Energy storage element

Abstract

To provide a power storage element, equipped with a container and an electrode terminal, which has improved reliability.SOLUTION: A power storage element 10 comprises: a container 100; an electrode terminal 130A; a collector 300A disposed inside the container 100; and a connection member 500 which electrically connects the electrode terminal 130A to the collector 300A. The electrode terminal 130A is disposed so as to penetrate a lid body 120 of the container 100 and is made of a first material. The connection member 500 includes a first material part 510 and a second material 520 which are bonded together at a portion where they overlap each other. The first material part 510 is made of the first material. The second material 520 is bonded to the collector 300A and is made of a second material. In a first bonding part 551 formed at a portion not overlapping the second material part 520, the first material part 510 is bonded to the electrode terminal 130A.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an energy storage element including a container and electrode terminals. [Background technology]

[0002] Patent Document 1 discloses a battery including a battery case that houses a power generating element, a nickel positive electrode lead plate for extracting current from the power generating element, and a connecting member that connects the aluminum battery case to the positive electrode lead plate. The battery case is connected to the positive electrode of the power generating element via the connecting member, and functions as a positive electrode terminal. In this battery, the connecting member is formed by laminating an aluminum layer and a nickel layer, and is welded to the inner surface of the battery case with the aluminum layer facing the inner surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-243719 Summary of the Invention [Problem to be solved by the invention]

[0004] As in the above-described conventional technology, a connecting member connecting a positive electrode lead plate (current collector) and a battery case (container and electrode terminal), which are made of different types of metals (dissimilar metals), has a two-layer structure that matches the metals to be connected, which is useful from the perspective of ease of joining by welding or the like. However, because the connecting member is a laminate of two metals, when welding the electrode terminal and the connecting member, as in the battery (energy storage element) in the above-described conventional technology, for example, welding must penetrate the two overlapping metals. Therefore, to form a highly reliable joint, the thermal energy required during welding is relatively large. As a result, when manufacturing an energy storage element in which an electrode terminal is disposed so as to penetrate the container of the energy storage element, the heat generated during welding the electrode terminal and the connecting member may damage the sealing portion of the container at the position where the electrode terminal penetrates, thereby impairing the reliability of the energy storage element.

[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 a container and electrode terminals, which has improved reliability. [Means for solving the problem]

[0006] An energy storage device according to one aspect of the present invention includes a container, an electrode terminal formed of a first material and disposed through a wall of the container, a current collector disposed inside the container, and a connection member that electrically connects the electrode terminal and the current collector, the connection member comprising a first material part and a second material part joined at overlapping portions, the first material part formed of the first material and the second material part joined to the current collector. , th The first material portion includes a second material portion formed of two materials, and the first material portion is joined to the electrode terminal at a first joining portion formed in a portion that does not overlap with the second material portion.

[0007] According to this configuration, the connection member connecting the electrode terminal and the current collector is formed by overlapping a first material portion and a second material portion. Therefore, a first material, which is the same material as the electrode terminal, can be used for the first material portion of the connection member, and a second material different from the first material can be used for the second material portion of the connection member. This at least improves the bondability (ease of bonding, bonding quality, etc.) between the electrode terminal and the connection member. Furthermore, because the connection member and the electrode terminal are bonded at the portion of the first material portion where the second material portion does not overlap, they can be bonded with, for example, relatively little energy. Therefore, problems such as heat during bonding destroying the sealed portion around the electrode terminal are unlikely to occur. Thus, the energy storage element according to this embodiment is an energy storage element with improved reliability.

[0008] The second material part may be joined to the current collector at a second joint, and when viewed from the overlapping direction of the first material part and the second material part, the first joint may be located on both sides of the second joint.

[0009] According to this configuration, for example, the second bonding portion is formed between two first bonding portions or at a position surrounded by the annular first bonding portions. This allows a structure consisting of the current collector, the connection member, and the electrode terminal bonded between adjacent members to be formed with good mechanical balance. This contributes to improving the reliability of the energy storage element.

[0010] The second material part may be joined to the current collector at a second joint, and when viewed from the overlapping direction of the first material part and the second material part, the second joint may be located on both sides of the first joint.

[0011] According to this configuration, for example, the first bonding portion is formed between two second bonding portions or at a position surrounded by the annular second bonding portions. This allows a structure consisting of the current collector, the connection member, and the electrode terminal bonded between adjacent members to be formed with good mechanical balance. This contributes to improving the reliability of the energy storage element.

[0012] The current collector may be formed from the second material.

[0013] According to this configuration, since the current collector is formed of the same material (second material) as the second material portion of the connection member, it is possible to more reliably improve the bonding between the connection member and the current collector, which contributes to improving the reliability of the energy storage element.

[0014] The energy storage element may further include a covering member arranged to cover the periphery of the bonding interface between the first material portion and the second material portion in the connecting member.

[0015] This configuration reduces the possibility of corrosion caused by contact of the electrolyte with the bonding interface between dissimilar metals such as aluminum and copper, thereby extending the life of the connecting member. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an energy storage element including a container and electrode terminals, which has 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] 1 is a first exploded perspective view of an energy storage element according to an embodiment. FIG. [Figure 3] FIG. 2 is a second exploded perspective view of the energy storage element according to the embodiment. [Figure 4] 1 is a perspective view showing a state in which a covering portion is disposed on a connecting member according to an embodiment. 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. 10 is a cross-sectional view showing the configuration of an electrode terminal and its surroundings according to a first modified example of the embodiment. [Figure 7]FIG. 10 is a bottom view showing the layout of a first bonding portion and a second bonding portion according to the first modification of the embodiment. [Figure 8] FIG. 10 is a cross-sectional view showing the configuration of an electrode terminal and its surroundings according to a second modification of the embodiment. [Figure 9] FIG. 10 is a bottom view showing the layout of the first bonding portion and the second bonding portion according to the second modification of the embodiment. [Figure 10] FIG. 11 is a cross-sectional view showing the configuration of an electrode terminal and its surroundings according to a third modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, with reference to the drawings, an energy storage element according to an embodiment of the present invention (including its modified examples) will be described. Note that the embodiments described below are all 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 and are not intended to limit the present invention. Furthermore, in each drawing, dimensions and the like are not strictly illustrated. Furthermore, in each drawing, the same or similar components are assigned the same reference numerals.

[0019] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of electrode terminals (negative and positive, 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 body, 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 lid of the energy storage element are arranged, the longitudinal direction of the short side surfaces of the container, or the extension direction of the legs of the current collectors. The X-axis direction, Y-axis direction, and Z-axis direction 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 opposite direction to the positive X-axis direction. The same applies to the Y-axis and Z-axis. Furthermore, expressions indicating relative directions or orientations, such as parallel and orthogonal, also include cases where the directions or orientations are not strictly those of the same kind. For example, saying that two directions are parallel does not only mean that the two directions are completely parallel, but also means that the directions are substantially parallel, i.e., there is a difference of, for example, a few percent.

[0021] (Embodiment) [1. General explanation of energy storage elements] First, an energy storage device 10 according to the present 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 a first exploded perspective view of the energy storage device 10 according to the embodiment. Specifically, Fig. 2 shows a state in which the container body 110 is separated from the energy storage device 10.

[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), and a gasoline-powered automobile. 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 , an energy storage element 10 includes a container 100, negative and positive electrode terminals 130, and a sealing member 140 that seals the attachment portions of the container 100 to which the electrode terminals 130 are attached. An electrode assembly 200 and negative and positive current collectors 300 are housed inside the container 100. In this embodiment, when distinguishing between the negative and positive electrode terminals 130, the negative electrode terminal 130 is referred to as electrode terminal 130A, and the positive electrode terminal 130 is referred to as electrode terminal 130B. Furthermore, when distinguishing between the negative and positive current collectors 300, the negative electrode current collector 300 is referred to as current collector 300A, and the positive electrode current collector 300 is referred to as current collector 300B. An electrolytic solution (non-aqueous electrolyte) is enclosed inside the container 100, but is not shown in the figure. The type of the electrolyte is not particularly limited, and various types can be selected as long as they do not impair the performance of the energy storage element 10. Furthermore, a spacer, an insulating film, etc. (not shown) may be placed inside the container 100.

[0025] The container 100 is a rectangular parallelepiped (square) container having a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100, and has short side surfaces 111 on both sides in the X-axis direction, long side surfaces 112 on both sides in the Y-axis direction, and a bottom wall 113 on the negative Z-axis side. The short side surfaces 111 are wall portions that form the short sides of the container 100, and the long side surfaces 112 are wall portions that form the long sides of the container 100.

[0026] The lid 120 is a rectangular plate-like member that constitutes the lid of the container 100, and is disposed on the positive side of the container body 110 in the Z-axis direction. That is, the lid 120 is a wall that faces the bottom wall 113 and is adjacent to the short side surface 111 and the long side surface 112. In this embodiment, the lid 120 has negative and positive electrode terminals 130 fixed thereto. The lid 120 may further be provided with a gas release valve that releases pressure inside the container 100 when the pressure therein increases, a liquid injection port for injecting an electrolyte solution into the container 100, and the like.

[0027] With this configuration, the container 100 is configured such that the electrode assembly 200, with the pair of current collectors 300 connected thereto, is housed inside the container body 110, and then the container body 110 and the lid 120 are joined by welding or the like, thereby sealing the interior. The container body 110 and the lid 120 are formed of a weldable metal, such as stainless steel, aluminum, or an aluminum alloy.

[0028] The electrode assembly 200 is an electricity storage element (power generating 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, which is a long strip-shaped current collecting foil made of aluminum, 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, which is a long strip-shaped current collecting foil made of copper, copper alloy, or the like. The current collecting foil can be made of any known material, such as nickel, iron, stainless steel, titanium, baked carbon, conductive polymer, conductive glass, or Al-Cd alloy. The positive electrode active material and negative electrode active material used in the composite layer can be any known material, as long as they are active materials capable of absorbing and releasing lithium ions. The separator can be made of, for example, a microporous resin sheet or nonwoven fabric.

[0029] In this embodiment, the electrode assembly 200 is a wound-type electrode assembly formed by winding a positive electrode plate and a negative electrode plate with a separator disposed between them. Specifically, the electrode assembly 200 is wound with the positive electrode plate and the negative electrode plate interposed between the separator and shifted relative to each other in the direction of the winding axis (in this embodiment, a virtual axis parallel to the X-axis direction). The positive electrode plate and the negative electrode plate have, at their respective ends in the shifted direction, portions where the composite material containing the active material is not applied (no composite layer is formed) and the base material layer is exposed (composite layer non-formed portions).

[0030] That is, the electrode body 200 has an electrode body main body 210, which is a main body portion on which a composite material layer is formed, and electrode body end portions 220 that protrude from the electrode body main body 210 in the positive and negative X-axis directions. One of these two electrode body end portions 220 is provided with a positive electrode converging portion in which composite material layer-free portions of positive electrode plates are stacked and bundled. The other electrode body end portion 220 is provided with a negative electrode converging portion in which composite material layer-free portions of negative electrode plates are stacked and bundled. Note that, although the present embodiment illustrates an electrode body 200 with an oval cross-sectional shape, the cross-sectional shape of the electrode body 200 may be circular, elliptical, or the like.

[0031] The electrode terminal 130 is a terminal electrically connected to the positive electrode plate or the negative electrode plate of the electrode assembly 200 via the current collector 300. In other words, the electrode terminal 130 is a metal member for leading out electricity stored in the electrode assembly 200 to the external space of the energy storage element 10 and for introducing electricity into the internal space of the energy storage element 10 in order to store electricity in the electrode assembly 200. As described above, the electrode terminal 130 is fixed to a wall (the lid 120 in this embodiment) arranged above the electrode assembly 200.

[0032] Specifically, in this embodiment, the electrode terminal 130 penetrates the lid 120 and is fixed to the lid 120 via the sealing member 140. The end of the electrode terminal 130 on the inner side (negative Z-axis direction side) of the container 100 is joined to the current collector 300. A conductive member (not shown), such as a bus bar, is joined to the end of the electrode terminal 130 on the outer side (positive Z-axis direction side) of the container 100. In this embodiment, each of the electrode terminals 130A and 130B is made of aluminum, an aluminum alloy, or the like. The configuration of the electrode terminal 130A and its surroundings will be described later with reference to FIGS. 3 and 4.

[0033] The current collectors 300 are members (positive electrode current collector and negative electrode current collector) that are arranged on both sides of the electrode assembly 200 in the X-axis direction and connected to the electrode assembly end portions 220. The current collectors 300 have a pair of legs 320. Specifically, the pair of legs 320 of the current collector 300B are joined to the electrode assembly end portion 220 on the positive electrode side, and the pair of legs 320 of the current collector 300A are joined to the electrode assembly end portion 220 on the negative electrode side.

[0034] The current collector 300 and the electrode assembly end portion 220 are joined by ultrasonic welding, crimping, or the like. The material of the current collector 300 is not limited, but for example, the positive electrode side current collector 300 is formed of a metal such as aluminum or an aluminum alloy, similar to the positive electrode substrate layer of the electrode assembly 200. The negative electrode side current collector 300 is formed of a metal such as copper or a copper alloy, similar to the negative electrode substrate layer of the electrode assembly 200.

[0035] [2. Electrode terminal and its peripheral configuration] Next, the configuration of the electrode terminal 130A and its surroundings in the energy storage device 10 according to the embodiment will be described with reference to Fig. 2 as well as Figs. 3 to 5. Note that this embodiment is characterized by the configuration of the surroundings of at least one (electrode terminal 130A) of the pair of electrode terminals 130 included in the energy storage device 10. Therefore, the configuration of one electrode terminal 130 (electrode terminal 130A) and its surroundings will be illustrated and described below.

[0036] FIG. 3 is a second exploded perspective view of the energy storage device 10 according to the embodiment. In FIG. 3, the electrode terminal 130A of the energy storage device 10 and its surrounding components are shown separated. FIG. 4 is a perspective view showing a state in which a covering member 530 is arranged on a connection member 500 according to the embodiment. FIG. 5 is a cross-sectional view showing the electrode terminal 130A and its surrounding configuration according to the embodiment. FIG. 5 is a partial cross-section of the energy storage device 10, which is a partial cross-section in the XZ plane passing through the line VV in FIG. 3, and the electrode body 200 and the container body 110 are not shown. These supplementary notes regarding FIG. 5 also apply to FIGS. 6, 8, and 10, which will be described later.

[0037] 3 and 5 , the electrode terminal 130 according to this embodiment is fixed to the sealing member 140 while penetrating the sealing member 140. The sealing member 140 is inserted into the opening 121 of the lid 120 and fixed to the lid 120, whereby the electrode terminal 130 is fixed to the container 100 while penetrating the opening 121 of the lid 120. The sealing member 140 covers the outer peripheral surface of the electrode terminal 130 and includes an electrically insulating first sealing member 141, and a conductive second sealing member 142 disposed along the outer periphery of the first sealing member 141. In other words, the conductive sealing member 140 holds the electrode terminal 130 while being electrically insulated from the electrode terminal 130.

[0038] The first sealing member 141 is made of, for example, glass or crystallized glass (also called glass ceramic), and has electrical insulation and high heat resistance. The second sealing member 142 is made of the same material as the container 100, such as aluminum or an aluminum alloy, and is fixed to the lid 120 by welding it to the periphery of the opening 121 of the lid 120. In the sealing member 140 configured to hold the electrode terminal 130A, the first sealing member 141 is formed by, for example, sintering glass powder. This results in a sealing member 140 that is integral with the electrode terminal 130A. In other words, the outer circumferential surface of the electrode terminal 130A and the sealing member 140 are tightly sealed by the first sealing member 141 integrated with the electrode terminal 130A, and the sealing member 140 and the periphery of the opening 121 of the container 100 are tightly sealed by metal-to-metal welding. Note that this sealing structure is just one example, and other examples of sealing structures will be described later with reference to FIG.

[0039] The end of the electrode terminal 130A arranged in this manner on the inner side of the container 100 (the negative Z-axis direction side) passes through the through-hole 151 of the internal insulating plate 150 and is connected to the terminal connection portion 310 of the current collector 300A. More specifically, the end of the electrode terminal 130A and the terminal connection portion 310 of the current collector 300A are connected by a connection member 500. The connection member 500 has a first material portion 510 and a second material portion 520 joined together at the overlapping portion. The first material constituting the first material portion 510 is, for example, aluminum or an aluminum alloy. That is, in the present embodiment, the electrode terminal 130A and the first material portion 510 are both formed from the first material, which is aluminum or an aluminum alloy.

[0040] The second material portion 520 of the connection member 500 is formed of a second material different from the first material. In this embodiment, the second material is copper or a copper alloy, and the current collector 300A joined to the electrode body end portion 220 on the negative electrode side is also formed of the second material. The first material portion 510 and the second material portion 520, which are formed of different metals, are, for example, rolled in an overlapping state, thereby being diffusion-bonded. In other words, alloying occurs at the interface between the first material portion 510 and the second material portion 520 due to element diffusion, so the first material portion 510 and the second material portion 520 are extremely firmly bonded. A connection member 500 configured in this manner is called, for example, a clad material.

[0041] In the present embodiment, as shown in FIGS. 3 and 5 , the first material portion 510 of the connection member 500 has a portion that is not overlapped with the second material portion 520, and this portion is joined to the electrode terminal 130A at a first joint portion 551. Furthermore, as shown in FIG. 5 , the second material portion 520 of the connection member 500 is joined to the terminal connection portion 310 of the current collector 300A at a second joint portion 552. The first joint portion 551 and the second joint portion 552 are formed, for example, by laser welding. Note that FIG. 5 schematically illustrates the cross sections of the first joint portion 551 and the second joint portion 552, and the shape, number, and position of the first joint portion 551 and the second joint portion 552 may be different from those shown in FIG. 5 . For example, the second joint portion 552 may penetrate the terminal connection portion 310 and the second material portion 520 and reach the first material portion 510.

[0042] 4, a covering member 530 (not shown in FIGS. 3 and 5) that covers the periphery of the bonding interface between the first material part 510 and the second material part 520 may be disposed on the connecting member 500, which is a laminate of dissimilar metals. The covering member 530 is formed, for example, by coating a resin material so as to cover the periphery of the bonding interface between the first material part 510 and the second material part 520. The covering member 530 prevents the electrolyte from coming into contact with the bonding interface between the first material part 510 and the second material part 520.

[0043] The internal insulating plate 150 is disposed between the lid 120 of the container 100 and the current collector 300A, and is a member that provides insulation between the lid 120 and the current collector 300A. In plan view (when viewed from the Z-axis direction), the internal insulating plate 150 is formed in a substantially rectangular shape large enough to cover the terminal connection portion 310 of the current collector 300A. The internal insulating plate 150 is formed from an electrically insulating resin material such as polypropylene (PP), polyethylene (PE), polyphenylene sulfide resin (PPS), polyethylene terephthalate (PET), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), or polyether sulfone (PES).

[0044] A conductive member (e.g., a bus bar) is joined to the end of the electrode terminal 130A on the exterior side of the container 100 (the positive side along the Z axis). In this embodiment, the bus bar is joined to the end face of the electrode terminal 130A by, for example, laser welding. Bus bars are generally made of aluminum or an aluminum alloy from the standpoints of lightweighting and good conductivity. Therefore, the electrode terminal 130A and the bus bar, which are made of the same metal, can be joined well and easily using a joining method such as laser welding. Note that there are no particular limitations on the method for joining the electrode terminal 130A and the bus bar; they may be joined by other welding methods such as resistance welding, or by mechanical methods such as fastening or crimping.

[0045] That is, the energy storage element 10 according to this embodiment includes a container 100, an electrode terminal 130A, a current collector 300A disposed inside the container 100, and a connection member 500 that electrically connects the electrode terminal 130A and the current collector 300A. The electrode terminal 130A is disposed so as to penetrate a wall portion (lid 120) of the container 100 and is formed of a first material. The connection member 500 includes a first material portion 510 and a second material portion 520 that are joined at an overlapping portion. The first material portion 510 is formed of a first material. The second material portion 520 is joined to the current collector 300A and is formed of a second material. The first material portion 510 is joined to the electrode terminal 130A at a first joining portion 551 that is formed in a portion that does not overlap with the second material portion 520.

[0046] According to this configuration, the connection member 500 connecting the electrode terminal 130A and the current collector 300A is formed by overlapping the first material portion 510 and the second material portion 520. Therefore, the first material, which is the same as the electrode terminal 130A, can be used as the material for the first material portion 510 of the connection member 500, and a second material different from the first material can be used as the material for the second material portion 520 of the connection member 500. This improves the bonding strength between at least the electrode terminal 130A and the connection member 500. Furthermore, because the connection member 500 and the electrode terminal 130A are bonded to each other at the portions of the first material portion 510 where the second material portion 520 does not overlap, bonding can be achieved with, for example, relatively little energy. Therefore, defects such as damage to the sealing portion around the electrode terminal 130A (in this embodiment, the welded portion between the sealing member 140 and the periphery of the opening 121) due to heat generated during bonding are unlikely to occur. Thus, the energy storage device 10 according to this embodiment is an energy storage device with improved reliability.

[0047] Considering direct bonding between the electrode terminal 130A and the current collector 300A, which is made of copper or a copper alloy, it is preferable that the electrode terminal 130A be made of the same metal (copper or a copper alloy). However, because the melting point of copper or a copper alloy is higher than that of aluminum or an aluminum alloy, the energy required for welding is large. Therefore, if the electrode terminal 130A and the current collector 300A were both made of a copper alloy, the heat generated when forming the first joint 551, which is located near the sealed portion around the electrode terminal 130A in the container 100, would likely damage the sealed portion (break airtightness). In this regard, in this embodiment, aluminum or an aluminum alloy is used as the first material, which is the material for the electrode terminal 130A and the current collector 300A. Therefore, the electrode terminal 130A and the current collector 300A can be welded with lower energy than if the first material were copper or a copper alloy. This also reduces damage to the sealed portion around the electrode terminal 130A due to heat during welding. Furthermore, since the first material is aluminum or an aluminum alloy, there is also the advantage that the electrode terminal 130A has good bondability to the bus bar that is the connection partner outside the container 100, as described above.

[0048] Furthermore, in this embodiment, the current collector 300A is made of the second material. That is, the current collector 300A is made of the same material (second material) as the second material portion 520 of the connection member 500, and therefore the bond between the connection member 500 and the current collector 300A can be more reliably improved. This contributes to improving the reliability of the energy storage element 10.

[0049] In addition, in this embodiment, the energy storage element 10 may further include a covering member 530 arranged to cover the periphery of the bonding interface between the first material part 510 and the second material part 520 in the connecting member 500, as shown in Figure 4.

[0050] This configuration reduces the possibility of corrosion due to contact of the electrolyte with the bonding interface between dissimilar metals (e.g., aluminum and copper) between the first material part 510 and the second material part 520. This increases the life of the connecting member 500.

[0051] The energy storage element 10 according to the embodiment of the present invention has been described above, but the electrode terminal 130 and its surroundings of the energy storage element 10 may have a configuration different from that shown in Figures 2 to 5. Therefore, modified examples of the electrode terminal 130 and its surroundings will be described below, focusing on the differences from the above embodiment.

[0052] [3-1. Variation 1] Fig. 6 is a cross-sectional view showing the configuration of an electrode terminal 130A and its surroundings according to the first modification of the embodiment. Fig. 7 is a bottom view showing the layout of a first bonding portion 551 and a second bonding portion 552 according to the first modification of the embodiment. In Fig. 7, in order to clearly show the layout, only the connection member 500a is shown, and each of the first bonding portion 551 and the second bonding portion 552 is schematically shown by a circle with a dot. This also applies to Fig. 9, which will be described later.

[0053] The energy storage element 10a according to this modification includes a connection member 500a that electrically connects the electrode terminal 130A and the current collector 300A. The connection member 500a includes a first material portion 510a and a second material portion 520a that are joined at the overlapping portion. The first material portion 510a is joined to the electrode terminal 130A at a first joint portion 551 formed in a portion that does not overlap with the second material portion 520a. The second material portion 520a is joined to the current collector 300A at a second joint portion 552. The energy storage element 10a according to this modification has these configurations in common with the energy storage element 10 according to the embodiment.

[0054] In this modified example, the positional relationship between the first bonding portion 551 and the second bonding portion 552 differs from that of the embodiment. Specifically, when viewed from the overlapping direction (Z-axis direction) of the first material portion 510a and the second material portion 520a, the first bonding portion 551 is located on both sides of the second bonding portion 552.

[0055] 6 and 7, second joints 552 are formed between two first joints 551 aligned in the X-axis direction and between two first joints 551 aligned in the Y-axis direction. This results in a structure joined between adjacent members in the Z-axis direction, and made up of the current collector 300A, the connection member 500, and the electrode terminal 130A, which is formed in a mechanically balanced manner. This contributes to improving the reliability of the energy storage element 10.

[0056] The first bonding portions 551 may be formed in a continuous ring shape surrounding at least one second bonding portion 552, or three or five or more first bonding portions 551 may be arranged so as to surround at least one second bonding portion 552. In addition, the connecting member 500a may be formed with only two first bonding portions 551, and at least one second bonding portion 552 may be formed between the two first bonding portions 551. In either case, the first bonding portions 551 satisfy the condition that they are located on both sides of the second bonding portion 552 when viewed from the Z-axis direction.

[0057] [3-2. Variation 2] Fig. 8 is a cross-sectional view showing the configuration of an electrode terminal 130A and its surroundings according to Modification 2 of the embodiment. Fig. 9 is a bottom view showing the layout of a first bonding portion 551 and a second bonding portion 552 according to Modification 2 of the embodiment.

[0058] The energy storage element 10b according to this modification includes a connection member 500b that electrically connects the electrode terminal 130A and the current collector 300A. The connection member 500b includes a first material portion 510b and a second material portion 520b that are joined at the overlapping portion. The first material portion 510b is joined to the electrode terminal 130A at a first joint portion 551 formed in a portion that does not overlap with the second material portion 520b. The second material portion 520b is joined to the current collector 300A at a second joint portion 552. These configurations of the energy storage element 10b according to this modification are common to the energy storage element 10 according to the embodiment.

[0059] In this modified example, the positional relationship between the first bonding portion 551 and the second bonding portion 552 is different from that of the embodiment. Specifically, when viewed from the overlapping direction (Z-axis direction) of the first material portion 510b and the second material portion 520b, the second bonding portion 552 is located on both sides of the first bonding portion 551.

[0060] 8 and 9, a first joint 551 is formed between two second joints 552 aligned in the X-axis direction and between two second joints 552 aligned in the Y-axis direction. This results in a structure formed of the current collector 300A, the connection member 500, and the electrode terminal 130A, which are joined between adjacent members in the Z-axis direction, in a well-balanced dynamic state. This contributes to improving the reliability of the energy storage element 10.

[0061] The second bonding portions 552 may be formed in a series of rings surrounding at least one first bonding portion 551, or three or five or more second bonding portions 552 may be arranged so as to surround at least one first bonding portion 551. In addition, only two second bonding portions 552 may be formed in the connection member 500b, and at least one first bonding portion 551 may be formed between the two second bonding portions 552. In either case, the condition that the second bonding portions 552 are located on both sides of the first bonding portion 551 when viewed from the Z-axis direction is satisfied.

[0062] [3-3. Variation 3] FIG. 10 is a cross-sectional view showing the configuration of an electrode terminal 130C and its periphery according to Modification 3 of the embodiment. An energy storage device 10c according to this modification includes a connection member 500 that electrically connects the electrode terminal 130C and the current collector 300A. The connection member 500 includes a first material portion 510 and a second material portion 520 that are joined at the overlapping portion. The first material portion 510 is joined to the electrode terminal 130C at a first joint portion 551 formed in a portion that does not overlap with the second material portion 520. The second material portion 520 is joined to the current collector 300A at a second joint portion 552. The energy storage device 10c according to this modification has these configurations in common with the energy storage device 10 according to the embodiment.

[0063] In an energy storage device 10c according to this modification, the sealing structure around the electrode terminal 130C in the container 100 differs from that of the energy storage device 10 according to the embodiment. Specifically, a sealing member 140a according to this modification includes an insulating member 144 that electrically insulates the electrode terminal 130C from the wall (lid 120) of the container 100, a first sealing member 143a that seals the gap between the insulating member 144 and the lid 120, and a second sealing member 143b that seals the gap between the insulating member 144 and the electrode terminal 130C. The insulating member 144 is a member made of a non-conductor such as ceramic, glass, or crystallized glass. In this embodiment, the insulating member 144 is formed in an annular shape having a hole in the center through which the electrode terminal 130C is inserted. The first sealing member 143a and the second sealing member 143b are brazing filler metals made of, for example, aluminum or copper, and function to fix the electrode terminal 130C to the lid 120 and seal the portion where they are located. Specifically, as shown in FIG. 10 , the first sealing member 143a is disposed between the insulating member 144 and the lid 120, thereby mechanically connecting the insulating member 144 and the lid 120 and sealing the gap between the insulating member 144 and the lid 120. The second sealing member 143b is disposed between the insulating member 144 and a flange 131 provided at the upper end of the electrode terminal 130C, thereby mechanically connecting the insulating member 144 and the electrode terminal 130C and sealing the gap between the insulating member 144 and the electrode terminal 130C. Furthermore, an annular member 122 made of an electrically insulating material is embedded in the gap between the electrode terminal 130C and the inner circumferential surface of the opening 121 of the lid 120. The annular member 122 may be formed, for example, by filling the gap with resin, or may be placed in the gap as a part formed in a ring shape in advance. The annular member 122 and the internal insulating plate 150 may be placed continuously. In this case, the annular member 122 may be provided integrally with the internal insulating plate 150. That is, a part of one part may function as the internal insulating plate 150, and another part may function as the annular member 122.

[0064] As described above, in this modification, the sealing portion around the electrode terminal 130C of the container 100 is formed using brazing material, which is similar to the above embodiment in that the sealing is performed using molten metal. Therefore, high heat resistance and airtightness can be achieved for the sealing portion around the electrode terminal 130C of the container 100. Even if a different sealing structure from the embodiment, such as that shown in FIG. 10 , is adopted, the electrode terminal 130C and the current collector 300A can be electrically and mechanically connected using the connecting member 500, as in the embodiment. That is, the first material portion 510 of the connecting member 500 and the electrode terminal 130C, both made of the first material, are joined at the first joint portion 551, forming a highly reliable first joint portion 551. Furthermore, because the connecting member 500 and the electrode terminal 130C are joined at a portion of the first material portion 510 where the second material portion 520 does not overlap, the joining can be performed with, for example, relatively little energy. Therefore, problems such as damage to the sealing portion around the electrode terminal 130C due to heat during joining are unlikely to occur. Therefore, the energy storage device 10 according to this modification is an energy storage device with improved reliability.

[0065] Energy storage device 10c according to this modification may include, instead of connection member 500, connection member 500a according to modification 1 (see FIG. 6) or connection member 500b according to modification 2 (see FIG. 8).

[0066] [4. Other Modifications] Although the energy storage element according to the embodiment and its modification of the present invention has been described above, the present invention is not limited to this embodiment and its modification. In other words, the embodiment and its modification disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is intended to include all modifications within the meaning and scope of the claims.

[0067] 3 to 5. For example, the size and shape of the connecting member 500 do not have to be the size and shape shown in Figures 3 to 5. For example, the first material portion 510 and the second material portion 520 of the connecting member 500 may each have a shape other than a rectangle, such as a circle, like the first material portion 510a and the second material portion 520a according to Modification 1. The size and shape of the first material portion 510 and the second material portion 520 may be determined appropriately depending on, for example, the number and layout of the first bonding portions 551 and the second bonding portions 552, or the required specifications (bonding area, melt volume, etc.).

[0068] Furthermore, at least one of the first material part 510 and the second material part 520 may be provided with a covering part obtained by coating the surface with a resin or the like. In this case, the thickness of the covering part may be such that it does not interfere with welding between the first material part 510 or the second material part 520 provided with the covering part and the electrode terminal 130 or the current collector 500, which is its bonding partner. This reduces the possibility of corrosion due to contact of the electrolyte with the bonding interface between the first material part 510 and the second material part 520. In other words, the same effect as that of the covering member 530 (see FIG. 4) arranged to cover the periphery of the bonding interface between the first material part 510 and the second material part 520 can be obtained.

[0069] Furthermore, the shape and size of the current collector 300 do not necessarily have to be the shape and size shown in Figure 3 etc. For example, it is not essential that the current collector 300 have the leg portion 320, and the current collector 300 may have, as a connection portion with the electrode assembly (electrode assembly connection portion), an electrode assembly connection portion of a configuration that corresponds to the shape, position, size, etc. of the electrode assembly end portion to which the electrode assembly connection portion is connected. For example, if the electrode assembly included in the energy storage element 10 has a tab portion (a stack of electrode plate tabs) at the end in the Z-axis direction, the current collector included in the energy storage element 10 may have a terminal connection portion that is joined to the second material portion 520 of the connection member 500, and a flat electrode assembly connection portion that is joined to the tab portion and is arranged with its thickness direction facing the Z-axis direction, the same as the terminal connection portion.

[0070] Furthermore, current collector 300A does not have to be made of the same material (second material) as second material part 520. For example, when the second joint part that joins current collector 300A and second material part 520 is formed by a mechanical method such as crimping or fastening, even if current collector 300A is formed of a metal different from the second material, difficulties do not arise as when current collector 300A and second material part 520 are joined by welding.

[0071] The energy storage element 10 may also include multiple electrode bodies 200. For example, if the energy storage element 10 includes two electrode bodies 200 arranged in the Y-axis direction, the current collector 300 may have four legs 320 for connection to the two electrode body ends 220.

[0072] Furthermore, the type of electrode body provided in energy storage element 10 is not limited to the wound type. For example, energy storage element 10 may be provided with a laminated electrode body in which flat electrode plates are stacked, or an electrode body having a structure in which long strip-shaped electrode plates are stacked in a bellows shape by repeatedly folding in peaks and valleys.

[0073] Furthermore, the various supplementary points regarding the energy storage device 10 according to the embodiment described above may be applied to any of the energy storage devices 10a to 10c according to Modifications 1 to 3. Furthermore, configurations constructed by arbitrarily combining the components included in the above embodiment and its modifications are also included within the scope of the present invention. [Industrial Applicability]

[0074] The present invention can be applied to an electric storage element such as a lithium ion secondary battery. [Explanation of symbols]

[0075] 10, 10a, 10b, 10c storage elements 100 containers 120 Lid 121 Opening 130, 130A, 130B, 130C electrode terminal 140, 140a Sealing member 141, 143a First sealing member 142, 143b Second sealing member 144 Insulating materials 150 Internal insulating plate 200 Electrode body 300, 300A, 300B current collector 310 Terminal connection part 500, 500a, 500b connecting members 510, 510a, 510b First Materials Department 520, 520a, 520b Second material section 530 Covering materials 551 First joint 552 Second joint

Claims

1. A container and an electrode terminal formed of a first material and disposed through a wall of the container; a current collector disposed inside the container; a connection member that electrically connects the electrode terminal and the current collector, the connection member includes a first material portion and a second material portion joined to each other at an overlapping portion, the first material portion being made of the first material, and a second material portion being joined to the current collector and made of the second material; the first material portion is joined to the electrode terminal at a first joining portion formed in a portion not overlapping with the second material portion, the second material part is joined to the current collector at a second joint part, When viewed from a direction in which the first material part and the second material part overlap, the first bonding parts are located on both sides of the second bonding part. Energy storage element.

2. A container and an electrode terminal formed of a first material and disposed through a wall of the container; a current collector disposed inside the container; a connection member that electrically connects the electrode terminal and the current collector, the connection member includes a first material portion and a second material portion joined to each other at an overlapping portion, the first material portion being made of the first material, and a second material portion being joined to the current collector and made of the second material; the first material portion is joined to the electrode terminal at a first joining portion formed in a portion not overlapping with the second material portion, the second material part is joined to the current collector at a second joint part, When viewed from the overlapping direction of the first material part and the second material part, the second bonding parts are located on both sides of the first bonding part. Energy storage element.

3. The current collector is formed of the second material. The energy storage element according to claim 1 or 2.

4. The connecting member further includes a covering member disposed to cover a periphery of a bonding interface between the first material portion and the second material portion. The energy storage element according to any one of claims 1 to 3.

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