Electricity storage device and method for manufacturing the same

Abstract

The disclosed power storage device is equipped with a power storage element 11, a bottomed cylindrical case 20 that accommodates the power storage element 11 and that has an opening 21 at one end, and a sealing body 30 that seals the opening 21. The case 20 is provided with: a first pressing part 22 in the vicinity of the opening 21, the first pressing part 22 pressing the side surface of the sealing body 30 and projecting toward the inner side of the case 20; and gas release parts 24, 26 provided nearer to one end side of the case 20 than the farthest-projecting apex 22a of the first pressing part 22. This makes it possible to provide a power storage device comprising an explosion-preventing mechanism which has high operating reliability and in which air-tightness is not impaired.

Description

[Technical Field]

[0001] The present disclosure relates to an electricity storage device and a method for manufacturing an electricity storage device. [Background technology]

[0002] Conventionally, there has been known an electricity storage device (specifically, an electrolytic capacitor) that includes an electricity storage element, a cylindrical case with a bottom that houses the electricity storage element, and a sealing body that seals the opening of the case (for example, Patent Document 1). The electricity storage device of Patent Document 1 has a constricted portion formed near the opening of the case that compresses the sealing body, and a hole or slit is provided at the point where the diameter of the constricted portion is smallest. This hole or slit functions as an explosion-proof mechanism that allows gas inside the case to escape when the internal pressure of the case increases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jikko No. 59-40767 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the location of the narrowed portion with the smallest diameter is the location that is most important for compressing the sealing body, i.e., for ensuring the airtightness of the electricity storage device. In Patent Document 1, a hole or slit is provided in that location, which may impair the airtightness of the electricity storage device. On the other hand, if some kind of explosion-proof mechanism is not provided, there is a risk that the sealing body will pop out and cause an electrical short circuit if the internal pressure of the case increases. In this situation, one of the objects of the present disclosure is to provide an electricity storage device with an explosion-proof mechanism that has high operational reliability and does not impair airtightness. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to an electricity storage device including: an electricity storage element; a cylindrical case that houses the electricity storage element and has an opening at one end; and a sealing body that seals the opening, wherein the case includes a first pressing portion that presses against a side surface of the sealing body and protrudes inward of the case near the opening; and a gas vent portion that is provided closer to the one end than the most protruding apex of the first pressing portion. [Effects of the Invention]

[0006] According to the present disclosure, an electricity storage device having an explosion-proof mechanism that has high operational reliability and does not impair airtightness can be obtained.

[0007] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present application, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of an electricity storage device according to a first embodiment of the present disclosure, taken along a cross section passing through a through hole. [Figure 2] 4 is an enlarged cross-sectional view showing a main part of the electricity storage device of Embodiment 1 when the internal pressure of the case increases. FIG. [Figure 3] 10 is a cross-sectional view schematically illustrating an example of an electricity storage device according to a second embodiment of the present disclosure, taken along a cross section passing through a slit. [Figure 4] FIG. 10 is an enlarged cross-sectional view showing a main part of the electricity storage device of Embodiment 2 when the internal pressure of the case increases. [Figure 5] 10 is a cross-sectional view schematically illustrating an example of an electricity storage device according to a third embodiment of the present disclosure, taken along a cross section passing through a through hole. [Figure 6] FIG. 10 is a side view schematically showing a case of an electricity storage device according to a third embodiment. [Figure 7] FIG. 10 is an enlarged cross-sectional view showing a main part of the electricity storage device of Embodiment 3 when the internal pressure of the case increases. [Figure 8] FIG. 11 is an enlarged cross-sectional view illustrating a hole-punching step in a method for manufacturing an electricity storage device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of an electricity storage device and a method for manufacturing an electricity storage device according to the present disclosure will be described below using examples. However, the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0010] The electricity storage device according to the present disclosure includes an electricity storage element, a cylindrical case with a bottom that houses the electricity storage element and has an opening at one end, and a sealing body that seals the opening. The case includes a first pressing portion that presses against the side of the sealing body near the opening and protrudes inward of the case, and a gas vent portion that is provided on the one end side of the most protruding apex of the first pressing portion. The gas vent portion has, for example, a through-hole or a slit. A protrusion that protrudes inward of the case may be formed on the periphery of the through-hole. The electricity storage device according to the present disclosure may have, for example, the configuration of electricity storage devices A, B, and C below, but is not particularly limited.

[0011] (Electricity storage device A) An electricity storage device according to one embodiment of the present disclosure (hereinafter referred to as electricity storage device A) includes an electricity storage element, a case, and a sealing body, which will be described below.

[0012] (storage element) The electricity storage element includes electrodes, an electrolyte, and the like. For example, when the electricity storage device A is an electrolytic capacitor, the electricity storage element includes a wound body. The wound body is formed by winding a pair of electrodes with a separator interposed therebetween. Both of the pair of electrodes may be polarizable electrodes, or one may be an anode and the other a cathode. For example, when the electricity storage device A is a secondary battery or a lithium ion capacitor, the electricity storage element includes an electrode group. The electrode group is formed by winding a positive electrode and a negative electrode with a separator interposed therebetween. The electricity storage element may further include an electrolyte or a liquid component.

[0013] (case) The case has a cylindrical shape with a bottom and an opening at one end, and houses the electricity storage element. The case may be made of a metal such as aluminum, iron, or nickel. The shape of the case is not particularly limited, and may be, for example, a cylindrical shape with a bottom.

[0014] (sealing body) The gasket seals the opening of the case. The gasket is made of an elastic material (e.g., a material containing an elastic resin). The shape of the gasket may correspond to the shape of the case. For example, if the case is cylindrical with a bottom, the gasket may be disk-shaped, and if the case is rectangular with a bottom, the gasket may be rectangular plate-shaped.

[0015] The elastic resin is preferably a rubber component. Examples of rubber components that can be used alone or in blends include butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber, ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), isoprene rubber (IR), Hypalon rubber, silicone rubber, and fluororubber. Among these, butyl rubber, ethylene propylene rubber, and fluororubber are preferred. In addition to the elastic resin, the elastic material may also contain optional components such as fillers, carbon black, processing aids, and crosslinking aids.

[0016] The case has a first pressing portion and a second pressing portion near the opening, and a through-hole (gas vent portion) is formed between the first pressing portion and the second pressing portion.

[0017] The first pressing portion presses against the side surface of the sealing body and protrudes toward the inside of the casing. The inner diameter of the first pressing portion at its most protruding apex may be smaller than the outer diameter of the sealing body when no load is applied. The first pressing portion may be formed, for example, by groove cutting to reduce the diameter of a portion of the opening.

[0018] The second pressing portion is disposed closer to one end of the case than the first pressing portion, i.e., closer to the opening, and presses the edge of the sealing body toward the inside of the case. The second pressing portion may be formed, for example, by curling a portion of the outermost end of the opening.

[0019] The through hole is provided closer to one end of the case than the most protruding apex of the first pressing portion, i.e., closer to the opening. The through hole may provide communication between the inside and outside of the case when the force acting on the first pressing portion from the sealing body falls below a predetermined value due to an increase in the internal pressure of the case. The through hole may be provided only on the one end side of the case than the apex of the first pressing portion. Only one through hole may be provided, or multiple through holes may be provided.

[0020] When the internal pressure of the case increases, the sealing body expands in the axial direction of the case toward the outside of the case. When this axial expansion occurs, the area of ​​the sealing body that is in contact with the first pressing portion is displaced away from the first pressing portion, thereby weakening the force (elastic repulsive force against compression) acting from the sealing body on the first pressing portion. When this acting force weakens below a predetermined value, gas inside the case passes between the sealing body and the first pressing portion. This gas escapes from inside the case to the outside through the through-hole, reducing the internal pressure of the power storage device A and ensuring safety.

[0021] Unlike the holes or slits in the electricity storage device of Patent Document 1, the through-holes in the electricity storage device A of the present disclosure are not provided at the apex of the first pressing portion, but are provided closer to one end of the case than the apex, i.e., closer to the opening. In other words, no through-holes are provided at the apex of the first pressing portion, which is an important location for ensuring the airtightness of the electricity storage device. Therefore, the airtightness of the electricity storage device A is not substantially impaired by the through-holes.

[0022] As described above, according to one embodiment of the present disclosure, an electricity storage device A is obtained that is equipped with an explosion-proof mechanism that has high operational reliability and does not impair airtightness. Furthermore, according to one embodiment of the present disclosure, operation of the explosion-proof mechanism can prevent unexpected explosion of the electricity storage device A, such as scattering of the sealing body, etc.

[0023] The through hole may be located closer to the top surface of the sealing body than the midpoint between the top surface of the sealing body and the most protruding apex of the first pressing portion in the axial direction of the case. With this configuration, the through hole is located sufficiently far from the apex of the first pressing portion. In other words, no through hole is present at or near the apex of the first pressing portion. This makes it even more difficult for the airtightness of the power storage device A to be impaired.

[0024] The through hole may be circular or elliptical. This configuration prevents stress from concentrating locally at the edge of the through hole when the internal pressure of the case increases, making it less likely that damage to the case will originate from the through hole.

[0025] The through-hole may be polygonal. With this configuration, the through-hole is formed using a polygonal needle or the like, which makes it easier to form the through-hole. Examples of polygonal shapes include, but are not limited to, triangles and rectangles.

[0026] (Electricity storage device B) An electricity storage device according to another embodiment of the present disclosure (hereinafter referred to as electricity storage device B) includes an electricity storage element, a case, and a sealing body, which will be described below.

[0027] (storage element) The power storage element may be the same as the power storage element of the power storage device A.

[0028] (case) The case may be the same as the case of the power storage device A.

[0029] (sealing body) The sealing member may be the same as the sealing member of the electricity storage device A.

[0030] The opening of the case has a first pressing portion and a slit (gas vent portion).

[0031] The first pressing portion presses against the side surface of the sealing body near the opening and protrudes inward of the case. The inner diameter of the first pressing portion at its most protruding apex may be smaller than the outer diameter of the sealing body when no load is applied. The first pressing portion may be formed, for example, by groove cutting to reduce the diameter of a portion of the opening.

[0032] The slit is provided closer to one end of the case than the most protruding apex of the first pressing portion, i.e., closer to the opening. The slit may provide communication between the inside and outside of the case when the force acting on the first pressing portion from the sealing body falls below a predetermined value due to an increase in internal pressure of the case. The slit may be provided only on the one end of the case than the apex of the first pressing portion. Only one slit or multiple slits may be provided.

[0033] When the internal pressure of the case increases, the sealing body expands in the axial direction of the case toward the outside of the case. When this axial expansion occurs, the area of ​​the sealing body that is in contact with the first pressing portion is displaced away from the first pressing portion, thereby weakening the force (elastic repulsive force against compression) acting from the sealing body on the first pressing portion. When this acting force weakens below a predetermined value, gas inside the case passes between the sealing body and the first pressing portion. This gas escapes from inside the case to the outside through the slit, reducing the internal pressure of the power storage device B and ensuring safety.

[0034] Unlike the holes or slits in the electricity storage device of Patent Document 1, the slits in the electricity storage device B of the present disclosure are not provided at the apex of the first pressing portion, but are provided closer to one end of the case than the apex, i.e., closer to the opening. In other words, no slits are provided at the apex of the first pressing portion, which is an important location for ensuring the airtightness of the electricity storage device. Therefore, the airtightness of the electricity storage device B is not substantially impaired by the slits.

[0035] As described above, according to another embodiment of the present disclosure, an electricity storage device B is obtained that is equipped with an explosion-proof mechanism that has high operational reliability and does not impair airtightness. Furthermore, according to another embodiment of the present disclosure, operation of the explosion-proof mechanism can prevent unexpected explosion of the electricity storage device B, such as scattering of the sealing body, etc.

[0036] The slit does not have to be disposed at the apex of the first pressing portion. The slit does not have to be disposed in the first pressing portion.

[0037] The sealing member may be made of an elastic body whose main component is rubber, and the rubber may constitute 50% or more by mass of the elastic body.

[0038] The case may further include a second pressing portion near the opening that presses against the top surface of the sealing body, thereby further improving the airtightness of the electricity storage device B.

[0039] The slit may extend to one end of the case, which makes it easier to form the slit.

[0040] The tip of the slit may be located closer to the end face of the sealing body in the axial direction of the case than the midpoint between the end face (top face) of the sealing body facing outward from the case and the apex of the first pressing portion. With this configuration, the tip of the slit is located sufficiently far from the apex of the first pressing portion. In other words, there is no slit at or near the apex of the first pressing portion. This makes it even more difficult for the airtightness of the electricity storage device B to be impaired.

[0041] (Electricity storage device C) An electricity storage device according to yet another embodiment of the present disclosure (hereinafter referred to as electricity storage device C) includes an electricity storage element, a case, and a sealing body, which will be described below.

[0042] (storage element) The power storage element may be the same as the power storage element of the power storage device A.

[0043] (case) The case may be the same as the case of the power storage device A.

[0044] (sealing body) The sealing member may be the same as the sealing member of the electricity storage device A.

[0045] The case has a first pressing portion and a second pressing portion near the opening, and a through-hole (gas vent portion) is formed between the first pressing portion and the second pressing portion.

[0046] The first pressing portion presses against the side surface of the sealing body and protrudes toward the inside of the case. The inner diameter of the first pressing portion at its most protruding apex may be smaller than the outer diameter of the sealing body when no load is applied. The first pressing portion may be formed, for example, by groove cutting to reduce the diameter of a portion of the opening.

[0047] The second pressing portion is disposed closer to one end of the case than the first pressing portion, i.e., closer to the opening, and presses the edge of the sealing body toward the inside of the case. The second pressing portion may be formed, for example, by curling a portion of the outermost end of the opening.

[0048] The through hole is provided closer to one end of the case than the most protruding apex of the first pressing portion, i.e., closer to the opening. The through hole may provide communication between the inside and outside of the case when the force acting on the first pressing portion from the sealing body falls below a predetermined value due to an increase in the internal pressure of the case. The through hole may be provided only on the one end side of the case than the apex of the first pressing portion. Only one through hole may be provided, or multiple through holes may be provided.

[0049] When the internal pressure of the case increases, the sealing body expands in the axial direction of the case toward the outside of the case. When this axial expansion occurs, the area of ​​the sealing body that is in contact with the first pressing portion is displaced away from the first pressing portion, thereby weakening the force (elastic repulsive force against compression) acting from the sealing body on the first pressing portion. When this acting force weakens below a predetermined value, gas inside the case passes between the sealing body and the first pressing portion. This gas escapes from inside the case to the outside through the through-hole, reducing the internal pressure of the power storage device C and ensuring safety.

[0050] Unlike the holes or slits in the electricity storage device of Patent Document 1, the through-holes in the electricity storage device C of the present disclosure are not provided at the apex of the first pressing portion, but are provided closer to one end of the case than the apex, i.e., closer to the opening. In other words, no through-holes are provided at the apex of the first pressing portion, which is an important location for ensuring the airtightness of the electricity storage device. Therefore, the airtightness of the electricity storage device C is not substantially impaired by the through-holes.

[0051] Furthermore, in the energy storage device C of the present disclosure, a protrusion that protrudes toward the inside of the case is formed on the periphery of the through hole. The presence of this protrusion prevents the sealing body from blocking the through hole. That is, even if the sealing body deforms and approaches the through hole, the protrusion abuts against the side of the sealing body, preventing the through hole from being completely blocked. The tip of the protrusion is not continuous around the entire circumference of the through hole. This ensures communication between the inside and outside of the case via the through hole even when the sealing body abuts against the protrusion. The through hole may be polygonal (triangle, square, etc.), and the protrusion may be formed along each side of the polygon. The length of the protrusion may be, for example, 30% or more of the maximum diameter of the through hole.

[0052] (Manufacturing Method of Electricity Storage Device C) The method for manufacturing the electricity storage device C according to the present disclosure includes a housing step, a sealing preparation step, a sealing completion step, and a perforation step. These steps will be described below. The housing step and the sealing preparation step may be performed simultaneously.

[0053] In the housing step, the electricity storage element is housed in a case. For example, when the electricity storage device C is an electrolytic capacitor, the wound body included in the electricity storage element is housed in the case so that the axial direction of the wound body substantially coincides with the axial direction of the case.

[0054] In the sealing preparation step, a sealing body is placed at the opening of the case. The sealing body may be placed so as to contact the inner surface of the case, or so as not to contact the inner surface of the case.

[0055] In the sealing completion step, a first pressing portion and a second pressing portion are formed to seal the opening of the case. The first pressing portion may be formed, for example, by groove cutting to reduce the diameter of a portion of the opening. The second pressing portion may be formed, for example, by curling a portion of the opening. The first pressing portion and the second pressing portion may be formed in the order listed above, or may be formed substantially simultaneously. Alternatively, the formation of the second pressing portion may begin halfway through the formation of the first pressing portion.

[0056] In the perforation step, after the sealing completion step, a through hole and a protrusion are formed in the case between the first pressing portion and the second pressing portion. In the perforation step, the through hole may be formed by piercing the case with the tip of a sharp tool (for example, a needle). The tip of the tool may be polygonal pyramid-shaped. If the tip of the tool is polygonal pyramid-shaped (triangular pyramid, quadrangular pyramid, etc.), the protrusion can be formed stably.

[0057] As described above, the present disclosure provides an electricity storage device C with an explosion-proof mechanism that has high operational reliability and does not impair airtightness, and a method for manufacturing the same. Furthermore, the present disclosure also provides an electricity storage device C that can be prevented from unexpectedly exploding, causing the sealing body or the like to fly off, by operating the explosion-proof mechanism.

[0058] An example of an electricity storage device and a method for manufacturing an electricity storage device according to the present disclosure will be described in detail below with reference to the drawings. The above-described components and steps can be applied to the components and steps of the example electricity storage device and the method for manufacturing an electricity storage device described below. The components and steps of the example electricity storage device and the method for manufacturing an electricity storage device described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Of the components and steps of the example electricity storage device and the method for manufacturing an electricity storage device described below, components and steps that are not essential to the electricity storage device and the method for manufacturing an electricity storage device according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0059] First Embodiment A first embodiment of the present disclosure will be described. As shown in Fig. 1, an electricity storage device 10 of this embodiment is configured as an electrolytic capacitor, and includes an electricity storage element 11, a case 20, and a sealing body 30.

[0060] The electricity storage element 11 includes a wound body. The wound body is formed by winding an anode foil and a cathode foil with a separator interposed therebetween. One end of lead tabs 12A and 12B are connected to the anode foil and the cathode foil, respectively. The wound body is formed by winding the lead tabs 12A and 12B. The other end of the lead tabs 12A and 12B are connected to lead wires 13A and 13B, respectively.

[0061] The case 20 has a cylindrical shape with a bottom and an opening 21 at one end, and houses the electricity storage element 11. The case 20 of this embodiment is made of aluminum, but is not limited to this. The case 20 of this embodiment has a cylindrical shape with a bottom, but is not limited to this. The axial length of the case 20 may be, for example, 60 to 80 mm before the first pressing portion 22 and the second pressing portion 23 described below are formed. The outer diameter of the case 20 may be, for example, 16 to 20 mm.

[0062] The sealing body 30 seals the opening 21 of the case 20. The sealing body 30 of this embodiment has a disk shape, but is not limited to this. The thickness of the sealing body 30 (the length in the axial direction of the case 20) may be, for example, 3 to 7 mm. The sealing body 30 may be made of an elastic body containing rubber as a main component. The rubber may constitute 50% by mass or more of the elastic body.

[0063] The opening 21 of the case 20 has a first pressing portion 22 and a second pressing portion 23 near the opening 21, and a through hole 24 is formed between the second pressing portion 23 and the first pressing portion 22. The through hole 24 is an example of a gas vent portion.

[0064] First pressing portion 22 presses against the side surface of sealing body 30 and protrudes inside case 20. The inner diameter of first pressing portion 22 at apex 22a is smaller than the outer diameter of sealing body 30 when no load is applied. In this embodiment, first pressing portion 22 is formed by grooving to reduce the diameter of a portion of opening 21, but the present invention is not limited to this.

[0065] Second pressing portion 23 is disposed closer to one end of case 20 (i.e., the opening side) than first pressing portion 22, and presses the edge of sealing body 30. In other words, second pressing portion 23 presses upper surface 30a of sealing body 30 in the vicinity of opening 21. Second pressing portion 23 in this embodiment is formed by curling a portion of opening 21, but is not limited to this.

[0066] The through hole 24 is provided closer to one end of the case 20 (i.e., closer to the opening) than the vertex 22a of the first pressing portion 22. In other words, the through hole 24 is not located at the vertex 22a of the first pressing portion 22. The through hole 24 is located closer to the end surface 30a of the sealing body 30 in the axial direction of the case 20 than the midpoint MP between the end surface (top surface) 30a of the sealing body 30 facing the outside of the case 20 and the vertex 22a of the first pressing portion 22. A portion of the opening 21 closer to the opening than the vertex 22a of the first pressing portion 22 may not be in partial contact with the sealing body 30. In other words, a gap may exist between the inner surface of the opening 21 and the side surface of the sealing body 30 on the opening side than the vertex 22a of the first pressing portion 22. The through hole 24 in this embodiment has a circular shape, but is not limited thereto. For example, the through hole 24 may have a polygonal shape.

[0067] The distance from one end of case 20 before second pressing portion 23 is formed to the center of through hole 24 (the distance in a direction parallel to the axial direction of case 20) may be, for example, 0.25×D to 0.9×D, where D is the distance from one end of case 20 before second pressing portion 23 is formed to vertex 22a of first pressing portion 22. In this embodiment, the distance D may be, for example, 2 to 8 mm. The diameter of through hole 24 may be, for example, 0.5 to 2 mm.

[0068] Through hole 24 provides communication between the inside and outside of case 20 when the force acting from sealing body 30 on first pressing portion 22 falls below a predetermined value due to an increase in the internal pressure of case 20. On the other hand, through hole 24 does not provide communication between the inside and outside of case 20 when the acting force is equal to or greater than the predetermined value.

[0069] 2, when the internal pressure of the case 20 increases, the sealing body 30 expands in the axial direction of the case 20 toward the outside of the case 20. When this axial expansion occurs, the area of ​​the sealing body 30 that is in contact with the first pressing portion 22 is displaced in a direction away from the first pressing portion 22 (i.e., radially inward), thereby weakening the force (elastic repulsive force against compression) acting from the sealing body 30 on the first pressing portion 22. When this acting force weakens to a value below a predetermined value, gas inside the case 20 passes between the sealing body 30 and the first pressing portion 22. This gas escapes from inside the case 20 to outside the case 20 through the through-holes 24, thereby ensuring the safety of the electricity storage device 10.

[0070] Second Embodiment A second embodiment of the present disclosure will be described below. As shown in Fig. 3, an electricity storage device 10 of this embodiment is configured as an electrolytic capacitor and includes an electricity storage element 11, a case 20, and a sealing body 30.

[0071] The electricity storage element 11 may be the same as that in the first embodiment.

[0072] The case 20 may be the same as that in the first embodiment.

[0073] The sealing body 30 may be the same as that in the first embodiment.

[0074] The opening 21 of the case 20 has a first pressing portion 22, a second pressing portion 23, and a slit 26. The slit 26 is an example of a gas vent portion.

[0075] First pressing portion 22 presses the side surface of sealing body 30 near opening 21 and protrudes inward of case 20. The inner diameter of first pressing portion 22 at apex 22a is smaller than the outer diameter of sealing body 30 when no load is applied. In this embodiment, first pressing portion 22 is formed by grooving to reduce the diameter of a portion of opening 21, but the present invention is not limited to this.

[0076] Second pressing portion 23 is disposed closer to one end of case 20 (i.e., the opening side) than first pressing portion 22, and presses the edge of sealing body 30. In other words, second pressing portion 23 presses upper surface 30a of sealing body 30 in the vicinity of opening 21. Second pressing portion 23 in this embodiment is formed by curling a portion of opening 21, but is not limited to this.

[0077] The slit 26 is provided closer to one end of the case 20 (i.e., closer to the opening) than the vertex 22a of the first pressing portion 22. In other words, the slit 26 is not located at the vertex 22a of the first pressing portion 22. The slit 26 is formed from one end of the case 20 to a predetermined position between the one end of the case 20 and the vertex 22a of the first pressing portion 22. The tip of the slit 26 is located closer to the end surface 30a of the sealing body 30 in the axial direction of the case 20 than the midpoint MP between the end surface (top surface) 30a of the sealing body 30 facing outward from the case 20 and the vertex 22a of the first pressing portion 22. A portion of the opening 21 closer to the opening than the vertex 22a of the first pressing portion 22 may not be in contact with the sealing body 30. In other words, a gap may exist between the inner surface of the opening 21 and the side surface of the sealing body 30 on the opening side than the vertex 22a of the first pressing portion 22.

[0078] The length of slit 26 (the length in the direction parallel to the axial direction of case 20) may be, for example, 0.25×D to 0.9×D, where D is the distance from one end of case 20 before second pressing portion 23 is formed to vertex 22a of first pressing portion 22. In this embodiment, distance D may be, for example, 2 to 8 mm. The width of slit 26 (the length in the circumferential direction of case 20) may be, for example, 0.2 to 0.5 mm.

[0079] Slit 26 allows communication between the inside and outside of case 20 when the force acting from sealing body 30 on first pressing portion 22 falls below a predetermined value due to an increase in the internal pressure of case 20. On the other hand, slit 26 does not allow communication between the inside and outside of case 20 when the acting force is equal to or greater than the predetermined value.

[0080] 4, when the internal pressure of the case 20 increases, the sealing body 30 expands in the axial direction of the case 20 toward the outside of the case 20. When this axial expansion occurs, the area of ​​the sealing body 30 that is in contact with the first pressing portion 22 is displaced in a direction away from the first pressing portion 22 (i.e., radially inward), thereby weakening the force (elastic repulsive force against compression) acting from the sealing body 30 on the first pressing portion 22. When this acting force weakens to a value below a predetermined value, gas inside the case 20 passes between the sealing body 30 and the first pressing portion 22. This gas escapes from inside the case 20 to outside the case 20 through the slits 26, thereby ensuring the safety of the electricity storage device 10.

[0081] Third Embodiment A third embodiment of the present disclosure will be described. As shown in Figures 5 and 6, an electricity storage device 10 of this embodiment is configured as an electrolytic capacitor and includes an electricity storage element 11, a case 20, and a sealing body 30.

[0082] The electricity storage element 11 may be the same as that in the first embodiment.

[0083] The case 20 may be the same as that in the first embodiment.

[0084] The sealing body 30 may be the same as that in the first embodiment.

[0085] The opening 21 of the case 20 has a first pressing portion 22 and a second pressing portion 23 near the opening 21, and a through hole 24 is formed between the second pressing portion 23 and the first pressing portion 22. The through hole 24 is an example of a gas vent portion.

[0086] First pressing portion 22 presses against the side surface of sealing body 30 and protrudes inside case 20. The inner diameter of first pressing portion 22 at apex 22a is smaller than the outer diameter of sealing body 30 when no load is applied. In this embodiment, first pressing portion 22 is formed by grooving to reduce the diameter of a portion of opening 21, but the present invention is not limited to this.

[0087] Second pressing portion 23 is disposed closer to one end of case 20 (i.e., the opening side) than first pressing portion 22, and presses the edge of sealing body 30. In other words, second pressing portion 23 presses upper surface 30a of sealing body 30 in the vicinity of opening 21. Second pressing portion 23 in this embodiment is formed by curling a portion of opening 21, but is not limited to this.

[0088] The through hole 24 is provided closer to one end of the case 20 (i.e., closer to the opening) than the vertex 22a of the first pressing portion 22. In other words, the through hole 24 is not located at the vertex 22a of the first pressing portion 22. The portion of the opening 21 closer to the opening than the vertex 22a of the first pressing portion 22 may not be in partial contact with the sealing body 30. In other words, a gap may exist between the inner surface of the opening 21 and the side surface of the sealing body 30 on the opening side than the vertex 22a of the first pressing portion 22. The through hole 24 in this embodiment has a rectangular shape, but the shape is not limited thereto. For example, the through hole 24 may have a circular shape or a polygonal shape other than a rectangular shape.

[0089] The distance from one end of case 20 before second pressing portion 23 is formed to the center of through hole 24 (the distance in a direction parallel to the axial direction of case 20) may be, for example, 0.25×D to 0.9×D, where D is the distance from one end of case 20 before second pressing portion 23 is formed to vertex 22a of first pressing portion 22. In this embodiment, the distance D may be, for example, 2 to 8 mm. The diameter of through hole 24 (the diameter of the circumscribed circle of through hole 24) may be, for example, 0.5 to 2 mm.

[0090] Through hole 24 provides communication between the inside and outside of case 20 when the force acting from sealing body 30 on first pressing portion 22 falls below a predetermined value due to an increase in the internal pressure of case 20. On the other hand, through hole 24 does not provide communication between the inside and outside of case 20 when the acting force is equal to or greater than the predetermined value.

[0091] 7, when the internal pressure of the case 20 increases, the sealing body 30 expands in the axial direction of the case 20 toward the outside of the case 20. When this axial expansion occurs, the area of ​​the sealing body 30 that is in contact with the first pressing portion 22 is displaced in a direction away from the first pressing portion 22 (i.e., radially inward), thereby weakening the force (elastic repulsive force against compression) acting from the sealing body 30 on the first pressing portion 22. When this acting force weakens to a value below a predetermined value, gas inside the case 20 passes between the sealing body 30 and the first pressing portion 22. This gas escapes from inside the case 20 to outside the case 20 through the through-holes 24, thereby ensuring the safety of the electricity storage device 10.

[0092] As shown in FIGS. 5 and 6 , the electricity storage device 10 has protrusions 25 formed on the periphery of the through hole 24 that protrude toward the inside of the case 20. In this embodiment, four triangular protrusions 25 are formed along each side of the rectangular through hole 24. The width of each protrusion 25 narrows from the base end to the tip. Therefore, the tip of the protrusion 25 is not continuous around the entire circumference of the through hole 24. Each protrusion 25 may be formed at the same time as forming the through hole 24 in the case 20.

[0093] The presence of the protrusions 25 prevents sealing body 30 from blocking through-hole 24. That is, even if sealing body 30 deforms and approaches through-hole 24, protrusions 25 abut against the side surface of sealing body 30, preventing through-hole 24 from being completely blocked (see, for example, FIG. 7).

[0094] (Method of manufacturing an electricity storage device) A description will be given of a method for manufacturing the above-described electricity storage device 10. The manufacturing method includes an accommodation step, a sealing preparation step, a sealing completion step, and a perforation step.

[0095] In the accommodation step, the electricity storage element 11 is accommodated in the case 20. In this embodiment, since the electricity storage device 10 is an electrolytic capacitor, the wound body included in the electricity storage element 11 is accommodated in the case 20 so that the axial direction of the wound body substantially coincides with the axial direction of the case 20.

[0096] In the sealing preparation step, sealing body 30 is placed in opening 21 of case 20. Sealing body 30 may be placed so as to contact the inner surface of case 20, or may be placed so as not to contact the inner surface of case 20.

[0097] In the sealing completion step, the first pressing portion 22 and the second pressing portion 23 are formed. The first pressing portion 22 is formed by groove cutting, which reduces the diameter of a portion of the opening 21. The second pressing portion 23 is formed by curling a portion of the opening 21. In this embodiment, the process starts with the formation of the first pressing portion 22, and then begins the formation of the second pressing portion 23 halfway through the formation of the first pressing portion 22. In this way, the opening 21 of the case 20 is sealed.

[0098] The perforation process is performed after the sealing completion process. In the perforation process, a through hole 24 and a protrusion 25 are formed between the first pressing portion 22 and the second pressing portion 23 in the case 20. In the perforation process of this embodiment, as shown in FIG. 8, the through hole 24 is formed by piercing the case 20 with the tip of a needle 40. The tip of this needle 40 has a quadrangular pyramid shape. The needle 40 is an example of a sharp tool. [Example]

[0099] The relationship between the position of the through-hole 24 and the operating pressure of the explosion-proof mechanism was measured for the electricity storage devices 10 of Examples 1 to 5 and Comparative Example 1 shown below. Here, the operating pressure of the explosion-proof mechanism refers to the internal pressure of the case 20 at which the inside and outside of the case 20 communicate with each other via the through-hole 24 as the internal pressure of the case 20 increases. The electricity storage devices 10 of Examples 1 to 5 correspond to the above-mentioned Embodiment 1.

[0100] Example 1 The outer diameter of the aluminum case 20 was 18 mm, the axial length of the case 20 before the formation of the first pressing portion 22 and the second pressing portion 23 was 70 mm, and the distance from one end of the case 20 before the formation of the second pressing portion 23 to the apex 22a of the first pressing portion 22 was 4.5 mm. The thickness of the butyl rubber sealing body 30 was 5 mm, and the outer diameter of the sealing body 30 before compression was 17.1 mm. The diameter of the through hole 24 was 1 mm, and the distance from one end of the case 20 before the formation of the second pressing portion 23 to the center of the through hole 24 (hereinafter simply referred to as the "distance to the through hole 24") was 1.1 mm. The operating pressure of the explosion-proof mechanism was 2.06 MPa.

[0101] Example 2 The distance to the through hole 24 was set to 1.73 mm, and the other configurations were the same as in Example 1. The operating pressure of the explosion-proof mechanism was 2.07 MPa.

[0102] Example 3 The distance to the through hole 24 was set to 2.22 mm, and the other configurations were the same as in Example 1. The operating pressure of the explosion-proof mechanism was 2.04 MPa.

[0103] Example 4 The distance to the through hole 24 was set to 2.59 mm, and the other configurations were the same as in Example 1. The operating pressure of the explosion-proof mechanism was 2.04 MPa.

[0104] Example 5 The distance to the through hole 24 was set to 3.33 mm, and the other configurations were the same as in Example 1. The operating pressure of the explosion-proof mechanism was 2.06 MPa.

[0105] Comparative Example 1 The distance to the through hole 24 was set to 4.26 mm, and the other configurations were the same as those in Example 1. In other words, a part of the through hole 24 was positioned closer to the other end of the case 20 than the apex 22a of the first pressing portion 22. The operating pressure of the explosion-proof mechanism was 1.12 MPa.

[0106] As described above, there was a difference of about two times in the operating pressure of the explosion-proof mechanism between Examples 1 to 5 and Comparative Example 1. Furthermore, the operating pressure of the explosion-proof mechanism was substantially constant in Examples 1 to 5. As long as the desired operation can be obtained, a higher operating pressure of the explosion-proof mechanism is preferable, and it can be said that Examples 1 to 5 demonstrate the superiority of the mechanism.

[0107] Furthermore, the relationship between the length of the slit 26 and the operating pressure of the explosion-proof mechanism was measured for the electricity storage devices 10 of Examples 6 to 9 and Comparative Example 2 shown below. Here, the operating pressure of the explosion-proof mechanism refers to the internal pressure of the case 20 when the inside and outside of the case 20 communicate with each other via the slit 26 as the internal pressure of the case 20 increases. The electricity storage devices 10 of Examples 6 to 9 correspond to the above-mentioned Embodiment 2.

[0108] Example 6 The outer diameter of the aluminum case 20 was 18 mm, the axial length of the case 20 before the formation of the first pressing portion 22 and the second pressing portion 23 was 70 mm, and the distance from one end of the case 20 before the formation of the second pressing portion 23 to the apex 22a of the first pressing portion 22 was 4.5 mm. The thickness of the butyl rubber sealing body 30 was 5 mm, and the outer diameter of the sealing body 30 before compression was 17.1 mm. The width of the slit 26 was 0.3 mm, and the length of the slit 26 was 1 mm. The operating pressure of the explosion-proof mechanism was 1.98 MPa.

[0109] Example 7 The length of the slit 26 was set to 2 mm, and the other configurations were the same as those in Example 6. The operating pressure of the explosion-proof mechanism was 1.87 MPa.

[0110] Example 8 The length of the slit 26 was set to 3 mm, and the other configurations were the same as those in Example 6. The operating pressure of the explosion-proof mechanism was 1.66 MPa.

[0111] Example 9 The length of the slit 26 was set to 4 mm, and the other configurations were the same as those in Example 6. The operating pressure of the explosion-proof mechanism was 1.58 MPa.

[0112] Comparative Example 2 The length of the slit 26 was set to 5 mm, and the other configurations were the same as those in Example 6. The operating pressure of the explosion-proof mechanism was 0.15 MPa.

[0113] As described above, a difference of about one order of magnitude was observed in the operating pressure of the explosion-proof mechanism between Examples 6 to 9 and Comparative Example 2. As long as the desired operation can be obtained, a higher operating pressure of the explosion-proof mechanism is preferable, and it can be said that Examples 6 to 9 demonstrate the superiority of the explosion-proof mechanism.

[0114] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention. [Industrial Applicability]

[0115] The present disclosure can be used in an electricity storage device and a method for manufacturing an electricity storage device. [Explanation of symbols]

[0116] 10: Energy storage device 11: Energy storage element 12A, 12B: Lead tab 13A, 13B: Lead wire 20: Case 21: Opening 22: First pressing part 22a: Vertex 23: Second pressing part 24: Through hole (gas vent) 25: Protrusion 26: Slit (gas vent) 30: Sealing body 30a: End surface (top surface) 40: Needle (tool) MP: Midway point

Claims

1. A storage element; a cylindrical case having a bottom and an opening at one end, the case housing the storage element; a sealing body that seals the opening, The case is a first pressing portion that presses a side surface of the sealing body near the opening and protrudes toward the inside of the case; a gas vent portion provided closer to the one end than the most protruding apex of the first pressing portion.

2. The power storage device according to claim 1 , wherein the gas vent portion has a through-hole.

3. 3. The energy storage device according to claim 2, wherein the through hole is positioned closer to the upper surface of the sealing body than a midpoint between the upper surface of the sealing body and the most protruding vertex of the first pressing portion in the axial direction of the case.

4. The electricity storage device according to claim 2 or 3, wherein the through-hole has a circular or elliptical shape.

5. The electricity storage device according to claim 2 or 3, wherein the through-hole is polygonal.

6. 6. The power storage device according to claim 1, wherein the case further includes a second pressing portion that presses against an upper surface of the sealing body near the opening.

7. The power storage device according to claim 6 , wherein the gas vent is provided between the first pressing portion and the second pressing portion of the case.

8. The power storage device according to claim 1 , wherein the gas vent portion has a slit.

9. The power storage device according to claim 8 , wherein the slits are not disposed at the vertices.

10. The electricity storage device according to claim 8 , wherein the sealing body is made of an elastic material containing rubber as a main component.

11. 11. The power storage device according to claim 8, wherein the case further comprises a second pressing portion that presses an upper surface of the sealing body near the opening.

12. The power storage device according to any one of claims 8 to 11, wherein the slit extends to the one end of the case.

13. The gas vent portion has a through hole, The power storage device according to claim 1 , wherein a protrusion that protrudes toward the inside of the case is formed on a peripheral edge of the through hole.

14. the through hole is polygonal; The power storage device according to claim 13 , wherein the protrusions are formed along each side of the polygon.

15. The power storage device according to claim 13 or 14, wherein the case further includes a second pressing portion that presses against an upper surface of the sealing body near the opening.

16. The power storage device according to claim 15 , wherein the gas vent is provided between the first pressing portion and the second pressing portion of the case.

17. A method for manufacturing the electricity storage device according to any one of claims 13 to 16, comprising: A method for manufacturing an electricity storage device, comprising a drilling step of forming the through hole by piercing the case with the tip of a sharp tool.

18. The method for manufacturing an electricity storage device according to claim 17 , wherein the tip of the tool has a polygonal pyramid shape.

19. A method for manufacturing the electricity storage device according to claim 15 or 16, comprising: a housing step of housing the electricity storage element in the case; a sealing preparation step of placing the sealing body in the opening; a sealing completion step of forming the first pressing portion and the second pressing portion; a drilling step of forming the through hole and the protrusion between the first pressing portion and the second pressing portion in the case after the sealing completion step; A method for manufacturing an electricity storage device, comprising:

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