JP7699623B2 - Electricity storage module and manufacturing method thereof - Google Patents

Description

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

Conventionally, power storage modules made up of multiple power storage devices (single cells) electrically connected together 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 a predetermined position. 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 binding member that applies a binding pressure in the arrangement direction to bind the cell group. The housing includes an area that is relatively prone to low temperatures, and the submodules arranged in the area that is prone to low temperatures are configured so that the binding pressure of the binding member is relatively lower than that of the other submodules. Patent Document 1 describes that by lowering the binding pressure on the energy storage devices in this area where the high-rate resistance is likely to decrease (area that is prone to low temperatures), the high-rate resistance (increase in resistance when high-rate charging and discharging is repeated) of the multiple energy storage devices can be leveled out.

JP 2021-044212 A JP 2019-033042 A

In the technology described in Patent Document 1, the multiple power storage devices included in one cell group cannot have different restraining pressures. Therefore, according to the inventors' studies, when temperature distribution occurs within the cell group, it can be difficult to equalize the high-rate resistance of multiple power storage devices. In addition, because a restraining member is required for each cell group, the restraining member becomes bulky and the volumetric energy density of the entire power storage module decreases, and when the power storage module is mounted on a moving object such as a vehicle, for example, the weight increases and there is a risk of fuel efficiency worsening.

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

The present invention provides an electricity storage module including a plurality of electricity storage devices, each of which has a first electrode including a first active material layer, and in which there are 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 electricity storage devices are charged and discharged, and among the plurality of electricity storage devices, a first electricity storage device arranged in the low-temperature region has a smaller basis weight of the first active material layer than a second electricity storage device arranged in the high-temperature region, and has a larger area of the first active material layer than the second electricity storage device.

The present invention also provides a method for manufacturing an electricity storage module including a plurality of electricity storage devices, each of which has a first electrode including a first active material layer. This manufacturing method includes a preparation step of preparing, as the plurality of electricity storage devices, a first electricity storage device having a relatively small basis weight of the first active material layer and a relatively large area of the first active material layer, and a second electricity storage device having a large basis weight of the first active material layer and a relatively small area of the first active material layer, 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.

After extensive research, the inventors have found that an electricity storage device with a small active material layer weight has relatively better high-rate resistance than an electricity storage device with a large active material layer weight. In the present invention, therefore, an electricity storage device with a relatively small weight (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. In addition, the high-rate resistance of the entire electricity storage module can be improved. In addition, 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 each electricity storage device can be flexibly adjusted. Furthermore, the number of restraining members can be reduced compared to the technology of Patent Document 1, so volumetric energy density and fuel efficiency can also be improved.

In addition, in the electricity storage device (first electricity storage device) with a small basis weight of the active material layer, the area of the active material layer is formed larger than that of the electricity storage device (second electricity storage device) with a large basis weight of the active material layer, and the imbalance in electrode capacity is reduced. This makes it possible to equalize the energy density between the first electricity storage device and the second electricity storage device, and to achieve a high energy density for the entire electricity storage module.

Although not particularly related to the technology disclosed herein, Patent Document 2 describes a method for manufacturing an electricity storage device that includes a binding process in which multiple battery cells are stacked and bound, and an activation process in which initial charging, high-temperature aging treatment, and self-discharge testing are performed in that order after the binding process, and that in the binding process, battery cells with larger battery capacities are positioned closer to the end of the bound state.

FIG. 1 is a perspective view illustrating a power storage module according to an embodiment. FIG. 2 is a perspective view that illustrates a schematic diagram of 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 that typically illustrates the power storage module and the cooling device of FIG. FIG. 6 is a plan view that illustrates a power storage module according to a first modified example. FIG. 7 is a plan view that illustrates a power storage module according to a second modified example. FIG. 8 is a plan view illustrating a power storage module according to a third modified example. FIG. 9 is a plan view illustrating a power storage module according to a fourth modified example.

Below, a preferred embodiment of the technology disclosed herein will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification that are necessary for implementing the present invention (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 for a person skilled in the art based on the prior art in the field. The energy storage module disclosed here can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.

In the following drawings, the same reference numerals are used for components and parts that perform the same function, and duplicate explanations may be omitted or simplified. In this specification, the notation "A to B" indicating a range includes not only the meaning of A or more and B or less, but also the meanings of "preferably larger than A" and "preferably smaller than B." In this specification, the notation "equal" does not necessarily refer to perfect agreement, but also allows for a variation of about ±5% (production error, etc.), for example.

[Electricity storage module]
1 is a perspective view that typically illustrates 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 thickness direction, width direction perpendicular to the thickness direction, and top-bottom direction, respectively, of the energy storage device 100. The thickness direction X is also the arrangement direction of the energy storage device 100. However, these are merely directions for the convenience of description and do not limit the installation form of the energy storage module 500 in any way.

The restraining mechanism 300 is a member that restrains the multiple power storage devices 100. Here, there is one restraining mechanism 300. Here, the restraining mechanism 300 is configured to apply an equal restraining pressure from the arrangement direction X to all the power storage devices 100 and the spacers 200. 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 the multiple power storage devices 100. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal.

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 multiple energy storage devices 100 and the multiple 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 by multiple screws 330 so that the restraining load is, for example, about 10 to 15 kN. As a result, a uniform restraining load is applied to the multiple energy storage devices 100 from the arrangement direction X, and the multiple 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, multiple restraining bands, bind 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 a spacer 200, the energy storage devices 100 adjacent to each other in the arrangement direction X may be in contact (direct contact). The spacers 200 preferably include a porous structure portion through which a fluid (typically a gas such as air) can pass.

The power storage device 100 is a device that can be repeatedly charged and discharged. In this specification, the term "power storage device" is a concept that includes secondary batteries such as lithium ion secondary batteries and nickel metal hydride batteries, and capacitors such as lithium ion capacitors and electric double layer capacitors. 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 changed as appropriate.

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 moving body such as a vehicle. Furthermore, in the case of a series connection, deterioration in the performance of some of the energy storage devices 100 is likely to lead to deterioration in the performance of the entire energy storage module 500. For this reason, it is particularly effective to apply the technology disclosed herein.

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

Figure 3 is a schematic vertical cross-sectional view taken along line III-III in Figure 2. As shown in Figure 3, the power 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 power storage device 100 further includes a non-aqueous electrolyte. The power storage device 100 is configured by housing 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 power storage device 100 is typically a non-aqueous electrolyte secondary battery, and is a lithium ion secondary battery in this case. When the power storage device 100 is a non-aqueous electrolyte secondary battery (particularly a lithium ion secondary battery), it is particularly effective to apply the technology disclosed herein.

The battery case 10 is a container that contains the electrode body 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 used conventionally, 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 body) 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 that extend from the long side of the bottom wall 12a and face each other, and a pair of short side walls 12c that extend from the short side of the bottom wall 12a and face each other. The long side walls 12b are flat.

The sealing plate 14 is a plate-like member. The sealing plate 14 is substantially rectangular. As shown in FIG. 3, the sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The battery case 10 is integrated by joining (preferably welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed (closed). The sealing plate 14 has a liquid injection hole 15 and two terminal pull-out holes 18 and 19. The liquid injection hole 15 is for injecting nonaqueous electrolyte after the sealing plate 14 is assembled to the exterior body 12. The liquid injection hole 15 is sealed with a sealing member 16. The terminal pull-out holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z.

The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the width direction Y (the left end in FIG. 2 and FIG. 3), and the negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the width direction Y (the right end in FIG. 2 and FIG. 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 pull-out holes 18 and 19, respectively. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are crimped to the peripheral portion surrounding the terminal pull-out holes 18 and 19 of the sealing plate 14 by crimping. The crimped portions 30c and 40c are formed at the ends of the positive electrode terminal 30 and the negative electrode terminal 40 on the side of the exterior body 12 (the lower end in FIG. 3). As a result, the positive electrode terminal 30 and the negative electrode terminal 40 are fixed 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 body 20 through the positive electrode current collector 50 inside the exterior body 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 body 20 through the negative electrode current collector 60 inside the exterior body 12. The negative electrode terminal 40 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90.

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. For example, the electricity storage module 500 is connected in series by electrically connecting the positive electrode external conductive member 32 of one of the electricity storage devices 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.

Figure 4 is a schematic diagram showing the configuration of the electrode body 20. As shown in Figure 4, the electrode body 20 has a positive electrode 22, a negative electrode 24, and a separator 26. One of the positive electrode 22 and the negative electrode 24 is an example of a "first electrode having a first active material layer," and the other is an example of a "second electrode having a second active material layer."

Here, the electrode body 20 is a wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are stacked via a strip-shaped separator 26 and wound around a winding axis WL. The number of windings (number of turns) of the wound electrode body is not particularly limited, but is preferably 20 turns or more, more preferably 30 turns or more, and even more preferably 50 turns or more, for example, 150 turns or less, 100 turns or less, in an electric storage device 100 mounted on a moving body such as a vehicle. The electrode body 20 has a flat outer shape. Here, the electrode body 20 is arranged inside the exterior body 12 with the winding axis WL oriented approximately parallel to the width direction Y. However, in other embodiments, the electrode body 20 may be arranged inside the exterior body 12 with the winding axis WL oriented approximately parallel to the vertical direction Z. The electrode body 20 may also be a laminated electrode body in which multiple square-shaped (typically rectangular) positive electrodes and multiple square-shaped (typically rectangular) negative electrodes are stacked in an insulated state.

The configuration of the positive electrode 22 may be the same as that of the conventional one. Here, the positive electrode 22 includes a positive electrode collector 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed on at least one surface of the positive electrode collector 22c. The positive electrode active material layer 22a is an example of a "first active material layer" or a "second active material layer". However, when the negative electrode 24 is the first electrode, the positive electrode active material layer 22a is not essential, and the positive electrode 22 may be, for example, metallic lithium, and may not have the positive electrode active material layer 22a. In addition, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments. The positive electrode collector 22c is strip-shaped. The positive electrode collector 22c is preferably made of metal, and more preferably made of metal foil. Here, the positive electrode collector 22c is aluminum foil.

A plurality of positive electrode tabs 22t are provided at one end of the positive electrode collector 22c in the width direction Y (the left end in FIG. 4). The plurality of positive electrode tabs 22t protrude toward one side in the width direction Y (the left end in FIG. 4). The plurality of positive electrode tabs 22t protrude in the width direction Y beyond the separator 26. The positive electrode tab 22t is a part of the positive electrode collector 22c here, and is made of metal foil (aluminum foil). The plurality of positive electrode tabs 22t are stacked at one end in the width 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 collector 50.

The positive electrode active material layer 22a is provided in a strip shape on one or both sides (both sides in this case) of the positive electrode collector 22c along the longitudinal direction MD of the positive electrode 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 the positive electrode active material 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 the lithium transition metal composite oxide include, for example, 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. Among these, lithium nickel cobalt manganese composite oxides are preferred. The positive electrode active material may be used alone or in combination of two or more types.

In this specification, the term "lithium nickel cobalt manganese composite oxide" includes oxides containing Li, Ni, Co, Mn, and O as constituent elements, as well as oxides containing one or more additional elements other than those. Examples of the 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 elements may also be semimetal elements such as B, C, Si, and P, or nonmetal elements such as S, F, Cl, Br, and I. This also applies to the above-mentioned 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 mass% or more, and more preferably, for example, 90 to 99 mass%. The positive electrode active material layer 22a may contain various additive components such as optional components other than the positive electrode active material, 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 a storage module 500 to be mounted on a moving body such as a vehicle, the thickness of the positive electrode active material layer 22a (average thickness per side 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 in 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, 20 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 collector 22c and the positive electrode active material layer 22a in the width 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.

The configuration of the negative electrode 24 may be the same as that of the conventional negative electrode. Here, the negative electrode 24 includes a negative electrode collector 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode collector 24c. The negative electrode active material layer 24a is an example of a "first active material layer" or a "second active material layer". However, when the positive electrode 22 is the first electrode, the negative electrode active material layer 24a is not essential, and the negative electrode 24 may be, for example, sheet-shaped carbon or silicon, and may not have the negative electrode active material layer 24a. The negative electrode collector 24c is strip-shaped. The negative electrode collector 24c is preferably made of metal, and more preferably made of metal foil. Here, the negative electrode collector 24c is copper foil.

A plurality of negative electrode tabs 24t are provided at one end of the negative electrode collector 24c in the width direction Y (the right end in FIG. 4). The plurality of negative electrode tabs 24t protrude toward one side in the width direction Y (the right end in FIG. 4). The plurality of negative electrode tabs 24t protrude in the width direction Y beyond the separator 26. The negative electrode tab 24t is a part of the negative electrode collector 24c here, and is made of metal foil (copper foil). The plurality of negative electrode tabs 24t are stacked at one end of the width 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 width direction Y. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode collector 60.

The negative electrode active material layer 24a is provided in a strip shape on one or both sides (both sides in this case) of the negative electrode collector 24c along the longitudinal direction MD of the negative electrode 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 the negative electrode active material include carbon materials such as graphite, hard carbon, and soft carbon, and 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 ratio 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 various additive components such as optional components other than the negative electrode active material, 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 one side of the negative electrode current collector 24c) is, for example, 10 to 400 μm, and preferably 20 to 300 μm, in a storage module 500 mounted on a moving body 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 FIG. 4. From the viewpoint 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, or 20 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 and the negative electrode 24. The configuration of the separator 26 may be the same as that of a conventional separator. The length Ls of the separator 26 in the width direction Y is preferably equal to or longer than the length Ln of the negative electrode active material layer 24a in the width 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 the conventional one. 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 an additive as necessary. The non-aqueous electrolyte is typically liquid, but may be gelled. In another embodiment, the electricity storage device 100 may include a solid electrolyte instead of the non-aqueous electrolyte. In that case, the separator 26 can be omitted.

Figure 5 is a plan view showing the power storage module 500 and the cooling device 400. Note that detailed illustration of the spacer 200 and the top surface of the power storage device 100 is omitted in Figure 5. As shown in Figure 5, the cooling device 400 here includes an 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 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.

In this embodiment, the air intake port IP is provided on one side (front F side) of the arrangement direction X of the power storage module 500. The exhaust port OP is provided on the other side (rear Rr side) of 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 disposed in the center of the power storage module 500 in the XY plane here. 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-cooled fan 410. For example, when the temperature sensor 420 detects that the temperature inside the power storage module 500 is equal to or higher than a predetermined first temperature, the control device 430 operates the air-cooled fan 410. As a result, low-temperature air outside the power storage module 500 is supplied from the air intake port IP into the power storage module 500, and an air flow AF is generated 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 discharged from the exhaust port OP. For example, when the temperature sensor 420 detects that the temperature inside the power storage module 500 is equal to or lower than a predetermined second temperature, the control device 430 stops the air-cooled fan 410. With such an air-cooled cooling device 400, the power storage device 100 can be cooled at low cost.

According to the inventors' study, a temperature distribution occurs inside the energy storage module 500 equipped with a cooling mechanism such as the cooling device 400 when the multiple energy storage devices 100 are charged and discharged, 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 up. As a result, in the center of the arrangement direction X, a chain reaction of heat generation occurs between the energy storage devices 100, and the temperature tends to become relatively high. On the other hand, the two ends of the arrangement direction X (the front F part and the rear Rr part in FIG. 5) have higher heat dissipation properties than the center, so that a chain reaction of heat generation is less likely to occur. Therefore, the temperature tends to be relatively low at both ends of the arrangement direction X.

In particular, in this embodiment, the intake port IP and the air-cooled fan 410 to which the 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. For this reason, both ends of the arrangement direction X tend to become low temperature. Therefore, the center of the arrangement direction X becomes the high temperature area A2 where the temperature is relatively high, and both ends of the arrangement direction X (the front F part and the rear Rr part in FIG. 5) tend to become the low temperature area A1 where the temperature is relatively low. In particular, the front F part of the arrangement direction X where the intake port IP and the air-cooled fan 410 are arranged tends to become the coldest. That is, in this embodiment, at least the front F side of the arrangement direction X tends to become the low temperature area A1 where the temperature is relatively low.

For example, as described in Patent Document 1, etc., if a temperature distribution occurs in the power storage module 500 in this way, the high-rate resistance of the power storage device 100 may vary. More specifically, the high-rate resistance of the power storage device 100 may be low 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 standard, a high voltage is applied to the power storage device 100 in the low-temperature region A1, and high-rate deterioration is likely to accelerate. In this way, if a temperature distribution occurs in the power storage module 500, the high-rate resistance of the entire power storage module 500 may be reduced due to the high-rate resistance of the power storage device 100 in the low-temperature region A1. Furthermore, when the power storage module is mounted on a moving body such as a vehicle, there is a risk of fuel efficiency being deteriorated.

Therefore, in the technology disclosed herein, a first electricity storage device 110 and a second electricity storage device 120 having different active material layer weights are used as the multiple electricity storage devices 100. The first electricity storage device 110 has a smaller active material layer weight than the second electricity storage device 120. As will be described in detail later, the inventors have confirmed that the smaller the active material layer weight of the electricity storage device 100, the higher the high-rate resistance. Therefore, in this embodiment, the first electricity storage device 110 having a relatively small weight (high high-rate resistance) is arranged in the low-temperature region A1, where the temperature is relatively low, here at both ends in the arrangement direction X (the front F part and the rear Rr part in FIG. 5). In addition, the second electricity storage device 120 having a relatively large weight (low high-rate resistance) is arranged in the high-temperature region A2, where the temperature is relatively high, here at the center of the arrangement direction X.

With this configuration, the high-rate resistance of the multiple power storage devices 100 can be equalized at a high level. In addition, the acceleration of deterioration can be suppressed, and the high-rate resistance of the entire power storage module 500 can be improved. In addition, 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 the technology of Patent Document 1. Furthermore, since the number of restraining mechanisms 300 can be reduced compared to the technology of Patent Document 1, the volumetric energy density and fuel efficiency can also be improved. In addition, the number of parts can be reduced, reducing manufacturing costs.

In this specification, the term "weight per unit area" refers to the mass (solid content) of the active material layer per unit area of the current collector. When the first electrode is the positive electrode 22, it is the mass of the positive electrode active material layer 22a per unit area of the positive electrode current collector 22c, and when the first electrode is the negative electrode 24, it is the mass of the negative electrode active material layer 24a per unit area of the negative electrode current collector 24c. The unit is mg/ ^cm2 . In this specification, the term "active material layer" can be appropriately replaced with the positive electrode active material layer 22a and/or the negative electrode active material layer 24a, and the term "electrode" can be appropriately replaced with the positive electrode 22 and/or the negative electrode 24.

When there are multiple first electricity storage devices 110 and multiple second electricity storage devices 120 as in this embodiment, it is preferable that each of the multiple first electricity storage devices 110 has a smaller basis weight than the multiple second electricity storage devices 120.

The specific value of the basis weight of the active material layer is a design item that is appropriately adjusted depending on, for example, the use of the power storage module 500. For this reason, although not particularly limited, in the power storage module 500 that is mounted on a moving body such as a vehicle, the basis weight of the active material layer of both the first power storage device 110 and the second power storage device 120 is preferably in the range of 1 to 50 mg/cm ^2. More preferably, the basis weight of the positive electrode active material layer 22a 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. In addition, 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 . When active material layers are formed on both sides of the current collector, the above-mentioned coating weight value is the coating amount of the active material layer on one side.

The difference in weight between the first and second storage devices 110 and 120 is a design item that is appropriately adjusted, for example, depending on the temperature distribution in the storage module 500. For this reason, although not particularly limited, in cases where the temperature distributions of the first and second storage devices 110 and 120 are significantly different, for example, when the weight of the first storage device 110 is taken as the reference (100%), the difference in weight between the first and second storage devices 110 and 120 is preferably 10% or more, more preferably 20% or more, and may be, for example, 25% or more. By setting the difference in weight to a predetermined value or more, the effect of the technology disclosed herein can be more significantly exhibited. The difference in weight may be, for example, 100% or less, or 50% or less. This allows the high-rate charging characteristics of the first and second storage devices 110 and 120 to be accurately leveled out. In addition, when there are multiple first electricity storage devices 110 and multiple second electricity storage devices 120, the difference in basis weight can be the difference between the average basis weight of the multiple first electricity storage devices 110 and the average basis weight of the multiple second electricity storage devices 120.

If the density of the active material layer is the same in the first electricity storage device 110 and the second electricity storage device 120, the thickness of the active material layer in the first electricity storage device 110 may be smaller than that of the second electricity storage device 120 due to the smaller basis weight.

In addition, in the technology disclosed herein, the first power storage device 110 has a larger active material layer area than the second power storage device 120. The second power storage device 120 has a smaller active material layer area than the first power storage device 110. As a result, the total mass of the active material layer in the power storage device 100 is homogenized between the first power storage device 110 and the second power storage device 120, and the imbalance in the electrode capacity (electrode theoretical capacity) calculated by the following formula: total mass of active material (g) x theoretical capacity per unit mass of active material (mAh/g) is reduced. With this configuration, the energy density of the first power storage device 110 and the second power storage device 120 is equalized, and a high energy density can be achieved in the entire power storage module 500. The theoretical capacity of the active material (or the calculation method thereof) is publicly known. For example, the theoretical capacity of graphite as a negative electrode active material is 372 mAh/g.

In this embodiment, the first electricity storage device 110 is formed with a larger area (cm ² ) of the active material layer in proportion to the smaller basis weight (mg/cm ² ) of the active material layer compared to the second electricity storage device 120. The second electricity storage device 120 is formed with a smaller area (cm ² ) of the active material layer in proportion to the larger basis weight (mg/cm ² ) of the active material layer compared to the first electricity storage device 110. That is, the area of the active material layer of the first electricity storage device 110 and the second electricity storage device 120 is determined according to the basis weight of the active material layer, and the total mass (mg) of the active material layer in the electricity storage device 100 is configured to be equal. Furthermore, the first electricity storage device 110 and the second electricity storage device are configured to be equal in total mass (mg) of the active material and to be equal in electrode capacity. This allows the energy density of the first electricity storage device 110 and the energy density of the second electricity storage device 120 to be equalized at a higher level.

The specific value of the total mass (mg) of the active material layer is a design item that is appropriately adjusted depending on, for example, the use of the power storage module 500. For this reason, although not particularly limited, in a power storage module 500 mounted on a moving body such as a vehicle, for example, the first power storage device 110 and the second power storage device 120, the total mass of the active material layer in one power storage device 100 is preferably in the range of 30 to 3000 g (30,000 to 3,000,000 mg). More preferably, the total mass of the positive electrode active material layer 22a in one power storage device 100 is preferably in the range of approximately 20 to 2,000 g (20,000 to 2,000,000 mg), more preferably in the range of 25 to 1,750 g (25,000 to 1,750,000 mg), for example, in the range of 30 to 1,500 g (30,000 to 1,500,000 mg). In addition, the total mass of the negative electrode active material layer 24a in one power storage device 100 is preferably in the range of approximately 13 to 1,300 g (13,000 to 1,300,000 mg), more preferably in the range of 16 to 1,150 g (16,000 to 1,150,000 mg), for example, in the range of 20 to 1,000 g (20,000 to 1,000,000 mg).

In addition, the area (cm ² ) of the active material layer can be adjusted by changing the length in the longitudinal direction MD and/or the length in the lateral direction (the length in the width direction Y in FIG. 4 ) of the active material layer when the active material layer is formed in a strip shape as in the present embodiment. In particular, from the viewpoint of workability, it is preferable to adjust the area of the active material layer by increasing or decreasing the length in the longitudinal direction MD of the active material layer. That is, in one embodiment, it is preferable that the length in the longitudinal direction MD of the active material layer of the first electricity storage device 110 is longer than that of the second electricity storage device 120. In this case, it is more preferable that the first electricity storage device 110 and the second electricity storage device 120 have the same length in the lateral direction of the active material layer (the length Lp in the width direction Y of the positive electrode active material layer 22a or the length Ln in the width direction Y of the negative electrode active material layer 24a in FIG. 4 ). This allows the area of the active material layer to be adjusted relatively easily.

When the electrode body 20 is a wound electrode body as in this embodiment, the first electricity storage device 110 may have a greater number of windings (number of turns) of the wound electrode body than the second electricity storage device 120, for example, by increasing the length of the longitudinal direction MD of the active material layer. The second electricity storage device 120 may have a smaller number of windings of the wound electrode body than the first electricity storage device 110. However, in other embodiments, when the electrode body 20 is a laminated electrode body, the first electricity storage device 110 may have a greater number of rectangular electrodes or a greater number of layers than the second electricity storage device 120, for example, in exchange for increasing the length of the longitudinal direction MD of the active material layer.

In addition, as in this embodiment, when the power storage device 100 has a positive electrode 22 and a negative electrode 24 (i.e., when it has a first electrode and a second electrode), it is preferable that the basis weight of the positive electrode active material layer 22a and the basis weight of the negative electrode active material layer 24a both satisfy the above-mentioned size relationship (first power storage device 110 < second power storage device 120). In other words, it is preferable that the first power storage device 110 has a smaller basis weight of the positive electrode active material layer 22a than the second power storage device 120, and a smaller basis weight of the negative electrode active material layer 24a than the second power storage device 120. In addition, it is preferable that the first power storage device 110 has a larger area of the positive electrode active material layer 22a than the second power storage device 120, and a larger area of the negative electrode active material layer 24a than the second power storage device 120. This reduces the imbalance in the opposing capacity ratio between the first power storage device 110 and the second power storage device 120.

In one embodiment, it is preferable that the basis weight of the positive electrode active material layer 22a and the basis weight of the negative electrode active material layer 24a in the first electricity storage device 110 are smaller by the same ratio, and the basis weight of the positive electrode active material layer 22a and the basis weight of the negative electrode active material layer 24a in the second electricity storage device 120 are larger by the same ratio. This allows the first electricity storage device 110 and the second electricity storage device 120 to have the same opposing capacity ratio.

The opposing capacity ratio is expressed as the ratio of the electrode capacity of the first electrode to the electrode capacity of the second electrode for each power storage device 100. In this embodiment, it can be expressed as the ratio of the electrode capacity (mAh) of the negative electrode 24 to the electrode capacity (mAh) of the positive electrode 22 (electrode capacity of negative electrode/electrode capacity of positive electrode) in 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).

Although not particularly limited, from the viewpoint of achieving a high level of balance between energy density and high-rate resistance in a storage module 500 mounted on a moving body such as a vehicle, the first storage device 110 and the second storage device 120 both have a counter-capacity ratio that is typically 1.0 or more, and is preferably in the range of approximately 1.0 to 2.0. In particular, in a high-output type storage module 500 such as that 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, in the range of 1.3 to 1.8. However, in a high-capacity type storage module 500 such as that mounted on an electric vehicle (BEV; Battery Electric Vehicle), the counter-capacity ratio may be approximately 1.0 to 1.2, since energy density is prioritized.

In the first power storage device 110, when the basis weight of the positive electrode active material layer 22a and the basis weight of the negative electrode active material layer 24a are reduced by the same ratio, it is preferable that the electrode opposing width of the positive electrode active material layer 22a and the negative electrode active material layer 24a is equal in the short direction (width direction Y in FIG. 4) of the strip-shaped electrode body 20 in the first power storage device 110 and the second power storage device 120. On the other hand, it is preferable that the electrode opposing length of the positive electrode active material layer 22a and the negative electrode active material layer 24a in the longitudinal direction MD of the strip-shaped electrode body 20 in the first power storage device 110 is longer than that of the second power storage device 120. In other words, it is preferable that the electrode opposing area of the positive electrode active material layer 22a and the negative electrode active material layer 24a in the first power storage device 110 is larger than that of the second power storage device 120. In particular, it is preferable that the length in the longitudinal direction MD of the strip-shaped positive electrode active material layer 22a is longer than that of the second electricity storage device 120, and the length in the longitudinal direction MD of the strip-shaped negative electrode active material layer 24a is longer than that of the second electricity storage device 120.

[Method of manufacturing the electricity storage module]
Next, a method for manufacturing a power storage module 500 including a plurality of power storage devices 100 will be described. The power storage module 500 can be manufactured by a manufacturing method including, for example, a preparation step (step A) of preparing a first power storage device 110 and a second power storage device 120, a temperature distribution prediction step (step B) of predicting a temperature distribution in the power storage module 500, and a construction step (step C) of constructing the power storage module 500 by combining the first power storage device 110 and the second power storage device 120. The order of the preparation step (step A) and the temperature distribution prediction step (step B) is not particularly limited, and for example, the temperature distribution prediction step (step B) may be performed after the preparation step (step A), the preparation step (step A) may be performed after the temperature distribution prediction step (step B), or both steps may be performed simultaneously. In addition, the manufacturing method disclosed herein may further include other steps at any stage.

In the (step A) preparation step, a first electricity storage device 110 having a relatively small basis weight of the active material layer and a relatively large area of the active material layer and a second electricity storage device 120 having a relatively large basis weight of the active material layer and a relatively small area of the active material layer are prepared as a plurality of electricity storage devices 100. In this embodiment, the (step A) preparation step includes (A-1) a positive electrode preparation step for preparing a positive electrode 22, (A-2) a negative electrode preparation step for preparing a negative electrode 24, (A-3) an electrode body preparation step for preparing an electrode body 20 using the prepared positive electrode 22 and negative electrode 24, (A-4) a housing step for housing the electrode body 20 and a nonaqueous electrolyte in a battery case 10, and (A-5) a conditioning step. However, the order of the positive electrode preparation step and the negative electrode preparation step is not particularly limited. In addition, other steps may be included at any stage.

(A-1) In the positive electrode preparation process, at least two types of positive electrodes 22 having different weights and areas of the positive electrode active material layer 22a are prepared. In detail, a first positive electrode having a relatively small weight and large area of the positive electrode active material layer 22a for the first power storage device 110 and a second positive electrode having a relatively large weight and small area for the second power storage device 120 are prepared. Specifically, for example, first, a positive electrode mixture paste containing at least the positive electrode active material is prepared by dispersing the above-mentioned solid materials (e.g., positive electrode active material, binder, conductive material, etc.) in a predetermined solvent (e.g., water, N-methyl-2-pyrrolidone, etc.). Next, the prepared positive electrode mixture paste is applied to the surface of the positive electrode current collector 22c using a conventionally known coating device and dried. At this time, the weight of the positive electrode active material layer 22a can be adjusted by changing the coating amount per unit area of the positive electrode mixture paste. In a preferred embodiment, the amount of the positive electrode composite paste applied per unit area of the first positive electrode is reduced, and the application area is increased accordingly (preferably, the length in the longitudinal direction MD is increased). After that, pressing and drying processes may be performed as necessary. In this manner, a first positive electrode and a second positive electrode having positive electrode active material layers 22a with different weights and areas can be produced.

(A-2) In the negative electrode preparation process, at least two types of negative electrodes 24 having different weights and areas of the negative electrode active material layer 24a are prepared in accordance with the positive electrode preparation process. In detail, a first negative electrode having a relatively small weight and large area of the negative electrode active material layer 24a for the first power storage device 110 and a second negative electrode having a relatively large weight and small area for the second power storage device 120 are prepared. Specifically, for example, first, a negative electrode mixture paste containing at least the negative electrode active material is prepared by dispersing the above-mentioned solid materials (e.g., negative electrode active material, binder, thickener, etc.) in a predetermined solvent (e.g., water, N-methyl-2-pyrrolidone, etc.). Next, the prepared negative electrode mixture 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 coating amount of the negative electrode composite paste per unit area can be changed to adjust the coating amount of the negative electrode active material layer 24a. In a preferred embodiment, for the first negative electrode, the coating amount of the negative electrode composite paste per unit area is reduced, and the coating area is increased accordingly (preferably, the length in the longitudinal direction MD is increased). It is preferable that the coating amount of the negative electrode composite paste per unit area is reduced by the same ratio as the coating amount of the positive electrode composite paste per unit area. It is also preferable that the coating area of the negative electrode composite paste is reduced by the same ratio as the coating area of the positive electrode composite paste. Thereafter, pressing, drying, or the like 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 amounts and areas can be produced.

(A-3) In the electrode body preparation process, the first positive electrode prepared in the positive electrode preparation process and the first negative electrode prepared in the negative electrode preparation process are opposed to each other via the separator 26 as described above and wound up. In this way, the electrode body 20 for the first electricity storage device 110 is prepared. In addition, the second positive electrode prepared in the positive electrode preparation process and the second negative electrode prepared in the negative electrode preparation process are opposed to each other via the separator 26 as described above and wound up. In this way, the electrode body 20 for the second electricity storage device 120 is prepared. Here, the electrode opposing length in the longitudinal direction MD between the positive electrode active material layer 22a and the negative electrode active material layer 24a of the electrode body 20 for the first electricity storage device 110 is longer than that of the electrode body 20 for the second electricity storage device 120. In other words, the electrode body 20 for the first electricity storage device 110 has a larger opposing area between the positive electrode active material layer 22a and the negative electrode active material layer 24a than the electrode body 20 for the second electricity storage device 120.

In the (A-4) accommodation step, the electrode body 20 prepared in the electrode body preparation step and the non-aqueous electrolyte as described above are accommodated in the battery case 10. In a preferred embodiment, first, the positive electrode tab group 23 of the electrode body 20 is joined to the positive electrode current collector 50, and the negative electrode tab group 25 of the electrode body 20 is joined to the negative electrode current collector 60. This integrates the sealing plate 14 and the electrode body 20. Next, the sealing plate 14 is placed over the opening 12h of the exterior body 12, and the electrode body 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, and the exterior body 12 and the sealing plate 14 are integrated. Next, the non-aqueous electrolyte 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-5) 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. The battery assembly can be charged and discharged in the same manner as in the past. 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 hermetically sealed (closed). In this manner, a first electricity storage device 110 and a second electricity storage device 120 having different active material layer weights and areas (here, the active material layer weights and areas are different for the positive electrode 22 and the negative electrode 24) can be prepared.

(Step B) In the temperature distribution prediction step, the temperature distribution in the power storage module 500 when multiple power storage devices 100 are charged and discharged is predicted. That is, for example, in the embodiment shown in FIG. 5, both ends in the arrangement direction X (particularly the front F part in the arrangement direction X) tend to become the low temperature area A1. However, the temperature distribution in the power storage module 500 may change depending on the configuration of the cooling device 400 (for example, the installation position and number of the intake port IP, exhaust port OP, and air-cooling fan 410) and the heat dissipation path. In addition, for example, the range of the low temperature area A1 (the length of the arrangement direction X) may also change 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 charging and discharging by a preliminary experiment or a simulation using commercially available analysis software. In particular, it is preferable to construct a power storage module for a preliminary test that imitates 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.

In a preferred embodiment, first, multiple power storage devices for a preliminary test that are different from the first power storage device 110 and the second power storage device 120 produced in the preparation process are prepared, and a temperature sensor is attached to each of them. Next, a power storage module for a preliminary test that imitates 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 high-rate charged and discharged), and the temperature distribution at this time is obtained. The charge and discharge conditions are preferably conditions that assume the actual usage mode. Then, based on the obtained temperature distribution, the temperature distribution in the power storage module 500 is predicted, and the module is divided (e.g., divided into two), 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 small basis weight and large area of the active material layer, is arranged in an area separated from the low temperature area A1, and the second power storage device 120, which has a relatively large basis weight and small area of the active material layer, is arranged in an area separated from the high temperature area A2. Then, the first power storage device 110 and the second power storage device 120 are restrained by the restraining mechanism 300 together with, for example, a plurality of spacers 200, and held together. 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 various purposes, but because it has excellent high-rate resistance, it can be suitably used in purposes requiring high output, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car or truck. The type of vehicle is not particularly limited, but examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and an electric vehicle (BEV). By mounting the power storage module 500 on a moving body such as a vehicle, the fuel efficiency (electricity cost) of the moving body can be improved.

Below, we will explain some test examples related to the present invention, but we do not intend to limit the present invention to these test examples.

In this test example, electricity storage devices with different weights and areas of the active material layers were constructed, and high-rate resistance was confirmed. Specifically, first, an electrode body was fabricated in which the positive electrode active material layer and the negative electrode active material layer had the weights and areas shown in Table 1, respectively, and electricity storage devices (lithium ion secondary batteries, Examples 1 to 4) were fabricated using the electrode body. Note that Table 1 shows relative values when the weights and areas of Example 2 are set to 1.00 (reference). The weights and areas of the positive electrode active material layer and the negative electrode active material layer were increased or decreased by the same ratio. The configuration other than the weights and areas of the positive electrode active material layer and the negative electrode active material layer was the same for all electricity storage devices.

Next, in a temperature environment of 25°C, the power storage device was adjusted to a state of SOC 50%, and a constant current discharge of 150 A was performed 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).

Next, in a temperature environment of 25°C, the power storage device was adjusted to a state of SOC 50%, and constant current charging was performed at a charge rate of 150A for 10 seconds, followed by a 5-second pause, followed by a 10A discharge rate for 150 seconds, followed by a 5-second pause. This cycle was repeated 1,000 times to perform a high-rate durability test. 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 durability test/initial resistance). The results are shown in Table 1. Note that Table 1 shows relative values when the resistance increase rate of Example 2 is set to 1.00 (reference).

As shown in Table 1, the smaller the basis weight of the energy storage device, the smaller the increase in resistance after the high-rate durability test, i.e., the higher the high-rate resistance. Although it is not intended to be interpreted in a particularly restrictive manner, the reason for this is thought to be that the smaller the basis weight (here, the relatively smaller the thickness), the easier it is for the nonaqueous electrolyte to penetrate deep into the active material layer, making it less likely for unevenness in the salt concentration to occur, or making it easier to alleviate unevenness in the salt concentration, so that resistance is less likely to increase even when high-rate charging and discharging are repeated. From the above, the experimental results also support the idea that energy storage devices with smaller basis weights have relatively better high-rate resistance than energy storage devices with larger basis weights.

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 changes to the above-exemplified embodiment. For example, it is possible to replace part of the above-mentioned embodiment with other modifications, and it is also possible to add other modifications to the above-mentioned embodiment. Furthermore, if a technical feature is not described as essential, it can also be deleted as appropriate.

(1) For example, in the above embodiment, in the preparation process (Step A), the electricity storage device 100 is manufactured in which the basis weight of the active material layer is intentionally varied. However, this is not limited to this. For example, the first electricity storage device 110 and the second electricity storage device 120 can be prepared by selecting from a large number of electricity storage devices having different basis weights of the active material layer within a predetermined range of good products.

(2) For example, in the embodiment of FIG. 5 described above, both ends of the arrangement direction X (the front F part and the rear Rr part in FIG. 5) are low temperature areas A1 with a relatively low temperature, and the center part of the arrangement direction X is a high temperature area A2 with a relatively high temperature. However, this is not limited to this. As described above, the temperature distribution in the storage module 500 can change depending on the configuration of the cooling device 400 (for example, the installation position and number of the intake port IP, the exhaust port OP, and the air-cooling fan 410), the number of the storage devices 100, the charge and discharge conditions, etc. Also, in the embodiment of FIG. 5 described above, the storage module 500 is divided into two temperature areas, the low temperature area A1 and the high temperature area A2, and the temperature distribution is symmetrical in the arrangement direction X. However, this is not limited to this. For example, the storage module 500 can be divided into three or more temperature areas. In this case, in the embodiment of FIG. 5, the low temperature area A1 on the rear Rr side of the arrangement direction X may be a medium temperature area A3 that is higher in temperature than the low temperature area A1 and lower in temperature than the high temperature area A2. Also, if the cooling path or heat dissipation path is complicated, the temperature distribution may be random, for example, with the low temperature area A1 and the high temperature area A2 appearing alternately. Below, some specific modified examples will be described with reference to FIG. 6 to FIG. 9. Note that the cooling device is not shown in FIG. 6 to FIG. 9.

(First Modification) FIG. 6 is a plan view of a storage module 500a according to a first modification. As described above, it is known that chain heat generation between the storage devices 100 is likely to occur in the center 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 center of the arrangement direction X to strongly cool the center. Then, as shown in FIG. 6, the temperature distribution of the storage module 500a is the opposite of that in FIG. 5, with the center of the arrangement direction X being a low-temperature region A1 with a relatively low temperature, and both ends of the arrangement direction X (the front F portion and the rear Rr portion in FIG. 6) being high-temperature regions A2 with a relatively high temperature.

In such a case, as shown in FIG. 6, a first electricity storage device 110 with a relatively small basis weight and large area of the active material layer (high high-rate resistance) can be arranged in the center of the arrangement direction X, which is the low-temperature region A1, and a second electricity storage device 120 with a relatively large basis weight and small area (low high-rate resistance) can be arranged at both ends of the arrangement direction X, which are the high-temperature regions A2.

(Second and third modified examples) FIG. 7 is a plan view of a storage module 500b according to a second modified example. FIG. 8 is a plan view of a storage module 500c according to a third modified example. For example, if the air-cooling fan 410 installed on the front F side of the arrangement direction X in FIG. 5 is powerful and has high cooling capacity, the temperature distribution in the storage modules 500b and 500c may be such that the front F part in the arrangement direction X becomes a low-temperature area A1 with a relatively low temperature, and the rear Rr part in the arrangement direction X becomes a high-temperature area A2 with a relatively high temperature, as shown in FIG. 7 and FIG. 8, respectively.

In such a case, as shown in Figures 7 and 8, it is advisable to arrange a first electricity storage device 110 having a relatively small basis weight and large area (high high-rate resistance) of the active material layer in the front F part of the arrangement direction X, which is the low-temperature region A1, and to arrange a second electricity storage device 120 having a relatively large basis weight and small area (low high-rate resistance) in the rear Rr part of the arrangement direction X, which is the high-temperature region A2.

The distribution of low temperature regions A1 and high temperature regions A2 may also vary depending on, for example, the number of power storage devices 100, the charging and discharging conditions, etc. For this reason, 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 non-uniformly 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) Fig. 9 is a plan view of a storage module 500d according to a fourth modification. As shown in Fig. 9, the temperature distribution of the storage module 500d is divided in more detail than in Fig. 5. That is, both ends of the arrangement direction X (the front F part and the rear Rr part in Fig. 6) are low temperature areas A1 with relatively low temperatures, the center part of the arrangement direction X is a high temperature area A2 with relatively high temperatures, and between the low temperature area A1 and the high temperature area A2 is a medium temperature area A3 with a higher temperature than the low temperature area A1 and a lower temperature than the high temperature area A2.

In such a case, as shown in FIG. 9, a first electricity storage device 110 having a relatively small basis weight and large area (high high-rate resistance) of the active material layer is arranged at both ends of the arrangement direction X, which is the low-temperature region A1, a second electricity storage device 120 having a relatively large basis weight and small area (low high-rate resistance) is arranged at the center of the arrangement direction X, which is the high-temperature region A2, and a third electricity storage device 130 having a smaller basis weight of the active material layer than the second electricity storage device 120 and a larger basis weight of the active material layer than the first electricity storage device 110 is arranged in the medium-temperature region A3, which is intermediate between the low-temperature region A1 and the high-temperature region A2. In other words, a plurality of electricity storage devices 100 may be arranged 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 of the arrangement direction X toward both ends, so that the basis weight of the active material layer gradually decreases. In addition, from the viewpoint of balancing the electrode capacity, it is advisable to arrange the multiple electricity storage devices 100 so that the area of the active material layer 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 toward both ends in the arrangement direction X, as the basis weight decreases.

In FIG. 9, the inside of the energy storage module 500 is divided into three temperature regions, but it is of course possible to divide it into four or more temperature regions. By dividing the inside of the energy storage module 500 into smaller regions in accordance with the temperature distribution in this manner, 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 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 first electrode including a first active material layer, the energy storage module including 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 a first energy storage device among the plurality of energy storage devices, which is arranged in the low temperature region, has a smaller basis weight of the first active material layer than a second energy storage device arranged in the high temperature region and has a larger area of the first active material layer than the second energy storage device.
Item 2: The energy storage module according to Item 1, wherein within the energy storage module, between the low temperature region and the high temperature region, there is a medium temperature region which 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 basis weight of the first active material layer gradually decreases and the area of the first active material layer gradually increases 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 first active material layer is formed in a band shape, and the first energy storage device has a longer longitudinal length of the first active material layer than the second energy storage device.
Item 4: The electricity storage module according to item 3, wherein the first electricity storage device and the second electricity storage device have the same length in a short side direction of the first active material layer.
Item 5: The first electricity storage device and the second electricity storage device, the basis weight of the first active material layer is in the range of 1 mg / cm ² or more and 50 mg / cm ² or less. Any one of items 1 to 4. The electricity storage module according to claim 4.
Item 6: The electricity storage module according to any one of Items 1 to 5, wherein each of the plurality of electricity storage devices has a second electrode having a second active material layer, and among the plurality of electricity storage devices, the first electricity storage device arranged in the low temperature region has a smaller basis weight of the second active material layer than the second electricity storage device arranged in the high temperature region and has a larger area of the second active material layer than the second electricity storage device.
Item 7: The storage module described in Item 6, wherein the ratio of the electrode capacity of the first electrode to the electrode capacity of the second electrode is an opposed capacity ratio, and the opposed capacity ratios of the first storage device and the second storage device are equal to each other.
Clause 8: A method for manufacturing an electricity storage module comprising a plurality of electricity storage devices, each of the plurality of electricity storage devices having a first electrode comprising a first active material layer, the method including: a preparation step of preparing, as the plurality of electricity storage devices, a first electricity storage device having a relatively small basis weight of the first active material layer and a relatively large area of the first active material layer, and a second electricity storage device having a large basis weight of the first active material layer and a relatively small area of the first active material layer; 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.

10 Battery case 20 Electrode body 22 Positive electrode (first electrode/second electrode)
22a Positive electrode active material layer (first active material layer/second active material layer)
24 Negative electrode (first electrode/second electrode)
24a Negative electrode active material layer (first active material layer/second active material layer)
Reference Signs List 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 (8)

A power storage module including a plurality of power storage devices,
Each of the plurality of power storage devices has a first electrode including a first active material layer,
Within the power storage module, there are 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 power storage devices,
Among the plurality of power storage devices, a first power storage device arranged in the low temperature region has a smaller basis weight of the first active material layer than a second power storage device arranged in the high temperature region, and has a larger area of the first active material layer than the second power storage device.
Energy storage module. a middle temperature region between the low temperature region and the high temperature region in the energy storage module, the middle 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 basis weight of the first active material layer is gradually decreased and the area of the first active material layer is gradually increased in the order of the high temperature region, the intermediate temperature region, and the low temperature region.
The energy storage module according to claim 1 . The first active material layer is formed in a strip shape,
The first power storage device has a longer length in a longitudinal direction of the first active material layer than the second power storage device.
The energy storage module according to claim 1 . The first power storage device and the second power storage device have the same length in a short side direction of the first active material layer.
The power storage module according to claim 3 . In both the first electricity storage device and the second electricity storage device, the basis weight of the first active material layer is in the range of 1 mg/cm2 or ^more and 50 mg/ ^cm2 or less.
The energy storage module according to claim 1 . Each of the plurality of power storage devices has a second electrode including a second active material layer,
Among the plurality of power storage devices, the first power storage device arranged in the low temperature region has a smaller basis weight of the second active material layer than the second power storage device arranged in the high temperature region, and has a larger area of the second active material layer than the second power storage device.
The energy storage module according to claim 1 . If the ratio of the electrode capacitance of the first electrode to the electrode capacitance of the second electrode is defined as an opposed capacitance ratio,
The first power storage device and the second power storage device have an equal opposing capacity ratio.
The power storage module according to claim 6 . A method for manufacturing an electricity storage module comprising a plurality of electricity storage devices, each of the plurality of electricity storage devices having a first electrode including a first active material layer, the method comprising the steps of:
a preparation step of preparing, as the plurality of electricity storage devices, a first electricity storage device in which the basis weight of the first active material layer is relatively small and the area of the first active material layer is relatively large, and a second electricity storage device in which the basis weight of the first active material layer is large and the area of the first active material layer is relatively small;
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 an energy storage module.

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