Electricity storage module and electricity storage device

Abstract

Providing a technique for improving safety in use of a power storage module while increasing energy density of the power storage module SOLUTION: According to the technology disclosed herein, a power storage module is provided. The power storage module includes a plurality of power storage devices, a bus bar, and a cooling unit. Each of the plurality of power storage devices includes an electrode assembly including a positive electrode and a negative electrode, and a case that houses the electrode assembly. The case has a bottom surface, an upper surface facing the bottom surface, and a side surface provided between the bottom surface and the upper surface. The bus bar is a member that connects the power storage devices. The cooling unit is provided on a bottom surface side of the power storage device. The positive electrode has a first region on the bottom surface side and a second region on the upper surface side. The first region includes a first positive electrode active material that is a positive electrode active material having a relatively large amount of Ni. The second region includes a second positive electrode active material that is a positive electrode active material having a relatively small amount of Ni.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an energy storage module and an energy storage device. [Background technology]

[0002] An example of a power storage module is a power storage module that includes a secondary battery such as a lithium-ion secondary battery as a power storage device. In recent years, this type of power storage module has been suitably used as a power source for driving vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] The battery pack disclosed in JP 2019-185845 A includes a filler member. The filler member has a thickness direction and a plane direction perpendicular to the thickness direction, and has a first surface and a second surface along the plane direction. The first surface is in contact with the plurality of unit cells constituting the battery pack, and the second surface is in contact with a cooling member capable of cooling the unit cells. When one of the unit cells constituting the battery pack is designated as the first unit cell, the heat transfer sensitivity S of the filler member when heat generated from the first unit cell transfers to a second unit cell adjacent to the first unit cell via the filler member and the cooling member is defined by Equation 1. Equation 1 is: Heat transfer sensitivity S of the filler member [W / K] = Thermal conductivity k of the filler member [W / m K] × Contact area A between the filler member and the first and second unit cells [m 2 ] / thickness d of the filling member [m]. When the temperature of the first cell reaches or exceeds the temperature of the abnormal heat generation state, the heat transfer sensitivity satisfies Equation 2. Equation 2 is 0.5≦S≦4.0. The publication states that this configuration makes it possible to suitably control heat transfer between cells via the cooling member in a battery pack including multiple cells. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-185845 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to increase the energy density of an energy storage module, it has been considered to increase the amount of nickel (Ni) in the positive electrode active material of the energy storage device included in the energy storage module. However, since increasing the amount of Ni tends to increase the amount of heat generated during use of the energy storage module and the energy storage device, there is still room for improvement in terms of using them more safely. Therefore, the present inventors have conducted extensive research to increase the energy density of the energy storage module while improving the safety of the use of the energy storage module. [Means for solving the problem]

[0006] The technology disclosed herein provides an energy storage module. The energy storage module includes a plurality of energy storage devices, a bus bar, and a cooling unit. The plurality of energy storage devices include an electrode assembly including a positive electrode and a negative electrode, and a case that houses the electrode assembly. The case has a bottom surface, a top surface facing the bottom surface, and a side surface provided between the bottom surface and the top surface. The bus bar is a member that connects the energy storage devices. The cooling unit is provided on the bottom surface side of the energy storage device. The positive electrode has a first region on the bottom surface side and a second region on the top surface side. The first region contains a first positive electrode active material that is a positive electrode active material with a relatively high Ni content. The second region contains a second positive electrode active material that is a positive electrode active material with a relatively low Ni content. This configuration can increase the energy density of the energy storage module while improving the safety of the energy storage module during use.

[0007] The technology disclosed herein provides an energy storage device. The energy storage device includes an electrode assembly including a positive electrode and a negative electrode, and a case that houses the electrode assembly. The case has a bottom surface, a top surface facing the bottom surface, and a side surface provided between the bottom surface and the top surface. The positive electrode has a first region on the bottom surface side and a second region on the top surface side. The first region contains a first positive electrode active material that is a positive electrode active material with a relatively high Ni content. The second region contains a second positive electrode active material that is a positive electrode active material with a relatively low Ni content. This configuration can increase the energy density of the energy storage module while improving the safety of the energy storage module during use. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of the power storage module 1000. FIG. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is a perspective view of the electricity storage device 100. As shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a partial perspective view of the electrode body 20. As shown in FIG. [Figure 6] FIG. 6 is a schematic diagram of the electrode body 220. [Figure 7] FIG. 7 is a schematic side view of the power storage module 3000. As shown in FIG. [Figure 8] FIG. 8 is a schematic perspective view of the power storage device 3100. As shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a partial perspective view of the electrode body 320. [Figure 11] FIG. 11 is a schematic diagram of the electrode body 420. As shown in FIG. [Figure 12] FIG. 12 is a plan view of the positive electrode 422. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the energy storage device disclosed herein is described below. The embodiment described herein does not particularly limit the technology disclosed herein. The technology disclosed herein is not limited to the embodiment described herein unless otherwise specified. The drawings are schematic and do not necessarily reflect the actual product. Components and parts that perform the same function are appropriately designated with the same reference numerals, and redundant explanations may be omitted. The reference numerals "R," "L," "U," "D," "F," and "Rr" in the drawings represent "right," "left," "up," "down," "front," and "rear," respectively. The notation "A to B" indicating a numerical range means "greater than A and less than B" unless otherwise specified, and also encompasses the meaning of "greater than A and less than B."

[0010] In this specification, the term "electricity storage device" refers to a device in which charging and discharging occur by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. Electricity storage devices include secondary batteries such as lithium ion secondary batteries. The electricity storage device may be, for example, a lithium ion secondary battery.

[0011] First Embodiment FIG. 1 is a perspective view of an energy storage module 1000. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. As shown in FIGS. 1 and 2, the energy storage module 1000 includes a plurality of energy storage devices 100, a bus bar 2A, a module case 3A, a cooling unit 4A, and a spacer 5A. As shown in FIG. 1, in the energy storage module 1000, the plurality of energy storage devices 100 are arranged in a first direction P. In the first direction P, the energy storage devices 100 are arranged such that the first side surfaces 12b of the energy storage devices 100 face each other. A spacer 5A is sandwiched between the energy storage devices. In the embodiment shown in FIGS. 1 and 2, the first direction P is a direction from the rear (Rr) to the front (F).

[0012] Here, the power storage device 100 is a lithium-ion secondary battery. FIG. 3 is a perspective view of the power storage device 100. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. As shown in FIGS. 3 and 4, the power storage device 100 includes a case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, a negative electrode current collector 60, an electrode assembly holder 29, and insulating members 92 and 94. The case 10 is, for example, an outer container that houses the electrode assembly 20 and a nonaqueous electrolyte (not shown). Here, the case 10 is a flat, rectangular case. As shown in FIGS. 3 and 4, the case 10 includes a main body 12 and a sealing plate 14. In this embodiment, the main body 12 includes a bottom surface 12a, an opening 12h, and side surfaces that are a pair of opposing first side surfaces 12b and a pair of opposing second side surfaces 12c. The bottom surface 12a is, for example, rectangular (including substantially rectangular; the same applies below) and constitutes the lower surface of the case 10. The opening 12h faces the bottom surface 12a and is closed by the sealing plate 14. Therefore, the sealing plate 14 disposed at the opening 12h constitutes the upper surface of the case 10. The pair of opposing first side surfaces 12b and the pair of opposing second side surfaces 12c are provided between the bottom surface 12a and the sealing plate 14 (upper surface) here. The pair of opposing first side surfaces 12b extend from a pair of opposing long sides of the bottom surface 12a. The pair of opposing second side surfaces 12c extend from a pair of opposing short sides of the bottom surface 12a.

[0013] The sealing plate 14 is, for example, a member that closes the opening 12h of the case 10. In this embodiment, the sealing plate 14 is flat and has a shape (here, rectangular) corresponding to the shape of the opening 12h. As shown in FIGS. 3 and 4 , the sealing plate 14 has a liquid inlet 15, a gas release valve 17, and terminal outlet holes 18 and 19. The liquid inlet 15 is, for example, a through-hole for injecting a nonaqueous electrolyte into the case 10. In this example, the liquid inlet 15 is sealed with a sealing member 16. The gas release valve 17 is, for example, a thin-walled portion that breaks when the pressure inside the case 10 reaches or exceeds a predetermined value, thereby releasing gas inside the case 10 to the outside. The terminal outlet hole 18 is, for example, a through-hole through which a portion of the positive electrode terminal 30 is inserted. The terminal outlet hole 19 is, for example, a through-hole through which a portion of the negative electrode terminal 40 is inserted.

[0014] The electrode assembly 20 is, for example, a power generating element of the electricity storage device 100 and includes a positive electrode 22 and a negative electrode 24. FIG. 5 is a partial perspective view of the electrode assembly 20. FIG. 5 shows a portion of the laminated structure of the electrode assembly 20, which includes the positive electrode 22, the negative electrode 24, and the separator 26. As shown in FIG. 5, the electrode assembly 20 is a laminated electrode assembly including a sheet-shaped positive electrode 22, a sheet-shaped negative electrode 24, and a sheet-shaped separator 26 interposed between the positive electrode 22 and the negative electrode 24. In this embodiment, the electrode assembly 20 has four laminated surfaces on which the positive electrodes 22 and the negative electrodes 24 are laminated. As shown in FIG. 4, these four laminated surfaces face the bottom surface 12a, a pair of opposing second side surfaces 12c, and the sealing plate 14 within the case 10. Of these four stacking surfaces, a positive electrode tab group 23 and a negative electrode tab group 25 are provided on the stacking surface facing the sealing plate 14.

[0015] As shown in FIG. 5, the positive electrode 22 includes a positive electrode active material layer 22a, a positive electrode current collector foil 22c, and a protective layer 22p. The positive electrode current collector foil 22c is, for example, a sheet-like aluminum foil. In this embodiment, the positive electrode current collector foil 22c has a rectangular main body and a positive electrode tab 22t protruding from the main body. The positive electrode current collector foil 22c has a region where the positive electrode active material layer 22a is provided and a region where the positive electrode active material layer 22a is not provided. The region where the positive electrode active material layer 22a is not provided includes, for example, a region where the protective layer 22p is provided and a region where the positive electrode current collector foil 22c is exposed.

[0016] In the embodiment shown in Fig. 5, the positive electrode active material layer 22a is provided in a rectangular shape on the positive electrode current collector foil 22c. Here, the positive electrode active material layer 22a is not provided in the region along the long side of the positive electrode current collector foil 22c on the positive electrode tab 22t side. The positive electrode active material layer 22a may be provided, for example, on one side or both sides (here, both sides) of the positive electrode current collector foil 22c. In this embodiment, the positive electrode active material layer 22a has a first positive electrode active material layer 22a1 and a second positive electrode active material layer 22a2.

[0017] The first positive electrode active material layer 22a1 is provided, for example, in the first region R1 on the bottom surface 12a side. The first positive electrode active material layer 22a1 contains, for example, a first positive electrode active material. The first positive electrode active material is not particularly limited as long as it contains, for example, nickel (Ni) and has a larger Ni content than the Ni content in the second positive electrode active material described below. The first positive electrode active material may be, for example, a lithium transition metal composite oxide containing Ni. The first positive electrode active material may be composed of one type alone or two or more types.

[0018] The first positive electrode active material is, for example, a compound represented by the following general formula (1): Li 1+a1 Ni x1 Mn y1 M1 z1 O2(1) In the formula, M1 is one or more metal elements selected from Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, W, etc., a1 satisfies -0.1≦a1≦0.1, x1 satisfies 0.7≦x1≦1.0, y1 satisfies 0≦y1≦0.3, and z1 satisfies 0≦z1≦0.3. Furthermore, x1, y1, and z1 satisfy x1+y1+z1=1. Although not particularly limited, the first positive electrode active material may be, for example, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNiO2, etc. can be preferably used.

[0019] The first positive electrode active material layer 22a1 may contain a positive electrode active material different from the first positive electrode active material, as long as the effects of the technology disclosed herein can be achieved. The type of the positive electrode active material contained in the first positive electrode active material layer 22a1 is not particularly limited. When the total positive electrode active material in the first positive electrode active material layer 22a1 is taken as 100% by mass, the content of the first positive electrode active material is generally 70% by mass or more, for example, 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more or 98% by mass or more. The closer to 100% by mass, the better.

[0020] The second positive electrode active material layer 22a2 is provided, for example, in the second region R2 on the upper surface (here, sealing plate 14) side. The second positive electrode active material layer 22a2 contains, for example, a second positive electrode active material. The second positive electrode active material is not particularly limited as long as it contains, for example, nickel (Ni) and the amount of Ni is smaller than the amount of Ni in the first positive electrode active material. The second positive electrode active material may be, for example, a lithium transition metal composite oxide containing Ni. The second positive electrode active material may be composed of one type alone or two or more types.

[0021] The second positive electrode active material is, for example, a compound represented by the following general formula (2): Li 1+a2 Ni x2 Mn y2 M2 z2 O2(2) In the formula, M2 is one or more metal elements selected from Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, W, etc., a2 satisfies -0.1≦a2≦0.1, x2 satisfies 0.3≦x2<0.7, y2 satisfies 0≦y2≦0.7, and z2 satisfies 0≦z2≦0.7. Furthermore, x2, y2, and z2 satisfy x2+y2+z2=1. Although not particularly limited, the first positive electrode active material may be, for example, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 and the like can be preferably used.

[0022] The second positive electrode active material layer 22a2 may contain a positive electrode active material different from the second positive electrode active material, as long as the effects of the technology disclosed herein can be achieved. The type of the positive electrode active material contained in the second positive electrode active material layer 22a2 is not particularly limited. When the entire positive electrode active material in the second positive electrode active material layer 22a2 is taken as 100% by mass, the content of the second positive electrode active material is generally 70% by mass or more, for example, 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more or 98% by mass or more. The closer to 100% by mass, the better.

[0023] In the embodiment shown in FIG. 5, the first region R1 may be located on one of a pair of opposing long sides of the positive current collector foil 22c on which the positive electrode tab 22t is not provided. From the viewpoint of achieving a high energy density of the power storage device 100, the first region R1 may have an area of, for example, 20% or more, preferably 30% or more, and more preferably 40% or more of the entire area of ​​the main body of the positive electrode current collector foil 22c (here, the portion of the positive electrode current collector foil 22c excluding the positive electrode tab 22t). From the viewpoint of improving the safety of the power storage device 100, the first region R1 may have an area of, for example, 80% or less, preferably 70% or less, and more preferably 60% or less of the entire area of ​​the main body of the positive electrode current collector foil 22c. Note that in this embodiment, the area of ​​the first region R1 is the same as the area of ​​the first positive electrode active material layer 22a1.

[0024] In the embodiment shown in FIG. 5, the second region R2 may be set on one of a pair of opposing long sides of the positive electrode current collector foil 22c, the long side on which the positive electrode tab 22t is provided. From the viewpoint of improving the safety of the power storage device 100, the second region R2 may have an area of, for example, 20% or more, preferably 30% or more, and more preferably 40% or more of the entire area of ​​the positive electrode current collector foil 22c. From the viewpoint of achieving a high energy density of the power storage device 100, the second region R2 may have an area of, for example, 80% or less, preferably 70% or less, and more preferably 60% or less of the entire area of ​​the positive electrode current collector foil 22c. Note that in this embodiment, the area of ​​the second region R2 is the same as the area of ​​the second positive electrode active material layer 22a2.

[0025] The area of ​​the first region R1 and the area of ​​the second region R2 may be the same or different. The area of ​​the first region R1 and the area of ​​the second region R2 may be set appropriately while taking into consideration, for example, the balance between the safety of the power storage device 100 and the increase in energy of the power storage device 100.

[0026] 5, the positive electrode active material layer 22a includes a first positive electrode active material layer 22a1 and a second positive electrode active material layer 22a2. However, the positive electrode active material layer 22a may include, for example, another positive electrode active material layer different from the first positive electrode active material layer 22a1 and the second positive electrode active material layer 22a2, as long as the effects of the technology disclosed herein can be achieved. The other positive electrode active material layer may include, for example, a positive electrode active material different from the first positive electrode active material and the second positive electrode active material.

[0027] The positive electrode active material layer 22a may contain, for example, a conductive material, a binder, etc. in addition to the positive electrode active material. Examples of the conductive material include carbon black such as acetylene black (AB) and other carbon materials such as graphite. Examples of the binder include polyvinylidene fluoride (PVDF). The content of the positive electrode active material relative to the entire positive electrode active material layer 22a is preferably 70 mass % or more, more preferably 80 mass % to 97 mass %, and even more preferably 85 mass % to 96 mass %. The content of the conductive material relative to the entire positive electrode active material layer 22a is, for example, 0.1 mass % to 10 mass %. The content of the binder relative to the entire positive electrode active material layer 22a is, for example, 0.5 mass % to 10 mass %.

[0028] The protective layer 22p may be provided, for example, closer to the upper surface (here, the sealing plate 14) than the second region R2. In the embodiment shown in FIGS. 4 and 5, the protective layer 22p is provided along one of a pair of opposing long sides of the positive electrode current collector foil 22c, on which the positive electrode tab 22t is provided, and is provided on the base end side of the positive electrode tab 22t. The base end of the positive electrode tab 22t here refers to the boundary between the positive electrode tab 22t and the rectangular main body of the positive electrode current collector foil 22c. The protective layer 22p includes, for example, an insulating inorganic filler (e.g., alumina). Note that the protective layer 22p does not necessarily have to be provided. For this reason, in other embodiments, the protective layer 22p is not provided (see the third and fourth embodiments described below).

[0029] The positive electrode tab 22t is, for example, a portion connected to the positive electrode current collector 50. In the embodiment shown in FIG. 4, the positive electrode tab 22t protrudes from the long side of a pair of opposing long sides of the positive electrode current collector foil 22c that is closer to the upper surface (here, the sealing plate 14). Neither the positive electrode active material layer 22a nor the protective layer 22p is provided on the protruding tip side of the positive electrode tab 22t. In this embodiment, in the electrode assembly 20, the positive electrode tabs 22t of the respective positive electrodes 22 are stacked to form a positive electrode tab group 23.

[0030] As shown in Fig. 5, the negative electrode 24 includes a negative electrode active material layer 24a and a negative electrode current collector foil 24c. The negative electrode current collector foil 24c is, for example, a sheet-like copper foil. The negative electrode current collector foil 24c has a rectangular main body and a negative electrode tab 24t protruding from the main body. The negative electrode current collector foil 24c has a region where the negative electrode active material layer 24a is provided and a region where the negative electrode active material layer 24a is not provided. The region where the negative electrode active material layer 24a is not provided is, for example, a region where the negative electrode current collector foil 24c is exposed.

[0031] 5, the negative electrode active material layer 24a is provided in a rectangular shape on the entire negative electrode current collector foil 24c except for the negative electrode tab 24t. The negative electrode active material layer 24a may be provided, for example, on one or both sides (both sides in this example) of the negative electrode current collector foil 24c.

[0032] The negative electrode active material layer 24a contains, for example, a negative electrode active material. Examples of the negative electrode active material include carbon materials such as natural graphite and artificial graphite; silicon; and the like. The negative electrode active material layer 24a may contain, in addition to the negative electrode active material, for example, a binder, a thickener, and the like. Examples of the binder include styrene butadiene rubber (SBR). Examples of the thickener include carboxymethyl cellulose (CMC). The content of the negative electrode active material relative to the entire negative electrode active material layer 24a is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% to 99% by mass, and may be 95% to 99% by mass. The content of the binder relative to the entire negative electrode active material layer 24a is, for example, 0.5% to 10% by mass.

[0033] The negative electrode tab 24t is a portion that is connected to, for example, the negative electrode current collector 60. In the embodiment shown in FIG. 4, the negative electrode tab 24t protrudes from the long side of a pair of opposing long sides of the negative electrode current collector foil 24c that is closer to the upper surface (here, the sealing plate 14). The negative electrode tab 24t is not provided with a negative electrode active material layer 24a. In this embodiment, the negative electrode tabs 24t of the respective negative electrodes 24 are stacked on top of each other in the electrode assembly 20 to form a negative electrode tab group 25.

[0034] Examples of separator 26 include porous sheets (films) made of resin materials such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. The porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) may be provided on the surface of separator 26.

[0035] The non-aqueous electrolyte solution contains, for example, a non-aqueous solvent and a supporting salt. Examples of the non-aqueous solvent include organic solvents used in this type of application, such as carbonates, ethers, esters, nitriles, sulfones, and lactones. Among these, carbonates are preferably used. Examples of carbonates include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC). As the non-aqueous solvent, one type of non-aqueous solvent may be used alone, or two or more types of non-aqueous solvents may be used in combination. Examples of the supporting salt include lithium salts such as LiPF6. The concentration of the supporting salt is preferably 0.7 mol / L to 1.4 mol / L, for example. The non-aqueous electrolyte solution may contain additives used in this type of application, if necessary.

[0036] The positive electrode terminal 30 is, for example, a portion electrically connected to the positive electrode 22 of the electrode assembly 20. As shown in FIGS. 3 and 4, the positive electrode terminal 30 is attached to the sealing plate 14. As shown in FIG. 4, the positive electrode terminal 30 is inserted through the terminal pull-out hole 18, with a portion disposed inside the case 10 and a portion disposed outside the case 10. The portion of the positive electrode terminal 30 disposed inside the case 10 is connected to the positive electrode current collector 50. The portion of the positive electrode terminal 30 disposed outside the case 10 is connected to the bus bar 2A (see FIGS. 1 and 2). The positive electrode terminal 30 is made of, for example, aluminum or an aluminum alloy.

[0037] The negative electrode terminal 40 is, for example, a portion electrically connected to the negative electrode 24 of the electrode assembly 20. As shown in FIGS. 3 and 4, the negative electrode terminal 40 is attached to the sealing plate 14. As shown in FIG. 4, the negative electrode terminal 40 is inserted through the terminal pull-out hole 19, with a portion disposed inside the case 10 and a portion disposed outside the case 10. The portion of the negative electrode terminal 40 disposed inside the case 10 is connected to the negative electrode current collector 60. The portion of the negative electrode terminal 40 disposed outside the case 10 is connected to the bus bar 2A (see FIGS. 1 and 2). The negative electrode terminal 40 is made of, for example, copper or a copper alloy.

[0038] The positive electrode current collector 50 is, for example, a portion electrically connected to the positive electrode 22 of the electrode assembly 20. As shown in FIG. 4, the positive electrode current collector 50 is flat and arranged along the inner surface of the sealing plate 14. In this example, the positive electrode tab group 23 is connected (welded) to the positive electrode current collector 50, and the tip 30c of the positive electrode terminal 30 is also connected to the positive electrode current collector 50. The positive electrode current collector 50 is made of, for example, aluminum or an aluminum alloy.

[0039] The negative electrode current collector 60 is, for example, a portion electrically connected to the negative electrode 24 of the electrode assembly 20. As shown in FIG. 4, the negative electrode current collector 60 is flat and arranged along the inner surface of the sealing plate 14. In this example, the negative electrode tab group 25 is connected (welded) to the negative electrode current collector 60, and the tip 40c of the negative electrode terminal 40 is also connected to the negative electrode current collector 60. The negative electrode current collector 60 is made of, for example, copper or a copper alloy.

[0040] The electrode assembly holder 29 is, for example, a member that prevents electrical conduction between the electrode assembly 20 and the case 10. As shown in FIG. 4 , the electrode assembly holder 29 is housed within the case 10 with the electrode assembly 20 housed therein. The insulating member 92 is, for example, a member that prevents electrical conduction between the positive electrode terminal 30 and the sealing plate 14 and between the negative electrode terminal 40 and the sealing plate 14. As shown in FIGS. 3 and 4 , the insulating member 92 has a portion that is arranged along the outer surface of the sealing plate 14 and a portion that is arranged along the inner periphery of the terminal lead-out hole 18 or 19. The insulating member 94 is a member that prevents electrical conduction between the positive electrode current collector 50 and the sealing plate 14 and between the negative electrode current collector 60 and the sealing plate 14. As shown in FIG. 4 , the insulating member 94 is arranged along the inner surface of the sealing plate 14. Although not particularly limited, examples of constituent materials of various insulating members include polyolefin resins such as polypropylene (PP) and polyethylene (PE); fluorine-based resins such as perfluoroalkoxyalkane and polytetrafluoroethylene (PTFE); and the like.

[0041] The bus bar 2A is, for example, a member that electrically connects the respective power storage devices 100. The bus bar 2A has, for example, a flat plate shape. As shown in FIGS. 1 and 2 , the bus bar 2A spans two power storage devices 100 adjacent to each other in a first direction P. In this embodiment, the bus bar 2A spans the positive electrode terminal 30 of one of the two power storage devices 100 adjacent to each other in the first direction P and the negative electrode terminal 40 of the other power storage device 100. The bus bar 2A is made of, for example, aluminum or an aluminum alloy. Although not particularly limited, the bus bar 2A and the positive electrode terminal 30 or the negative electrode terminal 40 may be joined by a conventionally known joining method such as ultrasonic welding, laser welding, or resistance welding.

[0042] The module case 3A is, for example, a member that restrains the multiple power storage devices 100 in a first direction P. As shown in FIG. 1 , the module case 3A includes a pair of end plates 31A, a pair of side plates 32A, a bottom plate 33A, and multiple screws 34A. The pair of end plates 31A are arranged to sandwich the multiple power storage devices 100 arranged in the first direction P. The pair of side plates 32A spans between one end plate 31A and the other end plate 31A and is fixed to the end plate 31A by multiple screws 34A. This applies a restraining pressure in the same direction to the multiple power storage devices 100 arranged in the first direction P (in FIG. 2 , the multiple power storage devices 100 arranged in the first direction P with spacers 5A interposed therebetween). The magnitude of the restraining pressure is not particularly limited and can be set appropriately. 1 and 2, the bottom plate 33A is disposed on the bottom surfaces 12a of the plurality of power storage devices 100 so as to be in contact with the bottom surfaces 12a. Although not particularly limited, the pair of end plates 31A, the pair of side plates 32A, and the bottom plate 33A may be made of metal, for example. The pair of side plates 32A and the bottom plate 33A may include, for example, a resin material in part.

[0043] The cooling unit 4A is, for example, a portion that cools a plurality of power storage devices 100. In the embodiment shown in FIG. 2, the cooling unit 4A is provided on the bottom plate 33A. In this embodiment, the cooling unit 4A includes a flow path 410 and a cooler (not shown). The flow path 410 is, for example, a portion through which a refrigerant flows. In this embodiment, the flow path 410 is provided on the bottom plate 33A. The cooler is, for example, a supply source that supplies the refrigerant. The cooler may be connected to the flow path 410. The refrigerant may have a sufficient cooling effect when the temperature of the power storage device 100 reaches or exceeds a predetermined value. Examples of the refrigerant include a mixture of water and a non-flammable and insulating solvent. Examples of the solvent include diisopropylnaphthalene; 1-phenyl-1-(3,4-dimethylphenyl)ethane; liquid cellulose; glycols such as ethylene glycol and propylene glycol; carbon tetrachloride; and the like. The refrigerant may contain an additive used in this type of application as needed. Alternatively, the refrigerant may be a gas such as outside air. Although not shown, a heat transfer member may be disposed between the power storage device 100 and the cooling unit 4A as needed. The heat transfer member may be, for example, a gap filler. Examples of such gap fillers include thermally conductive silicone resins that are initially in a gel state and harden into a solid after application.

[0044] The spacer 5A is, for example, a member that assists in restraining each of the power storage devices 100. The spacer 5A may be, for example, flat. As shown in FIGS. 1 and 2, the spacer 5A is disposed between two power storage devices 100 adjacent to each other in the first direction P. In this embodiment, the spacer 5A is disposed between two opposing first side surfaces 12b of the two power storage devices 100 adjacent to each other in the first direction P. Although not particularly limited, the spacer 5A is made of, for example, metal or resin.

[0045] As described above, the energy storage module 1000 includes a plurality of energy storage devices 100, a bus bar 2A, and a cooling unit 4A. Each of the energy storage devices 100 includes an electrode assembly 20 including a positive electrode 22 and a negative electrode 24, and a case 10 that houses the electrode assembly 20. The case 10 has a bottom surface 12a, an upper surface (here, a sealing plate 14) facing the bottom surface 12a, and side surfaces 12b and 12c provided between the bottom surface 12a and the upper surface. The bus bar 2A is a member that connects the energy storage devices 100. The cooling unit 4A is provided on the bottom surface 12a side of the energy storage device 100. The positive electrode 22 includes a first region R1 on the bottom surface 12a side and a second region R2 on the upper surface (here, the sealing plate 14) side. The first region R1 contains a first positive electrode active material that is a positive electrode active material with a relatively large amount of Ni. The second region R2 contains a second positive electrode active material that is a positive electrode active material with a relatively small amount of Ni.

[0046] In the power storage module 1000, a cooling unit 4A is disposed on the bottom surface 12a side of the power storage device 100. This can suppress heat generation in the power storage device 100. In the positive electrode 22 of the power storage device 100, a first region R1 on the bottom surface 12a side contains a first positive electrode active material having a relatively large amount of Ni, and a second region R2 on the top surface (sealing plate 14) side contains a second positive electrode active material having a relatively small amount of Ni. Here, the first positive electrode active material, due to its relatively large amount of Ni, can contribute to a higher energy density of the power storage device 100 and the power storage module 1000 than the second positive electrode active material, but can generate a larger amount of heat during use of the power storage device 100. The second positive electrode active material, due to its relatively small amount of Ni, can generate a smaller amount of heat in the power storage device 100 and the power storage module 1000 than the first positive electrode active material. In the energy storage module 1000, the first positive electrode active material is disposed on the bottom surface 12a side where the cooling unit 4A is provided, and therefore heat generation by the first positive electrode active material can be eliminated. This makes it possible to achieve a high energy density in the energy storage module 1000 and to improve the safety of using the energy storage module 1000.

[0047] The case 10 may have a rectangular bottom surface 12a, a pair of first side surfaces 12b extending from a pair of opposing long sides of the bottom surface 12a, and a pair of second side surfaces 12c extending from a pair of opposing short sides of the bottom surface 12a. The case 10 may have a positive electrode terminal 30 and a negative electrode terminal 40 on its top surface (here, the sealing plate 14). The multiple electricity storage devices 100 may be arranged such that the first side surfaces 12b of the electricity storage devices 100 face each other. The bus bar 2A may bridge between the positive electrode terminal 30 of one of two electricity storage devices 100 adjacent to each other in a first direction P in which the multiple electricity storage devices 100 are arranged, and the negative electrode terminal 40 of the other electricity storage device 100. In the electricity storage module 1000, the connection portion between the electrode terminal and the bus bar 2A is a portion that is likely to generate heat, and is provided on the top surface of the case 10. Therefore, the connection portion between the electrode terminal and the bus bar 2A is located away from the first region R1 including the first positive electrode active material, which makes it possible to suppress an increase in the amount of heat generated by the energy storage module 1000 during use, and further improves the safety of the energy storage module 1000 during use.

[0048] The energy storage module 1000 and the energy storage device 100 may include, as the electrode assembly 20, a laminated electrode assembly including a sheet-shaped positive electrode 22, a sheet-shaped negative electrode 24, and a sheet-shaped separator 26 interposed between the positive electrode 22 and the negative electrode 24. In the laminated electrode assembly, the four side surfaces are electrode stacking surfaces (open surfaces), which, for example, allows heat to be released from the interior more efficiently. For this reason, by including a laminated electrode assembly as the electrode assembly 20, the safety of use of the energy storage module 1000 can be further improved. In addition to this, the laminated electrode assembly can be produced more easily than, for example, a wound electrode assembly, which will be described later. For this reason, in addition to the above-mentioned effects, the productivity of the energy storage module 1000 can be increased.

[0049] The first positive electrode active material is represented by the following general formula (1): Li 1+a1 Ni x1 Mn y1 M1 z1 O2(1) [wherein M1 is one or more metal elements selected from Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and -0.1≦a1≦0.1, 0.7≦x1≦1.0, 0≦y1≦0.3, 0≦z1≦0.3, and x1+y1+z1=1 is satisfied.] The second positive electrode active material may be a compound represented by the following general formula (2): Li 1+a2 Ni x2 Mn y2 M2 z2 O2(2) [wherein M2 is one or more metal elements selected from Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and -0.1≦a2≦0.1, 0.3≦x2<0.7, 0≦y2≦0.7, 0≦z2≦0.7, and x2+y2+z2=1 is satisfied.] By using a compound represented by general formula (1) as the first positive electrode active material and a compound represented by general formula (2) as the second positive electrode active material, the effects of the technology disclosed herein can be better realized.

[0050] Although one embodiment of the technology disclosed herein has been described above, the above embodiment is merely an example. The technology disclosed herein may include modifications and alterations of the above embodiment. Note that in the embodiments described below, descriptions of parts common to the above embodiment will be omitted to avoid duplication.

[0051] Second Embodiment In the first embodiment described above, the energy storage module 1000 includes the electrode assembly 20, which is a laminated electrode assembly. However, the technology disclosed herein is not limited to this. The energy storage module 1000 may include, for example, an electrode assembly 220 shown in FIG. 6 instead of the electrode assembly 20. FIG. 6 is a schematic diagram of the electrode assembly 220. As shown in FIG. 6, the electrode assembly 220 is a wound electrode assembly in which a long sheet-like positive electrode 222 and a long sheet-like negative electrode 224 are wound around a winding axis WL with a long sheet-like separator 226 interposed therebetween. In this embodiment, the electrode assembly 220 has two laminated surfaces (open surfaces) where the positive electrode 222 and the negative electrode 224 are laminated. In this embodiment, these two laminated surfaces face the bottom surface 12a and the sealing plate 14 inside the case 10 (see FIG. 4). Of these two stacking surfaces, a positive electrode tab group and a negative electrode tab group may be provided on the stacking surface facing the sealing plate 14. In the embodiment shown in Fig. 6, the positive electrode tab group may be composed of a plurality of positive electrode tabs 222t. The negative electrode tab group may be composed of a plurality of negative electrode tabs 224t.

[0052] As shown in FIG. 6, the positive electrode 222 includes a positive electrode active material layer 222a, a positive electrode current collector foil 222c, and a protective layer 222p. The positive electrode current collector foil 222c is, for example, a long sheet of aluminum foil. In this embodiment, the positive electrode current collector foil 222c has a long, strip-shaped main body and a positive electrode tab 222t protruding from the main body. The positive electrode current collector foil 222c has a region where the positive electrode active material layer 222a is provided and a region where the positive electrode active material layer 222a is not provided. The region where the positive electrode active material layer 222a is not provided includes, for example, a region where the protective layer 222p is provided and a region where the positive electrode current collector foil 222c is exposed.

[0053] 6, the positive electrode active material layer 222a is provided in a strip shape on the positive electrode current collector foil 222c along the longitudinal direction LD. Here, the positive electrode active material layer 222a is not provided in the region along the longitudinal direction LD of the positive electrode current collector foil 222c on the positive electrode tab 222t side. The positive electrode active material layer 222a may be provided on, for example, one or both sides (here, both sides) of the positive electrode current collector foil 222c. In this embodiment, the positive electrode active material layer 222a has a first positive electrode active material layer 222a1 and a second positive electrode active material layer 222a2.

[0054] In the embodiment shown in FIG. 6, the first positive electrode active material layer 222a1 is provided in the first region R21. The first region R21 is provided, for example, on the bottom surface 12a side of the case 10 (see FIG. 4). In this embodiment, the first region R21 can be set in a portion along the longitudinal direction LD of the positive electrode 222 on the side opposite the positive electrode tab 222t. The first positive electrode active material layer 222a1 is provided, for example, in a strip shape along the longitudinal direction LD of the positive electrode 222 on the side opposite the positive electrode tab 222t. In the embodiment shown in FIG. 6, the second positive electrode active material layer 222a2 is provided in the second region R22. The second region R22 is provided, for example, on the top surface (here, the sealing plate 14) side of the case 10 (see FIG. 4). In this embodiment, the second region R22 can be set in a portion along the longitudinal direction LD of the positive electrode 222 on the positive electrode tab 222t side. The second positive electrode active material layer 222a2 is provided in a strip shape along the longitudinal direction LD of the positive electrode 222, for example, on the positive electrode tab 222t side.

[0055] The protective layer 222p may be provided, for example, closer to the upper surface (here, the sealing plate 14) than the second region R22. In the embodiment shown in Fig. 6, the protective layer 222p is provided in a strip shape along the longitudinal direction LD on the positive electrode tab 222t side of the positive electrode current collector foil 222c, and is provided on the base end side of the positive electrode tab 222t. The base end of the positive electrode tab 222t here refers to the boundary between the positive electrode tab 222t and the main body of the positive electrode current collector foil 222c.

[0056] In the embodiment shown in FIG. 6, the positive electrode tabs 222t protrude outward (in the U direction in the vertical direction Z in FIG. 6) from one end side of the positive electrode current collector foil 222c in the winding axis direction WD. The positive electrode tabs 222t are provided at predetermined intervals (intermittently) along the longitudinal direction LD. Neither the positive electrode active material layer 222a nor the protective layer 222p is provided on the protruding tip side of the positive electrode tab 222t. In this embodiment, a plurality of positive electrode tabs 222t are stacked in the electrode assembly 220 to form a positive electrode tab group. This positive electrode tab group is connected to the positive electrode current collector 50 (see FIG. 4). The positive electrode tabs 222t may, for example, differ from one another in size or shape.

[0057] As shown in FIG. 6, the negative electrode 224 includes a negative electrode active material layer 224a and a negative electrode current collector foil 224c. The negative electrode current collector foil 224c is, for example, a long sheet-like copper foil. In this embodiment, the negative electrode current collector foil 224c has a long, strip-like main body and a negative electrode tab 224t protruding from the main body. The negative electrode current collector foil 224c has a region where the negative electrode active material layer 224a is provided and a region where the negative electrode active material layer 224a is not provided. The region where the negative electrode active material layer 224a is not provided includes, for example, a region where the negative electrode current collector foil 224c is exposed.

[0058] 6, the negative electrode active material layer 224a is provided in a strip shape on the negative electrode current collector foil 224c along the longitudinal direction LD. Here, the negative electrode active material layer 224a is provided over the entire body of the negative electrode current collector foil 224c along the longitudinal direction LD. The negative electrode active material layer 224a may be provided on, for example, one or both sides (both sides in this case) of the negative electrode current collector foil 224c.

[0059] In the embodiment shown in FIG. 6, the negative electrode tab 224t protrudes outward (in the U direction in the up-down direction Z in FIG. 6) from one end side of the negative electrode current collector foil 224c in the winding axis direction WD. The negative electrode tabs 224t are provided at predetermined intervals (intermittently) along the longitudinal direction LD. No negative electrode active material layer 224a is provided on the protruding tip side of the negative electrode tab 224t. In this embodiment, in the electrode body 220, multiple negative electrode tabs 224t are stacked to form a negative electrode tab group. This negative electrode tab group is connected to the negative electrode current collector 60 (see FIG. 4). The negative electrode tabs 224t may, for example, have different sizes or shapes from one another.

[0060] As described above, this embodiment uses the electrode assembly 220, which is a wound electrode assembly, which makes it possible to achieve, for example, an even higher energy density for the power storage module.

[0061] <Third embodiment> In the first and second embodiments, the energy storage module 1000 includes the positive electrode terminal 30 and the negative electrode terminal 40 on the sealing plate 14, which is the upper surface of the energy storage device 100. However, the technology disclosed herein is not limited to this. FIG. 7 is a schematic side view of the energy storage module 3000. In FIG. 7, some of the components constituting the module case 3C of the energy storage module 3000 are not shown. As shown in FIG. 7, the energy storage module 3000 includes a plurality of energy storage devices 3100, a bus bar 2C, a module case 3C, a cooling unit 4C, and a spacer 5C.

[0062] As shown in Fig. 7, in the power storage module 3000, a plurality of power storage devices 3100 are arranged in a first direction P. In the first direction P, the power storage devices 3100 are arranged so that the first side surfaces 312b of the power storage devices 3100 face each other. As shown in Fig. 7, the power storage devices 3100 are arranged so that of two power storage devices 3100 adjacent to each other in the first direction P, the positive electrode terminal 330 of one power storage device 3100 and the negative electrode terminal 340 of the other power storage device 3100 are adjacent to each other. A spacer 5C is sandwiched between the power storage devices 3100.

[0063] FIG. 8 is a schematic perspective view of an electricity storage device 3100. FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. As shown in FIGS. 8 and 9, the electricity storage device 3100 includes a case 310, an electrode assembly 320, a positive electrode terminal 330, a negative electrode terminal 340, a positive electrode current collector 350, a negative electrode current collector 360, a nonaqueous electrolyte (not shown), and various insulating members (not shown). The case 310 here is a flat, rectangular case. As shown in FIGS. 8 and 9, the case 310 includes a main body 312 and two sealing plates 314. In this embodiment, the main body 312 has a rectangular cylindrical shape and includes a bottom surface 312a, a pair of opposing first side surfaces 312b, an upper surface 312d, and two openings 312h. The bottom surface 312a is, for example, rectangular and forms the lower surface of the case 310. Here, the pair of opposing first side surfaces 312b extend from a pair of opposing long sides of the bottom surface 312a. Here, the top surface 312d faces the bottom surface 312a. In this embodiment, the area surrounded by the bottom surface 312a, the pair of opposing first side surfaces 312b, and the top surface 312d forms the opening 312h. A sealing plate 314 is attached to each of the two openings 312h, thereby forming a pair of opposing second side surfaces 312c. Here, the pair of opposing second side surfaces 312c are areas extending from a pair of opposing short sides of the bottom surface 312a.

[0064] The main body 312 can be produced, for example, by bending a single metal plate into a cylindrical shape and joining (for example, welding) the seams. Therefore, as shown in Fig. 8, the main body 312 has a joint 312w on the top surface 312d thereof that extends along the left-right direction Y.

[0065] The sealing plate 314 is, for example, a member that closes the opening 312h of the case 310. In this embodiment, the sealing plate 314 is flat and has a shape (here, rectangular) that corresponds to the shape of the opening 312h. In the embodiment shown in FIGS. 8 and 9, one of the sealing plates 314 (here, the sealing plate 314 to which the positive electrode terminal 330 is attached) is provided with a liquid inlet 315. In this embodiment, the liquid inlet 315 is provided closer to the bottom surface 312a than the positive electrode terminal 330. The liquid inlet 315 is sealed with, for example, a sealing plug 316. Although not shown, each sealing plate 314 is provided with a terminal lead-out hole.

[0066] Fig. 10 is a partial perspective view of the electrode assembly 320. Fig. 10 shows a portion of the laminated structure of the positive electrode 322, the negative electrode 324, and the separator 326 in the electrode assembly 320. As shown in Fig. 10, the electrode assembly 320 is a laminated electrode assembly including a sheet-like positive electrode 322, a sheet-like negative electrode 324, and a sheet-like separator 326 interposed between the positive electrode 322 and the negative electrode 324.

[0067] 10, the positive electrode 322 includes a positive electrode active material layer 322a and a positive electrode current collector foil 322c. In this embodiment, the positive electrode active material layer 322a includes a first positive electrode active material layer 322a1 and a second positive electrode active material layer 322a2.

[0068] The first positive electrode active material layer 322a1 is provided, for example, in a first region R31 on the bottom surface 312a side (see FIGS. 9 and 10). In this embodiment, the first region R31 is preferably set closer to the bottom surface 312a than either the positive electrode tab 322t or the negative electrode tab 324t, whichever is closer to the bottom surface 312a. For this reason, the locations where the electrode tabs are provided, the area of ​​the first region R31, and the like can be set appropriately from the viewpoint of better achieving the effects of the technology disclosed herein.

[0069] The second positive electrode active material layer 322a2 is provided, for example, in the second region R32 on the upper surface 312d side (see FIGS. 9 and 10). In this embodiment, the second region R32 is preferably provided such that its lower end R32e is closer to the bottom surface 312a than the lower ends t1, t2 of the positive electrode tab 322t and the negative electrode tab 324t, whichever is closer to the bottom surface 312a (see FIGS. 9 and 10).

[0070] 10, the positive electrode tab 322t protrudes from one of a pair of opposing short sides of the positive electrode current collector foil 322c. As shown in FIGS. 9 and 10, in the electrode assembly 320, the positive electrode tabs 322t of the positive electrodes 322 are stacked to form a positive electrode tab group 323.

[0071] As shown in Fig. 10, the negative electrode 324 includes a negative electrode active material layer 324a and a negative electrode current collector foil 324c. In the embodiment shown in Fig. 10, the negative electrode tab 324t protrudes from one of a pair of opposing short sides of the negative electrode current collector foil 324c. As shown in Figs. 9 and 10, in the electrode assembly 320, the negative electrode tabs 324t of each negative electrode 324 are stacked to form a negative electrode tab group 325.

[0072] In this embodiment, the positive electrode terminal 330 is provided on one of a pair of opposing second side surfaces 312c (here, a pair of opposing sealing plates 314). As shown in FIG. 9, the positive electrode terminal 330 is inserted into a terminal lead-out hole (not shown) provided in the sealing plate 314, and a portion of the positive electrode terminal 330 is disposed inside the case 310 and a portion of the positive electrode terminal 330 is disposed outside the case 310. The portion of the positive electrode terminal 330 disposed inside the case 310 is connected to the positive electrode current collector 350. The portion of the positive electrode terminal 330 disposed outside the case 310 is connected to the bus bar 2C (see FIG. 7).

[0073] In this embodiment, the negative electrode terminal 340 is provided on the other of the pair of opposing second side surfaces 312c (here, the pair of opposing sealing plates 314). As shown in FIG. 9, the negative electrode terminal 340 is inserted into a terminal lead-out hole (not shown) provided in the sealing plate 314, and a portion of the negative electrode terminal 340 is disposed inside the case 310 and a portion of the negative electrode terminal 340 is disposed outside the case 310. The portion of the negative electrode terminal 340 disposed inside the case 310 is connected to the negative electrode current collector 360. The portion of the negative electrode terminal 340 disposed outside the case 310 is connected to the bus bar 2C (see FIG. 7).

[0074] 9, the positive electrode current collector 350 is flat and disposed along the inner surface of one of a pair of opposing second side surfaces 312c (here, a pair of opposing sealing plates 314). In this case, the positive electrode current collector 350 is connected (welded) to the positive electrode tab group 323, and also to the tip of the positive electrode terminal 330.

[0075] 9, the negative electrode current collector 360 has a flat plate shape and is disposed along the inner surface of the other of the pair of opposing second side surfaces 312c (here, the pair of opposing sealing plates 314). Here, the negative electrode current collector 360 has the negative electrode tab group 325 connected (welded) to it, and also has the tip of the negative electrode terminal 340 connected to it.

[0076] Although not shown in the drawings, the power storage device 3100 may have an insulating member similar to that described in the first embodiment.

[0077] As described above, the case 310 may have a rectangular bottom surface 312a, a pair of first side surfaces 312b extending from a pair of opposing long sides of the bottom surface 312a, and a pair of second side surfaces 312c (here, a pair of opposing sealing plates 314) extending from a pair of opposing short sides of the bottom surface 312a. The case 310 may have a positive electrode terminal 330 and a negative electrode terminal 340 on the second side surfaces 312c (here, a pair of opposing sealing plates 314). The multiple power storage devices 3100 may be arranged such that the first side surfaces 312b of the power storage devices 3100 face each other. The bus bar 2C may span between the positive electrode terminal 330 of one power storage device 3100 and the negative electrode terminal 340 of the other power storage device 3100 of two power storage devices 3100 adjacent to each other in the arrangement direction of the multiple power storage devices 3100. With this configuration, the effects of the technology disclosed herein can be appropriately achieved.

[0078] The positive electrode 324 may have a first region R31 closer to the bottom surface 312a than the connection portion between the positive electrode terminal 330 and the bus bar 2C or the connection portion between the negative electrode terminal 340 and the bus bar 2C, which is located closer to the bottom surface 312a. This can further improve the safety of the energy storage module 3000 when used.

[0079] <Fourth embodiment> In the third embodiment described above, the energy storage module 3000 includes the electrode assembly 320, which is a laminated electrode assembly. However, the technology disclosed herein is not limited to this. For example, the energy storage module 3000 may include an electrode assembly 420 shown in FIG. 11 instead of the electrode assembly 320. FIG. 11 is a schematic diagram of the electrode assembly 420. As shown in FIG. 11, the electrode assembly 420 is a wound electrode assembly in which a long sheet-like positive electrode 422 and a long sheet-like negative electrode 424 are wound around a winding axis WL with a long sheet-like separator 426 interposed therebetween.

[0080] FIG. 12 is a plan view of the positive electrode 422. As shown in FIGS. 11 and 12, the positive electrode 422 includes a positive electrode active material layer 422a and a positive electrode current collector foil 422c. The positive electrode current collector foil 422c is, for example, a long sheet-like aluminum foil. In this embodiment, the positive electrode current collector foil 422c has a long, strip-shaped main body and a positive electrode tab 422t protruding from the main body. The positive electrode current collector foil 422c has a region where the positive electrode active material layer 422a is provided and a region where the positive electrode active material layer 422a is not provided. The region where the positive electrode active material layer 422a is not provided includes, for example, a region where the positive electrode current collector foil 422c is exposed.

[0081] 11 and 12, the positive electrode active material layer 422a is provided in a strip shape on the positive electrode current collector foil 422c along the longitudinal direction LD. Here, the positive electrode active material layer 422a is not provided on the positive electrode tab 422t. The positive electrode active material layer 422a may be provided on, for example, one or both sides (here, both sides) of the positive electrode current collector foil 422c. In this embodiment, the positive electrode active material layer 422a has a first positive electrode active material layer 422a1 and a second positive electrode active material layer 422a2.

[0082] In this embodiment, the first positive electrode active material layer 422a1 is provided in a first region R41 on the bottom surface 312a side of the electrode body 420 (see FIGS. 9, 11, and 12). The first region R41 is preferably set closer to the bottom surface 312a than either the positive electrode tab 422t or the negative electrode tab 424t, whichever is provided closer to the bottom surface 312a (see FIGS. 9 and 11).

[0083] The second positive electrode active material layer 422a2 is provided, for example, in the second region R42 on the upper surface 312d side (see FIGS. 9 and 11). In this embodiment, the second region 432 is preferably provided such that its lower end is closer to the bottom surface 312a than the lower ends t41, t42 of the positive electrode tab 422t and the negative electrode tab 424t, whichever is closer to the bottom surface 312a (see FIGS. 9 and 11).

[0084] 12 , in the positive electrode 422, first positive electrode active material layers 422a1 and second positive electrode active material layers 422a2 are alternately provided from a first end 4221 to a second end 4222 in the longitudinal direction LD. The first end 4221 may be, for example, the end where winding begins and may be located inside the electrode body 420. The second end 4222 may be, for example, the end where winding ends and may be located on the outer periphery of the electrode body 420.

[0085] As shown in FIGS. 11 and 12, the positive electrode tab 422t protrudes outward (in the R direction in the left-right direction Y in FIG. 11) from one end edge of the positive electrode current collector foil 422c along the longitudinal direction LD. As shown in FIG. 12, the positive electrode tab 422t may protrude outward from the end edge in a region where the second positive electrode active material layer 422a2 is provided. The positive electrode tabs 422t are provided at predetermined intervals (intermittently) along the longitudinal direction LD. No positive electrode active material layer 422a is provided on the protruding tip side of the positive electrode tab 422t. In this embodiment, a plurality of positive electrode tabs 422t are stacked in the electrode body 420 to form a positive electrode tab group.

[0086] As shown in FIG. 11 , the negative electrode 424 includes a negative electrode active material layer 424a and a negative electrode current collector foil 424c. The negative electrode current collector foil 424c is, for example, a long sheet-like copper foil. In this embodiment, the negative electrode current collector foil 424c has a long, strip-like main body and a negative electrode tab 424t protruding from the main body. The negative electrode current collector foil 424c has a region where the negative electrode active material layer 424a is provided and a region where the negative electrode active material layer 424a is not provided. The region where the negative electrode active material layer 424a is not provided includes, for example, a region where the negative electrode current collector foil 424c is exposed.

[0087] 11, the negative electrode active material layer 424a is provided in a strip shape on the negative electrode current collector foil 424c along the longitudinal direction LD. Here, the negative electrode active material layer 424a is not provided on the negative electrode tab 424t. The negative electrode active material layer 424a may be provided on, for example, one or both sides (both sides in this case) of the negative electrode current collector foil 424c.

[0088] As shown in FIG. 11, the negative electrode tab 424t protrudes outward (in the L direction in the left-right direction Y in FIG. 11) from one end of the negative electrode current collector foil 424c along the longitudinal direction LD. The negative electrode tabs 424t are provided at predetermined intervals (intermittently) along the longitudinal direction LD. No negative electrode active material layer 424a is provided on the protruding tip side of the negative electrode tab 424t. In this embodiment, a plurality of negative electrode tabs 424t are stacked in the electrode body 420 to form a negative electrode tab group.

[0089] <Other embodiments> In the first embodiment described above, the cooling unit 4A is provided on the bottom plate 33A of the module case 3A. However, the technology disclosed herein is not limited to this configuration. The cooling unit 4A may be provided on, for example, the side plate 32A. In this case, the cooling unit 4A may be provided in, for example, a region of the side plate 32A that faces the first region R1. Furthermore, the case in the above embodiment has a rectangular shape. However, the technology disclosed herein is not limited to this configuration. The case may be, for example, cylindrical.

[0090] Suitable applications of the energy storage modules and energy storage devices in all of the above-described embodiments include drive power sources mounted on vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs).

[0091] The technology disclosed herein may include aspects described in the following items. Section 1: A power storage module, a plurality of electricity storage devices each including an electrode assembly including a positive electrode and a negative electrode, and a case for housing the electrode assembly, the case having a bottom surface, an upper surface facing the bottom surface, and a side surface provided between the bottom surface and the upper surface; a bus bar connecting each of the energy storage devices to each other; and a cooling unit provided on the bottom side of the electricity storage device; It is equipped with the positive electrode has a first region on the bottom surface side and a second region on the top surface side, the first region includes a first positive electrode active material that is a positive electrode active material having a relatively large amount of Ni, The second region includes a second positive electrode active material that is a positive electrode active material having a relatively small amount of Ni. Section 2: The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, The upper surface has a positive electrode terminal and a negative electrode terminal, the plurality of power storage devices are arranged such that the first side surfaces of the power storage devices face each other; Item 2. The energy storage module according to item 1, wherein the bus bar is bridged between the positive terminal of one of two energy storage devices adjacent to each other in a direction in which the plurality of energy storage devices are arranged and the negative terminal of the other energy storage device. Section 3: The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, The second side surface has a positive terminal and a negative terminal, the plurality of power storage devices are arranged such that the first side surfaces of the power storage devices face each other; Item 2. The energy storage module according to item 1, wherein the bus bar is bridged between the positive terminal of one of two energy storage devices adjacent to each other in a direction in which the plurality of energy storage devices are arranged and the negative terminal of the other energy storage device. Section 4: Item 4. The energy storage module according to item 3, wherein the positive electrode has the first region closer to the bottom surface than a connection portion between the positive electrode terminal and the bus bar and a connection portion between the negative electrode terminal and the bus bar, which connection portion is located closer to the bottom surface. Section 5: 5. The energy storage module according to any one of items 1 to 4, comprising, as the electrode body, a laminated electrode body including the positive electrode in a sheet shape, the negative electrode in a sheet shape, and a sheet-shaped separator interposed between the positive electrode and the negative electrode. Item 6: 5. The energy storage module according to any one of items 1 to 4, wherein the electrode body comprises a wound electrode body in which the positive electrode and the negative electrode are long and sheet-shaped and wound around a winding axis with a long and sheet-shaped separator interposed therebetween. Section 7: The first positive electrode active material is represented by the following general formula (1): Li 1+a1 Ni x1 Mn y1 M1 z1 O2(1) [In the formula, M1 is one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a1≦0.1, 0.7≦x1≦1.0, 0≦y1≦0.3, 0≦z1≦0.3, and x1+y1+z1=1.] is a compound represented by The second positive electrode active material is represented by the following general formula (2): Li 1+a2 Ni x2 Mn y2 M2 z2 O2(2) [In the formula, M2 is one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a2≦0.1, 0.3≦x2<0.7, 0≦y2≦0.7, 0≦z2≦0.7, and x2+y2+z2=1.] Item 7. The electricity storage module according to any one of items 1 to 6, wherein the compound is represented by the formula: Section 8: an electrode assembly including a positive electrode and a negative electrode; a case for accommodating the electrode body, the case having a bottom surface, an upper surface opposite to the bottom surface, and a side surface provided between the bottom surface and the upper surface; An electricity storage device comprising: the positive electrode has a first region on the bottom surface side and a second region on the top surface side, the first region includes a first positive electrode active material that is a positive electrode active material having a relatively high Ni content; The second region includes a second positive electrode active material that is a positive electrode active material having a relatively small amount of Ni. Section 9: The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, Item 9. The electricity storage device according to item 8, having a positive electrode terminal and a negative electrode terminal on the upper surface. Section 10: The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, Item 9. The electricity storage device according to item 8, having a positive electrode terminal and a negative electrode terminal on the second side surface. Section 11: Item 11. The power storage device according to item 10, wherein the positive electrode has the first region on the bottom side of a portion of the positive electrode terminal and a portion of the negative electrode terminal that is closer to the bottom side. Section 12: Item 12. The power storage device according to any one of items 8 to 11, comprising, as the electrode body, a laminated electrode body including the positive electrode in a sheet shape, the negative electrode in a sheet shape, and a sheet-shaped separator interposed between the positive electrode and the negative electrode. Section 13: Item 12. The power storage device according to any one of items 8 to 11, wherein the electrode body comprises a wound electrode body in which the long sheet-shaped positive electrode and the long sheet-shaped negative electrode are wound around a winding axis with a long sheet-shaped separator interposed therebetween. Section 14: The first positive electrode active material is represented by the following general formula (1): Li 1+a1 Ni x1 Mn y1 M1 z1 O2(1) [In the formula, M1 is one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a1≦0.1, 0.7≦x1≦1.0, 0≦y1≦0.3, 0≦z1≦0.3, and x1+y1+z1=1.] is a compound represented by The second positive electrode active material is represented by the following general formula (2): Li 1+a2 Ni x2 Mn y2 M2 z2 O2(2) [In the formula, M2 is one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a2≦0.1, 0.3≦x2<0.7, 0≦y2≦0.7, 0≦z2≦0.7, and x2+y2+z2=1.] Item 14. The electricity storage device according to any one of items 8 to 13, wherein the compound is represented by the formula: [Explanation of symbols]

[0092] 1000 Energy Storage Module 100 Energy storage device 10 cases 12 Main Unit 20, 220, 320, 420 electrode body 22, 222, 322, 422 positive electrode 22a, 222a, 322a, 422a Cathode active material layer 22a1, 222a1, 322a1, 422a1 First Positive Active Material Layer 22a2, 222a2, 322a2, 422a2 Second Positive Active Material Layer R1, R21, R31, R41 Domain 1 R2, R22, R32, R42 Second Domain 22C, 222C, 322C, 422C positive electrode current collector foil 24, 224, 324, 424 negative electrode 2A, 2C バスバー 4A, 4C Cooling Sections

Claims

1. A power storage module, a plurality of electricity storage devices each including an electrode assembly including a positive electrode and a negative electrode, and a case for accommodating the electrode assembly, the case having a bottom surface, an upper surface facing the bottom surface, and a side surface provided between the bottom surface and the upper surface; a bus bar connecting each of the power storage devices to each other; and a cooling unit provided on the bottom side of the electricity storage device; It is equipped with the positive electrode has a first region on the bottom surface side and a second region on the top surface side, the first region includes a first positive electrode active material that is a positive electrode active material having a relatively large amount of Ni, The second region includes a second positive electrode active material that is a positive electrode active material having a relatively small amount of Ni.

2. The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, The upper surface has a positive electrode terminal and a negative electrode terminal, the plurality of power storage devices are arranged such that the first side surfaces of the power storage devices face each other; 2. The energy storage module according to claim 1, wherein the bus bar is bridged between the positive electrode terminal of one of two energy storage devices adjacent to each other in a direction in which the plurality of energy storage devices are arranged and the negative electrode terminal of the other energy storage device.

3. The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, The second side surface has a positive terminal and a negative terminal, the plurality of power storage devices are arranged such that the first side surfaces of the power storage devices face each other; 2. The energy storage module according to claim 1, wherein the bus bar is bridged between the positive electrode terminal of one of two energy storage devices adjacent to each other in a direction in which the plurality of energy storage devices are arranged and the negative electrode terminal of the other energy storage device.

4. 4. The energy storage module according to claim 3, wherein the positive electrode has the first region closer to the bottom surface than a connection portion between the positive electrode terminal and the bus bar and a connection portion between the negative electrode terminal and the bus bar, the connection portion being disposed closer to the bottom surface.

5. 5. The storage module according to claim 1, comprising, as the electrode body, a laminated electrode body including: a sheet-shaped positive electrode; a sheet-shaped negative electrode; and a sheet-shaped separator interposed between the positive electrode and the negative electrode.

6. 5. The storage module according to claim 1, wherein the electrode body comprises a wound electrode body in which the long sheet-shaped positive electrode and the long sheet-shaped negative electrode are wound around a winding axis with a long sheet-shaped separator interposed therebetween.

7. The first positive electrode active material is represented by the following general formula (1): Li １＋ａ１ Ni ｘ１ Mn ｙ１ M1 ｚ１ O ２ (1) [In the formula, M1 is one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a1≦0.1, 0.7≦x1≦1.0, 0≦y1≦0.3, 0≦z1≦0.3, and x1+y1+z1=1.] is a compound represented by The second positive electrode active material is represented by the following general formula (2): Li １＋ａ２ Ni ｘ２ Mn ｙ２ M2 ｚ２ O ２ (2) [In the formula, M2 represents one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a2≦0.1, 0.3≦x2<0.7, 0≦y2≦0.7, 0≦z2≦0.7, and x2+y2+z2=1.] The storage module according to any one of claims 1 to 4, wherein the compound is represented by the formula:

8. an electrode assembly including a positive electrode and a negative electrode; a case for accommodating the electrode body, the case having a bottom surface, an upper surface opposite to the bottom surface, and a side surface provided between the bottom surface and the upper surface; An electricity storage device comprising: the positive electrode has a first region on the bottom surface side and a second region on the top surface side, the first region includes a first positive electrode active material that is a positive electrode active material having a relatively high Ni content; The second region includes a second positive electrode active material that is a positive electrode active material having a relatively small amount of Ni.

9. The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, The electricity storage device according to claim 8 , further comprising a positive electrode terminal and a negative electrode terminal on the upper surface.

10. The case is The container has a rectangular bottom surface, a pair of first side surfaces extending from a pair of opposing long sides of the bottom surface, and a pair of second side surfaces extending from a pair of opposing short sides of the bottom surface, The electricity storage device according to claim 8 , further comprising a positive electrode terminal and a negative electrode terminal on the second side surface.

11. 11. The power storage device according to claim 10, wherein the positive electrode has the first region on a bottom side of a portion of the positive electrode terminal and a portion of the negative electrode terminal that is disposed closer to the bottom side.

12. The electrode body is a laminated electrode body including the sheet-shaped positive electrode, the sheet-shaped negative electrode, and a sheet-shaped separator interposed between the positive electrode and the negative electrode. The power storage device according to any one of claims 8 to 11.

13. The electrode body includes a wound electrode body in which the long sheet-shaped positive electrode and the long sheet-shaped negative electrode are wound around a winding axis with a long sheet-shaped separator interposed therebetween. The power storage device according to any one of claims 8 to 11.

14. The first positive electrode active material is represented by the following general formula (1): Li １＋ａ１ Ni ｘ１ Mn ｙ１ M1 ｚ１ O ２ (1) [In the formula, M1 is one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a1≦0.1, 0.7≦x1≦1.0, 0≦y1≦0.3, 0≦z1≦0.3, and x1+y1+z1=1.] is a compound represented by The second positive electrode active material is represented by the following general formula (2): Li １＋ａ２ Ni ｘ２ Mn ｙ２ M2 ｚ２ O ２ (2) [In the formula, M2 represents one or more metal elements selected from the group consisting of Co, Al, Mg, Ca, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, Ta, and W, and the following relationships are satisfied: -0.1≦a2≦0.1, 0.3≦x2<0.7, 0≦y2≦0.7, 0≦z2≦0.7, and x2+y2+z2=1.] The electricity storage device according to any one of claims 8 to 11, wherein the compound is represented by the formula:

Images