Energy storage module and manufacturing method thereof

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 lower peak intensity ratio (I004 / I110) of a negative electrode active material layer 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 an electricity storage module including a plurality of electricity storage devices and a method for manufacturing the same. [Background technology]

[0002] Conventionally, power storage modules formed by electrically connecting a plurality of power storage devices (single cells) have been widely used in vehicle driving power sources, etc. Patent documents 1 to 4 are cited as related prior art documents.

[0003] For example, Patent Document 1 discloses an energy storage module having multiple submodules and a housing that houses the multiple submodules in predetermined positions. In Patent Document 1, each of the multiple submodules includes a cell group in which multiple energy storage devices (single cells) are arranged, and a restraining member that applies a restraining pressure in the arrangement direction to restrain the cell group. The housing includes an area that is prone to relatively low temperatures, and the submodules arranged in the area that is prone to low temperatures are configured so that the restraining pressure of the restraining member is relatively lower than that of the other submodules. Patent Document 1 describes that by reducing the restraining pressure on the energy storage devices in this area where high-rate resistance is prone to decrease (area that is prone to low temperatures), it is possible to level out the high-rate resistance (increase in resistance when high-rate charging and discharging is repeated) of the multiple energy storage devices. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-44212 [Patent Document 2] Japanese Patent Publication No. 2022-81868 [Patent Document 3] Japanese Patent Application Publication No. 2012-221816 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-90794 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-138644 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology described in Patent Document 1 above does not allow the multiple power storage devices included in one cell group to have different confinement pressures. Therefore, according to the inventors' studies, when a temperature distribution occurs within the cell group, it can be difficult to equalize the high-rate resistance of the multiple power storage devices. Furthermore, because a confinement member is required for each cell group, the confinement member becomes bulky, reducing the volumetric energy density of the entire power storage module. For example, when the power storage module is installed in a moving object such as a vehicle, the weight increases, potentially resulting in poor fuel efficiency.

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

[0007] According to the present invention, there is provided an electricity storage module including a plurality of electricity storage devices, wherein each of the plurality of electricity storage devices has a positive electrode and a negative electrode, and the negative electrode has a negative electrode active material layer containing graphite, and the electricity storage module includes a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high during charging and discharging of the plurality of electricity storage devices, and wherein when the negative electrode active material layer is measured by X-ray crystal structure analysis, a peak intensity I 110 The peak intensity I originating from the (004) plane of the graphite 004 The ratio (I 004 / I 110 ) is a peak intensity ratio, a first power storage device arranged in the low temperature region among the plurality of power storage devices has a lower peak intensity ratio than a second power storage device arranged in the high temperature region, thereby providing a power storage module.

[0008] The present invention also provides a method for producing an electricity storage module including a plurality of electricity storage devices, each of which has a positive electrode and a negative electrode, and the negative electrode including a negative electrode active material layer containing graphite. This method is characterized in that, when the negative electrode active material layer is measured by X-ray crystal structure analysis, a peak intensity I 110 The peak intensity I originating from the (004) plane of the graphite 004 The ratio (I 004 / I 110 ) is a peak intensity ratio, the method includes a preparation step of preparing, as the plurality of electricity storage devices, a first electricity storage device having a relatively low peak intensity ratio of the negative electrode active material layer and a second electricity storage device having a relatively high peak intensity ratio; a temperature distribution prediction step of predicting a temperature distribution in the electricity storage module when the plurality of electricity storage devices are charged and discharged; and a construction step of constructing the electricity storage module by arranging the first electricity storage device in a low-temperature region where the temperature is relatively low and arranging the second electricity storage device in a high-temperature region where the temperature is relatively high, based on the temperature distribution.

[0009] After extensive investigations, the inventors of the present invention found that an electricity storage device with a low peak intensity ratio in the negative electrode active material layer has relatively better high-rate resistance than an electricity storage device with a high peak intensity ratio in the negative electrode active material layer. Therefore, in the present invention, an electricity storage device with a relatively low peak intensity ratio (good high-rate resistance) is arranged in a low-temperature region where high-rate resistance is likely to decrease. This makes it possible to equalize the high-rate resistance of multiple electricity storage devices. Ultimately, it is possible to improve the high-rate resistance of the entire electricity storage module. Furthermore, unlike the technology of Patent Document 1, this technology is not limited to the framework of a "cell group," and therefore allows for flexible adjustment of the high-rate resistance of each electricity storage device. Furthermore, since the number of restraining members can be reduced compared to the technology of Patent Document 1, it is possible to improve volumetric energy density and fuel efficiency.

[0010] Although not particularly related to the technology disclosed herein, Patent Document 5 describes a range of the degree of orientation of a negative electrode active material layer that is suitable for an electricity storage device. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view schematically illustrating an electricity storage module according to one embodiment. [Figure 2] FIG. 2 is a perspective view schematically showing the secondary battery of FIG. [Figure 3] FIG. 3 is a schematic vertical cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of the electrode body of FIG. [Figure 5] FIG. 5 is a plan view schematically showing the power storage module and the cooling device of FIG. [Figure 6] FIG. 6 is a plan view schematically showing an electricity storage module according to a first modified example. [Figure 7] FIG. 7 is a plan view schematically showing an electricity storage module according to a second modified example. [Figure 8] FIG. 8 is a plan view schematically showing an electricity storage module according to a third modified example. [Figure 9] FIG. 9 is a plan view schematically showing an electricity storage module according to a fourth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the technology disclosed herein will be described below with reference to the accompanying drawings. Matters necessary for implementing the present invention other than those specifically mentioned in this specification (for example, the general configuration and manufacturing process of an energy storage module or energy storage device that do not characterize the present invention) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The energy storage module disclosed herein can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

[0013] In the following drawings, the same reference numerals are used to designate components and parts that perform the same function, and redundant explanations may be omitted or simplified. In addition, in this specification, the expression "A to B" indicating a range means not less than A and not more than B, and also encompasses the meanings of "preferably larger than A" and "preferably smaller than B."

[0014] [Energy storage module] 1 is a perspective view schematically illustrating an energy storage module 500. Here, the energy storage module 500 includes a plurality of energy storage devices 100, a plurality of spacers 200, and a restraining mechanism 300. However, the plurality of spacers 200 and the restraining mechanism 300 are not essential and may be omitted in other embodiments.

[0015] In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction, the long side direction perpendicular to the short side direction, and the up-down direction, respectively, of the energy storage device 100. The short side direction X is also the arrangement direction of the energy storage devices 100. However, these directions are merely used for convenience of description and do not limit the installation form of the energy storage module 500 in any way.

[0016] The restraining mechanism 300 is a member that restrains the multiple power storage devices 100. In this embodiment, there is only one restraining mechanism 300. The restraining mechanism 300 is configured to apply an equal restraining pressure to all of the power storage devices 100 and the spacers 200 in the arrangement direction X. The restraining 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 understood as a housing that houses the multiple power storage devices 100. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal.

[0017] The pair of end plates 310 are arranged at both ends of the energy storage module 500 in the arrangement direction X. The pair of end plates 310 sandwich the plurality of energy storage devices 100 and the plurality of spacers 200 in the arrangement direction X. The 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 with a plurality of screws 330 so that the restraining load is, for example, approximately 10 to 15 kN. This allows a uniform restraining load to be applied to the plurality of energy storage devices 100 in the arrangement direction X, and the plurality of energy storage devices 100 are held together. 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, bind bars, or the like, instead of the side plates 320.

[0018] Here, the spacers 200 are arranged between the plurality of power storage devices 100 in the arrangement direction X. That is, the power storage devices 100 and the spacers 200 are arranged alternately in the arrangement direction X. However, if the power storage module 500 does not include a spacer 200, the power storage devices 100 adjacent to each other in the arrangement direction X may abut (directly contact) each other. The spacers 200 preferably include a portion with a porous structure that allows a fluid (typically, a gas such as air) to pass through.

[0019] The electricity storage device 100 is a device that can be repeatedly charged and discharged. In this specification, the term "electricity 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 plurality of electricity storage devices 100 are arranged between a pair of end plates 310 along an arrangement direction X (in other words, a thickness direction X of the electricity storage device 100). The plurality of electricity storage devices 100 are preferably restrained by a restraining mechanism 300. The shape, size, number, etc. of the plurality of electricity storage devices 100 are not limited to the embodiment disclosed in FIG. 1 and can be changed as appropriate.

[0020] Although not shown here, when the energy storage module 500 is in use, the multiple energy storage devices 100 are electrically connected to each other by conductive members such as bus bars. The connection method is not particularly limited, and may be, for example, series, parallel, or multi-series / multi-parallel. In a preferred embodiment, the multiple energy storage devices 100 are connected in series. This makes it possible to suitably improve the output characteristics to a level suitable for use in a mobile body such as a vehicle. Furthermore, in the case of a series connection, performance degradation of some of the energy storage devices 100 is likely to lead to performance degradation of the entire energy storage module 500. For this reason, applying the technology disclosed herein is particularly effective.

[0021] FIG. 2 is a perspective view of the electricity storage device 100. As can be seen from FIGS. 1 and 2, the plurality of electricity storage devices 100 are all flat and rectangular, and have the same shape here. The plurality of electricity storage devices 100 are arranged so that their long side walls 12b, which will be described later, are parallel to each other. Here, the plurality of electricity storage devices 100 are lined up in the arrangement direction X with the long side walls 12b facing each other via spacers 200.

[0022] Fig. 3 is a schematic longitudinal sectional view taken along line III-III in Fig. 2. As shown in Fig. 3, the electricity storage device 100 here includes a battery case 10, an electrode assembly 20, a positive electrode terminal 30, and a negative electrode terminal 40. Although not shown, the electricity storage device 100 here further includes a non-aqueous electrolyte. The electricity storage device 100 is configured by accommodating the electrode assembly 20 and the non-aqueous electrolyte in a battery case 10 to which the positive electrode terminal 30 and the negative electrode terminal 40 are attached. The electricity storage device 100 is typically a non-aqueous electrolyte secondary battery, and is a lithium ion secondary battery here. When the electricity 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 accommodates the electrode assembly 20 and the nonaqueous electrolyte. As shown in FIG. 2, the battery case 10 has a flat, bottomed, rectangular parallelepiped (rectangular) outer shape. The material of the battery case 10 may be the same as that conventionally used, and is not particularly limited. The battery case 10 is made of, for example, aluminum, an aluminum alloy, iron, an 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) 14 that seals the opening 12h. As shown in FIG. 2, the exterior body 12 includes 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-like member. The sealing plate 14 has a substantially rectangular shape. 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 with the exterior body 12 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 (sealed). The sealing plate 14 has a liquid filling hole 15 and two terminal holes 18 and 19. The liquid filling hole 15 is for filling the nonaqueous electrolyte after the sealing plate 14 is assembled to the exterior body 12. The liquid filling hole 15 is sealed with a sealing member 16. The terminal holes 18 and 19 penetrate the sealing plate 14 in the up-down direction Z.

[0025] The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the long side direction Y (the left end in FIGS. 2 and 3 ), and the negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIGS. 2 and 3 ). As shown in FIG. 3 , the positive electrode terminal 30 and the negative electrode terminal 40 extend from the inside to the outside of the sealing plate 14 through the terminal lead-out holes 18 and 19, respectively. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are crimped to the peripheral portion of the sealing plate 14 surrounding the terminal lead-out holes 18 and 19 by crimping. Crimped portions 30c and 40c are formed at the ends of the positive electrode terminal 30 and the negative electrode terminal 40 on the exterior body 12 side (the lower end in FIG. 3 ). In this way, 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 assembly 20 via a positive electrode current collector 50 inside the exterior housing 12. The positive electrode terminal 30 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90. The negative electrode terminal 40 is electrically connected to the negative electrode tab group 25 of the electrode assembly 20 via a negative electrode current collector 60 inside the exterior housing 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 , a plate-shaped positive electrode external conductive member 32 and a plate-shaped negative electrode external conductive member 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 that electrically connect multiple electricity 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 an external insulating member 92. The electricity storage module 500 is connected in series, for example, by electrically connecting the positive electrode external conductive member 32 of one electricity storage device 100 and the negative electrode external conductive member 42 of the other electricity storage device 100 by a bus bar or the like, among the electricity storage devices 100 adjacent to each other in the arrangement direction X.

[0028] FIG. 4 is a schematic diagram showing the configuration of the electrode assembly 20. As shown in FIG. 4, the electrode assembly 20 has a positive electrode 22, a negative electrode 24, and a separator 26. Here, the electrode assembly 20 is a wound electrode assembly formed by stacking a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 with a strip-shaped separator 26 interposed therebetween and winding the stack around a winding axis WL. The electrode assembly 20 has a flat outer shape. Here, the electrode assembly 20 is disposed inside the exterior body 12 with the winding axis WL oriented substantially parallel to the long-side direction Y. However, in other embodiments, the electrode assembly 20 may be disposed inside the exterior body 12 with the winding axis WL oriented substantially parallel to the up-down direction Z. The electrode assembly 20 may also be a stacked electrode assembly formed by stacking a plurality of square-shaped (typically rectangular) positive electrodes and a plurality of square-shaped (typically rectangular) negative electrodes in an insulated state.

[0029] The configuration of the positive electrode 22 may be the same as that of a conventional positive electrode. Here, the positive electrode 22 has 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 made of metal foil. Here, the positive electrode current collector 22c is aluminum foil.

[0030] A plurality of positive electrode tabs 22t are provided at one end in the long side direction Y of the positive electrode current collector 22c (the left end in FIG. 4). 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 further in the long side direction Y than the separator 26. In this example, the positive electrode tab 22t is part of the positive electrode current collector 22c and is made of metal foil (aluminum foil). The plurality of positive electrode tabs 22t are stacked at one end in the long side direction Y (the left end in FIG. 4) 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 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 that can reversibly store and release 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 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 contain optional components other than the inorganic filler, such as a conductive material, a binder, various additive components, etc.

[0033] The negative electrode 24 includes 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, more preferably metal foil. In this example, the negative electrode current collector 24c is copper foil.

[0034] A plurality of 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 FIG. 4). The plurality of negative electrode tabs 24t protrude toward one side in the long side direction Y (the right end in FIG. 4). The plurality of negative electrode tabs 24t protrude further in the long side direction Y than the separator 26. In this example, the negative electrode tab 24t is part of the negative electrode current collector 24c and is made of metal foil (copper foil). The plurality of negative electrode tabs 24t are stacked at one end in the long side direction Y (the right end in FIG. 4) to form a negative electrode tab group 25. The negative electrode tab group 25 is provided at 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. The length Ln of the negative electrode active material layer 24a in the long side direction Y is preferably equal to or longer than the length Lp of the positive electrode active material layer 22a in the long side direction Y. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. The negative electrode active material essentially contains graphite. The graphite may be natural graphite or artificial graphite, or may be amorphous carbon-coated graphite in which graphite is coated with an amorphous carbon material. The negative electrode active material may further contain materials other than graphite, such as carbon materials such as hard carbon and soft carbon, or compounds containing silicon (Si-containing materials).

[0036] Although not particularly limited, the proportion of the negative electrode active material in the negative electrode active material layer 24a is preferably 90% by mass or more, and more preferably, for example, 95 to 99% by mass. 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. Examples of binders include styrene butadiene rubber (SBR) and polyvinylidene fluoride (PVdF). Examples of thickeners include carboxymethyl cellulose (CMC).

[0037] 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 from the negative electrode 24. The separator 26 may have a conventional configuration. The length Ls of the separator 26 in the long side direction Y is preferably equal to or longer than the length Ln of the negative electrode active material layer 24a in the long side direction Y. The separator 26 is preferably a resin porous sheet (microporous membrane) made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP). The separator 26 may have a functional layer (e.g., an adhesive layer or a heat resistance layer (HRL)) on the surface of the resin porous sheet.

[0038] The non-aqueous electrolyte may have the same configuration as conventional ones. The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt (electrolyte salt). The non-aqueous solvent is, for example, a carbonate such as ethylene carbonate, dimethyl carbonate, or 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 needed. The non-aqueous electrolyte is typically liquid, but may also be gel-like. In another embodiment, the electricity storage device 100 may include a solid electrolyte instead of the non-aqueous electrolyte. In this case, the separator 26 may be omitted.

[0039] FIG. 5 is a plan view schematically showing an electricity storage module 500 and a cooling device 400. Note that detailed illustration of the spacer 200 and the top surface of the electricity storage device 100 is omitted in FIG. 5. As shown in FIG. 5, the cooling device 400 includes an air intake port IP, an exhaust port OP, an air-cooled 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. However, in other embodiments, the cooling device 400 may be a liquid-cooled type cooling device that uses a liquid refrigerant.

[0040] In this embodiment, the air intake port IP is provided on one side (front F side) in the arrangement direction X of the power storage module 500. The air 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 air intake port IP. The air cooling fan 410 is configured to send wind (air) to the air intake port IP. The configuration of the air cooling fan 410 is not limited, but may include, for example, an electric motor (not shown). Here, the temperature sensor 420 is disposed in the center of the power storage module 500 in the XY plane. The temperature sensor 420 is, for example, a thermocouple or a thermistor.

[0041] The control device 430 is electrically connected to the temperature sensor 420 and the electric motor of the air-cooling fan 410. For example, when the temperature sensor 420 detects 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 through the air intake port IP, generating an air flow AF inside the power storage module 500. The supplied air passes through the power storage module 500 while cooling the power storage device 100, and is then discharged through the air exhaust port OP. For example, when the temperature sensor 420 detects 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. Using this air-cooling type cooling device 400, the power storage device 100 can be cooled at low cost.

[0042] According to the study by the present inventors, a temperature distribution occurs in an energy storage module 500 equipped with a cooling mechanism such as the cooling device 400 during charging and discharging of a plurality of energy storage devices 100, and a low-temperature region A1 where the temperature is relatively low and a high-temperature region A2 where the temperature is relatively high may occur. Specifically, when the energy storage devices 100 generate heat as they are charged and discharged, adjacent energy storage devices 100 heat each other. As a result, a chain reaction of heat generation occurs between the energy storage devices 100 in the central portion of the arrangement direction X, and the temperature tends to become relatively high. On the other hand, the two ends of the arrangement direction X (the front portion F and the rear portion Rr in FIG. 5 ) have higher heat dissipation properties than the central portion, and thus the chain reaction of heat generation is less likely to occur. Therefore, the two ends of the arrangement direction X tend to have a relatively low temperature.

[0043] In particular, in this embodiment, the intake port IP and the air-cooling fan 410, through which the refrigerant (air) is supplied, are arranged on the front F side in the arrangement direction X, and the exhaust port OP is arranged on the rear Rr side in the arrangement direction X. For this reason, both ends in the arrangement direction X tend to have low temperatures. Therefore, the central portion in the arrangement direction X becomes a high-temperature region A2 with a relatively high temperature, and both ends in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 5) tend to become low-temperature regions A1 with a relatively low temperature. In particular, the front F portion in the arrangement direction X, where the intake port IP and the air-cooling fan 410 are arranged, tends to have the lowest temperature. That is, in this embodiment, at least the front F side in the arrangement direction X tends to become a low-temperature region A1 with a relatively low temperature.

[0044] As described in, for example, Patent Document 1, when a temperature distribution occurs within the power storage module 500, variations in the high-rate resistance of the power storage device 100 may occur. Specifically, the high-rate resistance of the power storage device 100 may be reduced in the low-temperature region A1. In this case, if the charging and discharging of the entire power storage module 500 is controlled based on the high-rate resistance of the power storage device 100 in the low-temperature region A1, the high high-rate resistance of the power storage device 100 in the high-temperature region A2 cannot be fully utilized. On the other hand, if the high-rate resistance of the power storage device 100 in the high-temperature region A2 is used as the reference, a high voltage is applied to the power storage device 100 in the low-temperature region A1, which is likely to accelerate high-rate degradation. When a temperature distribution occurs within the power storage module 500, the high-rate resistance of the entire power storage module 500 may be reduced due to the influence of the high-rate resistance of the power storage device 100 in the low-temperature region A1. Furthermore, when the power storage module is installed in a moving object such as a vehicle, fuel efficiency may be reduced.

[0045] Therefore, in the technology disclosed herein, a plurality of power storage devices 100 are used, and the peak intensity ratio (I 004 / I 110) are used. The first electricity storage device 110 has a lower peak intensity ratio of the negative electrode active material layer 24a than the second electricity storage device 120. As will be described in detail later, the inventors have confirmed that the lower the peak intensity ratio of the negative electrode active material layer 24a, the higher the high-rate resistance. Therefore, in this embodiment, the first electricity storage device 110, which has a relatively low peak intensity ratio of the negative electrode active material layer 24a (high high-rate resistance), is arranged in a low-temperature region A1 where the temperature is relatively low, here, at both ends in the arrangement direction X (the front part F and the rear part Rr in FIG. 5 ). Furthermore, the second electricity storage device 120, which has a relatively high peak intensity ratio of the negative electrode active material layer 24a (low high-rate resistance), is arranged in a high-temperature region A2 where the temperature is relatively high, here, at the center in the arrangement direction X.

[0046] With this configuration, the high-rate resistance of the multiple power storage devices 100 can be equalized to a high level. Consequently, the acceleration of degradation can be suppressed, improving the high-rate resistance of the entire power storage module 500. Furthermore, unlike the technology of Patent Document 1, there is no need to be bound by the framework of a "cell group," so the high-rate resistance of the multiple power storage devices 100 can be flexibly adjusted according to the temperature distribution within the power storage module 500. Therefore, it may be possible to equalize the high-rate resistance of the multiple power storage devices 100 with higher accuracy than with 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, volumetric energy density and fuel efficiency can also be improved. Additionally, the number of parts can be reduced, reducing manufacturing costs.

[0047] The peak intensity ratio (I 004 / I 110) is an index representing the degree of orientation of the hexagonal mesh plane of graphite with respect to the thickness direction of the negative electrode 24 (the normal direction of the negative electrode current collector 24c), and a smaller value indicates that the hexagonal mesh plane is more aligned perpendicularly to the negative electrode current collector 24c. The peak intensity ratio can be calculated based on the measurement results of X-ray crystal structure analysis. Specifically, when the negative electrode active material layer 24a is measured by X-ray diffraction (XRD), for example, the peak derived from the (110) plane of graphite appears in the region of 2θ = 76.5° to 78.5° in the XRD chart, and the peak derived from the (004) plane of graphite appears in the region of 2θ = 53.5° to 56.0°. Therefore, the peak intensity (maximum intensity) I of the peak derived from the (004) plane can be calculated from the XRD chart using commercially available analysis software. 004 and the peak intensity (maximum intensity) of the peak originating from the (110) plane, I 110 and are respectively found, and the peak intensity ratio can be found by calculating the ratio between them.

[0048] The peak intensity ratio of the negative electrode active material layer 24a can be adjusted relatively easily, for example, by changing the type of graphite used as the negative electrode active material (the crystalline orientation of the graphite itself) or by applying a magnetic field to the negative electrode composite on the negative electrode current collector 24c in the (A-1) negative electrode production step of the manufacturing method described below.

[0049] When there are a plurality of first electricity storage devices 110 and a plurality of second electricity storage devices 120 as in the present embodiment, it is preferable that the peak intensity ratio of the anode active material layer 24a of each of the plurality of first electricity storage devices 110 is lower than that of the plurality of second electricity storage devices 120. Furthermore, from the viewpoint of achieving a high level of balance between energy density and high-rate resistance, the peak intensity ratio of the anode active material layer 24a of each of the first electricity storage devices 110 and the second electricity storage devices 120 is preferably in the range of approximately 1 to 50, more preferably in the range of 2 to 40, and more preferably in the range of, for example, 2.9 to 32.5, although this is not particularly limited. In particular, by setting the peak intensity ratio to a predetermined value or less, expansion of the anode 24 during high-rate charging can be more effectively suppressed.

[0050] Although it depends on the temperature distribution in the electricity storage module 500, in one embodiment, the peak intensity ratio of the negative electrode active material layer 24a of the first electricity storage device 110 is preferably approximately 40 or less, for example, in the range of 1 to 35, 2 to 30, or even 2 to 20, or 2 to 15. The peak intensity ratio of the negative electrode active material layer 24a of the second electricity storage device 120 is preferably approximately 50 or less, for example, in the range of 2 to 50, 5 to 40, or even 10 to 35.

[0051] The difference in packing density between the negative electrode active material layer 24a of the first power storage device 110 and the negative electrode active material layer 24a of the second power storage device 120 is a design factor that is appropriately adjusted, for example, depending on the temperature distribution within the power storage module 500. Therefore, although not particularly limited, when the temperature distributions between the first power storage device 110 and the second power storage device 120 are significantly different, the difference in peak intensity ratio between the negative electrode active material layer 24a of the first power storage device 110 and the second power storage device 120 is preferably 0.5 or more, more preferably 1 or more, and even more preferably 2 or more, 3 or more, or 4 or more. By setting the difference in peak intensity ratio to a predetermined value or more, the effects of the technology disclosed herein can be more pronounced. The difference in peak intensity ratio may be, for example, 8 or less, 7 or less, or 5 or less. This allows the high-rate charging characteristics of the first power storage device 110 and the second power storage device 120 to be accurately equalized. In addition, when there are multiple first power storage devices 110 and multiple second power storage devices 120, the difference in peak intensity ratio may be the difference between the average of the peak intensity ratios of the multiple first power storage devices 110 and the average of the peak intensity ratios of the multiple second power storage devices 120.

[0052] In a preferred embodiment, the first electricity storage device 110 contains artificial graphite as the graphite, and the second electricity storage device 120 contains natural graphite as the graphite. Preferably, in the first electricity storage device 110, artificial graphite is the main component of the negative electrode active material (meaning that it accounts for 50 mass % or more; the same applies hereinafter), and in the second electricity storage device 120, natural graphite is the main component of the negative electrode active material. This allows the peak intensity ratios of the first electricity storage device 110 and the second electricity storage device 120 to differ greatly.

[0053] In another preferred embodiment, the first electricity storage device 110 and the second electricity storage device 120 contain the same type of graphite. For example, both the first electricity storage device 110 and the second electricity storage device 120 contain artificial graphite. Alternatively, both the first electricity storage device 110 and the second electricity storage device 120 contain natural graphite. When the first electricity storage device 110 and the second electricity storage device 120 contain the same type of graphite, a magnetic field can be applied to the negative electrode composite on the negative electrode current collector 24c when fabricating the negative electrode 24 of the first electricity storage device 110 in the negative electrode fabrication step (A-1) of the manufacturing method described below. This reduces the peak intensity ratio, making it possible to make the peak intensity ratio significantly different from that of the second electricity storage device 120.

[0054] In one embodiment, the first electricity storage device 110 and the second electricity storage device 120 are preferably configured so that the thickness and basis weight (the mass of the negative electrode active material layer 24a per unit area of ​​the negative electrode current collector 24c) of the negative electrode active material layer 24a are the same and so that the negative electrode capacities are equal (manufacturing errors and the like are acceptable). This equalizes the energy densities of the first electricity storage device 110 and the second electricity storage device 120, thereby achieving a high energy density for the electricity storage module 500 as a whole.

[0055] In one embodiment, the first electricity storage device 110 and the second electricity storage device 120 preferably have the same configuration other than the negative electrode active material layer 24a, such as the configuration of the positive electrode 22, the separator 26, and the nonaqueous electrolyte. This makes it easier to equalize the battery performance other than high-rate resistance between the first electricity storage device 110 and the second electricity storage device 120.

[0056] [Method of manufacturing energy storage modules] Next, a method for manufacturing an energy storage module 500 including a plurality of energy storage devices 100 will be described. The energy storage module 500 can be manufactured by a manufacturing method including, 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 a temperature distribution in the energy storage module 500; and (Step C) a construction step of combining the first energy storage device 110 and the second energy storage device 120 to construct the energy storage module 500. The order of the (Step A) preparation step and the (Step B) temperature distribution prediction step is not particularly limited. For example, the (Step A) preparation step may be followed by the (Step B) temperature distribution prediction step, or the (Step B) preparation step may be followed by the (Step A) temperature distribution prediction step, or both steps may be performed simultaneously. The manufacturing method disclosed herein may further include other steps at any stage.

[0057] In the (Step A) preparation step, a first electricity storage device 110 having a relatively low peak intensity ratio in the negative electrode active material layer 24a and a second electricity storage device 120 having a relatively high peak intensity ratio in the negative electrode active material layer 24a are prepared as a plurality of electricity storage devices 100. In this embodiment, the (Step A) preparation step includes, in this order, (A-1) a negative electrode fabrication step of fabricating a negative electrode 24, (A-2) an electrode assembly fabrication step of fabricating an electrode assembly 20 using the negative electrode 24, (A-3) an accommodation step of accommodating the electrode assembly 20 and a nonaqueous electrolyte solution in a battery case 10, and (A-4) a conditioning step.

[0058] In the (A-1) negative electrode preparation step, at least two types of negative electrodes 24 are prepared, each having a different peak intensity ratio in the negative electrode active material layer 24a. Specifically, a first negative electrode having a relatively low peak intensity ratio is prepared for the first electricity storage device 110, and a second negative electrode having a relatively high peak intensity ratio is prepared for the second electricity storage device 120. That is, this step includes a first negative electrode preparation step of preparing a first negative electrode for the first electricity storage device 110, and a second negative electrode preparation step of preparing a second negative electrode for the second electricity storage device 120.

[0059] This process includes a preparation step, an application step, and a magnetic field application step. In the preparation step, for example, first, a negative electrode composite paste containing at least graphite is prepared by dispersing the above-mentioned solid materials (e.g., graphite as a negative electrode active material, a binder, a thickener, etc.) in a predetermined solvent (e.g., water, N-methyl-2-pyrrolidone, etc.). The type of graphite may be the same or different between the first and second negative electrodes. In this embodiment, the type of graphite is the same. For example, both the first and second negative electrodes contain artificial graphite. Alternatively, both the first and second negative electrodes contain natural graphite. This eliminates the need to separately prepare negative electrode composite pastes.

[0060] Next, in the application step, the prepared negative electrode composite paste is applied onto the negative electrode current collector 24c using a conventionally known coating device. Then, in the magnetic field application step, a magnetic field is applied to the first negative electrode in the thickness direction before the applied negative electrode composite paste solidifies (completely dries). This causes the graphite contained in the negative electrode composite paste to be oriented in the thickness direction so as to be parallel to the magnetic field lines, thereby reducing the peak intensity ratio. Note that the application of the magnetic field can be performed by a conventionally known method, such as that described in Patent Document 4, so that the graphite is appropriately oriented. Then, after the graphite is oriented, the negative electrode composite paste is dried, whereby the negative electrode composite is fixed to the surface of the negative electrode current collector 24c, and a first negative electrode with an increased peak intensity ratio can be produced.

[0061] On the other hand, for the second negative electrode, the negative electrode composite paste is applied to the surface of the negative electrode current collector 24c and then dried without applying a magnetic field. This allows the negative electrode composite to adhere to the surface of the negative electrode current collector 24c, resulting in a second negative electrode with a relatively low peak intensity ratio. However, a magnetic field may also be applied to the second negative electrode in the same manner as the first negative electrode. In this case, it is preferable that the conditions for applying the magnetic field (e.g., magnetic field strength, application time, etc.) be smaller than those for the first negative electrode. For example, the magnetic flux density of the magnetic field for the second negative electrode may be lower than that for the first negative electrode. This allows the peak intensity ratios of the negative electrode active material layers 24a to be significantly different from each other. In this manner, at least two types of negative electrodes 24, each having a negative electrode active material layer 24a with different peak intensity ratios, can be fabricated.

[0062] In the (A-2) electrode assembly preparation step, the first and second negative electrodes prepared in the negative electrode preparation step are each wound up opposite a separately prepared positive electrode 22 with the separator 26 as described above interposed therebetween. This produces an electrode assembly 20 for the first electricity storage device 110 and an electrode assembly 20 for the second electricity storage device 120.

[0063] In the (A-3) accommodation step, the electrode assembly 20 prepared in the electrode assembly preparation step and the nonaqueous electrolyte solution as described above are accommodated in the battery case 10. In a preferred embodiment, first, the positive electrode tab group 23 of the electrode assembly 20 is joined to the positive electrode current collector 50, and the negative electrode tab group 25 of the electrode assembly 20 is joined to the negative electrode current collector 60. This integrates the sealing plate 14 and the electrode assembly 20. Next, the sealing plate 14 is placed over the opening 12h of the exterior body 12, and the electrode assembly 20 is placed inside the exterior body 12. Next, the sealing plate 14 is welded to the periphery of the opening 12h of the exterior body 12, thereby integrating the exterior body 12 and the sealing plate 14. Next, the nonaqueous electrolyte solution as described above is prepared and injected into the battery case 10 through the injection hole 15 of the sealing plate 14. In this way, a battery assembly for the first power storage device 110 and a battery assembly for the second power storage device 120 are fabricated.

[0064] (A-4) In the conditioning step, the fabricated battery assembly is charged at least once. Preferably, it is charged and discharged at least once. Charging and discharging of the battery assembly can be performed in the same manner as conventional methods. 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 a predetermined state of charge (SOC) is reached between the terminals. Then, the battery case 10 is airtightly sealed (sealed). In this manner, a first electricity storage device 110 and a second electricity storage device 120 having different peak intensity ratios of the negative electrode active material layer 24a can be prepared.

[0065] (Step B) In the temperature distribution prediction step, the temperature distribution in 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 embodiment shown in FIG. 5 , both ends in the arrangement direction X (particularly the front F portion in the arrangement direction X) tend to become low-temperature regions A1. However, the temperature distribution in the power storage module 500 may vary depending on the configuration of the cooling device 400 (e.g., the installation positions and number of the air intake port IP, the air exhaust port OP, and the air-cooling fan 410) and the heat dissipation path. Furthermore, for example, the range of the low-temperature region A1 (the length in the arrangement direction X) may also 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 in the power storage module 500 during charge and discharge by a preliminary experiment or a simulation using commercially available analysis software. In particular, it is preferable to construct a power storage module for preliminary testing that simulates the power storage module 500, measure the temperature distribution, and predict the temperature distribution in the power storage module 500 based on the actual measurement.

[0066] In a preferred embodiment, first, a plurality of power storage devices for a preliminary test, which are different from the first power storage device 110 and the second power storage device 120 produced in the preparation step, are prepared, and a temperature sensor is attached to each of them. Next, a power storage module for a preliminary test simulating the power storage module 500 is assembled using the plurality of power storage devices for the preliminary test. Next, the plurality of power storage devices for the preliminary test are actually charged and discharged (preferably at a high rate), and the temperature distribution at this time is predicted. The charge and discharge conditions are preferably conditions that assume the actual use mode. Then, based on the obtained temperature distribution, the temperature distribution within the power storage module 500 is predicted, and the power storage module 500 is divided (e.g., divided into two), for example, into a low-temperature region A1 and a high-temperature region A2.

[0067] (Step C) In the construction step, a first electricity storage device 110 and a second electricity storage device 120 are arranged based on the temperature distribution predicted in the temperature distribution prediction step to construct an electricity storage module 500. Specifically, the first electricity storage device 110, whose negative electrode active material layer 24a has a relatively low peak intensity ratio, is arranged in an area designated as the low temperature region A1, and the second electricity storage device 120, whose negative electrode active material layer 24a has a relatively high peak intensity ratio, is arranged in an area designated as the high temperature region A2. Then, the first electricity storage device 110 and the second electricity storage device 120 are restrained and integrally held together by a restraining mechanism 300, for example, together with a plurality of spacers 200. In this manner, the electricity storage module 500 can be constructed.

[0068] [Uses of energy storage modules] The power storage module 500 can be used for a variety of purposes, but because it has excellent high-rate durability, it can be suitably used in purposes requiring high output, such as a power source (driving power source) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, and examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). Mounting the power storage module 500 on a moving object such as a vehicle can improve the fuel efficiency (electricity cost) of the moving object.

[0069] Some test examples relating to the present invention will be described below, but it is not intended that the present invention be limited to these test examples.

[0070] In this test example, electricity storage devices were constructed with different types of graphite as the negative electrode active material and / or different peak intensity ratios of the negative electrode active material layer, and their high-rate durability was confirmed. Specifically, first, a negative electrode composite paste was prepared using the types of graphite shown in Table 1, and negative electrodes (Examples 1 to 5) were fabricated. Note that in Examples 3 and 5, a magnetic field was applied with magnetic field lines oriented in the normal direction of the negative electrode current collector before the negative electrode composite paste dried. The application conditions were a magnetic flux density of 500 mT and an application time of 3 seconds. In this way, a negative electrode equipped with a negative electrode active material layer was fabricated.

[0071] The obtained negative electrode active material layer was measured using a commercially available X-ray diffraction device, and the peak intensity ratio (I 004 / I 110 Specifically, X-rays were applied from the normal direction of the negative electrode current collector, and measurements were carried out under the following conditions. The peak intensity ratio between the (110) plane and the (004) plane was then calculated. Measurement device: Ultima IV (Rigaku Corporation) X-ray source: CuKα ray Measurement range: 5 to 90° Step width: 0.02° Slits: Divergence slit = 1 degree, receiving slit = 0.1 mm, scattering slit = 1 degree

[0072] Next, a wound electrode body was produced using the produced negative electrodes (Examples 1 to 5), and electricity storage devices (lithium ion secondary batteries, Examples 1 to 5) were constructed. Note that the configurations other than those described above (the type of graphite and / or the peak intensity ratio of the negative electrode active material layer) were common to all electricity storage devices. Next, in a temperature environment of 25°C, the electricity storage devices were adjusted to a state of SOC 50%, and constant current discharge was performed at 150 A for 10 seconds, and the discharge resistance was measured. Next, the battery voltage ΔV that had dropped over 10 seconds was read, and the IV resistance (initial resistance) was calculated based on the battery voltage ΔV and the discharge current value (150 A).

[0073] Next, the energy storage device was adjusted to a 50% SOC state in a 25°C temperature environment, and subjected to 1000 cycles of constant-current charging at a charge rate of 150 A for 10 seconds, followed by a 5-second pause, followed by a 10 A discharge rate for 150 seconds, followed by a 5-second pause. This cycle constituted one charge / discharge cycle, and a high-rate durability test was performed. 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. Table 1 shows relative values, with the resistance increase rate of Example 2 set to 1.00 (reference).

[0074] [Table 1]

[0075] As shown in Table 1, when comparing Examples 3 and 5, in which a magnetic field was applied before the negative electrode composite paste dried, with Examples 1 and 2, in which a magnetic field was not applied, the peak intensity ratio was significantly reduced by applying a magnetic field. This shows that the peak intensity ratio can be adjusted by applying a magnetic field. In more detail, by applying a magnetic field, the direction of the hexagonal mesh plane of the graphite becomes perpendicular to the negative electrode current collector, and the I 004 becomes smaller (I 100It was found that as a result of this, the peak intensity ratio decreased. Furthermore, when Example 4, which used artificial graphite, was compared with Examples 1 and 2, which used natural graphite, the peak intensity ratio was relatively low when artificial graphite was used. Therefore, it was found that the peak intensity ratio could be adjusted by changing the type of graphite (the crystal orientation of the graphite itself).

[0076] Furthermore, the lower the peak intensity ratio of the negative electrode active material layer, the smaller the increase in resistance after the high-rate durability test, i.e., the higher the high-rate durability. While not intended to be a particularly restrictive interpretation, one possible reason for this is that the lower the peak intensity ratio of the negative electrode, the less likely the negative electrode is to expand and contract in the thickness direction, particularly during high-rate charge and discharge, thereby suppressing the discharge of electrolyte from both ends of the wound electrode assembly in the winding direction. From the above, the experimental results also support the idea that energy storage devices with a low peak intensity ratio of the negative electrode active material layer have relatively better high-rate durability than energy storage devices with a high peak intensity ratio of the negative electrode active material layer.

[0077] Although the preferred embodiment of the present invention has been described above, the above embodiment is merely an example. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modifications, or to add other modifications to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0078] (1) For example, in the above-described embodiment, in the preparation step (step A), a magnetic field was applied to the first negative electrode for the first power storage device 110 to adjust (specifically, reduce) the peak intensity ratio of the negative electrode active material layer 24a. However, this is not limited to this. As described in the above test example, when the types of negative electrode active materials (particularly the crystalline orientation of the graphite itself) differ between the first negative electrode and the second negative electrode, specifically when the negative electrode composite paste for the first negative electrode and the negative electrode composite paste for the second negative electrode are prepared separately, the application of a magnetic field to the first negative electrode may be omitted.

[0079] (2) For example, in the above-described embodiment, in the preparation step (Step A), the electricity storage devices 100 are manufactured in which the peak intensity ratios of the negative electrode active material layers 24a are intentionally varied. However, this is not limited to this. For example, the first electricity storage device 110 and the second electricity storage device 120 may be prepared by selecting the first electricity storage device 110 and the second electricity storage device 120 within a predetermined range of acceptable products from among a large number of electricity storage devices in which the peak intensity ratios of the negative electrode active material layers 24a vary.

[0080] A specific example is when a used electricity storage device (which may be in the form of an electricity storage module) is collected from the market and reused, i.e., when the electricity storage device 100 is a reused product. In recent years, electricity storage devices such as lithium ion secondary batteries have been provided with identification information from the perspective of traceability, etc. In one example, an optical symbol that can be read by a reading device is provided on the surface of the electricity storage module (e.g., sealing plate 14). Alternatively, a small substrate containing identification information is mounted inside the electricity storage device, etc. The identification information may include, for example, ID information such as the model number, manufacturer name, country of manufacture, name of manufacturing plant, and date of manufacture, as well as material information such as the type of negative electrode active material.

[0081] In this case, the (Step A) preparation step may include: (Aa) an acquisition step of reading out the identification information attached to each of the many collected electricity storage devices to acquire information on the type of negative electrode active material; and (Ab) a selection step of selecting, based on the acquired information on the type of negative electrode active material, a first electricity storage device 110 having a relatively low peak intensity ratio in the negative electrode active material layer 24a (e.g., containing artificial graphite) from a second electricity storage device 120 having a relatively high peak intensity ratio in the negative electrode active material layer 24a (e.g., containing natural graphite). This electricity storage module manufacturing method may also be understood as a method for reusing electricity storage devices. In this specification, the term "optical symbol" is a general term for an information medium that stores information by combining areas with high and low optical reflectance, and is a concept that encompasses two-dimensional symbols (also referred to as two-dimensional codes, two-dimensional barcodes, etc.) such as QR Code (registered trademark), data matrix, and data tag.

[0082] (3) For example, in the embodiment of FIG. 5 described above, both ends in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 5 ) are low-temperature regions A1 where the temperature is relatively low, and the center portion in the arrangement direction X is a high-temperature region A2 where the temperature is relatively high. However, this is not limited to this. As described above, the temperature distribution in the power storage module 500 can vary depending on the configuration of the cooling device 400 (for example, the installation positions and number of the air intake port IP, the air exhaust port OP, and the air-cooling fans 410), the number of power storage devices 100, the charge / discharge conditions, etc. Furthermore, in the embodiment of FIG. 5 described above, the power storage module 500 is divided into two temperature regions, the low-temperature region A1 and the high-temperature region A2, and further, the temperature distribution is symmetrical in the arrangement direction X. However, this is not limited to this. For example, the power storage module 500 may be divided into three or more temperature regions. In this case, in the embodiment of Fig. 5, the low temperature region A1 on the rear Rr side in the arrangement direction X may be made into a medium temperature region A3, which has a temperature higher than that of the low temperature region A1 and a temperature lower than that of the high temperature region A2. Furthermore, when 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. Some specific modified examples will be described below with reference to Figs. 6 to 9. Note that the cooling device is not shown in Figs. 6 to 9.

[0083] (First Modification) FIG. 6 is a plan view of a power storage module 500a according to a first modification. As described above, it is known that chain heat generation between the power storage devices 100 is likely to occur in the central portion of the arrangement direction X. For this reason, although not shown in FIG. 6, an air intake port IP and / or an air-cooling fan 410 through which a refrigerant (air) is supplied may be additionally installed in the central portion of the arrangement direction X to strongly cool the central portion. In this case, as shown in FIG. 6, the temperature distribution of the power storage module 500a is opposite to that in FIG. 5, with the central portion of the arrangement direction X becoming a low-temperature region A1 with a relatively low temperature, and both ends of the arrangement direction X (the front portion F and the rear portion Rr in FIG. 6) becoming high-temperature regions A2 with a relatively high temperature.

[0084] In such a case, as shown in FIG. 6, it is preferable to arrange a first electricity storage device 110 having a relatively low peak intensity ratio of the negative electrode active material layer 24a (high high-rate resistance) in the center of the arrangement direction X, which is the low-temperature region A1, and to arrange a second electricity storage device 120 having a relatively high peak intensity ratio of the negative electrode active material layer 24a (low high-rate resistance) at both ends of the arrangement direction X, which are the high-temperature regions A2.

[0085] (Second and Third Modifications) Fig. 7 is a plan view of a power storage module 500b according to a second modification. Fig. 8 is a plan view of a power storage module 500c according to a third modification. For example, if the air-cooling fan 410 installed on the front F side in the arrangement direction X in Fig. 5 is powerful and has high cooling capacity, the temperature distribution in the power storage modules 500b and 500c may be such that the front F part in the arrangement direction X becomes a low-temperature region A1 where the temperature is relatively low, and the rear Rr part in the arrangement direction X becomes a high-temperature region A2 where the temperature is relatively high, as shown in Figs. 7 and 8, respectively.

[0086] In such a case, as shown in Figures 7 and 8, it is preferable to arrange a first electricity storage device 110 having a relatively low peak intensity ratio of the negative electrode active material layer 24a (high high-rate resistance) in the front F part in the arrangement direction X, which is the low-temperature region A1, and to arrange a second electricity storage device 120 having a relatively high peak intensity ratio of the negative electrode active material layer 24a (low high-rate resistance) in the rear Rr part in the arrangement direction X, which is the high-temperature region A2.

[0087] Furthermore, the distribution of the low temperature region A1 and the high temperature region A2 may differ depending on, for example, the number of power storage devices 100, the charge / discharge conditions, etc. Therefore, the low temperature region A1 and the high temperature region A2 may be uniformly provided in the arrangement direction X as shown in Fig. 7, or may be non-uniformly provided in the arrangement 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.

[0088] (Fourth Modification) Fig. 9 is a plan view of a power storage module 500d according to a fourth modification. As shown in Fig. 9, the temperature distribution of the power storage module 500d is divided into more detailed sections than in Fig. 5. That is, both ends in the arrangement direction X (the front F section and the rear Rr section in Fig. 6) are low-temperature regions A1 with relatively low temperatures, the central section in the arrangement 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 the low-temperature region A1 and lower than the high-temperature region A2.

[0089] 9 , it is preferable to arrange a first electricity storage device 110 having a relatively low peak intensity ratio of the negative electrode active material layer 24a (high high-rate resistance) at both ends in the arrangement direction X, which are the low-temperature regions A1, a second electricity storage device 120 having a relatively high peak intensity ratio of the negative electrode active material layer 24a (low high-rate resistance) at the center in the arrangement direction X, which is the high-temperature region A2, and a third electricity storage device 130 having a lower peak intensity ratio of the negative electrode active material layer 24a than the second electricity storage device 120 and a higher peak intensity ratio of the negative electrode active material layer 24a than the first electricity storage device 110 in the medium-temperature region A3 between the low-temperature region A1 and the high-temperature region A2. In other words, it is preferable to arrange the multiple electricity storage devices 100 so that the peak intensity ratio of the negative electrode active material layer 24a gradually decreases in the order of the high-temperature region A2, the medium-temperature region A3, and the low-temperature region A1, in this case from the center toward both ends in the arrangement direction X.

[0090] 9, the inside of the power storage module 500 is divided into three temperature zones, but it is of course possible to divide it into four or more temperature zones. By dividing the inside of the power storage module 500 into smaller zones according to the temperature distribution in this way, the effects of the technology disclosed herein can be exerted to a high level, and the high-rate resistance of the entire power storage module 500 can be further improved.

[0091] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: An electricity storage module including a plurality of electricity storage devices, wherein each of the plurality of electricity storage devices has a positive electrode and a negative electrode, and the negative electrode has a negative electrode active material layer containing graphite, and the electricity storage module includes a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high during charging and discharging of the plurality of electricity storage devices, and wherein, when the negative electrode active material layer is measured by X-ray crystal structure analysis, a peak intensity I 110 The peak intensity I originating from the (004) plane of the graphite 004 The ratio (I 004 / I 110) is a peak intensity ratio, a first power storage device arranged in the low temperature region among the plurality of power storage devices has a lower peak intensity ratio than a second power storage device arranged in the high temperature region. Item 2: The energy storage module according to Item 1, wherein the energy storage module includes, between the low temperature region and the high temperature region, a medium temperature region that is higher in temperature than the low temperature region and lower in temperature than the high temperature region, and the plurality of energy storage devices are arranged such that the peak intensity ratio of the negative electrode active material layer decreases stepwise in the order of the high temperature region, the medium temperature region, and the low temperature region. Item 3: The electricity storage module according to item 1 or 2, wherein the difference in the peak intensity ratio of the negative electrode active material layer between the first electricity storage device and the second electricity storage device is 0.5 or more. Item 4: The electricity storage module according to any one of Items 1 to 3, wherein the peak intensity ratio of the negative electrode active material layer of each of the first electricity storage device and the second electricity storage device is in the range of 1 or more and 50 or less. Item 5: The electricity storage module according to any one of items 1 to 4, wherein the first electricity storage device contains artificial graphite as the graphite, and the second electricity storage device contains natural graphite as the graphite. Item 6: The power storage module according to any one of Items 1 to 5, wherein the first power storage device and the second power storage device are connected in series. Item 7: A method for producing an electricity storage module, comprising a plurality of electricity storage devices, each of the plurality of electricity storage devices having a positive electrode and a negative electrode, and the negative electrode having a negative electrode active material layer containing graphite, wherein when the negative electrode active material layer is measured by X-ray crystal structure analysis, a peak intensity I 110 The peak intensity I originating from the (004) plane of the graphite 004 The ratio (I 004 / I 110) is a peak intensity ratio, the plurality of electricity storage devices including a first electricity storage device having a negative electrode active material layer with a relatively low peak intensity ratio and a second electricity storage device having a negative electrode active material layer with a relatively high peak intensity ratio; a temperature distribution prediction step of predicting a temperature distribution in the electricity storage module when the plurality of electricity storage devices are charged and discharged; and a construction step of constructing the electricity storage module by arranging the first electricity storage device in a low-temperature region with a relatively low temperature and the second electricity storage device in a high-temperature region with a relatively high temperature based on the temperature distribution. Item 8: The manufacturing method according to Item 7, wherein the preparation step includes a first negative electrode preparation step of preparing a negative electrode for the first electricity storage device, and the first negative electrode preparation step includes an application step of applying a paste-like negative electrode composite containing the graphite onto a negative electrode current collector, and a magnetic field application step of applying a magnetic field to the negative electrode composite before the negative electrode composite on the negative electrode current collector solidifies, thereby orienting the graphite. [Explanation of symbols]

[0092] 10 Battery case 20 Electrode body 24 Negative electrode 100 Energy storage device 110 First electricity storage device 120 Second power storage device 130 Third Energy Storage Device 300 Restraint mechanism 400 Cooling device 410 Air-cooled fan 500 Energy Storage Module A1 Low temperature region A2 High temperature area A3 Medium temperature range

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 and a negative electrode, the negative electrode includes a negative electrode active material layer containing graphite, the power storage module includes a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high when the power storage devices are charged or discharged, Here, when the negative electrode active material layer is measured by X-ray crystal structure analysis, the peak intensity I １１０ The peak intensity I originating from the (004) plane of the graphite ００４ The ratio (I ００４ / I １１０ ) is the peak intensity ratio, Among the plurality of power storage devices, a first power storage device arranged in the low temperature region has a lower peak intensity ratio than a second power storage device arranged in the high temperature region. Energy storage module.

2. a medium temperature region between the low temperature region and the high temperature region within the energy storage module, the medium temperature region having a temperature 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 peak intensity ratio of the negative electrode active material layer decreases stepwise in the order of the high temperature region, the medium temperature region, and the low temperature region; The energy storage module according to claim 1 .

3. a difference between the peak intensity ratios of the negative electrode active material layers of the first electricity storage device and the second electricity storage device is 0.5 or more; The energy storage module according to claim 1 .

4. the peak intensity ratio of the negative electrode active material layer of each of the first and second electricity storage devices is in the range of 1 or more and 50 or less; The energy storage module according to claim 1 .

5. the first electricity storage device includes artificial graphite as the graphite, The second electricity storage device contains natural graphite as the graphite. The energy storage module according to claim 1 .

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

7. A method for manufacturing an electricity storage module including a plurality of electricity storage devices, each of the plurality of electricity storage devices having a positive electrode and a negative electrode, and the negative electrode including a negative electrode active material layer containing graphite, Here, when the negative electrode active material layer is measured by X-ray crystal structure analysis, the peak intensity I １１０ The peak intensity I originating from the (004) plane of the graphite ００４ The ratio (I ００４ / I １１０ ) is the peak intensity ratio, a preparation step of preparing, as the plurality of electricity storage devices, a first electricity storage device having a negative electrode active material layer with a relatively low peak intensity ratio and a second electricity storage device having a negative electrode active material layer with a relatively high peak intensity ratio; 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 low-temperature region having a relatively low temperature and arranging the second power storage device in a high-temperature region having a relatively high temperature based on the temperature distribution; Including, A method for manufacturing a storage module.

8. the preparing step includes a first negative electrode fabricating step of fabricating a negative electrode for the first electricity storage device, the first negative electrode preparation step includes: an application step of applying a paste-like negative electrode composite material containing the graphite onto a negative electrode current collector; and a magnetic field application step of applying a magnetic field to the negative electrode composite material before the negative electrode composite material on the negative electrode current collector is solidified, thereby orienting the graphite. A method for manufacturing the electricity storage module according to claim 7 .

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