Energy 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 higher LiFSI ratio 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 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 restraining member that applies a restraining pressure in the arrangement direction to restrain the cell group. And, in the housing, there is a region 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 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 tolerance is likely to decrease in this way, the high-rate tolerance (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 Patent Document 1 above, it is not possible to make the constraint pressures of multiple energy storage devices included in a single cell group different from each other. Therefore, according to the inventors' studies, when a temperature distribution occurs within the cell group, it is difficult to equalize the high-rate resistance of multiple energy storage devices. In addition, since a constraint member is required for each cell group, the constraint members become bulky, which may reduce the overall volumetric energy density of the energy storage module, or, for example, when the energy storage module is mounted on a moving object such as a vehicle, the weight may increase, potentially worsening fuel efficiency.

[0006] The present invention has been made in view of the above circumstances, and its main objective is to provide a novel energy storage module and a method for manufacturing the same that can equalize the high-rate resistance of multiple energy storage devices. [Means for solving the problem]

[0007] The present invention provides an energy storage module comprising a plurality of energy storage devices, each of which has an electrode body and a non-aqueous electrolyte, the non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte salt, and within the energy storage module there is a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high when the plurality of energy storage devices are charged and discharged, and here, if the molar ratio of lithium bis(fluorosulfonyl)imide in the electrolyte salt is defined as the LiFSI ratio, then the first energy storage device located in the low-temperature region has a higher LiFSI ratio than the second energy storage device located in the high-temperature region.

[0008] Furthermore, the present invention provides a method for manufacturing an energy storage module comprising a plurality of energy storage devices, each of which comprises an electrode body and a non-aqueous electrolyte, the non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte salt. This manufacturing method includes a preparation step of preparing a plurality of energy storage devices, where the molar ratio of lithium bis(fluorosulfonyl)imide in the electrolyte salt is defined as the LiFSI ratio, a first energy storage device having a relatively high LiFSI ratio, and a second energy storage device having a relatively low LiFSI ratio; a temperature distribution prediction step of predicting the temperature distribution within the energy storage module when the plurality of energy storage devices are charged and discharged; and a construction step of constructing the energy storage module by arranging the first energy storage device in a relatively low-temperature region and the second energy storage device in a relatively high-temperature region based on the temperature distribution.

[0009] Through various studies conducted by the inventors, it was found that energy storage devices with a high LiFSI ratio exhibit relatively superior high-rate tolerance compared to energy storage devices with a low LiFSI ratio. Therefore, in this invention, energy storage devices with a relatively high LiFSI ratio (high high-rate tolerance) are placed in the low-temperature region where high-rate tolerance tends to decrease. This allows for the equalization of the high-rate tolerance of multiple energy storage devices, thereby improving the high-rate tolerance of the entire energy storage module. Furthermore, unlike the technology described in Patent Document 1, there is no need to be constrained by the framework of "cell groups," allowing for flexible adjustment of the high-rate tolerance of individual energy storage devices. In addition, since the number of restraining members can be reduced compared to the technology described in Patent Document 1, volumetric energy density and fuel efficiency can also be improved.

[0010] Although not particularly related to the technology disclosed herein, Patent Documents 2 to 5 describe ranges of LiFSI concentrations or ratios suitable for energy storage devices. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic perspective view showing an energy storage module according to one embodiment. [Figure 2] Figure 2 is a schematic perspective view showing the secondary battery shown in Figure 1. [Figure 3] Figure 3 is a schematic longitudinal cross-sectional view along the line III-III in Figure 2. [Figure 4] Figure 4 is a schematic diagram showing the configuration of the electrode body in Figure 3. [Figure 5] Figure 5 is a schematic plan view showing the energy storage module and cooling device shown in Figure 1. [Figure 6] Figure 6 is a schematic plan view showing a power storage module according to the first modified example. [Figure 7] Figure 7 is a schematic plan view showing a power storage module according to the second modified example. [Figure 8] Figure 8 is a schematic plan view showing a power storage module according to the third modified example. [Figure 9] Figure 9 is a schematic plan view showing a power storage module according to the fourth modified example. [Modes 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 herein but necessary for carrying out the present invention (for example, the general configuration and manufacturing process of energy storage modules and devices that do not characterize the present invention) can be understood as design matters of those skilled in the art based on the prior art. The energy storage modules disclosed herein can be carried out based on the content disclosed herein and common technical knowledge in the art.

[0013] In the following drawings, the same reference numerals are used for members and parts that perform the same function, and redundant explanations may be omitted or simplified. Furthermore, in this specification, the notation "A~B" indicating a range encompasses not only the meaning of A or greater and B or less, but also the meanings of "preferably greater than A" and "preferably less than B".

[0014] [Energy 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 can 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 for accommodating a plurality of power storage devices 100. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal.

[0017] A pair of end plates 310 are positioned at both ends of the energy storage module 500 in the array direction X. The pair of end plates 310 sandwich a plurality of energy 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, for example, so that the restraining load is about 10 to 15 kN. This applies a uniform restraining load to the plurality of energy storage devices 100 from the array direction X, and the plurality of energy storage devices 100 are held together as a single unit. However, the configuration of the restraining mechanism is not limited to this. The restraining mechanism 300 may include, for example, a plurality of restraining bands or binding bars instead of the side plates 320.

[0018] In this configuration, the spacers 200 are positioned between each of the multiple energy storage devices 100 in the array direction X. That is, in the array direction X, the energy storage devices 100 and the spacers 200 are arranged alternately. However, if the energy storage module 500 does not include spacers 200, adjacent energy storage devices 100 in the array direction X may be in direct contact with each other. It is preferable that the spacers 200 include a porous structure portion through which a fluid (typically a gas such as air) can pass.

[0019] The energy storage device 100 is a device capable of repeated charging and discharging. In this specification, "energy storage device" is a concept that encompasses 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. Here, the multiple energy storage devices 100 are arranged between a pair of end plates 310 along the arrangement direction X (in other words, the thickness direction X of the energy storage devices 100). It is preferable that the multiple energy storage devices 100 are constrained by the restraint mechanism 300. The shape, size, number, etc. of the multiple energy storage devices 100 are not limited to the embodiment disclosed in Figure 1 and can be changed as appropriate.

[0020] Although not shown in the diagrams here, when the energy storage module 500 is in use, multiple energy storage devices 100 are electrically connected to each other by conductive members such as busbars. The connection method is not particularly limited and may be series, parallel, or multiple series and multiple parallel. In one preferred embodiment, multiple energy storage devices 100 are connected in series. This allows for a suitable improvement in output characteristics to a level suitable for use in mobile devices such as vehicles. Furthermore, in the case of series connection, performance degradation of some energy storage devices 100 tends to lead to performance degradation of the entire energy storage module 500. Therefore, applying the technology disclosed herein is particularly effective.

[0021] Figure 2 is a perspective view of the energy storage device 100. As can be seen from Figures 1 and 2, the multiple energy storage devices 100 are all flattened rectangular in shape and are identical in this respect. The multiple energy storage devices 100 are arranged so that their long side walls 12b, which will be described later, are parallel to each other. The multiple energy storage devices 100 are arranged in the arrangement direction X with their long side walls 12b facing each other via spacers 200.

[0022] Figure 3 is a schematic longitudinal cross-sectional view along the line III-III in Figure 2. As shown in Figure 3, the energy storage device 100 here comprises 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 energy 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 energy storage device 100 is typically a non-aqueous electrolyte secondary battery, and here it is a lithium-ion secondary battery. When the energy storage device 100 is a lithium-ion secondary battery, the application of the technology disclosed herein is particularly effective.

[0023] The battery case 10 is a container for housing the electrode body 20 and the non-aqueous electrolyte. As shown in Figure 2, the battery case 10 has a flattened, bottomed rectangular parallelepiped (square) shape. The material of the battery case 10 can be the same as that conventionally used, and there are no particular restrictions. The battery case 10 can be made of, for example, aluminum, aluminum alloy, iron, iron alloy, etc. As shown in Figure 3, the battery case 10 comprises an outer casing 12 having an opening 12h and a sealing plate (lid) 14 that seals the opening 12h. As shown in Figure 2, the outer casing 12 comprises a substantially rectangular bottom wall 12a having long and short sides, 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 walls 12b are flat.

[0024] The sealing plate 14 is a plate-shaped member. The sealing plate 14 is substantially rectangular in shape. As shown in Figure 3, the sealing plate 14 is attached to the outer casing 12 so as to close the opening 12h of the outer casing 12. The battery case 10 is integrated by joining (preferably by welding) the sealing plate 14 to the periphery of the opening 12h of the outer casing 12. The battery case 10 is airtightly sealed. The sealing plate 14 is provided with an electrolyte injection hole 15 and two terminal lead-out holes 18 and 19. The electrolyte injection hole 15 is for injecting a non-aqueous electrolyte after the sealing plate 14 has been assembled to the outer casing 12. The electrolyte 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.

[0025] The positive terminal 30 is located at one end of the sealing plate 14 in the long side direction Y (the left end in Figures 2 and 3), and the negative terminal 40 is located at the other end of the sealing plate 14 in the long side direction Y (the right end in Figures 2 and 3). As shown in Figure 3, the positive terminal 30 and the negative terminal 40 extend from the inside to the outside of the sealing plate 14 through terminal lead holes 18 and 19, respectively. The positive terminal 30 and the negative terminal 40 are crimped to the peripheral portion surrounding the terminal lead holes 18 and 19 of the sealing plate 14 by a crimping process. Crimped portions 30c and 40c are formed at the ends of the outer casing 12 side of the positive terminal 30 and the negative terminal 40 (the lower ends in Figure 3). In this way, the positive terminal 30 and the negative terminal 40 are fixed to the sealing plate 14.

[0026] As shown in Figure 3, the positive terminal 30 is electrically connected to the group of positive tabs 23 of the electrode body 20 via the positive current collector 50 inside the casing 12. The positive terminal 30 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90. The negative terminal 40 is electrically connected to the group of negative tabs 25 of the electrode body 20 via the negative current collector 60 inside the casing 12. The negative terminal 40 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90.

[0027] As shown in Figures 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 busbars are attached to electrically connect a plurality of energy storage devices 100 to each other. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external insulating member 92. The energy storage module 500 is connected in series, for example, by electrically connecting the positive electrode external conductive member 32 of one energy storage device 100 and the negative electrode external conductive member 42 of the other energy storage device 100, which are adjacent to each other in the array direction X, with a busbar or the like.

[0028] Figure 4 is a schematic diagram showing the configuration of the electrode body 20. As shown in Figure 4, the electrode body 20 has a positive electrode 22, a negative electrode 24, and a separator 26. In this embodiment, 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 stacked via a strip-shaped separator 26 and wound around a winding axis WL. The electrode body 20 has a flattened outer shape. In this embodiment, the electrode body 20 is arranged inside the outer casing 12 with the winding axis WL oriented substantially parallel to the long side direction Y. However, in other embodiments, the electrode body 20 may be arranged inside the outer casing 12 with the winding axis WL oriented substantially parallel to the vertical direction Z. Alternatively, the electrode body 20 may be a laminated electrode body in which multiple rectangular positive electrodes and multiple rectangular negative electrodes are stacked in an insulated state.

[0029] The configuration of the positive electrode 22 may be the same as in the conventional design. Here, the positive electrode 22 comprises a positive electrode current collector 22c and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed to 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 of metal foil. Here, the positive electrode current collector 22c is aluminum foil.

[0030] Multiple positive electrode tabs 22t are provided at one end of the positive electrode current collector 22c in the long side direction Y (the left end in Figure 4). The multiple positive electrode tabs 22t protrude toward one side in the long side direction Y (the left side in Figure 4). The multiple positive electrode tabs 22t protrude further in the long side direction Y than the separator 26. The positive electrode tabs 22t are here part of the positive electrode current collector 22c and are made of metal foil (aluminum foil). The multiple positive electrode tabs 22t are stacked at one end in the long side direction Y (the left end in Figure 4) to form a group of positive electrode tabs 23. The group of positive electrode tabs 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 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 intercepting and releasing charge carriers. Examples of positive electrode active materials include lithium transition metal composite oxides. The positive electrode active material layer 22a may also contain various additive components other than the positive electrode active material, such as binders and conductive materials.

[0032] The positive electrode protective layer 22p is provided at the boundary 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 (e.g., alumina). The positive electrode protective layer 22p may also contain optional components other than the inorganic filler, such as conductive materials, binders, various additives, etc.

[0033] The configuration of the negative electrode 24 may be the same as in the conventional design. Here, the negative electrode 24 has a negative electrode current collector 24c and a negative electrode active material layer 24a fixed to 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 of metal foil. Here, the negative electrode current collector 24c is copper foil.

[0034] Multiple negative electrode tabs 24t are provided at one end of the negative electrode current collector 24c in the long side direction Y (the right end in Figure 4). The multiple negative electrode tabs 24t protrude toward one side in the long side direction Y (the right side in Figure 4). The multiple negative electrode tabs 24t protrude further in the long side direction Y than the separator 26. The negative electrode tabs 24t are here part of the negative electrode current collector 24c and are made of metal foil (copper foil). The multiple negative electrode tabs 24t are stacked at one end in the long side direction Y (the right end in Figure 4) to form a negative electrode tab group 25. The negative electrode tab group 25 is provided in a position symmetrical 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 collector 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. Preferably, the length Ln of the negative electrode active material layer 24a in the longitudinal direction Y is the same as or longer than the length Lp of the positive electrode active material layer 22a in the longitudinal direction Y. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly intercalating and releasing charge carriers. Examples of negative electrode active material include carbon materials such as graphite. The negative electrode active material layer 24a may also contain optional components other than the negative electrode active material, such as binders, thickeners, dispersants, and other additive components.

[0036] The separator 26 is positioned between the positive electrode 22 and the negative electrode 24. The separator 26 is an insulating member between the positive electrode 22 and the negative electrode 24. The configuration of the separator 26 may be the same as in the conventional design. Preferably, the length Ls of the long side Y of the separator 26 is the same as or longer than the length Ln of the long side Y of the negative electrode active material layer 24a. As the separator 26, for example, a porous sheet (microporous membrane) made of polyolefin resin such as polyethylene (PE) or polypropylene (PP) is preferred. The separator 26 may have a functional layer (for example, an adhesive layer or a heat-resistant layer) on the surface of the porous sheet.

[0037] A non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt (supporting salt). Examples of non-aqueous solvents include various organic solvents commonly used in the electrolytes of lithium-ion secondary batteries, specifically carbonates, esters, ethers, nitriles, sulfones, lactones, etc. These can be used individually or in combination of two or more. In particular, it is preferable to include carbonates and esters, more preferable to include carbonates, and especially preferable to consist of carbonates (the non-aqueous solvent is a carbonate). In this specification, "carbonates" refers to all compounds that contain at least one carbonate structure (-O-CO-O-) in their molecule.

[0038] Specific examples of carbonates include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and fluoroethylene carbonate; and linear carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), and difluoroethylene carbonate (DFEC). In particular, from the viewpoint of improving ionic conductivity and reducing the viscosity of the non-aqueous electrolyte, it is preferable that the non-aqueous solvent contains both a cyclic carbonate (e.g., EC) and a linear carbonate (e.g., DMC and / or EMC). Furthermore, the proportion of the cyclic solvent (e.g., cyclic carbonate) in the total non-aqueous solvent is preferably 50% by volume or less, for example, 10-50% by volume or 20-30% by volume.

[0039] Specific examples of esters include, for example, linear esters such as methyl acetate (MA), ethyl acetate, n-propyl acetate, and n-butyl acetate. Specific examples of ethers include, for example, linear ethers such as diethyl ether.

[0040] Examples of electrolyte salts include various lithium salts commonly used as electrolytes in lithium-ion secondary batteries, specifically, lithium hexafluoride phosphate (LiPF6); lithium tetrafluoroborate (LiBF4); lithium bis(fluorosulfonyl)imide (LiFSI; LiN(SO2F)2); lithium bis(trifluoromethanesulfonyl)imide (LiTFSI; LiN(SO2CF3)2); and perfluoroalkylsulfonylimide compounds such as lithium bis(pentafluoroethanesulfonyl)imide. These can be used individually or in combination of two or more. Among these, the inclusion of LiFSI and LiPF6 is preferred. It is more preferable that the electrolyte salt consists of LiFSI and / or LiPF6. Compared to LiTFSI, which is another perfluoroalkylsulfonylimide compound, LiFSI has a relatively lower anion bulk. Furthermore, because Li dissociates easily in LiFSI and has low viscosity, combining it with LiPF6, for example, can specifically improve high-rate resistance.

[0041] The non-aqueous electrolyte may contain additional additives as needed. Examples of additives include gas generators such as biphenyl (BP) and cyclohexylbenzene (CHB); and film-forming agents such as oxalate complex compounds containing boron and / or phosphorus atoms. While the non-aqueous electrolyte is typically liquid, it may also be gel-like.

[0042] Figure 5 is a schematic plan view showing the energy storage module 500 and the cooling device 400. Note that Figure 5 omits detailed illustrations of the spacer 200 and the top surface of the energy storage device 100. As shown in Figure 5, the cooling device 400 here comprises an air intake IP, an exhaust port OP, an air-cooling fan 410, a temperature sensor 420, and a control device 430. The cooling device 400 here is an air-cooled type cooling device that uses air as a refrigerant. However, in other embodiments, the cooling device 400 may be a liquid-cooled type cooling device that uses a liquid refrigerant.

[0043] In this embodiment, the intake port IP is provided on one side (front F side) of the arrangement direction X of the energy storage module 500. The exhaust port OP is provided on the other side (rear Rr side) of the arrangement direction X. The cooling fan 410 is attached to the intake port IP. The cooling fan 410 is configured to blow air into the intake port IP. The configuration of the cooling fan 410 is not limited, but for example it may include an electric motor (not shown). The temperature sensor 420 is located in the center of the energy storage module 500 in the XY plane. The temperature sensor 420 is, for example, a thermocouple or a thermistor.

[0044] The control device 430 is electrically connected to the temperature sensor 420 and the electric motor of the cooling fan 410. When the control device 430 detects, for example, that the temperature inside the energy storage module 500 has risen above a predetermined first temperature, it activates the cooling fan 410. This allows cool air from outside the energy storage module 500 to be supplied into the energy storage module 500 from the intake port IP, creating an airflow AF inside the energy storage module 500. The supplied air passes through the energy storage module 500, cooling the energy storage device 100, and is discharged from the exhaust port OP. When the control device 430 detects, for example, that the temperature inside the energy storage module 500 has fallen below a predetermined second temperature, it stops the cooling fan 410. With such an air-cooled cooling device 400, the energy storage device 100 can be cooled at low cost.

[0045] Incidentally, according to the inventors' studies, a temperature distribution occurs inside a storage module 500 equipped with a cooling mechanism such as a cooling device 400 when multiple storage devices 100 are charged and discharged, resulting in a low-temperature region A1 where the temperature is relatively low and a high-temperature region A2 where the temperature is relatively high. Specifically, when a storage device 100 generates heat during charging and discharging, adjacent storage devices 100 heat each other. As a result, a chain reaction of heat generation occurs between the storage devices 100 in the central part of the array direction X, making it easy for the temperature to be relatively high. On the other hand, the ends of the array direction X (the front F and rear Rr parts in Figure 5) have better heat dissipation than the central part, so a chain reaction of heat generation is less likely to occur. Therefore, the temperature tends to be relatively low at both ends of the array direction X.

[0046] In particular, in this embodiment, an air intake IP and a cooling fan 410, to which refrigerant (air) is supplied, are located on the front F side of the array direction X, and an exhaust port OP is located on the rear Rr side of the array direction X. Therefore, both ends of the array direction X tend to be cold. Consequently, the central part of the array direction X tends to become a high-temperature region A2 with a relatively high temperature, and both ends of the array direction X (the front F and rear Rr parts in Figure 5) tend to become a low-temperature region A1 with a relatively low temperature. In particular, the front F part of the array direction X, where the air intake IP and cooling fan 410 are located, tends to be the coldest. That is, in this embodiment, at least the front F side of the array direction X tends to become a low-temperature region A1 with a relatively low temperature.

[0047] For example, as described in Patent Document 1, if a temperature distribution occurs within the energy storage module 500, variations may occur in the high-rate tolerance of the energy storage device 100. Specifically, the high-rate tolerance of the energy storage device 100 may be low in the low-temperature region A1. In this case, if the charging and discharging of the entire energy storage module 500 is controlled based on the high-rate tolerance of the energy storage device 100 in the low-temperature region A1, the high high-rate tolerance of the energy storage device 100 in the high-temperature region A2 cannot be fully utilized. On the other hand, if the high-rate tolerance of the energy storage device 100 in the high-temperature region A2 is used as the standard, a high voltage will be applied to the energy storage device 100 in the low-temperature region A1, and high-rate degradation is likely to accelerate. Thus, if a temperature distribution occurs within the energy storage module 500, the high-rate tolerance of the entire energy storage module 500 may decrease, being pulled down by the high-rate tolerance of the energy storage device 100 in the low-temperature region A1. Furthermore, if the energy storage module is mounted on a moving object such as a vehicle, fuel efficiency may worsen.

[0048] Therefore, the technology disclosed herein uses a first energy storage device 110 and a second energy storage device 120 as multiple energy storage devices 100, each having a different LiFSI ratio in the electrolyte salt. The first energy storage device 110 has a higher LiFSI ratio than the second energy storage device 120. As will be described in detail later, the inventors' studies have confirmed that a higher LiFSI ratio leads to higher high-rate resistance. For this reason, in this embodiment, the first energy storage device 110, which has a relatively high LiFSI ratio (high high-rate resistance), is placed in the low-temperature region A1, where the temperature is relatively low, specifically at both ends of the array direction X (the front F and rear Rr parts in Figure 5). In addition, the second energy storage device 120, which has a relatively low LiFSI ratio (low high-rate resistance), is placed in the high-temperature region A2, where the temperature is relatively high, specifically in the center of the array direction X.

[0049] This configuration allows for a high level of equalization of the high-rate resistance of multiple energy storage devices 100. Consequently, it is possible to suppress the acceleration of degradation and improve the overall high-rate resistance of the energy storage module 500. Furthermore, unlike the technology in Patent Document 1, there is no need to be constrained by the framework of "cell groups," so the high-rate resistance of multiple energy storage devices 100 can be flexibly adjusted according to the temperature distribution within the energy storage module 500. Therefore, in some cases, the high-rate resistance of multiple energy storage devices 100 can be equalized with higher precision than the technology in Patent Document 1. In addition, since the number of restraint mechanisms 300 can be reduced compared to the technology in Patent Document 1, volumetric energy density and fuel efficiency can also be improved. Moreover, the number of parts can be reduced, thereby lowering manufacturing costs.

[0050] The LiFSI ratio is the molar proportion of lithium bis(fluorosulfonyl)imide (LiFSI) in an electrolyte salt, calculated for example by (molar concentration of LiFSI / total molar concentration of electrolyte salt) × 100, and is expressed in the range of 0 to 100 mol%. That is, if the electrolyte salt does not contain LiFSI, it is 0 mol%, and if the electrolyte salt consists of LiFSI, it is 100 mol%. For example, if the electrolyte salt consists of LiFSI and / or LiPF6, the LiFSI ratio is calculated by (molar concentration of LiFSI / (molar concentration of LiFSI + molar concentration of LiPF6)) × 100.

[0051] In this embodiment, where there are multiple first energy storage devices 110 and multiple second energy storage devices 120, it is preferable that each of the multiple first energy storage devices 110 has a higher LiFSI ratio than each of the multiple second energy storage devices 120. Furthermore, although not particularly limited, from the viewpoint of improving the battery characteristics of the energy storage device 100 (for example, balancing energy density and high-rate tolerance at a high level), it is preferable that the total molar concentration of the electrolyte salt in both the first energy storage device 110 and the second energy storage device 120 is approximately 0.5 to 2.0 mol / L, more preferably 0.8 to 1.5 mol / L, and even more preferably 0.9 to 1.3 mol / L, for example 1.1 ± 0.1 mol / L. In particular, by setting the total molar concentration to below a predetermined value, the high-rate charging characteristics of the energy storage module 500 can be better improved.

[0052] The first energy storage device 110 includes LiFSI as an essential component and may further include, for example, LiPF6. This improves cycle characteristics and thermal stability. The electrolyte salt of the first energy storage device 110 may consist of LiFSI or of LiFSI and LiPF6. Depending on the temperature distribution within the energy storage module 500, in one embodiment, the molar concentration of LiFSI in the first energy storage device 110 is preferably about 0.1 mol / L or more, for example, 0.1 to 2.0 mol / L, more preferably 0.2 to 1.5 mol / L, for example, 0.2 to 1.1 mol / L or 0.55 to 1.1 mol / L. The molar concentration of LiPF6 in the first energy storage device 110 is preferably about 0 to 1.5 mol / L, more preferably 1.1 mol / L or less, for example, 0.83 mol / L or less, 0.55 mol / L or less, or 0.3 mol / L or less.

[0053] The second energy storage device 120 preferably contains LiPF6, and may further contain, for example, LiFSI. Including LiFSI further improves thermal stability in the high-temperature region A2. However, the electrolyte salt of the second energy storage device 120 does not have to contain LiFSI. The electrolyte salt of the second energy storage device 120 may consist of, for example, LiPF6, or LiFSI and LiPF6. Depending on the temperature distribution within the energy storage module 500, in one embodiment, the molar concentration of LiFSI in the second energy storage device 120 is preferably about 0 to 1.5 mol / L, more preferably 1.1 mol / L or less, and may be, for example, 0.83 mol / L or less, 0.55 mol / L or less, or 0.3 mol / L or less. From the viewpoint of thermal stability, the molar concentration of LiFSI in the second energy storage device 120 is preferably 0.01 mol / L or more, 0.05 mol / L or more, or 0.1 mol / L or more. The second energy storage device 120 preferably has a molar concentration of LiPF6 of approximately 0.1 mol / L or more, for example, 0.1 to 2.0 mol / L, more preferably 0.5 to 1.2 mol / L, and may also be, for example, 0.55 to 1.1 mol / L or 0.83 to 1.1 mol / L.

[0054] Depending on the temperature distribution within the energy storage module 500, in one embodiment, the LiFSI ratio of the first energy storage device 110 is preferably 10 to 100 mol%, more preferably 20 to 100 mol%, and even more preferably 25 to 100 mol% or 50 mol% or more. The LiFSI ratio of the second energy storage device 120 is preferably 50 mol% or less, for example 0 to 50 mol%, more preferably 0 to 30 mol%, and even more preferably 25% mol or less. The LiFSI ratio of the second energy storage device 120 may be 5 mol% or more, 10 mol% or more, and even more preferably 20 mol% or more.

[0055] The difference in LiFSI ratio between the first energy storage device 110 and the second energy storage device 120 (i.e., (LiFSI ratio of the first energy storage device 110) - (LiFSI ratio of the second energy storage device 120)) is a design item that is appropriately adjusted, for example, by the temperature distribution within the energy storage module 500. For this reason, although not particularly limited, when the temperature distributions of the first energy storage device 110 and the second energy storage device 120 differ significantly, it is preferable that the difference in LiFSI ratio between the first energy storage device 110 and the second energy storage device 120 be 10 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more. This allows the effects of the technology disclosed herein to be more pronounced. Furthermore, if there are multiple first energy storage devices 110 and second energy storage devices 120, the difference in the above LiFSI ratio may be the difference between the average LiFSI ratio of the multiple first energy storage devices 110 and the average LiFSI ratio of the multiple second energy storage devices 120.

[0056] In this embodiment, the electrolyte salt of the first energy storage device 110 and the second energy storage device 120 consists of LiFSI and / or LiPF6. Therefore, the first energy storage device 110, which has a high LiFSI ratio, has a lower molar ratio of LiPF6 in the electrolyte salt (LiPF6 ratio) than the second energy storage device 120. In one embodiment, the LiPF6 ratio of the first energy storage device 110 (mole ratio of LiPF6 in the electrolyte salt; the same applies hereinafter) is preferably 0 to 90 mol%, for example 0 to 80 mol%, more preferably 0 to 75 mol%, and more preferably 50 mol% or less. The LiPF6 ratio of the second energy storage device 120 is preferably 10 to 100 mol%, more preferably 50 mol% or more, and more preferably 70 mol% or more, for example 70 to 100 mol%, and more preferably 75 to 100 mol%.

[0057] In one embodiment, it is preferable that the first energy storage device 110 and the second energy storage device 120 have the same total molar concentration of electrolyte salt. In one embodiment, it is preferable that the first energy storage device 110 and the second energy storage device 120 have the same type and composition of non-aqueous solvent. This makes it easier to equalize the battery performance other than high-rate resistance between the first energy storage device 110 and the second energy storage device 120. The non-aqueous solvent in the first energy storage device 110 and the second energy storage device 120 may consist of carbonates. Among these, a mixed solvent containing cyclic carbonates and linear carbonates is preferred.

[0058] In one embodiment, it is preferable that the first energy storage device 110 and the second energy storage device 120 have the same configuration other than the non-aqueous electrolyte, particularly the configuration of the electrode body 20 (manufacturing tolerances, etc., may be permitted). This equalizes the energy density of the first energy storage device 110 and the second energy storage device 120, enabling high energy density for the entire energy storage module 500.

[0059] [Manufacturing method for energy storage modules] Next, a method for manufacturing an energy storage module 500 equipped with multiple energy storage devices 100 will be described. The energy storage module 500 can be manufactured by a manufacturing method that includes, for example, (Step A) a preparation step of preparing a first energy storage device 110 and a second energy storage device 120, (Step B) a temperature distribution prediction step of predicting the temperature distribution within the energy storage module 500, and (Step C) a construction step of constructing the energy storage module 500 by combining the first energy storage device 110 and the second energy storage device 120. 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, or both steps may be performed simultaneously. Furthermore, the manufacturing method disclosed herein may include other steps at any stage.

[0060] (Step A) Preparation step is prepared as a plurality of energy storage devices 100, including a first energy storage device 110 with a relatively high LiFSI ratio and a second energy storage device 120 with a relatively low LiFSI ratio. In this embodiment, (Step A) Preparation step includes, in this order, (A-1) an electrolyte preparation step of preparing a non-aqueous electrolyte, (A-2) a storage step of housing the electrode body 20 and the prepared non-aqueous electrolyte in the battery case 10, and (A-3) a conditioning step.

[0061] (A-1) In the electrolyte preparation step, at least two non-aqueous electrolytes with different LiFSI ratios are prepared. Specifically, a first electrolyte with a relatively high LiFSI ratio is prepared for the first energy storage device 110, and a second electrolyte with a relatively low LiFSI ratio is prepared for the second energy storage device 120. The first and second electrolytes may be purchased commercially or prepared by conventionally known methods. In one preferred embodiment, for example, the electrolyte salt (e.g., LiPF6) described above is added to a mixed solvent (non-aqueous solvent) containing two or more organic solvents, and the mixture is stirred and mixed until homogeneous to prepare the first electrolyte for the first energy storage device 110 and the second electrolyte for the second energy storage device 120.

[0062] (A-2) In the housing step, the electrode body 20, which has been prepared separately, is housed in the battery case 10 together with the first or second electrolyte. In one 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. This integrates the sealing plate 14 and the electrode body 20. Next, the sealing plate 14 is placed over the opening 12h of the outer casing 12, and the electrode body 20 is placed inside the outer casing 12. Next, the sealing plate 14 is welded to the periphery of the opening 12h of the outer casing 12 to integrate the outer casing 12 and the sealing plate 14. Next, the first or second electrolyte is injected into the inside of the battery case 10 through the injection hole 15 of the sealing plate 14. This allows for the fabrication of a battery assembly for the first energy storage device 110 and a battery assembly for the second energy storage device 120.

[0063] (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. Charging and discharging of the battery assembly can be done in the same manner as conventional methods. Typically, an external power supply is connected between the positive terminal 30 and the negative 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 this way, a first energy storage device 110 and a second energy storage device 120 with mutually different LiFSI ratios can be prepared.

[0064] (Step B) In the temperature distribution prediction step, the temperature distribution within the energy storage module 500 is predicted when multiple energy storage devices 100 are charged and discharged. That is, in the configuration shown in Figure 5, for example, both ends of the array direction X (particularly the front F in the array direction X) tend to become low-temperature regions A1. However, the temperature distribution within the energy storage module 500 can also change depending on the configuration of the cooling device 400 (for example, the installation position and number of intake ports IP, exhaust ports OP, and cooling fans 410) and the heat dissipation path. Also, for example, the range of the low-temperature region A1 (length of the array direction X) can also change depending on, for example, the number of energy storage devices 100 and the charging and discharging conditions. For this reason, it is preferable to predict the temperature distribution within the energy storage module 500 during charging and discharging by conducting preliminary experiments or simulations using commercially available analysis software. In particular, it is preferable to construct an energy storage module for preliminary testing that mimics the energy storage module 500, measure the temperature distribution, and predict the temperature distribution within the energy storage module 500 based on the measurements.

[0065] In one preferred embodiment, first, several preliminary test energy storage devices different from the first energy storage device 110 and the second energy storage device 120 manufactured in the preparation step are prepared, and a temperature sensor is attached to each of them. Next, a preliminary test energy storage module, which mimics the energy storage module 500, is assembled using the multiple preliminary test energy storage devices. Then, the multiple preliminary test energy storage devices are actually charged and discharged (preferably at a high rate), and the temperature distribution at this time is obtained. The charge and discharge conditions are preferably those that simulate the actual usage. Based on the obtained temperature distribution, the temperature distribution inside the energy storage module 500 is predicted and divided into, for example, a low-temperature region A1 and a high-temperature region A2 (for example, divided into two parts).

[0066] (Process C) In the construction process, the first energy storage device 110 and the second energy storage device 120 are arranged based on the temperature distribution predicted in the temperature distribution prediction process to construct the energy storage module 500. Specifically, the first energy storage device 110, which has a relatively high LiFSI ratio, is placed in the area designated as the low-temperature region A1, and the second energy storage device 120, which has a relatively low LiFSI ratio, is placed in the area designated as the high-temperature region A2. Then, the first energy storage device 110 and the second energy storage device 120 are restrained and held together integrally by a restraining mechanism 300, for example, along with multiple spacers 200. In this way, the energy storage module 500 can be constructed.

[0067] [Applications of energy storage modules] The energy storage module 500 can be used for various applications, but due to its excellent high-rate resistance, it is particularly suitable for applications requiring high output, such as a power source (drive power supply) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). By mounting the energy storage module 500 on a moving object such as a vehicle, the fuel efficiency (electricity consumption) of the moving object can be improved.

[0068] The following describes some test examples relating to the present invention, but it is not intended to limit the present invention to these test examples.

[0069] In this test, energy storage devices with different LiFSI ratios were constructed to confirm high-rate resistance. Specifically, LiFSI and LiPF6 were used as electrolyte salts to prepare non-aqueous electrolytes with the LiPF6 and LiFSI ratios shown in Table 1, and energy storage devices (lithium-ion secondary batteries, Examples 1 to 4) were fabricated using these non-aqueous electrolytes. The total molar concentration of the electrolyte salts was 1.1 mol / L (the same) for all energy storage devices. As the non-aqueous solvent, a mixed solvent was used, consisting of carbonates, specifically EC, DMC, and EMC, in a volume ratio of EC:DMC:EMC = 30:40:30. The components other than the non-aqueous electrolyte (electrodes, etc.) were also common to all energy storage devices. Next, the energy storage devices were adjusted to a state of charge of 50% under a temperature environment of 25°C, and a constant current discharge of 150A for 10 seconds was performed, and the discharge resistance was measured. Next, the battery voltage ΔV, which dropped over 10 seconds, was read, and the IV resistance (initial resistance) was calculated based on this battery voltage ΔV and the discharge current value (150A).

[0070] Next, under a temperature environment of 25°C, the energy storage device was adjusted to a state of charge (SOC) of 50%, and a high-rate endurance test was conducted by repeatedly performing a constant current charge at a charge rate of 150A for 10 seconds, followed by a 5-second pause, and then a constant current discharge at a discharge rate of 10A for 150 seconds, followed by a 5-second pause. This charge-discharge cycle was repeated 1000 times. After the high-rate endurance 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 endurance test to the initial resistance (IV resistance after endurance test / initial resistance). The results are shown in Table 1. Note that Table 1 shows the relative values ​​when the resistance increase rate in Example 1 is set to 1.00 (reference).

[0071] [Table 1]

[0072] As shown in Table 1, although the reason is unclear, energy storage devices with a higher LiFSI ratio showed the smallest increase in resistance after high-rate endurance testing, meaning they had higher high-rate tolerance. Therefore, the experimental results confirm that energy storage devices with a high LiFSI ratio have relatively superior high-rate tolerance compared to energy storage devices with a low LiFSI ratio.

[0073] Preferred embodiments of the present invention have been described above, but these embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed herein and common technical knowledge in the art. The technologies described in the claims include various modifications and changes to the embodiments illustrated above. For example, it is possible to replace parts of the above embodiments with other modifications, and it is also possible to add other modifications to the above embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0074] (1) For example, in the embodiment described above, in the preparation process (Step A), energy storage devices 100 with intentionally different LiFSI ratios were manufactured. However, the invention is not limited to this. For example, from among a large number of energy storage devices with varying LiFSI ratios, the first energy storage device 110 and the second energy storage device 120 can be selected and prepared within a predetermined range of good products.

[0075] A concrete example is when a used energy storage device (which may be in the form of an energy storage module) is collected from the market and reused, i.e., when the energy storage device 100 is a reused item. In recent years, energy storage devices such as lithium-ion secondary batteries are sometimes marked with identification information for traceability purposes. For example, an optical symbol that can be read by a reader is attached to the surface of the energy storage module (e.g., the sealing plate 14). Alternatively, a small circuit board containing identification information is mounted inside the energy storage device. Identification information may include ID information such as model number, manufacturer name, country of manufacture, manufacturing plant name, and date of manufacture, as well as material information such as the type of positive electrode active material, the type of negative electrode active material, and the type and concentration of the electrolyte salt.

[0076] In this case, (Step A) Preparation Step may include (Aa) an acquisition step of reading the identification information attached to each of the numerous recovered energy storage devices to obtain information on the type of electrolyte salt and, if LiFSI is included, the LiFSI ratio, and (Ab) a selection step of extracting multiple energy storage devices containing LiFSI based on the acquired information, and selecting from the extracted multiple energy storage devices a first energy storage device 110 with a relatively high LiFSI ratio and a second energy storage device 120 with a relatively low LiFSI ratio. Such a method for manufacturing energy storage modules can also be understood as a method for reusing energy storage devices. In this specification, "optical symbol" is a general term for information media that store information by a combination of parts with high and low optical reflectivity, and is a concept that includes two-dimensional symbols (also called two-dimensional codes, two-dimensional barcodes, etc.) such as QR codes (registered trademark), data matrices, and data tags.

[0077] (2) For example, in the embodiment shown in Figure 5 above, both ends of the array direction X (the front F and rear Rr parts in Figure 5) were low-temperature regions A1, and the central part of the array direction X was a high-temperature region A2, where the temperature was relatively high. However, it is not limited to this. As mentioned above, the temperature distribution within the energy storage module 500 can vary depending on the configuration of the cooling device 400 (for example, the location and number of intake ports IP, exhaust ports OP, and cooling fans 410), the number of energy storage devices 100, the charging and discharging conditions, etc. Also, in the embodiment shown in Figure 5 above, the inside of the energy storage module 500 was divided into two temperature regions, low-temperature region A1 and high-temperature region A2, and the temperature distribution was symmetrical with respect to the array direction X. However, it is not limited to this. For example, the inside of the energy storage module 500 can also be divided into three or more temperature regions. In that case, in the embodiment shown in Figure 5, the low-temperature region A1 on the rear Rr side in the arrangement direction X may be defined as a medium-temperature region A3 that is hotter than the low-temperature region A1 and hotter than the high-temperature region A2. Also, if the cooling path and heat dissipation path are complex, the temperature distribution may be random, for example, with the low-temperature region A1 and the high-temperature region A2 appearing alternately. Several specific modifications will be described below with reference to Figures 6 to 9. Note that the cooling device is not shown in Figures 6 to 9.

[0078] (First Modification) Figure 6 is a plan view of the energy storage module 500a according to the first modification. As described above, it is known that chain reaction of heat generation between the energy storage devices 100 is likely to occur in the central part of the array direction X. For this reason, although not shown in Figure 6, an air intake IP and / or an air-cooling fan 410 supplied with a coolant (air) may be additionally installed in the central part of the array direction X to strongly cool the central part. Then, as shown in Figure 6, the temperature distribution of the energy storage module 500a may be the opposite of that in Figure 5, with the central part of the array direction X becoming a low-temperature region A1 with a relatively low temperature, and both ends of the array direction X (the front F and rear Rr parts in Figure 6) becoming a high-temperature region A2 with a relatively high temperature.

[0079] In such cases, as shown in Figure 6, it is preferable to place the first energy storage device 110, which has a relatively high LiFSI ratio (high high-rate tolerance), in the center of the array direction X, which is the low-temperature region A1, and the second energy storage devices 120, which have a relatively low LiFSI ratio (low high-rate tolerance), at both ends of the array direction X, which is the high-temperature region A2.

[0080] (Second and Third Modifications) Figure 7 is a plan view of the energy storage module 500b according to the second modification. Figure 8 is a plan view of the energy storage module 500c according to the third modification. For example, if the cooling fan 410 installed on the front F side in the arrangement direction X of Figure 5 is powerful and has high cooling capacity, the temperature distribution within the energy storage modules 500b and 500c may be such that the front F part in the arrangement direction X becomes a relatively low-temperature region A1, and the rear Rr part in the arrangement direction X becomes a relatively high-temperature region A2.

[0081] In such cases, as shown in Figures 7 and 8, it is preferable to place the first energy storage device 110, which has a relatively high LiFSI ratio (high high-rate tolerance), in the front F portion of the array direction X, which is the low-temperature region A1, and the second energy storage device 120, which has a relatively low LiFSI ratio (low high-rate tolerance), in the rear Rr portion of the array direction X, which is the high-temperature region A2.

[0082] Furthermore, the distribution between the low-temperature region A1 and the high-temperature region A2 may vary depending on, for example, the number of energy storage devices 100, the charging and discharging conditions, etc. For this reason, the low-temperature region A1 and the high-temperature region A2 may be uniformly distributed in the array direction X, as shown in Figure 7, or they may be non-uniformly distributed in the array direction X, as shown in Figure 8. In other words, the number of first energy storage devices 110 and the number of second energy storage devices 120 included in the energy storage module 500 may be the same or different.

[0083] (Fourth Modification) Figure 9 is a plan view of the energy storage module 500d according to the fourth modification. As shown in Figure 9, the temperature distribution of the energy storage module 500d is divided in more detail here than in Figure 5. Specifically, both ends in the array direction X (the front F and rear Rr parts in Figure 6) are low-temperature regions A1 with relatively low temperatures, the central part in the array direction X is a high-temperature region A2 with relatively high temperatures, and the area between the low-temperature region A1 and the high-temperature region A2 is a medium-temperature region A3 that is hotter than the low-temperature region A1 and colder than the high-temperature region A2.

[0084] In such cases, as shown in Figure 9, it is preferable to place a first energy storage device 110 with a relatively high LiFSI ratio (high high-rate tolerance) at both ends of the array direction X, which is the low-temperature region A1; a second energy storage device 120 with a relatively low LiFSI ratio (low high-rate tolerance) at the center of the array direction X, which is the high-temperature region A2; and a third energy storage device 130 with a higher LiFSI ratio than the second energy storage device 120 and a lower LiFSI ratio than the first energy storage device 110 at the medium-temperature region A3, which is between the low-temperature region A1 and the high-temperature region A2. In other words, it is preferable to arrange multiple energy storage devices 100 in the order of high-temperature region A2, medium-temperature region A3, and low-temperature region A1, where the LiFSI ratio increases in stages from the center to both ends of the array direction X.

[0085] In Figure 9, the energy 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 dividing the energy storage module 500 into these finer sections according to the temperature distribution, the effects of the technology disclosed herein can be realized at a high level, and the overall high-rate resistance of the energy storage module 500 can be improved.

[0086] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: An energy storage module comprising a plurality of energy storage devices, each of the plurality of energy storage devices having an electrode body and a non-aqueous electrolyte, the non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte salt, the energy storage module having a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high when the plurality of energy storage devices are charged and discharged, wherein the molar ratio of lithium bis(fluorosulfonyl)imide in the electrolyte salt is defined as the LiFSI ratio, and the first energy storage device located in the low-temperature region has a higher LiFSI ratio than the second energy storage device located in the high-temperature region. Item 2: The energy storage module according to Item 1, wherein within the energy storage module there is a medium temperature region between the low temperature region and the high temperature region, where the temperature is higher than the low temperature region and lower than the high temperature region, and the multiple energy storage devices are arranged such that the LiFSI ratio increases in stages in the order of the high temperature region, the medium temperature region, and the low temperature region. Item 3: The energy storage module according to Item 1 or Item 2, wherein both the first energy storage device and the second energy storage device contain LiPF6 as the electrolyte salt. Item 4: The energy storage module according to Item 3, wherein the first energy storage device has a lower molar ratio of the LiPF6 in the electrolyte salt than the second energy storage device. Item 5: The first energy storage device is the energy storage module according to Item 1 or 2, wherein the LiFSI ratio is 10 mol% or more and 100 mol% or less. Item 6: The first energy storage device and the second energy storage device are both energy storage modules according to any one of items 1 to 5, wherein the total molar concentration of the electrolyte salt is 0.8 mol / L or more and 1.5 mol / L or less. Item 7: The first energy storage device and the second energy storage device are both energy storage modules according to any one of items 1 to 6, wherein the non-aqueous solvent includes carbonates. Item 8: A method for manufacturing an energy storage module comprising a plurality of energy storage devices, each of which has an electrode body and a non-aqueous electrolyte, the non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte salt, wherein, if the molar ratio of lithium bis(fluorosulfonyl)imide in the electrolyte salt is defined as the LiFSI ratio, the method comprises: a preparation step of preparing a plurality of energy storage devices, namely a first energy storage device having a relatively high LiFSI ratio and a second energy storage device having a relatively low LiFSI ratio; a temperature distribution prediction step of predicting the temperature distribution within the energy storage module when the plurality of energy storage devices are charged and discharged; and a construction step of constructing the energy storage module by arranging the first energy storage device in a relatively low temperature region and the second energy storage device in a relatively high temperature region based on the temperature distribution. [Explanation of Symbols]

[0087] 10 Battery Case 20 Electrode body 24 Negative electrode 100 Energy Storage Devices 110 First energy storage device 120 Second energy storage device 130 Third Energy Storage Device 300 Restraint mechanism 400 Cooling device 410 Air Cooling Fan 500 Energy Storage Modules A1 Low temperature area A2 High temperature area A3 Medium temperature range

Claims

1. A storage module comprising a plurality of energy storage devices arranged along the direction of arrangement, Each of the aforementioned energy storage devices comprises an electrode body and a non-aqueous electrolyte, The aforementioned non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt. Within the aforementioned energy storage module, there is a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high when multiple energy storage devices are being charged and discharged. Here, if we define the molar ratio of lithium bis(fluorosulfonyl)imide in the electrolyte salt as the LiFSI ratio, Among the multiple energy storage devices, the first energy storage device located in the low-temperature region has a higher LiFSI ratio than the second energy storage device located in the high-temperature region. One of the first energy storage device and the second energy storage device is arranged at both ends of the energy storage module in the arrangement direction. The other of the first and second energy storage devices is positioned in the center of the energy storage module in the direction of arrangement. Energy storage module.

2. Within the energy storage module, there is a medium temperature region between the low temperature region and the high temperature region, where the temperature is higher than the low temperature region and lower than the high temperature region. The multiple energy storage devices are arranged such that the LiFSI ratio increases in stages in the order of high temperature region, medium temperature region, and low temperature region. The energy storage module according to claim 1.

3. Both the first energy storage device and the second energy storage device contain LiPF6 as the electrolyte salt. The energy storage module according to claim 1.

4. The first energy storage device has a lower molar ratio of LiPF6 in the electrolyte salt than the second energy storage device. The energy storage module according to claim 3.

5. The first energy storage device has a LiFSI ratio of 10 mol% or more and 100 mol% or less. The energy storage module according to claim 1.

6. Both the first energy storage device and the second energy storage device have a total molar concentration of the electrolyte salt of 0.8 mol / L or more and 1.5 mol / L or less. A storage module according to any one of claims 1 to 5.

7. Both the first energy storage device and the second energy storage device contain carbonates as the non-aqueous solvent. A storage module according to any one of claims 1 to 5.

8. A method for manufacturing an energy storage module, comprising a plurality of energy storage devices arranged along the direction of arrangement, wherein each of the plurality of energy storage devices has an electrode body and a non-aqueous electrolyte, and the non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt, Here, if we define the molar ratio of lithium bis(fluorosulfonyl)imide in the electrolyte salt as the LiFSI ratio, A preparation step of preparing a plurality of energy storage devices, including a first energy storage device having a relatively high LiFSI ratio and a second energy storage device having a relatively low LiFSI ratio. A temperature distribution prediction step that predicts the temperature distribution within the energy storage module when multiple energy storage devices are charged and discharged, Based on the results of the temperature distribution prediction, a construction step is made to construct the energy storage module by placing the first energy storage device in a low-temperature region where the temperature is relatively low, and the second energy storage device in a high-temperature region where the temperature is relatively high. Includes, In the construction process, one of the first energy storage device and the second energy storage device is placed at both ends of the energy storage module in the arrangement direction. The other of the first energy storage device and the second energy storage device is positioned in the center of the energy storage module in the direction of arrangement. A method for manufacturing energy storage modules.

Images