JP7559410B2 - Power storage device - Google Patents

Description

The present invention relates to an energy storage device that includes an energy storage element and a spacer.

Conventionally, there is known a storage device that includes a storage element and a spacer, where the spacer has a wall portion around the storage element. For example, Patent Document 1 discloses a battery module (storage device) that includes a battery cell (storage element) and a spacer, where the spacer has a side wall portion, a bottom wall portion, and an upper wall portion around the battery cell.

JP 2017-174831 A

In a configuration in which the spacer has a wall portion around the storage element, as in the conventional storage device, a gap (wobble) may occur between the wall portion and the storage element due to dimensional tolerances, etc. If a member is also arranged on the opposite side of the wall portion from the storage element, a gap (wobble) may occur between the wall portion and the member due to dimensional tolerances, etc. For example, in the conventional storage device, the side wall portion of the spacer is arranged between the storage element (battery cell) and the side plate, and the bottom wall portion of the spacer is arranged between the storage element and the base plate. For this reason, a gap may occur between the side wall portion of the spacer and the storage element or the side plate, or between the bottom wall portion of the spacer and the storage element or the base plate. In such a case, the storage element, etc. may move within the storage device due to vibration or impact being applied to the storage device, which may damage the internal members of the storage device.

The present invention was made by the inventors with a new focus on the above problem, and aims to provide an electricity storage device that can prevent damage to internal components.

In order to achieve the above object, an energy storage device according to one embodiment of the present invention is an energy storage device including an energy storage element and a spacer arranged side by side in a first direction, the spacer having a first wall portion facing the energy storage element in a second direction intersecting the first direction, a protrusion protruding from the first wall portion in the second direction, a second wall portion arranged in a position adjacent to the first wall portion in a third direction intersecting the first direction and the second direction, and a deformation portion arranged between the first wall portion and the second wall portion, which allows the first wall portion to deform more relative to the second wall portion than other adjacent portions.

According to this, in the energy storage device, the spacer aligned in the first direction with the energy storage element has a protrusion protruding in the second direction from a first wall portion facing the energy storage element in the second direction. Furthermore, the spacer has a deformation portion between the first wall portion and the second wall portion adjacent in the third direction, which allows the first wall portion to be significantly deformed relative to the second wall portion. In this way, since the spacer has a protrusion protruding from the first wall portion toward the energy storage element or in the opposite direction to the energy storage element, even if a gap (wobble) occurs between the first wall portion and the energy storage element or the member opposite the energy storage element, the protrusion can fill the gap. As a result, even if the energy storage device is subjected to vibration or impact, the energy storage element, etc. can be prevented from moving within the energy storage device, and therefore damage to the internal members of the energy storage device can be prevented.

Furthermore, when the spacer is provided with the above-mentioned protrusion, if the gap between the first wall portion and the storage element or the member opposite the storage element is small or if the protrusion is hard, the protrusion may not be crushed sufficiently, causing damage to the spacer, the storage element, or the member. For this reason, a deformation portion that enables deformation of the first wall portion is disposed between the first wall portion and the second wall portion on which the protrusion is provided. As a result, if the protrusion is not crushed sufficiently, the deformation portion deforms the first wall portion relative to the second wall portion, thereby preventing damage to the spacer, the storage element, or the member. Therefore, damage to the members inside the storage device can be prevented.

The spacer may further have a spacer body that faces the energy storage element in the first direction, and the portion of the first wall where the protrusion is formed may be connected to the spacer body and protrude from the spacer body in the first direction.

In this way, in the spacer, the portion of the first wall portion where the protrusion is formed is connected to the spacer body and protrudes from the spacer body, so that the portion can be prevented from deforming relative to the second wall portion more than if it were not connected to the spacer body. This prevents the portion from deforming too much relative to the second wall portion, which could damage the spacer or create a gap between the spacer and the energy storage element or the member on the opposite side to the energy storage element. Therefore, damage to the internal members of the energy storage device can be prevented.

The deformation portion may have at least one of a through portion formed by penetrating the area between the first wall portion and the second wall portion in the second direction, and a thin portion that is thinner in the second direction than the first wall portion and the second wall portion.

In this way, the deformation portion of the spacer can be easily formed by configuring it to have at least one of a through portion that penetrates the area between the first wall portion and the second wall portion, and a thin portion that is thinner than the first wall portion and the second wall portion. This makes it easy to prevent damage to the internal components of the energy storage device.

The spacer may also have a pair of second wall portions arranged at positions sandwiching the first wall portion in the third direction, and a pair of deformation portions arranged between the first wall portion and the pair of second wall portions.

With this, since the spacer has a pair of deformation portions between the first wall portion and the pair of second wall portions, the first wall portion can be easily deformed relative to the second wall portions, and the deformation can be balanced. This can further prevent damage to the internal components of the energy storage device.

The first wall portion may be thinner in the second direction than the second wall portion.

With this, in the spacer, the first wall portion is thinner than the second wall portion, so even if a protrusion is provided on the first wall portion, the first wall portion can be prevented from protruding on the side opposite the protrusion. This allows for space saving even with a configuration in which the first wall portion deforms relative to the second wall portion to prevent damage to the internal components of the energy storage device.

The first wall portion may also be arranged so that the surface opposite the protrusion side is closer to the protrusion side than the second wall portion.

In this way, in the spacer, the first wall portion is arranged with the surface opposite the protrusion side closer to the protrusion side than the second wall portion, so that even if the first wall portion deforms relative to the second wall portion, the first wall portion can be prevented from protruding on the side opposite the protrusion. This makes it possible to save space even with a configuration in which the first wall portion deforms relative to the second wall portion to prevent damage to internal components of the energy storage device.

The protrusion may also protrude in the second direction away from the energy storage element.

With this, since the projection of the spacer protrudes toward the opposite side to the energy storage element, even if a gap (wobble) occurs between the first wall portion and the member on the opposite side to the energy storage element, the projection can fill the gap. This makes it possible to prevent the energy storage element and the like from moving inside the energy storage device even if the energy storage device is subjected to vibration or impact. Furthermore, even if the projection is pressed against the member, the deformation portion deforms the first wall portion relative to the second wall portion, thereby preventing damage to the spacer or the member. Therefore, damage to the members inside the energy storage device can be prevented.

The present invention can be realized not only as an electricity storage device, but also as a spacer.

The electricity storage device of the present invention can prevent damage to internal components.

1 is a perspective view showing an external appearance of a power storage device according to an embodiment; 2 is a perspective view showing the inside of an exterior body with a main body and a lid separated in an energy storage device according to an embodiment; FIG. 2 is an exploded perspective view showing inner components of an exterior body of the energy storage device according to the embodiment; FIG. FIG. 2 is an exploded perspective view illustrating the components of the electricity storage unit according to the embodiment. FIG. 2 is an exploded perspective view showing each component of the energy storage element according to the embodiment. FIG. 2 is a perspective view showing a configuration of a spacer according to an embodiment. 4A and 4B are an enlarged perspective view and a top view showing a configuration of a recessed wall portion of a side wall portion of the spacer according to the embodiment. 4A and 4B are an enlarged perspective view and a top view showing a configuration of a flat wall portion of a rear wall portion of a spacer according to an embodiment. FIG. 2 is a perspective view showing a configuration of a side member according to the embodiment. 4 is a top view showing the positional relationship between a spacer, an energy storage element, and a side member in the embodiment. FIG.

The following describes an energy storage device according to an embodiment of the present invention (including its variations) with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection forms, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, the dimensions and other details are not strictly shown in each figure. Furthermore, the same reference numerals are used in each figure to identify identical or similar components.

In the following description and drawings, the X-axis direction is defined as the longitudinal direction of the exterior body of the energy storage device, the arrangement direction of the energy storage unit and the electrical equipment unit, the arrangement direction of the multiple side members, the extension direction of the end members, the opposing direction of the short side surfaces of the container of the energy storage element, or the arrangement direction of a pair of electrode terminals in one energy storage element. The Y-axis direction is defined as the arrangement direction of the energy storage element and the bus bar or bus bar frame, or the arrangement direction of the main body and the lid of the container of the energy storage element. The Z-axis direction is defined as the arrangement direction of the main body and the lid of the exterior body of the energy storage device, the arrangement direction of the pair of end members, the arrangement direction of the energy storage element, the spacer and the end member, the opposing direction of the long side surfaces of the container of the energy storage element, the flattening direction of the energy storage element, the stacking direction of the electrode plates of the electrode body of the energy storage element, or the up-down direction. These X-axis, Y-axis and Z-axis directions intersect each other (orthogonal in this embodiment). Note that, depending on the usage mode, it is possible that the Z-axis direction is not the up-down direction, but for convenience of explanation, the Z-axis direction will be described as the up-down direction below.

In the following description, for example, the positive X-axis direction refers to the direction of the X-axis arrow, and the negative X-axis direction refers to the opposite direction to the positive X-axis direction. The same applies to the Y-axis and Z-axis directions. In the following, the Z-axis direction may also be called the first direction or arrangement direction, the X-axis direction may also be called the second direction, and the Y-axis direction may also be called the third direction. Furthermore, expressions indicating relative directions or attitudes, such as parallel and perpendicular, may also include cases where the directions or attitudes are not strictly those. For example, saying that two directions are perpendicular does not only mean that the two directions are completely perpendicular, but also means that the directions are substantially perpendicular, that is, there is a difference of, for example, about a few percent.

(Embodiment)
[1 General Description of Power Storage Device 10]
First, a schematic configuration of the energy storage device 10 according to the present embodiment will be described. Fig. 1 is a perspective view showing the external appearance of the energy storage device 10 according to the present embodiment. Fig. 2 is a perspective view showing the inside of the exterior body 100 in the energy storage device 10 according to the present embodiment, with the main body and the lid of the exterior body 100 separated. Fig. 3 is an exploded perspective view showing the components inside the exterior body 100 of the energy storage device 10 according to the present embodiment.

The power storage device 10 is a device that can charge electricity from the outside and discharge electricity to the outside, and in this embodiment, has a substantially rectangular parallelepiped shape. For example, the power storage device 10 is a battery module (battery pack) used for power storage or power source applications. Specifically, the power storage device 10 is used as a battery for driving or starting the engine of a moving body such as an automobile, motorcycle, watercraft, ship, snowmobile, agricultural machinery, construction machinery, or railway vehicle for electric railways. Examples of the above-mentioned automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and gasoline-powered automobiles. Examples of the above-mentioned railway vehicles for electric railways include electric trains, monorails, linear motor cars, and hybrid trains equipped with both a diesel engine and an electric motor. The power storage device 10 can also be used as a stationary battery for home use or for power generation.

As shown in Figures 1 to 3, the energy storage device 10 includes an exterior body 100, and an energy storage unit 200 and an electric equipment unit 300 housed in the exterior body 100. In addition to the above components, the energy storage device 10 may also include an exhaust section for exhausting gas discharged from the energy storage unit 200 to the outside of the exterior body 100, and a connector connected to the electric equipment unit 300 by an electric wire or the like for transmitting signals to the outside.

The exterior body 100 is a box-shaped (approximately rectangular parallelepiped) container (module case) that constitutes the exterior body of the energy storage device 10. In other words, the exterior body 100 is arranged outside the energy storage unit 200 and the electric equipment unit 300, and fixes the energy storage unit 200 and the electric equipment unit 300 at a predetermined position to protect them from impacts and the like. The exterior body 100 is formed of, for example, an insulating material such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), ABS resin, or a composite material thereof, or a metal with an insulating coating. The exterior body 100 thereby prevents the power storage unit 200 and the electrical equipment unit 300 from coming into contact with external metal members, etc. Note that the exterior body 100 may be formed of a conductive member such as a metal, as long as the electrical insulation of the power storage unit 200 and the electrical equipment unit 300 is maintained.

The exterior body 100 has an exterior body main body 110 that constitutes the main body of the exterior body 100, and an exterior body lid body 120 that constitutes the lid body of the exterior body 100. The exterior body main body 110 is a bottomed rectangular cylindrical housing (chassis) with an opening formed on the positive side of the Z axis, and houses the energy storage unit 200 and the electric equipment unit 300. The exterior body main body 110 has a bottom wall portion 111, four side wall portions 112, and multiple protrusions 113.

The bottom wall 111 is disposed on the negative Z-axis side of the exterior body 110, and is a flat, rectangular wall that forms the bottom surface of the exterior body 110. A rib 111a is formed on the positive Z-axis surface of the bottom wall 111. The rib 111a is a convex portion that protrudes in the positive Z-axis direction from the positive Z-axis surface of the bottom wall 111, and a plurality of ribs 111a extending in the X-axis and Y-axis directions are formed over almost the entire surface of the positive Z-axis surface of the bottom wall 111. The four side walls 112 are disposed on both sides of the X-axis and Y-axis of the exterior body 110, and are four flat, rectangular walls that form two short sides on both sides of the X-axis and two long sides on both sides of the Y-axis of the exterior body 110.

The protrusions 113 are members that penetrate the bottom wall 111 in the Z-axis direction and protrude in the Z-axis positive direction from the surface of the bottom wall 111 in the Z-axis positive direction. In this embodiment, two protrusions 113 aligned in the Y-axis direction are disposed at each of the center in the X-axis direction and the end in the X-axis positive direction of the bottom wall 111. Each protrusion 113 is attached to the end member 230 and the side member 240 by inserting the portion protruding in the Z-axis positive direction from the bottom wall 111 into the openings (openings 230b and 244 described below) formed in the end member 230 and the side member 240.

For example, the protrusion 113 is a bolt such as a sealing bolt, and the male thread of the bolt is arranged to protrude in the Z-axis positive direction from the surface of the bottom wall 111 in the Z-axis positive direction beyond the rib 111a. The male thread of the protrusion 113 is screwed into a female thread formed in at least one of the openings 230b and 244, thereby attaching the bottom wall 111 to the end member 230 and the side member 240. In this embodiment, the male thread of the protrusion 113 passes through the opening 230b of the end member 230 and is screwed into the female thread of the opening 244 of the side member 240, thereby fixing the bottom wall 111 to the side member 240 with the end member 230 sandwiched between them.

In this way, one of the exterior body 100 and the side member 240 (in this embodiment, the exterior body 100) has a protrusion (protrusion 113) that protrudes toward the other (in this embodiment, the side member 240), and the other has an opening (opening 244) into which the protrusion is inserted. Then, the side member 240 is fixed to the exterior body 100 by fixing the protrusion (protrusion 113) to the other (side member 240) within the opening (opening 244).

The exterior body cover 120 is a flat rectangular member that closes the opening of the exterior body main body 110. The exterior body cover 120 is joined to the exterior body main body 110, preferably in an airtight or watertight manner, by adhesive, heat sealing, ultrasonic welding, laser welding, or the like. A pair of external terminals 130, which are a pair of module terminals (general terminals) on the positive and negative sides, are arranged on both ends of the exterior body cover 120 in the negative X-axis direction and in the Y-axis direction. The energy storage device 10 charges with electricity from the outside and discharges electricity to the outside via the pair of external terminals 130. The external terminals 130 are formed of a conductive member made of metal, such as aluminum, an aluminum alloy, copper, or a copper alloy.

The energy storage unit 200 has a shape that is flat in the Z-axis direction and elongated in the X-axis direction, with multiple energy storage elements 210 laid horizontally (turned over) and arranged (stacked) in the Z-axis direction and aligned in the X-axis direction. Specifically, the energy storage unit 200 has a configuration in which multiple energy storage elements 210 aligned in the Z-axis direction and the X-axis direction are sandwiched in the Z-axis direction and the X-axis direction by a pair of end members 230 and multiple (three) side members 240 together with a spacer 220. A more detailed explanation of the configuration of the energy storage unit 200 will be given later.

The electric equipment unit 300 has an electric equipment 310, an attachment member 320, and a busbar unit 330. The electric equipment 310 is an equipment that can monitor the state of the energy storage element 210 of the energy storage unit 200 and control the energy storage element 210. In this embodiment, the electric equipment 310 is a flat rectangular member that is arranged and attached in the positive direction of the X-axis of the energy storage unit 200. The electric equipment 310 has electric components such as a circuit board, a shunt resistor, and a connector that monitor the charging and discharging state of the energy storage element 210 and control the charging and discharging of the energy storage element 210. The electric equipment 310 has a configuration in which these electric components are housed in an insulating cover member.

The mounting member 320 is a flat plate-shaped member that mounts the electrical device 310 to the energy storage unit 200. The mounting member 320 is formed of, for example, any electrically insulating resin material that can be used for the exterior body 100 described above. The mounting member 320 is disposed between the energy storage unit 200 and the electrical device 310, and is attached to the energy storage unit 200 while the electrical device 310 is attached to it. In this embodiment, the mounting member 320 is attached to the side surface of the energy storage unit 200 in the positive direction of the X axis, so that the electrical device 310 is attached to the side surface of the energy storage unit 200 in the positive direction of the X axis in an upright position (a position parallel to the YZ plane).

Specifically, the mounting member 320 is attached to the end member 230 and the side member 240 of the energy storage unit 200, which will be described later. More specifically, the mounting member 320 has four protrusions 321 at both ends in the Z-axis direction and both ends in the Y-axis direction. The protrusions 321 have portions that protrude in the Z-axis direction toward the end member 230, and are attached to the end member 230 and the side member 240 by inserting these portions into openings (openings 230c and 244, which will be described later) formed in the end member 230 and the side member 240. For example, the protrusions 321 are bolts, and the male threads of the bolts are screwed into the female threads formed in at least one of the openings 230c and 244, thereby attaching the mounting member 320 to the end member 230 and the side member 240.

The busbar unit 330 has a busbar and a relay, and electrically connects the energy storage unit 200 and the electric device 310, electrically connects the electric device 310 and the external terminal 130, and electrically connects the energy storage unit 200 and the external terminal 130. The busbar is a plate-shaped member that connects the busbar 250 (described later) of the energy storage unit 200 to the electric device 310, connects the electric device 310 and the external terminal 130, connects the busbar 250 to the relay, and connects the relay to the external terminal 130. The busbar is formed of, for example, a conductive member made of a metal such as aluminum, an aluminum alloy, copper, a copper alloy, or nickel, or a combination of these, or a conductive member other than a metal.

[2. Description of the Configuration of the Energy Storage Unit 200]
Next, the configuration of the energy storage unit 200 will be described in detail with reference to Fig. 4 in addition to Fig. 3. Fig. 4 is an exploded perspective view showing the components of the energy storage unit 200 according to the present embodiment. Note that in Fig. 4, the bus bar 250 and the bus bar frame 251 of the energy storage unit 200 are omitted.

As shown in Figures 3 and 4, the energy storage unit 200 has a plurality of energy storage elements 210 (211, 212), a plurality of spacers 220 (221, 222), a pair of end members 230 (231, 232), three side members 240, a plurality of bus bars 250, and a bus bar frame 251.

The storage element 210 is a secondary battery (single cell) capable of charging and discharging electricity, and more specifically, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. The storage element 210 has a flat rectangular parallelepiped shape (rectangular shape). In this embodiment, eight storage elements 210 are arranged in the Z-axis direction and the X-axis direction in a horizontally placed (lying down) state (with the long side of the storage element 210 facing the Z-axis direction). Specifically, the four storage elements 211 on the negative side of the X-axis are arranged (stacked) in the Z-axis direction (arrangement direction), and the four storage elements 212 on the positive side of the X-axis are arranged (stacked) in the Z-axis direction (arrangement direction). The four storage elements 211 and the four storage elements 212 are arranged side by side in the X-axis direction. A detailed description of the configuration of the storage elements 210 (211, 212) will be described later.

The number of the storage elements 210 is not particularly limited, and any number of the storage elements 210 may be stacked (flat) in the Z-axis direction, or any number of the storage elements 210 may be arranged in the X-axis direction. In other words, the storage unit 200 may have only one storage element 210. The shape of the storage element 210 is not limited to the above-mentioned square shape, and may be other shapes such as a polygonal column shape, a cylindrical shape, an elliptical column shape, or an oblong column shape. The storage element 210 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The storage element 210 may not be a secondary battery, but may be a primary battery that can use stored electricity without the user having to charge it. The storage element 210 may be a battery using a solid electrolyte. The storage element 210 may be a pouch-type storage element.

The spacer 220 (221, 222) is a flat, rectangular member that is arranged (arranged) alongside the energy storage element 210 in the Z-axis direction (first direction, arrangement direction) and electrically insulates the energy storage element 210 from other components. The spacer 220 (221, 222) is formed, for example, from any electrically insulating resin material that can be used for the exterior body 100 described above.

Specifically, the spacers 221 are intermediate spacers (inter-cell spacers) arranged adjacent to the storage elements 210 in the Z-axis direction. That is, the spacers 221 are arranged between two adjacent storage elements 210 (between the two storage elements 211 and between the two storage elements 212) and electrically insulate the two storage elements 210. In this embodiment, three spacers 221 are arranged corresponding to the four storage elements 211, but when the number of storage elements 211 is other than four, the number of spacers 221 is appropriately changed according to the number of storage elements 211. The same applies to the storage elements 212.

The spacers 222 are end spacers that are arranged at the ends of the spacers 220 in the Z-axis direction (first direction, arrangement direction), and are arranged adjacent to the end storage elements 210 in the Z-axis direction. The spacers 222 are arranged between the end storage elements 210 (end storage elements 211 and 212) and the end members 230 (231, 232), and electrically insulate the end storage elements 210 from the end members 230 (231, 232). In other words, two spacers 222 are arranged on both sides of the four storage elements 211 in the Z-axis direction, and two spacers 222 are arranged on both sides of the four storage elements 212 in the Z-axis direction.

The spacer 220 (221, 222) has walls on both sides in the X-axis direction and on both sides in the Y-axis direction, and is electrically insulated from other components arranged on both sides of the energy storage element 210 in the X-axis direction and on both sides in the Y-axis direction. For example, the spacer 220 (221, 222) has walls arranged between the energy storage element 210 and the side member 240, and electrically insulates the energy storage element 210 from the side member 240. A detailed description of the configuration of the spacer 220 (221) will be given later.

The end member 230 and the side member 240 are members (restraining members) that compress (restrain) the energy storage element 210 from the outside in the Z-axis direction. In other words, the end member 230 and the side member 240 sandwich the multiple energy storage elements 210 and the multiple spacers 220 from both sides in the Z-axis direction, thereby compressing (restraining) each of the energy storage elements 210 and the multiple spacers 220 from both sides in the Z-axis direction. The end member 230 and the side member 240 are formed of metal members such as stainless steel, aluminum, aluminum alloy, iron, plated steel sheet, etc., but may also be formed of insulating members such as highly rigid resin.

The end members 230 (231, 232) are arranged in a position sandwiching the multiple storage elements 210 (211 and 212) and the multiple spacers 220 (221 and 222) in the Z-axis direction, and are a pair of flat plate-shaped members (end plates) that sandwich them in the Z-axis direction. As a result, the pair of end members 230 collectively restrain the multiple storage elements 210 and the multiple spacers 220 in the Z-axis direction (collectively apply a restraining force in the Z-axis direction to the multiple storage elements 210 and the multiple spacers 220). The end member 231 is the end member 230 on the negative side of the Z-axis of the pair of end members 230, and the end member 232 is the end member 230 on the positive side of the Z-axis. The end members 230 (231, 232) may be block-shaped or rod-shaped members instead of flat plate-shaped members.

The side member 240 is a flat member (side plate) arranged adjacent to the spacer 220 in the X-axis direction (second direction intersecting the first direction) and facing the spacer 220. Both ends of the side member 240 are attached to a pair of end members 230, and by connecting the pair of end members 230, the side member 240 restrains the multiple storage elements 210 and the multiple spacers 220. In other words, the side member 240 is arranged extending in the Z-axis direction so as to straddle the multiple storage elements 210 and the multiple spacers 220, and applies a restraining force to the multiple storage elements 210, etc. in the arrangement direction (Z-axis direction). Note that the side member 240 may be a block-shaped or rod-shaped member rather than a flat member.

In this embodiment, three side members 240 are arranged in the negative X-axis direction of the multiple storage elements 211, between the multiple storage elements 211 and the multiple storage elements 212, and in the positive X-axis direction of the multiple storage elements 212. In other words, in the X-axis direction (second direction), two sets of storage elements 210 and spacers 220 are arranged at positions sandwiching the central side member 240, and two side members 240 are arranged at positions sandwiching the two sets of storage elements 210 and spacers 220. These three side members 240 are attached to both ends in the X-axis direction and the center of a pair of end members 230 at both ends in the Z-axis direction. As a result, the end members 230 and the side members 240 sandwich and restrain the multiple storage elements 210 and the multiple spacers 220 from both sides in the X-axis direction and both sides in the Z-axis direction.

Specifically, the end members 230 (231, 232) have protrusions 230a (231a, 232a), and are connected (joined) to the respective side members 240 by the protrusions 230a. In this embodiment, three protrusions 230a aligned in the Y-axis direction are arranged at the center and both ends of the end member 230 in the X-axis direction. The protrusions 230a have portions that protrude in the Z-axis direction from the surface of the end member 230 facing the side member 240 toward the side member 240, and are attached to the side member 240 by being inserted into openings 243 formed in the side member 240.

For example, the protrusion 230a is a bolt, and the male thread of the bolt is screwed into the female thread formed in the opening 243, thereby attaching the end member 230 to the side member 240. Alternatively, the protrusion 230a is a self-tapping bolt (tapping bolt), and the end member 230 is attached to the side member 240 by screwing it into the opening 243 while forming a female thread. The arrangement position and number of the protrusions 230a are not particularly limited. In addition, the method of connecting the end member 230 and the side member 240 may be other methods, such as welding, crimping, adhesion, or welding. A detailed description of the configuration of the side member 240 will be given later.

In addition, the end members 230 (231, 232) have the above-mentioned two openings 230b (231b, 232b) arranged between the three protrusions 230a (231a, 232a) lined up in the Y-axis direction at the center in the X-axis direction and at the end in the positive X-axis direction. In other words, the three protrusions 230a (231a, 232a) and the two openings 230b (231b, 232b) are arranged alternately in the Y-axis direction. The openings 230b (231b, 232b) are circular through-holes that penetrate the end members 230 (231, 232) in the Z-axis direction. At the end of the end member 230 (231, 232) in the negative X-axis direction, the above-mentioned two openings 230c (231c, 232c) are arranged between the three protrusions 230a (231a, 232a) arranged in the Y-axis direction. In other words, the three protrusions 230a (231a, 232a) and the two openings 230c (231c, 232c) are arranged alternately in the Y-axis direction. The openings 230c (231c, 232c) are circular through-holes that penetrate the end member 230 (231, 232) in the Z-axis direction.

The bus bar 250 is a flat member connected to the energy storage element 210. Specifically, the bus bar 250 is arranged in the negative Y-axis direction of the multiple energy storage elements 210, and is connected (joined) to the electrode terminals 210b of the multiple energy storage elements 210 and the bus bar unit 330. That is, the bus bar 250 connects the electrode terminals 210b of the multiple energy storage elements 210 to each other, and connects the electrode terminals 210b of the end energy storage elements 210 to the bus bar unit 330. In this embodiment, the bus bar 250 and the electrode terminals 210b of the energy storage elements 210 are connected (joined) by welding, but may be connected (joined) by bolt fastening or the like. The bus bar 250 is formed of, for example, a conductive member made of a metal such as aluminum, an aluminum alloy, copper, a copper alloy, or nickel, or a combination thereof, or a conductive member other than a metal. In this embodiment, the bus bar 250 connects two storage elements 210 in parallel to form four sets of storage element groups, and connects the four sets of storage element groups in series, but the bus bar 250 may also connect all eight storage elements 210 in series, or may have another configuration.

The busbar frame 251 is a flat rectangular insulating member that can electrically insulate the busbar 250 from other members and regulate the position of the busbar 250. The busbar frame 251 is formed of, for example, any electrically insulating resin material that can be used for the exterior body 100 described above. The busbar frame 251 is arranged in the negative Y-axis direction of the multiple storage elements 210 and is positioned relative to the multiple storage elements 210. The busbar 250 is also positioned on the busbar frame 251. As a result, the busbar 250 is positioned relative to the multiple storage elements 210 and joined to the electrode terminals 210b of the multiple storage elements 210.

[3. Description of the Configuration of Energy Storage Element 210]
Next, the configuration of the energy storage element 210 will be described in detail. Fig. 5 is an exploded perspective view showing each component of the energy storage element 210 according to the present embodiment. Specifically, Fig. 5 shows an exploded view of each part of the energy storage element 210 shown in Fig. 4 in a vertically placed (standing) state. Note that since all eight energy storage elements 210 (four energy storage elements 211 and four energy storage elements 212) have the same configuration, the configuration of one energy storage element 210 will be described below.

As shown in FIG. 5, the energy storage element 210 includes a container 210a, a pair of electrode terminals 210b (positive and negative), and a pair of gaskets 210c (positive and negative). The container 210a also contains a pair of gaskets 210d (positive and negative), a pair of collectors 210e (positive and negative), and an electrode body 210f. An electrolyte (non-aqueous electrolyte) is enclosed inside the container 210a, but is not shown. There is no particular limit to the type of electrolyte as long as it does not impair the performance of the energy storage element 210, and various electrolytes can be selected. In addition to the above components, a spacer disposed on the side or below the electrode body 210f, an insulating film that encases the electrode body 210f, or an insulating sheet that covers the outer surface of the container 210a may be disposed.

The container 210a is a rectangular parallelepiped (angular or box-shaped) case having a container body 210a1 with an opening and a container lid 210a2 that closes the opening of the container body 210a1. With this configuration, the container 210a is structured so that the inside can be sealed by welding the container body 210a1 and the container lid 210a2 together after the electrode body 210f and other components are housed inside the container body 210a1. The materials of the container body 210a1 and the container lid 210a2 are not particularly limited, but are preferably weldable metals such as stainless steel, aluminum, aluminum alloy, iron, and plated steel sheet.

The container body 210a1 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 210a, and has an opening on the negative Y-axis side. In other words, the container body 210a1 has a pair of rectangular, planar (flat) long sides on both sides in the Z-axis direction, a pair of rectangular, planar (flat) short sides on both sides in the X-axis direction, and a rectangular, planar (flat) bottom surface on the positive Y-axis side. The container lid 210a2 is a rectangular plate-like member that constitutes the lid of the container 210a, and is disposed extending in the X-axis direction on the negative Y-axis side of the container body 210a1.

The electrode body 210f is an electric storage element (power generation element) formed by stacking a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate is a positive electrode active material layer formed on a positive electrode base layer, which is a current collector foil made of a metal such as aluminum or an aluminum alloy. The negative electrode plate is a negative electrode active material layer formed on a negative electrode base layer, which is a current collector foil made of a metal such as copper or a copper alloy. As the active material used for the positive electrode active material layer and the negative electrode active material layer, any known material can be used as long as it can absorb and release lithium ions. In this embodiment, the electrode body 210f is a wound type (so-called vertically wound type) electrode body formed by winding the electrode plates (positive electrode plate and negative electrode plate) around a winding axis (a virtual axis parallel to the X-axis direction) extending in the X-axis direction.

Here, the electrode plates (positive and negative plates) of the electrode body 210f are stacked in the Z-axis direction, so the Z-axis direction is also called the stacking direction. In other words, the electrode body 210f is formed by stacking the electrode plates in the stacking direction. The electrode body 210f has a pair of flat parts 210f1 aligned in the Z-axis direction and a pair of curved parts 210f2 aligned in the Y-axis direction by winding the electrode plates, and the stacking direction is the stacking direction of the electrode plates in the flat part 210f1. The flat part 210f1 is a flat part that connects the ends of the pair of curved parts 210f2, and the curved part 210f2 is a part that is curved in a semicircular shape or the like so as to protrude in the Y-axis direction. The stacking direction can also be defined as the direction in which the flat surface of the flat part 210f1 faces, or the direction in which the pair of flat parts 210f1 face each other. For this reason, the multiple storage elements 211 arranged in the arrangement direction (Z-axis direction) can also be said to be arranged in the stacking direction, and the multiple storage elements 212 arranged in the arrangement direction (Z-axis direction) can also be said to be arranged in the stacking direction.

In addition, the electrode body 210f has positive and negative plates wound with a mutual shift in the X-axis direction, so that the positive and negative plates have portions (active material layer non-formed portions) at the ends in the shifted direction where the active material is not formed (coated) and the substrate layer is exposed. In other words, the electrode body 210f has connection portions 210f3 at both ends in the X-axis direction that protrude from the flat portion 210f1 and the curved portion 210f2 on both sides in the X-axis direction, and are connected to the current collector 210e by stacking the active material layer non-formed portions of the positive and negative plates.

The electrode body 210f may be of any type, such as a so-called horizontally wound electrode body formed by winding an electrode plate around a winding axis extending in the Y-axis direction, a laminated (stacked) electrode body formed by stacking multiple flat electrode plates, or a bellows-shaped electrode body in which the electrode plate is folded into a bellows shape. In the case of a horizontally wound electrode body, the flat parts are the curved parts and the flat parts other than the connection parts (tabs) with the current collector, and in the case of a laminated (stacked) and bellows-shaped electrode body, the flat parts are the flat parts other than the connection parts (tabs) with the current collector.

The electrode terminals 210b are terminals (positive and negative terminals) of the storage element 210, and are arranged on the container lid 210a2 so as to protrude in the negative Y-axis direction. The electrode terminals 210b are electrically connected to the positive and negative plates of the electrode body 210f via the current collector 210e. The electrode terminals 210b are formed of a conductive material such as a metal, such as aluminum, an aluminum alloy, copper, or a copper alloy.

The current collector 210e is a conductive member (positive electrode current collector and negative electrode current collector) electrically connected to the electrode terminal 210b and the connection portion 210f3 of the electrode body 210f. The current collector 210e is made of aluminum, an aluminum alloy, copper, a copper alloy, or the like. The gaskets 210c and 210d are flat, electrically insulating sealing members arranged between the container lid portion 210a2 and the electrode terminal 210b and between the current collector 210e and the container lid portion 210a2. The gaskets 210c and 210d are made of, for example, any electrically insulating resin material that can be used for the exterior body 100 described above.

[4. Description of the Configuration of Spacer 221]
Next, the configuration of the spacer 221 will be described in detail. Since all the spacers 221 included in the energy storage unit 200 have the same configuration, the following description will be given by illustrating one spacer 221. Fig. 6 is a perspective view showing the configuration of the spacer 221 according to this embodiment. Specifically, Fig. 6 shows an enlarged view of the spacer 221 shown in Fig. 4.

7 is an enlarged perspective view and a top view of the configuration of the concave wall portions 282 and 285 of the side wall portion 280a of the spacer 221 according to the present embodiment. Specifically, FIG. 7(a) is an enlarged perspective view of the configuration of the concave wall portions 282 and 285 of the side wall portion 280a surrounded by the dashed line indicated by VII in the spacer 221 shown in FIG. 6. FIG. 7(b) is an enlarged perspective view of the configuration of FIG. 7(a) seen from the opposite side (X-axis minus direction). FIG. 7(c) is a top view of the configuration of FIG. 7(a) seen from the Z-axis plus direction. FIG. 8 is an enlarged perspective view and a top view of the configuration of the flat wall portion 291 of the rear wall portion 290 of the spacer 221 according to the present embodiment. Specifically, FIG. 8(a) is an enlarged perspective view of the configuration of the flat wall portion 291 of the rear wall portion 290 surrounded by the dashed line indicated by VIII in the spacer 221 shown in FIG. 6. FIG. 8(b) is a top view of the configuration in FIG. 8(a) viewed from the positive direction of the Z axis.

As shown in these figures, the spacer 221 has a spacer body 260, a front wall portion 270, a pair of side walls 280 (280a and 280b), and a rear wall portion 290. The spacer body 260 is a flat, rectangular portion that constitutes the body of the spacer 221, and is disposed at a position facing the energy storage element 210 in the Z-axis direction (first direction). Specifically, the spacer body 260 faces the long side of the container 210a of the energy storage element 210, and is disposed between the long sides of the two energy storage elements 210. In this embodiment, the spacer body 260 has a plurality of ribs 261, 262, and 263 extending in the X-axis direction formed on the main surface 260a on both sides in the Z-axis direction, but ribs extending in the Y-axis direction may be formed, or ribs may not be formed.

The front wall portion 270 is a flat wall portion that protrudes from the edge of the spacer body 260 in the negative Y-axis direction on both sides of the Z-axis direction, faces the energy storage element 210 in the Y-axis direction, and is arranged extending in the X-axis direction. Specifically, the front wall portion 270 is arranged so as to cover approximately half of the surface of the container lid portion 210a2 of the energy storage element 210 in the negative Y-axis direction in the Z-axis direction for each energy storage element 210 arranged on both sides of the spacer 221 in the Z-axis direction. More specifically, the front wall portion 270 is arranged so as to cover approximately half of the portion of the energy storage element 210 in the negative Y-axis direction other than the gas exhaust valve and electrode terminal 210b of the container lid portion 210a2 in the Z-axis direction.

The pair of side walls 280 are plate-shaped walls that protrude from both ends of the spacer body 260 in the X-axis direction in both Z-axis directions, and are arranged to face the storage element 210 in the X-axis direction (second direction) and extend in the Y-axis direction (third direction intersecting the first and second directions). Specifically, the pair of side walls 280 are arranged to cover approximately half of the surfaces (short sides) on both sides of the X-axis direction of the container body 210a1 of the storage element 210 for each storage element 210 arranged on both sides of the spacer 221 in the Z-axis direction. Hereinafter, the side wall 280 on the positive side of the X-axis direction of the pair of side walls 280 is also referred to as side wall 280a, and the side wall 280 on the negative side of the X-axis direction is also referred to as side wall 280b.

Sidewall portion 280a has spacer convex portion 281 and concave wall portions 282 to 285. Sidewall portion 280b also has spacer convex portion 281 and concave wall portions 282 to 285, similar to sidewall portion 280a. In other words, sidewall portion 280b has a shape that is symmetrical to sidewall portion 280a with respect to the YZ plane that passes through the center of spacer body 260. For this reason, the configuration of sidewall portion 280a will be described in detail below, and the description of the configuration of sidewall portion 280b will be simplified or omitted.

The spacer protrusion 281 is a protrusion that protrudes in the positive direction of the X-axis. In other words, the spacer protrusion 281 protrudes toward the side member 240. Specifically, the spacer protrusion 281 is a rectangular column-shaped (in this embodiment, a square tube-shaped) protrusion that extends in the Z-axis direction and protrudes in the positive direction of the X-axis, and two spacer protrusions 281 are arranged at both ends of the side wall portion 280a in the Y-axis direction. In this embodiment, the two spacer protrusions 281 have the same amount of protrusion in the positive direction of the X-axis, and are arranged to protrude in the positive direction of the X-axis more than the concave wall portions 282 to 285. In the Y-axis direction, the spacer protrusion 281 in the negative direction of the Y-axis has a larger width than the spacer protrusion 281 in the positive direction of the Y-axis.

The concave wall portions 282 to 285 are disposed between two spacer protrusions 281, and are rectangular recesses recessed toward the positive or negative X-axis direction when viewed from the Z-axis direction. Specifically, the concave wall portions 282 and 283 are U-shaped (inverted C-shaped) recesses when viewed from the Z-axis direction, with the surface facing the negative X-axis recessed in a rectangular shape toward the positive X-axis direction, and are disposed extending in the Z-axis direction. The concave wall portions 282 and 283 can also be said to be bulging protrusions extending in the Z-axis direction protruding in a rectangular shape toward the positive X-axis direction when viewed from the Z-axis direction, since the surface facing the positive X-axis protrudes in the positive X-axis direction. In this embodiment, two concave wall portions 282 are disposed between two spacer protrusions 281, and two concave wall portions 283 are disposed between the two concave wall portions 282. These recessed wall portions 282 and 283 are equally recessed in the positive X-axis direction, protrude in the positive X-axis direction, and have the same width in the Y-axis direction.

The concave wall portions 284 and 285 are generally C-shaped recesses when viewed from the Z-axis direction, with the surface facing the positive X-axis direction recessed in a rectangular shape toward the negative X-axis direction, and are arranged to extend in the Z-axis direction. The concave wall portions 284 and 285 are also said to be bulging convex portions extending in the Z-axis direction, protruding in a rectangular shape toward the negative X-axis direction, as viewed from the Z-axis direction, because the surface facing the negative X-axis direction protrudes in the negative X-axis direction. In this embodiment, two concave wall portions 284 are arranged between each of the two spacer convex portions 281 and each of the two two concave wall portions 282, and one concave wall portion 284 is arranged between the two concave wall portions 283. Two concave wall portions 285 are arranged between each of the two concave wall portions 282 and each of the two two concave wall portions 283.

In other words, the five concave wall portions, the three concave wall portions 284 and the two concave wall portions 285, are arranged alternately in the Y-axis direction with the four concave wall portions, the two concave wall portions 282 and the two concave wall portions 283, between the two spacer protrusions 281. The concave wall portions 284 and 285 are equally recessed in the negative X-axis direction, are equally protruding in the negative X-axis direction, and are equally wide in the Y-axis direction. Note that the concave wall portions 284 and 285 are narrower in the Y-axis direction than the concave wall portions 282 and 283.

Here, the concave wall portions 283 and 284 are flat wall portions (recesses), whereas the concave wall portions 282 and 285 are provided with protrusions (protrusions 282b and 285b described below) and have a shape that is concave in the opposite direction to the protrusion direction of the protrusions. The configuration of these concave wall portions 282 and 285 will be described in detail below. Note that all of the concave wall portions 282 of the side wall portion 280 (280a and 280b) have the same configuration, so the following will describe in detail one concave wall portion 282. The same applies to the concave wall portion 285.

7, the concave wall portion 282 has a first wall portion 282a provided with a protrusion 282b, a second wall portion 282c, and a deformation portion 282d. The first wall portion 282a is a flat rectangular wall portion parallel to the YZ plane that is arranged protruding from the spacer main body 260 on both sides in the Z axis direction and faces the energy storage element 210 in the X axis direction (second direction). The protrusion 282b is a protruding portion that protrudes from the first wall portion 282a toward the energy storage element 210 in the X axis direction (second direction). In other words, the portion of the first wall portion 282a where the protrusion 282b is formed is connected to the spacer main body 260 and protrudes from the spacer main body 260 in the Z axis direction (first direction).

The protrusion 282b is a rib that protrudes in the negative X-axis direction from the center of the first wall portion 282a in the Y-axis direction, and is arranged extending in the Z-axis direction from the end of the first wall portion 282a to the main surface 260a of the spacer body 260. In this embodiment, the protrusion 282b has a shape in which the edge in the positive Z-axis direction is inclined in the negative Z-axis direction as it approaches the negative X-axis direction, so that the length in the Z-axis direction becomes shorter as it approaches the negative X-axis direction from the first wall portion 282a.

The position of the protrusion 282b is not particularly limited. For example, the protrusion 282b may be disposed at the end of the first wall portion 282a in the Y-axis direction, or at the end or center in the Z-axis direction. The shape and number of the protrusions 282b are also not particularly limited. The length in the Z-axis direction may be longer toward the negative X-axis direction, or the length in the Z-axis direction may be the same throughout the X-axis direction, or multiple protrusions 282b may be arranged side by side in the Y-axis or Z-axis directions. In this embodiment, the protrusions 282b are also arranged in the curved portion of the boundary between the first wall portion 282a and the spacer main body 260, but in order to make the protrusions 282b easier to crush, the protrusions 282b may not be arranged in the curved portion.

The second wall portion 282c, like the first wall portion 282a, is a flat, rectangular wall portion that is arranged to protrude from the spacer body 260 on both sides in the Z axis direction and is parallel to the YZ plane, facing the energy storage element 210 in the X axis direction. The second wall portion 282c is arranged in a position adjacent to the first wall portion 282a in the Y axis direction (third direction). Specifically, a pair of second wall portions 282c are arranged at positions sandwiching the first wall portion 282a in the Y axis direction (third direction).

Here, the first wall portion 282a is thinner in the X-axis direction (second direction) than the second wall portion 282c. Specifically, the surface of the first wall portion 282a opposite the protrusion 282b side is disposed closer to the protrusion 282b side than the second wall portion 282c. In other words, the first wall portion 282a and the second wall portion 282c are disposed at the same position in the X-axis direction on the surface in the negative X-axis direction, and the first wall portion 282a is disposed in the negative X-axis direction on the surface in the positive X-axis direction. In other words, the concave wall portion 282 has a shape in which the surface in the positive X-axis direction is concave in the negative X-axis direction at the position of the first wall portion 282a.

The deformation portion 282d is disposed between the first wall portion 282a and the second wall portion 282c, and is a portion that allows the first wall portion 282a to deform more significantly relative to the second wall portion 282c than other adjacent portions. A pair of deformation portions 282d is disposed between the first wall portion 282a and a pair of second wall portions 282c. In this embodiment, the deformation portion 282d is a through portion formed by penetrating the portion between the first wall portion 282a and the second wall portion 282c in the X-axis direction (second direction). Specifically, the deformation portion 282d is a long cutout (slit) extending in the Z-axis direction, in which the portion between the first wall portion 282a and the second wall portion 282c in the concave wall portion 282 is cut from the edge in the Z-axis positive direction toward the Z-axis negative direction. In this embodiment, the deformation portion 282d extends to the curved portion of the boundary between the first wall portion 282a and the spacer body 260, but it does not have to extend to that curved portion, and it may extend beyond that curved portion.

In addition, the deformation portion 282d is not limited to a notch (slit) and may be, for example, a through hole extending in the Z-axis direction, or a through portion such as a plurality of through holes aligned in the Z-axis direction. Alternatively, the deformation portion 282d may not be a through portion, but may be a thin portion that is thinner in the X-axis direction (second direction) than the first wall portion 282a and the second wall portion 282c. In this case, the deformation portion 282d may be a flat thin portion, or may be a bellows-shaped thin portion, etc. Furthermore, the deformation portion 282d may have both the through portion and the thin portion. In this way, it is sufficient that the deformation portion 282d has at least one of a through portion and a thin portion.

Next, the configuration of the concave wall portion 285 will be described in detail. The concave wall portion 285 has a first wall portion 285a provided with a protrusion 285b, a second wall portion 285c, and a deformation portion 285d. The first wall portion 285a is a flat, rectangular wall portion parallel to the YZ plane that is arranged protruding from the spacer body 260 on both sides in the Z axis direction and faces the storage element 210 in the X axis direction (second direction). The protrusion 285b is a protruding portion that protrudes from the first wall portion 285a toward the opposite side to the storage element 210 in the X axis direction (second direction). In other words, the portion of the first wall portion 285a where the protrusion 285b is formed is connected to the spacer body 260 and protrudes from the spacer body 260 in the Z axis direction (first direction).

The protrusion 285b is a rib that protrudes in the positive X-axis direction from the center of the first wall portion 285a in the Y-axis direction, and is arranged to extend in the Z-axis direction. In this embodiment, the protrusion 285b is a trapezoidal protrusion when viewed from the X-axis direction, whose length in the Z-axis direction decreases as it moves from the first wall portion 285a in the positive X-axis direction, and two protrusions 285b are arranged side by side in the Z-axis direction. Note that the two protrusions 285b may be formed as a single protrusion by being extended in the Z-axis direction and connected. Furthermore, the arrangement position, shape, and number of the protrusions 285b are not particularly limited, and various modifications similar to those of the protrusion 282b described above are possible.

The second wall portion 285c is a flat rectangular wall portion parallel to the YZ plane, arranged adjacent to the first wall portion 285a in the Y-axis direction (third direction), similar to the above-mentioned second wall portion 282c. Specifically, a pair of second wall portions 285c are arranged at positions sandwiching the first wall portion 285a in the Y-axis direction (third direction). The first wall portion 285a and the second wall portion 285c have the same thickness in the X-axis direction (second direction).

The deformation portion 285d is disposed between the first wall portion 285a and the second wall portion 285c, and is a portion that allows the first wall portion 285a to deform more with respect to the second wall portion 285c than other adjacent portions. A pair of deformation portions 285d is disposed between the first wall portion 285a and a pair of second wall portions 285c. In this embodiment, the deformation portion 285d is a through portion (notch) formed by penetrating the portion between the first wall portion 285a and the second wall portion 285c in the X-axis direction (second direction), but various deformations (through holes, thin portions, etc.) similar to those of the above-mentioned deformation portion 282d are possible.

6 and 8, the rear wall portion 290 is a flat wall portion that protrudes from the edge of the spacer body 260 in the positive Y-axis direction on both sides in the Z-axis direction, faces the energy storage element 210 in the Y-axis direction, and is arranged extending in the X-axis direction. Specifically, the rear wall portion 290 is arranged so as to cover approximately half of the surface (bottom surface) in the positive Y-axis direction of the container body 210a1 of the energy storage element 210 in the Z-axis direction for each of the energy storage elements 210 arranged on both sides of the spacer 221 in the Z-axis direction.

The rear wall 290 has two flat wall portions 291 at both ends in the X-axis direction. The flat wall portion 291 is a flat wall portion, not a recessed or protruding wall portion like the concave wall portion 282. The rear wall portion 290 has a first wall portion 291a provided with a protrusion 291b, a second wall portion 291c, and a deformation portion 291d. The first wall portion 291a is a flat rectangular wall portion parallel to the XZ plane that is arranged protruding from the spacer main body 260 on both sides in the Z-axis direction and faces the storage element 210 in the Y-axis direction. The protrusion 291b is a protruding portion that protrudes from the first wall portion 291a toward the storage element 210 in the Y-axis direction. In other words, the portion of the first wall portion 291a where the protrusion 291b is formed is connected to the spacer main body 260 and protrudes from the spacer main body 260 in the Z-axis direction.

The protrusion 291b is a rib that protrudes in the negative Y-axis direction from both ends of the first wall portion 291a in the X-axis direction, and is arranged to extend in the Z-axis direction. Note that the protrusion 291b has a similar configuration to the protrusion 282b described above, so a detailed description will be omitted. The second wall portion 291c is a flat, rectangular wall portion parallel to the XZ plane, arranged at a position adjacent to the first wall portion 291a in the X-axis direction. A pair of second wall portions 291c are arranged at positions sandwiching the first wall portion 291a in the X-axis direction. The second wall portion 291c also has a similar configuration to the second wall portion 282c described above, so a detailed description will be omitted. The deformation portion 291d is arranged between the first wall portion 291a and the second wall portion 291c, and is a portion that enables a larger deformation of the first wall portion 291a relative to the second wall portion 291c than other adjacent portions. A pair of deformation portions 291d are disposed between the first wall portion 291a and the pair of second wall portions 291c. The deformation portions 291d have the same configuration as the deformation portion 282d described above, and therefore a detailed description thereof will be omitted.

The configuration of the spacer 221 has been described above, but the spacer 222 has the same configuration as the spacer 221. In other words, all the spacers 222 have walls with the same configuration as the front wall 270, the pair of side wall portions 280 (280a and 280b), and half of the rear wall portion 290 in the Z-axis direction of the spacer 221.

[5. Description of the Configuration of Side Member 240]
Next, the configuration of the side member 240 will be described in detail. Since all of the side members 240 of the energy storage unit 200 have the same configuration, the following description will be given by illustrating one side member 240. Fig. 9 is a perspective view showing the configuration of the side member 240 according to the present embodiment. Specifically, Fig. 9 shows an enlarged view of the side member 240 shown in Fig. 4.

As shown in FIG. 9, the side member 240 has a side protrusion 241 in which the above-mentioned openings 243 and 244 are formed, and a side recess 242. In this embodiment, five side protrusions 241 and four side recesses 242 are arranged alternately in the Y-axis direction.

The side protrusion 241 is a protruding portion of the side member 240 that protrudes in the X-axis direction and extends in the Z-axis direction. In this embodiment, the side protrusion 241 is a rectangular columnar (rectangular parallelepiped) portion that protrudes in a rectangular shape on both sides of the side member 240 in the X-axis direction and extends from one end to the other end of the side member 240 in the Z-axis direction. Here, the side protrusion 241 in which the opening 243 is formed is called the side protrusion 241a, and the side protrusion 241 in which the opening 244 is formed is called the side protrusion 241b. In other words, three side protrusions 241a and two side protrusions 241b are arranged alternately in the Y-axis direction. Two openings 243 extending in the Z-axis direction are formed at both ends of the side protrusion 241a in the Z-axis direction, and two openings 244 extending in the Z-axis direction are formed at both ends of the side protrusion 241b in the Z-axis direction.

As described above, the side protrusion 241a is fixed to the pair of end members 230 in the Z-axis direction by inserting the protrusions 230a (231a, 232a) of the pair of end members 230 (231, 232) into the openings 243 on both sides in the Z-axis direction. The side protrusion 241b is fixed to the exterior body 100 in the Z-axis direction by inserting the protrusion 113 of the exterior body main body 110 of the exterior body 100 into the opening 244 in the negative Z-axis direction. Note that for the side member 240 on the negative X-axis side, the side protrusion 241b is fixed to the electric equipment unit 300 in the Z-axis direction by inserting the protrusion 321 of the mounting member 320 of the electric equipment unit 300 into the openings 244 on both sides in the Z-axis direction.

The side recess 242 is a portion of the side member 240 that is recessed in the X-axis direction and extends in the Z-axis direction, and is disposed adjacent to the side protrusions 241 (241a, 241b). In this embodiment, the side recess 242 is a flat, rectangular (cuboid-shaped) portion that is recessed in a rectangular shape from both sides of the side member 240 in the X-axis direction and extends from one end of the side member 240 in the Z-axis direction to the other end.

[6. Description of Positional Relationship between Spacer 221, Energy Storage Element 210, and Side Member 240]
Next, the positional relationship between the spacer 221, the energy storage element 210, and the side member 240 will be described in detail. Fig. 10 is a top view showing the positional relationship between the spacer 221, the energy storage element 210, and the side member 240 according to this embodiment. Specifically, Fig. 10(a) shows the configuration when the spacer 221, the energy storage element 210, and the side member 240 are assembled, as viewed from the positive direction of the Z axis. Fig. 10(b) shows an enlarged view of the recessed wall portions 282 and 285 of the side wall portion 280a of the spacer 221 in Fig. 10(a) and the configuration around them.

As shown in FIG. 10, the side wall portions 280 (280a and 280b) of the spacer 221 are disposed on both sides of the energy storage element 210 in the X-axis direction, and the rear wall portion 290 is disposed in the positive Y-axis direction of the energy storage element 210. The side members 240 are disposed on both sides of the side wall portions 280 (280a and 280b) in the X-axis direction. In other words, the side wall portions 280 (280a and 280b) are disposed between the energy storage element 210 and the side members 240, and are disposed in a state where they are sandwiched between the energy storage element 210 and the side members 240.

The spacer protrusions 281 of the side wall 280 are disposed outside the end of the side member 240 in the Y-axis direction and protrude toward the side member 240. The two recessed wall portions 282 and the two recessed wall portions 283 are inserted into the four side recesses 242 of the side member 240, respectively. The five side protrusions 241 of the side member 240 are inserted into the three recessed wall portions 284 and the two recessed wall portions 285, respectively. Specifically, the three side protrusions 241a are inserted into the three recessed wall portions 284, and the two side protrusions 241b are inserted into the two recessed wall portions 285.

Then, the protrusion 282b of the concave wall portion 282 abuts against the energy storage element 210, and the protrusion 285b of the concave wall portion 285 abuts against the side convex portion 241b of the side member 240. In this embodiment, since all the spacers 220 (all the spacers 221 and all the spacers 222) have the same configuration as described above, the protrusion 285b of all the spacers 220 abuts against the side convex portion 241b of the side member 240. The protrusion 291b (not shown in FIG. 10) of the flat wall portion 291 of the rear wall portion 290 abuts against the energy storage element 210. Note that the protrusion 282b protrudes in the negative X-axis direction from the concave wall portion 285 so that it can abut against the energy storage element 210. Since the protrusion 285b only needs to come into contact with the side convex portion 241b, it protrudes less than the protrusion 282b and does not protrude in the positive direction of the X-axis beyond the concave wall portion 282. In addition, the distance (gap) between the first wall portion 282a and the side concave portion 242 is greater than the distance between the second wall portion 282c and the side concave portion 242.

The energy storage device 10 also includes two sets of energy storage elements 210 and spacers 221 at positions sandwiching the side member 240 in the X-axis direction. That is, the side member 240 is disposed between the side wall portion 280a of the spacer 221 disposed in the Z-axis direction of the energy storage element 211 and the side wall portion 280b of the spacer 221 disposed in the Z-axis direction of the energy storage element 212. The portion of the side member 240 on the negative X-axis direction side and the side wall portion 280a have the above-mentioned configuration, and the portion of the side member 240 on the positive X-axis direction side and the side wall portion 280b have the above-mentioned configuration.

[7. Description of Effects]
As described above, according to the energy storage device 10 according to the embodiment of the present invention, the spacer 221 has a protrusion 282b protruding in the second direction from the first wall portion 282a facing the energy storage element 210 in the second direction (X-axis direction). Furthermore, the spacer 221 has a deformation portion 282d between the first wall portion 282a and the second wall portion 282c adjacent to each other in the third direction (Y-axis direction) that allows the first wall portion 282a to be largely deformed relative to the second wall portion 282c. Similarly, the spacer 221 has a protrusion 285b protruding in the second direction from the first wall portion 285a facing the energy storage element 210 in the second direction (X-axis direction). Furthermore, the spacer 221 has a deformation portion 285d between the first wall portion 285a and the second wall portion 285c adjacent to each other in the third direction (Y-axis direction) that allows the first wall portion 285a to be largely deformed relative to the second wall portion 285c.

In this way, the spacer 221 has a protrusion 282b protruding from the first wall portion 282a toward the energy storage element 210, and a protrusion 285b protruding in the opposite direction from the energy storage element 210 (toward the side member 240). Therefore, even if a gap (wobble) occurs between the first wall portion 282a and the energy storage element 210, or between the first wall portion 285a and the member (side member 240) opposite the energy storage element 210, the protrusion 282b or 285b can fill the gap. As a result, even if the energy storage device 10 is subjected to vibration or impact, the energy storage element 210 and the like can be prevented from moving within the energy storage device 10, and therefore damage to the internal members of the energy storage device 10 can be prevented. The same can be said about the flat wall portion 291.

In addition, when the spacer 221 is provided with the protrusion 282b, if the gap between the first wall portion 282a and the energy storage element 210 is small or the protrusion 282b is hard, the protrusion 282b may not be crushed sufficiently, and the spacer 221 or the energy storage element 210 may be damaged. Similarly, for the protrusion 285b, if the gap between the first wall portion 285a and the member (side member 240) on the opposite side of the energy storage element 210 is small or the protrusion 285b is hard, the protrusion 285b may not be crushed sufficiently, and the spacer 221 or the member may be damaged. For this reason, the deformation portions 282d, 285d that enable the deformation of the first wall portions 282a, 285a are disposed between the first wall portions 282a, 285a on which the protrusions 282b, 285b are provided and the second wall portions 282c, 285c. As a result, if the protrusions 282b, 285b are not sufficiently crushed, the first wall portions 282a, 285a are deformed relative to the second wall portions 282c, 285c by the deformation portions 282d, 285d, and damage to the spacer 221, the energy storage element 210, or other related members can be suppressed. Therefore, damage to members inside the energy storage device 10 can be suppressed. The same can be said for the flat wall portion 291.

In addition, the portion of the first wall portion 282a where the protrusion 282b is formed is connected to the spacer body 260 and protrudes from the spacer body 260, so that the portion can be prevented from deforming relative to the second wall portion 282c more than when the portion is not connected to the spacer body 260. This can prevent the portion from deforming too much relative to the second wall portion 282c, causing damage to the spacer 221 or creating a gap between the spacer 221 and the energy storage element 210. Similarly, the protrusion 285b can prevent the spacer 221 from being damaged or creating a gap between the spacer 221 and the member (side member 240) on the opposite side to the energy storage element 210. Therefore, damage to the internal members of the energy storage device 10 can be prevented. The same can be said for the flat wall portion 291.

In addition, the deforming portion 282d can be easily formed by configuring it to have at least one of a through portion that penetrates the area between the first wall portion 282a and the second wall portion 282c, and a thin portion that is thinner than the first wall portion 282a and the second wall portion 282c. This makes it easy to prevent damage to the internal members of the energy storage device 10. The same can be said about the deforming portion 285d. The same can be said about the flat wall portion 291.

In addition, since the spacer 221 has a pair of deformation portions 282d between the first wall portion 282a and the pair of second wall portions 282c, the first wall portion 282a can be easily deformed relative to the second wall portions 282c, and the deformation can be balanced. This can further prevent damage to the internal members of the energy storage device 10. The same can be said about the deformation portions 285d. The same can be said about the flat wall portions 291.

In addition, because the first wall portion 282a is thinner than the second wall portion 282c, even if the protrusion 282b is provided on the first wall portion 282a, the first wall portion 282a can be prevented from protruding on the side opposite the protrusion 282b. This makes it possible to save space even in a configuration in which the first wall portion 282a deforms relative to the second wall portion 282c to prevent damage to the internal components of the energy storage device 10. The same can be said for the flat wall portion 291.

The first wall portion 282a is arranged such that the surface opposite the protrusion 282b (e.g., the outer surface) is closer to the protrusion 282b (e.g., the inner surface) than the second wall portion 282c. Therefore, even if the first wall portion 282a deforms relative to the second wall portion 282c, the first wall portion 282a can be prevented from protruding toward the opposite side to the protrusion 282b (e.g., the outer side). This makes it possible to save space even with a configuration in which the first wall portion 282a deforms relative to the second wall portion 282c to prevent damage to the internal components of the energy storage device 10. The same can be said for the flat wall portion 291.

In addition, since the protrusion 285b protrudes toward the opposite side of the energy storage element 210, even if a gap (wobble) occurs between the first wall portion 285a and the member (side member 240) on the opposite side of the energy storage element 210, the protrusion 285b can fill the gap. This makes it possible to suppress the movement of the energy storage element 210 and the like within the energy storage device 10 even if the energy storage device 10 is subjected to vibration or impact. In addition, even if the protrusion 285b is pressed against the member (side member 240), the deformation portion 285d deforms the first wall portion 285a relative to the second wall portion 285c, thereby suppressing damage to the spacer 221 or the member. Therefore, damage to the internal members of the energy storage device 10 can be suppressed.

In addition, the spacer 221 has protrusions 282b, 285b protruding in the second direction from a side wall portion 280 that faces the energy storage element 210 in the second direction (X-axis direction) and extends in the third direction (Y-axis direction). Furthermore, the side wall portion 280 of the spacer 221 has the protrusions 282b, 285b provided thereon and has concave wall portions 282, 285 that are concave in the opposite direction to the protrusion direction of the protrusions 282b, 285b. In this way, when the spacer 221 is provided with the protrusions 282b, 285b, if the protrusion length of the protrusions 282b, 285b is short, the protrusions 282b, 285b may not be sufficiently crushed, and the spacer 221, the energy storage element 210, or the above-mentioned member (side member 240), etc. may be damaged. For this reason, the side wall portion 280 of the spacer 221 is provided with concave wall portions 282, 285 that are concave in the direction opposite to the protrusion direction of the protrusions 282b, 285b, and the concave wall portions 282, 285 are provided with the protrusions 282b, 285b. This allows the protrusion length of the protrusions 282b, 285b to be increased, so that the protrusions 282b, 285b are prevented from being sufficiently crushed, thereby preventing damage to the spacer 221, the energy storage element 210, or the above-mentioned components. Therefore, damage to the internal components of the energy storage device 10 can be prevented.

In addition, in the concave wall portion 282, the first wall portion 282a is thinner than the second wall portion 282c, so that even if the first wall portion 282a has a protrusion 282b, the first wall portion 282a can be prevented from protruding on the side opposite the protrusion 282b. As a result, even in a configuration in which the concave wall portion 282 is provided on the side wall portion 280 of the spacer 221 to prevent damage to the internal components of the energy storage device 10, the concave wall portion 282 can be prevented from protruding on the side opposite the protrusion 282b, thereby enabling space saving.

In addition, in the concave wall portion 282, the first wall portion 282a on which the protrusion 282b is provided has a surface (e.g., outer surface) opposite the protrusion 282b side arranged closer to the protrusion 282b side (e.g., inner side) than the second wall portion 282c. Therefore, even if the first wall portion 282a is deformed opposite the protrusion 282b (e.g., outer side), the first wall portion 282a can be prevented from protruding on the side opposite the protrusion 282b. As a result, even in a configuration in which the concave wall portion 282 is provided on the side wall portion 280 of the spacer 221 to prevent damage to the internal members of the storage device 10, the concave wall portion 282 can be prevented from protruding on the side opposite the protrusion 282b, thereby saving space.

The side member 240 facing the spacer 221 has a side recess 242 into which the recessed wall portions 282, 283 of the spacer 221 are inserted, and a side protrusion 241 into which the recessed wall portions 284, 285 are inserted. Therefore, the spacer 221 can be positioned relative to the side member 240 by utilizing the recessed wall portions 282, 283, 284, or 285. This makes it possible to prevent the spacer 221 and the energy storage element 210, etc. from moving within the energy storage device 10 even if the energy storage device 10 is subjected to vibration or impact, thereby preventing damage to the internal components of the energy storage device 10.

[8. Description of Modifications]
Although the power storage device 10 according to the embodiment of the present invention (including its modified examples) has been described above, the present invention is not limited to this embodiment. In other words, the embodiment disclosed here is illustrative and not restrictive in all respects, and the scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

For example, in the above embodiment, a plurality of spacers 220 are arranged, but only one spacer 220 may be arranged. In other words, only one spacer 221 may be arranged, only one spacer 222 may be arranged, or a configuration in which either spacer 221 or spacer 222 is not arranged may be used. Even if spacer 221 is not arranged, spacer 222 can perform the same function as spacer 221 by having a wall portion and the like similar to that of spacer 221 described above.

In the above embodiment, the spacer 221 has a pair of second walls 282c sandwiching the first wall 282a, and has a pair of deformation portions 282d between the first wall 282a and the pair of second walls 282c. However, the spacer 221 may have the second wall 282c only on one side of the first wall 282a, and may have only one deformation portion 282d between the first wall 282a and the second wall 282c. The same applies to the concave wall 285 and the flat wall 291.

In the above embodiment, the first wall portion 282a of the concave wall portion 282 of the side wall portion 280 of the spacer 221 is thinner than the second wall portion 282c. However, the first wall portion 282a may be the same thickness as the second wall portion 282c, or the second wall portion 282c may be thicker.

In the above embodiment, the concave wall portion 282 of the side wall portion 280 of the spacer 221 is arranged such that the surface of the first wall portion 282a facing the protrusion 282b is closer to the protrusion 282b side than the second wall portion 282c. However, the surface of the first wall portion 282a facing the protrusion 282b side than the second wall portion 282c may be arranged on the opposite side to the protrusion 282b side.

In the above embodiment, the concave wall portion 285 of the side wall portion 280 of the spacer 221 has the first wall portion 285a having the same thickness as the second wall portion 285c. However, the first wall portion 285a may be thinner or thicker than the second wall portion 285c. Also, the surface of the first wall portion 285a opposite the protrusion 285b side from the second wall portion 285c may be disposed closer to the protrusion 285b side, or the surface of the first wall portion 285a opposite the protrusion 285b side from the second wall portion 285c may be disposed closer to the protrusion 285b side. The same applies to the flat wall portion 291.

In the above embodiment, the flat wall portion 291 is a flat wall portion, but it may be a concave wall portion, similar to the concave wall portions 282, 285, etc. Alternatively, the concave wall portions such as the concave wall portions 282, 285, etc. may be flat walls rather than concave.

In the above embodiment, the concave wall portions 284 and 285 have the same shape, and the width between the pair of walls facing each other in the Y-axis direction in the recess is the same. However, the width between the pair of walls of the concave wall portions 284 and 285 may be different. For example, the width between the pair of walls of the concave wall portions 284 and 285 may be gradually increased or decreased from the concave wall portion at the end in the negative Y-axis direction to the concave wall portion at the end in the positive Y-axis direction. This allows a gap to be formed between the concave wall portions 284 and 285 and the side protrusion portion 241 of the side member 240, so that positional deviations due to dimensional tolerances during manufacturing can be absorbed.

In the above embodiment, the side member 240 has side protrusions 241 that protrude on both sides in the X-axis direction. However, the side protrusions 241 may protrude only on one side in the X-axis direction, and the side member 240 may be a flat member that does not have a side protrusion 241. In other words, the side member 240 does not have to have at least one of the side recesses 242 into which the recessed wall portions 282, 283 of the spacer 221 are inserted, and the side protrusions 241 that are inserted into the recessed wall portions 284, 285.

In the above embodiment, the energy storage unit 200 has two energy storage elements 210 (211 and 212) arranged in the X-axis direction. However, the energy storage unit 200 may have three or more energy storage elements 210 arranged in the X-axis direction, or may have only one energy storage element 210 in the X-axis direction.

In the above embodiment, any of the plurality of spacers 221 may not have the above configuration, any of the plurality of side members 240 may not have the above configuration, and any of the plurality of storage elements 210 may not have the above configuration.

In the above embodiment, the energy storage device 10 does not need to include all of the components described above. For example, the energy storage device 10 does not need to include components (members or parts) that do not contribute to the above-mentioned effects or that can achieve the above-mentioned effects without them.

Any combination of the components included in the above embodiment and its variations is also within the scope of the present invention.

The present invention can be realized not only as an energy storage device 10, but also as a spacer 220.

The present invention can be applied to a storage device equipped with a storage element such as a lithium-ion secondary battery.

REFERENCE SIGNS LIST 10 Energy storage device 100 Exterior body 112, 280, 280a, 280b Side wall portion 130 External terminal 200 Energy storage unit 210, 211, 212 Energy storage element 210a Container 210b Electrode terminal 210e Current collector 210f Electrode body 220, 221, 222 Spacer 230, 231, 232 End member 240 Side member 241, 241a, 241b Side protrusion 242 Side recess 250 Bus bar 260 Spacer body 270 Front wall portion 281 Spacer protrusion 282, 283, 284, 285 Recessed wall portion 282a, 285a, 291a First wall portion 282b, 285b, 291b Protrusion 282c, 285c, 291c Second wall portion 282d, 285d, 291d Deformed portion 290 Rear wall portion 291 Flat wall portion 300 Electrical equipment unit

Claims (6)

An electricity storage device including electricity storage elements and spacers arranged side by side in a first direction,
The spacer is
a first wall portion facing the energy storage element in a second direction intersecting the first direction;
a protrusion protruding from the first wall portion in the second direction;
a second wall portion disposed adjacent to the first wall portion in a third direction intersecting the first direction and the second direction;
a deformation portion disposed between the first wall portion and the second wall portion, the deformation portion enabling a larger deformation of the first wall portion relative to the second wall portion than other adjacent portions ,
The first wall portion has a thickness in the second direction that is smaller than that of the second wall portion.
Energy storage device. An electricity storage device including electricity storage elements and spacers arranged side by side in a first direction,
The spacer is
a first wall portion facing the energy storage element in a second direction intersecting the first direction;
a protrusion protruding from the first wall portion in the second direction;
a second wall portion disposed adjacent to the first wall portion in a third direction intersecting the first direction and the second direction;
a deformation portion disposed between the first wall portion and the second wall portion, the deformation portion enabling a larger deformation of the first wall portion relative to the second wall portion than other adjacent portions ,
The first wall portion has a surface on the opposite side to the protrusion side from the second wall portion and is disposed on the protrusion side.
Energy storage device. An electricity storage device including electricity storage elements and spacers arranged side by side in a first direction,
The spacer is
a first wall portion facing the energy storage element in a second direction intersecting the first direction;
a protrusion protruding from the first wall portion in the second direction;
a second wall portion disposed adjacent to the first wall portion in a third direction intersecting the first direction and the second direction;
a deformation portion disposed between the first wall portion and the second wall portion, the deformation portion enabling a larger deformation of the first wall portion relative to the second wall portion than other adjacent portions ,
The deformation portion has a thin portion that is thinner in the second direction than the first wall portion and the second wall portion.
Energy storage device. An electricity storage device including electricity storage elements and spacers arranged side by side in a first direction,
The spacer is
a first wall portion facing the energy storage element in a second direction intersecting the first direction;
a protrusion protruding from the first wall portion in the second direction;
a second wall portion disposed adjacent to the first wall portion in a third direction intersecting the first direction and the second direction;
a deformation portion disposed between the first wall portion and the second wall portion, the deformation portion enabling a larger deformation of the first wall portion relative to the second wall portion than other adjacent portions ,
The protrusion protrudes from the first wall portion toward a side opposite to the energy storage element in the second direction.
Energy storage device. The spacer further comprises:
a spacer body facing the energy storage element in the first direction;
The power storage device according to claim 1 , wherein a portion of the first wall portion where the protrusion is formed is connected to the spacer body and protrudes from the spacer body in the first direction. The spacer is
A pair of the second walls arranged at positions sandwiching the first wall in the third direction;
The power storage device according to claim 1 , further comprising: a pair of the deformation portions disposed between the first wall portion and the pair of second wall portions.

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