Energy storage device

Abstract

In an external casing where the battery case and lid are joined by heat welding, the present invention provides a reliable energy storage device that suppresses damage to the joint when the internal pressure of the casing increases. [Solution] The energy storage device comprises an energy storage element and an outer casing 10 that houses the energy storage element. The outer casing comprises a first outer casing 12 having an opening on one side in the first direction, a second outer casing 20 that closes the opening, a joint 90 that joins the opening end face, which is the end face of the opening, and the second outer casing by welding or adhesive, and a shaft member 100 that extends in the first direction and penetrates the joint. The first outer casing has a first shaft hole 110 provided on the opening end face, and the second outer casing has a second shaft hole 120 facing the first shaft hole in the first direction. The shaft member is inserted into the first shaft hole and the second shaft hole.

Description

Technical Field

[0001] The present invention relates to a power storage device.

Background Art

[0002] Patent Document 1 discloses a battery including a lead battery case that is an exterior case and a lead battery lid that closes an upper opening of the lead battery case. The lead battery case internally partitions with a battery partition wall, provides an auxiliary battery storage chamber inside the lead battery case, and stores an auxiliary battery in this auxiliary battery storage chamber. The lead battery lid is thermally welded to the outer peripheral wall of the lead battery case and the upper edge of the battery partition wall, closing the upper openings of the cell chamber and the auxiliary battery storage chamber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional battery described above, the lead battery case and the lead battery lid are joined by thermal welding. Thus, when there is a joined portion where two members are joined to the exterior case, for example, when the internal pressure of the exterior case rises, stress may concentrate on the joined portion, resulting in damage to the joined portion. Damage to the joined portion of the exterior case becomes a factor such as a decrease in the airtightness of the exterior case.

[0005] [[ID=ID=39]]The present invention has been newly made by the inventors of the present application paying attention to the above problems, and an object thereof is to provide a power storage device with improved reliability.

Means for Solving the Problems

[0006] An energy storage device according to one aspect of the present invention comprises an energy storage element and an outer casing housing the energy storage element, wherein the outer casing comprises a first outer casing having an opening on one side in a first direction, a second outer casing closing the opening, a joint that joins the opening end face, which is the end face of the opening, and the second outer casing by welding or adhesive, and a shaft member extending in the first direction and penetrating the joint, wherein the first outer casing has a first shaft hole provided in the opening end face, and the second outer casing has a second shaft hole facing the first shaft hole in the first direction, and the shaft member is inserted into the first shaft hole and the second shaft hole.

[0007] Another embodiment of the present invention provides a power storage device comprising a power storage element and an outer casing housing the power storage element, wherein the outer casing comprises a first outer casing having an opening on one side in a first direction, a second outer casing closing the opening, a joint that joins the opening end face, which is the end face of the opening, and the second outer casing by welding, and a shaft member extending in the first direction and penetrating the joint, wherein the first outer casing has a first shaft hole provided in the opening end face, and the second outer casing has a second shaft hole facing the first shaft hole in the first direction, and the shaft member is inserted into the first shaft hole and the second shaft hole. [Effects of the Invention]

[0008] According to the present invention, an energy storage device with improved reliability can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view showing the external appearance of an energy storage device according to an embodiment. [Figure 2] Figure 2 is an exploded perspective view of the energy storage device according to the embodiment. [Figure 3] Figure 3 is an exploded perspective view showing the shaft member and its surrounding components according to an embodiment. [Figure 4] Figure 4 is a cross-sectional view showing the configuration of the shaft member and its surrounding area according to the embodiment. [Figure 5] Figure 5 is an enlarged cross-sectional view showing a portion of the cross-sectional view shown in Figure 4. [Figure 6] Figure 6 is a perspective view showing a partial arrangement range of the joint according to the embodiment. [Figure 7] Figure 7 is a perspective view illustrating an example of a method for forming a joint according to the embodiment. [Figure 8] Figure 8 is a cross-sectional view showing the configuration of the shaft member and its surrounding area according to a modified example 1 of the embodiment. [Figure 9] Figure 9 is a cross-sectional view showing the configuration of the shaft member and its surrounding area according to a modified example 2 of the embodiment. [Figure 10] Figure 10 is a cross-sectional view showing the configuration of the shaft member and its surrounding area according to a modified example 2 of the embodiment. [Modes for carrying out the invention]

[0010] (1) An energy storage device according to one aspect of the present invention comprises an energy storage element and an outer casing housing the energy storage element, wherein the outer casing comprises a first outer casing having an opening on one side in a first direction, a second outer casing closing the opening, a joint that joins the opening end face, which is the end face of the opening, and the second outer casing by welding or adhesive, and a shaft member extending in the first direction and penetrating the joint, wherein the first outer casing has a first shaft hole provided in the opening end face, and the second outer casing has a second shaft hole facing the first shaft hole in the first direction, and the shaft member is inserted into the first shaft hole and the second shaft hole.

[0011] According to one aspect of the present invention, the interior of the outer casing can be sealed by joining the second outer casing and the open end face of the first outer casing at a joint. Furthermore, at the boundary between the second outer casing and the first outer casing, there is a shaft member that penetrates the joint and is inserted into the second outer casing and the first outer casing. Therefore, even if the outer casing deforms to bulge due to an increase in internal pressure, the increase in stress generated at the joint is suppressed, and as a result, damage to the joint is effectively suppressed. Accordingly, the energy storage device according to one aspect of the present invention is an energy storage device with improved reliability.

[0012] (2) In the power storage device described in (1) above, the opening may be provided with a thick-walled portion where the thickness of the opening end face is thicker than other portions, and the first shaft hole may be provided in the thick-walled portion.

[0013] According to the power storage device described in (2) above, the shaft member is more stably supported by the thick-walled portion and / or the thickness of the shaft member can be made larger. As a result, the joint portion is less likely to be damaged.

[0014] (3) In the power storage device described in (1) or (2) above, the exterior body may be made of resin and the shaft member may be made of metal.

[0015] According to the power storage device described in (3) above, problems such as a decrease in strength due to heat or vibration are less likely to occur in the shaft member. This contributes to an improvement in the reliability of the power storage device.

[0016] (4) In the power storage device described in any one of (1) to (3) above, the shaft member may be a threaded shaft portion that couples to at least one of the first shaft hole and the second shaft hole, and includes a threaded shaft portion provided with a thread on the outer periphery.

[0017] According to the power storage device described in (4) above, a bolt or a tapping screw or the like can be adopted as the shaft member. As a result, the coupling force between the shaft member and the first shaft hole and / or the second shaft hole is improved, and as a result, the strength of the joint portion is further improved.

[0018] (5) In the power storage device described in any one of (1) to (4) above, the first shaft hole may penetrate the first exterior body in the first direction, or the second shaft hole may penetrate the second exterior body in the first direction.

[0019] In the energy storage device described in (5) above, at least one of the first shaft hole and the second shaft hole opens to the outer surface of the casing. Therefore, after joining the second casing to the open end face, the shaft members can be inserted into the first shaft hole and the second shaft hole. In other words, the joining work between the second casing and the open end face can be performed without placing shaft members in either the second or first casing. Therefore, for example, it is easier to perform the joining work with greater precision.

[0020] (6) In the energy storage device described in any one of (1) to (5) above, the shaft member may not have a portion that is exposed to the outside of the outer casing.

[0021] According to the energy storage device described in (6) above, the shaft member does not have any portion exposed to the outside of the outer casing, so for example, damage or deterioration of the shaft member 100 is suppressed. As a result, the reliability of the shaft member is maintained or improved.

[0022] (7) Another embodiment of the present invention provides an energy storage device comprising an energy storage element and an outer casing housing the energy storage element, wherein the outer casing comprises a first outer casing having an opening on one side in a first direction, a second outer casing closing the opening, a joint that joins the opening end face, which is the end face of the opening, and the second outer casing by welding, and a shaft member extending in the first direction and penetrating the joint, wherein the first outer casing has a first shaft hole provided in the opening end face, and the second outer casing has a second shaft hole facing the first shaft hole in the first direction, and the shaft member is inserted into the first shaft hole and the second shaft hole.

[0023] In another aspect of the present invention, the opening end faces of the second outer casing and the first outer casing are joined by a welded joint, thereby sealing the inside of the outer casing. Furthermore, at the boundary between the second outer casing and the first outer casing, there is a shaft member that penetrates the joint and is inserted into both the second and first outer casings. Therefore, even if the outer casing deforms and bulges due to an increase in internal pressure, damage to the welded joint is effectively suppressed. Accordingly, the other aspect of the present invention provides an improved energy storage device.

[0024] The following description will explain an embodiment of the present invention (including its modifications) with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples and are not intended to limit the present invention. Furthermore, dimensions and other specifications are not strictly illustrated in each figure. In addition, the same or similar components are denoted by the same reference numerals in each figure.

[0025] In the following description and drawings, the direction in which a pair of terminals on one energy storage element are aligned, or the direction in which a pair of short sides on one energy storage element face each other, is defined as the X-axis direction. The direction in which multiple energy storage elements are aligned, the direction in which a pair of long sides on one energy storage element face each other, or the thickness direction of an energy storage element is defined as the Y-axis direction. The direction in which the container body and lid plate are aligned on the container of an energy storage element, the direction in which the first outer casing and the second outer casing are aligned on the outer casing, or the vertical direction is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect (orthogonal in this embodiment) with each other. Note that depending on the usage, the Z-axis direction may not be the vertical direction, but for the sake of explanation below, the Z-axis direction will be described as the vertical direction.

[0026] In the following explanation, the X-axis positive direction refers to the direction of the X-axis arrow, and the X-axis negative direction refers to the opposite direction. When simply referring to the X-axis direction, it refers to either the X-axis positive direction or the X-axis negative direction, or either direction. The same applies to the Y-axis and Z-axis directions. Expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where they are not strictly those directions or orientations. Two directions being parallel means not only that they are perfectly parallel, but also that they are substantially parallel, i.e., that they may have a difference of a few percent. Furthermore, in the following explanation, when "insulation" is used, it means "electrical insulation." Insulating materials have a volume resistivity of 1 × 10⁻⁶. 6Ωm or greater, more preferably 1 × 10⁻⁶ 7 Ωm or greater, more preferably 1 × 10⁻⁶ 10 It is preferable that the material is formed from a material with a density of Ωm or greater.

[0027] (Embodiment) [1. General description of the energy storage device 1] First, the configuration overview of the energy storage device 1 in this embodiment will be described. Figure 1 is a perspective view showing the external appearance of the energy storage device 1 according to this embodiment. Figure 2 is an exploded perspective view of the energy storage device 1 according to this embodiment. Inside the outer casing 10, in addition to the members shown in Figure 2, a plurality of busbars for connecting a plurality of energy storage elements 50 are housed, and further, a control device for monitoring and controlling the charging state of the plurality of energy storage elements 50, spacers arranged along the energy storage elements 50, and restraining members for restraining the plurality of energy storage elements 50 may be arranged. However, the illustration and description of these members will be omitted. In Figure 2, and in Figures 3, 4, and 6 which will be described later, only one shaft member 100 is shown, but the energy storage device 1 may have a plurality of shaft members 100.

[0028] The energy storage device 1 is a device that can charge electricity from an external source and discharge electricity to an external source. The energy storage device 1 is, for example, a battery module (battery pack) used for power storage or power supply purposes. Specifically, the energy storage device 1 is used as a battery for driving or starting the engine of mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, automated guided vehicles (AGVs), or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicles. Examples of railway vehicles for electric railways include electric trains, monorails, maglev trains, and hybrid trains equipped with both diesel engines and electric motors. The energy storage device 1 can also be used as a stationary battery for household or commercial use.

[0029] As shown in Figures 1 and 2, the energy storage device 1 comprises an outer casing 10, an energy storage unit 51 housed in the outer casing 10 and having one or more energy storage elements 50, and a shaft member 100. The outer casing 10 is a box-shaped (approximately rectangular parallelepiped) container (module case) that constitutes the housing of the energy storage device 1. A rectangular parallelepiped, in this context, is a hexahedron whose faces are all rectangles or squares. In other words, the outer casing 10 is positioned outside the energy storage unit 51 and protects the energy storage unit 51.

[0030] The outer casing 10 is formed from insulating materials 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), polyetheretherketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), polyamide (PA), ABS resin, or composite materials thereof. The outer casing 10 thereby prevents the energy storage element 50, etc., from coming into contact with external metal components.

[0031] The exterior body 10 comprises a first exterior body 12 and a second exterior body 20. The first exterior body 12 is a bottomed rectangular cylindrical housing having an opening 12a that forms an opening 13 in the Z-axis positive direction. In other words, the first exterior body 12 is the main body of the exterior body. Specifically, the first exterior body 12 comprises a pair of first side wall portions 17 facing each other in the Y-axis direction, a pair of first side wall portions 18 facing each other in the X-axis direction, and a bottom wall portion 19 facing the energy storage unit 51 in the Z-axis direction. The opening 12a is formed by the Z-axis positive ends of the pair of first side wall portions 17 and the pair of first side wall portions 18. That is, the opening 12a is provided at the Z-axis positive end of the first exterior body 12. In this embodiment, the opening end face 12b, which is the end face of the opening 12a, is joined to the second exterior body 20.

[0032] The second exterior body 20 is a member that closes the opening 12a of the first exterior body 12. In other words, the second exterior body 20 is a lid. More specifically, the second exterior body 20 is joined to the opening end face 12b and closes the opening 13 formed by the opening 12a. The second exterior body 20 according to this embodiment comprises a pair of second exterior body side wall portions 27 facing each other in the Y-axis direction, a pair of second side wall portions 28 facing each other in the X-axis direction, and an upper wall portion 29 facing the energy storage unit in the Z-axis direction. In this embodiment, the ends of the pair of second side wall portions 27 and the pair of second side wall portions 28 in the Z-axis negative direction are joined to the opening end face 12b of the first exterior body 12. The second exterior body 20 configured in this way has a pair of external terminals 70 for the positive and negative electrodes. Specifically, the external terminals 70 are located at both ends in the Y-axis direction of the X-axis positive end of the second exterior body 20.

[0033] The energy storage device 1 charges itself with electricity from the outside and discharges electricity to the outside through this pair of external terminals 70. The external terminals 70 are made of a conductive metal such as aluminum, aluminum alloy, copper, or copper alloy. When distinguishing between the pair of external terminals 70, the positive external terminal 70 is referred to as external terminal 70A, and the negative external terminal 70 is referred to as external terminal 70B.

[0034] After the energy storage unit 51 and the like are housed in the first outer casing 12, the second outer casing 20 is joined to the first outer casing 12. Specifically, the second outer casing 20 and the first outer casing 12 are joined by adhesive or welding. In other words, the energy storage device 1 according to this embodiment is equipped with a joint 90 that joins the second outer casing 20 and the first outer casing 12 by adhesive or welding. As a result, the boundary portion (i.e., the joint 90) between the second outer casing 20 and the first outer casing 12 is maintained in a state of high airtightness. Details of the joint 90 will be described later with reference to Figures 4 to 7.

[0035] The energy storage unit 51 comprises one or more energy storage elements 50. The energy storage unit 51 according to this embodiment comprises eight energy storage elements 50. The eight energy storage elements 50 are arranged in the Y-axis direction with their long side surface 52a facing the Y-axis direction. In other words, in this embodiment, a pair of first side wall portions 17 of the first outer casing 12 face the energy storage unit 51 in the direction in which the eight energy storage elements 50 are arranged.

[0036] The energy storage unit 51 may include spacers or holders (not shown) arranged along the energy storage elements 50. The energy storage unit 51 may also include busbar holders that hold busbars connected to the energy storage elements 50. The energy storage unit 51 may also include restraining members (not shown) that constrain a plurality of energy storage elements 50 in their alignment direction. The eight energy storage elements 50 in the energy storage unit 51 are connected, for example, in series by a plurality of busbars (not shown), but the electrical connection configuration is not limited thereto. There are no particular limitations on the number of energy storage elements 50 in the energy storage unit 51. The number of energy storage elements 50 in the energy storage unit 51 may be any of 1 to 7, or 9 or more.

[0037] The energy storage element 50 is a secondary battery, more specifically a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. As shown in Figure 2, the energy storage element 50 includes a flat rectangular parallelepiped (square) shaped container 52. Inside the container 52 are electrodes, a current collector, and an electrolyte (not shown). As the electrodes, for example, a wound type electrode formed by winding an electrode plate and a separator, a stacked type electrode formed by stacking multiple flat electrode plates, or a bellows type electrode formed by folding an electrode plate in a bellows shape may be used. More specifically, the electrodes of the energy storage element 50 include a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate is an electrode plate (electrode plate) on which a positive electrode active material layer is formed on the surface of a positive electrode current collector foil, which is a long strip of metal foil. The negative electrode plate is an electrode plate (electrode plate) on which a negative electrode active material layer is formed on the surface of a negative electrode current collector foil, which is a long strip of metal foil. As the positive electrode current collector foil and negative electrode current collector foil, any known material that is stable against oxidation-reduction reactions during charging and discharging can be used, such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, and Al-Cd alloy. As the positive electrode active material used in the positive electrode active material layer and the negative electrode active material used in the negative electrode active material layer, any known material that is capable of intercalating and releasing charge transport ions can be used. As for the electrolyte contained in the container 52, there are no particular restrictions on its type as long as it does not impair the performance of the energy storage element 50, and various types can be selected. The energy storage element 50 may be a secondary battery other than a non-aqueous electrolyte secondary battery, or it may be a capacitor. The energy storage element 50 may be a primary battery. The energy storage element 50 may be a pouch-type energy storage element. The energy storage element 50 may be a battery using a solid electrolyte. The shape of the energy storage element 50 is not limited to the above-mentioned rectangular shape, but may also be a polygonal prism, cylindrical shape, elliptical prism shape, oblong cylindrical shape, etc.

[0038] As shown in Figure 2, the container 52 is a rectangular parallelepiped case having a pair of long sides 52a, a pair of short sides 52b, a bottom surface 52d, and a terminal arrangement surface 52c. A pair of terminals 55 and a gas discharge valve 53 are provided on the terminal arrangement surface 52c. After housing electrodes and the like inside the container 52 (container body), the inside of the container 52 is sealed by welding the container body and the lid plate forming the terminal arrangement surface 52c. The material of the container 52 is not particularly limited, but it is preferably a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet. If the internal pressure of the container 52 rises excessively due to gas generation from the electrolyte inside the container 52, the gas is discharged from the gas discharge valve 53. In this embodiment, the outer casing 10 is equipped with, for example, an outlet (not shown) located on the second outer casing 20, and is configured to maintain airtightness except for the outlet. Therefore, when gas is discharged from the gas discharge valve 53 of the energy storage element 50, the gas is discharged to the outside of the outer casing 10 through the discharge port. This suppresses the occurrence of malfunctions such as damage to the outer casing 10 due to an excessive rise in internal pressure of the outer casing 10. Furthermore, if the internal pressure of the container 52 does not rise excessively, the outer casing 10 maintains its airtightness.

[0039] The terminals 55 are electrically connected to the electrode body housed in the container 52 and protrude from the terminal arrangement surface 52c. One of the pair of terminals 55 is electrically connected to the positive electrode of the electrode body, and the other is electrically connected to the negative electrode of the electrode body. The terminals 55 are formed of a conductive material such as aluminum, aluminum alloy, copper, or copper alloy. In this embodiment, the terminals 55 have a flat portion to which a conductive member such as a busbar is welded. The terminals 55 may also have a shaft portion for fixing an external conductive member such as a busbar using a nut.

[0040] In this embodiment, as described above, eight energy storage elements 50 are connected in series. Of the eight energy storage elements 50, the positive terminal 55 of the energy storage element 50 at the end in the positive direction of the Y-axis functions as the total positive terminal of the energy storage unit 51. Of the eight energy storage elements 50, the negative terminal 55 of the energy storage element 50 at the end in the negative direction of the Y-axis functions as the total negative terminal of the energy storage unit 51. The total positive terminal is electrically connected to the positive external terminal 70A via one or more busbars (not shown). The total negative terminal is electrically connected to the negative external terminal via one or more busbars (not shown). In other words, the energy storage unit 51 charges with electricity from the outside and discharges electricity to the outside via the external terminals 70A and 70B.

[0041] The shaft member 100 in this embodiment is a rod-shaped member inserted into the first outer casing 12 and the second outer casing 20 of the outer casing 10. Specifically, as shown in Figure 2, the first outer casing 12 has a first shaft hole 110 into which the shaft member 100 is inserted, and the second outer casing 20 has a second shaft hole 120 into which the shaft member 100 is inserted. In other words, the shaft member 100 is inserted into both the second outer casing 20 and the first outer casing 12 when the second outer casing 20 is joined to the first outer casing 12. In the energy storage device 1 according to this embodiment, the shaft member 100 improves the joint strength between the first outer casing 12 and the second outer casing 20. The configuration of the shaft member 100 and its surroundings will be described below with reference to Figures 3 to 7.

[0042] [2. Configuration of the shaft member 100 and its surrounding area] Figure 3 is an exploded perspective view showing the configuration of the shaft member 100 and its surroundings according to the embodiment. Figure 4 is a cross-sectional view showing the configuration of the shaft member 100 and its surroundings according to the embodiment. In Figure 4, a cross-section of a part of the energy storage device 1 is simply shown, which is a cross-section parallel to the XZ plane passing through the line IV-IV in Figure 3. Figure 5 is an enlarged cross-sectional view showing an enlarged portion of the cross-sectional view shown in Figure 4. In Figure 5, the rectangular area labeled with reference numeral "V" in Figure 4 is enlarged and simply shown. In Figures 4 and 5, the joint 90 that joins the first outer casing 12 and the second outer casing 20 is schematically represented by a thick dashed line between the first outer casing 12 and the second outer casing 20.

[0043] Figure 6 is a perspective view showing a portion of the arrangement range of the joint portion 90 according to the embodiment. In Figure 6, the arrangement range of the joint portion 90 on a portion of the open end face 12b of the first exterior body 12 is represented by a patterned area. Figure 7 is a perspective view illustrating an example of a method for forming the joint portion 90 according to the embodiment. In Figures 4, 6, and 7, the illustration of the energy storage unit 51 and the like housed in the exterior body 10 is omitted.

[0044] As shown in Figures 3 to 6, the energy storage device 1 includes a joint 90 that joins the open end face 12b of the first outer casing 12 to the second outer casing 20 by welding or adhesive. The opening 12a is the portion of the first outer casing 12 that forms an opening 13 in the Z-axis positive direction. The Z-axis direction is an example of the first direction, and the Z-axis positive direction is an example of one side of the first direction.

[0045] Examples of welding methods used to form the joint 90 include thermal welding, ultrasonic welding, and laser welding. In this embodiment, the joint 90 is formed by thermal welding. When the joint 90 is formed by bonding the open end face 12b and the second outer casing 20, the adhesive used for the joint 90 is preferably a heat-resistant adhesive such as an epoxy adhesive. A chemical substance may be used as the adhesive to form the joint 90 by chemically melting and then solidifying the open end face 12b and a part of the second outer casing 20.

[0046] In this embodiment, in a plan view (viewed from the Z-axis positive direction), the opening 12a and the opening end face 12b are formed in a rectangular shape that surrounds the housing space for housing the energy storage unit 51. The joint portion 90 according to this embodiment is provided along the entire direction of this rectangular shape (in other words, the direction in which the opening end face 12b extends in a plan view). In other words, the joint portion 90 is arranged to surround the housing space for housing the energy storage unit 51 in a plan view, thereby achieving a high level of airtightness at the boundary between the first outer casing 12 and the second outer casing 20.

[0047] More specifically, in this embodiment, as shown in Figure 3, the second exterior body 20 has an opening 20a that forms an opening in the negative Z-axis direction. The opening 20a is composed of the ends of a pair of second side wall portions 27 and a pair of second side wall portions 28 in the negative Z-axis direction. In other words, the opening 20a is provided at the end of the second exterior body 20 in the negative Z-axis direction. In this embodiment, the opening end face 20b, which is the end face of the opening 20a, is joined to the opening end face 12b of the first exterior body 12 by a joint portion 90. The configuration of the second exterior body 20 is not limited to the above configuration. The second exterior body 20 only needs to be of a size and shape that closes the opening 13 when joined to the opening end face 12b of the first exterior body 12. For example, the second exterior body 20 may be a flat plate-shaped member that closes the opening 13 of the first exterior body 12, and may be a flat plate-shaped member with its thickness direction oriented in the Z-axis direction.

[0048] In the energy storage device 1, when the gas discharge valve 53 of the energy storage element 50 opens and gas is ejected, the gas can be guided to a predetermined location from an outlet (not shown) provided in the outer casing 10, as described above. However, if there is a gap at the boundary between the first outer casing 12 and the second outer casing 20, or if a gap is created due to gas pressure, it becomes difficult to smoothly discharge the gas from the outlet to the predetermined location. Furthermore, the energy storage device 1 may be used in situations where it is exposed to wind and rain, or submerged in water due to natural disasters, etc. Therefore, the joint between the first outer casing 12 and the second outer casing 20 may require high airtightness against gas or liquid. Accordingly, the joint 90 connecting the first outer casing 12 and the second outer casing 20 is an important part from the viewpoint of improving the reliability of the energy storage device 1. In this regard, since the joint 90 is located at the boundary between the first exterior body 12 and the second exterior body 20, it is a part where stress tends to concentrate due to large fluctuations in the internal pressure of the exterior body 10 and repeated fluctuations in internal pressure. For this reason, further improvement in the joint strength of the joint 90 is desired.

[0049] Therefore, in the energy storage device 1 according to this embodiment, the outer casing 10 is provided with a shaft member 100 that penetrates the joint portion 90. Specifically, as shown in Figures 2 to 5, the outer casing 10 is provided with a first shaft hole 110 and a second shaft hole 120 that are opposite each other in the Z-axis direction. The first shaft hole 110 is provided in the first outer casing 12, and the second shaft hole 120 is provided in the second outer casing 20. In this embodiment, the first shaft hole 110 is a bottomed hole that opens into the open end face 12b. In this embodiment, the second shaft hole 120 is a bottomless hole that penetrates the second outer casing 20 in the first direction. That is, the second shaft hole 120 opens into the open end face 20b of the second outer casing 20 and the outer surface (the surface in the Z-axis positive direction) of the upper wall portion 29. In other words, the first shaft hole 110 and the second shaft hole 120 in this embodiment are a single space that holds the shaft member 100 extending in the Z-axis direction, and form a single continuous space in the Z-axis direction.

[0050] Thus, in this embodiment, the shaft member 100 penetrates the joint 90 and is inserted into the first shaft hole 110 of the first outer casing 12 and the second shaft hole 120 of the second outer casing 20. Therefore, when viewed from the direction in which the shaft member 100 extends (Z-axis direction), the shaft member 100 is located within the arrangement range of the joint 90. In other words, the shaft member 100 can efficiently act on the joint 90 to improve the joining force provided by the joint 90. To put it another way, the joint 90 is efficiently reinforced by the shaft member 100.

[0051] In this embodiment, as described above, the joint 90 is formed by heat welding. More specifically, the joint 90 is formed by hot plate welding. In hot plate welding, for example, as shown in Figure 7, a heated plate, the hot plate 500, is sandwiched between the first exterior body 12 and the second exterior body 20, which are the objects to be welded, and after melting their respective end faces, the first exterior body 12 and the second exterior body 20 are joined together.

[0052] The heating plate 500 is provided with through holes 510 at positions opposite the first shaft hole 110 and the second shaft hole 120 in the Z-axis direction. The through holes 510 are larger than the first shaft hole 110 and the second shaft hole 120 in a plan view. This prevents, for example, the opening of the first shaft hole 110 pre-formed in the first outer casing 12 and the opening of the second shaft hole 120 pre-formed in the second outer casing 20 from being blocked by molten resin. A release agent such as fluororesin may be applied to the periphery of the opening of the through holes 510 in the heating plate 500. This prevents the molten resin from being carried away to the periphery.

[0053] The joining of the open end face 12b of the first exterior body 12 and the second exterior body 20 is performed, for example, by the following procedure. After the open end face 12b of the first exterior body 12 and the open end face 20b of the second exterior body 20 are melted by the hot plate 500, the exterior body 12 and the second exterior body 20 move relative to each other in the Z-axis direction so as to move away from the hot plate 500. Specifically, the first exterior body 12 and the second exterior body 20 may move in the negative Z-axis direction and the positive Z-axis direction, respectively, with respect to the hot plate 500, or for example, one of the first exterior body 12 and the second exterior body 20 and the hot plate 500 may move in the negative Z-axis direction or the positive Z-axis direction with respect to the other of the first exterior body 12 and the second exterior body 20. After that, the hot plate 500 moves in the X-axis direction or the Y-axis direction to retract to a predetermined position. Then, the shaft member 100 is inserted into one of the first shaft hole 110 and the second shaft hole 120, and the open end face 12b of the first outer casing 12 and the open end face 20b of the second outer casing 20 are superimposed. At this time, the shaft member 100 is inserted into the other of the first shaft hole 110 and the second shaft hole 120. After that, the molten resin of the first outer casing 12 and the second outer casing 20 are integrated and solidified. As a result, a joint portion 90 is formed that joins the open end face 12b of the first outer casing 12 and the second outer casing 20, with the shaft member 100 positioned to pass through it. In the above joining procedure, it is preferable that the shaft member 100 is press-fitted into each of the first shaft hole 110 and the second shaft hole 120. This improves the bonding strength between the shaft member 100 and each of the first shaft hole 110 and the second shaft hole 120.

[0054] After the shaft member 100 has been inserted into both the first shaft hole 110 and the second shaft hole 120, the open end face 12b of the first outer casing 12 and the open end face 20b of the second outer casing 20 may be melted. In other words, with one end of the shaft member 100 in the Z-axis direction inserted into the first shaft hole 110 and the other end of the shaft member 100 in the Z-axis direction inserted into the second shaft hole 120, the open end faces 12b and 20b may be melted by the hot plate 500. For example, one end of the shaft member 100 is inserted into one of the first shaft hole 110 and the second shaft hole 120, and the other end of the shaft member 100 protruding from that end is inserted into the through hole 510 of the hot plate 500. Furthermore, the other end that has been inserted into the through hole 510 and protruding from the through hole 510 is inserted into the other of the first shaft hole 110 and the second shaft hole 120. Alternatively, one end of the shaft member 100, which is inserted into the through hole 510 of the heating plate 500, is inserted into the first shaft hole 110, and the other end of the shaft member 100 is inserted into the second shaft hole 120. Then, the heating plate 500 is sandwiched between the first outer casing 12 and the second outer casing 20, causing the open end faces 12b and 20b to melt. Next, one of the first outer casing 12 and the second outer casing 20 is separated from the other, one end of the shaft member 100 is removed from one of the first shaft hole 110 and the second shaft hole 120, and the heating plate 500 is removed from between the first outer casing 12 and the second outer casing 20. Next, the end of the shaft member 100 is inserted into the first shaft hole 110 and the second shaft hole 120, and the already melted open end faces 12b and 20b are superimposed. By this procedure, a joint 90 is formed that connects the open end face 12b of the first exterior body 12 to the second exterior body 20, and the joint 90 is positioned with the shaft member 100 passing through it.

[0055] The heating plate 500 does not necessarily have a through hole 510. That is, the opening of the first shaft hole 110 facing the heating plate 500, and the opening of the second shaft hole 120 facing the heating plate 500, may each be sealed with molten resin. Even if these openings are sealed with resin, as long as the resin is molten, the shaft member 100 can be inserted into the first shaft hole 110 and the second shaft hole 120 by breaking through the resin sealing these openings. Even if the resin sealing these openings hardens, if the thickness of the hardened resin is relatively small, the shaft member 100 can be inserted into the first shaft hole 110 and the second shaft hole 120 by breaking through the resin sealing these openings.

[0056] The first shaft hole 110 and the second shaft hole 120 may be formed in the exterior body 10 after the open end face 12b of the first exterior body 12 and the second exterior body 20 have been joined. For example, the open end face 12b of the first exterior body 12 and the second exterior body 20 may be joined by heat welding using a hot plate 500 that does not have through holes 510, and then the first shaft hole 110 and the second shaft hole 120 may be formed from the Z-axis positive direction of the second exterior body 20 by drilling or the like. In this case, the shaft member 100 can be inserted into the second shaft hole 120 and the first shaft hole 110 using a jig or the like from the opening in the Z-axis positive direction of the second shaft hole 120. As a result, the shaft member 100 can be positioned, for example, as shown in Figure 4.

[0057] In other words, when assembling the exterior body 10 equipped with the shaft member 100, the assembly may be carried out in the following order: welding or bonding the first exterior body 12 and the second exterior body 20, forming the first shaft hole 110 and the second shaft hole 120, and inserting the shaft member 100 into the first shaft hole 110 and the second shaft hole 120.

[0058] There are no particular limitations on the shape of the heating plate 500. The heating plate 500 may be a frame-shaped plate corresponding to the open end face 12b in a plan view. In other words, the heating plate 500 may have a portion facing the open end face 12b in the Z-axis direction, but no portion facing the energy storage unit 51 (not shown in Figure 7) in the Z-axis direction. This suppresses the adverse effect of the heat generated by the heating plate 500 on the energy storage unit 51.

[0059] As described above, the energy storage device 1 according to this embodiment comprises an energy storage element 50 and an outer casing 10 that houses the energy storage element 50. The outer casing 10 comprises a first outer casing 12 having an opening 12a on one side in the Z-axis direction, a second outer casing 20 that closes the opening 12a, a joint 90, and a shaft member 100. The joint 90 joins the opening end face 12b, which is the end face of the opening 12a, and the second outer casing 20 by welding or adhesive. The shaft member 100 extends in the Z-axis direction and penetrates the joint 90. The first outer casing 12 has a first shaft hole 110 provided in the opening end face 12b, and the second outer casing 20 has a second shaft hole 120 facing the first shaft hole 110 in the Z-axis direction. The shaft member 100 is inserted into the first shaft hole 110 and the second shaft hole 120.

[0060] Thus, in the energy storage device 1 according to this embodiment, the inside of the outer casing 10 can be sealed by joining the second outer casing 20 and the open end face 12b of the first outer casing 12 at the joint 90. Furthermore, at the boundary between the second outer casing 20 and the first outer casing 12, there is a shaft member 100 that penetrates the joint 90 and is inserted into the second outer casing 20 and the first outer casing 12. Therefore, even if the outer casing 10 deforms to bulge due to an increase in internal pressure of the outer casing 10, the increase in stress generated at the joint 90 is suppressed, and as a result, damage to the joint 90 is effectively suppressed. Accordingly, the energy storage device 1 according to one aspect of the present invention is an energy storage device 1 with improved reliability.

[0061] More specifically, the shaft member 100 that penetrates the joint 90 can restrict the movement of one of the first exterior body 12 and the second exterior body 20 relative to the other, at least in a direction intersecting the direction in which the shaft member 100 extends (Z-axis direction). As a result, for example, if the portion of the exterior body 10 including the joint 90 deforms by bulging outward due to an increase in the internal pressure of the exterior body 10, the shaft member 100 that extends in a direction intersecting the direction of bulging and penetrates the joint 90 suppresses such deformation. In this way, the shaft member 100 according to this embodiment functions as a reinforcing member that reinforces the joint 90. This prevents damage to the joint 90 caused by an increase in the internal pressure of the exterior body 10, or by vibration or impact applied to the exterior body 10.

[0062] More specifically, the shaft member 100 according to this embodiment is a straight rod and has a simple shape with no protruding parts in the radial direction (a direction perpendicular to the axial direction of the shaft member 100). Therefore, the shaft member 100 is easy to manufacture. More specifically, since the shaft member 100 is a cylindrical member with a circular cross-section, the first shaft hole 110 and the second shaft hole 120 are round holes whose inner diameter is approximately the same as the outer diameter of the shaft member 100. Therefore, it is easy to form the first shaft hole 110 in the first outer casing 12 and the second shaft hole 120 in the second outer casing 20.

[0063] In the energy storage device 1 according to this embodiment, the first outer casing 12 and the second outer casing 20 are joined by a joint 90 that connects surfaces extending in a direction perpendicular to the Z-axis direction. Therefore, the joint 90 can effectively restrict the movement of one of the first outer casing 12 and the second outer casing 20 relative to the other in the Z-axis direction. Furthermore, the shaft member 100 that penetrates the joint 90 in the Z-axis direction can effectively restrict the movement of one of the first outer casing 12 and the second outer casing 20 relative to the other in a direction intersecting the Z-axis direction. In other words, in this embodiment, the shaft member 100 can efficiently reinforce the joint 90. As a result, damage to the joint 90 is effectively suppressed.

[0064] In this embodiment, the energy storage device 1 has one shaft member 100, but the energy storage device 1 may have multiple shaft members 100. For example, multiple shaft members 100 may be arranged along the direction in which the opening 12a of the first outer casing 12 extends (the X-axis direction and the Y-axis direction). In this case, the first outer casing 12 only needs to have multiple first shaft holes 110 that correspond one-to-one with the multiple shaft members 100, and the second outer casing 20 only needs to have multiple second shaft holes 120 that correspond one-to-one with the multiple shaft members 100. By providing the energy storage device 1 with multiple shaft members 100, a wider area of ​​the joint 90 is reinforced by the multiple shaft members 100. As a result, the effect of suppressing damage to the joint 90 can be obtained over a wider area.

[0065] When the energy storage device 1 includes a plurality of shaft members 100, an example of the arrangement positions of the plurality of shaft members 100 is described below. In the following description, an example of the arrangement positions of the plurality of shaft members 100 is described with reference to the first outer casing 12. That is, the first shaft hole 110 of the first outer casing 12 and the second shaft hole 120 of the second outer casing 20 may be provided at positions corresponding to the plurality of shaft members 100 shown in the following example.

[0066] The first exterior body 12 has two first side wall portions 17 that face each other in the Y-axis direction, and one or more shaft members 100 may be arranged on each of the first side wall portions 17 that extend in the X-axis direction in a plan view (see Figure 3). For example, one shaft member 100 may be arranged on the first side wall portion 17 in the negative Y-axis direction, and two or more shaft members 100 may be arranged on the first side wall portion 17 in the positive Y-axis direction.

[0067] The first exterior body 12 has two first side wall portions 18 facing each other in the X-axis direction, and one or more shaft members 100 may be arranged on each of the second side wall portions 18 (see Figure 3) that extend in the Y-axis direction in a plan view. For example, one shaft member 100 may be arranged on the first side wall portion 18 in the negative X-axis direction, and two or more shaft members 100 may be arranged on the first side wall portion 18 in the positive X-axis direction.

[0068] One or more shaft members 100 may be arranged on one or both of the two first side wall portions 17, and one or more shaft members 100 may be arranged on one or both of the two second side wall portions 18.

[0069] In any of the above cases, the effect of suppressing damage to the joint 90 by the shaft member 100 can be obtained over a wider range.

[0070] If the energy storage device 1 includes a plurality of shaft members 100, the plurality of shaft members 100 may be the same in length and shape as each other, or may include two or more shaft members 100 that are different in length as each other, or may include two or more shaft members 100 that are different in shape as each other.

[0071] The energy storage device 1 according to this embodiment includes an energy storage unit 51 that includes a plurality of energy storage elements 50 arranged in the Y-axis direction. Therefore, for example, if at least one of the plurality of energy storage elements 50 expands, the energy storage unit 51 may push against the first side wall portion 17 of the outer casing 10 in the Y-axis direction. In other words, the outer casing 10 may deform by bulging due to the expansion of the energy storage elements 50. In this regard, in this embodiment, the shaft member 100 is positioned opposite the energy storage unit 51 in the direction in which the plurality of energy storage elements 50 are arranged. Focusing on a single energy storage element 50, the shaft member 100 is positioned opposite the energy storage element 50 in the direction in which a pair of long sides 52a (see Figure 2) of the energy storage element 50 are opposite each other. Therefore, in the energy storage device 1 equipped with the shaft member 100, damage to the joint portion 90 is effectively suppressed even when the outer casing 10 deforms by bulging due to the expansion of the energy storage elements 50.

[0072] The position of the shaft member 100 in the X-axis direction is within the range between the pair of terminals 55 of the energy storage element 50 in the X-axis direction. More preferably, the position of the shaft member 100 in the X-axis direction coincides with the central position of the pair of terminals 55 of the energy storage element 50 in the X-axis direction. In other words, it is preferable that the central position of the pair of terminals 55 of the energy storage element 50 in the X-axis direction and the shaft member 100 are opposite each other in the Y-axis direction. This more effectively suppresses damage to the joint 90 when the casing 10 deforms and bulges due to the expansion of the energy storage element 50.

[0073] When viewed from the Y-axis direction, at least a portion of the shaft member 100 overlaps with the active material layer (positive electrode active material layer or negative electrode active material layer) of the electrode plate (positive electrode plate or negative electrode plate) of the electrode body of the energy storage element 50. In other words, at least a portion of the shaft member 100 is positioned opposite the area of ​​the energy storage element 50 that is prone to expansion in the Y-axis direction. This also effectively suppresses damage to the joint 90 caused by the expansion of the energy storage element 50.

[0074] In this embodiment, the open end face 12b of the first exterior body 12 and the second exterior body 20 are joined by a welding joint 90. In other words, the joint 90 is formed when these two members melt together at the boundary between the first exterior body 12 and the second exterior body 20. Therefore, it is easy to improve the airtightness at the boundary between the first exterior body 12 and the second exterior body 20 (i.e., the joint 90). Furthermore, as described above, since there is a shaft member 100 inserted into the second exterior body 20 and the first exterior body 12, penetrating the joint 90, damage to the joint 90 is effectively suppressed.

[0075] In this embodiment, as shown in Figures 3 and 6, the opening 12a has a thickened portion 15 where the thickness of the opening end face 12b is greater than that of the other parts. The first shaft hole 110 is provided in the thickened portion 15. The "thickness of the opening end face 12b" is the length in the direction perpendicular to the direction in which the opening end face 12b extends (the same direction in which the opening 12a extends, the X-axis direction in Figure 6) in a plan view. In other words, in Figure 6, the length of the opening end face 12b in the Y-axis direction is the thickness of the opening end face 12b. The same applies to the "thickness of the thickened portion 15".

[0076] In this way, since the elongated shaft member 100 is positioned in the thickened portion 15 of the first outer casing 12, the shaft member 100 is more stably supported by the thickened portion 15, and / or the diameter of the shaft member 100 can be increased. This makes the joint 90 less susceptible to damage. In this embodiment, when viewed from the Y-axis direction, at least a portion of the thickened portion 15 overlaps with the active material layer (positive electrode active material layer or negative electrode active material layer) of the electrode plate (positive electrode plate or negative electrode plate) of the electrode body of the energy storage element 50. In other words, at least a portion of the thickened portion 15 is positioned opposite the area of ​​the energy storage element 50 that is prone to expansion in the Y-axis direction. This effectively suppresses damage to the joint 90 caused by the expansion of the energy storage element 50.

[0077] In this embodiment, as shown in Figures 3 and 6, a thickened portion 15 is provided in the central part of the open end face 12b extending in the X-axis direction. In a plan view, the thickness of the thickened portion 15 increases as it approaches the center in the Z-axis direction from both ends in the X-axis direction. In other words, it is formed so that the thickness of the thickened portion 15 changes gradually. This suppresses the occurrence of surface depressions or internal cavities in the thickened portion 15 due to shrinkage after resin molding. To further suppress such surface depressions caused by shrinkage after resin molding, one or more holes opening into the open end face 12b may be provided in the thickened portion 15 at positions different from the first axial hole 110.

[0078] The shape of the thickened portion 15 is not limited to the shapes shown in Figures 3 and 6. The thickness of the thickened portion 15 may be constant in the X-axis direction. In this embodiment, the thickened portion 15 is formed by a part of the inner surface of the first side wall portion 17 (the surface facing the energy storage unit 51) protruding in a direction toward the energy storage unit 51. As a result, the thickened portion 15 can act on the energy storage unit 51 to suppress expansion of the energy storage unit 51 in the Y-axis direction.

[0079] The thickened portion 15 does not need to be formed over the entire area of ​​the first side wall portion 17 in the Z-axis direction. The thickened portion 15 may be formed only over an area of ​​the first side wall portion 17 or 18 that is roughly the same as the area where the first shaft hole 110 is located in the Z-axis direction. The thickened portion 15 may also be formed by the outer surface (the surface opposite to the inner surface) of the first side wall portion 17 protruding outward. This can, for example, increase the internal space of the exterior body 10. The thickened portion 15 may also be formed only around the first shaft hole 110 in the opening 12a of the first exterior body 12. In other words, in Figure 6, the length of the thickened portion 15 in the X-axis direction may be shorter than the length shown in Figure 6.

[0080] In this embodiment, the second shaft hole 120 is formed on the open end face 20b, which is the end face of the opening 20a of the second outer casing 20. In other words, the second shaft hole 120 is provided on the second side wall portion 27 of the second outer casing 20 (see Figure 3). Therefore, the opening 20a of the second outer casing 20 has a thickened portion 25 on the open end face 20b, which is thicker than other parts. This also allows the shaft member 100 to be supported more stably and / or the diameter of the shaft member 100 to be increased. As a result, the joint portion 90 becomes less susceptible to damage.

[0081] In this embodiment, the outer casing 10 is made of resin, and the shaft member 100 is made of metal. Therefore, problems such as a decrease in strength due to heat or vibration are less likely to occur in the shaft member 100. In other words, the effect of suppressing damage to the joint 90 by the shaft member 100 can be obtained over a longer period of time. Because the mechanical strength of the shaft member 100 is relatively high, the effect of suppressing damage to the joint 90 by the shaft member 100 is further improved. These factors contribute to improving the reliability of the energy storage device 1.

[0082] In this embodiment, the second shaft hole 120 penetrates the second outer casing 20 in the Z-axis direction. In other words, the second shaft hole 120 is a bottomless hole with openings at both ends in the direction in which the second shaft hole 120 extends (Z-axis direction).

[0083] Therefore, after joining the second outer casing 20 and the open end face 12b, the shaft member 100 can be inserted into the first shaft hole 110 and the second shaft hole 120 through the second shaft hole 120 opening on the outer surface of the second outer casing 20. In other words, the joining work (heat welding in this embodiment) between the second outer casing 20 and the open end face 12b can be performed without placing the shaft member 100 in either the second outer casing 20 or the first outer casing 12. As a result, for example, it is easier to perform the joining work with greater precision.

[0084] In this embodiment, for example, as shown in Figure 4, the shaft member 100 does not have a portion that is exposed to the outside of the outer casing 10. "A portion that is exposed to the outside of the outer casing 10" means a portion of the shaft member 100 that protrudes outward from the outer surface of the outer casing 10, or a portion that is in substantially the same position as the outer surface of the outer casing 10. When the end face of the shaft member 100 in the Z-axis positive direction is located in the Z-axis negative direction more than the outer surface of the outer casing 10 (see Figure 4), if the distance between the end face of the shaft member 100 and the outer surface of the second outer casing 20 in the Z-axis positive direction is 1 / 10 or less of the length of the shaft member 100 in the Z-axis direction, then the shaft member 100 is said to have a portion that is in substantially the same position as the outer surface of the outer casing 10.

[0085] Thus, in this embodiment, since the shaft member 100 does not have any portion exposed to the outside of the outer casing 10, damage or deterioration of the shaft member 100 is suppressed, for example. As a result, the reliability of the shaft member 100 is maintained or improved.

[0086] The above description focuses on the configuration of the shaft member 100 and its surroundings in the energy storage device 1 according to the embodiment. However, the configuration of the shaft member 100 and its surroundings in the energy storage device 1 may differ from the configuration shown in Figures 2 to 7. Therefore, the following describes modified configurations of the shaft member 100 and its surroundings, focusing on the differences from the above embodiment.

[0087] [3-1. Variation 1] Figure 8 is a cross-sectional view showing the configuration of the shaft member 100a and its surroundings according to the first modified embodiment. The shaft member 100a provided in the energy storage device 1a according to this modified embodiment is a screw shaft portion 101 that is connected to at least one of the first shaft hole 110 and the second shaft hole 120, and comprises a screw shaft portion 101 having screw threads on its outer circumference. More specifically, the shaft member 100a comprises a screw shaft portion 101 and a screw head 102 with an outer diameter larger than that of the screw shaft portion 101. The screw shaft portion 101 is connected to the first shaft hole 110, and the screw head 102 is in contact with the outer surface (Z-axis positive direction surface) of the upper wall portion 29 of the second outer casing 20. The shaft member 100a according to this modified embodiment is inserted into the second shaft hole 120 and the first shaft hole 110 from the opening in the Z-axis positive direction of the second shaft hole 120 after the joint portion 90 is formed, for example by heat welding.

[0088] The shaft member 100a in this modified example can be realized by a bolt or a tapping screw. This improves the bonding force between the shaft member 100a and the first shaft hole 110 and / or the second shaft hole 120, and as a result, the strength of the joint 90 is further improved. Since the shaft member 100a has a threaded shaft portion 101, the shaft member 100a is inserted into the first shaft hole 110 and the second shaft hole 120 while rotating in the circumferential direction of the threaded shaft portion 101. Therefore, compared to the case where a straight rod-shaped shaft member 100 (see Figures 3 and 4) is inserted into the first shaft hole 110 and the second shaft hole 120 by being pushed in the axial direction, the risk of the shaft member 100a bending when inserted into the first shaft hole 110 and the second shaft hole 120 is lower.

[0089] If the shaft member 100a is a self-tapping screw, the shaft member 100a is inserted into the first shaft hole 110 as it rotates in the circumferential direction, forming a screw groove on the inner surface of the first shaft hole 110. Therefore, it is not necessary to pre-form a screw groove on the inner surface of the first shaft hole 110. If the shaft member 100a is a self-tapping screw, for example, even if the opening of the first shaft hole 110 is blocked with molten resin, the resin can be easily broken. In other words, the shaft member 100a can be easily inserted into the first shaft hole 110.

[0090] In Figure 8, the head portion 102 is positioned outside the outer surface (the surface in the positive Z-axis direction) of the upper wall portion 29 of the second outer casing 20. However, the head portion 102 may be housed in a recess (not shown) provided in the upper wall portion 29 of the second outer casing 20. In other words, the shaft member 100a may be positioned such that the head portion 102 of the shaft member 100a does not protrude outside the outer surface of the upper wall portion 29 of the second outer casing 20.

[0091] Furthermore, by removing the head portion 102 from the shaft member 100a, it is also possible to construct the shaft member using only the screw shaft portion 101.

[0092] [3-2. Variation 2] Figure 9 is a cross-sectional view showing the configuration of the shaft member 100b and its surroundings according to a modified example 2 of the embodiment. In the energy storage device 1b according to this modified example, the first shaft hole 110 penetrates the first outer casing 12 in the Z-axis direction, and the second shaft hole 120 penetrates the second outer casing 20 in the Z-axis direction. That is, the first shaft hole 110 is a bottomless hole with openings at both ends in the direction in which the first shaft hole 110 extends (Z-axis direction), and the second shaft hole 120 is a bottomless hole with openings at both ends in the direction in which the second shaft hole 120 extends (Z-axis direction). Therefore, both the first shaft hole 110 and the second shaft hole 120 open to the outer surface of the outer casing 10. Specifically, the first shaft hole 110 opens to the first outer surface 19a, which is the Z-axis negative direction surface of the bottom wall portion 19 of the first outer casing 12. The second shaft hole 120 opens into the second outer surface 29a, which is the Z-axis positive surface of the upper wall portion 29 of the second outer body 20. The first outer surface 19a is the Z-axis negative outer surface of the outer body 10, and the second outer surface 29a is the Z-axis positive outer surface of the outer body 10.

[0093] Thus, since both the first shaft hole 110 and the second shaft hole 120 open to the outer surface of the casing 10, the shaft member 100b can be inserted into the first shaft hole 110 and the second shaft hole 120 after the second casing 20 and the opening end face 12b have been joined. The presence of the shaft member 100b inside the first shaft hole 110 and the second shaft hole 120 can be confirmed from both the positive Z-axis direction and the negative Z-axis direction. Furthermore, since the shaft member 100b is positioned throughout the entire area of ​​the casing 10 in the Z-axis direction, the function of the shaft member 100b in improving the mechanical strength of the casing 10 becomes more pronounced. For example, if the energy storage device 1b according to this modified example is subjected to an excessive impact from the negative Y-axis direction, the shaft member 100b will be hit before the energy storage element 50, thus suppressing damage to the energy storage element 50 due to the impact.

[0094] [3-3. Modified Example 3] Figure 10 is a cross-sectional view showing the configuration of the shaft member 100c and its surroundings according to a modified example 2 of the embodiment. In the energy storage device 1c according to this modified example, the first shaft hole 110 penetrates the first outer casing 12 in the Z-axis direction, and the second shaft hole 120 does not penetrate the second outer casing 20c in the Z-axis direction. In other words, the first shaft hole 110 is a bottomless hole with both ends open in the direction in which the first shaft hole 110 extends (Z-axis direction), and the second shaft hole 120 is a bottomed hole with only one end open in the direction in which the second shaft hole 120 extends (Z-axis direction). Specifically, the second shaft hole 120 is open only at the end in the Z-minus direction, and the end in the Z-plus direction is closed.

[0095] Therefore, after joining the second outer casing 20 to the open end face 12b, the shaft member 100c can be inserted into the first shaft hole 110 and the second shaft hole 120 through the first shaft hole 110 opening in the first outer surface 19a of the first outer casing 12. Furthermore, when the energy storage device 1c is positioned with the second outer casing 20 above the first outer casing 12, the upper end surface of the shaft member 100c is covered by a portion of the upper wall portion 29 of the second outer casing 20. Therefore, foreign matter such as moisture from outside the outer casing 10 is less likely to adhere to the upper end surface of the shaft member 100c. This suppresses damage or deterioration of the shaft member 100c. As a result, the reliability of the shaft member 100c is maintained or improved.

[0096] [4. Other variations] Although the embodiment of the energy storage device 1 and its modified forms have been described above, the present invention is not limited to the embodiment and its modified forms. In other words, the embodiments disclosed herein are illustrative and not restrictive in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims.

[0097] The opening 12a of the first exterior body 12 does not need to have a thickened portion 15. For example, if the thickness of the first side wall portion 17 or 18 is sufficiently large compared to the outer diameter of the shaft member 100, the first shaft hole 110 can be provided on the opening end face 12b without providing a thickened portion 15. The opening 20a of the second exterior body 20 does not need to have a thickened portion 25. For example, if the thickness of the second side wall portion 27 or 28 is sufficiently large compared to the outer diameter of the shaft member 100, the second shaft hole 120 can be provided on the opening end face 20b without providing a thickened portion 25. Even if the second exterior body 20 is a flat plate-shaped member that does not have second side wall portions 27 and 28, it is not necessary to provide a thickened portion 25.

[0098] The shaft member 100 may be made of a material other than metal. For example, the shaft member 100 may be made of a resin that has higher rigidity than the resin that forms the outer casing 10. The shaft member 100 may be made of fiber-reinforced plastic, which is a combination of reinforcing fibers and resin. The shape of the shaft member 100 does not have to be cylindrical. For example, a rod body whose cross-section perpendicular to the axial direction is polygonal, elliptical, or oblong may be used as the shaft member 100.

[0099] The shaft member 100 may have a portion that is exposed to the outside of the outer casing 10, as shown in the shaft member 100a in Modification 1. In this case, it is easy to confirm whether or not the shaft member 100 is placed on the outer casing 10.

[0100] It is not mandatory for the pair of external terminals 70 to be located on the second outer casing 20 of the outer casing 10. At least one of the pair of external terminals 70 may be located on the first outer casing 12. If the cable electrically connected to the energy storage unit 51 functions as an external terminal, the pair of external terminals 70 may not be located on the outer casing 10.

[0101] The shape of the outer casing 10 does not have to be a rectangular parallelepiped as shown in Figures 1 and 2. For example, an outer casing of another shape, such as a cylindrical shape, may be used as the outer casing for housing the energy storage unit 51, etc.

[0102] In this embodiment, the first outer casing 12 has a volume capable of accommodating the energy storage unit 51 from the opening 12a toward the bottom wall portion 19, and the second outer casing 20 has a volume smaller than the volume of the first outer casing 12 from the opening 20a toward the top wall portion 29 (see Figure 3). Here, the volume of the second outer casing 20 can be the same as or larger than the volume of the first outer casing 12. Furthermore, even if the volume of the second outer casing 20 is larger than the volume of the first outer casing 12, the second outer casing 20 can be treated as blocking the opening 12a of the first outer casing 12.

[0103] The energy storage unit 51 is not limited to being housed and fixed in the first outer casing 12, but can also be housed and fixed in the second outer casing 20.

[0104] The various supplementary details concerning the configuration of the shaft member 100 and its surroundings according to the above-described embodiment may be appropriately applied to the shaft members 100a, 100b, and 100c, and their surrounding configurations, according to Modifications 1 to 3. Configurations constructed by arbitrarily combining the components included in the above embodiment and its modified forms are also included within the scope of the present invention. [Industrial applicability]

[0105] This invention can be applied to energy storage devices equipped with energy storage elements such as lithium-ion secondary batteries. [Explanation of Symbols]

[0106] 1, 1a, 1b, 1c power storage device 10 Exterior 12 First exterior body 12a, 20a opening 12b, 20b open end surface 13 Aperture 15, 25 Thick part 20 Second exterior body 50 Energy storage elements 90 Joint 100, 100a, 100b, 100c shaft member 101 Shaft 102 Head 110 First shaft hole 120 Second shaft hole

Claims

1. Energy storage element, The system comprises an outer casing for housing the energy storage element, The exterior body is, A first exterior body having an opening on one side in the first direction, A second exterior body that closes the aforementioned opening, A joint portion is provided to join the opening end face, which is the end face of the opening, and the second exterior body by welding or adhesive, It comprises a shaft member that extends in the first direction and penetrates the joint, The first exterior body is The opening end face is provided with a first shaft hole, The second exterior body is provided with a second shaft hole that faces the first shaft hole in the first direction, The shaft members are inserted into the first shaft hole and the second shaft hole. Energy storage device.

2. The opening has a thicker portion where the thickness of the opening end face is greater than that of other parts. The first shaft hole is provided in the thickened portion. The energy storage device according to claim 1.

3. The exterior body is made of resin, and the shaft member is made of metal. The energy storage device according to claim 1 or 2.

4. The shaft member comprises a screw shaft portion that is connected to at least one of the first shaft hole and the second shaft hole, and has a screw shaft portion on its outer circumference. The energy storage device according to claim 1 or 2.

5. The first shaft hole penetrates the first outer casing in the first direction, or the second shaft hole penetrates the second outer casing in the first direction. The energy storage device according to claim 1 or 2.

6. The shaft member does not have any portion exposed to the outside of the outer casing. The energy storage device according to claim 1 or 2.

7. Energy storage element, The system comprises an outer casing for housing the energy storage element, The exterior body is, A first exterior body having an opening on one side in the first direction, A second exterior body that closes the aforementioned opening, A joint portion is formed by welding the opening end face, which is the end face of the opening, to the second exterior body, It comprises a shaft member that extends in the first direction and penetrates the joint, The first exterior body is The opening end face is provided with a first shaft hole, The second exterior body is provided with a second shaft hole that faces the first shaft hole in the first direction, The shaft members are inserted into the first shaft hole and the second shaft hole. Energy storage device.

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