Energy 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

Technical Field

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

Background Art

[0002] Conventionally, a power storage device provided with a so-called current interruption mechanism (CID) has been known (for example, Patent Document 1). The power storage device of Patent Document 1 includes a bottomed cylindrical case, a power storage element disposed in the case, a lead connected to an electrode of the power storage element, and a sealing member that seals an opening of the case. This sealing member has an insulating gasket including a base portion and a conductive sealing plate including a protrusion, and the base portion is disposed between the sealing plate and the power storage element. The protrusion of the sealing plate is inserted into a through hole formed in the base portion and is connected to the lead. As the function of the current interruption mechanism, when the internal pressure in the case rises, the protrusion is displaced in a direction away from the lead, so that the connection between the protrusion and the lead is broken.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of the current interruption mechanism of Patent Document 1, in order to improve its operation reliability, it is required that the lead is difficult to be displaced when the protrusion is displaced. However, when the base portions of the lead and the gasket are deformed to a certain extent, the lead is also displaced together with the protrusion, so that the operation reliability of the current interruption mechanism may be impaired. In such a situation, one of the objects of the present disclosure is to improve the operation reliability of the current interruption mechanism.

Means for Solving the Problems

[0005] One aspect of this disclosure relates to energy storage devices. The energy storage device comprises a case having a cylindrical tube portion with an open end at one end and a bottom portion that closes the other end of the tube portion, an energy storage element disposed inside the case and including a pair of electrodes, a strip-shaped lead connected to one of the pair of electrodes, and a sealing member that seals the open end of the case, wherein the sealing member comprises an insulating gasket and a conductive sealing plate, the gasket having a compression portion interposed between the tube portion and the sealing plate and a base portion disposed between the sealing plate and the energy storage element, the sealing plate having a displacement portion and an outer peripheral 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, the electrical connection between the displacement portion and the lead is broken when the displacement portion is displaced away from the lead in response to an increase in internal pressure inside the case, and the device further comprises displacement suppression means disposed inside the case and suppressing the displacement of the lead when the displacement portion is displaced away from the lead. [Effects of the Invention]

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

[0007] While novel features of this disclosure are described in the attached claims, this disclosure, in conjunction with other purposes and features of the application, will be better understood by the following detailed description with reference to the drawings, both in terms of structure and content. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing the configuration of the energy storage device of Embodiment 1. [Figure 2] This is a perspective view showing the main part of the first lead of Embodiment 1. [Figure 3] This is a schematic cross-sectional view showing the configuration of a modified energy storage device according to Embodiment 1. [Figure 4] This is a perspective view showing the main part of the first lead of Embodiment 2. [Figure 5]This is a schematic cross-sectional view showing the configuration of the energy storage device of Embodiment 3. [Figure 6] This is a cross-sectional view showing an enlarged view of the main part of the energy storage device of Embodiment 3. [Figure 7] This is a bottom view of the sealing member of Embodiment 3, as seen from the bottom of the case. [Figure 8] This is a bottom view of the sealing member of Embodiment 4, as seen from the bottom of the case. [Figure 9] This is a bottom view of the sealing member of Embodiment 5, as seen from the bottom of the case. [Modes for carrying out the invention]

[0009] An example of an embodiment of the energy storage device relating to this disclosure is described below. However, this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are achieved.

[0010] The energy storage device relating to this disclosure may be a secondary battery or a capacitor. The energy 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 energy storage device may be an electric double-layer capacitor or a lithium-ion capacitor. The energy storage device comprises a case, an energy storage element, a strip-shaped lead, a sealing member, and a displacement suppression means.

[0011] The case has a cylindrical section with an open end at one end and a bottom section that closes the other end of the cylindrical section. The case may function, for example, as 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 not electrically connected to the sealing plate described later) may be electrically connected to the case. For example, the negative electrode may be electrically connected to the case.

[0012] For the case, a metal case can be used, for example. This metal case may be made of aluminum, iron, nickel, copper, or alloys or clad materials of these metals. The case of the energy storage device is not limited to the above configuration, but any known case may be used.

[0013] The energy storage element includes a pair of electrodes, a positive electrode and a negative electrode, arranged within a case and facing each other via a separator. The shape of the energy storage element may be, for example, a wound-type energy storage element in which the positive and negative electrodes are wound together via a separator. There are no particular limitations on the energy storage element; it can be selected according to the type of energy storage device. Known energy storage elements can be used. For example, if the energy storage device is a secondary battery, an energy storage element including a positive electrode, a negative electrode, a separator, and an electrolyte may be used. The negative electrode of an example lithium-ion secondary battery includes a substance that reversibly intercepts and releases lithium ions as the negative electrode active material. This negative electrode active material may include, for example, carbon materials such as graphite, or inorganic compounds such as silicon or titanium oxide. The positive electrode of a lithium-ion secondary battery may include, as the positive electrode active material, a transition metal composite oxide containing lithium. This transition metal composite oxide may include, for example, elements such as nickel, manganese, cobalt, and aluminum.

[0014] If the energy storage device is a capacitor, an energy storage element comprising at least one pair of electrodes, an electrolyte, and a separator may be used. These components can be selected according to the type of capacitor.

[0015] The lead is connected to at least one of the pair of electrodes of the power storage element. The lead electrically connects one electrode connected at one end thereof to the sealing member or the case at the other end. As the lead, a lead used in a known power storage device may be used. A strip-shaped metal sheet may be used as the lead. Examples of the metal (conductive metal) constituting the lead include aluminum, iron, nickel, copper, or an alloy or clad material of these metals. One end of the lead may be connected to any of the pair of electrodes of the power storage element. However, when the power 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 portion of the case. The sealing member 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 power storage element. The base portion may be overlapped with the sealing plate. The shape of the base portion may be, for example, a disc shape, but is not limited thereto.

[0018] The gasket is made of a material having elasticity and insulation for functioning as a gasket. The gasket may be made of a known material used for the gasket of a secondary battery or a capacitor. Examples of the material of the gasket include polypropylene (PP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), perfluoroalkoxy alkane (PFA), and polyether ether ketone (PEEK). Additives (for example, known additives) may be added to these materials as necessary. There is no limitation on the method of forming the gasket, and it may be formed by a method such as injection molding.

[0019] The sealing plate has a displacement portion and an outer peripheral portion provided around the displacement portion and sandwiched between the compression portions of the gasket. The displacement portion may be provided at the center of the sealing plate. A protrusion protruding toward the power storage element may be formed on the displacement portion. The sealing plate may further have a thin 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 is 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 provided around the displacement portion is, for example, annular when viewed from the axial direction of the case, and the thin portion may also be annular. The protrusion may be arranged, 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 may function as a displacement member that electrically connects the electrode terminal (for example, a terminal cap) and the lead. The sealing plate is composed of, for example, a metal plate and is composed of a metal such as aluminum, nickel, copper, iron, an alloy of these metals, or a clad material. Note that the protrusion and the 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 other members or directly connected. There is no particular limitation on the indirect or direct connection method between the sealing plate and the lead, and welding or the like may be used, for example.

[0021] In the power storage device of the present disclosure, as the function of the current interruption mechanism, when the internal pressure in the case rises, the displacement portion is displaced in a direction away from the lead, whereby the electrical connection between the displacement portion and the lead is broken. Such displacement may occur when the internal pressure in the case exceeds a predetermined value. When such displacement occurs, the displacement of the lead is suppressed by displacement suppressing means arranged in the case. The displacement portion is electrically disconnected from the lead whose displacement is suppressed, whereby the current interruption mechanism operates properly.

[0022] A through hole may be formed in the base. The through hole may be located in the central region of the base. The shape of the through hole is not particularly limited and may be circular, elliptical, oblong, rectangular, polygonal, etc. The lead may have a connection region at least one end in the width direction (short side direction) of the lead in which at least one bent portion is formed as a displacement suppression means. Such a connection region has higher rigidity against bending force than the connection region (connection portion to the displacement portion) of a conventional lead in which no bent portion is formed. The bent portion may be formed at both ends in the width direction of the lead, or at only 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 the through hole in the base. That is, the lead may be electrically and physically connected to the sealing plate. There is no particular limit to the method of connecting the lead and the sealing plate, and welding may be used, for example. However, in order to function as a current interruption mechanism, it is necessary that the connection between the lead and the sealing plate is released when the force pulling the lead and the sealing plate apart becomes large. In this case, as a mechanism to break the connection between the lead and the displacement part, the welded portion between the lead and the displacement part may be broken, or a weak point may be provided around the connection point with the displacement part in the lead, and this weak point may break when the displacement part 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 welding area and welding depth. There are no particular limitations on the welding method, and laser welding, resistance welding, friction stir welding, ultrasonic bonding, etc. may be used.

[0023] In this configuration of energy storage device, the current interruption mechanism works by displacing the displaced part away from the lead in response to an increase in internal pressure within the case, thereby severing the connection between the displaced part 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 displaced part is connected, i.e., the connection region, has at least one bent portion. Therefore, the connection region is stronger and less prone to deformation than the portion of the lead to which the bent portion is not formed. As a result, even if the lead is pulled by the displaced part, the displacement of the lead is suppressed. The displaced part is then disconnected from the lead whose displacement has been suppressed, thereby allowing the current interruption mechanism to function properly.

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

[0025] At least one bent portion may have a fold that is inclined with respect to the longitudinal direction of the lead. Such a fold may be formed, for example, by bending the lead along a straight line that moves from the center of the lead's width toward the end as it moves away from the tip of the lead. With this configuration, at least one bent portion can be formed by the process of bending the lead alone, thus reducing the increase in the number of steps required to manufacture the energy storage device.

[0026] The angle between at least one bent portion and the main surface of the lead may be greater than 0° and less than 180°. If the angle is within this range, the effect of improving the strength of the lead due to the bent portion can be obtained. Furthermore, it is preferable that the angle is 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] At least one bent portion may include two bent portions. One bent portion may be located at one end in the width direction of the lead. The other bent portion may be located at the other end in the width direction of the lead. With this configuration, no bent portion is formed in the central region in the width direction of the lead, so this central region can be used for connection with the displacement portion. In addition, 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 with the outer periphery of the sealing plate when viewed from the axial direction of the case. The 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 interruption mechanism operates, the base is less likely to be deformed by the connection region of the lead that is pulled along with the displacement of the displaced part. This is because the displacement of one end and the other end of the connection region is restrained by the outer periphery of the sealing plate located on the opposite side of the base. Therefore, the operational reliability of the current interruption mechanism can be further improved.

[0029] The energy storage device may further include a reinforcing member as a displacement suppression means to reinforce the base. The reinforcing member may be made of a material with higher rigidity than the gasket's constituent material in order to reinforce the gasket base with high reliability. The reinforcing member may also be made of a material with higher rigidity than the lead, or it may be made of the same material as the lead but designed to be thicker than the lead. The reinforcing member may be a conductive material and may be made of 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), perfluoroalkoxyaluane (PFA), and polyetheretherketone (PEEK). The reinforcing member may be integrated with the gasket or its base, or it may be a separate component. In the former case, the reinforcing member may be insert-molded together with the gasket, for example. In the latter case, the reinforcing member may be mechanically locked to the base, the reinforcing member may be press-fitted into a hole provided in the base, or the two may be fixed together via an adhesive. If the reinforcing member is made of an insulating material, a through hole or notch may be formed in the reinforcing member, and the projection of the displacement part may be inserted through this 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 on the energy storage element side and exposes a second portion of the main surface. The second portion may be used for electrical connection between the displacement part of the sealing plate and the lead. It is desirable that the first portion covers as much area as possible (for example, 70% or more or 90% or more of the area) of the area of ​​the main surface of the reinforcing member on the energy storage element side other than the second portion. Also, on the main surface of the base on the energy storage element side, the portion that overlaps with the reinforcing member may protrude further toward the energy storage element than the portion that does not overlap with the reinforcing member. This configuration makes it easier to keep the portion that needs to be thickened as the base to the minimum necessary, and it is possible to suppress the thickening of the compression part. Therefore, it is possible to suppress the increase in size of the sealing component.

[0030] In this configuration of energy storage device, the current interruption mechanism works by displacing the displacement part away from the lead in response to an increase in internal pressure within the case, thereby severing the electrical connection between the displacement part 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 less likely to be displaced because it is reinforced by a reinforcing member. Therefore, even if the lead is pulled due to this displacement, the lead will come into contact with the base of the gasket, suppressing the displacement of the lead. The displacement part is electrically disconnected from the lead whose displacement has been suppressed, thereby allowing the current interruption mechanism to operate properly.

[0031] Furthermore, in this configuration of the 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. Since 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 it from moving within the case and coming into contact with the case or other components, thus preventing a short circuit. In addition, even if the reinforcing member is made of an insulating material, the operation of the current interruption mechanism tends to be more stable.

[0032] If the reinforcing member is a conductive member, the displacement portion of the sealing plate and the reinforcing member may be connected at a first connection point. The first connection point may be located in the center of the displacement portion and the reinforcing member. The reinforcing member and the lead may also be connected at a second connection point separate from the first connection point. Furthermore, as the internal pressure inside the case increases, the displacement portion may be displaced away from the lead, thereby breaking the connection between the displacement portion and the reinforcing member, and thus breaking 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 a conductive reinforcing member. The function of the current interruption mechanism is achieved when the connection between the displacement portion and the reinforcing member is broken, in other words, when the first connection point breaks.

[0033] The first and second connection parts may be separated from each other in the radial direction of the case. This configuration makes it easy to form the first and second connection parts separately under different conditions. Therefore, the connection strength of the first connection part can be made lower than that of the second connection part, making it easy to realize the operation of the current interruption mechanism due to the breakage of the former. Note that the first and second connection parts do not have to be separated from each other in the radial direction of the case. In this case, the two connection parts may be a single unit or may be separate.

[0034] At least one opening may expose the main surface at the positions corresponding to the first and second connection portions as a second portion. With this configuration, the first and second connection portions can be easily formed, for example, by welding, through the second portion exposed from at least one opening. In this case, the at least one opening includes a first opening that exposes the first connection portion and a second opening that exposes the second connection portion, and the first and second openings may be spaced apart from each other. With this configuration, compared to a configuration in which the first and second connection portions are exposed by a single opening, more of the base portion of the reinforcing member that does not contribute to the first or second connection portion can be covered. Therefore, the possibility of the reinforcing member coming into contact with other conductive members and causing a short circuit can be reduced. In addition, by connecting the lead and the reinforcing member at the second opening, the periphery of the second opening functions to suppress the displacement of the lead, making it easier to connect the lead and the reinforcing member.

[0035] The base may cover at least a portion of the main surface of the reinforcing member on the sealing plate side. In other words, at least a portion of the base may be interposed between the sealing plate and the reinforcing member. With this configuration, the base can hold the reinforcing member from both sides in the axial direction. Therefore, the reinforcing member can be fixed to the base more firmly. Furthermore, if the reinforcing member is made of a conductive material, the interposition of a portion of the base between the reinforcing member and the sealing plate can suppress electrical connection between the sealing plate and the reinforcing member after the sealing plate has acted as a current interruption mechanism. The main surface of the reinforcing member on the sealing plate side may be covered with an insulating member separate from the base.

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

[0037] In the following, an example of an energy storage device related to this disclosure will be described in detail with reference to the drawings. The components of the example energy storage device described below can be the components described above. The components of the example energy storage device described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiments. Among the components of the example energy storage device described below, components that are not essential to the energy storage device related to this disclosure may be omitted. Note that the figures shown below are schematic and do not accurately reflect the actual shape and number of components.

[0038] Embodiment 1 Embodiment 1 of this disclosure will now be described. The energy storage device 10 in this embodiment is a lithium-ion secondary battery, but is not limited thereto. For example, the energy storage device 10 may be a lithium-ion capacitor, an electric double-layer capacitor, an intermediate energy storage device between a lithium-ion secondary battery and a lithium-ion capacitor, or other electrochemical devices.

[0039] As shown in Figures 1 and 2, the energy storage device 10 comprises a bottomed cylindrical case 20, an energy storage element 30 disposed inside the case 20 and including a pair of electrodes (not shown), a first lead 41 connected to one of the electrodes, a second lead 45 connected to the other electrode, and a sealing member 50 that seals the open end 21a of the case 20. The energy storage device 10 further comprises first and second insulating plates 61 and 62. The first and second insulating plates 61 and 62 are disc-shaped members with through holes formed in them.

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

[0041] The energy storage element 30 is generally cylindrical in shape. The energy storage element 30 is constructed by winding a positive electrode and a negative electrode (not shown) via a separator (not shown).

[0042] One end of the first lead 41 is connected to one electrode (the 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 a projection 57a ​​of the sealing plate 56. As a result, the sealing plate 56 functions as the positive electrode terminal of the energy storage device 10. The first lead 41 is an example of a lead. The bent portions 43 are an example of displacement suppression means.

[0043] As shown in Figure 2, the connection region 42 has one bent portion 43 formed at each end of the first lead 41 in the width direction (the direction perpendicular to the plane of the paper in Figure 1). Each bent portion 43 has a fold line along the longitudinal direction (the left-right direction in Figure 1) of the first lead 41. One bent portion 43 is located at one end of the first lead 41 in the width direction. The other bent portion 43 is located at the other end of the first lead 41 in the width direction. Each bent portion 43 can be formed by making an incision in the first lead 41 and bending the first lead 41 along its longitudinal direction.

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

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

[0046] The connection region 42 extends from the tip of the first lead 41 over a predetermined length. However, the connection region 42 may also extend from a position some distance from the tip of the first lead 41 over a predetermined length. 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 projection 57a ​​of the sealing plate 56 is connected.

[0047] One end of the second lead 45 is connected to the other electrode (the negative electrode in this example) of the energy storage element 30. The second lead 45 is made of a strip of 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 causes the case 20 to function as the negative electrode terminal of the energy storage device 10.

[0048] The sealing member 50 comprises an insulating gasket 51 and a conductive sealing plate 56. The gasket 51 has a compression portion 52 interposed between the cylindrical portion 21 (groove portion 21b) and the sealing plate 56, and a base portion 53 that overlaps with the sealing plate 56. The base portion 53 is positioned 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 peripheral portion 58 of the sealing plate 56 are in close contact. In addition to the through hole 53a into which the projection 57a ​​is inserted, the gasket 51 may also have a through hole (not shown) for supplying gas to the sealing plate 56.

[0049] The sealing plate 56 has a displacement portion 57 in its center, an outer peripheral portion 58 surrounding the displacement portion 57 and sandwiched between the compression portion 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 projection 57a ​​that protrudes toward the energy storage element 30. The cross-sectional shape of the projection 57a ​​(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 outer peripheral portion 58.

[0050] The projection 57a ​​of the sealing plate 56 is inserted into the through hole 53a. Here, a gap may or may not be formed between the projection 57a ​​and the through hole 53a. As described above, the projection 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 the case 20 increases, the projection 57a ​​of the displacement section 57 is displaced in a direction away from the energy storage element 30 (i.e., away from the first lead 41). On the other hand, the displacement of the first lead 41 is suppressed by the high-strength connection region 42. Therefore, if the displacement of the projection 57a ​​becomes large, the connection between the projection 57a ​​and the first lead 41 is broken. As a result, overcharging and other problems are suppressed.

[0052] If the internal pressure inside case 20 increases further and the displacement of the displacement portion 57 becomes even larger, the thin-walled portion 59 or its peripheral edge will rupture. As a result, the gas inside case 20 will be released to the outside of case 20.

[0053] Modified form of Embodiment 1 A modified example of Embodiment 1 of this disclosure will now be described. The energy storage device 10 of this modified example differs from Embodiment 1 in the configuration of the connection area 42. The differences from Embodiment 1 will be mainly described below.

[0054] As shown in Figure 3, the connection region 42 in this embodiment is longer than the connection region 42 in the first embodiment described above. Specifically, one end and the other end of the connection region 42 overlap with the outer periphery 58 of the sealing plate 56 when viewed from the axial direction of the case 20 (viewed from above in Figure 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. Here, 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 portion 54 positioned between the first lead 41 and the protruding end of the groove portion 21b. The side wall portion 54 may be provided only in the region where the first lead 41 and the groove portion 21b are in close proximity, or it may be provided around the entire circumference. The side wall portion 54 may protrude toward the energy storage element 30 from the main surface (bottom surface in Figure 3) of the base portion 53 on the energy storage element 30 side. This side wall portion 54 prevents the connection region 42 from coming into contact with the inner surface of the case 20.

[0056] Embodiment 2 Embodiment 2 of this disclosure will now be described. The energy storage device 10 of this embodiment differs from Embodiment 1 in the configuration of the bent portion 43. The differences from Embodiment 1 will be mainly described below.

[0057] As shown in Figure 4, in this embodiment, the connection region 42 has one bent portion 43 formed at each end of the first lead 41 in the width direction. 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 located at one end of the first lead 41 in the width direction. The other bent portion 43 is located at the other end of the first lead 41 in the width direction. 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 they approach each other from the base end to the tip end of the first lead 41.

[0058] Embodiment 3 Embodiment 3 of the present disclosure will now be described. The energy storage device 110 in this embodiment is a lithium-ion secondary battery, but is not limited thereto. For example, the energy storage device 110 may be a lithium-ion capacitor, an electric double-layer capacitor, an intermediate energy storage device between a lithium-ion secondary battery and a lithium-ion capacitor, or other electrochemical devices.

[0059] As shown in Figures 5 to 7, the energy storage device 110 comprises a bottomed cylindrical case 120, an energy storage element 130 disposed inside 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 the open end 121a of the case 120, and a reinforcing member 170. The energy storage device 110 further comprises first and second insulating plates 161 and 162. The first and second insulating plates 161 and 162 are disc-shaped members with through holes formed in them.

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

[0061] The energy storage element 130 is generally cylindrical in shape. The energy storage element 130 is constructed by winding a positive electrode and a negative electrode (not shown) via a separator (not shown).

[0062] One end of the first lead 141 is connected to one electrode (the positive electrode in this example) of the energy storage element 130. The first lead 141 is made of a strip of metal foil, but is not limited to this. The other end of the first lead 141 is connected to a reinforcing member 170. As will be described later, the reinforcing member 170 is connected to a sealing plate 156, so that 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 (the negative electrode in this example) of the energy storage element 130. The second lead 142 is made of a strip of 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 causes the case 120 to function as the negative electrode terminal of the energy storage device 110.

[0064] The sealing member 150 comprises 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 overlaps with the sealing plate 156. The base portion 153 is positioned 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-shaped through hole 153a is formed in the central region of the base portion 153. The peripheral edge of the base portion 153 and the outer peripheral portion 158 of the sealing plate 156 are in close contact.

[0065] A reinforcing member 170 is positioned inside the base 153. The base 153 covers the main surface of the reinforcing member 170 on the side opposite to the energy storage element 130 (upper side in Figure 5), except for the region where the insertion hole 153a is formed. The base 153 has a first opening 153c and a second opening 153d that cover the first portion 170a of the main surface of the reinforcing member 170 on the energy storage element 130 side (lower side in Figure 5) and expose the second portion 170b of the main surface. The first opening 153c is provided at a position corresponding to the first connection portion 181, which will be described later (in this example, the central position of the base 153). The second opening 153d is provided at a position corresponding to the second connection portion 182, which will be 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 each expose the main surface of the reinforcing member 170 on the energy storage element 130 side as the second portion 170b at the position where they are positioned. The first opening 153c and the second opening 153d are each examples of at least one opening. On the main surface of the base portion 153 on the energy storage element 130 side, the portion that overlaps with the reinforcing member 170 protrudes more towards the energy storage element 130 than the portion that does not overlap with the reinforcing member 170.

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

[0067] The reinforcing member 170 is provided inside the base 153 and reinforces the base 153. The reinforcing member 170 is a conductive member and is made of, for example, 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 on the energy storage element 130 side (the lower surface in Figure 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 Figure 6, the reinforcing member 170 is connected to the first lead 141 and the second connecting portion 182 at the first portion 170a exposed from the second opening 153d.

[0068] As shown in Figure 7, the reinforcing member 170 is formed in the shape of a rectangular plate. As shown in Figure 6, in the radial direction of the case 120, the outer end (longitudinal end) of the reinforcing member 170 is located outside the inner end of the outer circumference 158 of the sealing plate 156. Figures 5 and 6 are cross-sectional views of the energy storage device 110 in a cross-section along the longitudinal direction of the reinforcing member 170.

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

[0070] As shown in Figure 6, the first connecting portion 181, which connects the projection 157a and the reinforcing member 170, and the second connecting portion 182, which connects the reinforcing member 170 and the first lead 141, are separated from each other in the radial direction of the case 120. The joint strength of the first connecting portion 181 may be lower than that of the second connecting portion 182. The first connecting portion 181 and the second connecting portion 182 can be formed separately, for example, by laser welding. For example, the first connecting portion 181 may be formed by laser welding through a first opening 153c, and the second connecting portion 182 may be formed by laser welding through a second opening 153d.

[0071] As shown in Figure 7, the base 153 of the gasket 151 has multiple ventilation holes (through holes) 53b formed therein. The ventilation holes 153b are connected to the displacement part 157 so that the internal pressure inside the case 120 is transmitted to the displacement part 157.

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

[0073] If the internal pressure inside case 120 increases further and the displacement of the displacement portion 157 becomes even larger, the thin-walled portion 159 or its peripheral edge will rupture. As a result, the gas inside case 120 will be released to the outside of case 120.

[0074] Embodiment 4 Embodiment 4 of this disclosure will now be described. The shape of the reinforcing member 170 in the energy storage device 110 of this embodiment differs from that of Embodiment 3. The differences from Embodiment 3 will be mainly described below.

[0075] As shown in Figure 8, the reinforcing member 170 in this modified example is formed in the shape of a cross-shaped plate. This configuration allows for more effective reinforcement of the base 153 of the gasket 151.

[0076] Embodiment 5 Embodiment 5 of this disclosure will now be described. The shape of the reinforcing member 170 in the energy storage device 110 of this embodiment differs from that of Embodiment 3. The differences from Embodiment 3 will be mainly described below.

[0077] As shown in Figure 9, the reinforcing member 170 in this embodiment is formed in a disc shape. The reinforcing member 170 has a circular through-hole 170c formed in a position that overlaps with the ventilation hole 153b. Note that the shape of the through-hole 170c is not limited to a circle. With this configuration, the base 153 of the gasket 151 can be reinforced more effectively.

[0078] While this disclosure describes preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which this disclosure pertains by reading the above disclosure. Accordingly, the attached claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of this disclosure. [Industrial applicability]

[0079] This disclosure can be used in energy storage devices. [Explanation of Symbols]

[0080] 10: Energy storage device 20: Case 21:Cylinder part 21a: Open end 21b:Groove 22: Bottom 30: Energy storage element 41: First lead (lead) 42: Connection area 43: Bending section (displacement suppression means) 45: Second lead 50: Sealing member 51: Gasket 52: Compression section 53: Base 53a: Through hole 54: Side wall section 56: Sealing board 57: Displacement part 57a: Protrusion 58: Outer perimeter 59: Thin-walled section 61: First insulating board 62: Second insulating board 110: Energy storage device 120: Case 121:Cylinder part 121a: Open end 121b: Groove 122: Bottom 130: Energy storage element 141: First lead (lead) 142: Second lead 150: Sealing member 151: Gasket 152: Compression section 153: Base 153a: Through hole 153b: Ventilation holes 153c: 1st opening (opening) 153d: Second opening (opening) 156: Sealing board 157: Displacement part 157a: Protrusion 158: Outer perimeter 159: Thin-walled section 161: First insulating plate 162: Second insulating plate 170: Reinforcement member (displacement suppression means) 170a: 1st part 170b:Second part 170c: Through hole 181: First connection section 182: Second connection section

Claims

1. A case having a cylindrical tube portion with an open end at one end, and a bottom portion that closes the other end of the cylindrical portion, A power storage element, which includes a pair of electrodes, is placed inside the aforementioned case. 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 comprises 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 peripheral portion provided around the displacement portion and sandwiched between the compression portions, The displacement portion of the sealing plate and the lead are electrically connected. As the internal pressure inside the case increases, the displacement part is displaced in a direction away from the lead, thereby breaking the electrical connection between the displacement part and the lead. The case further comprises a displacement suppression means disposed within the case, which suppresses the displacement of the lead when the displacement portion is displaced in a direction away from the lead, A through hole is formed in the base portion. The lead has a connection region at least one bent portion formed as the displacement suppression means at at least one end in the width direction of the lead, An energy storage device in which the displacement portion of the sealing plate and the connection region of the lead are connected via the through hole.

2. The energy storage device according to claim 1, wherein the at least one bent portion has a fold along the longitudinal direction of the lead.

3. The energy storage device according to claim 1, wherein the at least one bent portion has a fold that is inclined with respect to the longitudinal direction of the lead.

4. The at least one folded portion includes two of the folded portions, One of the bent portions is positioned at one end of the lead in the width direction, The other bent portion is located at the other end in the width direction of the lead, as described in any one of claims 1 to 3.

5. One end and the other end of the connection region overlap with the outer periphery of the sealing plate when viewed from the axial direction of the case. The energy storage device according to any one of claims 1 to 3, 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.

6. A case having a cylindrical tube portion having an open end at one end, and a bottom portion that closes the other end of the cylindrical portion, A power storage element, which includes a pair of electrodes, is placed inside the aforementioned case. 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 comprises 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 peripheral portion provided around the displacement portion and sandwiched between the compression portions, The displacement portion of the sealing plate and the lead are electrically connected. As the internal pressure inside the case increases, the displacement part is displaced in a direction away from the lead, thereby breaking the electrical connection between the displacement part and the lead. The case further comprises a displacement suppression means disposed within the case, which suppresses the displacement of the lead when the displacement portion is displaced in a direction away from the lead, The displacement suppression means further includes a reinforcing member that reinforces the base, The base portion has at least one opening that covers the first portion of the main surface of the reinforcing member on the energy storage element side and exposes the second portion of the main surface. The reinforcing member is a conductive member, The displacement portion of the sealing plate and the reinforcing member are connected at the first connection portion. The reinforcing member and the lead are connected at the second connection portion. As the internal pressure inside the case increases, the displacement portion is displaced away from the lead, thereby breaking the connection between the displacement portion and the reinforcing member, and consequently breaking the electrical connection between the displacement portion and the lead. The at least one opening exposes the main surface at the position corresponding to the first and second connection portions as the second portion. The at least one opening includes a first opening that exposes the first connecting portion and a second opening that exposes the second connecting portion. A power storage device in which the first opening and the second opening are separated from each other.

7. The energy storage device according to claim 6, wherein the first connection portion and the second connection portion are separated from each other in the radial direction of the case.

8. The energy storage device according to claim 6 or 7, wherein the portion of the main surface of the base on the energy storage element side that overlaps with the reinforcing member protrudes further toward the energy storage element than the portion that does not overlap with the reinforcing member.

9. The energy storage device according to claim 6 or 7, wherein the base covers at least a portion of the main surface of the reinforcing member on the sealing plate side.

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