Energy storage element

Abstract

To provide a power storage element having an electrode terminal including two members made of metals of different kinds and having improved reliability.SOLUTION: A power storage element 10 includes a container 100, an electrode terminal 200, and a gasket 250. The electrode terminal 200 has a shaft 210 made of a first metal and a terminal body 201 made of a second metal. The terminal body 201 has an opening 203 in which the axial end of the shaft 210 is embedded. The shaft 210 includes a flange 211 formed at the end embedded in the opening 203. The flange 211 includes a contact surface 211a that contacts the gasket 250 in the axial direction of the shaft 210. The terminal body 201 has a first facing surface 202a that is a surface facing the gasket 250 in the axial direction of the opening peripheral edge portion 202 that is the peripheral edge portion of the opening 203. The first facing surface 202a is arranged at a position farther from a cover plate 110 than the contact surface 211a in the axial direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an energy storage element having electrode terminals. [Background technology]

[0002] Patent Document 1 discloses a cell (energy storage element) equipped with an electrode terminal fixed to a case (container). The electrode terminal includes a rivet terminal connected to a current collector disposed inside the container, and a movable terminal that abuts against the rivet terminal for electrical connection, has a welding surface to be welded to a bus bar, and is displaceable relative to the rivet terminal. With this configuration, the movable terminal can be displaced relative to the rivet terminal, thereby absorbing strain that occurs in the movable terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-161692 Summary of the Invention [Problem to be solved by the invention]

[0004] As in the conventional electrode terminal described above, the portion bonded to the external bus bar and the portion bonded to the current collector inside the container can be made of different metals (e.g., aluminum and copper). This allows, for example, the electrode terminal to be bonded to other components (e.g., bus bar or current collector) on both the external and internal sides of the container using the same metal, thereby facilitating the formation of a highly reliable joint. However, electrode terminals generally require tight bonding between two components made of different metals, for example, to reduce electrical resistance. Therefore, when the terminal body, located outside the container, and the shaft, which penetrates the container wall, are made of different metals, the terminal body and the shaft are bonded by press-fitting the end of the shaft into the terminal body. More specifically, to tightly and firmly bond the end of the shaft to the fitting hole (opening) of the terminal body, the end of the shaft, whose outer diameter is smaller than the inner diameter of the opening, is inserted into the opening of the terminal body and pressed, compressing the end in the axial direction. This causes the end of the shaft to expand radially within the opening. As a result, a flange that protrudes radially outward is formed on the end of the shaft within the opening, thereby providing a good mechanical and electrical connection between the shaft and the terminal body. However, in this case, although the flange of the shaft and the portion of the terminal body adjacent to the flange are formed flush with each other during the press-fitting process, residual stress can subsequently cause the portion adjacent to the flange to protrude axially beyond the flange. In this case, the flange of the shaft cannot sufficiently press against the gasket located between the terminal body and the wall of the container, potentially resulting in poor airtightness around the shaft of the container.

[0005] The present invention was made by the inventor of the present application by focusing on the above-mentioned problem, and aims to provide an energy storage element having electrode terminals including two members formed of different types of metal, which has improved reliability. [Means for solving the problem]

[0006] An energy storage element according to one embodiment of the present invention is an energy storage element comprising a container, an electrode terminal fixed to a wall of the container, and a gasket arranged between the electrode terminal and the wall of the container, wherein the electrode terminal comprises: a shaft formed of a first metal and arranged so as to penetrate the gasket and the wall; and a terminal body formed of a second metal different from the first metal and arranged on the opposite side of the gasket from the wall, the terminal body having an opening in which an axial end of the shaft is embedded, the shaft having a flange portion formed on the end embedded in the opening, the flange portion including an abutment surface that abuts against the gasket in the axial direction of the shaft, the terminal body having a first opposing surface that is a surface of an opening peripheral portion that is a peripheral part of the opening that faces the gasket in the axial direction, and the first opposing surface is arranged at a position farther from the wall in the axial direction than the abutment surface.

[0007] According to this configuration, when an electrode terminal having a shaft press-fitted into a terminal body is fixed to a wall of a container via a gasket, the abutment surface of the flange of the shaft can firmly press the gasket toward the wall. Specifically, the first opposing surface of the terminal body, which is located on the outer periphery of the flange, is positioned farther from the wall than the abutment surface. This reduces the possibility that the abutment between the first opposing surface and the gasket will result in insufficient compression of the gasket by the abutment surface. This therefore reduces the occurrence of poor airtightness around the shaft of the container. In this way, the energy storage element according to this embodiment is an energy storage element equipped with an electrode terminal including two members made of different types of metals, and is an energy storage element with improved reliability.

[0008] The gasket may have a first convex portion arranged at a position opposite the abutment surface of the flange portion, the first convex portion being compressed by the abutment surface, and the flange portion may have a second opposing surface arranged radially outward of the abutment surface of the shaft, farther from the wall portion than the abutment surface, and facing the gasket.

[0009] In the manufacturing process of an electrode terminal having the above configuration, when the shaft is press-fitted into the terminal body, for example, a jig (mold) is positioned so that the outer edge of the flange is compressed together with the opening periphery located on the outer periphery of the flange in the terminal body. This allows the opening periphery of the terminal body to be reliably compressed to a position above the abutment surface (in the direction opposite to the protruding direction of the shaft). As a result, even if the opening periphery is deformed to return to its original shape due to residual stress, the first opposing surface formed on the opening periphery can be positioned above the abutment surface. In this case, the outer edge of the flange is also compressed together with the terminal body to form a second opposing surface. Since this second opposing surface is positioned above the abutment surface, it cannot compress the gasket located below. However, the gasket according to this embodiment has a first convex portion located opposite the abutment surface. Therefore, this first convex portion is reliably compressed against the abutment surface, thereby ensuring sufficient airtightness.

[0010] The first opposing surface may be located between the contact surface and the second opposing surface in the axial direction.

[0011] When the terminal body is press-fitted into the shaft, the terminal body's opening periphery is compressed together with the outer edge of the flange. Residual stress causes the first opposing surface of the opening periphery to move closer to its original axial position. As a result, the first opposing surface protrudes closer to the gasket than the second opposing surface. However, even in this case, the first opposing surface is positioned farther from the container wall than the abutment surface, reducing the likelihood of the abutment surface insufficiently compressing the gasket.

[0012] The first opposing surface of the terminal body may be spaced apart from the gasket.

[0013] With this configuration, the first opposing surface does not substantially exert a pressing force on the gasket, and almost all of the pressing force on the gasket from the abutting surface is used to compress the gasket. In other words, the pressing force on the gasket from the abutting surface is not reduced by the first opposing surface abutting against the gasket. As a result, the airtightness around the shaft is further improved.

[0014] The gasket may be arranged in a position facing the wall portion of the container and have a second convex portion that is compressed by the wall portion, and the second convex portion may be arranged within the range of the abutment surface when viewed from the axial direction.

[0015] With this configuration, the second protrusion is located within the range of the abutment surface when viewed in the axial direction, and therefore the pressing force of the abutment surface efficiently acts as a force compressing the second protrusion, thereby improving the airtightness between the gasket and the wall portion, and thereby further improving the airtightness around the shaft. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an energy storage element having electrode terminals including two members formed of different types of metals, and having improved reliability. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view showing the appearance of an energy storage element according to an embodiment; [Figure 2] FIG. 2 is an exploded perspective view of the energy storage element according to the embodiment. [Figure 3] FIG. 2 is an exploded perspective view showing the configuration of an electrode terminal and its surroundings according to the embodiment. [Figure 4] 4 is an exploded cross-sectional view showing the configuration of an electrode terminal and its surroundings in an XZ plane passing through line IV-IV in FIG. 3. FIG. [Figure 5] 2 is a cross-sectional view showing the configuration of an electrode terminal and its surroundings according to the embodiment; FIG. [Figure 6] FIG. 6 is a partially enlarged view showing a part of FIG. 5. [Figure 7A] 5A to 5C are partial cross-sectional views showing a part of a manufacturing process for an electrode terminal according to an embodiment. [Figure 7B] 7B is a partial cross-sectional view showing the shape of the electrode terminal after undergoing the step shown in FIG. 7A. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, with reference to the drawings, an energy storage element according to an embodiment (including modified examples) of the present invention will be described. Note that the embodiments described below all show comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, in each drawing, dimensions and the like are not shown strictly. Furthermore, in each drawing, identical or similar components are assigned the same reference numerals. Furthermore, in each drawing, dimensions and the like are not shown strictly.

[0019] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of electrode terminals (positive and negative, hereinafter the same) of an energy storage element are arranged, the direction in which a pair of current collectors are arranged, the direction of the winding axis of the electrode assembly, or the direction in which the short side surfaces of the container face each other. The Y-axis direction is defined as the direction in which the long side surfaces of the container face each other, the lateral direction of the short side surfaces of the container, or the thickness direction of the container. The Z-axis direction is defined as the direction in which the container body and cover plate of the energy storage element are arranged, the longitudinal direction of the short side surfaces of the container, or the extension direction of the electrode assembly connection portion of the current collector. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment).

[0020] In the following description, for example, the positive X-axis direction refers to the direction of the X-axis arrow, and the negative X-axis direction refers to the direction opposite to the positive X-axis direction. The same applies to the Y-axis and Z-axis. Furthermore, expressions indicating relative directions or attitudes, such as parallel and orthogonal, also include cases where the directions or attitudes are not strictly the same. For example, "two directions are parallel" does not only mean that the two directions are completely parallel, but also means that the directions are substantially parallel, that is, that there is a difference of, for example, a few percent. Furthermore, simply referring to the "X-axis direction" means both directions or either direction parallel to the X-axis. The same applies to terms related to the Y-axis and Z-axis. In the following description, when the term "insulation" is used, it means "electrical insulation."

[0021] (Embodiment) [1. General explanation of energy storage elements] First, an energy storage device 10 according to an embodiment will be generally described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the appearance of the energy storage device 10 according to the embodiment. Fig. 2 is an exploded perspective view of the energy storage device 10 according to the embodiment. Specifically, Fig. 2 is a perspective view showing the electrode body 400 and the like of the energy storage device 10, with the cover plate 110 of the container 100 and the container body 101 separated from each other.

[0022] The energy storage device 10 is a secondary battery (single cell) that can charge and discharge electricity, and more specifically, is a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage device 10 is used, for example, as a battery for driving or starting the engine of a mobile object such as an automobile, motorcycle, personal watercraft, ship, snowmobile, agricultural machinery, construction machinery, or electric railway vehicle. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a gasoline-powered vehicle, and a diesel-powered vehicle. Examples of the electric railway vehicle include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The energy storage device 10 can also be used as a stationary battery for home or business use.

[0023] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, but may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may not be a secondary battery, but may be a primary battery that allows stored electricity to be used without the user having to charge it. The energy storage element 10 may also be a battery that uses a solid electrolyte. In the present embodiment, the energy storage element 10 is illustrated as having a rectangular parallelepiped (cornered) shape, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, and may be a cylindrical shape, an elongated cylindrical shape, a polygonal prism shape other than a rectangular parallelepiped, or the like.

[0024] As shown in Fig. 1, the energy storage element 10 includes a container 100, a negative electrode terminal 200, and a positive electrode terminal 300. As shown in Fig. 2, the container 100 contains a negative current collector 120, a positive current collector 130, and an electrode assembly 400.

[0025] In addition to the above components, the energy storage element 10 may also include spacers arranged on the sides of the current collectors 120 and 130, or an insulating film that encases the electrode assembly 400, etc. Furthermore, an electrolyte solution (non-aqueous electrolyte) or the like is sealed inside the container 100 of the energy storage element 10, but this is not shown in the drawings. There are no particular restrictions on the type of electrolyte solution sealed in the container 100, as long as it does not impair the performance of the energy storage element 10, and various types can be selected.

[0026] The container 100 is composed of a rectangular cylindrical container body 101 with a bottom, and a cover plate 110 that forms a wall that closes the opening of the container body 101. The container 100 has a structure in which the interior is sealed by welding the cover plate 110 to the container body 101 after the electrode assembly 400 and other components are housed inside. The materials of the cover plate 110 and the container body 101 are not particularly limited, but are preferably weldable metals such as stainless steel, aluminum, or aluminum alloys.

[0027] The electrode assembly 400 is an electricity storage element (power generation element) that includes a positive electrode plate, a negative electrode plate, and a separator and can store electricity. The positive electrode plate is an electrode plate in which a composite layer containing a positive electrode active material is formed on a positive electrode substrate layer that is a long strip-shaped current collector foil made of aluminum, an aluminum alloy, or the like. The negative electrode plate is an electrode plate in which a composite layer containing a negative electrode active material is formed on a negative electrode substrate layer that is a long strip-shaped current collector foil made of copper, a copper alloy, or the like. The separator is a microporous sheet made of resin or the like. The electrode assembly 400 is formed by winding the positive electrode plate and the negative electrode plate with the separator disposed between them.

[0028] The electrode assembly 400 has a positive electrode end 411a formed by laminating a base material layer of a positive electrode plate at one end (the end on the negative side in the X-axis direction in FIG. 2 ) in the direction of the winding axis (the X-axis direction in this embodiment). The electrode assembly 400 also has a negative electrode end 421a formed by laminating a base material layer of a negative electrode plate at the other end (the end on the positive side in the X-axis direction in FIG. 2 ) in the direction of the winding axis. The positive electrode end 411a is joined to the current collector 130, and the negative electrode end 421a is joined to the current collector 120.

[0029] In this embodiment, the shape of the electrode assembly 400 when viewed from the direction of the winding axis is an oval shape, but the shape may be an ellipse, a circle, a polygon, or the like. The type of electrode assembly 400 is not limited to a wound type. For example, the energy storage element 10 may be provided with a stacked electrode assembly in which flat electrode plates are stacked, or a bellows-type electrode assembly in which long strip-shaped electrode plates are folded in a bellows shape.

[0030] The electrode terminal 200 is a negative electrode terminal electrically connected to the negative electrode of the electrode assembly 400 via the current collector 120. The electrode terminal 300 is a positive electrode terminal electrically connected to the positive electrode of the electrode assembly 400 via the current collector 130. The electrode terminals 200 and 300 are attached to the cover plate 110 disposed above the electrode assembly 400 via gaskets 250 and 350.

[0031] The material of the current collector 130 is not limited, but is formed of, for example, aluminum or an aluminum alloy, similar to the positive electrode substrate layer of the electrode assembly 400. The material of the current collector 120 is also not limited, but is formed of, for example, copper or a copper alloy, similar to the negative electrode substrate layer of the electrode assembly 400.

[0032] In the energy storage element 10 configured in this manner, the portion of the electrode terminal 200 serving as the negative electrode terminal that is joined to an external bus bar or the like and the portion that is joined to the current collector 120 inside the container 100 are made of different types of metal. The configuration of the electrode terminal 200 having such characteristics and its surroundings will be described below with reference to FIGS. 3 to 7B.

[0033] [2. Electrode terminal and its peripheral configuration] FIG. 3 is an exploded perspective view showing the electrode terminal 200 and its surrounding structure according to the embodiment. FIG. 4 is an exploded cross-sectional view showing the electrode terminal 200 and its surrounding structure taken along the XZ plane passing through line IV-IV in FIG. 3. In FIGS. 3 and 4, the shaft 210 is shown in a state before being crimped. FIG. 5 is a cross-sectional view showing the electrode terminal 200 and its surrounding structure according to the embodiment. The position of the cross section in FIG. 5 corresponds to the position of the cross section in FIG. 4. FIG. 6 is a partially enlarged view showing a portion of FIG. 5. In FIGS. 5 and 6, the first convex portion 256 and the second convex portion 257 are slightly protruded to indicate their positions. FIG. 7A is a partial cross-sectional view showing a part of the manufacturing process for the electrode terminal 200 according to the embodiment, and FIG. 7B is a partial cross-sectional view showing the shape of the electrode terminal 200 after the process shown in FIG. 7A. The position of the cross section in FIGS. 7A and 7B corresponds to the position of the cross section in FIG. 4.

[0034] As shown in FIGS. 3 to 6, in this embodiment, the electrode terminal 200 has a terminal body 201 and a shaft body 210. The terminal body 201 and the shaft body 210 are formed of different types of metals. Specifically, the shaft body 210 is formed of, for example, copper or a copper alloy, like the current collector 120 joined to the negative electrode end portion 421a of the electrode body 400. The terminal body 201 is formed of, for example, aluminum or an aluminum alloy from the viewpoint of ease of welding to an aluminum bus bar or the like. In this embodiment, copper or a copper alloy is an example of a first metal, and aluminum or an aluminum alloy is an example of a second metal.

[0035] The electrode terminal 200 is fixed to the container 100 via a gasket 250. Specifically, the gasket 250 is disposed between the terminal body 201 and the cover plate 110 of the container 100. The cover plate 110 is an example of a wall portion of the container 100. The shaft 210 fixed to the terminal body 201 is disposed so as to pass through a through-hole 252 of the gasket 250, a through-hole 112 of the cover plate 110, a through-hole 282 of the insulating member 280, and a through-hole 123 formed in the terminal connection portion 121 of the current collector 120. Furthermore, as shown in FIG. 5 , the tip of the shaft 210 is crimped, thereby forming a crimped portion 212a. As a result, the gasket 250, the insulating member 280, and the current collector 120 are fixed to the cover plate 110 together with the electrode terminal 200. 3, the current collector 120 has a pair of legs 122, which are joined to the negative electrode end 421a (see FIG. 2) of the electrode body 400. In this configuration, more specifically, the gasket 250 has a cylindrical portion 259 (see FIG. 4) that forms the through hole 252. The cylindrical portion 259 serves to maintain airtightness between the shaft 210 of the electrode terminal 200 and the through hole 112 of the cover plate 110, and to electrically insulate the shaft 210 from the cover plate 110.

[0036] Thus, the gasket 250 not only serves to maintain airtightness around the shaft body 210 of the electrode terminal 200, but also serves to insulate the electrode terminal 200 from the container 100 together with the insulating member 280. The gasket 250 and the insulating member 280 are each made of an insulating material such as polypropylene (PP), polyethylene (PE), polyphenylene sulfide resin (PPS), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), or polyethersulfone (PES).

[0037] 3 to 5, the gasket 250 has a side wall 258 that surrounds the end face of the terminal body 201 in a direction (parallel to the XY plane) perpendicular to the thickness direction (Z-axis direction). The side wall 258 functions, for example, as a member that prevents conduction between the electrode terminal 200 and an external member disposed near the energy storage device 10. The side wall 258 also functions as a rotation stopper for the electrode terminal 200, for example, during the manufacture and use of the energy storage device 10.

[0038] In this manner, in electrode terminal 200 fixed to cover plate 110 via gasket 250, terminal body 201 and shaft body 210, which are made of different types of metals, are joined in the state shown in Fig. 4. Specifically, shaft body 210 has shaft body portion 212, which is a cylindrical rod, and flange portion 211 extending radially from shaft body portion 212, with flange portion 211 embedded in opening 203 provided on the gasket 250 side of terminal body 201. More specifically, for example, the end of shaft body portion 212, without flange 211 formed thereon, is inserted into opening 203 of terminal body 201, which has an inner diameter larger than the outer diameter of shaft body portion 212, and pressed with a large force. In other words, the end of shaft body portion 212 is press-fitted into opening 203 of terminal body 201. This causes the end portion to expand radially within opening 203, resulting in the formation of flange 211 that expands radially within opening 203, bringing the inner surface of opening 203 and shaft 210 into close contact. As a result, terminal body 201 and shaft 210, which are made of dissimilar metals, are joined mechanically strongly and with reduced electrical resistance. Note that flange 211 having an outer diameter that allows insertion into opening 203 may be formed on the end portion of shaft body portion 212 before the end portion is press-fitted into opening 203 of terminal body 201. Even in this case, by press-fitting the end portion including flange 211 into opening 203 and causing flange 211 to expand radially, terminal body 201 and shaft 210 can be joined mechanically strongly and with reduced electrical resistance.

[0039] As described above, when joining terminal body 201 and shaft body 210 by press-fitting, in this embodiment, the base portion of shaft body 210 is formed to protrude in the axial direction of shaft body 210 (in this embodiment, the Z-axis direction, hereinafter simply referred to as the "axial direction") beyond its outer periphery. Specifically, as shown in FIG. 7A , a mold 500 having a stepped portion 501 is placed along the back surface of terminal body 201 (the surface facing gasket 250), and shaft 210 is press-fitted into opening 203 of terminal body 201. Mold 500 is a metal member having a circular hole in its center, through which shaft main body portion 212 of shaft body 210 passes. Mold 500 has a first mold surface 500b on the outer periphery of the circular hole when viewed in the axial direction, and a second mold surface 500a on the outer periphery of first mold surface 500b. The first mold surface 500b is positioned farther from the terminal body 201 in the axial direction than the second mold surface 500a, and a step portion 501 is formed by the boundary between the first mold surface 500b and the second mold surface 500a.

[0040] By press-fitting the shaft 210 into the terminal body 201 using such a mold 500, a step shape that conforms to the shape of the step portion 501 of the mold 500 is formed on the back surface side of the terminal body 201, as shown in FIG. 7B. Specifically, as shown in FIGS. 6 and 7B, an abutting surface 211a and a first opposing surface 202a are formed at different axial positions. The abutting surface 211a is a surface formed on the flange portion 211 that faces and abuts against the gasket 250. The first opposing surface 202a is a surface of the opening peripheral portion 202, which is the peripheral portion of the opening 203 of the terminal body 201, that faces the gasket 250. The first opposing surface 202a is positioned farther from the cover plate 110 in the axial direction than the abutting surface 211a. More specifically, as shown in FIGS. 4 to 6, the opening periphery 202 is housed in a recess 251 of the gasket 250, and a first opposing surface 202a, which is the tip surface of the opening periphery 202, faces a bottom surface 251a of the recess 251.

[0041] Here, let us assume that the shaft 210 is press-fitted into the opening 203 of the terminal body 201 using a mold that forms the contact surface 211a and the first opposing surface 202a as flat surfaces without any steps. In this case, immediately after the press-fitting operation is completed and the mold is removed from the electrode terminal 200, the contact surface 211a and the first opposing surface 202a are flush with each other. However, when comparing the shaft 210 made of copper or a copper alloy with the terminal body 201 made of aluminum or an aluminum alloy, the terminal body 201 experiences greater distortion (deformation) due to residual stress due to differences in the physical properties of these materials. As a result, the opening periphery 202 is deformed to return to its original shape due to the residual stress, which may cause the first opposing surface 202a to protrude to a position closer to the cover plate 110 than the contact surface 211a. However, in this embodiment, a mold 500 having a step portion 501 is used to press-fit the shaft 210 into the terminal body 201, thereby forming the first opposing surface 202a at a position recessed relative to the abutment surface 211a (farther from the cover plate 110). As a result, even if the first opposing surface 202a is displaced to return to its original position due to residual stress in the opening periphery 202, the first opposing surface 202a will not protrude to a position closer to the cover plate 110 than the abutment surface 211a. That is, the step width of the step portion 501 of the mold 500 (the difference in the axial positions between the first mold surface 500b and the second mold surface 500a) is equal to or greater than the return distance (axial movement distance) of the first opposing surface 202a due to residual stress. Therefore, even if the first opposing surface 202a moves due to residual stress after the electrode terminal 200 is completed, it will not move beyond the abutment surface 211a. The amount of return of the first opposing surface 202a may be determined by an experiment using the actual electrode terminal 200 and / or theoretical calculations.

[0042] 5 and 6, when the electrode terminal 200 is fixed to the cover plate 110, the contact surface 211a of the flange portion 211 contacts the gasket 250 and presses the gasket 250 toward the cover plate 110. On the other hand, the first opposing surface 202a of the opening periphery 202 of the terminal body 201 is positioned so as not to substantially press the gasket 250.

[0043] That is, the energy storage device 10 according to this embodiment includes a container 100, an electrode terminal 200 fixed to a cover plate 110 of the container 100, and a gasket 250 disposed between the electrode terminal 200 and the cover plate 110 of the container 100. The electrode terminal 200 includes a shaft 210 formed of a first metal and a terminal body 201 formed of a second metal different from the first metal. The shaft 210 is disposed so as to penetrate the gasket 250 and the cover plate 110. The terminal body 201 is disposed on the opposite side of the gasket 250 from the cover plate 110. In other words, the gasket 250 is disposed between the terminal body 201 and the cover plate 110. The terminal body 201 has an opening 203 in which the axial end of the shaft 210 is embedded. The shaft 210 has a flange 211 formed on the end embedded in the opening 203. The flange portion 211 includes an abutment surface 211a that abuts against the gasket 250 in the axial direction of the shaft body 210. The terminal body 201 has a first opposing surface 202a that is a surface of the opening peripheral portion 202 that is the peripheral portion of the opening 203 that faces the gasket 250 in the axial direction. The first opposing surface 202a is located at a position farther from the cover plate 110 in the axial direction than the abutment surface 211a.

[0044] According to this configuration, when the electrode terminal 200 is fixed to the cover plate 110 of the container 100 via the gasket 250, the abutment surface 211a of the flange 211 of the shaft 210 can firmly press the gasket 250 toward the cover plate 110. Specifically, the first opposing surface 202a of the terminal body 201, which is located on the outer periphery (radially outer side) of the flange 211, is disposed farther from the cover plate 110 than the abutment surface 211a. Therefore, abutment between the first opposing surface 202a and the gasket 250 reduces the possibility that the amount of axial compression of the gasket 250 by the abutment surface 211a (and the resulting amount of radial expansion; the same applies hereinafter) due to the abutment between the first opposing surface 202a and the gasket 250 will be insufficient. This reduces the occurrence of poor airtightness around the shaft 210 of the container 100. Thus, the energy storage device 10 according to this embodiment is an energy storage device that includes the electrode terminal 200 including two members formed of different types of metals and has improved reliability.

[0045] Furthermore, the energy storage device 10 according to this embodiment has a configuration for more reliably suppressing poor airtightness around the shaft body 210 of the container 100. Specifically, as shown in Figures 3 and 4, the gasket 250 has a first convex portion 256 arranged at a position facing the abutment surface 211a of the flange portion 211, and the first convex portion 256 is compressed by the abutment surface 211a. The flange portion 211 has a second opposing surface 211b arranged outward of the abutment surface 211a in the radial direction of the shaft body 210, at a position farther from the cover plate 110 than the abutment surface 211a, and opposing the gasket 250.

[0046] 7A , when the shaft 210 is press-fitted into the terminal body 201, the mold 500 is positioned so that the outer edge of the flange 211 is compressed together with the opening circumferential edge 202 located on the outer periphery of the flange 211. That is, when the electrode terminal 200 is viewed in the axial direction during the press-fitting operation, the mold 500 is formed and positioned so that the second mold surface 500a is positioned over an area that includes the outer edge of the flange 211 as well as the entire opening circumferential edge 202. Therefore, the opening circumferential edge 202 of the terminal body 201 is reliably pressed by the second mold surface 500a. This allows the opening circumferential edge 202 of the terminal body 201 to be reliably compressed to a position above the abutment surface 211a (on the opposite side to the protruding direction of the shaft 210). As a result, even if the opening periphery 202 is deformed to return to its original shape due to residual stress, the first opposing surface 202a formed on the opening periphery 202 can be positioned above the abutment surface 211a. In this case, the outer edge portion of the flange 211 is also compressed together with the terminal body 201 to form the second opposing surface 211b, which is positioned above the abutment surface 211a. Therefore, the outer edge portion of the flange 211 cannot compress the gasket 250 located below. However, the gasket 250 according to this embodiment has a first protrusion 256 at a position opposite the abutment surface 211a. Specifically, in this embodiment, the first protrusion 256 is formed on the bottom surface 251a of the recess 251 of the gasket 250, into which the flange 211 and the opening periphery 202 are inserted. Therefore, as shown in FIGS. 5 and 6, the first protrusion 256 is reliably compressed against the contact surface 211a, and as a result, sufficient airtightness by the gasket 250 is ensured.

[0047] 6, the second opposing surface 211b and the first opposing surface 202a are arranged at the same position in the axial direction, but the first opposing surface 202a and the second opposing surface 211b may be arranged at different positions in the axial direction. For example, the first opposing surface 202a may be arranged between the abutment surface 211a and the second opposing surface 211b in the axial direction.

[0048] That is, as described above, when the opening periphery 202 of the terminal body 201 is compressed together with the second opposing surface 211b of the flange 211 when the shaft 210 is press-fitted into the terminal body 201, the first opposing surface 202a is displaced toward its original axial position due to residual stress. As a result, the first opposing surface 202a protrudes to a position closer to the cover plate 110 than the second opposing surface 211b. However, even in this case, the first opposing surface 202a is positioned axially above the abutting surface 211a (farther from the cover plate 110), reducing the possibility that the amount of axial compression of the gasket 250 by the abutting surface 211a will be insufficient. This reduces the occurrence of poor airtightness around the shaft 210 of the container 100.

[0049] Furthermore, the second opposing surface 211b may be located between the first opposing surface 202a and the contact surface 211a. Even in this case, among the contact surface 211a, the first opposing surface 202a, and the second opposing surface 211b, the contact surface 211a is located at a position closest to the cover plate 110 in the axial direction. Therefore, when the electrode terminal 200 is fixed to the cover plate 110, the contact surface 211a of the flange portion 211, including the area surrounding the shaft body portion 212, can reliably compress the gasket 250 in the axial direction. As a result, poor airtightness around the shaft body 210 of the container 100 is suppressed.

[0050] In this embodiment, the first opposing surface 202a of the terminal body 201 is spaced apart from the gasket 250, as shown in FIG.

[0051] According to this configuration, the first opposing surface 202a does not substantially generate a pressing force against the gasket 250. Therefore, almost all of the pressing force against the gasket 250 by the contact surface 211a is used to compress the gasket 250. In other words, the pressing force against the gasket 250 by the contact surface 211a is not reduced by the first opposing surface 202a contacting the gasket 250. As a result, the airtightness around the shaft body 210 is further improved.

[0052] Furthermore, in energy storage device 10 of the present embodiment, gasket 250 is disposed at a position facing cover plate 110 of container 100 and has second convex portions 257 that are compressed by cover plate 110. When viewed in the axial direction, second convex portions 257 are disposed within the range of contact surface 211a. That is, as shown in FIGS. 4 to 6, for example, second convex portions 257 of gasket 250 are disposed in the region directly below contact surface 211a of flange portion 211. Similar to first convex portions 256 (see FIG. 3), second convex portions 257 are formed in an annular shape surrounding through-hole 252 of gasket 250.

[0053] In this way, since the second protrusion 257 is located within the range of the abutment surface 211a when viewed in the axial direction, the pressing force of the abutment surface 211a efficiently acts as a force compressing the second protrusion 257. As a result, the second protrusion 257 is deformed so as to be crushed by the outer surface of the cover plate 110 (the cover plate outer surface 110a), thereby further improving the airtightness between the gasket 250 and the cover plate 110. More specifically, the second protrusion 257 functions as a part that seals the air passage that connects the inside and the outside of the container 100, which is passed between the outer peripheral surface of the cylindrical portion 259 of the gasket 250 and the inner peripheral surface of the through hole 112 of the cover plate 110. As a result, the airtightness between the gasket 250 and the cover plate 110 is improved, and thereby the airtightness around the shaft 210 is further improved. In this embodiment, as shown in FIGS. 4 to 6 , the first protrusion 256 and the second protrusion 257 of the gasket 250 are arranged side by side in the axial direction. Therefore, the pressing force from the abutment surface 211a that presses the gasket 250 in the axial direction acts as a force that efficiently compresses the first convex portion 256 and the second convex portion 257, thereby further improving the airtightness around the shaft body 210 in the container 100.

[0054] [3. Modifications] The energy storage element according to the present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments. Various modifications that a person skilled in the art can make to the above embodiments or modifications are also included within the scope of the present invention, as long as they do not deviate from the spirit of the present invention.

[0055] For example, from the viewpoint of reliably and precisely forming the first opposing surface 202a at a position higher than the abutment surface 211a (on the positive side of the Z axis), it is preferable to position the mold 500 so as to press the outer edge portion of the flange 211 together with the opening periphery 202, as shown in FIG. 7A. As a result, the second opposing surface 211b is formed on the outer periphery of the abutment surface 211a. However, even if the first opposing surface 202a is positioned adjacent to the abutment surface 211a when viewed from the axial direction, the function of the electrode terminal 200 to reliably and firmly compress the gasket 250 in the axial direction by the abutment surface 211a is not lost. In other words, it is not essential that the second opposing surface 211b be formed on the flange 211 of the shaft 210 of the electrode terminal 200.

[0056] Although the first metal used in the shaft 210 is copper or a copper alloy and the second metal used in the terminal body 201 is aluminum or an aluminum alloy, the combination of the first metal and the second metal is not limited thereto. That is, when the first metal and the second metal are different types of metal, differences in the physical properties of these metals may cause the abutting surface 211a and the first opposing surface 202a to have different amounts of axial displacement due to residual stress after the press-fitting operation. Therefore, as in the above embodiment, the first opposing surface 202a is formed at a position recessed from the abutting surface 211a (farther from the cover plate 110) during the press-fitting operation. This prevents the first opposing surface 202a from protruding beyond the abutting surface 211a even if the residual stress in the opening periphery 202 causes the first opposing surface 202a to be displaced axially to reduce the distance from the abutting surface 211a after the press-fitting operation. Furthermore, even if at least one of the contact surface 211a and the first opposing surface 202a is displaced so as to maintain or increase the axial distance therebetween, the first opposing surface 202a remains in a state where it does not protrude beyond the contact surface 211a. That is, in either case, the use of the electrode terminal 200 can provide the effect of improving the airtightness around the shaft body 210.

[0057] In the present embodiment, the wound electrode assembly 400 is housed in the container 100 with the winding axis oriented in the opposing direction of the short side surfaces of the container 100 (the X-axis direction) (see FIG. 2). However, when the energy storage device 10 includes a wound electrode assembly, the electrode assembly may be housed in the container 100 with the winding axis oriented in the longitudinal direction of the short side surfaces of the container 100 (the Z-axis direction), for example. In this case, the electrode assembly may be housed in the container 100 with the positive electrode tab portion and the negative electrode tab portion oriented in the positive direction of the Z-axis. This allows the electrode terminal 200 to be electrically connected to the negative electrode tab portion of the electrode assembly via a flat current collector made of, for example, copper. Even in this case, the abutting surface 211a of the flange portion 211 of the electrode terminal 200 is located closer to the cover plate 110 than the first opposing surface 202a of the terminal body 201, thereby achieving high airtightness by compressing the gasket 250 with the abutting surface 211a. In other words, by using the electrode terminal 200, the effect of improving the airtightness around the shaft body 210 can be obtained regardless of the shape of the current collector connected to the electrode terminal 200 or the type and posture of the electrode body.

[0058] Furthermore, the energy storage element 10 does not necessarily have to include the electrode terminal 300. For example, by electrically connecting the positive electrode of the electrode assembly 400 and the container 100, a part of the container 100 may function as an electrode terminal on the positive electrode side.

[0059] The shape of the gasket 250 does not have to be the shape shown in Figures 3 and 4, etc. For example, the gasket 250 does not have to have the side wall portion 258. For example, the gasket 250 may have various shapes, such as a circle or an oval, when viewed from the axial direction. The shape of the electrode terminal 200 does not have to be the shape shown in Figures 3 and 4, etc. The electrode terminal 200 may have various shapes, such as a circle or an oval, when viewed from the axial direction. [Industrial Applicability]

[0060] The present invention can be applied to an electric storage element such as a lithium ion secondary battery. [Explanation of symbols]

[0061] 10. Energy storage element 100 containers 101 Container body 110 Lid plate 110a Lid plate outer surface 112, 123, 252, 282 through holes 120, 130 Current collector 121 Terminal connection part 122 Legs 200, 300 electrode terminal 201 Terminal body 202 Opening periphery 202a First facing surface 203 Opening 210 Shaft 211 Tsuba 211a Contact surface 211b Second facing surface 212 Shaft body 212a Crimping part 250, 350 gasket 251 recess 251a Bottom 256 First convex part 257 Second convex part 258 Side wall 259 Cylindrical part 280 Insulating materials 400 Electrode body 411a Positive end 421a Negative side end 500 molds 500a Second mold surface 500b First mold surface 501 Step

Claims

1. An energy storage element comprising: a container; an electrode terminal fixed to a wall of the container; and a gasket disposed between the electrode terminal and the wall of the container, The electrode terminal is a shaft formed of a first metal, the shaft being disposed in a state of penetrating the gasket and the wall portion; a terminal body formed of a second metal different from the first metal, the terminal body being disposed on the opposite side of the gasket from the wall portion and having an opening in which an axial end portion of the shaft body is embedded, the shaft body has a flange portion formed on the end portion embedded in the opening, the flange portion including a contact surface that contacts the gasket in the axial direction of the shaft body, the terminal body has a first opposing surface that is a surface of an opening peripheral portion that is a peripheral portion of the opening and that faces the gasket in the axial direction, the first opposing surface is disposed at a position farther from the wall portion than the abutting surface in the axial direction, the gasket has a first convex portion disposed at a position facing the contact surface of the flange portion and compressed by the contact surface, the flange portion is disposed outward of the abutment surface in the radial direction of the shaft, at a position farther from the wall portion than the abutment surface, and has a second opposing surface facing the gasket. Energy storage element.

2. The first opposing surface is located between the abutment surface and the second opposing surface in the axial direction. The energy storage element according to claim 1.

3. An energy storage element comprising: a container; an electrode terminal fixed to a wall of the container; and a gasket disposed between the electrode terminal and the wall of the container, The electrode terminal is a shaft formed of a first metal, the shaft being disposed in a state of penetrating the gasket and the wall portion; a terminal body formed of a second metal different from the first metal, the terminal body being disposed on the opposite side of the gasket from the wall portion and having an opening in which an axial end portion of the shaft body is embedded, the shaft body has a flange portion formed on the end portion embedded in the opening, the flange portion including a contact surface that contacts the gasket in the axial direction of the shaft body, the terminal body has a first opposing surface that is a surface of an opening peripheral portion that is a peripheral portion of the opening and that faces the gasket in the axial direction, the first opposing surface is disposed at a position farther from the wall portion than the abutting surface in the axial direction, the gasket has a recess that is smaller than the terminal body when viewed in the axial direction and that accommodates the opening periphery, the opening peripheral edge portion is disposed between an outer peripheral surface of the flange portion and an inner peripheral surface of the recess portion in a radial direction of the shaft body. Energy storage element.

4. The first opposing surface of the terminal body is disposed spaced apart from the gasket. The energy storage element according to any one of claims 1 to 3.

5. the gasket is disposed at a position facing the wall portion of the container and has a second convex portion that is compressed by the wall portion; the second protrusion is disposed within the range of the contact surface when viewed from the axial direction. The energy storage element according to any one of claims 1 to 4.

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