power storage device

Abstract

The power storage device of the present disclosure includes a power storage element, a bottomed cylindrical case that houses the power storage element and has an opening at one end, and a closure that seals the opening. The case has a first pressing portion that presses a side surface of the closure and protrudes toward an inner side of the case, and a second pressing portion that presses an upper surface of the closure, near the opening. The closure has a slit in the upper surface. The slit extends more toward an inner side in a radial direction of the case than the second pressing portion and opens in a side surface of the closure.

Description

Technical Field

[0001] This disclosure relates to energy storage devices. Background Technology

[0002] Conventionally, a known energy storage device (e.g., an electrolytic capacitor) comprises: an energy storage element; a bottom-shaped casing housing the energy storage element; and a sealing body that seals the opening of the casing. In such energy storage devices, there are cases where a groove, such as a cross-shaped groove, is formed on the bottom surface of the casing as an explosion-proof mechanism. The strength of the bottom of this groove is weaker than its periphery. Therefore, when the internal pressure of the casing rises, the casing cracks starting from this groove, and the gas inside the casing escapes through the crack. This prevents the sealing part of the energy storage device from rupturing.

[0003] To ensure the reliable operation of the explosion-proof mechanism constructed from the groove, safety allowable values ​​are set between the permissible internal pressure of the housing and the operating pressure of the explosion-proof mechanism, and between the operating pressure of the explosion-proof mechanism and the sealing strength. However, if the sealing body deteriorates, the sealing strength of the energy storage device decreases, thus reducing the internal pressure of the housing when the seal breaks. On the other hand, the internal pressure of the housing remains constant when the explosion-proof mechanism constructed from the groove operates. Therefore, depending on the deterioration state of the sealing body, there is a drawback that the seal may break before the explosion-proof mechanism operates.

[0004] On the other hand, the energy storage device proposed in Patent Document 1 has a groove or slit extending from one of its upper edge and lower edge to the other on the side of the sealing body. This groove or slit is normally closed, but opens when the internal pressure of the housing rises abnormally, thereby functioning as an explosion-proof mechanism for venting gas from the housing.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: JP Patent No. 6191015 Summary of the Invention

[0008] However, in Patent Document 1, the slot or slit extends from the upper edge to the lower edge of the sealing body. Therefore, there is a concern that the sealing body may open even if the internal pressure of the casing does not increase significantly over time, due to factors such as the deterioration of the sealing body over the years. In other words, the explosion-proof mechanism of Patent Document 1 is designed with a risk of reduced operational reliability over time. Under these circumstances, one of the objectives of this disclosure is to provide an energy storage device with an explosion-proof mechanism that can maintain high operational reliability.

[0009] One aspect of this disclosure relates to an energy storage device. The energy storage device comprises: an energy storage element; a housing having a bottom cylindrical shape to house the energy storage element and having an opening at one end; and a sealing body to seal the opening, wherein the housing has a first pressing portion and a second pressing portion near the opening, the first pressing portion pressing against a side of the sealing body and protruding inwards from the housing, the second pressing portion pressing against an upper surface of the sealing body, and the sealing body having a slit on its upper surface, the slit extending radially inwards from the housing than the second pressing portion and opening on a side of the sealing body.

[0010] According to this disclosure, it is possible to obtain an energy storage device with an explosion-proof mechanism that can maintain high operational reliability. Attached Figure Description

[0011] Figure 1 This is a schematic cross-sectional view through a slit, representing an example of an energy storage device according to this disclosure.

[0012] Figure 2 It is a schematic top view representing the sealed body.

[0013] Figure 3 This is an enlarged sectional view of the main parts of the energy storage device when the internal pressure of the casing increases. Detailed Implementation

[0014] The following examples illustrate implementations of the energy storage devices involved in this disclosure. However, this disclosure is not limited to the examples described below. Specific values ​​and materials may be exemplified in the following description, but other values ​​and materials may also be applied as long as the effects of this disclosure are achieved.

[0015] (Electronic storage devices)

[0016] The energy storage device disclosed herein includes energy storage elements, a casing, and a sealing body. These will be described below.

[0017] (Electricity storage element)

[0018] Energy storage elements include electrodes, electrolytes, etc. For example, in the case of an energy storage device that is an electrolytic capacitor, the energy storage element includes a winding body. The winding body is formed by winding a pair of electrodes together with a separator in between. The pair of electrodes can both be polarized electrodes, or one can be an anode and the other a cathode. For example, in the case of an energy storage device that is a secondary battery or a lithium-ion capacitor, the energy storage element includes an electrode assembly. The electrode assembly is formed by winding a positive electrode and a negative electrode together with a separator in between. The energy storage element may also include an electrolyte or a liquid component.

[0019] (case)

[0020] The casing is a bottomed cylindrical shape with an opening at one end, and it houses the energy storage elements. The casing can be made of metals such as aluminum, iron, and nickel. The shape of the casing is not particularly limited, but it can be, for example, a bottomed cylindrical shape.

[0021] (Sealing body)

[0022] The sealing element seals the opening of the shell. The sealing element is made of an elastic material (e.g., a material containing an elastic resin). The shape of the sealing element can correspond to the shape of the shell. For example, if the shell is a bottomed cylindrical shape, the sealing element can be a circular plate; if the shell is a bottomed square cylindrical shape, the sealing element can be a square plate.

[0023] As an elastic resin, a rubber component is desirable. As a rubber component, butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber (EPDM), chloroprene rubber (CR), isoprene rubber (IR), Hypalon rubber, silicone rubber, fluororubber, etc., can be used alone or in combination. Among these, butyl rubber, ethylene propylene rubber, and fluororubber are particularly desirable. Besides elastic resins, elastic materials can also contain fillers, carbon black, processing aids, crosslinking aids, etc., as any component.

[0024] The aforementioned housing has a first pressing part and a second pressing part near the opening.

[0025] The first pressing part presses against the side of the sealing body and protrudes into the inside of the shell. The inner diameter of the most prominent apex of the first pressing part can be smaller than the outer diameter of the sealing body in the unloaded state. The first pressing part can also be formed, for example, by slotting a portion of the opening into a narrower diameter.

[0026] The second pressing part is positioned at one end of the housing, i.e., the opening side, which is closer to the first pressing part than the first pressing part, and presses the edge of the sealing body toward the inside of the housing. The second pressing part may also be formed, for example, by curling a portion of the outermost end of the opening.

[0027] A slit is formed on the upper surface of the sealing body. The slit extends radially inward into the shell beyond the second pressing part. The slit opens on the side of the sealing body. Alternatively, the slit may open only on the side of the sealing body, in a region slightly above the most prominent apex of the first pressing part (the opening side). The slit does not open on the lower surface of the sealing body (the inner surface of the shell). The slit may also allow communication between the inside and outside of the shell if an increase in the internal pressure of the shell causes the force acting from the sealing body on the first pressing part to fall below a predetermined value.

[0028] Here, if the internal pressure of the housing increases, the sealing body expands axially outward from the housing. During this axial expansion, the area of ​​the sealing body that contacts the first pressing part shifts away from the first pressing part, thus weakening the force (elastic repulsion relative to compression) acting from the sealing body towards the first pressing part. If this force weakens to below a predetermined value, gas inside the housing passes between the sealing body and the first pressing part. This gas is then discharged from inside the housing to the outside through a slit, reducing the internal pressure of the energy storage device and ensuring safety.

[0029] Thus, the slit in the energy storage device of this disclosure does not open or close according to the pressure inside the casing. This differs from the slot or slit in the energy storage device of Patent Document 1. Alternatively, the slit in the energy storage device of this disclosure is always open. Therefore, the problem of the slit opening when the sealing body deteriorates over time, as seen in Patent Document 1, is avoided. In other words, even if the sealing body deteriorates over time, the function of the explosion-proof mechanism of the slit in this disclosure will not be substantially impaired.

[0030] As described above, according to this disclosure, an energy storage device equipped with an explosion-proof mechanism capable of maintaining high operational reliability can be obtained. Furthermore, according to this disclosure, by operating the explosion-proof mechanism, unintended breakage of the energy storage device, such as the scattering of sealing components, can be prevented.

[0031] Multiple slits can also be provided. When multiple slits are provided, they can be arranged at equal intervals around the circumference of the housing. This suppresses asymmetrical deformation of the sealing body, improving the operational reliability of the explosion-proof mechanism formed by the slits.

[0032] Hereinafter, an example of an energy storage device according to this disclosure will be specifically described with reference to the accompanying drawings. The structural elements described above can be applied to the structural elements of the energy storage device of the example described below. The structural elements of the energy storage device of the example described below can be modified based on the above description. Furthermore, the matters described below can also be applied to the above-described embodiments. Non-essential structural elements in the energy storage device of the example described below, and those not required in the energy storage device according to this disclosure, may also be omitted. Additionally, the figures shown below are schematic and do not accurately reflect the actual shape and number of components.

[0033] like Figure 1 As shown, the energy storage device 10 is configured as an electrolytic capacitor, and includes an energy storage element 11, a housing 20, and a sealing body 30.

[0034] The energy storage element 11 includes a winding body. The winding body is formed by winding an anode foil and a cathode foil together with a spacer in between. One end of the anode foil and the cathode foil are respectively connected to a lead connector 12A and a lead connector 12B. The winding body is configured to wind the lead connectors 12A and 12B into the winding body. At the other end of the lead connectors 12A and 12B, leads 13A and 13B are respectively connected.

[0035] The housing 20 is a bottomed cylindrical shape with an opening 21 at one end, and it houses the energy storage element 11. The housing 20 of this embodiment is made of aluminum, but is not limited to this. The housing 20 of this embodiment is a bottomed cylindrical shape, but is not limited to this. The axial length of the housing 20, before the formation of the first pressing part 22 and the second pressing part 23 (described later), can be, for example, 60 to 80 mm. The outer diameter of the housing 20 can be, for example, 16 to 20 mm.

[0036] The sealing body 30 seals the opening 21 of the housing 20. In this embodiment, the sealing body 30 is circular, but it is not limited to this. The thickness of the sealing body 30 (the axial length of the housing 20) can be, for example, 3 to 7 mm. The sealing body 30 may also contain an elastomer primarily composed of rubber.

[0037] The opening 21 of the housing 20 has a first pressing part 22 and a second pressing part 23.

[0038] The first pressing part 22 is located near the opening 21, presses against the side of the sealing body 30, and protrudes towards the inside of the housing 20. The inner diameter of the apex 22a of the first pressing part 22 is smaller than the outer diameter of the sealing body 30 in the unloaded state. In this embodiment, the first pressing part 22 is formed by slotting a portion of the opening 21 to reduce its diameter, but it is not limited to this.

[0039] The second pressing part 23 is disposed at one end of the housing 20 (i.e., the opening side) closer to the first pressing part 22 than the first pressing part 22, and presses the edge of the sealing body 30. In other words, the second pressing part 23 presses the upper surface 30a of the sealing body 30 near the opening 21. In this embodiment, the second pressing part 23 is formed by curling a portion of the opening 21, but it is not limited to this.

[0040] like Figure 1 as well as Figure 2 As shown, a slit 31 is formed on the upper surface 30a of the sealing body 30. The slit 31 extends radially inward beyond the second pressing part 23 into the housing 20, communicating with the external space of the housing 20. For example, the slit 31 may extend radially inward by 0.2 to 2.0 mm beyond the radially inward end of the second pressing part 23. The slit 31 extends radially along the housing 20. However, the slit 31 may not extend radially along the housing 20.

[0041] The slit 31 opens on the side of the sealing body 30. Here, the slit 31 opens only on the side of the sealing body 30 in an area slightly above the position of the most prominent apex 22a of the first pressing part 22. The apex 22a of the first pressing part 22 is a crucial part for ensuring the airtightness of the housing 20; from the viewpoint of ensuring this airtightness, it is advantageous that the slit 31 does not open at this location. The slit 31 does not open on the lower surface of the sealing body 30.

[0042] like Figure 2 As shown, in this embodiment, four slits 31 are provided, but the number of slits 31 can be three or less, or five or more. The four slits 31 are arranged at equal intervals (90° apart in this example) around the circumference of the housing 20. However, multiple slits 31 can also be arranged at unequal intervals. Furthermore, in Figure 2 The through holes for passing through lead connectors 12A and 12B are omitted from the illustration.

[0043] The portion of the first pressing portion 22 further from the opening 21 on the opening side may also partially contact the sealing body 30. That is, a gap may exist between the inner surface of the opening 21 and the side surface of the sealing body 30 further from the opening 22 on the opening side than the vertex 22a of the first pressing portion 22. In the presence of this gap, the slit 31 may also communicate with this gap.

[0044] The distance from the upper surface of the sealing body 30 to the vertex 22a of the first pressing part 22 is defined as D. The depth of the slit 31 (the length in the direction parallel to the axial direction of the housing 20) can be, for example, 0.25×D to 0.9×D. In this embodiment, this distance D can be, for example, 2 to 5 mm. The width of the slit 31 (the circumferential length of the housing 20) can be, for example, 0.2 to 0.5 mm.

[0045] When the force exerted by the sealing body 30 on the first pressing part 22 is lower than a predetermined value due to the increased internal pressure of the housing 20, the slit 31 connects the inside and outside of the housing 20. On the other hand, when the force is higher than the predetermined value, the slit 31 does not connect the inside and outside of the housing 20.

[0046] Here, as Figure 3As shown, if the internal pressure of the housing 20 increases, the sealing body 30 expands axially outward from the housing 20. During this axial expansion, the area of ​​the sealing body 30 that contacts the first pressing part 22 shifts away from the first pressing part 22 (i.e., radially inward), thus weakening the force (elastic repulsive force against compression) acting from the sealing body 30 towards the first pressing part 22. If this force weakens to below a predetermined value, gas inside the housing 20 passes between the sealing body 30 and the first pressing part 22. This gas is discharged from inside the housing 20 to outside the housing 20 via the slit 31, thereby ensuring the safety of the energy storage device 10.

[0047] Example

[0048] For the energy storage devices 10 of Examples 1 to 3 and Comparative Examples 1 and 2 shown below, the relationship between the depth of the slit 31 and the operating pressure of the explosion-proof mechanism was measured. Here, the operating pressure of the explosion-proof mechanism refers to the internal pressure of the housing 20 when the internal pressure of the housing 20 rises and the inside and outside of the housing 20 are connected through the slit 31.

[0049] Example 1

[0050] The outer diameter of the aluminum housing 20 is set to 18 mm, the axial length of the housing 20 before forming the first pressing part 22 and the second pressing part 23 is set to 70 mm, and the axial distance from the upper surface 30a of the sealing body 30 to the apex 22a of the first pressing part 22 is set to 3.5 mm. The thickness of the butyl rubber sealing body 30 is set to 7 mm, and the outer diameter of the sealing body 30 before compression is set to 17.1 mm. The width of the slit 31 is set to 0.3 mm, and the depth of the slit 31 is set to 1.11 mm. The operating pressure of the explosion-proof mechanism is 2.15 MPa.

[0051] Example 2

[0052] The depth of slit 31 is set to 2.56 mm, and the rest of the structure is the same as in Example 1. The operating pressure of the explosion-proof mechanism is 1.94 MPa.

[0053] Example 3

[0054] The depth of slit 31 is set to 3.20 mm, and the rest of the structure is the same as in Example 1. The operating pressure of the explosion-proof mechanism is 1.86 MPa.

[0055] Comparative Example 1

[0056] The depth of slit 31 is set to 3.87 mm, and the rest of the structure is the same as in Example 1. The operating pressure of the explosion-proof mechanism is 0.42 MPa.

[0057] Comparative Example 2

[0058] The depth of slit 31 is set to 5.09 mm, and the rest of the structure is the same as in Example 1. The operating pressure of the explosion-proof mechanism is 0.19 MPa.

[0059] As described above, a significant difference in the operating pressure of the explosion-proof mechanism can be observed between Examples 1-3 and Comparative Examples 1 and 2. Since a higher operating pressure is preferred to achieve the desired operation, Examples 1-3 demonstrate their superiority.

[0060] Industrial availability

[0061] This disclosure can be used in energy storage devices.

[0062] -Symbol Explanation-

[0063] 10: Energy storage equipment

[0064] 11: Energy Storage Elements

[0065] 12A, 12B: Lead wire connectors

[0066] 13A, 13B: Lead wires

[0067] 20: Shell

[0068] 21: Opening

[0069] 22: First pressing part

[0070] 22a: Vertex

[0071] 23: Second pressing part

[0072] 30: Sealing body

[0073] 30a: Upper surface

[0074] 31: Slit.

Claims

1. An energy storage device, comprising: Energy storage elements; A cylindrical housing containing the energy storage element, having an opening at one end; and A sealing body that seals the opening, the sealing body comprising an elastic resin. The housing has a first pressing part and a second pressing part near the opening. The first pressing part presses against the side of the sealing body and protrudes towards the inside of the housing. The second pressing part presses against the upper surface of the sealing body. The sealing body has a slit on its upper surface. The slit extends further radially inward than the second pressing portion and opens on the side of the sealing body. The sealing body is configured such that, due to the increase in internal pressure of the housing, at least a portion of the lower surface of the sealing body on the opposite side of the upper surface is maintained below the first pressing portion, and the first pressing portion deforms to form a gap between the side surface of the sealing body and the inner surface of the housing, thereby discharging gas from the housing to the outside.

2. The energy storage device according to claim 1, wherein, The slit opens on the side of the sealing body only in an area higher than the position of the most prominent vertex of the first pressing part.

3. The energy storage device according to claim 1 or 2, wherein, The sealing body has a plurality of slits that serve as the slits.

4. The energy storage device according to claim 3, wherein, The plurality of slits are arranged at equal intervals around the circumference of the housing.

5. The energy storage device according to claim 1, wherein, The energy storage device also includes: an anode lead connector and a cathode lead connector, which are respectively connected to the anode and cathode of the energy storage element and pass through the sealing body.

6. The energy storage device according to claim 1, wherein, The shell is made of aluminum, iron, or nickel.

7. The energy storage device according to claim 1, wherein, The entire area of ​​the upper surface of the sealing body, excluding the area covered by the shell and the slit, is in contact with the second pressing part. At a position higher than the most prominent vertex of the first pressing part, there is a gap between the side of the sealing body and the inner surface of the housing.

8. The energy storage device according to claim 1, wherein, The entire area of ​​the upper surface of the sealing body, excluding the area covered by the shell and the slit, is in contact with the second pressing part. In a cross-section containing the center of the sealing body and the center of the energy storage element, there exists an empty area surrounded by the second pressing portion, the portion of the housing above the position of the most prominent vertex of the first pressing portion, and the side surface of the sealing body.

9. The energy storage device according to claim 1, wherein, The slit extends radially inward by more than 0.2 mm and less than 2.0 mm beyond the radially inner end of the second pressing part.

10. The energy storage device according to claim 1, wherein, When the distance from the upper surface of the sealing body to the position of the most prominent vertex of the first pressing part is set as D, the depth of the slit is 0.25×D or more and 0.9×D or less.

11. The energy storage device according to claim 1, wherein, When the distance from the upper surface of the sealing body to the position of the most prominent vertex of the first pressing part is set as D, the depth of the slit is (1.11 / 3.5)×D or more and 0.9×D or less.

12. The energy storage device according to claim 1, wherein, The sealing body is configured such that, due to the increase in internal pressure of the housing, the upper surface of the sealing body deforms protruding outward from the housing.

13. The energy storage device according to claim 1, wherein, The sealing body is configured such that, due to the increase in internal pressure of the housing, the lower surface of the sealing body deforms protruding outward from the housing.

14. The energy storage device according to claim 1, wherein, The lead connector is connected to the energy storage element. The lead wire is connected to the lead wire connector and is thinner than the lead wire connector. The lead connector protrudes from the sealing body.

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