Energy storage device and energy storage module

Abstract

To provide a power storage module that can effectively regulate (cool or heat) the temperature of a power storage device.SOLUTION: A power storage module 500 includes a plurality of power storage devices 100 and a temperature adjustment unit 400. The power storage device 100 includes an electrode assembly 20 including a positive electrode 22 and a negative electrode 24, an electrolyte, and a case 10 that accommodates the electrode assembly 20 and the electrolyte. The case 10 includes a first wall having an outer surface on which a recess 12d is provided. The temperature adjustment unit 400 is disposed so as to face the outer surface of the first wall. A stacking end surface 20a of the electrode assembly 20 is disposed so as to face the inner surface of the first wall.SELECTED DRAWING: Figure 6D

Description

[Technical field]

[0001] The present invention relates to an electricity storage device and an electricity storage module. [Background technology]

[0002] JP 2021-089812 A discloses a battery module including a secondary battery, a cooler, and a heat conductive member disposed between the secondary battery and the cooler. A groove recessed toward the inside of the case is formed in the wall of the case of the secondary battery facing the cooler. The heat conductive member fills the space between the facing wall, including the inside of the groove, and the cooler. This configuration is said to be able to achieve both suppression of deformation of the case and suppression of deterioration of cooling performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-089812 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in a power storage module (e.g., a battery pack) including a plurality of power storage devices (e.g., secondary batteries), the individual power storage devices may become hot when a large current is continuously charged or discharged, when some abnormality (internal short circuit, etc.) occurs, etc. Also, the higher the capacity of the power storage device, the smaller the cooling effect of natural heat dissipation or a temperature adjustment mechanism becomes.

[0005] Therefore, a main object of the present disclosure is to provide an electricity storage module capable of effectively regulating (cooling or heating) the temperature of an electricity storage device. [Means for solving the problem]

[0006] The disclosed power storage module includes a plurality of power storage devices and a temperature adjustment unit. The power storage devices include an electrode assembly including a positive electrode and a negative electrode, an electrolyte, and a case that contains the electrode assembly and the electrolyte. The case includes a first wall having an outer surface with a recess, and the temperature adjustment unit is disposed so as to face the outer surface of the first wall, and the stacking end surface of the electrode assembly is disposed so as to face the inner surface of the first wall.

[0007] According to this configuration, by providing a recess on the outer surface of the first wall of the electricity storage device, the surface area of ​​the outer surface of the first wall is increased, and the heat exchange efficiency with the temperature adjustment unit arranged opposite the outer surface is improved. This makes it possible to effectively adjust the temperature (cooling or heating) of the electricity storage device. In addition, by arranging the stacking end surface of the electrode body in a direction facing the inner surface of the first wall, the electrode body becomes more susceptible to the effect of cooling or heating from the temperature adjustment unit, and the temperature of the electrode body can be effectively adjusted. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an exploded perspective view illustrating a power storage module according to an embodiment. [Diagram 2] 1 is a vertical cross-sectional view illustrating a schematic configuration of an electricity storage device according to an embodiment. [Diagram 3] 1 is a cross-sectional view illustrating a schematic configuration of an electricity storage device according to an embodiment. [Figure 4] FIG. 4 is a schematic vertical cross-sectional view taken along line IV-IV in FIG. 2. [Diagram 5] FIG. 2 is a schematic diagram showing the configuration of an electrode body according to one embodiment. [Figure 6A] 5 is a plan view showing a schematic arrangement pattern of recesses in a bottom wall of a case of an electricity storage device according to one embodiment. FIG. [Figure 6B] 5 is a plan view illustrating a schematic shape of a recess in a bottom wall of a case of an electricity storage device according to one embodiment. FIG. [Figure 6C] 5 is a cross-sectional view illustrating a schematic shape of a recess in a bottom wall of a case of an electricity storage device according to one embodiment. FIG. [Figure 6D] 4 is a schematic diagram showing an arrangement of a bottom wall of a case of an electricity storage device according to an embodiment and a temperature adjustment unit. FIG. [Figure 7A] 13 is a plan view showing a schematic arrangement pattern of recesses in a bottom wall of a case of an electricity accumulation device in Modification 1. FIG. [Figure 7B] 13 is a plan view illustrating a schematic shape of a recess in a bottom wall of a case of an electricity accumulation device in Modification 1. FIG. [Figure 7C] 13 is a cross-sectional view illustrating a schematic shape of a recess in a bottom wall of a case of an electricity accumulation device in Modification 1. FIG. [Figure 8A] 13 is a plan view showing a schematic arrangement pattern of recesses in a bottom wall of a case of an electricity accumulation device in Modification 2. FIG. [Figure 8B] 13 is a plan view illustrating a schematic shape of a recess in a bottom wall of a case of an electricity accumulation device in Modification 2. FIG. [Figure 8C] 13 is a cross-sectional view illustrating a schematic shape of a recess in a bottom wall of a case of an electricity accumulation device in Modification 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, some preferred embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of an electricity storage device that does not characterize the technology disclosed herein) can be understood as design matters of a person skilled in the art based on the conventional technology in the field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the field. It should be noted that the expression "A to B (where A and B are any numerical values)" indicating a range in this specification means "A or more and B or less", and also includes the meanings of "more than A and less than B", "more than A and B or less", and "A or more and less than B".

[0010] In this specification, the term "electricity storage device" refers to a device that can be charged and discharged. Electricity storage devices include batteries such as primary batteries and secondary batteries (e.g., lithium ion secondary batteries and nickel-metal hydride batteries), and capacitors (physical batteries) such as electric double layer capacitors.

[0011] FIG. 1 is an exploded perspective view showing a typical example of an energy storage module 500 according to an embodiment. FIG. 2 is a vertical cross-sectional view showing a typical example of the configuration of an energy storage device 100. The electrode assembly 20 in FIG. 2 is partially broken for the purpose of illustration. FIG. 3 is a horizontal cross-sectional view showing a typical example of the configuration of the energy storage device 100. FIG. 4 is a schematic vertical cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a schematic view showing a typical example of the configuration of the electrode assembly 20. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom. In addition, the symbol X in the drawings indicates the short side direction (thickness direction) of the energy storage device 100, the symbol Y indicates the long side direction of the energy storage device 100 perpendicular to the short side direction, and the symbol Z indicates the up-down direction of the energy storage device 100. The short side direction X is also the arrangement direction of the energy storage devices 100. However, these are merely directions for the convenience of explanation, and do not limit the installation form of the power storage device 100 and the power storage module 500 in any way.

[0012] Here, the power storage module 500 includes a plurality of power storage devices 100, a plurality of spacers 200, a restraining mechanism 300, and a temperature adjustment unit 400. The power storage module 500 includes a plurality of power storage devices 100 arranged along a predetermined direction. Specifically, the power storage devices 100 are arranged so that the surfaces of adjacent power storage devices 100 in the thickness direction X face each other. That is, here, the plurality of power storage devices 100 are arranged (stacked) along the thickness direction X. Although not shown in the figure, the plurality of power storage devices 100 may be electrically connected by a conductive member such as a bus bar. The bus bar is electrically connected to the positive terminal member or the negative terminal member of each power storage device. In this case, the bus bar may connect the plurality of power storage devices 100 in series, parallel, or multiple series and multiple parallel.

[0013] In the power storage module 500, a spacer 200 is disposed between adjacent power storage devices 100. The spacer 200 can contribute to uniformity of the binding pressure on the opposing surfaces of the adjacent power storage devices 100. The spacer 200 can be made of, for example, a resin material. Examples of the resin material include natural rubber, synthetic rubber, silicone resin, and urethane resin. Note that the spacer 200 is not an essential component.

[0014] The restraining mechanism 300 is configured to apply a prescribed restraining pressure to the multiple power storage devices 100 and the multiple spacers 200 in the arrangement direction X. Here, the restraining mechanism 300 includes a pair of end plates 310, a pair of side plates 320, and multiple screws 330. The pair of end plates 310 are aligned in a predetermined arrangement direction X. The pair of end plates 310 are disposed at both ends of the power storage module 500 in the arrangement direction X. The power storage device 100 is disposed between the pair of end plates 310 along the arrangement direction X. The pair of end plates 310 sandwich the multiple power storage devices 100 and the multiple spacers 200 in the arrangement direction X.

[0015] 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 restraining load is, for example, approximately 10 to 15 kN. As a result, a restraining load is applied to the plurality of power storage devices 100 and the plurality of spacers 200 from the arrangement direction X, and the power storage module 500 is held integrally. However, the restraining mechanism is not limited to this. The restraining mechanism 300 may include, for example, a plurality of restraining bands, bind bars, or the like, instead of the side plates 320. Note that the restraining mechanism 300 is not an essential component.

[0016] 2, the electricity storage device 100 includes a case 10, an electrode assembly 20, and an electrolyte (not shown). Here, the electricity storage device 100 may include a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collecting member 50, an external positive electrode current collecting member 52, a negative electrode current collecting member 60, an external negative electrode current collecting member 62, a gasket 92, and an internal insulating member 94. Here, the electricity storage device 100 is a lithium ion secondary battery.

[0017] The case 10 is a housing that contains the electrode body 20 and the electrolyte. The case 10 may be a box-shaped shape with a bottom including a first wall. The first wall is a wall that faces the temperature adjustment unit 400 in the power storage module 500. The case 10 preferably has a flat, bottomed rectangular parallelepiped (rectangular) outer shape. However, the case 10 is not limited thereto and may be cylindrical, rectangular prism, or the like. The material of the case 10 may be the same as that conventionally used, and is not particularly limited. The case 10 is preferably made of metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0018] 2, the case 10 includes an exterior body 12 having an opening 12h, and a sealing plate (lid) 14 that seals the opening 12h. The case 10 preferably includes the exterior body 12 and the sealing plate 14. The exterior body 12 and the sealing plate 14 have sizes according to the size of the electrode assembly 20, the number of electrodes to be accommodated (one or more; here, more than one), etc.

[0019] The exterior body 12 is a bottomed, rectangular container having an opening 12h on the upper surface. The exterior body 12 includes a substantially rectangular bottom wall 12a, a pair of first side walls 12b (see FIG. 3) extending from the long side of the bottom wall 12a and facing each other, and a pair of second side walls 12c (see FIGS. 2 and 3) extending from the short side of the bottom wall 12a and facing each other. The bottom wall 12a faces the opening 12h (see FIG. 2). Here, the first side wall 12b has a larger area than the second side wall 12c. In this embodiment, the bottom wall 12a is the above-mentioned first wall. Therefore, in this embodiment, the present technology can be understood by reading "bottom wall 12a" as "first wall". In the energy storage module 500, the energy storage device 100 is arranged so that the bottom wall 12a faces the temperature adjustment unit. However, the first wall is not limited to the bottom wall 12a, and may be the first side wall 12b, the second side wall 12c, or the sealing plate .

[0020] The sealing plate 14 is a plate-like member attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The sealing plate 14 has a substantially rectangular shape. The case 10 is integrated by joining (e.g., welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. This makes the case 10 airtightly sealed (hermetically sealed).

[0021] As shown in FIG. 2, the sealing plate 14 is provided with a liquid inlet 15, a gas exhaust valve 17, and terminal outlet holes 18 and 19. The liquid inlet 15 is a through hole for injecting an electrolyte into the case 10 after the sealing plate 14 is assembled to the exterior body 12. The liquid inlet 15 is sealed by a sealing member 16 after the electrolyte is injected. The gas exhaust valve 17 is a thin-walled portion configured to break when the pressure inside the case 10 reaches or exceeds a predetermined value, thereby discharging the gas inside the case 10 to the outside. The terminal outlet holes 18 and 19 are formed at both ends of the sealing plate 14 in the long side direction Y. The terminal outlet holes 18 and 19 are through holes that penetrate the sealing plate 14 in the up-down direction Z (thickness direction of the sealing plate 14).

[0022] As shown in FIG. 2, a plurality of recesses 12d are provided on the outer side surface 12a1 of the bottom wall 12a. The recesses 12d are recessed from the outer side surface 12a1 of the bottom wall 12a toward the inner side surface 12a2 of the bottom wall 12a. In this embodiment, the recesses 12d have a bottom surface 12e. This increases the surface area of ​​the outer side surface 12a1 of the bottom wall 12a, improving the heat exchange efficiency with the temperature adjustment unit 400. Therefore, the temperature adjustment (cooling or heating) of the electricity storage device 100 can be performed effectively. Note that there may be only one recess 12d. The recess 12d is provided by, for example, press molding. Note that the recesses 12d in each figure are shown diagrammatically, and the shape, number, arrangement, etc. do not necessarily correspond between the figures.

[0023] The number of recesses 12d is 1 / cm with respect to a planar area including the opening area of ​​the recesses 12d on the outer surface 12a1 of the bottom wall 12a on which the recesses 12d are provided (i.e., the area of ​​the outer surface 12a1 of the bottom wall 12a when the recesses 12d are not provided). 2 It is preferable that the number of pieces is 1.5 pieces / cm or more. 2 More than 2 pieces / cm 2 This increases the surface area of ​​the outer side surface 12a1 of the bottom wall 12a, allowing the power storage device 100 to be cooled or heated more effectively.

[0024] In this embodiment, the inner surface 12a2 of the bottom wall 12a is provided with a protrusion 12f corresponding to the recess 12d. The protrusion 12f protrudes from the inner surface 12a2 of the bottom wall 12a toward the electrode body 20. The protrusion 12f contacts the electrode body 20 via a resin sheet 29, which is an insulating member. The protrusion 12f may directly contact the electrode body 20. Here, the tip surface 12g of the protrusion 12f contacts the electrode body 20. The tip surface 12g of the protrusion 12f faces the bottom surface 12e of the recess 12d. The contact of the protrusion 12f with the electrode body 20 makes it easier for the cooling or heating by the temperature adjustment unit 400 to be transmitted to the electrode body 20. The protrusion 12f is not an essential component. The protrusion 12f may not have the tip surface 12g.

[0025] Fig. 6A is a plan view showing a typical arrangement pattern of the recesses 12d of the bottom wall 12a, as viewed from the outer surface 12a1 side of the bottom wall 12a. Fig. 6B is a plan view showing a typical shape of the recesses 12d, as viewed from the outer surface 12a1 side of the bottom wall 12a. Fig. 6C is a cross-sectional view showing a typical shape of the recesses 12d. Fig. 6D is a schematic diagram showing the arrangement of the bottom wall 12a and the temperature adjustment unit 400.

[0026] As shown in FIG. 6A, in this embodiment, the bottom wall 12a has a row A in which a plurality of recesses 12d are arranged in the long side direction Y of the bottom wall 12a. The number of recesses 12d arranged in one row is not particularly limited, and may be, for example, 2 to 50, and preferably 10 to 40. In the row A, the plurality of recesses 12d are preferably arranged at a distance from each other. In addition, the interval between adjacent recesses 12d is preferably constant. As a result, the recesses 12d are uniformly arranged in the row A, and the temperature of the electricity storage device 100 can be more uniformly adjusted. Note that, since unavoidable deviations may occur when the recesses 12d are formed, the intervals between adjacent recesses 12d do not need to be strictly constant, and for example, a deviation of up to 5% from the average value of the intervals between adjacent recesses 12d in the row A may be allowed.

[0027] As shown in FIG. 6A, the bottom wall 12a has a plurality of rows A in the short side direction X. Here, three rows A are formed, but the number is not particularly limited. For example, the number of rows A may be one. There may be two or more rows (for example, 2 to 10 rows), but it is preferable that there are a plurality of rows A. This provides many recesses 12d in the bottom wall 12a and increases the surface area of ​​the outer side surface 12a1 of the bottom wall 12a, so that the electricity storage device 100 can be cooled or heated more effectively. The number of recesses 12d in each row may be different or the same.

[0028] It is preferable that the interval between adjacent rows A is constant. This allows the recesses 12d to be more uniformly arranged in the short side direction X, and therefore the power storage device 100 can be more uniformly cooled or heated. As described above, since unavoidable misalignment may occur when forming the recesses 12d, for example, a misalignment of up to 5% with respect to the average value of the interval between adjacent rows A may be tolerated.

[0029] Although the shape of the recess 12d is not particularly limited, in this embodiment, a truncated cone-shaped recess 12d is provided as shown in Figures 6A to 6D. The recess 12d gradually narrows from the outer surface 12a1 of the bottom wall 12a toward the bottom surface 12e of the recess 12d. The recess 12d has a side surface 12i between the outer surface 12a1 of the bottom wall 12a and the bottom surface 12e of the recess 12d.

[0030] 6B and 6C, the opening of the recess 12d is circular in plan view with a radius R. The radius R is not particularly limited, and may be, for example, 1 mm or more, 1.5 mm or more, 2 mm or more, or 2.5 mm or more. The radius R may be, for example, 5 mm or less, 4.5 mm or less, 4 mm or less, or 3.5 mm or less.

[0031] As shown in FIG. 6C, the height H (depth) of the recess 12d is not particularly limited, but may be, for example, 1 mm or more, 1.5 mm or more, or 2 mm or more. This increases the surface area of ​​the outer side surface 12a1 of the bottom wall 12a, and the power storage device 100 can be cooled or heated more effectively. The height H of the recess 12d may be, for example, 5 mm or less, 4 mm or less, or 3 mm or less. When the inner side surface 12a2 of the bottom wall 12a of the power storage device 100 has a protrusion 12f corresponding to the recess 12d, if the height H of the recess 12d is too high, the storage space for the electrode body 20 inside the case 10 may be narrowed, and the energy density may be reduced. The height of the protrusion 12f is the same as the height H of the recess 12d.

[0032] Angle θ (see FIG. 6C) of side surface 12i of recess 12d with respect to the opening of recess 12d is not particularly limited, and may be, for example, 15° or more, 30° or more, or 45° or more. Also, angle θ may be, for example, 90° or less, 75° or less, or 60° or less. When recess 12d is formed by press molding, angle θ is preferably 90° or less from the viewpoint of ease of molding.

[0033] In a plan view, when the plan area S including the opening area of ​​the recess 12d on the outer side surface 12a1 of the bottom wall 12a (first wall) is taken as 100%, the total ratio of the opening area S1 of the recess 12d is, for example, 10% or more, preferably 20% or more, and more preferably 30% or more. This sufficiently increases the surface area of ​​the outer side surface 12a1 of the bottom wall 12a, and the power storage device 100 can be cooled or heated more effectively. In addition, when the plan area S including the opening area of ​​the recess 12d on the outer side surface 12a1 of the bottom wall 12a is taken as 100%, the total ratio of the opening area S1 of the recess 12d can be, for example, 60% or less, 50% or less, or 40% or less. If the ratio of the opening area of ​​the recess 12d is too high, the strength of the bottom wall 12a of the case 10 may be impaired. In this specification, the total area of ​​bottom surface 12e and side surface 12i of recess 12d is referred to as the internal area of ​​recess 12d, and the opening area of ​​recess 12d refers to the area of ​​the opening excluding the internal area (see FIG. 6C).

[0034] The total ratio of the internal area of ​​the recesses 12d to the surface area of ​​the outer side surface 12a1 of the bottom wall 12a (first wall) (including the internal area of ​​the recesses 12d, not including the opening area of ​​the recesses 12d) is, for example, 20% or more, preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. This sufficiently increases the surface area of ​​the outer side surface 12a1 of the bottom wall 12a, and allows the electricity storage device 100 to be cooled or heated more effectively. In addition, the ratio of the internal area of ​​the recesses 12d to the surface area of ​​the outer side surface 12a1 of the bottom wall 12a (first wall) is, for example, 80% or less, and preferably 70% or less.

[0035] The efficiency of cooling or heating the power storage device 100 is particularly required when the power storage device 100 is large, and the present technology is highly effective in such cases. Therefore, the planar area S including the opening area of ​​the recess 12d on the outer side surface 12a1 of the bottom wall 12a is set to, for example, 50 cm 2 More than 100cm 2 Over 120cm 2 It could be more than that.

[0036] As shown in FIGS. 2 to 4, in this embodiment, the outer surface of the case 10 is covered with an insulating sheet 96. The insulating sheet 96 ensures insulation of the case 10 when the electricity storage module 500 is submerged in water. In this embodiment, the outer surface of the first side wall 12b and the outer surface of the second side wall 12c are covered with the insulating sheet 96. The insulating sheet 96 may also be arranged on the outer surface 12a1 of the bottom wall 12a. It is preferable that the insulating sheet 96 is not arranged in the recess 12d. By not arranging the insulating sheet 96 in the recess 12d, the electricity storage device 100 can be cooled or heated effectively. The insulating sheet 96 is made of resin, and may be made of, for example, polyolefin such as polyethylene (PE).

[0037] The positive electrode terminal 30 is attached to one end of the sealing plate 14 in the long side direction Y (the left end in FIG. 2). The negative electrode terminal 40 is attached to the other end of the sealing plate 14 in the long side direction Y (the right end in FIG. 2). The positive electrode terminal 30 and the negative electrode terminal 40 are preferably attached to the sealing plate 14. The positive electrode terminal 30 and the negative electrode terminal 40 are inserted into the terminal pull-out holes 18, 19, and are partially exposed on the surface of the sealing plate 14. The positive electrode terminal 30 and the negative electrode terminal 40 are electrically connected to another electricity storage device or an external device via an external connection member such as a bus bar.

[0038] As shown in FIG. 2, the positive electrode terminal 30 is electrically connected to the positive electrode 22 (see FIG. 5) of the electrode assembly 20 inside the case 10 via a positive electrode current collecting member 50 and a positive electrode tab group 22g (i.e., a plurality of stacked positive electrode tabs 22t) described later. The positive electrode terminal 30 is also electrically connected to an external positive electrode current collecting member 52 outside the case 10. The positive electrode terminal 30 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy, for example. The negative electrode terminal 40 is electrically connected to the negative electrode 24 (see FIG. 5) of the electrode assembly 20 inside the case 10 via a negative electrode current collecting member 60 and a negative electrode tab group 24g (i.e., a plurality of stacked negative electrode tabs 24t) described later. The negative electrode terminal 40 is also electrically connected to an external negative electrode current collecting member 62 outside the case 10. The negative electrode terminal 40 is preferably made of metal, and more preferably made of copper or a copper alloy, for example. The positive electrode terminal 30 and the negative electrode terminal 40 are insulated from the sealing plate 14 by a gasket 92. The gasket 92 is preferably made of resin.

[0039] The positive current collecting member 50 is a conductive member, and is attached to the sealing plate 14 here. As shown in FIG. 2, the positive current collecting member 50 is insulated from the inner surface of the sealing plate 14 by an internal insulating member 94 made of resin. The positive current collecting member 50 electrically connects the positive electrode tab group 22g of the electrode body 20 and the positive electrode terminal 30. The positive current collecting member 50 has a plate-shaped first region extending in the long side direction Y along the inner surface of the sealing plate 14. One end (the right side in FIG. 2) of the positive current collecting member 50 (specifically, the first region) in the long side direction Y is electrically connected to the positive electrode tab group 22g. The other end (the left side in FIG. 2) of the positive current collecting member 50 (specifically, the first region) in the long side direction Y is electrically connected to the lower end 30c of the positive electrode terminal 30. The positive current collecting member 50 is preferably made of a metal having excellent electrical conductivity, for example, aluminum or an aluminum alloy. The positive electrode current collecting member 50 may be made of the same type of metal as the positive electrode tab 22t and / or the positive electrode terminal 30.

[0040] The external positive current collecting member 52 is a conductive member and is electrically connected to the positive terminal 30 outside the case 10. Here, the external positive current collecting member 52 is insulated from the outer surface of the sealing plate 14 by a gasket 92. The external positive current collecting member 52 has a plate-shaped portion extending in the direction Y along both sides of the outer surface of the sealing plate 14. A conductive member such as a bus bar can be connected to the plate-shaped portion. The external positive current collecting member 52 is preferably made of a metal having excellent conductivity, for example, aluminum or an aluminum alloy. The external positive current collecting member 52 can be made of the same type of metal as the positive terminal 30. The external positive current collecting member 52 is not an essential component.

[0041] The negative current collecting member 60 is a conductive member, and is attached to the sealing plate 14 here. The negative current collecting member 60 is insulated from the inner surface of the sealing plate 14 by an internal insulating member 94 made of resin. The negative current collecting member 60 electrically connects the negative electrode tab group 24g of the electrode body 20 and the negative electrode terminal 40. As shown in FIG. 2, the negative current collecting member 60 has a plate-shaped first region extending in the long side direction Y along the inner surface of the sealing plate 14. One end (the left side in FIG. 2) of the negative current collecting member 60 (specifically, the first region) in the long side direction Y is electrically connected to the negative electrode tab group 24g. The other end (the right side in FIG. 2) of the negative current collecting member 60 (specifically, the first region) in the long side direction Y is electrically connected to the lower end 40c of the negative electrode terminal 40. The negative current collecting member 60 is preferably made of a metal having excellent electrical conductivity, for example, copper or a copper alloy. The negative electrode current collecting member 60 may be made of the same type of metal as the negative electrode tab 24t and / or the negative electrode terminal 40.

[0042] The external negative current collecting member 62 is a conductive member and is electrically connected to the negative terminal 40 outside the case 10. Here, the external negative current collecting member 62 is insulated from the outer surface of the sealing plate 14 by a gasket 92. The external negative current collecting member 62 has a plate-shaped portion extending in the direction Y along both sides of the outer surface of the sealing plate 14. A conductive member such as a bus bar can be connected to the plate-shaped portion. The external negative current collecting member 62 is preferably made of a metal having excellent conductivity, for example, copper or a copper alloy. The external negative current collecting member 62 can be made of the same type of metal as the negative terminal 40. The external negative current collecting member 62 is not an essential component.

[0043] As shown in Figs. 3 and 4, in the electricity storage device 100 of this embodiment, a plurality of electrode bodies 20 (specifically, two) are accommodated in the case 10. However, the number of electrode bodies 20 arranged in one case 10 is not particularly limited, and may be one or may be three or more. The electrode body 20 is arranged inside the case 10 in a state where it is covered with a resin sheet 29 (insulating member) having insulating properties. This prevents the electrode body 20 from coming into direct contact with the exterior body 12. The resin sheet 29 may be made of, for example, polyolefin such as polyethylene (PE). The resin sheet 29 may be configured to be in the shape of a bag or a box.

[0044] As shown in Figures 2 and 5, the electrode body 20 has a first lamination end surface 20a. The lamination end surface is a surface on which an end of a positive electrode and an end of a negative electrode are arranged. It is preferable that the lamination end surface is not covered with a separator (i.e., the end of the positive electrode 22 and the end of the negative electrode 24 are exposed). In this embodiment, the electrode body 20 is a wound electrode body. In the wound electrode body, the lamination end surface is a surface perpendicular to the winding axis.

[0045] 5 indicates the longitudinal direction of the electrode assembly 20 manufactured in a strip shape. In the longitudinal direction LD, the winding start end side is indicated as S, and the winding end side is indicated as E. Also, the symbol WD in FIG. 5 indicates a direction perpendicular to the longitudinal direction LD, and indicates the winding axis direction of the electrode assembly 20. Here, the winding axis direction WD is approximately parallel to the up-down direction Z of the electricity storage device 100.

[0046] The electrode body 20 has a flat outer shape as shown in Figs. 2 and 3. The flat electrode body 20 has a pair of curved portions 20r whose outer surfaces are curved, and a flat portion 20f whose outer surface is flat and connects the pair of curved portions 20r. As shown in Fig. 5, the electrode body 20 has a first lamination end face 20a and a second lamination end face 20b perpendicular to the winding axis direction WD. The first lamination end face 20a and the second lamination end face 20b face each other. The first lamination end face 20a is a lamination end face on the side where the positive electrode tab 22t and the negative electrode tab 24t are not formed. The second lamination end face 20b is a lamination end face on which the positive electrode tab 22t and the negative electrode tab 24t are formed. The first lamination end face 20a of the electrode body 20 is arranged in a direction in which the first lamination end face 20a faces the inner surface 12a2 of the bottom wall 12a. In other words, the electrode body 20 is housed inside the case 10 with the winding axis direction WD perpendicular to the sealing plate 14 and the bottom wall 12a. At this time, the second stacking end face 20b faces the sealing plate 14. As shown in FIG. 3, the pair of curved portions 20r faces the pair of second side walls 12c of the exterior body 12, and the flat portion 20f faces the first side wall 12b of the exterior body 12. The stacking end face (the first stacking end face 20a or the second stacking end face 20b, preferably the first stacking end face 20a) faces the bottom wall 12a (the first wall), so that the temperature of the electricity storage device 100 (particularly the temperature of the electrode body 20) can be effectively cooled or heated. This is because the stacking end face is the end of the positive electrode 22 or the end of the negative electrode 24, and the temperature is easily transmitted to the inside of the electrode body 20.

[0047] In addition, the electrode body 20 is not limited to a wound electrode body as long as it has a laminated end surface. In another embodiment, for example, the electrode body 20 may be a laminated electrode body in which a plurality of square-shaped (typically rectangular) positive electrodes and a plurality of square-shaped (typically rectangular) negative electrodes are stacked in an insulated state. The effect of the present technology is exerted by arranging the laminated end surface of the laminated electrode body so as to face the inner surface of the first wall.

[0048] As shown in FIG. 5, the electrode body 20 is configured by stacking a strip-shaped first separator 26, a strip-shaped negative electrode 24, a strip-shaped second separator 27, and a strip-shaped positive electrode 22, and winding them around a winding axis WL.

[0049] The positive electrode 22 may be the same as a conventional one, and is not particularly limited. As shown in FIG. 5, the positive electrode 22 has a positive electrode current collector foil 22c and a positive electrode active material layer 22a fixed on at least one surface of the positive electrode current collector foil 22c. The positive electrode current collector foil 22c is strip-shaped. The positive electrode current collector foil 22c is preferably made of metal, and more preferably made of metal foil. In this embodiment, the positive electrode current collector foil 22c is an aluminum foil.

[0050] A plurality of positive electrode tabs 22t are provided at one end of the positive electrode current collector foil 22c in the winding axis direction WD (width direction perpendicular to the longitudinal direction LD). The plurality of positive electrode tabs 22t protrude toward one side of the winding axis direction WD. The plurality of positive electrode tabs 22t protrude in the winding axis direction WD beyond the first separator 26 and the second separator 27. The positive electrode tab 22t is a part of the positive electrode current collector foil 22c here, and is made of a metal foil (aluminum foil). The plurality of positive electrode tabs 22t are stacked at one end of the winding axis direction WD to form a positive electrode tab group 22g. The positive electrode tab group 22g is provided on the second stack end surface 20b. The positive electrode tab group 22g is electrically connected to the positive electrode terminal 30 via the positive electrode current collector member 50.

[0051] As shown in Fig. 5, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction LD of the positive electrode current collector foil 22c. The positive electrode active material layer 22a contains a positive electrode active material capable of reversibly absorbing and releasing charge carriers. An example of the positive electrode active material is a lithium transition metal composite oxide. The positive electrode active material layer 22a may contain any component other than the positive electrode active material, such as various additive components such as a binder and a conductive material.

[0052] The negative electrode 24 may be the same as a conventional one, and is not particularly limited. As shown in FIG. 5, the negative electrode 24 has a negative electrode current collector foil 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector foil 24c. The negative electrode current collector foil 24c is strip-shaped. The negative electrode current collector foil 24c is preferably made of metal, and more preferably made of metal foil. Here, the negative electrode current collector foil 24c is copper foil.

[0053] A plurality of negative electrode tabs 24t are provided in the winding axis direction WD (width direction perpendicular to the longitudinal direction LD) of the negative electrode current collector foil 24c. The plurality of negative electrode tabs 24t protrude toward one side of the winding axis direction WD. The plurality of negative electrode tabs 24t protrude in the winding axis direction WD beyond the first separator 26 and the second separator 27. The negative electrode tab 24t is a part of the negative electrode current collector foil 24c here, and is made of a metal foil (copper foil). The plurality of negative electrode tabs 24t are stacked at one end of the winding axis direction WD to form a negative electrode tab group 24g. The negative electrode tab group 24g is provided at an end on the same side as the end where the positive electrode tab group 22g is provided in the winding axis direction WD. The negative electrode tab group 24g is provided on the second stacking end surface 20b. The negative electrode tab group 24g is electrically connected to the negative electrode terminal 40 via the negative electrode current collector member 60.

[0054] As shown in Fig. 5, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction LD of the negative electrode current collector foil 24c. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. Examples of the negative electrode active material include carbon materials such as graphite. The negative electrode active material layer 24a may contain any component other than the negative electrode active material, such as various additive components such as a binder, a thickener, a dispersant, etc.

[0055] The first separator 26 is disposed between the positive electrode 22 and the negative electrode 24. The first separator 26 is a member that insulates the positive electrode 22 and the negative electrode 24. The second separator 27 is disposed in the outermost layer of the electrode body 20. Inside the wound electrode body 20, the second separator 27 is disposed between the positive electrode 22 and the negative electrode 24. The second separator 27 is a member that insulates the positive electrode 22 and the negative electrode 24 inside the electrode body 20. As the first separator 26 and the second separator 27, for example, a porous sheet made of a resin made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable.

[0056] The electrolyte can be any electrolyte used in a general power storage device without any particular limitations. An example of the electrolyte is a non-aqueous electrolyte in which a supporting salt is dissolved in a non-aqueous solvent. In the non-aqueous electrolyte used in a lithium ion secondary battery, a carbonate-based solvent such as ethylene carbonate, dimethyl carbonate, or ethyl methyl carbonate can be used as the non-aqueous solvent. In addition, a fluorine-containing lithium salt such as LiPF6 can be used as the supporting salt. The electrolyte may contain an additive as necessary.

[0057] The amount of the electrolyte is not particularly limited, but when the electricity storage device 100 is fully charged (i.e., the state of charge (SOC) is 100%), the liquid level of the electrolyte located between the case 10 and the electrode body 20 is preferably 1 / 5 or more, more preferably 2 / 5 or more, of the height of the case 10. The liquid level of the electrolyte refers to the liquid level when the first wall (here, the bottom wall 12a) of the case 10 is placed in the vertical direction (the direction of gravity). The height of the case 10 refers to the height in the vertical direction Z from the inner surface of the first wall of the case 10 (here, the inner surface 12a2 of the bottom wall 12a). By having a large amount of electrolyte located between the case 10 and the electrode body 20, the electricity storage device 100 can be cooled or heated more effectively.

[0058] The temperature adjustment unit 400 is disposed so as to face the outer surface of the first wall of the power storage device 100. Preferably, the temperature adjustment unit 400 is in contact with the outer surface of the power storage device 100. As shown in FIG. 6D, in this embodiment, the temperature adjustment unit 400 is disposed so as to face the outer surface 12a1 of the bottom wall 12a of the plurality of power storage devices 100. The temperature adjustment unit 400 may be capable of cooling and / or heating the plurality of power storage devices 100. In this embodiment, as shown in FIG. 1, the temperature adjustment unit 400 includes a thin portion 410, a thick portion 420, a convex portion 432, and a convex portion group 430 in which a plurality of the convex portions 432 are gathered. As shown in FIG. 6D, in this embodiment, a hollow portion 422 is provided inside the thick portion 420. The hollow portion 422 is filled with a temperature adjustment medium, for example, a cooling medium or a heating medium. Thinner portion 410 and thicker portion 420 are preferably made of a thermally conductive material, for example aluminum.

[0059] As shown in FIG. 1, the thin-walled portion 410 includes an inlet 412 and an outlet 414. The inlet 412 is a portion that supplies the temperature control medium to the inside of the temperature control portion 400. The supplied temperature control medium is supplied to the hollow portion 422 of the thick-walled portion 420. The outlet 414 is a portion that discharges the temperature control medium in the hollow portion 422 from the temperature control portion 400. The temperature control medium discharged from the outlet 414 may be introduced again into the inlet 412 to circulate the temperature control medium. In this case, the temperature control medium may be cooled or heated before being introduced into the inlet 412 after being discharged from the outlet 414.

[0060] The temperature control medium may be a liquid or a gas. Examples of liquids used as the temperature control medium include water, a coolant, etc. Examples of gases used as the temperature control medium include air.

[0061] The temperature control unit 400 is not limited to the one using the temperature control medium as described above. For example, the temperature control unit 400 may include an electric heating wire.

[0062] A part of the temperature adjustment unit 400 is preferably disposed inside the recess 12d of the outer side surface 12a1 of the bottom wall 12a (first wall) of the power storage device 100. This allows the power storage device 100 to be cooled or heated more effectively. In this embodiment, as shown in Figs. 1 and 6D, a plurality of protrusions 432 are provided on the surface of the thick portion 420 facing the first wall of the power storage device 100. As shown in Fig. 6D, the protrusions 432 protrude from the surface of the thick portion 420 toward the outer side surface 12a1 of the bottom wall 12a of the power storage device 100. At least a part of the protrusions 432 of the temperature adjustment unit 400 is disposed inside the recess 12d of the bottom wall 12a. The protrusions 432 of the temperature adjustment unit 400 are provided so as to correspond to the shape of the recess 12d.

[0063] 1, the temperature adjustment unit 400 has a plurality of convex portion groups 430 each including a plurality of convex portions 432. In each of the plurality of convex portion groups 430, the convex portions 432 are arranged so as to correspond to the positions of the concave portions 12d of the bottom wall 12a of the opposing power storage device 100. The number of convex portion groups 430 may be the same as the number of power storage devices 100 included in the power storage module 500. However, the convex portion groups 430 do not necessarily need to face the bottom wall 12a of the power storage device 100, and the number of convex portion groups 430 may be smaller than the number of power storage devices 100 included in the power storage module 500.

[0064] The cavity 422 is preferably also provided inside the protruding portion 432 of the temperature adjustment portion 400. This allows the temperature adjustment medium to be supplied also inside the protruding portion 432, and the electricity storage device 100 can be cooled or heated more effectively.

[0065] The temperature adjustment unit 400 may be provided with a heat conductive member on a surface that comes into contact with at least one first wall of the power storage device 100. A known heat conductive member may be used, and may be made of, for example, silicone rubber. The shape of the heat conductive member is not particularly limited, and may be, for example, sheet-like. By providing the temperature adjustment unit 400 with a heat conductive member, it is possible to fill a gap that may occur between the temperature adjustment unit 400 and the outer surface of the first wall of the power storage device 100, and therefore it is possible to more effectively cool or heat the power storage device 100.

[0066] The power storage module 500 can be used for various purposes, but can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, a truck, etc. The type of vehicle is not particularly limited, but examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), a battery electric vehicle (BEV), etc.

[0067] Although the preferred embodiment of the present technology has been described above, the above embodiment is merely an example. The present technology can be implemented in various other forms. The technology described in the claims includes various modifications and changes to the above-exemplified embodiment. For example, it is possible to replace a part of the above-mentioned embodiment with another modification, and it is also possible to add another modification to the above-mentioned embodiment. Furthermore, if the technical feature is not described as essential, it is also possible to delete it as appropriate.

[0068] For example, in the above-described embodiment, the shape of the recess 12d provided on the outer side surface 12a1 of the bottom wall 12a of the case 10 was a truncated cone. However, the shape of the recess 12d is not limited to this. FIG. 7A is a plan view that shows a typical arrangement pattern of the recesses on the bottom wall of the case of the power storage device in the first modification. FIG. 7B is a plan view that shows a typical shape of the recesses on the bottom wall of the case of the power storage device in the first modification. FIG. 7C is a cross-sectional view that shows a typical shape of the recesses on the bottom wall of the case of the power storage device in the first modification. As shown in FIGS. 7A to 7C, in the first modification, a truncated pyramidal recess 12d1 is provided on the outer side surface 12a1 of the bottom wall 12a of the case. The recess 12d1 is gradually narrowed toward the bottom surface 12e1. The recess 12d1 has a side surface 12i1 between the outer side surface 12a1 of the bottom wall 12a and the bottom surface 12e1 of the recess 12d1.

[0069] 7B and 7C, the opening of the recess 12d1 is a square with a side length of x. The length x is not particularly limited, but may be, for example, 2 mm or more, 3 mm or more, 4 mm or more, or 5 mm or more. The length x may be, for example, 8 mm or less, 7 mm or less, or 6 mm or less.

[0070] The height H1 (depth) of the recess 12d1 may be similar to the height H of the protrusion 12f in the above-described embodiment. The angle θ1 of the side surface 12i1 of the recess 12d1 when the opening of the recess 12d1 is used as a reference may be similar to the angle θ of the protrusion 12f in the above-described embodiment.

[0071] FIG. 8A is a plan view showing a typical arrangement pattern of recesses on a bottom wall of a case of an electricity storage device in Modification 2. FIG. 8B is a plan view showing a typical shape of recesses on a bottom wall of a case of an electricity storage device in Modification 2. FIG. 8C is a cross-sectional view showing a typical shape of recesses on a bottom wall of a case of an electricity storage device in Modification 2. As shown in FIGS. 8A to 8C, in Modification 2, an arc-shaped recess 12d2 is provided on an outer side surface 12a1 of a bottom wall 12a of the case. The recess 12d2 has a curved bottom surface 12e2. The opening of the recess 12d2 is a circle having a radius R2 in a plan view. The radius R2 may be the same as the radius R of the opening of the recess 12d in the above-mentioned embodiment. The height H2 (depth) of the recess 12d2 may be the same as the height H of the recess 12d in the above-mentioned embodiment.

[0072] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A power storage module comprising a plurality of power storage devices and a temperature adjustment unit, wherein the power storage devices include an electrode body including a positive electrode and a negative electrode, an electrolyte, and a case for accommodating the electrode body and the electrolyte, the case including a first wall having an outer surface with a recess, the temperature adjustment unit being disposed so as to face the outer surface of the first wall, and a stacking end face of the electrode body being disposed in a direction facing the inner surface of the first wall. Item 2: The power storage module according to item 1, wherein a portion of the temperature adjustment section is disposed within the recess. Item 3: The number of the recesses with respect to a planar area including an opening area of ​​the recesses on the outer surface of the first wall is 1 / cm 2 Item 3. The power storage module according to item 1 or 2. Item 4: The energy storage module according to any one of items 1 to 3, wherein the first wall is a bottom wall of the case, and when the energy storage device is fully charged, the height of a liquid surface of the electrolyte located between the case and the electrode body is 1 / 5 or more of the height of the case. Item 5: The electricity storage module according to any one of items 1 to 4, wherein an outer surface of the case is covered with an insulating sheet, and the insulating sheet is not disposed in the recess. Item 6: The energy storage module according to any one of items 1 to 5, wherein the first wall is a rectangular bottom wall of the case, the bottom wall has a row in which a plurality of the recesses are arranged in a long side direction of the bottom wall, a plurality of the rows are provided in a short side direction of the bottom wall, and the plurality of the recesses are arranged at a distance from each other. Item 7: The energy storage module according to any one of items 1 to 6, wherein a convex portion corresponding to the concave portion is provided on an inner surface of the first wall, and the convex portion is in contact with the electrode body directly or via an insulating member. Item 8: An electricity storage device comprising an electrode assembly including a positive electrode and a negative electrode, an electrolyte, and a case for accommodating the electrode assembly and the electrolyte, wherein the case has a first wall having an outer surface with a recess, and a stacking end face of the electrode assembly is arranged facing an inner surface of the first wall. Item 9: The number of the recesses with respect to the planar area including the opening area of ​​the recesses on the outer surface of the first wall is 1 / cm 2 Item 9. The electricity storage device according to item 8. Item 10: The electricity storage device according to item 8 or 9, wherein the first wall is a bottom wall of the case, and when the electricity storage device is fully charged, the height of a liquid surface of the electrolyte located between the case and the electrode body is 1 / 5 or more of the height of the case. Item 11: The energy storage device according to any one of items 8 to 10, wherein the first wall is a rectangular bottom wall of the case, the bottom wall has a row in which the recesses are aligned in a long side direction of the bottom wall, the rows are provided in a plurality of rows in a short side direction of the bottom wall, and the recesses are arranged at a distance from each other. Item 12: The electricity storage device according to any one of items 8 to 11, wherein a convex portion corresponding to the concave portion is provided on an inner surface of the first wall, and the convex portion is in contact with the electrode body directly or via an insulating member. [Explanation of symbols]

[0073] 10 Cases 12 Exterior body 12a Bottom wall 12d Recess 20 Electrode body 30 Positive terminal 40 Negative terminal 100 Energy storage device 200 Spacer 300 Restraint mechanism 400 Temperature control section 430 Convex Group 432 Convex 500 Energy Storage Module

Claims

1. A plurality of power storage devices; Temperature control unit and A power storage module comprising: The power storage device is An electrode assembly including a positive electrode and a negative electrode; An electrolyte; a case for accommodating the electrode assembly and the electrolyte; Including, the electrode body is a wound electrode body in which the strip-shaped positive electrode and the strip-shaped negative electrode are stacked with a separator interposed therebetween and wound around a winding axis, The electrode body has a lamination end surface that is a surface perpendicular to the winding axis, The case includes a first wall as a bottom wall, the first wall having an outer surface on which a plurality of recesses are provided, A plurality of protrusions corresponding to the plurality of recesses are provided on an inner surface of the first wall, The plurality of protrusions are in contact with the electrode body directly or via an insulating member, when the power storage device is fully charged, a liquid level of the electrolyte located between the case and the electrode body is equal to or greater than ⅕ of a height of the case; the temperature adjustment unit is disposed so as to face the outer surface of the first wall, The stacking end surface of the electrode body is arranged to face the inner surface of the first wall. Energy storage module.

2. The power storage module according to claim 1 , wherein a portion of the temperature adjustment section is disposed within the recess.

3. The number of the recesses relative to a planar area including an opening area of ​​the recesses on the outer surface of the first wall is 1 / cm. ２ The power storage module according to claim 1 or 2.

4. An energy storage module as described in claim 1 or 2, wherein the total proportion of the internal area of ​​the multiple recesses to the surface area of ​​the outer surface of the first wall is 60% or more and 80% or less.

5. The outer surface of the case is covered with an insulating sheet, The insulating sheet is not disposed in the recess. The energy storage module according to claim 1 or 2.

6. the first wall is rectangular; The first wall has a row of the recesses aligned in a long side direction of the first wall, A plurality of the rows are provided in a short side direction of the first wall, The plurality of recesses are spaced apart. The energy storage module according to claim 1 or 2.

7. The temperature control section has a surface facing the first wall, the surface having a plurality of protrusions protruding toward the first wall, the plurality of protrusions of the temperature adjustment portion are disposed inside the plurality of recesses of the first wall, A cavity into which a temperature control medium is supplied is provided inside the plurality of protrusions of the temperature control unit. The energy storage module according to claim 1 or 2.

8. An electrode assembly including a positive electrode and a negative electrode; An electrolyte; a case for accommodating the electrode assembly and the electrolyte; A power storage device comprising: the electrode body is a wound electrode body in which the strip-shaped positive electrode and the strip-shaped negative electrode are stacked with a separator interposed therebetween and wound around a winding axis, The electrode body has a lamination end surface that is a surface perpendicular to the winding axis, The case includes a first wall as a bottom wall, the first wall having an outer surface on which a plurality of recesses are provided, A plurality of protrusions corresponding to the plurality of recesses are provided on an inner surface of the first wall, The plurality of protrusions are in contact with the electrode body directly or via an insulating member, when the power storage device is fully charged, a liquid level of the electrolyte located between the case and the electrode body is equal to or greater than ⅕ of a height of the case; The stacking end surface of the electrode body is arranged to face the inner surface of the first wall. Energy storage device.

9. The number of the recesses relative to a planar area including an opening area of ​​the recesses on the outer surface of the first wall is 1 / cm. ２ The electricity storage device according to claim 8 .

10. An electricity storage device as described in claim 8 or 9, wherein the total proportion of the internal area of ​​the multiple recesses to the surface area of ​​the outer surface of the first wall is 60% or more and 80% or less.

11. the first wall is rectangular; The first wall has a row of the recesses aligned in a long side direction of the first wall, A plurality of the rows are provided in a short side direction of the first wall, The plurality of recesses are spaced apart. The electricity storage device according to claim 8 or 9.

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