JP7763207B2 - Energy storage module and manufacturing method thereof - Google Patents

Description

The present invention relates to an energy storage module equipped with multiple energy storage devices and a manufacturing method thereof.

Conventionally, energy storage modules consisting of multiple electrically connected energy storage devices (single cells) have been widely used in vehicle drive power sources and the like. Patent Document 1 is an example of a related prior art document.

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 contains an area that is prone to relatively low temperatures, and submodules arranged in this area are configured so that the restraining pressure of the restraining member is relatively lower than that of other submodules. Patent Document 1 describes how, by reducing the restraining pressure on the energy storage devices in areas where high-rate resistance is likely to decrease (areas prone to low temperatures), it is possible to average out the high-rate resistance (increase in resistance when high-rate charging and discharging are repeated) of the multiple energy storage devices.

Japanese Patent Application Laid-Open No. 2021-44212 Japanese Patent Application Laid-Open No. 2019-021770 JP 2010-225366 A

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

The present invention was made in consideration of the above circumstances, and its main purpose is to provide a new energy storage module configuration that can equalize the high-rate resistance of multiple energy storage devices, as well as a manufacturing method for the same.

The present invention provides an energy storage module comprising a plurality of energy storage devices, each of which has a positive electrode and a negative electrode. The energy 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 energy storage devices are charged or discharged. If the ratio of the theoretical capacity per unit area of the negative electrode to the theoretical capacity per unit area of the positive electrode (negative electrode theoretical capacity/positive electrode theoretical capacity) is taken as the opposing capacity ratio, then the first energy storage device of the plurality of energy storage devices, located in the low-temperature region, has a higher opposing capacity ratio than the second energy storage device located in the high-temperature region.

The present invention also provides a method for manufacturing an energy storage module comprising a plurality of energy storage devices, each of which has a positive electrode and a negative electrode. This manufacturing method includes the following steps: a preparation step of preparing, as the plurality of energy storage devices, a first energy storage device having a relatively high opposing capacity ratio and a second energy storage device having a relatively low opposing capacity ratio, where the ratio of the theoretical capacity per unit area of the negative electrode to the theoretical capacity per unit area of the positive electrode (negative electrode theoretical capacity/positive electrode theoretical capacity) is the opposing capacity 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 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, based on the temperature distribution.

After extensive research, the inventors discovered that energy storage devices with a high opposing capacity ratio have relatively better high-rate resistance than energy storage devices with a low opposing capacity ratio. Therefore, in the present invention, energy storage devices with a relatively high opposing capacity ratio (excellent high-rate resistance) are placed in low-temperature regions where high-rate resistance is likely to decrease. This makes it possible to equalize the high-rate resistance of multiple energy storage devices. Ultimately, this improves the high-rate resistance of the entire energy storage module. Furthermore, unlike the technology of Patent Document 1, this technology is not limited to the framework of a "cell group," allowing for flexible adjustment of the high-rate resistance of individual energy storage devices. 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.

While not particularly related to the technology disclosed herein, Patent Documents 2 and 3 each describe electrode properties (e.g., porosity of the active material layer) and discharge capacity ratio ranges suitable for electricity storage devices.

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

Preferred embodiments of the technology disclosed herein will be described below, with appropriate reference to the 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 does not characterize the present invention) can be understood as design matters of a person 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.

In the drawings below, components and parts that perform the same function are given the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, in this specification, the notation "A to B" indicating a range means greater than or equal to A and less than or equal to B, as well as "preferably greater than A" and "preferably smaller than B." Furthermore, in this specification, the notation "equal" does not necessarily refer to an exact match; for example, a variation of approximately ±5% (due to manufacturing errors, etc.) is acceptable.

[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.

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 of the energy storage device 100, the long side direction perpendicular to the short side direction, and the up-down direction, respectively. 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 explanation and do not in any way limit the installation form of the energy storage module 500.

The restraining mechanism 300 is a member that restrains multiple energy storage devices 100. In this embodiment, there is only one restraining mechanism 300. The restraining mechanism 300 is configured to apply equal restraining pressure to all of the energy storage devices 100 and 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 multiple screws 330. The pair of end plates 310 and the pair of side plates 320 can also be understood as a housing that houses multiple energy storage devices 100. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal.

A 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 a plurality of energy storage devices 100 and a plurality of spacers 200 in the arrangement direction X. A pair of side plates 320 bridges 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 applies a uniform restraining load to the plurality of energy storage devices 100 in the arrangement direction X, holding the plurality of energy storage devices 100 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, binding bars, etc. instead of the side plates 320.

Here, the spacers 200 are arranged between the multiple energy storage devices 100 in the arrangement direction X. That is, the energy storage devices 100 and the spacers 200 are arranged alternately in the arrangement direction X. However, if the energy storage module 500 does not include spacers 200, the energy storage devices 100 adjacent to each other in the arrangement direction X may be in abutting contact (direct contact). The spacers 200 preferably include a porous structure portion that allows fluid (typically, a gas such as air) to pass through.

The power storage device 100 is a device that can be repeatedly charged and discharged. In this specification, the term "power storage device" 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 power 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 power storage device 100). The multiple power storage devices 100 are preferably restrained by a restraining mechanism 300. The shape, size, number, etc. of the multiple power storage devices 100 are not limited to the embodiment disclosed in FIG. 1 and can be modified as appropriate.

Although not shown 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 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, multiple energy storage devices 100 are connected in series. This makes it possible to suitably improve output characteristics to a level suitable for use in mobile objects such as vehicles. Furthermore, in the case of a series connection, performance degradation of some 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.

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 flat, rectangular, and have the same shape here. The multiple energy storage devices 100 are arranged so that their long side walls 12b, described below, are parallel to each other. Here, the multiple energy storage devices 100 are lined up in the arrangement direction X with the long side walls 12b facing each other via spacers 200.

Figure 3 is a schematic longitudinal cross-sectional view taken along line III-III in Figure 2. As shown in Figure 3, the electricity storage device 100 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 further includes a non-aqueous electrolyte. The electricity storage device 100 is configured by housing the electrode assembly 20 and 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 in this case, a lithium-ion secondary battery. When the electricity storage device 100 is a non-aqueous electrolyte secondary battery (particularly a lithium-ion secondary battery), applying the technology disclosed herein is particularly effective.

The battery case 10 is a container that houses the electrode assembly 20 and nonaqueous electrolyte. As shown in FIG. 2, the battery case 10 has a flat, bottomed, rectangular (square) 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, aluminum alloy, iron, iron alloy, etc. 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.

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 cover the opening 12h of the exterior body 12. The battery case 10 is integrated by joining (preferably welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed (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 vertical direction Z.

The positive electrode terminal 30 is located at one end of the sealing plate 14 in the long side direction Y (left end in Figures 2 and 3), and the negative electrode terminal 40 is located at the other end of the sealing plate 14 in the long side direction Y (right end in Figures 2 and 3). As shown in Figure 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 outlet 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 outlet holes 18 and 19 by crimping. Crimped portions 30c and 40c are formed on the ends of the positive electrode terminal 30 and the negative electrode terminal 40 on the exterior body 12 side (lower end in Figure 3). This secures the positive electrode terminal 30 and the negative electrode terminal 40 to the sealing plate 14.

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 the 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 the 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 a gasket 90.

As shown in Figures 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 energy 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. For example, the energy storage module 500 is connected in series by electrically connecting the positive electrode external conductive member 32 of one of the energy storage devices 100 adjacent to each other in the arrangement direction X with the negative electrode external conductive member 42 of the other energy storage device 100 via a bus bar or the like.

Figure 4 is a schematic diagram showing the configuration of the electrode assembly 20. As shown in Figure 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 them 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 approximately 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 approximately parallel to the vertical direction Z. Furthermore, the electrode assembly 20 may be a stacked electrode assembly formed by stacking multiple square-shaped (typically rectangular) positive electrodes and multiple square-shaped (typically rectangular) negative electrodes in an insulated state.

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 adhered to at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is preferably made of metal, and more preferably made of metal foil. Here, the positive electrode current collector 22c is aluminum foil.

A plurality of positive electrode tabs 22t are provided at one end of the positive electrode current collector 22c in the long side direction Y (left end in Figure 4). The multiple positive electrode tabs 22t protrude toward one side in the long side direction Y (left end in Figure 4). The multiple positive electrode tabs 22t protrude further in the long side direction Y than the separator 26. In this example, the positive electrode tabs 22t are 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 (left end in Figure 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.

The positive electrode active material layer 22a is provided in a strip shape on one or both sides (both sides in this example) of the positive electrode current collector 22c, extending 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 absorbing and releasing charge carriers. Examples of positive electrode active materials include lithium transition metal composite oxides and lithium transition metal phosphate compounds. The lithium transition metal composite oxide preferably contains at least one of Ni, Co, and Mn as a transition metal element. Specific examples of lithium transition metal composite oxides include lithium nickel composite oxides, lithium cobalt composite oxides, lithium manganese composite oxides, lithium nickel manganese composite oxides, lithium nickel cobalt manganese composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium iron nickel manganese composite oxides. Of these, lithium nickel cobalt manganese composite oxides are preferred. The positive electrode active materials may be used alone or in combination.

In this specification, the term "lithium nickel cobalt manganese composite oxide" encompasses oxides containing Li, Ni, Co, Mn, and O as constituent elements, as well as oxides containing one or more additional elements. Examples of additional elements include transition metal elements and typical metal elements such as Mg, Ca, Al, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, Na, Fe, Zn, and Sn. The additional element may also be a metalloid element such as B, C, Si, or P, or a non-metal element such as S, F, Cl, Br, or I. This also applies to the lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel manganese composite oxide, lithium nickel cobalt aluminum composite oxide, and lithium iron nickel manganese composite oxide.

Although not particularly limited, the proportion of the positive electrode active material in the positive electrode active material layer 22a is preferably 80% by mass or more, and more preferably 90 to 99% by mass. 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 binders and conductive materials. Examples of binders include polyvinylidene fluoride (PVdF). Examples of conductive materials include carbon materials such as carbon black. Although not particularly limited, in an energy storage module 500 to be mounted on a mobile object such as a vehicle, the thickness of the positive electrode active material layer 22a (average thickness per surface of the positive electrode current collector 22c) is, for example, 10 to 300 μm, and preferably 20 to 200 μm.

Although not particularly limited, in an energy storage module 500 to be mounted on a mobile object such as a hybrid electric vehicle (HEV), the width of the positive electrode active material layer 22a in the winding axis WL direction (average value, excluding the portion formed on the positive electrode tab 22t), in other words, the length Lp in the width direction Y, is preferably 5 cm or more, more preferably 9 cm or more, and even more preferably, for example, 10 cm or more, 15 cm or more, 20 cm or more, or 25 cm or more. The length Lp may be, for example, 100 cm or less, 50 cm or less, or 30 cm or less.

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 additives, etc.

The configuration of the negative electrode 24 may be the same as that of a conventional negative electrode. 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 made of metal foil. Here, the negative electrode current collector 24c is copper foil.

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 tabs 24t are part of the negative electrode current collector 24c and are 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 located symmetrically 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.

The negative electrode active material layer 24a is provided in a strip shape on one or both sides (both sides in this example) of the negative electrode current collector 24c, along the longitudinal direction of the negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material that can reversibly store and release charge carriers. Examples of negative electrode active materials include carbon materials such as graphite, hard carbon, and soft carbon, as well as compounds containing silicon (Si-containing materials). The graphite may be natural graphite or artificial graphite, or it may be amorphous carbon-coated graphite, in which graphite is coated with an amorphous carbon material.

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 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 additives such as binders, thickeners, and dispersants. Examples of binders include styrene butadiene rubber (SBR) and polyvinylidene fluoride (PVdF). Examples of thickeners include carboxymethyl cellulose (CMC). Although not particularly limited, the thickness of the negative electrode active material layer 24a (average thickness per surface of the negative electrode current collector 24c) is, for example, 10 to 400 μm, and preferably 20 to 300 μm, in a power storage module 500 to be mounted on a mobile object such as a vehicle.

The width of the negative electrode active material layer 24a in the winding axis WL direction (average value, excluding the portion formed on the negative electrode tab 24t), in other words, the length Ln in the width direction Y, is preferably the same as or longer than the length Lp of the positive electrode active material layer 22a, as shown in Figure 4. From the perspective of balancing high capacity and high output, the length Ln is preferably 5 cm or more, more preferably 9 cm or more, and even more preferably, for example, 10 cm or more, 15 cm or more, 20 cm or more, or 25 cm or more. The length Ln may be, for example, 100 cm or less, 50 cm or less, or 30 cm or less.

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.

The configuration of the non-aqueous electrolyte may be the same as that of a conventional non-aqueous electrolyte. 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 (LiPF ₆ ) or lithium bis(fluorosulfonyl)imide (LiFSI). The non-aqueous electrolyte may further contain additives as necessary. The non-aqueous electrolyte is typically liquid, but may also be gel-like. In 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.

Figure 5 is a plan view schematically showing the energy storage module 500 and the cooling device 400. Note that detailed illustration of the spacer 200 and the top surface of the energy storage device 100 is omitted in Figure 5. As shown in Figure 5, the cooling device 400 here 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 here is an air-cooled cooling device that uses air as a refrigerant. However, in other embodiments, the cooling device 400 may be a liquid-cooled cooling device that uses a liquid refrigerant.

In this embodiment, the air intake port IP is provided on one side (front F side) of the power storage module 500 in the arrangement direction X. The air exhaust port OP is provided on the other side (rear Rr side) in the arrangement direction X. The air-cooled fan 410 is attached to the air intake port IP. The air-cooled fan 410 is configured to send wind (air) to the air intake port IP. The configuration of the air-cooled fan 410 is not limited, but may include, for example, an electric motor (not shown). The temperature sensor 420 is located 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.

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 or exceeded a predetermined first temperature, the control device 430 operates the air-cooling fan 410. This allows low-temperature air from outside the power storage module 500 to be supplied into the power storage module 500 through the air intake port IP, creating an air flow AF within 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 or exceeded a predetermined second temperature, the control device 430 stops the air-cooling fan 410. This air-cooling type cooling device 400 allows the power storage device 100 to be cooled at low cost.

According to the inventors' investigations, a temperature distribution occurs inside an energy storage module 500 equipped with a cooling mechanism such as the cooling device 400 during charging and discharging of multiple energy storage devices 100, 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 the energy storage devices 100 generate heat during charging and discharging, adjacent energy storage devices 100 heat each other. This causes a chain reaction of heat generation between the energy storage devices 100 in the central portion of the arrangement direction X, making the temperature relatively high. On the other hand, the ends of the arrangement direction X (the front portion F and the rear portion Rr in Figure 5) have higher heat dissipation properties than the central portion, making chain reaction of heat generation less likely to occur. Therefore, the temperatures at both ends of the arrangement direction X tend to be relatively low.

In particular, in this embodiment, the intake port IP and air-cooled fan 410, through which refrigerant (air) is supplied, are arranged on the front F side of the arrangement direction X, and the exhaust port OP is arranged on the rear Rr side of the arrangement direction X. As a result, both ends of the arrangement direction X tend to be cold. As a result, the center of the arrangement direction X becomes a high-temperature area A2 with a relatively high temperature, and both ends of the arrangement direction X (the front F part and rear Rr part in Figure 5) tend to become low-temperature areas A1 with a relatively low temperature. In particular, the front F part of the arrangement direction X, where the intake port IP and air-cooled fan 410 are arranged, tends to be the coldest. In other words, in this embodiment, at least the front F side of the arrangement direction X tends to become a low-temperature area A1 with a relatively low temperature.

As described in Patent Document 1, for example, when temperature distribution occurs within the energy storage module 500, variations in the high-rate resistance of the energy storage device 100 can occur. Specifically, the high-rate resistance of the energy storage device 100 can be reduced 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 resistance of the energy storage device 100 in the low-temperature region A1, the high high-rate resistance of the energy storage device 100 in the high-temperature region A2 cannot be fully utilized. On the other hand, if the high-rate resistance of the energy storage device 100 in the high-temperature region A2 is used as the standard, a high voltage is applied to the energy storage device 100 in the low-temperature region A1, which is likely to accelerate high-rate degradation. When temperature distribution occurs within the energy storage module 500, the high-rate resistance of the entire energy storage module 500 may be affected by the high-rate resistance of the energy storage device 100 in the low-temperature region A1, potentially reducing the high-rate resistance of the entire energy storage module 500. Furthermore, when the energy storage module is installed in a moving object such as a vehicle, fuel economy may be reduced.

Therefore, the technology disclosed herein uses, as the multiple power storage devices 100, a first power storage device 110 and a second power storage device 120 having mutually different opposing capacity ratios between the positive electrode 22 and the negative electrode 24. The first power storage device 110 has a higher opposing capacity ratio than the second power storage device 120. As will be described in detail later, the inventors' studies have confirmed that the higher the opposing capacity ratio of a power storage device 100, the higher its high-rate resistance. Therefore, in this embodiment, a first power storage device 110 having a relatively high opposing capacity ratio (high high-rate resistance) is arranged in a low-temperature region A1 where the temperature is relatively low, in this case, at both ends in the arrangement direction X (the front portion F and the rear portion Rr in Figure 5). Furthermore, a second power storage device 120 having a relatively low opposing capacity ratio (low high-rate resistance) is arranged in a high-temperature region A2 where the temperature is relatively high, in this case, at the center in the arrangement direction X.

With this configuration, the high-rate resistance of the multiple energy storage devices 100 can be equalized to a high level. This in turn suppresses accelerated degradation and improves the high-rate resistance of the entire energy 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 energy storage devices 100 can be flexibly adjusted according to the temperature distribution within the energy storage module 500. Therefore, it may be possible to equalize the high-rate resistance of the multiple energy storage devices 100 with higher accuracy than with the technology of Patent Document 1. Furthermore, because 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.

The opposing capacity ratio is the ratio of the theoretical capacity per unit area of the negative electrode 24 (mAh/cm ² ) to the theoretical capacity per unit area of the positive electrode 22 (mAh/cm ² ) (negative electrode theoretical capacity/positive electrode theoretical capacity), and is typically a value calculated for the opposing portion where the positive electrode active material layer 22a and the negative electrode active material layer 24a face each other (here, the region of width Lp of the positive electrode active material layer 22a) by the following formula: opposing capacity ratio = {mass of negative electrode active material per unit area of the negative electrode 24 (g/cm ² ) × theoretical electrical capacity of negative electrode active material (mAh/g)} / {mass of positive electrode active material per unit area of the positive electrode 22 (g/cm ² ) × theoretical electrical capacity of positive electrode active material (mAh/g)}. The theoretical electric capacity (or a method for calculating the same) of the positive electrode active material and the negative electrode active material is publicly known, for example, the theoretical electric capacity of graphite is 372 mAh/g. The mass of the positive electrode active material and the mass of the negative electrode active material per unit area are preferably average values in the region where the positive electrode 22 and the negative electrode 24 face each other.

As is clear from the above formula, the face-to-face capacity ratio can be adjusted, for example, during the manufacture of the positive electrode 22 and/or negative electrode 24, by changing the mass of the positive electrode active material layer 22a per unit area of the positive electrode current collector 22c (basis weight of the positive electrode active material layer 22a) and/or the mass of the negative electrode active material layer 24a per unit area of the negative electrode current collector 24c (basis weight of the negative electrode active material layer 24a). When there are multiple first electricity storage devices 110 and multiple second electricity storage devices 120, as in this embodiment, it is preferable that all of the multiple first electricity storage devices 110 have a relatively higher face-to-face capacity ratio than the multiple second electricity storage devices 120.

While not particularly limited, in a power storage module 500 to be mounted on a mobile object such as a vehicle, from the perspective of achieving a high level of balance between energy density and high-rate resistance, the first power storage device 110 and the second power storage device 120 both have a counter-capacity ratio that is typically 1.0 or greater, and preferably in the range of approximately 1.0 to 2.0. In particular, for a high-output power storage module 500 to be mounted on a hybrid electric vehicle (HEV), the counter-capacity ratio is more preferably in the range of 1.2 to 1.9, for example, 1.3 to 1.8. However, for a high-capacity power storage module 500 to be mounted on a battery electric vehicle (BEV), energy density is prioritized, so the counter-capacity ratio may be approximately 1.0 to 1.2. By setting the counter-capacity ratio at a predetermined value or greater, the high-rate charging characteristics of the power storage module 500 can be improved.

Although this depends on the temperature distribution within the energy storage module 500, in a high-output energy storage module 500 such as that installed in a hybrid electric vehicle (HEV), the first energy storage device 110 preferably has a counter-current capacity ratio of approximately 1.0 to 2.0, for example, in the range of 1.6 to 1.9, and more preferably in the range of 1.7 to 1.8. The second energy storage device 120 preferably has a counter-current capacity ratio of approximately 1.0 to 1.8, for example, in the range of 1.4 to 1.7, and more preferably in the range of 1.5 to 1.6. By setting the counter-current capacity ratio to a predetermined value or higher, the high-rate charging characteristics of the energy storage module 500 can be improved.

The difference in the opposing capacity ratio between the first power storage device 110 and the second power storage device 120 is a design factor that is adjusted appropriately based on, for example, the temperature distribution within the power storage module 500. Therefore, although not particularly limited, in cases where the temperature distribution between the first power storage device 110 and the second power storage device 120 differs significantly, the difference in the opposing capacity ratio between the first power storage device 110 and the second power storage device 120 is preferably 10% or more, more preferably 15% or more, and may be, for example, 20% or more, 30% or more. By setting the difference in the opposing capacity ratio to a predetermined value or more, the effects of the technology disclosed herein can be more pronounced. The difference in the opposing capacity ratio may be, for example, 100% or less, or 50% 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. Note that when there are multiple first power storage devices 110 and multiple second power storage devices 120, the difference in opposing capacity ratio may be the difference between the average opposing capacity ratio of the multiple first power storage devices 110 and the average opposing capacity ratio of the multiple second power storage devices 120.

In one embodiment, the first power storage device 110 preferably has a larger coating weight of the negative electrode active material layer 24a than the second power storage device 120. That is, the negative electrode active material layer 24a of the first power storage device 110 is preferably configured so that the coating amount per unit area is relatively large (and therefore the thickness of the negative electrode active material layer 24a is typically relatively large) to, for example, increase the opposing capacity ratio, thereby resulting in a relatively high negative electrode theoretical capacity. The negative electrode active material layer 24a of the second power storage device 120 is preferably configured so that the coating amount per unit area is relatively small (and therefore the thickness of the negative electrode active material layer 24a is typically relatively small) to, for example, decrease the opposing capacity ratio, thereby resulting in a relatively low negative electrode theoretical capacity. Furthermore, the first electricity storage device 110 and the second electricity storage device 120 are preferably configured to have the same basis weight of the positive electrode active material layer 22a and the same positive electrode theoretical capacity (for example, a variation of about ±5% (manufacturing error, etc.) is acceptable). This allows the energy densities of the first electricity storage device 110 and the second electricity storage device 120 to be equalized, thereby achieving a high energy density for the electricity storage module 500 as a whole.

The specific values of the basis weights of the positive electrode active material layer 22a and the negative electrode active material layer 24a are design factors that are adjusted as appropriate depending on, for example, the application of the power storage module 500. Therefore, although not particularly limited, in a power storage module 500 that is mounted on a mobile body such as a vehicle, the basis weight of the positive electrode active material layer 22a of both the first power storage device 110 and the second power storage device 120 is preferably in the range of approximately 3 to 35 mg/cm ² , more preferably in the range of 4 to 30 mg/cm ² , for example, in the range of 5 to 25 mg/cm ^2. The basis weight of the negative electrode active material layer 24a is preferably in the range of approximately 3 to 25 mg/cm ² , more preferably in the range of 3.5 to 20 mg/cm ² , for example, in the range of 4 to 15 mg/cm ^2. The basis weight of the negative electrode active material layer 24a is preferably smaller than the basis weight of the positive electrode active material layer 22a. When active material layers are formed on both sides of the current collector, the above-mentioned value of the basis weight is the amount of the active material layer applied to one side.

[Method of manufacturing the energy storage module]
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 within 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 also include other steps at any stage.

In the (Step A) preparation step, a plurality of power storage devices 100 are prepared, including a first power storage device 110 with a relatively high counter-capacity ratio and a second power storage device 120 with a relatively low counter-capacity ratio. 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) a housing step of housing the electrode assembly 20 and a non-aqueous electrolyte solution in a battery case 10; and (A-4) a conditioning step.

(A-1) In the negative electrode preparation process, at least two types of negative electrodes 24 are prepared, each having a different basis weight of the negative electrode active material layer 24a. Specifically, a first negative electrode having a relatively high basis weight is prepared for the first power storage device 110, and a second negative electrode having a relatively low basis weight is prepared for the second power storage device 120. Specifically, for example, first, a negative electrode composite paste containing at least the negative electrode active material is prepared by dispersing the solid materials (e.g., negative electrode active material, binder, thickener, etc.) described above in a predetermined solvent (e.g., water, N-methyl-2-pyrrolidone, etc.). Next, the prepared negative electrode composite paste is applied to the surface of the negative electrode current collector 24c using a conventionally known coating device and dried. At this time, the basis weight of the negative electrode active material layer 24a can be adjusted by changing the amount of negative electrode composite paste applied per unit area. Thereafter, pressing, drying, and other processes may be performed as necessary. In this manner, a first negative electrode and a second negative electrode having negative electrode active material layers 24a with different coating weights can be produced.

(A-2) In the electrode assembly fabrication process, the first and second negative electrodes fabricated in the negative electrode fabrication process are wound up opposite a separately prepared positive electrode 22, with the separator 26 as described above interposed between them. 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.

(A-3) In the 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. This produces a battery assembly for the first power storage device 110 and a battery assembly for the second power storage device 120.

(A-4) In the conditioning step, the fabricated battery assembly is charged at least once. Preferably, the fabricated battery assembly 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. The battery case 10 is then hermetically sealed (sealed). In this manner, a first power storage device 110 and a second power storage device 120 having different opposing capacity ratios can be prepared.

(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, for example, in the configuration shown in FIG. 5 , both ends in the arrangement direction X (particularly the front F in the arrangement direction X) tend to become low-temperature regions A1. However, the temperature distribution within the energy storage module 500 can also vary depending on the configuration of the cooling device 400 (e.g., the installation positions and number of the air intake port IP, exhaust port OP, and 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) can also vary depending on, for example, the number of energy storage devices 100 and the charge and discharge conditions. Therefore, it is preferable to predict the temperature distribution within the energy storage module 500 during charge and discharge through preliminary experiments or simulations using commercially available analysis software. In particular, it is preferable to construct a preliminary test energy storage module simulating the energy storage module 500, measure the temperature distribution, and predict the temperature distribution within the energy storage module 500 based on the actual measurements.

In a preferred embodiment, first, multiple power storage devices for a preliminary test are prepared that are different from the first power storage device 110 and the second power storage device 120 produced in the preparation process, and a temperature sensor is attached to each. Next, a power storage module for a preliminary test that simulates the power storage module 500 is assembled using the multiple power storage devices for the preliminary test. Next, the multiple power storage devices for the preliminary test are actually charged and discharged (preferably at a high rate), and the temperature distribution during this process is obtained. The charge and discharge conditions are preferably those that simulate actual use. Then, based on the obtained temperature distribution, the temperature distribution within the power storage module 500 is predicted and divided (e.g., into two regions), for example, into a low-temperature region A1 and a high-temperature region A2.

(Step C) In the construction step, the first power storage device 110 and the second power storage device 120 are arranged based on the temperature distribution predicted in the temperature distribution prediction step to construct the power storage module 500. Specifically, the first power storage device 110, which has a relatively high opposing capacity ratio, is arranged in an area designated as the low-temperature area A1, and the second power storage device 120, which has a relatively low opposing capacity ratio, is arranged in an area designated as the high-temperature area A2. Then, the first power storage device 110 and the second power storage device 120 are restrained and held together by a restraining mechanism 300, for example, together with a plurality of spacers 200. In this manner, the power storage module 500 can be constructed.

[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 for 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). By mounting the power storage module 500 on a mobile object such as a vehicle, the fuel efficiency (electricity cost) of the mobile object can be improved.

The following describes several test examples related to the present invention, but it is not intended that the present invention be limited to these test examples.

In this test example, energy storage devices with different counter-current capacity ratios were constructed and their high-rate durability was confirmed. Specifically, electrode assemblies with the counter-current capacity ratios shown in Table 1 were first fabricated, and energy storage devices (lithium-ion secondary batteries, Examples 1 to 4) were fabricated using these electrode assemblies. The counter-current capacity ratio was adjusted by changing the basis weight of the negative electrode active material layer. Furthermore, the configuration other than the basis weight of the negative electrode active material layer was the same for all energy storage devices. Next, the energy storage devices were adjusted to an SOC of 50% in a temperature environment of 25°C, and a constant current discharge of 150 A was performed for 10 seconds, and the discharge resistance was measured. Next, the battery voltage drop ΔV 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).

Next, the energy storage device was adjusted to an SOC of 50% in a 25°C 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. Then, a constant-current discharge at a discharge rate of 10 A for 150 seconds, followed by a 5-second pause, was performed. 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 the capacitance ratio and resistance increase rate of Example 1, each expressed as a relative value with 1.00 (reference).

As shown in Table 1, the higher the counter capacity ratio of an energy storage device, the smaller the increase in resistance after the high-rate durability test, i.e., the higher the high-rate durability. While no particular limitation is intended, the reason for this is thought to be that the higher the counter capacity ratio (here, the relatively higher the negative electrode theoretical capacity), the less likely the negative electrode SOC to increase during high-rate charging and discharging, and the expansion and contraction of the negative electrode is suppressed. From the above, the experimental results also support the idea that energy storage devices with a high counter capacity ratio have relatively better high-rate durability than energy storage devices with a low counter capacity ratio.

The above describes a preferred embodiment of the present invention, but 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 content disclosed in this specification and the common technical knowledge in the relevant field. The technology described in the claims includes various modifications and variations of the above-exemplified embodiment. For example, it is possible to replace part of the above-mentioned embodiment with other modifications, or to add other modifications to the above-mentioned embodiment. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

(1) For example, in the above-described embodiment, in the preparation step (Step A), the power storage devices 100 are manufactured with intentionally different opposing capacity ratios. However, this is not limited to this. For example, the first power storage device 110 and the second power storage device 120 may be selected and prepared within a predetermined range of acceptable products from among a large number of power storage devices with varying opposing capacity ratios.

A specific 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 product. In recent years, energy storage devices such as lithium-ion secondary batteries have been given identification information for reasons of traceability, etc. In one example, an optical symbol that can be read by a reading device is given to the surface of the energy storage module (e.g., sealing plate 14). Alternatively, a small substrate containing identification information is mounted inside the energy storage device. The identification information may include ID information such as the model number, manufacturer name, country of manufacture, name of manufacturing plant, and date of manufacture, as well as composition information such as the type of positive electrode active material and negative electrode active material and opposing capacity ratio.

In this case, the (Step A) preparation step may include: (1-a) an acquisition step of reading out the identification information attached to each of the many collected electricity storage devices to acquire information on the counter-current capacity ratio; and (1-b) a sorting step of sorting out, based on the acquired counter-current capacity ratio information, first electricity storage devices 110 having a relatively high counter-current capacity ratio and second electricity storage devices 120 having a relatively low counter-current capacity ratio in the negative electrode active material layer 24a. This method of manufacturing an electricity storage module can also be understood as a method of reusing electricity storage devices. Note that, in this specification, the term "optical symbol" is a general term for information media that store information by combining areas with high and low optical reflectivity, 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 tags.

(2) 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 high-temperature region A2, where the temperature is relatively high. However, this is not limited to this. As described above, the temperature distribution within the energy storage module 500 can vary depending on the configuration of the cooling device 400 (e.g., the installation positions and number of the air intake port IP, the exhaust port OP, and the air-cooling fans 410), the number of energy storage devices 100, the charge/discharge conditions, etc. Furthermore, in the embodiment of FIG. 5 described above, the energy storage module 500 is divided into two temperature regions, the low-temperature region A1 and the high-temperature region A2, and the temperature distribution is symmetrical in the arrangement direction X. However, this is not limited to this. For example, the energy storage module 500 can also be divided into three or more temperature regions. In this case, in the embodiment of Figure 5, the low-temperature region A1 on the rear Rr side of the arrangement direction X may be made into a medium-temperature region A3, which has a higher temperature than the low-temperature region A1 and a lower temperature than the high-temperature region A2. Furthermore, if the cooling path or heat dissipation path is 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 variations will be described below with reference to Figures 6 to 9. Note that the cooling device is not shown in Figures 6 to 9.

(First Modification) Figure 6 is a plan view of a power storage module 500a according to a first modification. As mentioned 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 Figure 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. As a result, as shown in Figure 6, the temperature distribution of the power storage module 500a is the opposite of that in Figure 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 Figure 6) becoming high-temperature regions A2 with a relatively high temperature.

In such cases, as shown in Figure 6, it is advisable to place a first power storage device 110 with a relatively high opposing capacity ratio (high high-rate resistance) in the center of the arrangement direction X, which is the low-temperature region A1, and place a second power storage device 120 with a relatively low opposing capacity ratio (low high-rate resistance) at both ends of the arrangement direction X, which are the high-temperature regions A2.

(Second and third modified examples) Figure 7 is a plan view of a power storage module 500b according to a second modified example. Figure 8 is a plan view of a power storage module 500c according to a third modified example. For example, if the cooling fan 410 installed on the front F side of the arrangement direction X in Figure 5 is powerful and has high cooling capacity, the temperature distribution within 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 with a relatively low temperature, and the rear Rr part in the arrangement direction X becomes a high-temperature region A2 with a relatively high temperature, as shown in Figures 7 and 8, respectively.

In such cases, as shown in Figures 7 and 8, it is advisable to arrange a first power storage device 110 with a relatively high opposing capacity ratio (high high-rate resistance) in the front F portion of the arrangement direction X, which is the low-temperature region A1, and to arrange a second power storage device 120 with a relatively low opposing capacity ratio (low high-rate resistance) in the rear Rr portion of the arrangement direction X, which is the high-temperature region A2.

Furthermore, the distribution of low temperature regions A1 and high temperature regions A2 may differ depending on, for example, the number of power storage devices 100, charge/discharge conditions, etc. Therefore, the low temperature regions A1 and high temperature regions A2 may be uniformly arranged in the arrangement direction X as shown in FIG. 7, or may be unevenly arranged 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.

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

In such cases, as shown in FIG. 9 , a first power storage device 110 with a relatively high opposing capacity ratio (high high-rate resistance) can be arranged at both ends of the arrangement direction X, which are the low-temperature region A1; a second power storage device 120 with a relatively low opposing capacity ratio (low high-rate resistance) can be arranged in the center of the arrangement direction X, which is the high-temperature region A2; and a third power storage device 130 with a higher opposing capacity ratio than the second power storage device 120 and a lower opposing capacity ratio than the first power storage device 110 can be arranged in the medium-temperature region A3, which is intermediate between the low-temperature region A1 and the high-temperature region A2. In other words, the multiple power storage devices 100 can be arranged so that the opposing capacity ratio increases stepwise 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 to both ends of the arrangement direction X.

Note that while Figure 9 shows the interior of the energy storage module 500 divided into three temperature zones, it is of course possible to divide it into four or more temperature zones. By dividing the interior of the energy storage module 500 into smaller zones in this way according to the temperature distribution, the effects of the technology disclosed herein can be exerted to a high level, and the high-rate resistance of the entire energy storage module 500 can be further improved.

As described above, specific aspects of the technology disclosed herein include those described in the following sections.
Item 1: An energy storage module including a plurality of energy storage devices, each of the plurality of energy storage devices having a positive electrode and a negative electrode, wherein the energy 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 plurality of energy storage devices are charged or discharged, and wherein, when a ratio of a theoretical capacity per unit area of the negative electrode to a theoretical capacity per unit area of the positive electrode (negative electrode theoretical capacity/positive electrode theoretical capacity) is defined as an opposed capacity ratio, a first energy storage device of the plurality of energy storage devices that is arranged in the low-temperature region has a higher opposed capacity ratio than a second energy storage device that is arranged in the high-temperature region.
Item 2: The energy storage module according to Item 1, wherein, between the low temperature region and the high temperature region, there is a medium 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, and the plurality of energy storage devices are arranged such that the opposing capacity ratio increases stepwise 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 2, wherein the difference in the opposing capacity ratio between the first energy storage device and the second energy storage device is 10% or more.
Item 4: The storage module according to any one of Items 1 to 3, wherein the opposing capacity ratio of the first storage device and the second storage device is in the range of 1.0 or more and 2.0 or less.
Item 5: The electricity storage module according to any one of Items 1 to 4, wherein the negative electrode has a negative electrode active material layer, and the first electricity storage device has a larger basis weight of the negative electrode active material layer than the second electricity storage device.
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 both lithium ion secondary batteries.
Clause 7: A method for manufacturing an electricity storage module including a plurality of electricity storage devices, each having a positive electrode and a negative electrode, wherein, when a ratio of a theoretical capacity per unit area of the negative electrode to a theoretical capacity per unit area of the positive electrode (negative electrode theoretical capacity/positive electrode theoretical capacity) is defined as an opposed capacity ratio, the plurality of electricity storage devices include a preparation step of preparing a first electricity storage device having a relatively high opposed capacity ratio and a second electricity storage device having a relatively low opposed capacity 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.

REFERENCE SIGNS LIST 10 Battery case 20 Electrode body 22 Positive electrode 22a Positive electrode active material layer 24 Negative electrode 24a Negative electrode active material layer 100 Electricity storage device 110 First electricity storage device 120 Second electricity storage device 130 Third electricity storage device 300 Restraint mechanism 400 Cooling device 410 Air-cooling fan 500 Electricity storage module A1 Low temperature region A2 High temperature region A3 Medium temperature region

Claims (7)

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 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, the ratio of the theoretical capacity per unit area of the negative electrode to the theoretical capacity per unit area of the positive electrode (negative electrode theoretical capacity/positive electrode theoretical capacity) is defined as the opposing capacity ratio:
Among the plurality of power storage devices, a first power storage device arranged in the low temperature region has a higher opposed capacity ratio than a second power storage device arranged in the high temperature region.
Energy storage module. 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 opposing capacity ratio increases 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 . a difference in the opposing capacity ratio between the first power storage device and the second power storage device is 10% or more;
The energy storage module according to claim 1 . the first power storage device and the second power storage device each have an opposing capacity ratio in the range of 1.0 or more and 2.0 or less;
The energy storage module according to claim 1 . the negative electrode has a negative electrode active material layer,
the first electricity storage device has a larger basis weight of the negative electrode active material layer than the second electricity storage device;
The energy storage module according to claim 1 . The first power storage device and the second power storage device are both lithium ion secondary batteries.
The energy storage module according to claim 1 . 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, the method comprising:
Here, the ratio of the theoretical capacity per unit area of the negative electrode to the theoretical capacity per unit area of the positive electrode (negative electrode theoretical capacity/positive electrode theoretical capacity) is defined as the opposing capacity ratio:
a preparation step of preparing, as the plurality of power storage devices, a first power storage device having a relatively high opposed capacity ratio and a second power storage device having a relatively low opposed capacity 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.