) a conditioning step.

[0057] (In (A-1) the electrode body manufacturing step, first, at least two types of separators 26 having different porosities are prepared. Specifically, a first separator having a relatively high porosity for the first power storage device 110 and a second separator having a relatively low porosity for the second power storage device 120 are prepared. The first separator and the second separator may be purchased as commercial products or may be manufactured by a conventionally known method. Next, a separately prepared positive electrode 22 and negative electrode 24 are opposed to each other with the first separator or the second separator interposed therebetween and wound. Thereby, an electrode body 20 for the first power storage device 110 and an electrode body 20 for the second power storage device 120 are manufactured.

[0058] (A-2) In the accommodation process, the electrode body 20 produced in the electrode body manufacturing process and the non-aqueous electrolyte as described above are 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 portion 50, and the negative electrode tab group 25 of the electrode body 20 is joined to the negative electrode current collector portion 60. Thereby, the sealing plate 14 and the electrode body 20 are integrated. Next, the sealing plate 14 is placed over the opening 12h of the exterior body 12, and the electrode body 20 is disposed inside the exterior body 12. 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, a non-aqueous electrolyte as described above is prepared and injected into the interior of the battery case 10 through the liquid injection hole 15 of the sealing plate 14. Thereby, a battery assembly for the first power storage device 110 and a battery assembly for the second power storage device 120 are manufactured.

[0059] (A-3) In the conditioning process, the manufactured battery assembly is charged at least once. Preferably, the manufactured 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 having different porosity rates of the separator 26 can be prepared.

[0060] (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 aspect as shown in FIG. 5, 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 (e.g., 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 (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 and 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 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.

[0061] 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 that mimics the power storage module 500 is assembled. Next, the plurality of power storage devices for preliminary tests 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).

[0062] (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 with a relatively high porosity of the separator 26 is arranged in the area separated from the low-temperature region A1, and the second power storage device 120 with a relatively low porosity of the separator 26 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.

[0063] [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 installed in applications that require high output, such as vehicles like passenger cars and trucks. The type of vehicle is not particularly limited. For example, plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), etc. can be mentioned. By installing the power storage module 500 in a moving body such as a vehicle, the fuel consumption (electricity cost) of the moving body can be improved.

[0064] 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.

[0065] In this test example, power storage devices with different separator porosities were constructed to confirm the high-rate tolerance. Specifically, first, separators with the porosities shown in Table 1 were prepared, and power storage devices (lithium-ion secondary batteries, Examples 1 to 5) were fabricated using these separators. Note that as the separators, porous sheets (without functional layers) having a three-layer structure (PP / PE / PP) with PP layers laminated on both sides of the PE layer were used, and the properties of the separators other than the porosity (such as thickness and size) were unified in each example. Also, the configurations other than the separators were 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%, 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.

[0066] 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, followed by a 5-second pause, 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 this charge-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 manner 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 3 is set as 1.00 (reference).

[0067]

Table 1

[0068] As shown in Table 1, the higher the porosity of the separator in the power storage device, the smaller the increase in resistance after the high-rate durability test, that is, the higher the high-rate tolerance. Although not intended to be construed in a particularly limiting sense, the reason for this is that the higher the porosity of the separator, the better the movement (liquid flow) of the electrolyte in the electrode body (especially in the winding axis direction) during high-rate charge and discharge, making it less likely for unevenness in salt concentration to occur, or for any unevenness in salt concentration that does occur to be easily alleviated, thus improving the high-rate tolerance. From the above, it was confirmed from the experimental results that a power storage device with a high porosity of the separator is relatively superior in high-rate tolerance compared to a power storage device with a low porosity of the separator.

[0069] As described above, the preferred embodiments of the present invention have been explained, 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, or to add other modified examples to the above-described embodiments. Also, if its technical features are not described as essential, it is possible to appropriately delete them.

[0070] (1) For example, in the above-described embodiment, in the (process A) preparation process, the power storage device 100 with intentionally different porosities of the separator 26 was manufactured. However, it 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 with varying porosities of the separator 26 within a predetermined acceptable range.

[0071] (2) For example, in the embodiment of FIG. 5 described above, both end portions in the array direction X (the front F portion and the rear Rr portion in FIG. 5) are relatively low-temperature regions A1 with a relatively low temperature, and the central portion 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. Also, in the embodiment of FIG. 5 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. 5, 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. 6 to 9. Note that in FIGS. 6 to 9, the illustration of the cooling device is omitted.

[0072] (First Modification Example) FIG. 6 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 portion in the array direction X. Therefore, although not shown in FIG. 6, 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 portion in the array direction X, and the central portion may be strongly cooled. Then, as shown in FIG. 6, the temperature distribution of the power storage module 500a is, contrary to FIG. 5, such that the central portion in the array direction X becomes a relatively low-temperature region A1, and both end portions in the array direction X (the front F portion and the rear Rr portion in FIG. 6) may become relatively high-temperature regions A2.

[0073] In such cases, as shown in FIG. 6, a first power storage device 110 with a relatively high separator 26 porosity (high high-rate tolerance) 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 low separator 26 porosity (low high-rate tolerance) is arranged at both ends of the array direction X in the high-temperature region A2.

[0074] (Second and third modified examples) FIG. 7 is a plan view of a power storage module 500b according to the second modified example. FIG. 8 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. 5 is powerful and has a high cooling capacity, as shown in FIGS. 7 and 8 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 low-temperature region A1, and the rear Rr part in the array direction X becomes a relatively high-temperature high-temperature region A2.

[0075] In such cases, as shown in FIGS. 7 and 8, a first power storage device 110 with a relatively high separator 26 porosity (high high-rate tolerance) 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 low separator 26 porosity (low high-rate tolerance) is arranged at the rear Rr part in the array direction X in the high-temperature region A2.

[0076] 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. For this reason, the low-temperature region A1 and the high-temperature region A2 may be provided uniformly in the array direction X as shown in FIG. 7, or may be provided non-uniformly in the array direction X as shown in FIG. 8. 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.

[0077] (Fourth Modification Example) FIG. 9 is a plan view of a power storage module 500d according to the fourth modification example. As shown in FIG. 9, the temperature distribution of the power storage module 500d is here divided more detailedly than in FIG. 5. That is, both end portions in the array direction X (the front F portion and the rear Rr portion in FIG. 6) are low-temperature regions A1 with relatively low temperatures, the central portion in the array direction X is a high-temperature region A2 with relatively high temperatures, and between the low-temperature region A1 and the high-temperature region A2 is a medium-temperature region A3 with a temperature higher than that of the low-temperature region A1 and lower than that of the high-temperature region A2.

[0078] In such a case, as shown in FIG. 9, first power storage devices 110 with a relatively high porosity of the separator 26 (high high-rate resistance) are arranged at both end portions in the array direction X, which are the low-temperature regions A1, and second power storage devices 120 with a relatively low porosity of the separator 26 (low high-rate resistance) are arranged at the central portion in the array direction X, which is the high-temperature region A2. A third power storage device 130, which has a higher porosity of the separator 26 than the second power storage device 120 and a lower porosity of the separator 26 than the first power storage device 110, is arranged in the medium-temperature region A3, which is intermediate between the low-temperature region A1 and the high-temperature region A2. In other words, it is advisable to arrange a plurality of power storage devices 100 such that the porosity of the separator 26 increases stepwise from the central portion to both end portions in the array direction X in the order of the high-temperature region A2, the medium-temperature region A3, and the low-temperature region A1.

[0079] Note that in FIG. 9, 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 can be exerted at a high level, and the high-rate resistance of the entire power storage module 500 can be improved better.

[0080] 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, wherein each of the plurality of power storage devices has a positive electrode, a negative electrode, and a separator, 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, and the plurality of power storage devices are arranged such that the porosity of the separator increases stepwise in the order of the high-temperature region, the medium-temperature region, and the low-temperature region. Item 2: 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. The plurality of power storage devices are arranged such that the porosity of the separator increases stepwise in the order of the high-temperature region, the medium-temperature region, and the low-temperature region. The power storage module according to Item 1. Item 3: The first power storage device and the second power storage device both have a separator porosity in the range of 45% or more and 60% or less. The power storage module according to Item 1 or Item 2. Item 4: The first power storage device and the second power storage device have the same separator thickness. The power storage module according to any one of Items 1 to 3. Item 5: The first power storage device and the second power storage device both have a separator made of a polyolefin resin. The power storage module according to any one of Items 1 to 4. Item 6: The first power storage device and the second power storage device are both non-aqueous electrolyte secondary batteries. The power storage module according to any one of Items 1 to 5. Item 7: A method for manufacturing a power storage module including a plurality of power storage devices, each of the plurality of power storage devices having a positive electrode, a negative electrode, and a separator, the method comprising: a preparation step of preparing, as the plurality of power storage devices, a first power storage device having a relatively high porosity of the separator and a second power storage device having a relatively low porosity of the separator; 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 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.

Explanation of Signs

[0081] 10 Battery case 20 Electrode body 22 Positive electrode 24 Negative electrode 26 Separator 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 positive electrode, a negative electrode, and a separator, 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, Among the plurality of power storage devices, the first power storage device disposed in the low-temperature region has a higher porosity of the separator than the second power storage device disposed in the high-temperature region, Power storage module.

2. In the power storage module, between the low-temperature region and the high-temperature region, there is a medium-temperature region where the temperature is higher than that of the low-temperature region and lower than that of the high-temperature region, The plurality of power storage devices are arranged such that the porosity of the separator increases step by step in the order of the high-temperature region, the medium-temperature region, and the low-temperature region, The power storage module according to claim 1.

3. Both the first power storage device and the second power storage device have the porosity of the separator in the range of 45% or more and 60% or less, The power storage module according to claim 1.

4. The first power storage device and the second power storage device have the same thickness of the separator, The power storage module according to any one of claims 1 to 3.

5. Both the first power storage device and the second power storage device have the separator made of a polyolefin resin, The power storage module according to any one of claims 1 to 3.

6. Both the first power storage device and the second power storage device are non-aqueous electrolyte secondary batteries, The power storage module according to any one of claims 1 to 3. Claim 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 positive electrode, a negative electrode, and a separator, comprising: a preparation step of preparing, as the plurality of power storage devices, a first power storage device having a relatively high porosity of the separator and a second power storage device having a relatively low porosity of the separator; 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; 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; and a method for manufacturing a power storage module.

Images