Power storage device

Abstract

A power storage device 10 comprises a case 20, a power storage element 30, a belt-like lead 41, and an opening-sealing member 50. The opening-sealing member 50 is provided with: an insulating gasket 51 having a base part 53; and an electroconductive opening-sealing plate 56. The opening-sealing plate 56 has a displacement part 57. The displacement part 57 of the opening-sealing plate 56 and the lead 41 are electrically connected to each other. By displacement of the displacement part 57 in a direction separating away from the lead 41 in response to a rise in internal pressure inside the case 20, the displacement part 57 and the lead 41 are electrically disconnected from each other. The storage device 10 further comprises a displacement suppression means 43 that is disposed in the case 20 and that suppresses displacement of the lead 47 when the displacement part 57 is displaced in the direction separating away from the lead 41. Accordingly, the operation reliability in an electric current cutoff mechanism is enhanced.

Description

Power storage device

[0001] The present disclosure relates to an electricity storage device.

[0002] Conventionally, electric storage devices equipped with a so-called current interrupt device (CID) have been known (see, for example, Patent Document 1). The electric storage device of Patent Document 1 includes a cylindrical case with a bottom, an electric storage element disposed within the case, leads connected to electrodes of the electric storage element, and a sealing member that seals an opening of the case. The sealing member has an insulating gasket including a base and a conductive sealing plate including a protrusion, and the base is disposed between the sealing plate and the electric storage element. The protrusion of the sealing plate is inserted into a through hole formed in the base and connected to the lead. As a function of the current interrupt device, the protrusion is displaced away from the lead in response to an increase in internal pressure within the case, thereby severing the connection between the protrusion and the lead.

[0003] Japanese Patent Application Laid-Open No. 2021-125304

[0004] In the case of the current interruption device of Patent Document 1, in order to improve its operational reliability, it is required that the lead is less likely to displace when the protrusion is displaced. However, if the lead or the base of the gasket is deformed to a certain extent, the lead will also displace along with the protrusion, which may impair the operational reliability of the current interruption device. In this situation, one of the objectives of the present disclosure is to improve the operational reliability of the current interruption device.

[0005] One aspect of the present disclosure relates to a power storage device. The energy storage device includes a case having a cylindrical tube portion with an open end at one end and a bottom portion closing the other end of the tube portion, an energy storage element arranged within the case and including a pair of electrodes, a strip-shaped lead connected to one of the pair of electrodes, and a sealing member sealing the open end of the case, wherein the sealing member includes an insulating gasket and a conductive sealing plate, wherein the gasket has a compression portion interposed between the tube portion and the sealing plate and a base portion arranged between the sealing plate and the energy storage element, and the sealing plate has a displacement portion and an outer circumferential portion provided around the displacement portion and sandwiched between the compression portion, the displacement portion of the sealing plate and the lead are electrically connected, and when the displacement portion displaces in a direction away from the lead in response to an increase in internal pressure within the case, the electrical connection between the displacement portion and the lead is severed, and the device further includes a displacement suppression means arranged within the case for suppressing displacement of the lead when the displacement portion displaces in a direction away from the lead.

[0006] According to the present disclosure, the operational reliability of the current interruption mechanism can be improved.

[0007] While the novel features of the present disclosure are set forth in the appended claims, the present disclosure, 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.

[0008] FIG. 1 is a cross-sectional view schematically showing the configuration of an energy storage device of embodiment 1. FIG. 2 is a perspective view showing a main part of a first lead of embodiment 1. FIG. 3 is a cross-sectional view schematically showing the configuration of an energy storage device of a modified example of embodiment 1. FIG. 4 is a perspective view showing a main part of a first lead of embodiment 2. FIG. 5 is a cross-sectional view schematically showing the configuration of an energy storage device of embodiment 3. FIG. 6 is a cross-sectional view showing an enlarged main part of an energy storage device of embodiment 3. FIG. 7 is a bottom view of a sealing member of embodiment 3 as seen from the bottom side of the case. FIG. 8 is a bottom view of a sealing member of embodiment 4 as seen from the bottom side of the case. FIG. 9 is a bottom view of a sealing member of embodiment 5 as seen from the bottom side of the case.

[0009] An embodiment of the power 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 power storage device according to the present disclosure may be a secondary battery or a capacitor. The power storage device may be a non-aqueous electrolyte secondary battery (such as a lithium ion secondary battery or a lithium secondary battery) or a nickel-metal hydride secondary battery. The power storage device may be an electric double layer capacitor or a lithium ion capacitor. The power storage device includes a case, a power storage element, a strip-shaped lead, a sealing member, and a displacement suppression means.

[0011] The case has a cylindrical tube portion with an open end at one end and a bottom portion that closes the other end of the tube portion. The case may function as, for example, one of the electrode terminals. When the case functions as an electrode terminal, for example, the case may be made of a conductive metal, and one electrode of the energy storage element (an electrode that is not electrically connected to the sealing plate described below) may be electrically connected to the case. For example, the negative electrode may be electrically connected to the case.

[0012] The case may be, for example, a metal case. This metal case may be made of aluminum, iron, nickel, copper, or an alloy or clad material of these metals. The case for the power storage device is not limited to the above configuration, and any known case may be used.

[0013] The energy storage element is disposed in a case and includes a pair of electrodes, each consisting of a positive electrode and a negative electrode, facing each other with a separator interposed therebetween. The energy storage element may be, for example, a wound type energy storage element in which the positive electrode and negative electrode are stacked with a separator interposed therebetween and wound. The energy storage element is not particularly limited and may be selected depending on the type of energy storage device. Known energy storage elements can be used for the energy storage element. For example, when the energy storage device is a secondary battery, an energy storage element including a positive electrode, a negative electrode, a separator, and an electrolyte solution may be used. The negative electrode of an example lithium-ion secondary battery includes a substance that reversibly absorbs and releases lithium ions as a negative electrode active material. Examples of such negative electrode active materials include carbon materials such as graphite and inorganic compounds such as silicon and titanium oxide. The positive electrode of a lithium-ion secondary battery may include a lithium-containing transition metal composite oxide as a positive electrode active material. The transition metal composite oxide includes elements such as nickel, manganese, cobalt, and aluminum.

[0014] When the electricity storage device is a capacitor, an electricity storage element including at least a pair of electrodes, an electrolyte, and a separator may be used. These components can be selected depending on the type of capacitor.

[0015] The lead is connected to at least one of the pair of electrodes of the energy storage element. The lead electrically connects one of the electrodes connected at one end to a sealing member or a case at the other end. The lead may be a lead used in known energy storage devices. The lead may be a strip-shaped metal sheet. Examples of metals (conductive metals) constituting the lead include aluminum, iron, nickel, copper, or alloys or clad materials of these metals. One end of the lead may be connected to either of the pair of electrodes of the energy storage element, but when the energy storage device is a secondary battery, for example, the lead connected to the sealing member is connected to the positive electrode.

[0016] The sealing member seals the open end of the case and includes an insulating gasket and a conductive sealing plate.

[0017] The gasket has a compression portion interposed between the cylindrical portion of the case and the sealing plate, and a base portion disposed between the sealing plate and the energy storage element. The base portion may overlap the sealing plate. The shape of the base may be, for example, a disk shape, but is not limited thereto.

[0018] The gasket is made of a material having the elasticity and insulating properties required for functioning as a gasket. The gasket may be made of a known material used in gaskets for secondary batteries or capacitors. Examples of gasket materials include polypropylene (PP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), perfluoroalkoxyalanine (PFA), and polyether ether ketone (PEEK). Additives (e.g., known additives) may be added to these materials as needed. The method for forming the gasket is not limited, and the gasket may be formed by a method such as injection molding.

[0019] The sealing plate has a displacement portion and an outer peripheral portion that surrounds the displacement portion and is sandwiched between the compressed portions of the gasket. The displacement portion may be located at the center of the sealing plate. The displacement portion may have a protrusion that protrudes toward the energy storage element. The sealing plate may further have a thin-walled portion that connects the displacement portion and the outer peripheral portion and is thinner than the displacement portion and the outer peripheral portion. The sealing plate may be formed, for example, in a disk shape as a whole. The displacement portion may be circular or polygonal when viewed from the axial direction of the case. The outer peripheral portion that surrounds the displacement portion may be, for example, annular when viewed from the axial direction of the case, and the thin-walled portion may also be annular. The protrusion may be located, for example, at the center of the displacement portion. Note that the shape of the protrusion when viewed from the axial direction may be circular, oval, elliptical, rectangular, or polygonal. The sealing plate may function as an electrode terminal or as a displacement member that electrically connects an electrode terminal (e.g., a terminal cap) to a lead. The sealing plate is made of, for example, a metal plate, such as aluminum, nickel, copper, iron, or an alloy or clad material of these metals. Note that the protrusion and thin portion of the displacement portion are not necessarily required.

[0020] The displacement portion of the sealing plate and the lead are electrically connected. For example, the displacement portion and the lead may be indirectly connected via another member, or may be directly connected. There are no particular limitations on the method for indirectly or directly connecting the sealing plate and the lead, and welding, for example, may be used.

[0021] In the energy storage device of the present disclosure, the current interruption mechanism functions by displacing the displacement portion away from the lead in response to an increase in internal pressure within the case, thereby disconnecting the electrical connection between the displacement portion and the lead. This displacement may occur when the internal pressure within the case exceeds a predetermined value. When such displacement occurs, the displacement of the lead is suppressed by a displacement suppression means disposed within the case. The displacement portion is electrically disconnected from the lead whose displacement is suppressed, thereby allowing the current interruption mechanism to operate properly.

[0022] A through hole may be formed in the base. The through hole may be located in a central region of the base. The shape of the through hole is not particularly limited and may be, for example, circular, elliptical, oval, rectangular, polygonal, or the like. The lead may have a connection region in which at least one bent portion is formed as a displacement suppression means at at least one end in the width direction (short direction) of the lead. Such a connection region has higher rigidity against bending force than a connection region (connection portion with the displacement portion) of a conventional lead that does not have a bent portion. The bent portion may be formed at both ends in the width direction of the lead, or may be formed only at one end in the width direction of the lead. The displacement portion of the sealing plate and the connection region of the lead may be connected via a through hole in the base. That is, the lead may be electrically and physically connected to the sealing plate. The method of connecting the lead and the sealing plate is not particularly limited and may be, for example, welding. However, in order to function as a current interruption mechanism, the connection method must be such that the connection between the lead and the sealing plate is released when the force pulling the lead and the sealing plate apart becomes too large. In this case, the mechanism for breaking the connection between the lead and the displacement portion may be to break the welded portion between the lead and the displacement portion, or to provide a weak portion in the lead around the connection with the displacement portion, and to break this weak portion when the displacement portion is displaced. When the lead and the sealing plate are connected by welding, the force required to separate the lead and the sealing plate can be adjusted by changing conditions such as the weld area and weld depth. There are no particular limitations on the welding method, and laser welding, resistance welding, friction stirring, ultrasonic welding, etc. may be used.

[0023] In an energy storage device with this configuration, the current interruption mechanism functions by displacing the displacement portion away from the lead in response to an increase in internal pressure within the case, thereby severing the connection between the displacement portion and the lead. This displacement may occur when the internal pressure within the case exceeds a predetermined value. When such displacement occurs, the portion of the lead to which the displacement portion is connected, i.e., the connection region, has at least one bent portion formed therein. Therefore, the connection region is stronger and less likely to deform than the portion of the lead not having the bent portion formed therein. Therefore, even if the lead is pulled by the displacing displacement portion, the displacement of the lead is suppressed. The displacement portion is separated from the lead whose displacement is suppressed, thereby allowing the current interruption mechanism to operate properly.

[0024] At least one bent portion may have a crease along the longitudinal direction of the lead. Such a crease may be formed, for example, by cutting a slit in the lead and bending the lead along the longitudinal direction. This configuration makes it easy to ensure sufficient strength throughout the entire connection region in the longitudinal direction of the lead.

[0025] At least one bent portion may have a crease inclined with respect to the longitudinal direction of the lead. Such a crease may be formed, for example, by bending the lead along a straight line that approaches the end portion from the center of the lead in the width direction as the distance from the tip of the lead increases. With this configuration, at least one bent portion can be formed simply by bending the lead, thereby suppressing an increase in the number of steps required to manufacture the energy storage device.

[0026] The angle between at least one bent portion and the lead main surface may be greater than 0° and less than 180°. If the angle is within this range, the bent portion can effectively improve the lead strength. Furthermore, the angle is preferably greater than 45° and less than 135°, and more preferably greater than 85° and less than 95°. The angle may be, for example, 90°.

[0027] The at least one bent portion may include two bent portions. One bent portion may be located at one end of the lead in the width direction. The other bent portion may be located at the other end of the lead in the width direction. With this configuration, no bent portion is formed in the central region of the lead in the width direction, so that the central region can be used for connection with the displacement portion. Furthermore, by forming two bent portions, the strength of the connection region can be sufficiently increased.

[0028] In a direction perpendicular to the axial direction of the case, one end and the other end of the connection region may overlap the outer periphery of the sealing plate when viewed from the axial direction of the case. A base of the gasket may be sandwiched between one end of the connection region and the outer periphery, and between the other end of the connection region and the outer periphery. With this configuration, when the current-breaking mechanism is activated, the base is less likely to be deformed by the connection region of the lead, which is pulled in response to displacement of the displacement portion. This is because displacement of the one end and the other end of the connection region is suppressed by the outer periphery of the sealing plate, which is located on the opposite side of the base. This further improves the operational reliability of the current-breaking mechanism.

[0029] The energy storage device may further include a reinforcing member that reinforces the base as a displacement suppression means. The reinforcing member may be made of a material with higher rigidity than the constituent material of the gasket to reliably reinforce the gasket base. The reinforcing member may also be made of a material with higher rigidity than the lead, or may be made of the same material as the lead but thicker than the lead. The reinforcing member may be a conductive member, such as a metal (e.g., aluminum, iron, nickel, copper, stainless steel, etc.). The reinforcing member may also be made of an insulating resin with higher rigidity than the gasket. Examples of such insulating resins include polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), perfluoroalkoxyalanine (PFA), and polyether ether ketone (PEEK). The reinforcing member may be integrated with the gasket or its base, or may be separate. In the former case, the reinforcing member may be insert-molded together with the gasket, for example. In the latter case, the base may mechanically engage the reinforcing member, press the reinforcing member into a hole in the base, or fix the two together via an adhesive. When the reinforcing member is made of an insulating material, a through-hole or a notch may be formed in the reinforcing member, and the protrusion of the displacement portion may be inserted into the through-hole or notch and connected to the lead. The base may have at least one opening that covers a first portion of the main surface of the reinforcing member facing the energy storage device and exposes a second portion of the main surface. The second portion may be used for electrical connection between the displacement portion of the sealing plate and the lead. It is desirable that the first portion cover as much of the area of ​​the main surface of the reinforcing member facing the energy storage device as possible (e.g., 70% or more or 90% or more of the area) of the region other than the second portion. Furthermore, on the main surface of the base facing the energy storage device, the portion overlapping the reinforcing member may protrude toward the energy storage device beyond the portion not overlapping the reinforcing member. This configuration facilitates minimizing the thickness of the base. Furthermore, it is possible to suppress thickening of the compressed portion. Therefore, it is possible to prevent the sealing member from becoming large.

[0030] In an energy storage device with this configuration, the current interruption mechanism functions by displacing the displacement portion away from the lead in response to an increase in internal pressure within the case, thereby severing the electrical connection between the displacement portion and the lead. This displacement may occur when the internal pressure within the case exceeds a predetermined value. When such displacement occurs, the base of the gasket is reinforced by the reinforcing member and is therefore less likely to displace. Therefore, even if the lead is pulled due to this displacement, the lead abuts against the base of the gasket, thereby suppressing the displacement of the lead. The displacement portion is electrically disconnected from the lead whose displacement has been suppressed, thereby allowing the current interruption mechanism to operate properly.

[0031] Furthermore, in this energy storage device, the first portion of the reinforcing member is covered by the base of the gasket, making it difficult for the reinforcing member to move relative to the base. Because the base is fixed to the case, the reinforcing member is also difficult to move relative to the case. Therefore, when the current interruption mechanism operates, if the reinforcing member is conductive, it is possible to prevent the reinforcing member from moving within the case and coming into contact with the case or other components, resulting in a short circuit. Furthermore, even if the reinforcing member is made of an insulating material, the operation of the current interruption mechanism is likely to be stable.

[0032] When the reinforcing member is a conductive member, the displacement portion of the sealing plate and the reinforcing member may be connected by a first connection portion. The first connection portion may be provided at a central portion of the displacement portion and the reinforcing member. The reinforcing member and the lead may be connected by a second connection portion separate from the first connection portion. When the internal pressure in the case increases, the displacement portion may be displaced away from the lead, thereby severing the connection between the displacement portion and the reinforcing member, thereby severing the electrical connection between the displacement portion and the lead. In this configuration, the displacement portion of the sealing plate and the lead are indirectly connected via the conductive reinforcing member. The function of the current interruption mechanism is exerted when the connection between the displacement portion and the reinforcing member is severed, in other words, when the first connection portion breaks.

[0033] The first connection portion and the second connection portion may be spaced apart from each other in the radial direction of the case. This configuration makes it easy to form the first connection portion and the second connection portion separately under different conditions. Therefore, the connection strength of the first connection portion can be made lower than the connection strength of the second connection portion, making it easy to realize operation of the current interruption mechanism by fracture of the first connection portion. Note that the first connection portion and the second connection portion do not have to be spaced apart from each other in the radial direction of the case. In this case, the two connection portions may be integral with each other or separate from each other.

[0034] At least one opening may expose a second portion of the main surface at a position corresponding to the first connection portion and the second connection portion. This configuration allows the first connection portion and the second connection portion to be easily formed, for example, by welding, via the second portion exposed through the at least one opening. The at least one opening may include a first opening exposing the first connection portion and a second opening exposing the second connection portion, and the first opening and the second opening may be spaced apart from each other. This configuration allows the base to cover more of the reinforcing member that does not contribute to the first connection portion or the second connection portion, compared to a configuration in which the first and second connection portions are exposed through a single opening. This reduces the possibility of the reinforcing member coming into contact with other conductive members and causing a short circuit. Furthermore, by connecting the lead and the reinforcing member through the second opening, the periphery of the second opening serves to suppress lead displacement, facilitating connection between the lead and the reinforcing member.

[0035] The base may cover at least a portion of the main surface of the reinforcing member facing the sealing plate. That is, at least a portion of the base may be interposed between the sealing plate and the reinforcing member. This configuration allows the base to hold the reinforcing member from both axial sides. This allows the reinforcing member to be more firmly fixed to the base. Furthermore, if the reinforcing member is made of a conductive material, interposing a portion of the base between the reinforcing member and the sealing plate can prevent electrical connection between the sealing plate and the reinforcing member after the sealing plate operates as a current interruption mechanism. The main surface of the reinforcing member facing the sealing plate may be covered with an insulating member separate from the base.

[0036] As described above, according to the present disclosure, the operational reliability of the current interruption mechanism can be improved by suppressing displacement of the lead.

[0037] An example of a power storage device according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the example power storage device described below. The components of the example power storage device described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Of the components of the example power storage device described below, components that are not essential to the power 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.

[0038] First Embodiment A first embodiment of the present disclosure will be described. The power storage device 10 of this embodiment is a lithium ion secondary battery, but is not limited to this. For example, the power storage device 10 may be a lithium ion capacitor, an electric double layer capacitor, an intermediate power storage device between a lithium ion secondary battery and a lithium ion capacitor, or other electrochemical devices.

[0039] 1 and 2 , the energy storage device 10 includes a cylindrical case 20 with a bottom, an energy storage element 30 disposed within the case 20 and including a pair of electrodes (not shown), a first lead 41 connected to one of the pair of electrodes, a second lead 45 connected to the other electrode, and a sealing member 50 that seals the open end 21 a of the case 20. The energy storage device 10 further includes first and second insulating plates 61 and 62. The first and second insulating plates 61 and 62 are each a disk-shaped member having a through hole formed therein.

[0040] The case 20 has a cylindrical portion 21 having an open end 21a at one end (the upper end in FIG. 1 ) and a bottom portion 22 that closes the other end of the cylindrical portion 21. An annular groove 21b that protrudes radially inward of the cylindrical portion 21 is formed near the open end 21a of the cylindrical portion 21. The sealing member 50 is disposed on the inner circumferential surface of the groove 21b. The open end 21a of the case 20 is crimped to an outer circumferential portion 58 of a sealing plate 56 (described later) via a gasket 51 (described later). As a result, the sealing member 50 is sandwiched between the groove 21b and the open end 21a, sealing the case 20.

[0041] The energy storage element 30 has a generally cylindrical shape and is configured by winding a positive electrode and a negative electrode (not shown) with a separator (not shown) interposed therebetween.

[0042] One end of the first lead 41 is connected to one electrode (positive electrode in this example) of the energy storage element 30. The first lead 41 is made of a strip-shaped metal sheet, but is not limited to this. The other end of the first lead 41 is provided with a connection region 42 in which two bent portions 43 are formed. This connection region 42 is connected to the protrusion 57a ​​of the sealing plate 56. This allows the sealing plate 56 to function as the positive electrode terminal of the energy storage device 10. The first lead 41 is an example of a lead. The bent portion 43 is an example of a displacement suppression means.

[0043] 2, the connection region 42 has a bent portion 43 formed on each end of the first lead 41 in the width direction (the direction perpendicular to the plane of the paper in FIG. 1). Each bent portion 43 has a crease along the longitudinal direction of the first lead 41 (the left-right direction in FIG. 1). One bent portion 43 is disposed at one end of the first lead 41 in the width direction. The other bent portion 43 is disposed at the other end of the first lead 41 in the width direction. Each bent portion 43 can be formed by making a cut in the first lead 41 and bending the first lead 41 along the longitudinal direction.

[0044] In the width direction of the first lead 41, the ratio L2 / L1 of the dimension L2 of the portion of the connection region 42 used for connection with the protrusion 57a ​​(the portion not used as the bent portion 43) to the dimension L1 of the first lead 41 may be, for example, 0.2 to 0.8, or 0.3 to 0.7. In other words, in the width direction of the first lead 41, the ratio L3 / L1 of the dimension L3 of the portion of the connection region 42 used as the bent portion 43 to the dimension L1 of the first lead 41 may be, for example, 0.2 to 0.8, or 0.3 to 0.7. Here, L1 = L2 + L3 holds.

[0045] The two bent portions 43 may have the same or different shapes and dimensions. For example, the two bent portions 43 in this embodiment have shapes that are symmetrical with respect to a plane that is perpendicular to the main surface of the first lead 41 and passes through the center of the first lead 41, but two bent portions 43 that have shapes that are asymmetric with respect to the plane may also be provided.

[0046] The connection region 42 extends a predetermined length from the tip of the first lead 41. However, the connection region 42 may extend a predetermined length from a position some distance away from the tip of the first lead 41. In the latter case, the bent portion 43 is not formed at the tip of the first lead 41. In either case, the connection region 42 must be present in the portion of the first lead 41 to which the protrusion 57a ​​of the sealing plate 56 is connected.

[0047] One end of the second lead 45 is connected to the other electrode (negative electrode in this example) of the energy storage element 30. The second lead 45 is made of a strip-shaped metal sheet, but is not limited to this. The other end of the second lead 45 is connected to the bottom 22 of the case 20. This allows the case 20 to function as the negative electrode terminal of the energy storage device 10.

[0048] The sealing member 50 includes an insulating gasket 51 and a conductive sealing plate 56. The gasket 51 includes a compression portion 52 interposed between the cylindrical portion 21 (groove portion 21b) and the sealing plate 56, and a base portion 53 overlapping the sealing plate 56. The base portion 53 is disposed between the sealing plate 56 and the energy storage element 30. The base portion 53 has a planar shape that is approximately the same size as the planar shape (circular) of the sealing plate 56. An oval through-hole 53a is formed in the central region of the base portion 53. The peripheral edge of the base portion 53 and the outer periphery 58 of the sealing plate 56 are in close contact with each other. Note that the gasket 51 may have a through-hole (not shown) for supplying gas to the sealing plate 56, separate from the through-hole 53a through which the protrusion 57a ​​is inserted in the base portion 53.

[0049] The sealing plate 56 has a displacement portion 57 provided in the center thereof, an outer peripheral portion 58 provided around the displacement portion 57 and sandwiched between the compression portions 52 of the gasket 51, and a thin-walled portion 59 connecting the displacement portion 57 and the outer peripheral portion 58. The displacement portion 57 has a protrusion 57a ​​formed thereon that protrudes toward the energy storage element 30. The cross-sectional shape of the protrusion 57a ​​(the cross-sectional shape in a cross section perpendicular to the axial direction of the case 20) is oval, but is not limited to this. The thickness of the thin-walled portion 59 is smaller than the thickness of the displacement portion 57 and the thickness of the outer peripheral portion 58.

[0050] The protrusion 57a ​​of the sealing plate 56 is inserted into the through hole 53a. A gap may or may not be formed between the protrusion 57a ​​and the through hole 53a. As described above, the protrusion 57a ​​is connected to the connection region 42 of the first lead 41. In other words, the displacement portion 57 of the sealing plate 56 and the connection region 42 of the first lead 41 are connected via the through hole 53a.

[0051] When the internal pressure inside case 20 increases, protrusion 57a ​​of displacement portion 57 is displaced in a direction away from energy storage element 30 (i.e., in a direction away from first lead 41). On the other hand, displacement of first lead 41 is suppressed by connection region 42, which has high strength. Therefore, when the displacement of protrusion 57a ​​becomes large, the connection between protrusion 57a ​​and first lead 41 is severed. As a result, overcharging and the like are suppressed.

[0052] If the internal pressure of the case 20 increases further and the displacement of the displacement portion 57 becomes even greater, the thin-walled portion 59 or its peripheral portion will break, causing the gas inside the case 20 to be released to the outside of the case 20.

[0053] <<Modification of First Embodiment>> A modification of the first embodiment of the present disclosure will be described. The energy storage device 10 of this modification differs from the first embodiment in the configuration of the connection region 42. The following mainly describes the differences from the first embodiment.

[0054] As shown in FIG. 3 , the connection region 42 of this embodiment is longer than the connection region 42 of the first embodiment. Specifically, one end and the other end of the connection region 42 overlap the outer periphery 58 of the sealing plate 56 when viewed in the axial direction of the case 20 (when viewed from above in FIG. 3 ). In other words, one end and the other end of the connection region 42 are located outside the inner end of the outer periphery 58 of the sealing plate 56 in the radial direction of the case 20. The base 53 of the gasket 51 is sandwiched between one end of the connection region 42 and the outer periphery 58, and between the other end of the connection region 42 and the outer periphery 58. There may or may not be a gap between the connection region 42 of the first lead 41 and the base 53 of the gasket 51.

[0055] The gasket 51 has a side wall 54 disposed between the first lead 41 and the protruding end of the groove 21b. The side wall 54 may be provided, for example, only in the region where the first lead 41 and the groove 21b are close to each other, or may be provided along the entire periphery. The side wall 54 may protrude from the main surface of the base 53 facing the energy storage element 30 (the lower surface in FIG. 3 ) toward the energy storage element 30. The side wall 54 prevents the connection region 42 from contacting the inner surface of the case 20.

[0056] Second Embodiment A second embodiment of the present disclosure will be described. The power storage device 10 of this embodiment differs from the first embodiment in the configuration of the bent portion 43. The following mainly describes the differences from the first embodiment.

[0057] As shown in FIG. 4 , in the connection region 42 of this embodiment, one bent portion 43 is formed at each end in the width direction of the first lead 41. Each bent portion 43 has a fold that is inclined with respect to the longitudinal direction of the first lead 41. One bent portion 43 is disposed at one end in the width direction of the first lead 41. The other bent portion 43 is disposed at the other end in the width direction of the first lead 41. Each bent portion 43 can be formed by bending the first lead 41 along a pair of straight lines that are inclined with respect to the longitudinal direction. Here, the pair of straight lines may extend so as to approach each other from the base end side toward the tip end side of the first lead 41.

[0058] Third Embodiment A third embodiment of the present disclosure will be described. The power storage device 110 of this embodiment is a lithium ion secondary battery, but is not limited to this. For example, the power storage device 110 may be a lithium ion capacitor, an electric double layer capacitor, an intermediate power storage device between a lithium ion secondary battery and a lithium ion capacitor, or other electrochemical devices.

[0059] 5 to 7 , the energy storage device 110 includes a cylindrical case 120 with a bottom, an energy storage element 130 disposed within the case 120 and including a pair of electrodes (not shown), a first lead 141 connected to one of the pair of electrodes, a second lead 142 connected to the other electrode, a sealing member 150 that seals an open end 121 a of the case 120, and a reinforcing member 170. The energy storage device 110 further includes first and second insulating plates 161 and 162. The first and second insulating plates 161 and 162 are each a disk-shaped member having a through hole formed therein.

[0060] The case 120 has a cylindrical portion 121 having an open end 121a at one end (the upper end in FIG. 5 ) and a bottom portion 122 that closes the other end of the cylindrical portion 121. An annular groove 121b that protrudes radially inward of the cylindrical portion 121 is formed near the open end 121a of the cylindrical portion 121. The sealing member 150 is disposed on the inner circumferential surface of the groove 121b. The open end 121a of the case 120 is crimped to an outer circumferential portion 158 of a sealing plate 156 (described later) via a gasket 151 (described later). As a result, the sealing member 150 is sandwiched between the groove 121b and the open end 121a, sealing the case 120.

[0061] The energy storage element 130 has a generally cylindrical shape and is configured by winding a positive electrode and a negative electrode (not shown) with a separator (not shown) interposed therebetween.

[0062] One end of the first lead 141 is connected to one electrode (positive electrode in this example) of the energy storage element 130. The first lead 141 is made of a strip-shaped metal foil, but is not limited to this. The other end of the first lead 141 is connected to the reinforcing member 170. As will be described later, the reinforcing member 170 is connected to the sealing plate 156, and therefore the sealing plate 156 functions as the positive electrode terminal of the energy storage device 110. The first lead 141 is an example of a lead. The reinforcing member 170 is an example of a displacement suppression means.

[0063] One end of the second lead 142 is connected to the other electrode (negative electrode in this example) of the energy storage element 130. The second lead 142 is made of a strip-shaped metal foil, but is not limited to this. The other end of the second lead 142 is connected to the bottom 122 of the case 120. This allows the case 120 to function as the negative electrode terminal of the energy storage device 110.

[0064] The sealing member 150 includes an insulating gasket 151 and a conductive sealing plate 156. The gasket 151 has a compression portion 152 interposed between the cylindrical portion 121 (groove portion 121b) and the sealing plate 156, and a base portion 153 that is overlaid on the sealing plate 156. The base portion 153 is disposed between the sealing plate 156 and the energy storage element 130. The base portion 153 has a planar shape that is approximately the same size as the planar shape (circular) of the sealing plate 156. An oval insertion hole 153a is formed in the central region of the base portion 153. The peripheral edge of the base portion 153 and the outer periphery 158 of the sealing plate 156 are in close contact with each other.

[0065] A reinforcing member 170 is disposed inside the base 153. The base 153 covers the main surface of the reinforcing member 170 on the side opposite the energy storage element 130 (the upper side in FIG. 5 ), excluding an area where the insertion hole 153 a is formed. The base 153 has a first opening 153 c and a second opening 153 d that cover a first portion 170 a of the main surface of the reinforcing member 170 on the energy storage element 130 side (the lower side in FIG. 5 ) and expose a second portion 170 b of the main surface. The first opening 153 c is provided at a position corresponding to a first connecting portion 181 (described later) (in this example, the center position of the base 153). The second opening 153 d is provided at a position corresponding to a second connecting portion 182 (described later) and accommodates at least a portion of the other end of the first lead 141. The first opening 153c and the second opening 153d expose the main surface of the reinforcing member 170 facing the energy storage element 130 as the second portion 170b at the positions where they are arranged. The first opening 153c and the second opening 153d are each an example of at least one opening. On the main surface of the base 153 facing the energy storage element 130, the portion overlapping with the reinforcing member 170 protrudes toward the energy storage element 130 more than the portion not overlapping with the reinforcing member 170.

[0066] Sealing plate 156 has a displacement portion 157 provided in the center thereof, an outer peripheral portion 158 provided around displacement portion 157 and sandwiched between compression portions 152 of gasket 151, and a thin-walled portion 159 connecting displacement portion 157 and outer peripheral portion 158. Displacement portion 157 has a protrusion 157a formed thereon that protrudes toward energy storage element 130. The cross-sectional shape of protrusion 157a (the cross-sectional shape in a cross section perpendicular to the axial direction of case 120) is oval, but is not limited to this. The thickness of thin-walled portion 159 is smaller than the thickness of displacement portion 157 and outer peripheral portion 158.

[0067] The reinforcing member 170 is provided inside the base 153 to reinforce the base 153. The reinforcing member 170 is a conductive member, for example, made of metal. In this embodiment, the reinforcing member 170 is integrated with the gasket 151 by insert molding. The main surface of the reinforcing member 170 facing the energy storage element 130 (the lower surface in FIG. 5 ) has a first portion 170a exposed from the first opening 153c and the second opening 153d, and a second portion 170b covered by the base 153. As shown in FIG. 6 , the reinforcing member 170 is connected to the first lead 141 at the first portion 170a exposed from the second opening 153d by a second connection portion 182.

[0068] As shown in Fig. 7, reinforcing member 170 is formed in the shape of a rectangular plate. As shown in Fig. 6, in the radial direction of case 120, the outer end (longitudinal end) of reinforcing member 170 is located outward from the inner end of outer periphery 158 of sealing plate 156. Note that Figs. 5 and 6 are cross-sectional views of power storage device 110 taken along the longitudinal direction of reinforcing member 170.

[0069] Protrusion 157a of sealing plate 156 is inserted into insertion hole 153a. A gap may or may not be formed between protrusion 157a and insertion hole 153a. As shown in FIG. 6 , protrusion 157a (displacement portion 157) of sealing plate 156 is connected to reinforcing member 170 at first connection portion 181. As a result, displacement portion 157 of sealing plate 156 is electrically connected to first lead 141 via conductive reinforcing member 170.

[0070] 6 , a first connection portion 181 connecting the protrusion 157a and the reinforcing member 170 and a second connection portion 182 connecting the reinforcing member 170 and the first lead 141 are spaced apart from each other in the radial direction of the case 120. The bonding strength of the first connection portion 181 may be lower than the bonding strength of the second connection portion 182. The first connection portion 181 and the second connection portion 182 may be formed separately by, for example, laser welding. As an example, the first connection portion 181 may be formed by laser welding through the first opening 153c, and the second connection portion 182 may be formed by laser welding through the second opening 153d.

[0071] 7, a plurality of vent holes (through holes) 53b are formed in the base 153 of the gasket 151. The vent holes 153b communicate with the displacement portion 157 so that the internal pressure in the case 120 is transmitted to the displacement portion 157.

[0072] When the internal pressure inside case 120 increases, protrusion 157a of displacement portion 157 is displaced in a direction away from energy storage element 130 (i.e., in a direction away from reinforcing member 170 and first lead 141). On the other hand, the displacement of reinforcing member 170 and first lead 141 is suppressed by base portion 153, which is reinforced by reinforcing member 170. Therefore, when the displacement of protrusion 157a becomes large, the connection between protrusion 157a and reinforcing member 170 is severed. This breaks the electrical connection between displacement portion 157 and first lead 141, preventing overcharging and the like.

[0073] If the internal pressure in case 120 increases further and the displacement of displacement portion 157 becomes even greater, thin portion 159 or its peripheral portion will break, causing the gas inside case 120 to be released to the outside of case 120.

[0074] Fourth Embodiment A fourth embodiment of the present disclosure will be described. The power storage device 110 of this embodiment differs from the third embodiment in the shape of the reinforcing member 170. The following mainly describes the differences from the third embodiment.

[0075] 8, the reinforcing member 170 of this modified example is formed in the shape of a cross-shaped plate. With this configuration, the base portion 153 of the gasket 151 can be reinforced more effectively.

[0076] Fifth Embodiment A fifth embodiment of the present disclosure will be described. The power storage device 110 of this embodiment differs from the third embodiment in the shape of the reinforcing member 170. The following mainly describes the differences from the third embodiment.

[0077] 9, the reinforcing member 170 of this embodiment is formed in a disk shape. The reinforcing member 170 has a circular through-hole 170c formed in a position overlapping the air vent 153b. However, the shape of the through-hole 170c is not limited to a circular shape. With this configuration, the base 153 of the gasket 151 can be reinforced more effectively.

[0078] While the present disclosure has been described with respect to presently preferred embodiments, such disclosure should not be interpreted as limiting. Various variations and modifications will no doubt become apparent to those skilled in the art to which the present disclosure pertains upon reading the above disclosure. Accordingly, the appended claims should be interpreted to cover all variations and modifications without departing from the true spirit and scope of the present disclosure.

[0079] The present disclosure can be used in a power storage device.

[0080] 10: Energy storage device 20: Case 21: Cylindrical portion 21a: Opening end 21b: Groove portion 22: Bottom portion 30: Energy storage element 41: First lead (lead) 42: Connection region 43: Bent portion (displacement suppression means) 45: Second lead 50: Sealing member 51: Gasket 52: Compression portion 53: Base portion 53a: Through hole 54: Side wall portion 56: Sealing plate 57: Displacement portion 57a: Protrusion 58: Outer periphery 59: Thin portion 61: First insulating plate 62: Second insulating plate 110: Energy storage device 120: Case 121: Cylindrical portion 121a: Opening end 121b: Groove portion 122: Bottom portion 130: Energy storage element 141: First lead (lead) 142: Second lead 150: Sealing member 151: Gasket 152: Compression portion 153: Base portion 153a: Insertion hole 153b: Ventilation hole 153c: First opening (opening) 153d: Second opening (opening) 156: Sealing plate 157: Displacement portion 157a: Protrusion 158: Outer periphery 159: Thin portion 161: First insulating plate 162: Second insulating plate 170: Reinforcing member (displacement suppression means) 170a: First portion 170b: Second portion 170c: Through hole 181: First connecting portion 182: Second connecting portion

Claims

1. a case having a cylindrical tube portion with an open end at one end and a bottom portion closing the other end of the tube portion; an electricity storage element disposed in the case and including a pair of electrodes; a strip-shaped lead connected to one of the pair of electrodes; a sealing member that seals the open end of the case; Equipped with the sealing member includes an insulating gasket and a conductive sealing plate; the gasket has a compression portion interposed between the cylindrical portion and the sealing plate, and a base portion disposed between the sealing plate and the energy storage element, the sealing plate has a displacement portion and an outer circumferential portion provided around the displacement portion and sandwiched between the compression portion, the displacement portion of the sealing plate and the lead are electrically connected, When the internal pressure in the case increases, the displacement portion is displaced in a direction away from the lead, thereby cutting off the electrical connection between the displacement portion and the lead, The power storage device further comprises a displacement suppressing means disposed within the case, the displacement suppressing means suppressing displacement of the lead when the displacement portion is displaced in a direction away from the lead.

2. A through hole is formed in the base, the lead has a connection region in which at least one bent portion is formed as the displacement suppression means at at least one end of the lead in the width direction, The power storage device according to claim 1 , wherein the displacement portion of the sealing plate and the connection region of the lead are connected via the through hole.

3. The power storage device according to claim 2 , wherein the at least one bent portion has a crease along a longitudinal direction of the lead.

4. The power storage device according to claim 2 , wherein the at least one bent portion has a fold that is inclined with respect to a longitudinal direction of the lead.

5. the at least one folded portion includes two folded portions, one of the bent portions is disposed at one end of the lead in the width direction, 5. The power storage device according to claim 2, wherein the other bent portion is disposed at the other end of the lead in the width direction.

6. one end and the other end of the connection region overlap with the outer circumferential portion of the sealing plate when viewed in the axial direction of the case, The storage device according to any one of claims 2 to 4, wherein the base of the gasket is sandwiched between the one end of the connection region and the outer periphery, and between the other end of the connection region and the outer periphery.

7. The displacement suppressing means further includes a reinforcing member that reinforces the base portion, The energy storage device according to claim 1 , wherein the base portion has at least one opening that covers a first portion of a main surface of the reinforcing member that faces the energy storage device and exposes a second portion of the main surface.

8. the reinforcing member is a conductive member, the displacement portion of the sealing plate and the reinforcing member are connected by a first connection portion, the reinforcing member and the lead are connected at a second connection portion, 8. The energy storage device according to claim 7, wherein the displacement portion is displaced in a direction away from the lead in response to an increase in internal pressure within the case, thereby severing the connection between the displacement portion and the reinforcing member and thereby severing the electrical connection between the displacement portion and the lead.

9. The power storage device according to claim 8 , wherein the first connection portion and the second connection portion are spaced apart from each other in a radial direction of the case.

10. The power storage device according to claim 8 , wherein the at least one opening exposes, as the second portion, the main surface at a position corresponding to the first connection portion and the second connection portion.

11. the at least one opening includes a first opening exposing the first connection portion and a second opening exposing the second connection portion; The power storage device according to claim 10 , wherein the first opening and the second opening are spaced apart from each other.

12. The storage device according to any one of claims 7 to 9, wherein on the main surface of the base facing the storage element, the portion overlapping with the reinforcing member protrudes toward the storage element more than the portion not overlapping with the reinforcing member.

13. The power storage device according to any one of claims 7 to 9, wherein the base covers at least a part of a main surface of the reinforcing member on the sealing plate side.