Electric storage module and method for manufacturing the same

Abstract

To provide a power storage module with a novel structure, in which the high-rate durability of a plurality of power storage devices can be leveled.SOLUTION: A power storage module 500 disclosed here includes a plurality of power storage devices 100. The power storage module 500 includes a low-temperature region A1 with relatively low temperature and a high-temperature region A2 with relatively high temperature when the power storage devices 100 are charged and discharged. A first power storage device 110 disposed in the low-temperature region A1 among the power storage devices 100 includes an active material layer with a smaller basis weight and a larger area compared to a second power storage device 120 disposed in the high-temperature region A2.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a power storage module including a plurality of power storage devices and a method for manufacturing the same.

Background Art

[0002] Conventionally, in a power source for vehicle driving or the like, a power storage module formed by electrically connecting a plurality of power storage devices (single cells) has been widely used. As a related prior art document, Patent Document 1 can be cited.

[0003] For example, Patent Document 1 discloses a power storage module having a plurality of sub-modules and a housing that houses the plurality of sub-modules at predetermined positions. In Patent Document 1, each of the plurality of sub-modules includes a cell group in which a plurality of power storage devices (single cells) are arranged, and a restraining member that applies a restraining pressure in the arrangement direction to restrain the cell group. And, in the housing, there is a region that tends to become relatively low in temperature, and the sub-module arranged in the region that tends to become low in temperature is configured such that the restraining pressure of the restraining member is relatively lower than that of other sub-modules. Patent Document 1 describes that by reducing the restraining pressure on the power storage device in a region (a region that tends to become low in temperature) where the high-rate tolerance is likely to decrease in this way, the high-rate tolerance (increase in resistance when high-rate charge and discharge are repeated) of the plurality of power storage devices can be equalized.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in the above Patent Document 1, for a plurality of power storage devices included in one cell group, it is not possible to make the restraint pressures different from each other. Therefore, according to the study by the present inventors, when a temperature distribution occurs within the cell group, it may be difficult to equalize the high-rate tolerance of the plurality of power storage devices. Further, since a restraint member is essential for each cell group, the restraint member takes up space and the volume energy density of the entire power storage module decreases. For example, when the power storage module is mounted on a moving body such as a vehicle, there is a risk that the weight increases and the fuel consumption deteriorates.

[0006] The present invention has been made in view of the above circumstances, and its main object is to provide a power storage module having a novel configuration capable of equalizing the high-rate tolerance of a plurality of power storage devices and a method for manufacturing the same.

Means for Solving the Problems

[0007] According to the present invention, there is provided a power storage module including a plurality of power storage devices, wherein each of the plurality of power storage devices has a first electrode including a first active material layer, and within the power storage module, when the plurality of power storage devices are charged and discharged, there are a low-temperature region where the temperature relatively decreases and a high-temperature region where the temperature relatively increases. Among the plurality of power storage devices, a first power storage device arranged in the low-temperature region has a smaller basis weight of the first active material layer and a larger area of the first active material layer than a second power storage device arranged in the high-temperature region.

[0008] Further, according to the present invention, there is provided a method for manufacturing a power storage module including a plurality of power storage devices, each of the plurality of power storage devices having a first electrode including a first active material layer. This manufacturing method includes a preparation step of preparing, as the plurality of power storage devices, a first power 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 power 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 power storage module when the plurality of power storage devices are charged and discharged; and a construction step of constructing the power storage module by arranging the first power storage device in a relatively low-temperature region and the second power storage device in a relatively high-temperature region based on the temperature distribution.

[0009] As a result of various studies by the present inventors, it has been found that a power storage device with a small basis weight of the active material layer is relatively superior in high-rate resistance compared to a power storage device with a large basis weight of the active material layer. Therefore, in the present invention, a power storage device with a relatively small basis weight (superior in high-rate resistance) is arranged in a low-temperature region where the high-rate resistance is likely to decrease. Thereby, the high-rate resistance of the plurality of power storage devices can be leveled. As a result, the high-rate resistance of the entire power storage module can be improved. Further, unlike the technology of Patent Document 1, it is not necessary to be confined to the framework of a "cell group", so the high-rate resistance of each power storage device can be flexibly adjusted. Furthermore, since the number of restraining members can be reduced compared to the technology of Patent Document 1, the volume energy density and fuel efficiency can also be improved.

[0010] In addition, in a power storage device (first power 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 a power storage device (second power storage device) with a large basis weight of the active material layer, reducing the imbalance in electrode capacity. Thereby, the energy density is leveled between the first power storage device and the second power storage device, and high energy density of the entire power storage module can be achieved.

[0011] Although not particularly related to the technology disclosed herein, Patent Document 2 describes a method for manufacturing a power storage device including a restraining step of stacking and restraining a plurality of battery cells, and an activation step of sequentially performing initial charging, high-temperature aging treatment, and self-discharge inspection after the restraining step. In the restraining step, it is described that battery cells with a larger battery capacity are arranged closer to the end of the restrained state.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the technology disclosed herein will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention (for example, the general configurations and manufacturing processes of power storage modules and power storage devices that do not characterize the present invention) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The power storage module disclosed herein can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field.

[0014] In the following drawings, members and parts having the same function are denoted by the same reference numerals, and duplicate explanations may be omitted or simplified. Also, in this specification, the notation "A to B" indicating a range includes the meaning of "A or more and B or less", as well as the meaning of "preferably greater than A" and "preferably less than B". Further, in this specification, the notation "equal" does not necessarily refer only to exact coincidence, and for example, a variation of about ±5% (manufacturing error, etc.) is also allowed.

[0015] [Power Storage Module] FIG. 1 is a perspective view schematically showing a power storage module 500. The power storage module 500 here includes a plurality of power storage devices 100, a plurality of spacers 200, and a restraint mechanism 300. However, the plurality of spacers 200 and the restraint mechanism 300 are not essential and can be omitted in other embodiments.

[0016] In the following description, the reference numerals L, R, F, Rr, U, D in the drawings represent left, right, front, rear, up, and down, respectively, and the reference numerals X, Y, Z in the drawings represent the thickness direction, the width direction orthogonal to the thickness direction, and the up-down direction of the power storage device 100, respectively. The thickness direction X is also the arrangement direction of the power storage devices 100. However, these are merely directions for convenience of explanation and do not limit the installation form of the power storage module 500 in any way.

[0017] The restraint mechanism 300 is a member that restrains a plurality of power storage devices 100. Here, there is one restraint mechanism 300. The restraint mechanism 300 is configured to apply an equal restraint pressure from the arrangement direction X to all the power storage devices 100 and the spacers 200. The restraint mechanism 300 includes a pair of end plates 310, a pair of side plates 320, and a plurality of screws 330. The pair of end plates 310 and the pair of side plates 320 can also be regarded as a housing that houses a plurality of power storage devices 100. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal.

[0018] The pair of end plates 310 are arranged at both ends of the power storage module 500 in the arrangement direction X. The pair of end plates 310 sandwich a plurality of power storage devices 100 and a plurality of spacers 200 in the arrangement direction X. The pair of side plates 320 bridge the pair of end plates 310. The pair of side plates 320 are fixed to the end plates 310 by a plurality of screws 330 so that the restraint load is about 10 to 15 kN, for example. Thereby, a uniform restraint load is applied to the plurality of power storage devices 100 from the arrangement direction X, and the plurality of power storage devices 100 are integrally held. However, the configuration of the restraint mechanism is not limited to this. The restraint mechanism 300 may include, for example, a plurality of restraint bands or binding bars instead of the side plates 320.

[0019] The spacers 200 are each arranged between a plurality of power storage devices 100 in the arrangement direction X here. That is, in the arrangement direction X, the power storage devices 100 and the spacers 200 are arranged alternately. However, when the power storage module 500 does not include the spacers 200, the power storage devices 100 adjacent to each other in the arrangement direction X may be in contact (in direct contact). The spacer 200 preferably includes a porous structure portion through which a fluid (typically, a gas such as air) can pass.

[0020] The power storage device 100 is a device capable of repeated charge and discharge. In this specification, the "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. A plurality of power storage devices 100 are arranged here 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). It is preferable that the plurality of power storage devices 100 are constrained by a constraint mechanism 300. Note that the shape, size, number, etc. of the plurality of power storage devices 100 are not limited to the embodiments disclosed in FIG. 1 and can be changed as appropriate.

[0021] Although not shown here, when the power storage module 500 is used, a plurality of power storage devices 100 are electrically connected to each other by a conductive member such as a bus bar. The connection method is not particularly limited and may be, for example, series, parallel, or multi-series multi-parallel. In a preferred embodiment, a plurality of power storage devices 100 are connected in series. Thereby, for example, the output characteristics can be preferably improved to a level suitable for use in a moving body such as a vehicle. Also, in the case of series connection, deterioration of the performance of some of the power storage devices 100 is likely to lead to deterioration of the performance of the entire power storage module 500. Therefore, it is particularly effective to apply the technology disclosed here.

[0022] FIG. 2 is a perspective view of the power storage device 100. As can be seen from FIGS. 1 and 2, the plurality of power storage devices 100 are all flat rectangular shapes and are of the same shape here. The plurality of power storage devices 100 are arranged such that the long side walls 12b described later are parallel to each other. Here, the plurality of power storage devices 100 are arranged in the arrangement direction X so that the long side walls 12b face each other via the spacer 200.

[0023] Figure 3 is a schematic longitudinal sectional view taken along line III-III of Figure 2. As shown in Figure 3, the power storage device 100 includes, here, a battery case 10, an electrode body 20, a positive electrode terminal 30, and a negative electrode terminal 40. Although illustration is omitted, the power storage device 100 further includes a non-aqueous electrolyte here. The power storage device 100 is configured by housing the electrode body 20 and the non-aqueous electrolyte in the battery case 10 to which the positive electrode terminal 30 and the negative electrode terminal 40 are attached. The power storage device 100 is typically a non-aqueous electrolyte secondary battery, and here it is a lithium-ion secondary battery. 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.

[0024] The battery case 10 is a container for housing the electrode body 20 and the non-aqueous electrolyte. As shown in Figure 2, the battery case 10 has an outer shape that is flat, bottomed, and rectangular parallelepiped (square) here. The material of the battery case 10 may be the same as those conventionally used, and there is no particular limitation. The battery case 10 is made of, for example, aluminum, aluminum alloy, iron, iron alloy, etc. As shown in Figure 3, the battery case 10 includes an outer package 12 having an opening 12h and a sealing plate (lid body) 14 for sealing the opening 12h. As shown in Figure 2, the outer package 12 includes a substantially rectangular bottom wall 12a having a long side and a short side, a pair of long side walls 12b extending from the long side of the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the short side of the bottom wall 12a and facing each other. The long side wall 12b is flat.

[0025] The sealing plate 14 is a plate-shaped member. The sealing plate 14 is substantially rectangular. As shown in FIG. 3, the sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The battery case 10 is integrated by joining (preferably, welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed. The sealing plate 14 is provided with a liquid injection hole 15 and two terminal lead-out holes 18 and 19. The liquid injection hole 15 is for injecting a non-aqueous electrolyte after assembling the sealing plate 14 to the exterior body 12. The liquid injection hole 15 is sealed by a sealing member 16. The terminal lead-out holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z.

[0026] The positive terminal 30 is disposed at one end in the width direction Y of the sealing plate 14 (the left end in FIGS. 2 and 3), and the negative terminal 40 is disposed at the other end in the width direction Y of the sealing plate 14 (the right end in FIGS. 2 and 3). As shown in FIG. 3, the positive terminal 30 and the negative terminal 40 respectively extend from the inside to the outside of the sealing plate 14 through the terminal lead-out holes 18 and 19. Here, the positive terminal 30 and the negative terminal 40 are caulked to the peripheral portion surrounding the terminal lead-out holes 18 and 19 of the sealing plate 14 by caulking. Caulking portions 30c and 40c are formed at the ends on the side of the exterior body 12 of the positive terminal 30 and the negative terminal 40 (the lower ends in FIG. 3). Thereby, the positive terminal 30 and the negative terminal 40 are fixed to the sealing plate 14.

[0027] As shown in FIG. 3, the positive terminal 30 is electrically connected to the positive tab group 23 of the electrode body 20 through the positive current collector 50 inside the exterior body 12. The positive terminal 30 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90. The negative terminal 40 is electrically connected to the negative tab group 25 of the electrode body 20 through the negative current collector 60 inside the exterior body 12. The negative terminal 40 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90.

[0028] As shown in FIGS. 2 and 3, a plate-shaped positive electrode external conductive member 32 and a 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 a conductive member such as a bus bar for electrically connecting a plurality of power storage devices 100 to each other is attached. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external insulating member 92. The power storage module 500 is connected in series, for example, by electrically connecting the positive electrode external conductive member 32 of one power storage device 100 and the negative electrode external conductive member 42 of the other power storage device 100 among adjacent power storage devices 100 in the arrangement direction X with a bus bar or the like.

[0029] FIG. 4 is a schematic diagram showing the configuration of the electrode body 20. As shown in FIG. 4, the electrode body 20 includes a positive electrode 22, a negative electrode 24, and a separator 26. Among the positive electrode 22 and the negative electrode 24, one 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".

[0030] Here, the electrode body 20 is a wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are laminated via a strip-shaped separator 26 and wound around a winding axis WL. The number of windings (number of turns) of the wound electrode body is not particularly limited. However, in a power storage device 100 mounted on a moving body such as a vehicle, for example, it is preferably 20 turns or more, more preferably 30 turns or more, and still more preferably 50 turns or more, and is, for example, 150 turns or less and 100 turns or less. The electrode body 20 has a flat outer shape. Here, the electrode body 20 is disposed inside the exterior body 12 in a direction in which the winding axis WL is substantially parallel to the width direction Y. However, in other embodiments, the electrode body 20 may be disposed inside the exterior body 12 in a direction in which the winding axis WL is substantially parallel to the vertical direction Z. Further, the electrode body 20 may be a laminated electrode body in which a plurality of rectangular (typically rectangular) positive electrodes and a plurality of rectangular (typically rectangular) negative electrodes are stacked in an insulated state.

[0031] 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 current collector 22c, a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed on at least one surface of the positive electrode current collector 22c. The positive electrode active material layer 22a is an example of the "first active material layer" to the "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 or the like and may not have the positive electrode active material layer 22a. Further, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode current collector 22c is in a strip shape. The positive electrode current collector 22c is preferably made of metal, and more preferably made of a metal foil. Here, the positive electrode current collector 22c is an aluminum foil.

[0032] A plurality of positive electrode tabs 22t are provided at one end (the left end in FIG. 4) in the width direction Y of the positive electrode current collector 22c. The plurality of positive electrode tabs 22t protrude toward one side (the left side in FIG. 4) in the width direction Y. The plurality of positive electrode tabs 22t protrude in the width direction Y more than the separator 26. Here, the positive electrode tab 22t is a part of the positive electrode current collector 22c and is made of a metal foil (aluminum foil). The plurality of positive electrode tabs 22t are laminated at one end (the left end in FIG. 4) in the width direction Y to form a positive electrode tab group 23. The positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collecting portion 50.

[0033] The positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction MD of the positive electrode current collector 22c on one side or both sides (here, both sides) of the positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material capable of reversibly occluding and releasing charge carriers. Examples of the positive electrode active material include lithium transition metal composite oxides and lithium transition metal phosphate compounds. The lithium transition metal composite oxide preferably contains at least one of Ni, Co, and Mn as the transition metal element. Specific examples of the lithium transition metal composite oxide include, for example, lithium nickel-based composite oxides, lithium cobalt-based composite oxides, lithium manganese-based composite oxides, lithium nickel manganese-based composite oxides, lithium nickel cobalt manganese-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, lithium iron nickel manganese-based composite oxides, and the like. Among them, a lithium nickel cobalt manganese-based composite oxide is preferable. The positive electrode active material may be used alone or in combination of two or more kinds.

[0034] In addition, in this specification, the term "lithium nickel cobalt manganese-based composite oxide" includes oxides containing one or more additional elements other than those in addition to the oxides composed of Li, Ni, Co, Mn, and O as constituent elements. 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, Sn, etc. The additional elements may also be semi-metal elements such as B, C, Si, P, etc. and non-metal elements such as S, F, Cl, Br, I, etc. This also applies to the above-mentioned lithium nickel-based composite oxides, lithium cobalt-based composite oxides, lithium manganese-based composite oxides, lithium nickel manganese-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, lithium iron nickel manganese-based composite oxides, and the like.

[0035] 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, more preferably 90 to 99% by mass, for example. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as various additive components such as a binder, a conductive material, and the like. Examples of the binder include polyvinylidene fluoride (PVdF). Examples of the conductive material include carbon materials such as carbon black. Although not particularly limited, for example, in the power storage module 500 mounted on a moving body such as a vehicle, the thickness of the positive electrode active material layer 22a (average thickness per one side of the positive electrode current collector 22c) is, for example, 10 to 300 μm, preferably 20 to 200 μm.

[0036] Although not particularly limited, for example, in the power storage module 500 mounted on a moving body 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 further preferably 10 cm or more, 20 cm or more, for example. The length Lp may be, for example, 100 cm or less, 50 cm or less, 30 cm or less.

[0037] The positive electrode protective layer 22p is provided at the boundary portion between the positive electrode current collector 22c and the positive electrode active material layer 22a in the 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 (for example, alumina). The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, various additive components, and the like.

[0038] The configuration of the negative electrode 24 may be the same as that of the conventional one. Here, the negative electrode 24 includes a negative electrode current collector 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector 24c. The negative electrode active material layer 24a is an example of the "first active material layer" to the "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-like carbon, silicon, etc., and may not have the negative electrode active material layer 24a. 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 a metal foil. Here, the negative electrode current collector 24c is a copper foil.

[0039] A plurality of negative electrode tabs 24t are provided at one end (the right end in FIG. 4) in the width direction Y of the negative electrode current collector 24c. The plurality of negative electrode tabs 24t project toward one side in the width direction Y (the right side in FIG. 4). The plurality of negative electrode tabs 24t project in the width direction Y more than the separator 26. Here, the negative electrode tab 24t is a part of the negative electrode current collector 24c and is made of a metal foil (copper foil). The plurality of negative electrode tabs 24t are laminated at one end (the right end in FIG. 4) in the width direction Y to form a negative electrode tab group 25. The negative electrode tab group 25 is provided at a position symmetric to the positive electrode tab group 23 in the width direction Y. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collecting portion 60.

[0040] The negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction MD of the negative electrode current collector 24c on one or both surfaces (here, both surfaces) of the negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly occluding and releasing charge carriers. Examples of the negative electrode active material include carbon materials such as graphite, hard carbon, and soft carbon, and compounds containing silicon (Si-containing materials). The graphite may be natural graphite or artificial graphite, or may be amorphous carbon-coated graphite in which the graphite is coated with an amorphous carbon material.

[0041] 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, more preferably 95 to 99% by mass, for example. The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as various additive components such as a binder, a thickener, and a dispersant. Examples of the binder include styrene-butadiene rubber (SBR) and polyvinylidene fluoride (PVdF). Examples of the thickener 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, preferably 20 to 300 μm, in the power storage module 500 mounted on a moving body such as a vehicle.

[0042] 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 further preferably 10 cm or more, 20 cm or more, for example. The length Ln may be, for example, 100 cm or less, 50 cm or less, or 30 cm or less.

[0043] 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 the prior art. The length Ls in the width direction Y of the separator 26 is preferably the same as or longer than the length Ln in the width direction Y of the negative electrode active material layer 24a. As the separator 26, for example, a porous sheet (micro-porous membrane) made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. The separator 26 may be provided with a functional layer (for example, an adhesive layer or a heat resistance layer (HRL)) on the surface of the porous sheet made of resin.

[0044] The configuration of the non-aqueous electrolyte may be the same as that of the prior art. The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt (electrolyte salt). The non-aqueous solvent is, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as lithium hexafluorophosphate (LiPF6) or lithium bis(fluorosulfonyl)imide (LiFSI). The non-aqueous electrolyte may further contain additives as necessary. The non-aqueous electrolyte is typically liquid, but may also be gel-like. In other embodiments, the power storage device 100 may be provided with a solid electrolyte instead of the non-aqueous electrolyte. In that case, the separator 26 can be omitted.

[0045] FIG. 5 is a plan view schematically showing a power storage module 500 and a cooling device 400. In FIG. 5, detailed illustration of the upper surfaces of the spacers 200 and the power storage devices 100 is omitted. As shown in FIG. 5, the cooling device 400 includes, here, an intake port IP, an exhaust port OP, an air-cooling fan 410, a temperature sensor 420, and a control device 430. The cooling device 400 is an air-cooling type cooling device that uses air as a refrigerant here. However, in other embodiments, the cooling device 400 may be a liquid-cooling type cooling device that uses a liquid refrigerant.

[0046] In the present embodiment, the intake port IP is provided on one side (front F side) in the arrangement direction X of the power storage module 500. The exhaust port OP is provided on the other side (rear Rr side) in the arrangement direction X. The air-cooling fan 410 is attached to the intake port IP. The air-cooling fan 410 is configured to send wind (air) to the intake port IP. The configuration of the air-cooling fan 410 is not limited, but for example, it includes an electric motor (not shown). The temperature sensor 420 is disposed at the center in the XY plane of the power storage module 500 here. The temperature sensor 420 is, for example, a thermocouple or a thermistor.

[0047] The control device 430 is electrically connected to the temperature sensor 420 and the electric motor of the air-cooling fan 410. When the control device 430 detects, for example, that the temperature inside the power storage module 500 has reached a predetermined first temperature or higher by the temperature sensor 420, it operates the air-cooling fan 410. As a result, low-temperature air outside the power storage module 500 is supplied into the power storage module 500 from the intake port IP, and an air flow AF is generated inside the power storage module 500. The supplied air passes through the inside of the power storage module 500 while cooling the power storage device 100, and is discharged from the exhaust port OP. When the control device 430 detects, for example, that the temperature inside the power storage module 500 has reached a predetermined second temperature or lower by the temperature sensor 420, it stops the air-cooling fan 410. According to such an air-cooled cooling device 400, the power storage device 100 can be cooled at low cost.

[0048] By the way, according to the study by the present inventors, inside the power storage module 500 equipped with a cooling mechanism such as the cooling device 400, for example, a temperature distribution occurs during charging and discharging of the plurality of power storage devices 100, and a low-temperature region A1 where the temperature relatively becomes low and a high-temperature region A2 where the temperature relatively becomes high may occur. Specifically, when the power storage device 100 generates heat due to charging and discharging, adjacent power storage devices 100 heat each other. As a result, in the central portion in the arrangement direction X, a chain-like heat generation occurs between the power storage devices 100, and the temperature tends to become relatively high. On the other hand, both end portions in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 5) are more heat dissipative than the central portion, so chain-like heat generation is less likely to occur. Therefore, at both end portions in the arrangement direction X, the temperature tends to become relatively low.

[0049] Particularly, in the present embodiment, an intake port IP through which refrigerant (air) is supplied and an air-cooling fan 410 are arranged on the front F side in the array direction X, and an exhaust port OP is arranged on the rear Rr side in the array direction X. For this reason, both ends in the array direction X tend to be at a low temperature. Therefore, the central portion in the array direction X becomes a high-temperature region A2 with a relatively high temperature, and both ends in the array direction X (the front F portion and the rear Rr portion in FIG. 5) tend to become low-temperature regions A1 with a relatively low temperature. In particular, the front F portion in the array direction X where the intake port IP and the air-cooling fan 410 are arranged is most likely to be at the lowest temperature. That is, in the present embodiment, at least the front F side in the array direction X tends to be a low-temperature region A1 with a relatively low temperature.

[0050] As described in Patent Document 1 and the like, for example, when such a temperature distribution occurs in the power storage module 500, variations may occur in the high-rate tolerance of the power storage device 100. Specifically, the high-rate tolerance of the power storage device 100 may be reduced in the low-temperature region A1. In this case, if the charge and discharge of the entire power storage module 500 are controlled based on the high-rate tolerance of the power storage device 100 in the low-temperature region A1, the high high-rate tolerance of the power storage device 100 in the high-temperature region A2 cannot be fully utilized. On the other hand, if the high-rate tolerance of the power storage device 100 in the high-temperature region A2 is used as a reference, a high voltage is applied to the power storage device 100 in the low-temperature region A1, and high-rate degradation is likely to be accelerated. Thus, when a temperature distribution occurs in the power storage module 500, the high-rate tolerance of the entire power storage module 500 may be reduced due to being restricted by the high-rate tolerance of the power storage device 100 in the low-temperature region A1. Furthermore, when the power storage module is mounted on a moving body such as a vehicle, there is also a possibility that the fuel consumption deteriorates.

[0051] Therefore, in the technology disclosed herein, as the plurality of power storage devices 100, a first power storage device 110 and a second power storage device 120 having different basis weights of the active material layer are used. The first power storage device 110 has a smaller basis weight of the active material layer than the second power storage device 120. Although details will be described later, as a result of the study by the present inventors, it has been confirmed that the power storage device 100 with a smaller basis weight of the active material layer has higher high-rate tolerance. Therefore, in the present embodiment, in the low-temperature region A1 where the temperature is relatively low, here, at both ends in the arrangement direction X (the front F part and the rear Rr part in FIG. 5), the first power storage device 110 having a relatively small basis weight (high high-rate tolerance) is arranged. Further, in the high-temperature region A2 where the temperature is relatively high, here, in the central part in the arrangement direction X, the second power storage device 120 having a relatively large basis weight (low high-rate tolerance) is arranged.

[0052] According to such a configuration, the high-rate tolerance of the plurality of power storage devices 100 can be leveled at a high level. As a result, the acceleration of deterioration can be suppressed, and the high-rate tolerance of the entire power storage module 500 can be improved. Further, unlike the technology of Patent Document 1, since there is no need to be confined within the framework of a "cell group", the high-rate tolerance of the plurality of power storage devices 100 can be flexibly adjusted according to the temperature distribution in the power storage module 500. Therefore, in some cases, the high-rate tolerance of the plurality of power storage devices 100 can be leveled with higher accuracy than the technology of Patent Document 1. Furthermore, since the number of restraint mechanisms 300 can be reduced compared to the technology of Patent Document 1, the volumetric energy density and fuel efficiency can also be improved. In addition, the number of parts can be reduced, and the manufacturing cost can be reduced.

[0053] In addition, in this specification, the "basis weight" 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 / cm 2That is also the case. In this specification, wherever it simply says "active material layer", it can be appropriately read as the positive electrode active material layer 22a and / or the negative electrode active material layer 24a as appropriate, and wherever it says "electrode", it can be appropriately read as the positive electrode 22 and / or the negative electrode 24 as appropriate.

[0054] When there are a plurality of the first power storage devices 110 and the second power storage devices 120 respectively as in this embodiment, it is preferable that any of the plurality of first power storage devices 110 has a basis weight smaller than that of the plurality of second power storage devices 120.

[0055] The specific value of the basis weight of the active material layer is a design matter that can be appropriately adjusted depending on, for example, the use of the power storage module 500 and the like. For this reason, although it is not particularly limited, for example, in the power storage module 500 mounted on a moving body such as a vehicle, both the first power storage device 110 and the second power storage device 120 have a basis weight of the active material layer in the range of 1 to 50 mg / cm 2 It is preferably in the range of. 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 It is preferably in the range of, and more preferably in the range of 4 to 30 mg / cm 2 For example, it is good to be in the range of 5 to 25 mg / cm 2 2 It is preferably in the range of. More preferably, the basis weight of the negative electrode active material layer 24a is preferably in the range of approximately 3 to 25 mg / cm 2 It is preferably in the range of, and more preferably in the range of 3.5 to 20 mg / cm 2 For example, it is good to be in the range of 4 to 15 mg / cm 2 Note that the above value of the basis weight is the coating amount of the active material layer on one side when the active material layer is formed on both sides of the current collector.

[0056] The difference in the basis weight between the first power storage device 110 and the second power storage device 120 is a design matter that is appropriately adjusted, for example, according to the temperature distribution within the power storage module 500. Therefore, although not particularly limited, when the temperature distributions of the first power storage device 110 and the second power storage device 120 are significantly different, for example, when the basis weight of the first power storage device 110 is taken as a reference (100%), the difference in the basis weight between the first power storage device 110 and the second power storage device 120 is preferably 10% or more, more preferably 20% or more, and may be, for example, 25% or more. By setting the difference in the basis weight to a predetermined value or more, the effects of the technology disclosed herein can be more significantly exhibited. The difference in the basis weight may be, for example, 100% or less, 50% or less. Thereby, the high-rate charging characteristics of the first power storage device 110 and the second power storage device 120 can be accurately equalized. When there are a plurality of the first power storage devices 110 and the second power storage devices 120, the difference in the basis weight may be the difference between the average of the basis weights of the plurality of first power storage devices 110 and the average of the basis weights of the plurality of second power storage devices 120.

[0057] If the density of the active material layer is the same between the first power storage device 110 and the second power storage device 120, the first power storage device 110 may have a smaller thickness of the active material layer than the second power storage device 120 due to its smaller basis weight.

[0058] In the technology disclosed herein, the area of the active material layer of the first power storage device 110 is formed to be larger than that of the second power storage device 120. The area of the active material layer of the second power storage device 120 is formed to be smaller than that of the first power storage device 110. As a result, in the power storage device 100, the total mass of the active material layer in the first power storage device 110 and the second power storage device 120 is homogenized, and the imbalance of the electrode capacity (electrode theoretical capacity) calculated by the following formula: total mass of the active material (g) × theoretical capacitance per unit mass of the active material (mAh / g); is reduced. With such a configuration, the energy densities of the first power storage device 110 and the second power storage device 120 can be leveled, and a high energy density can be realized for the entire power storage module 500. Note that the theoretical capacitance of the active material (or its calculation method) is known. For example, the theoretical capacitance of graphite as the negative electrode active material is 372 mAh / g.

[0059] In the present embodiment, the first power storage device 110 has a larger area of the active material layer (cm 2 ) by an amount corresponding to a smaller basis weight (mg / cm 2 ) of the active material layer than the second power storage device 120. The second power storage device 120 has a smaller area of the active material layer (cm 2 ) by an amount corresponding to a larger basis weight (mg / cm 2 ) of the active material layer than the first power storage device 110. That is, in the first power storage device 110 and the second power storage device 120, the area of the active material layer is determined according to the basis weight of the active material layer, respectively, so that the total mass (mg) of the active material layer in the power storage device 100 becomes equal. As a result, the first power storage device 110 and the second power storage device are configured such that the total mass (mg) of the active material is equal and the electrode capacities are equal. Thereby, the energy density of the first power storage device 110 and the energy density of the second power storage device 120 can be leveled at a higher level.

[0060] The specific value of the total mass (mg) of the active material layer is a design matter that is appropriately adjusted depending on, for example, the application of the power storage module 500. Therefore, although not particularly limited, in the power storage module 500 mounted on a moving body such as a vehicle, for example, in both the first power storage device 110 and the second power storage device 120, it is preferable that the total mass of the active material layer in one power storage device 100 is in the range of 30 to 3000 g (30000 to 3000000 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 2000 g (20000 to 2000000 mg), more preferably in the range of 25 to 1750 g (25000 to 1750000 mg), and, for example, in the range of 30 to 1500 g (30000 to 1500000 mg). Also, 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 1300 g (13000 to 1300000 mg), more preferably in the range of 16 to 1150 g (16000 to 1150000 mg), and, for example, in the range of 20 to 1000 g (20000 to 1000000 mg).

[0061] Note that the area (cm 2 ) of the active material layer can be adjusted by changing the length in the machine direction MD and / or the length in the cross-machine direction (in FIG. 4, the length in the width direction Y) of the active material layer when the active material layer is formed in a strip shape, for example, as in the present embodiment. Among these, from the viewpoint of workability and the like, it is preferable to adjust the area of the active material layer by increasing or decreasing the length in the machine direction MD of the active material layer. That is, in one embodiment, it is preferable that the first power storage device 110 has a longer length in the machine direction MD of the active material layer than the second power storage device 120. Also, in this case, it is more preferable that the first power storage device 110 and the second power storage device 120 have the same length in the cross-machine direction (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). Thereby, the area of the active material layer can be adjusted relatively simply.

[0062] When the electrode body 20 is a wound electrode body as in this embodiment, the first power storage device 110 can have a larger number of winding turns (number of turns) of the wound electrode body than the second power storage device 120, for example, by increasing the length of the active material layer in the longitudinal direction MD. The second power storage device 120 can have a smaller number of winding turns of the wound electrode body than the first power storage device 110. However, in other embodiments, when the electrode body 20 is a laminated electrode body, the first power storage device 110 may have a larger number of square electrodes or lamination layers than the second power storage device 120, for example, instead of increasing the length of the active material layer in the longitudinal direction MD.

[0063] Also, when the power storage device 100 has a positive electrode 22 and a negative electrode 24 as in this embodiment (that is, when it has a first electrode and a second electrode), it is preferable that both the basis weight of the positive electrode active material layer 22a and the basis weight of the negative electrode active material layer 24a satisfy the above magnitude 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. Also, 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. Thereby, the imbalance in the opposing capacitance ratio can be reduced between the first power storage device 110 and the second power storage device 120.

[0064] 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 of the first power storage device 110 are reduced 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 of the second power storage device 120 are increased by the same ratio. Thereby, the opposing capacitance ratio can be made equal between the first power storage device 110 and the second power storage device 120.

[0065] Incidentally, the opposed capacity ratio is represented by 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 the present embodiment, for example, in the opposed portion where the positive electrode active material layer 22a and the negative electrode active material layer 24a face each other (here, the region of the width Lp of the positive electrode active material layer 22a), it can be represented by the ratio of the electrode capacity (mAh) of the negative electrode 24 to the electrode capacity (mAh) of the positive electrode 22 (negative electrode electrode capacity / positive electrode electrode capacity).

[0066] Although not particularly limited, for example, in the power storage module 500 mounted on a moving body such as a vehicle, from the viewpoint of balancing the energy density and the high-rate tolerance at a high level, etc., both the first power storage device 110 and the second power storage device 120 preferably have an opposed capacity ratio that is typically 1.0 or more and is generally in the range of 1.0 to 2.0. In particular, in a high-output type power storage module 500 such as that mounted on a hybrid electric vehicle (HEV), it is more preferable that the opposed capacity ratio is 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 power storage module 500 such as that mounted on a battery electric vehicle (BEV), since the energy density is prioritized, the opposed capacity ratio may be about 1.0 to 1.2.

[0067] In the case where the basis weight of the positive electrode active material layer 22a and the basis weight of the negative electrode active material layer 24a are decreased by the same ratio in the first power storage device 110, it is preferable that the first power storage device 110 and the second power storage device 120 have the same electrode facing width between the positive electrode active material layer 22a and the negative electrode active material layer 24a in the short side direction (width direction Y in FIG. 4) of the strip-shaped electrode body 20. On the other hand, in the first power storage device 110, it is preferable that the electrode facing length between the positive electrode active material layer 22a and the negative electrode active material layer 24a is longer than that of the second power storage device 120 in the longitudinal direction MD of the strip-shaped electrode body 20. In other words, it is preferable that the first power storage device 110 has a larger electrode facing area between the positive electrode active material layer 22a and the negative electrode active material layer 24a than the second power storage device 120. Specifically, it is preferable that the length of the strip-shaped positive electrode active material layer 22a in the longitudinal direction MD is longer than that of the second power storage device 120, and the length of the strip-shaped negative electrode active material layer 24a in the longitudinal direction MD is longer than that of the second power storage device 120.

[0068] [Method for manufacturing a power storage module] Next, a method for manufacturing a power storage module 500 including a plurality of power storage devices 100 will be described. The power storage module 500 can be manufactured, for example, by a manufacturing method including: (Step A) a preparation step of preparing a first power storage device 110 and a second power storage device 120; (Step B) a temperature distribution prediction step of predicting the temperature distribution in the power storage module 500; and (Step C) a construction step of constructing the power storage module 500 by combining the first power storage device 110 and the second power storage device 120. Note that the order of (Step A) the preparation step and (Step B) the temperature distribution prediction step is not particularly limited. For example, (Step B) the temperature distribution prediction step may be performed after (Step A) the preparation step, (Step A) the preparation step may be performed after (Step B) the temperature distribution prediction step, or both steps may be performed simultaneously. In addition, the manufacturing method disclosed herein may further include other steps at any stage.

[0069] (Project A) In the preparation process, as the plurality of power storage devices 100, a first power 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 power 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. In the present embodiment, the (Project A) preparation process includes: (A-1) a positive electrode manufacturing process for manufacturing the positive electrode 22, (A-2) a negative electrode manufacturing process for manufacturing the negative electrode 24, (A-3) an electrode body manufacturing process for manufacturing the electrode body 20 using the manufactured positive electrode 22 and negative electrode 24, (A-4) an accommodation process for accommodating the electrode body 20 and the non-aqueous electrolyte in the battery case 10, and (A-5) a conditioning process. However, the order of the positive electrode manufacturing process and the negative electrode manufacturing process is not particularly limited. Further, other processes may be included at any stage.

[0070] (A-1) In the positive electrode manufacturing process, at least two types of positive electrodes 22 having different basis weights and areas of the positive electrode active material layer 22a are manufactured. Specifically, a first positive electrode for the first power storage device 110, which has a relatively small basis weight and a large area of the positive electrode active material layer 22a, and a second positive electrode for the second power storage device 120, which has a relatively large basis weight and a small area, are manufactured. Specifically, for example, first, a solid content material (for example, a positive electrode active material, a binder, a conductive material, etc.) as described above is dispersed in a predetermined solvent (for example, water, N-methyl-2-pyrrolidone, etc.) to prepare a positive electrode composite paste containing at least the positive electrode active material. Next, the prepared positive electrode composite 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 basis weight of the positive electrode active material layer 22a can be adjusted by changing the coating amount per unit area of the positive electrode composite paste. In a preferred embodiment, for the first positive electrode, the coating amount per unit area of the positive electrode composite paste is reduced, and accordingly, the coating area is widened (preferably, the length in the machine direction MD is increased). Thereafter, a pressing process, a drying process, or the like may be performed as necessary. As described above, the first positive electrode and the second positive electrode each having a positive electrode active material layer 22a with different basis weights and areas can be manufactured.

[0071] (A-2) In the negative electrode manufacturing process, at least two types of negative electrodes 24 with different basis weights and areas of the negative electrode active material layer 24a are manufactured according to the positive electrode manufacturing process. Specifically, a first negative electrode for the first power storage device 110, which has a relatively small basis weight and a large area of the negative electrode active material layer 24a, and a second negative electrode for the second power storage device 120, which has a relatively large basis weight and a small area, are manufactured. Specifically, for example, first, a solid content material (e.g., negative electrode active material, binder, thickener, etc.) as described above is dispersed in a predetermined solvent (e.g., water, N-methyl-2-pyrrolidone, etc.) to prepare a negative electrode composite paste containing at least the negative electrode active material. 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 coating amount per unit area of the negative electrode composite paste. In a preferred embodiment, for the first negative electrode, the coating amount per unit area of the negative electrode composite paste is reduced, and accordingly, the coating area is widened (preferably, the length in the machine direction MD is increased). The coating amount per unit area of the negative electrode composite paste is preferably reduced by the same ratio as the coating amount per unit area of the positive electrode composite paste. Also, the coating area of the negative electrode composite paste is preferably reduced by the same ratio as the coating area of the positive electrode composite paste. Thereafter, press treatment, drying treatment, etc. may be performed as necessary. As described above, the first negative electrode and the second negative electrode each having a negative electrode active material layer 24a with different basis weights and areas can be manufactured.

[0072] (A-3) In the electrode body manufacturing process, the first positive electrode manufactured in the positive electrode manufacturing process and the first negative electrode manufactured in the negative electrode manufacturing process are opposed to each other with the separator 26 as described above and wound. Thereby, the electrode body 20 for the first power storage device 110 is manufactured. Further, the second positive electrode manufactured in the positive electrode manufacturing process and the second negative electrode manufactured in the negative electrode manufacturing process are opposed to each other with the separator 26 as described above and wound. Thereby, the electrode body 20 for the second power storage device 120 is manufactured. Here, in the electrode body 20 for the first power storage device 110, the electrode facing length in the longitudinal direction MD of the positive electrode active material layer 22a and the negative electrode active material layer 24a is longer than that of the electrode body 20 for the second power storage device 120. In other words, in the electrode body 20 for the first power storage device 110, the facing area between the positive electrode active material layer 22a and the negative electrode active material layer 24a is larger than that of the electrode body 20 for the second power storage device 120.

[0073] (A-4) In the accommodation process, the electrode body 20 manufactured in the electrode body manufacturing process and the non-aqueous electrolyte as described above are accommodated in the battery case 10. In a preferred embodiment, first, the positive electrode tab group 23 of the electrode body 20 is joined to the positive electrode current collector 50, and the negative electrode tab group 25 of the electrode body 20 is joined to the negative electrode current collector 60. Thereby, the sealing plate 14 and the electrode body 20 are integrated. Next, the sealing plate 14 is placed over the opening 12h of the exterior body 12, and the electrode body 20 is disposed inside the exterior body 12. Next, the sealing plate 14 is welded to the periphery of the opening 12h of the exterior body 12 to integrate the exterior body 12 and the sealing plate 14. Next, the non-aqueous electrolyte as described above is prepared and injected into the battery case 10 through the liquid injection hole 15 of the sealing plate 14. Thereby, the battery assembly for the first power storage device 110 and the battery assembly for the second power storage device 120 are manufactured.

[0074] (A-5) In the conditioning process, the fabricated battery assembly is charged at least once. Preferably, the fabricated battery assembly is charged and discharged at least once. The charging and discharging of the battery assembly can be performed in the same manner as in the prior art. Typically, an external power source is connected between the positive terminal 30 and the negative 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. In this way, the first power storage device 110 and the second power storage device 120, in which the basis weight and area of the active material layer are different (here, for each of the positive electrode 22 and the negative electrode 24, the basis weight and area of the active material layer are different), can be prepared.

[0075] (Step B) In the temperature distribution prediction step, the temperature distribution within the power storage module 500 when a plurality of power storage devices 100 are charged and discharged is predicted. That is, for example, in the aspect as shown in FIG. 5, both end portions in the arrangement direction X (particularly the front F portion in the arrangement direction X) are likely to be low-temperature regions A1. However, the temperature distribution within the power storage module 500 can also vary depending on the configuration of the cooling device 400 (for example, the installation position and number of the intake port IP, the exhaust port OP, and the air-cooling fan 410) and the heat dissipation path. Also, for example, the range (length in the arrangement direction X) of the low-temperature region A1 can also vary depending on, for example, the number of power storage devices 100 and the charge and discharge conditions. Therefore, it is preferable to predict the temperature distribution within the power storage module 500 during charging and discharging by means of a preliminary experiment or a simulation using commercially available analysis software. In particular, it is preferable to construct a power storage module for preliminary testing that simulates the power storage module 500, measure the temperature distribution, and predict the temperature distribution within the power storage module 500 based on the measurement.

[0076] In a preferred embodiment, first, a plurality of power storage devices for preliminary tests, different from the first power storage device 110 and the second power storage device 120 manufactured in the preparation step, are prepared, and a temperature sensor is attached to each of them. Next, using the plurality of power storage devices for preliminary tests, a power storage module for preliminary tests simulating the power storage module 500 is assembled. Next, the plurality of power storage devices for preliminary tests are actually charged and discharged (preferably high-rate charge and discharge), and the temperature distribution at this time is obtained. The charge and discharge conditions are preferably conditions assuming the actual usage mode. Then, based on the obtained temperature distribution, the temperature distribution within the power storage module 500 is predicted and divided, for example, into a low-temperature region A1 and a high-temperature region A2 (for example, divided into two parts).

[0077] (Step C) In the construction step, based on the temperature distribution predicted in the temperature distribution prediction step, the first power storage device 110 and the second power storage device 120 are arranged to construct the power storage module 500. Specifically, the first power storage device 110, which has a relatively small basis weight of the active material layer and a large area, is arranged in the region divided as the low-temperature region A1, and the second power storage device 120, which has a relatively large basis weight of the active material layer and a small area, is arranged in the region divided as the high-temperature region A2. Then, for example, together with a plurality of spacers 200, the first power storage device 110 and the second power storage device 120 are constrained by the constraint mechanism 300 and held integrally. In this way, the power storage module 500 can be constructed.

[0078] [Use of the power storage module] The power storage module 500 can be used for various applications. Since it has excellent high-rate tolerance, it can be suitably used as a power source (drive power source) for motors mounted on applications that require high output, such as vehicles like 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), battery electric vehicles (BEVs), etc. By mounting the power storage module 500 on a moving body such as a vehicle, the fuel consumption (electricity cost) of the moving body can be improved.

[0079] Hereinafter, several test examples related to the present invention will be described, but the present invention is not intended to be limited to such test examples.

[0080] In this test example, power storage devices with different basis weights and areas of the active material layer were constructed, and the high-rate tolerance was confirmed. Specifically, first, electrode bodies with the basis weights and areas shown in Table 1 for the positive electrode active material layer and the negative electrode active material layer were produced, respectively, and power storage devices (lithium-ion secondary batteries, Examples 1 to 4) were produced using these electrode bodies. Note that Table 1 shows the relative values when the basis weight and area of Example 2 are set to 1.00 (reference), respectively. Also, the basis weight and area were increased or decreased by the same ratio for both the positive electrode active material layer and the negative electrode active material layer. In addition, the configurations other than the basis weight and area of the positive electrode active material layer and the basis weight and area of the negative electrode active material layer were made common for all power storage devices.

[0081] 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 was performed at 150 A for 10 seconds, and the discharge resistance was measured. Next, the battery voltage drop ΔV that dropped in 10 seconds was read, and based on the battery voltage ΔV and the discharge current value (150 A), the IV resistance (initial resistance) was calculated.

[0082] Next, in a temperature environment of 25°C, the power storage device was adjusted to a state of SOC 50%, then constant current charging was performed at a charging rate of 150 A for 10 seconds, followed by a 5-second pause, and then constant current discharging was performed at a discharging rate of 10 A for 150 seconds, followed by a 5-second pause. One cycle of charge and discharge was defined as one cycle, and this was repeated 1000 times to conduct 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 the durability test / initial resistance). The results are shown in Table 1. Note that Table 1 shows the relative values when the resistance increase rate of Example 2 is set as 1.00 (reference).

[0083]

Table 1

[0084] As shown in Table 1, the smaller the basis weight of the power storage device, the smaller the increase in resistance after the high-rate durability test, that is, the higher the high-rate tolerance. Although not intended to be construed in a particularly limited manner, the reason for this is considered to be that the smaller the basis weight (here, relatively smaller thickness), the easier it is for the non-aqueous electrolyte to spread to the inside (deep part) of the active material layer, making it less likely to have uneven salt concentration, or the uneven salt concentration is more easily alleviated. As a result, it was difficult for the resistance to increase even when high-rate charge and discharge were repeated. From the above, it was verified from the experimental results that the power storage device with a small basis weight is relatively superior in high-rate tolerance compared to the power storage device with a large basis weight.

[0085] Although the preferred embodiments of the present invention have been described above, the above embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the content disclosed in this specification and common general knowledge in the art. The technology described in the claims includes various modifications and changes to the above-exemplified embodiments. For example, it is possible to replace a part of the above-described embodiments with other modified examples, and it is also possible to add other modified examples to the above-described embodiments. Further, if its technical features are not described as essential, it is also possible to appropriately delete them.

[0086] (1) For example, in the above-described embodiment, in the (step A) preparation step, the power storage device 100 with intentionally different basis weights of the active material layer was manufactured. However, it is not limited to this. For example, it is also possible to select and prepare the first power storage device 110 and the second power storage device 120 from among a number of power storage devices with varying basis weights of the active material layer within a predetermined range of acceptable products.

[0087] (2) For example, in the embodiment of FIG. 5 described above, both ends in the array direction X (the front F part and the rear Rr part in FIG. 5) are relatively low-temperature regions A1 with a low temperature, and the central part in the array direction X is a relatively high-temperature region A2 with a high temperature. However, it is not limited to this. As described above, the temperature distribution within the power storage module 500 can vary depending on the configuration of the cooling device 400 (for example, the intake port IP, the exhaust port OP, the installation position and number of the air-cooling fans 410), the number of power storage devices 100, the charge and discharge conditions, and the like. Also, in the embodiment of FIG. 5 described above, the inside of the power storage module 500 is divided into two temperature regions, a low-temperature region A1 and a high-temperature region A2, and furthermore, the temperature distribution is symmetric with respect to the array direction X. However, it is not limited to this. For example, the inside of the power storage module 500 can also be divided into three or more temperature regions. In that case, in the embodiment of FIG. 5, the low-temperature region A1 on the rear Rr side in the array direction X may be set as a medium-temperature region A3 that is higher in temperature than the low-temperature region A1 and lower in temperature than the high-temperature region A2. Also, when the cooling path and the heat dissipation path are complex, the temperature distribution may be random, for example, the low-temperature region A1 and the high-temperature region A2 may appear alternately. Hereinafter, several specific modification examples will be described with reference to FIGS. 6 to 9. Note that in FIGS. 6 to 9, the illustration of the cooling device is omitted.

[0088] (First Modification Example) FIG. 6 is a plan view of a power storage module 500a according to the first modification example. As described above, it is known that chain heat generation is likely to occur between the power storage devices 100 at the central part in the array direction X. Therefore, although not shown in FIG. 6, an intake port IP through which a refrigerant (air) is supplied and / or an air-cooling fan 410 may be additionally installed at the central part in the array direction X, and the central part may be strongly cooled. Then, as shown in FIG. 6, the temperature distribution of the power storage module 500a is, contrary to FIG. 5, such that the central part in the array direction X becomes a relatively low-temperature region A1, and both ends in the array direction X (the front F part and the rear Rr part in FIG. 6) may become relatively high-temperature regions A2.

[0089] In such cases, as shown in FIG. 6, a first power storage device 110 with a relatively small basis weight of the active material layer and a large area (high high-rate tolerance) is arranged at the center of the array direction X in the low-temperature region A1, and a second power storage device 120 with a relatively large basis weight and a small area (low high-rate tolerance) is arranged at both ends of the array direction X in the high-temperature region A2.

[0090] (Second and third modified examples) FIG. 7 is a plan view of a power storage module 500b according to the second modified example. FIG. 8 is a plan view of a power storage module 500c according to the third modified example. For example, when the air-cooling fan 410 installed on the front F side in the array direction X of FIG. 5 is powerful and has a high cooling capacity, as shown in FIGS. 7 and 8 respectively, the temperature distribution within the power storage modules 500b and 500c may be such that the front F portion in the array direction X becomes a low-temperature region A1 with a relatively low temperature, and the rear Rr portion in the array direction X becomes a high-temperature region A2 with a relatively high temperature.

[0091] In such cases, as shown in FIGS. 7 and 8, a first power storage device 110 with a relatively small basis weight of the active material layer and a large area (high high-rate tolerance) is arranged at the front F portion in the array direction X in the low-temperature region A1, and a second power storage device 120 with a relatively large basis weight and a small area (low high-rate tolerance) is arranged at the rear Rr portion in the array direction X in the high-temperature region A2.

[0092] Also, the distribution between the low-temperature region A1 and the high-temperature region A2 may vary depending on, for example, the number of power storage devices 100, charge and discharge conditions, etc. Therefore, the low-temperature region A1 and the high-temperature region A2 may be provided uniformly in the array direction X as shown in FIG. 7, or may be provided non-uniformly in the array direction X as shown in FIG. 8. In other words, the number of first power storage devices 110 and the number of second power storage devices 120 included in the power storage module 500 may be the same or different.

[0093] (Fourth Modification Example) FIG. 9 is a plan view of the power storage module 500d according to the fourth modification example. As shown in FIG. 9, the temperature distribution of the power storage module 500d is here divided in more detail than in FIG. 5. That is, both end portions in the arrangement direction X (the front F portion and the rear Rr portion in FIG. 6) are relatively low-temperature regions A1 where the temperature is low, the central portion in the arrangement direction X is a relatively high-temperature region A2 where the temperature is high, and between the low-temperature region A1 and the high-temperature region A2 is a medium-temperature region A3 where the temperature is higher than that of the low-temperature region A1 and lower than that of the high-temperature region A2.

[0094] In such a case, as shown in FIG. 9, first power storage devices 110 having a relatively small basis weight of the active material layer and a large area (high high-rate tolerance) are arranged at both end portions in the arrangement direction X, which are the low-temperature regions A1. Second power storage devices 120 having a relatively large basis weight and a small area (low high-rate tolerance) are arranged at the central portion in the arrangement direction X, which is the high-temperature region A2. Third power storage devices 130 having a basis weight of the active material layer smaller than that of the second power storage devices 120 and larger than that of the first power storage devices 110 are arranged in the medium-temperature region A3, which is intermediate between the low-temperature region A1 and the high-temperature region A2. In other words, it is preferable to arrange a plurality of power storage devices 100 so that the basis weight of the active material layer gradually decreases from the central portion to both end portions in the arrangement direction X in the order of the high-temperature region A2, the medium-temperature region A3, and the low-temperature region A1. Further, from the viewpoint of balancing the electrode capacity, it is preferable to arrange a plurality of power storage devices 100 so that the area of the active material layer gradually increases from the central portion to both end portions in the arrangement direction X in the order of the high-temperature region A2, the medium-temperature region A3, and the low-temperature region A1 as the basis weight decreases.

[0095] Note that in FIG. 9, the inside of the power storage module 500 is divided into three temperature regions, but it is of course possible to divide it into four or more temperature regions. By thus finely dividing the inside of the power storage module 500 according to the temperature distribution, the effects of the technology disclosed herein can be exhibited at a high level, and the high-rate tolerance of the entire power storage module 500 can be improved better.

[0096] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: A power storage module including a plurality of power storage devices, wherein each of the plurality of power storage devices has a first electrode including a first active material layer, and in the power storage module, when the plurality of power storage devices are charged and discharged, there are a low-temperature region where the temperature is relatively low and a high-temperature region where the temperature is relatively high. Among the plurality of power storage devices, the first power storage device disposed in the low-temperature region has a smaller basis weight of the first active material layer and a larger area of the first active material layer than the second power storage device disposed in the high-temperature region. Item 2: In the power storage module, there is a medium-temperature region between the low-temperature region and the high-temperature region, where the temperature is higher than that of the low-temperature region and lower than that of the high-temperature region. The plurality of power storage devices are arranged such that the 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. The power storage module according to Item 1. Item 3: The first active material layer is formed in a strip shape, and the first power storage device has a longer length in the longitudinal direction of the first active material layer than the second power storage device. The power storage module according to Item 1 or Item 2. Item 4: The first power storage device and the second power storage device have the same length in the short direction of the first active material layer. The power storage module according to Item 3. Item 5: Both the first power storage device and the second power storage device have a basis weight of the first active material layer within the range of 2 50 mg / cm 2 or less. The power storage module according to any one of Items 1 to 4. Item 6: Each of the plurality of power storage devices has a second electrode provided with a second active material layer. Among the plurality of power storage devices, the first power storage device disposed in the low-temperature region has a smaller basis weight of the second active material layer and a larger area of the second active material layer than the second power storage device disposed in the high-temperature region. The power storage module according to any one of Items 1 to 5. Item 7: When the ratio of the electrode capacity of the first electrode to the electrode capacity of the second electrode is defined as the opposing capacity ratio, the first power storage device and the second power storage device have the same opposing capacity ratio. The power storage module according to Item 6. Item 8: A method for manufacturing a power storage module including a plurality of power storage devices, each of the plurality of power storage devices having a first electrode provided with a first active material layer. As the plurality of power storage devices, a first power 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 power storage device having a large basis weight of the first active material layer and a relatively small area of the first active material layer are prepared. A preparation step, a temperature distribution prediction step of predicting the temperature distribution in the power storage module when the plurality of power storage devices are charged and discharged, and based on the temperature distribution, the first power storage device is disposed in a low-temperature region where the temperature is relatively low, and the second power storage device is disposed in a high-temperature region where the temperature is relatively high to construct the power storage module. A method for manufacturing a power storage module including a construction step.

Explanation of Reference Numerals

[0097] 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) 100 Power storage device 110 First power storage device 120 Second power storage device 130 Third power storage device 300 Constraint mechanism 400 Cooling device 410 Air-cooling fan 500 Power storage module A1 Low-temperature region A2 High-temperature region A3 Medium-temperature region

Claims

1. A power storage module including a plurality of power storage devices, wherein each of the plurality of power storage devices has a first electrode including a first active material layer, in the power storage module, when the plurality of power storage devices are charged and discharged, there are a low temperature region where the temperature is relatively low and a high temperature region where the temperature is relatively high, among the plurality of power storage devices, the first power storage device disposed in the low temperature region has a smaller basis weight of the first active material layer and a larger area of the first active material layer than the second power storage device disposed in the high temperature region, A power storage module.

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

3. The first active material layer is formed in a strip shape, the first power storage device has a longer length in the longitudinal direction of the first active material layer than the second power storage device, The power storage module according to claim 1.

4. The first power storage device and the second power storage device have the same length in the short direction of the first active material layer, The power storage module according to claim 3.

5. Both the first power storage device and the second power storage device have the basis weight of the first active material layer in the range of 1 mg / cm ２ or more and 50 mg / cm ２ or less. The power storage module according to any one of claims 1 to 4.

6. 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 disposed in the low temperature region has a smaller basis weight of the second active material layer and a larger area of the second active material layer than the second power storage device disposed in the high temperature region, The power storage module according to any one of claims 1 to 4.

7. When the ratio of the electrode capacity of the first electrode to the electrode capacity of the second electrode is defined as the opposing capacity ratio, the first power storage device and the second power storage device have the same opposing capacity ratio, The power storage module according to claim 6.

8. A method for manufacturing a power storage module including a plurality of power storage devices, wherein each of the plurality of power storage devices has a first electrode including a first active material layer, As the plurality of the power storage devices, a first power 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 power 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 are prepared in a preparation step. A temperature distribution prediction step of predicting a temperature distribution in the power storage module when the plurality of the 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 where the temperature is relatively low and arranging the second power storage device in a high temperature region where the temperature is relatively high based on the temperature distribution. Including A method for manufacturing a power storage module.

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