Method for manufacturing an energy storage device and lower case

Abstract

To provide an energy storage device that can prevent waste from an energy storage cell from coming into contact with the safety valve of an adjacent energy storage cell. [Solution] The energy storage device 10 comprises at least one energy storage cell and a lower case 210. A safety valve SV is provided on the lower surface of the energy storage cell. The lower case 210 has a bottom plate 211 provided below the energy storage cell and a bottom wall 212 which defines a smoke exhaust path S by being the bottom plate and the bottom wall 212. The bottom plate 211 has a through hole 211h. The bottom plate 211 and the bottom wall 212 are integrally formed from the same material, seal the smoke exhaust path S, and have a cast surface.

Description

Technical Field

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[0001] The present disclosure relates to a method for manufacturing a power storage device and a lower case.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2023-126584 discloses a battery including a plurality of cells, a case that houses the plurality of cells, a protection member that protects the bottom portion of the case, and a cover. The protection member is fixed to the bottom portion of the case by a fastener. A relief mechanism is provided on the bottom surface of each cell. The discharged material discharged from the relief mechanism flows into a collection cavity formed between the bottom portion of the case and the protection member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the battery described in Japanese Patent Application Laid-Open No. 2023-126584, there is a concern that moisture may enter the collection cavity from the gap between the bottom portion of the case and the protection member.

[0005] An object of the present disclosure is to provide a method for manufacturing a power storage device and a lower case capable of suppressing the intrusion of moisture into the smoke exhaust path.

Means for Solving the Problems

[0006] A power storage device according to one aspect of the present disclosure comprises at least one power storage cell and a lower case housing at least a portion of the at least one power storage cell, wherein a safety valve is provided on the lower surface of the at least one power storage cell, and the lower case has a bottom plate provided below the at least one power storage cell and a bottom wall provided below the bottom plate, the bottom wall and the bottom plate together define a smoke exhaust path, the bottom plate has a through hole provided at a position opposite the safety valve, the bottom plate and the bottom wall are integrally formed from the same material and seal the smoke exhaust path and have a cast surface.

[0007] A method for manufacturing a lower case according to one aspect of the present disclosure is a method for manufacturing a lower case that houses at least a portion of at least one energy storage cell, comprising the steps of forming a bottom plate provided below the at least one energy storage cell and a bottom wall provided below the bottom plate, the bottom wall defining a smoke exhaust path together with the bottom plate and the bottom wall, wherein a core for forming the smoke exhaust path is placed in a pair of molds that are separable from each other, and a metal material for forming the bottom plate and the bottom wall is supplied into the gap between the pair of molds and the core. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a power storage device and a method for manufacturing a lower case that can suppress the intrusion of moisture into the exhaust gas path. [Brief explanation of the drawing]

[0009] [Figure 1] This figure schematically shows a vehicle equipped with an energy storage device according to one embodiment of the present disclosure. [Figure 2] This is a schematic perspective view of an energy storage device. [Figure 3] This is a schematic plan view showing the power storage device with the upper cover removed. [Figure 4] Figure 3 shows a cross-sectional view along line IV-IV. [Figure 5]Figure 3 is a cross-sectional view along the VV line. [Figure 6] This diagram schematically shows a pair of molds and cores used in the manufacture of the lower case. [Figure 7] This is a cross-sectional view illustrating a modified example of the lower case. [Figure 8] This is a cross-sectional view illustrating a modified example of the lower case. [Figure 9] This is a cross-sectional view illustrating a modified example of the lower case. [Figure 10] This is a schematic cross-sectional view showing a modified example of the base plate. [Figure 11] Figure 10 is a schematic diagram showing a pair of molds and cores used in the manufacture of the base plate and base wall shown. [Figure 12] This is a schematic cross-sectional view showing a modified example of the base plate. [Figure 13] Figure 12 is a schematic diagram showing a pair of molds, a core, and a cylindrical section used in the manufacture of the base plate and base wall shown. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described with reference to the drawings. In the drawings referred to below, the same or equivalent components are given the same number.

[0011] Figure 1 is a schematic diagram showing a vehicle equipped with an energy storage device according to one embodiment of the present disclosure. Figure 2 is a schematic perspective view showing the energy storage device. Figure 3 is a schematic plan view showing the energy storage device with the upper cover removed. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3. Figure 5 is a cross-sectional view taken along line VV in Figure 3.

[0012] As shown in FIG. 1, the vehicle 1 includes a vehicle body 2 and a power storage device 10. Examples of the vehicle 1 include a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a battery electric vehicle.

[0013] As shown in FIG. 1, the vehicle body 2 includes a frame member 20. The frame member 20 is disposed at the bottom of the vehicle body 2. The frame member 20 is formed in a substantially rectangular tube shape that surrounds the power storage device 10.

[0014] The power storage device 10 is attached to the frame member 20. As shown in FIGS. 1 to 5, the power storage device 10 includes six power storage stacks 11 to 16, a housing 200, a heat insulating member 280, devices 300, a device cooler 350, and a refrigerant pipe 400. Note that the number of power storage stacks is not limited to six.

[0015] Each of the power storage stacks 11 to 16 is formed in a rectangular parallelepiped shape that is long in the first direction. As shown in FIG. 3, the six power storage stacks 11 to 16 are arranged so as to line up along a second direction that is orthogonal to both the first direction and the vertical direction. In the present embodiment, the first direction corresponds to the front-rear direction of the vehicle, and the second direction corresponds to the left-right direction (width direction) of the vehicle. Each of the power storage stacks 11 to 16 includes at least one power storage cell 100. In the present embodiment, each of the power storage stacks 11 to 16 includes a plurality of power storage cells 100 and a plurality of cooling plates 150.

[0016] The plurality of power storage cells 100 are arranged so as to line up along the first direction. As shown in FIGS. 4 and 5, each power storage cell 100 has an electrode body 112, a cell case 114, and a pair of external terminals 116.

[0017] The electrode body 112 may be composed of a wound body in which a positive electrode sheet and a negative electrode sheet are wound with a separator in between, or it may be composed of a laminate in which a positive electrode sheet and a negative electrode sheet are stacked with a separator in between. The electrode body 112 is formed in a shape that is elongated in the second direction.

[0018] The cell case 114 houses the electrode body 112. The cell case 114 is formed in a rectangular parallelepiped shape. The cell case 114 is made of a metal such as aluminum. A safety valve SV is provided on the lower surface of the cell case 114.

[0019] A pair of external terminals 116 are provided on the upper surface of the cell case 114. The pair of external terminals 116 are provided at positions spaced apart from each other in the width direction of the cell case 114. The width direction of the cell case 114 corresponds to the second direction.

[0020] As shown in Figures 4 and 5, each cooling plate 150 is positioned between a pair of adjacent energy storage cells 100 in the first direction. Each cooling plate 150 is formed in a long, flat shape in the second direction. Each cooling plate 150 has a flow path (not shown) through which a refrigerant flows along the second direction.

[0021] The housing 200 houses six energy storage stacks 11-16. As shown in Figures 4 and 5, the housing 200 includes a lower case 210 and an upper cover 220.

[0022] The lower case 210 is open upwards. The lower case 210 is made of a metal such as aluminum. The lower case 210 is formed by casting. Therefore, the surface of the lower case 210 is made of a cast surface. The lower case 210 has a bottom plate 211, a bottom wall 212, a peripheral wall 213, a pair of partition walls 214, and a flange 215.

[0023] The base plate 211 is located below each of the energy storage stacks 11-16. The base plate 211 is formed in a flat shape. As shown in Figures 4 and 5, the base plate 211 has a plurality of through holes 211h. Each through hole 211h is located opposite the safety valve SV of the energy storage cell 100. The cross-sectional area of ​​each through hole 211h in a plane parallel to the base plate 211 gradually increases as it goes downwards.

[0024] The bottom wall 212 is located below the bottom plate 211. The bottom plate 211 and the bottom wall 212 define the smoke exhaust path S. The smoke exhaust path S is a path for discharging gas discharged from the safety valve SV of the energy storage cell 100 to the outside of the housing 200. The smoke exhaust path S is sealed by the bottom plate 211 and the bottom wall 212, except for the smoke exhaust duct section 218 which will be described later. The bottom wall 212 may be formed parallel to the bottom plate 211. The thickness of the bottom wall 212 may be greater than the thickness of the bottom plate 211.

[0025] The peripheral wall 213 surrounds each of the energy storage stacks 11-16. The peripheral wall 213 is connected to the base plate 211 and the base wall 212. The peripheral wall 213 rises from the periphery of the base plate 211 and the base wall 212.

[0026] As shown in Figures 3 and 5, a smoke exhaust duct section 218 is formed in the peripheral wall 213. The smoke exhaust duct section 218 extends upward from the bottom wall 212. The smoke exhaust duct section 218 guides gas upward from the smoke exhaust path S. An explosion-proof valve 290 is provided near the downstream end of the smoke exhaust duct section 218 on the peripheral wall 213. The explosion-proof valve 290 releases pressure inside the housing 200. The explosion-proof valve 290 opens when the pressure inside the housing 200 exceeds a reference value. The explosion-proof valve 290 is composed of a check valve. As shown in Figure 5, when gas is discharged from any of the energy storage cells 100, the gas spreads in the first direction through the smoke exhaust path S and is discharged outside the housing 200 through the smoke exhaust duct section 218 and the explosion-proof valve 290.

[0027] A pair of partition walls 214 divide the space enclosed by the base plate 211 and the peripheral wall 213 into a space in which each energy storage stack 11-16 is arranged and other spaces. The pair of partition walls 214 are spaced apart from each other in a first direction. Each partition wall 214 rises from the base plate 211. Each partition wall 214 extends in a second direction. Each partition wall 214 may be formed in a hollow shape. The pair of partition walls 214 have the function of restraining each energy storage stack 11-16 from both sides in the first direction. As shown in Figure 3, the end of the partition wall 214 formed on one side (front side) in the first direction in the second direction is spaced apart from the peripheral wall 213. The end of the partition wall 214 formed on the other side (rear side) in the first direction in the second direction is connected to the peripheral wall 213.

[0028] The flange 215 protrudes outward from the outer surface of the peripheral wall 213 in the second direction.

[0029] In this embodiment, the bottom plate 211, bottom wall 212, peripheral wall 213, pair of partition walls 214, flange 215, and exhaust duct section 218 are integrally formed from the same material (metal such as aluminum) and have a cast surface. The bottom plate 211 and bottom wall 212 seal the exhaust path S.

[0030] The upper cover 220 is positioned above each of the energy storage stacks 11-16. The upper cover 220, together with the lower case 210, houses the six energy storage stacks 11-16. Specifically, the upper cover 220, together with the lower case 210, houses the six energy storage stacks 11-16 in a sealed state. The peripheral edge of the upper cover 220 is connected to the upper end of the peripheral wall 213 by bolts or the like via a sealing member.

[0031] The heat insulating members 280 are provided on the bottom plate 211. Each heat insulating member 280 has a shape that covers the through hole 211h. Each heat insulating member 280 has the function of protecting each energy storage cell 100 from gas discharged from the safety valve SV. Each heat insulating member 280 is made of, for example, mica, which is made by solidifying natural inorganic minerals by heat pressing.

[0032] The equipment 300 is housed in the enclosure 200. As shown in Figure 3, the equipment 300 is located in the space formed between the partition wall 214 and the peripheral wall 213 on the other side of the lower case 210 in the first direction, i.e., the other side (rear side) in the first direction. The equipment 300 may include a junction box. The equipment 300 may include relays, control equipment, etc.

[0033] The equipment cooler 350 cools the equipment 300. As shown in Figures 3 and 5, the equipment cooler 350 is provided between the extension 211a of the base plate 211 and the equipment 300. A thermally conductive adhesive 900 may be provided between the equipment cooler 350 and the extension 211a.

[0034] The refrigerant piping 400 is routed within the housing 200. The refrigerant piping 400 is connected to each cooling plate 150 and the equipment cooler 350. As shown in Figures 2 and 3, an inlet port 181 and an outlet port 182 are provided on the front wall 213f formed on one side (front side) of the peripheral wall 213 in the first direction. The refrigerant piping 400 is connected to the inlet port 181 and the outlet port 182. Therefore, the refrigerant (water, oil, etc.) supplied from the inlet port 181 flows through the refrigerant piping 400 to each cooling plate 150 and the equipment cooler 350, cools each energy storage cell 100 and equipment 300, and then flows out through the refrigerant piping 400 to the outlet port 182.

[0035] As shown in Figure 3, the refrigerant piping 400 includes an upstream pipe 410 and a downstream pipe 420.

[0036] The upstream end of the upstream piping 410 is connected to the inlet port 181. The downstream end of the upstream piping 410 is connected to one end of the equipment cooler 350 in the second direction. The upstream piping 410 is routed to pass between the front wall 213f and the partition wall 214 formed on one side in the first direction, and between the energy storage stack 11 and the peripheral wall 213 located on one side in the second direction. The upstream piping 410 is connected to one end of each cooling plate 150 in the second direction.

[0037] The upstream end of the downstream pipe 420 is connected to the other end of the equipment cooler 350 in the second direction. The downstream end of the downstream pipe 420 is connected to the outlet port 182. The downstream pipe 420 is routed to pass between the front wall 213f and the partition wall 214 formed on one side in the first direction, and between the energy storage stack 16 and the peripheral wall 213 located on the other side in the second direction. The downstream pipe 420 is connected to the other end of each cooling plate 150 in the second direction.

[0038] In the energy storage device 10 described above, if a discharge is made downward from the safety valve SV due to a short circuit or the like in any of the energy storage cells 100, the discharge will collide with the heat insulating member 280. As a result, the heat insulating member 280 will rupture, and the discharge will flow into the exhaust gas path S. Subsequently, the gas contained in the discharge will spread through the exhaust gas path S and be discharged from the housing 200 through the explosion-proof valve 290 as shown in Figure 5. Therefore, the adhering of the contents of the energy storage cell 100 (so-called debris) contained in the discharged discharge from the energy storage cell 100 to the external terminals 116 of the energy storage cell 100 is suppressed.

[0039] Next, the manufacturing method of the lower case 210 will be described with reference to Figure 6. The lower case 210 is formed by casting. In this manufacturing method, a pair of molds 510 and 520 and a core 550 are used.

[0040] The pair of molds 510, 520 has a lower mold 510 and an upper mold 520 that are separable from each other. The pair of molds 510, 520 has an internal space that corresponds to the outer shape of the lower case 210. The lower mold 510 is provided with an opening 510h for supplying molten metal into the pair of molds 510, 520.

[0041] The core 550 is used to form the exhaust path S. The core 550 may be made of, for example, sand. As shown in Figure 6, the core 550 includes a through-hole forming portion 552 for forming a through-hole 211h in the bottom plate 211. The core 550 may also include a protrusion 553 for forming an opening for mounting the explosion-proof valve 290.

[0042] In this manufacturing method, with the core 550 positioned inside a pair of molds 510 and 520, a metal material (such as aluminum) for forming the lower case 210 is supplied into the gap (internal space) between the pair of molds 510 and 520 and the core 550. Subsequently, the core 550 is removed from inside the lower case 210.

[0043] In this manufacturing method, a bottom plate 211 and bottom wall 212 having a sealed exhaust passage S are formed, thereby suppressing the intrusion of moisture into the exhaust passage S. Furthermore, when the bottom plate is manufactured by extrusion molding or the like, a process of forming multiple through holes in the bottom plate is required, which complicates the manufacturing process and increases manufacturing costs. However, as in this embodiment, by integrally molding the bottom plate 211 and bottom wall 212 by casting, the process of forming through holes becomes unnecessary.

[0044] Modifications of the above embodiment will be described below.

[0045] <First variation> As shown in Figures 7 and 8, the peripheral wall 213 may be constructed separately from the bottom plate 211 and bottom wall 212. In other words, it is sufficient that at least the bottom plate 211 and bottom wall 212 are integrally formed by casting. In the example shown in Figures 7 and 8, the peripheral wall 213 is formed in a hollow shape by extrusion molding.

[0046] <Second variation> As shown in Figure 9, the peripheral wall 213 may include an inclined wall 213a. The inclined wall 213a is inclined so as it moves upward, it gradually moves away from the energy storage cell 100. In the example shown in Figure 9, the inclined wall 213a is made up of the other side (rear side) wall of the peripheral wall 213 in the first direction. The explosion-proof valve 290 is provided on the inclined wall 213a.

[0047] In this embodiment, the accumulation of debris at corners is suppressed.

[0048] <Third variation> As shown in Figure 10, the lower case 210 may further have a cylindrical portion 217 that protrudes toward the bottom wall 212 from the portion of the bottom plate 211 surrounding the through hole 211h. In the example shown in Figure 10, the cylindrical portion 217 is integrally formed with the bottom plate 211 from the same material as the bottom plate 211. The lower end of the cylindrical portion 217 is separated upward from the bottom wall 212. The cross-sectional area of ​​the cylindrical portion 217 in a plane parallel to the bottom plate 211 gradually decreases toward the bottom wall 212.

[0049] In this example, the lower case 210 is formed by the lower mold 510 and upper mold 520 shown in Figure 11. The upper mold 520 has a cylindrical portion forming section 524 for forming the cylindrical portion 217. The lower mold 510 has a receiving surface 554 for receiving the cylindrical portion forming section 524.

[0050] In this example, with the lower end of the cylindrical forming portion 524 of the upper mold 520 in contact with the receiving surface 554 of the core 550, a metal material (such as aluminum) for forming the lower case 210 is supplied into the gap (internal space) between the pair of molds 510, 520 and the core 550.

[0051] In this embodiment, when gas that has flowed from one energy storage cell 100 into the exhaust gas path S through the cylindrical portion 217 spreads within the exhaust gas path S, as shown in Figure 10, the gas forms a swirling flow within the cylindrical portion 217 located below the energy storage cell 100 adjacent to the first energy storage cell 100 (hereinafter referred to as the "adjacent energy storage cell"). As a result, the gas rising within the cylindrical portion 217 is prevented from contacting the safety valve SV of the adjacent energy storage cell.

[0052] <Fourth variation> Similar to the third modification, the lower case 210 may have a cylindrical portion 217. As shown in Figure 12, in this example, the cylindrical portion 217 is made of a separate material from the bottom plate 211.

[0053] In this example, the cylindrical portion 217 has a cylindrical body 217a and a flange portion 217b. The shape of the cylindrical body 217a is the same as the shape of the cylindrical portion 217 in the third modified example. The flange portion 217b protrudes outward from the top of the cylindrical body 217a in the radial direction of the cylindrical body 217a. The flange portion 217b may be connected in an annular shape. The flange portion 217b is located within the bottom plate 211.

[0054] In this example, the lower case 210 is formed by the lower mold 510, upper mold 520, and cylindrical portion 217 shown in Figure 13. In this example, with the cylindrical portion 217 placed on the receiving surface 554 of the core 550 and the cylindrical portion forming portion 524 of the upper mold 520 inserted into the cylindrical portion body 217a, a metal material (such as aluminum) for forming the lower case 210 is supplied into the gap (internal space) between the pair of molds 510, 520 and the core 550.

[0055] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0056] [Aspect 1] At least one energy storage cell, A lower case housing at least a portion of the at least one energy storage cell, A safety valve is provided on the lower surface of at least one of the energy storage cells. The aforementioned lower case is A bottom plate provided below at least one of the energy storage cells, A bottom wall provided below the bottom plate, the bottom wall having a smoke exhaust path defined by the bottom plate and the bottom wall, The bottom plate has a through hole provided at a position opposite the safety valve, An energy storage device wherein the bottom plate and the bottom wall are integrally formed from the same material, seal the exhaust gas path, and have a cast surface.

[0057] In this energy storage device, the bottom plate and bottom wall are formed, for example, by casting, thereby creating a bottom plate and bottom wall with a sealed exhaust passage, which suppresses the intrusion of moisture into the exhaust passage.

[0058] [Aspect 2] The lower case is further equipped with an explosion-proof valve, The lower case is connected to the bottom plate and the bottom wall and further has a peripheral wall surrounding the at least one energy storage cell, The peripheral wall includes an inclined wall that slopes upward so as it moves, gradually moving away from the at least one energy storage cell. The energy storage device according to embodiment 1, wherein the explosion-proof valve is provided on the inclined wall.

[0059] In this embodiment, the accumulation of waste (so-called debris, etc.) at the corners between the bottom wall and the inclined wall is suppressed as waste discharged from the energy storage cell travels through the exhaust path towards the explosion-proof valve.

[0060] [Aspect 3] The aforementioned at least one energy storage cell includes a plurality of energy storage cells, The lower case further has a cylindrical portion that protrudes toward the bottom wall from the portion of the bottom plate surrounding the through hole, The energy storage device according to embodiment 1 or 2, wherein the lower end of the cylindrical portion is separated upward from the bottom wall.

[0061] In this embodiment, when gas flowing from one energy storage cell into the exhaust path through the cylindrical section spreads within the exhaust path, the gas forms a swirling flow within the cylindrical section located below the energy storage cell adjacent to the first energy storage cell. As a result, the gas rising within the cylindrical section is prevented from contacting the safety valve of the adjacent energy storage cell.

[0062] [Aspect 4] The energy storage device according to embodiment 3, wherein the cylindrical portion is made of a separate material from the bottom plate.

[0063] In this embodiment, the degree of freedom in selecting the material for forming the cylindrical portion is increased.

[0064] [Aspect 5] A method for manufacturing a lower case that houses at least a portion of at least one energy storage cell, The process includes forming a bottom plate provided below at least one of the energy storage cells, and a bottom wall provided below the bottom plate, the bottom wall which defines a smoke exhaust path together with the bottom plate and the bottom wall, A method for manufacturing a lower case, wherein, in the step described above, a core for forming the exhaust path is placed in a pair of molds that are separable from each other, and a metal material for forming the bottom plate and the bottom wall is supplied into the gap between the pair of molds and the core.

[0065] In this manufacturing method, a bottom plate and bottom wall with a sealed exhaust passage are formed, thereby suppressing the intrusion of moisture into the exhaust passage.

[0066] [Aspect 6] The method for manufacturing a lower case according to embodiment 5, wherein the step uses a core that includes a protrusion for forming a through hole at a position opposite to a safety valve provided on the lower surface of at least one energy storage cell.

[0067] In this embodiment, since a through hole is formed in the bottom plate at a position facing the safety valve of the energy storage cell during the process of forming the bottom plate and bottom wall, the formation of the bottom plate is simplified compared to the case where the through hole is formed in a separate process after the bottom plate is formed.

[0068] [Aspect 7] A method for manufacturing a lower case according to embodiment 5 or 6, wherein the step involves using a pair of molds that are connected to the bottom plate and the bottom wall and capable of forming a peripheral wall surrounding at least one energy storage cell.

[0069] In this embodiment, the periphery wall is formed integrally with the bottom plate and bottom wall.

[0070] It should be noted that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of this disclosure is defined by the claims rather than the description of the embodiments above, and includes all modifications within the meaning and scope equivalent to the claims. [Explanation of Symbols]

[0071] 1 Vehicle, 2 Vehicle body, 10 Energy storage device, 11-16 Energy storage stack, 20 Frame member, 100 Energy storage cell, 112 Electrode body, 114 Cell case, 116 External terminal, 200 Housing, 210 Lower case, 211 Bottom plate, 212 Bottom wall, 213 Peripheral wall, 214 Partition wall, 215 Flange, 217 Cylinder section, 217a Cylinder section body, 217b Flange section, 218 Smoke exhaust duct section, 220 Upper cover, 300 Equipment, 350 Equipment cooler, 400 Refrigerant piping, 410 Upstream piping, 420 Downstream piping, 510 Lower mold, 510h Opening, 520 Upper mold, 524 Cylinder section forming section, 550 Core, 552 Through hole forming section, 553 Protrusion, 554 Receiving surface, 900 thermal conductive adhesive, S space (smoke exhaust path), SV safety valve.

Claims

1. At least one energy storage cell, A lower case housing at least a portion of the at least one energy storage cell, A safety valve is provided on the lower surface of at least one of the energy storage cells. The aforementioned lower case is A bottom plate provided below at least one of the energy storage cells, A bottom wall provided below the bottom plate, the bottom wall having a smoke exhaust path defined by the bottom plate and the bottom wall, The bottom plate has a through hole provided at a position opposite the safety valve, An energy storage device wherein the bottom plate and the bottom wall are integrally formed from the same material, seal the exhaust gas path, and have a cast surface.

2. The lower case is further equipped with an explosion-proof valve, The lower case is connected to the bottom plate and the bottom wall and further has a peripheral wall surrounding the at least one energy storage cell, The peripheral wall includes an inclined wall that slopes upward so as it extends, gradually moving away from the at least one energy storage cell. The explosion-proof valve is provided in the inclined wall, as described in claim 1.

3. The aforementioned at least one energy storage cell includes a plurality of energy storage cells, The lower case further has a cylindrical portion that protrudes toward the bottom wall from the portion of the bottom plate surrounding the through hole, The energy storage device according to claim 1, wherein the lower end of the cylindrical portion is separated upward from the bottom wall.

4. The energy storage device according to claim 3, wherein the cylindrical portion is made of a separate material from the bottom plate.

5. A method for manufacturing a lower case that houses at least a portion of at least one energy storage cell, The process includes forming a bottom plate provided below at least one of the energy storage cells, and a bottom wall provided below the bottom plate, the bottom wall which defines a smoke exhaust path together with the bottom plate and the bottom wall, A method for manufacturing a lower case, wherein, in the step described above, a core for forming the exhaust path is placed in a pair of molds that are separable from each other, and a metal material for forming the bottom plate and the bottom wall is supplied into the gap between the pair of molds and the core.

6. The method for manufacturing a lower case according to claim 5, wherein the core used in the above step includes a protrusion for forming a through hole at a position opposite to a safety valve provided on the lower surface of the at least one energy storage cell.

7. The method for manufacturing a lower case according to claim 5, wherein the pair of molds used in the above step are connected to the bottom plate and the bottom wall and capable of forming a peripheral wall that surrounds at least one energy storage cell.

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