Power storage device

Abstract

This power storage device comprises a first power storage element, a second power storage element, and a bus bar. The first power storage element and the second power storage element are disposed side by side in a first direction. The first power storage element includes a first terminal disposed in a second direction intersecting the first direction. The second power storage element includes a second terminal disposed in the second direction. The bus bar includes a second joining part and a first joining part joined to the first terminal, and a third joining part joined to the second terminal. The first joining part and the second joining part are disposed separately from each other in a third direction intersecting the first direction and the second direction. The third joining part is disposed at a central portion in the third direction.

Description

Power storage device

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

[0002] Patent Document 1 discloses a battery module including a plurality of batteries and a plurality of bus bars connecting the batteries. Each bus bar is made of a flat, plate-shaped conductive member, and both ends of the bus bar are connected to the electrode terminals of adjacent batteries by welding.

[0003] Japanese Patent Application Laid-Open No. 2018-206638

[0004] In the bus bar provided in the conventional energy storage module, the two ends welded to the upper surfaces of the two electrode terminals have the same shape around them. Therefore, for example, if the surface of one of the two electrode terminals facing the bus bar has an element (such as a protrusion) that may hinder bonding with the bus bar, the bus bar and that electrode terminal may not be bonded well. This can reduce the reliability of the energy storage device.

[0005] The present invention was made by the inventors of the present application by focusing on the above-mentioned problem, and has an object to provide a power storage device with improved reliability.

[0006] An energy storage device according to one embodiment of the present invention comprises a first storage element, a second storage element, and a bus bar, wherein the first storage element and the second storage element are arranged side by side in a first direction, the first storage element comprises a first terminal arranged in a second direction intersecting the first direction, the second storage element comprises a second terminal arranged in the second direction, the bus bar comprises a first joint portion and a second joint portion joined to the first terminal, and a third joint portion joined to the second terminal, the first joint portion and the second joint portion being arranged separately in a third direction intersecting the first direction and the second direction, and the third joint portion being arranged in a central portion of the bus bar in the third direction.

[0007] According to the present invention, it is possible to provide a power storage device with improved reliability.

[0008] FIG. 1 is a perspective view showing a configuration of an energy storage device according to an embodiment. FIG. 2 is an exploded perspective view of a busbar unit according to an embodiment. FIG. 3 is a perspective view of a busbar and two energy storage elements according to an embodiment. FIG. 4 is an enlarged perspective view showing a busbar and its surrounding configuration according to an embodiment. FIG. 5 is a plan view showing a busbar and its surrounding configuration according to an embodiment. FIG. 6 is a cross-sectional view showing a busbar and its surrounding configuration according to an embodiment. FIG. 7 is a plan view showing a busbar and its surrounding configuration according to a modified example of the embodiment.

[0009] (1) An energy storage device according to one aspect of the present invention comprises a first storage element, a second storage element, and a bus bar, wherein the first storage element and the second storage element are arranged side by side in a first direction, the first storage element comprises a first terminal arranged in a second direction intersecting the first direction, the second storage element comprises a second terminal arranged in the second direction, the bus bar comprises a first joint portion and a second joint portion joined to the first terminal, and a third joint portion joined to the second terminal, the first joint portion and the second joint portion being arranged separately in a third direction intersecting the first direction and the second direction, and the third joint portion being arranged in a central portion of the bus bar in the third direction.

[0010] According to the energy storage device described in (1) above, even if the first terminal has a portion that may impede bonding to the bus bar, the bus bar can be bonded to the first terminal at at least two locations (first and second bonding portions) while avoiding the portion. This allows the terminals (first terminal and second terminal) of the two energy storage elements (first energy storage element and second energy storage element) to be bonded well to the bus bar. Therefore, the energy storage device according to this aspect has improved reliability.

[0011] (2) In the energy storage device described in (1) above, the bus bar may have a first opening, and the first opening may be arranged between the first joint portion and the second joint portion in the third direction.

[0012] According to the energy storage device described in (2) above, for example, the bus bar can be joined to the first terminal while the first opening more reliably prevents interference between the bus bar and a protruding portion (convex portion) of the first terminal. Specifically, the bus bar can be joined to the first terminal at two locations (first and second joints) that sandwich the first opening in the third direction.

[0013] (3) In the energy storage device described in (2) above, the bus bar may include a first joining plate portion on which the first joining portion is formed, and a second joining plate portion on which the second joining portion is formed and which is arranged separately from the first joining plate portion in the third direction, and the first opening may be a gap between the first joining plate portion and the second joining plate portion.

[0014] According to the energy storage device described above in (3), the gap between the two plate-shaped portions (the first and second joining plate portions) is provided in the bus bar as the first opening, which allows the bus bar having the first opening to be efficiently manufactured.

[0015] (4) In the energy storage device described in any one of (1) to (3) above, when viewed from the second direction, at least a portion of the third junction may be aligned with the region between the first junction and the second junction in the first direction.

[0016] According to the energy storage device described in (4) above, it is easy to make the lengths of the conductive paths connecting the first and second joints, which are arranged separated in the third direction across the first opening, and the third joints equal to each other, which is advantageous for improving the conductive efficiency between the two energy storage elements, for example.

[0017] (5) In the energy storage device described in any one of (1) to (4) above, the bus bar may include a first terminal connection portion in which the first joint portion and the second joint portion are formed, a second terminal connection portion in which the third joint portion is formed, and an intermediate connection portion connecting the first terminal connection portion and the second terminal connection portion, wherein the first terminal connection portion is disposed on one side of the second terminal connection portion in the first direction, and the intermediate connection portion is connected to an end portion of the first terminal connection portion on the other side in the first direction and is also connected to an end portion of the second terminal connection portion on the other side in the first direction.

[0018] According to the energy storage device described in (5) above, the intermediate connector extends from the end of the second terminal connector on the other side in the first direction, and is connected to the first terminal connector across a space in the second direction beyond the second terminal connector, thereby efficiently absorbing misalignment of one of the first and second energy storage elements relative to the other by the intermediate connector.

[0019] (6) In the energy storage device described in (5) above, the intermediate connection portion may include a second opening portion at a position facing the third joint portion in the second direction.

[0020] According to the energy storage device described above in (6), the work for forming the third joint portion (e.g., welding) can be performed through the second opening, thereby more efficiently joining the bus bar and the second terminal.

[0021] (7) In the energy storage device described in any one of (1) to (6) above, the third junction may include a fourth junction and a fifth junction, and the fourth junction and the fifth junction may be arranged separately in the third direction.

[0022] According to the energy storage device described in (7) above, the joints between the second terminals and the bus bars are arranged so as to be separated in the third direction. This allows the length of the conductive path connecting the first joint and the third joint to be approximately the same as the length of the conductive path connecting the second joint and the third joint, and allows the lengths to be relatively short. This is advantageous for improving the conductivity between the two energy storage elements, for example.

[0023] Hereinafter, with reference to the drawings, a description will be given of an energy storage device according to an embodiment of the present invention (including modifications thereof). 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. In each drawing, dimensions and the like are not strictly illustrated. In each drawing, the same or similar components are designated by the same reference numerals.

[0024] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of terminals of an energy storage element are aligned, or the direction in which a pair of short side surfaces of a container for the energy storage element face each other. The Y-axis direction is defined as the direction in which a pair of long side surfaces of a container for the energy storage element face each other, the thickness direction (flattening direction) of the container for the energy storage element, or the direction in which multiple energy storage elements of an energy storage unit are aligned. The Z-axis direction is defined as the direction in which the terminals of the energy storage element protrude, the direction in which the container body and the cover plate of the energy storage element are aligned, the direction in which the energy storage unit and the busbar unit are aligned, or the up-down direction. The X-axis direction, Y-axis direction, and Z-axis direction intersect each other (orthogonal in this embodiment). Depending on the usage mode, the Z-axis direction may not be the up-down direction; however, for convenience of explanation, the following description will be made assuming that the Z-axis direction is the up-down direction.

[0025] In the following description, 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. Simply referring to the X-axis direction refers to both or either of the positive X-axis direction and the negative X-axis direction. References to one side and the other side of the X-axis direction refer to one and the other of the positive X-axis direction and the negative X-axis direction. The same applies to the Y-axis and Z-axis directions. Expressions indicating relative directions or orientations, such as parallel and perpendicular, may also include cases where the directions or orientations are not strictly the same. For example, two directions being parallel not only means 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. In the following description, the term "insulation" means "electrical insulation." It is preferable that the insulating material be formed from a material with a volume resistivity of 1×10 Ω-m or more.

[0026] (Embodiment) [1. General Description of Energy Storage Device 1] Fig. 1 is a perspective view showing the configuration of an energy storage device 1 according to an embodiment. Fig. 1 shows an energy storage unit 10 and a bus bar unit 400 removed from a case body 610. Fig. 2 is an exploded perspective view of the bus bar unit 400 according to the embodiment. Fig. 3 is a perspective view of a bus bar 300 and two energy storage elements 100 according to the embodiment. The two energy storage elements 100 shown in Fig. 3 are adjacent to each other in the Y-axis direction. When describing these two energy storage elements 100 separately, the energy storage element 100 in the negative Y-axis direction will be referred to as a first energy storage element 100A, and the energy storage element 100 in the positive Y-axis direction will be referred to as a second energy storage element 100B. The first energy storage element 100A and the second energy storage element 100B are two energy storage elements 100 that are arbitrarily selected from the plurality of energy storage elements 100 (see FIG. 1) included in the energy storage device 1 and are adjacent to each other in the Y-axis direction. The Y-axis direction is an example of the first direction. In the drawings from FIG. 3 onwards (FIGS. 3 to 7), the case 600, spacers 200 and 250, and busbar unit 400 shown in FIG. 1 are omitted.

[0027] The power storage device 1 is a device that can charge electricity from an external source and discharge electricity to an external source. The power storage device 1 is, for example, a battery module (battery assembly) used for power storage or power supply purposes. Specifically, the power storage device 1 is used 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, automatic guided vehicle (AGV), 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 fossil fuel (gasoline, diesel, liquefied natural gas, etc.) 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 power storage device 1 can also be used as a stationary battery for home or business use.

[0028] 1 , the energy storage device 1 includes an energy storage unit 10, a bus bar unit 400, and a case 600 that houses the energy storage unit 10. In addition to the above components, the energy storage device 1 may also include electrical devices such as a circuit board and a relay that monitor or control the charge state, discharge state, etc. of the energy storage unit 10.

[0029] In this embodiment, the energy storage unit 10 is a battery module having a plurality of energy storage elements 100. Specifically, the energy storage unit 10 includes a plurality of energy storage elements 100 (34 in this embodiment), a spacer 200 disposed between two adjacent energy storage elements 100 in the Y-axis direction, and spacers 250 disposed on the outer sides of each of the energy storage elements 100 at both ends in the Y-axis direction. The spacer 200 is also referred to as, for example, an "inter-cell spacer." The spacer 250 is also referred to as, for example, an "end spacer." In this embodiment, the spacers 200 and 250 also function as cell holders that hold one or more energy storage elements 100 disposed along the spacer 200 or 250.

[0030] The energy storage unit 10 has a generally rectangular parallelepiped shape that is long in the Y-axis direction, with a plurality of energy storage elements 100, a plurality of spacers 200, and a pair of spacers 250 arranged in the Y-axis direction. The plurality of energy storage elements 100 included in the energy storage unit 10 are electrically connected by a plurality of bus bars 300.

[0031] In this embodiment, the energy storage unit 10 is a non-constrained type module that does not include restraining members (such as end plates and side plates) that restrain the multiple energy storage elements 100 in the Y-axis direction. However, the energy storage unit 10 may include restraining members that restrain the multiple energy storage elements 100 and the multiple spacers 200 and 250 in the Y-axis direction. The energy storage unit 10 does not have to include the spacers 200 and 250. For example, when an insulating film is disposed on each of the multiple energy storage elements 100, the energy storage element 100 is electrically insulated from other members adjacent to the energy storage element 100 (such as other energy storage elements 100) by at least the insulating film disposed on the energy storage element 100.

[0032] The energy storage element 100 is a secondary battery (single cell), more specifically, a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. As shown in FIG. 3 , the energy storage element 100 includes a flat rectangular (square) container 110. The container 110 contains an electrode assembly, a current collector, an electrolyte, and other components (not shown). The electrode assembly may be, for example, a wound electrode assembly formed by winding an electrode plate and a separator. The electrode assembly may be a stacked electrode assembly formed by stacking multiple flat electrode plates, or an electrode assembly having a bellows-like structure formed by repeatedly folding long strip-shaped electrode plates. The type of electrolyte contained in the container 110 is not particularly limited as long as it does not impair the performance of the energy storage element 100, and various types can be selected. The energy storage element 100 may be a secondary battery other than a nonaqueous electrolyte secondary battery, or a capacitor. The energy storage element 100 may be a primary battery. The energy storage element 100 may be a battery using a solid electrolyte. The energy storage element 100 may be a pouch-type energy storage element. The shape of the energy storage element 100 is not limited to the above-mentioned rectangular shape, and may be other shapes such as a polygonal column shape, a cylindrical shape, an elliptical column shape, or an oblong column shape.

[0033] As shown in Fig. 3, the container 110 is a rectangular parallelepiped case having a pair of long sides 111, a pair of short sides 112, and a bottom surface 113 formed by the container body, and a terminal placement surface 130 formed by a cover plate. The rectangular parallelepiped here refers to a hexahedron with all sides being rectangular or square. After the electrode assembly and other components are housed inside the container body, the container body and the cover plate are welded together to seal the interior of the container 110. The material of the container 110 is not particularly limited, but is preferably a weldable metal such as stainless steel, aluminum, an aluminum alloy, iron, or plated steel sheet.

[0034] The energy storage element 100 includes terminals 140 arranged in the Z-axis direction. The Z-axis direction is an example of a second direction. The terminals 140 are electrically connected to an electrode assembly housed in the container 110. More specifically, a pair of terminals 140 are arranged to protrude in the positive direction of the Z-axis from a terminal arrangement surface 130 of the container 110. A gas exhaust valve 131 is further provided on the terminal arrangement surface 130. One of the pair of terminals 140 is electrically connected to the positive electrode of the electrode assembly, and the other is electrically connected to the negative electrode of the electrode assembly. Hereinafter, when distinguishing between the negative electrode terminal 140 and the positive electrode terminal 140, the negative electrode terminal 140 will be referred to as a negative electrode terminal 141, and the positive electrode terminal 140 will be referred to as a positive electrode terminal 142.

[0035] The negative electrode terminal 141 has a terminal body 141a made of aluminum or an aluminum alloy and a shaft body made of copper or a copper alloy. The shaft body is joined to the terminal body 141a while passing through the terminal body 141a, and the end of the shaft body protrudes slightly from the upper surface of the terminal body 141a (the surface facing the positive direction of the Z axis; the same applies below). This forms a terminal protrusion 141b on the terminal body 141a due to the end (see FIG. 3). The positive electrode terminal 142 is made of aluminum or an aluminum alloy and has a flat upper surface.

[0036] In this embodiment, as shown in FIG. 3 , the terminal 140 included in the first energy storage element 100A is referred to as the first terminal 140A, and the terminal 140 included in the second energy storage element 100B is referred to as the second terminal 140B. That is, the first energy storage element 100A has two first terminals 140A, that is, a negative electrode terminal 141 and a positive electrode terminal 142, and the second energy storage element 100B has two second terminals 140B, that is, a negative electrode terminal 141 and a positive electrode terminal 142. When the first energy storage element 100A and the second energy storage element 100B are aligned in the Y-axis direction, the first terminal 140A and the second terminal 140B are aligned in the Y-axis direction. In this state, one of the first terminal 140A and the second terminal 140B is the negative electrode terminal 141, and the other is the positive electrode terminal 142. FIG. 3 shows that a negative electrode terminal 141 serving as a first terminal 140A and a positive electrode terminal 142 serving as a second terminal 140B are connected by a bus bar 300.

[0037] As shown in FIG. 3 , bus bar 300, which electrically and mechanically connects first terminal 140A and second terminal 140B, includes first terminal connection portion 310, second terminal connection portion 320, and intermediate connection portion 350. First terminal connection portion 310 and second terminal connection portion 320 are each a plate-like portion joined to the upper surface of terminal 140. Intermediate connection portion 350 is a plate-like portion that connects first terminal connection portion 310 and second terminal connection portion 320. In the present embodiment, intermediate connection portion 350 is integral with first terminal connection portion 310 and second terminal connection portion 320. The configuration of bus bar 300 and its surroundings will be described later using FIGS. 4 to 6 .

[0038] The case 600 is a container having a substantially rectangular parallelepiped (box-like) shape that houses the energy storage unit 10. The case 600 is disposed outside the energy storage unit 10 and protects the energy storage unit 10 from impacts and the like. The case 600 is formed from a metal member such as aluminum, an aluminum alloy, stainless steel, iron, or a plated steel plate. In this embodiment, the case 600 is formed by die-casting aluminum (aluminum die-casting). Instead of the case 600, a case formed from an insulating member such as a resin material may be used as the case that houses the energy storage unit 10.

[0039] As shown in FIG. 1 , the case 600 has a case main body 610. The case main body 610 is a housing (enclosure) having an opening 610a formed in the positive direction of the Z axis and sized to allow insertion of the power storage unit 10. The case main body 610 includes a case side wall 611 facing the power storage unit 10 in the X axis direction, a case side wall 612 facing the power storage unit 10 in the Y axis direction, and a case bottom wall 615 supporting the power storage unit 10 from the negative direction of the Z axis. The X axis direction is an example of a third direction. The case 600 may further include a lid (not shown) that closes the opening 610a of the case main body 610.

[0040] The busbar unit 400 includes a plurality of busbars 300, a busbar holder 401 that holds the busbars 300, and a wiring substrate 500. The busbar unit 400 is disposed opposite the energy storage unit 10 in the Z-axis direction. The busbar holder 401 is a member formed of an insulating material such as resin, and includes a plurality of busbar accommodating sections 405 that accommodate the busbars 300. The busbar accommodating sections 405 are box-shaped sections that accommodate and hold the busbars 300 with their lower surfaces (surfaces facing the negative Z-axis direction) exposed. In this embodiment, as shown in FIGS. 1 to 3 , two energy storage elements 100 adjacent in the Y-axis direction are connected in series by the busbars 300. That is, the plurality of energy storage elements 100 included in the energy storage unit 10 are connected in series by the busbars 300. Each of the plurality of busbars 300 is held in a busbar accommodating section 405 located at a position corresponding to the busbar 300. In this embodiment, a bus bar 382 is joined to the negative electrode terminal 141 of the energy storage element 100 at the end of the energy storage unit 10 facing in the positive direction of the Y axis, and a bus bar 381 is joined to the positive electrode terminal 142 of the energy storage element 100 at the end of the energy storage unit 10 facing in the negative direction of the Y axis. These bus bars 382 and 381 are also held by a bus bar holder 401.

[0041] 2 , the bus bar 382 is provided with a negative electrode general terminal 392 that protrudes in the positive direction of the Z axis, and the bus bar 381 is provided with a positive electrode general terminal 391 that protrudes in the positive direction of the Z axis. The negative electrode general terminal 392 and the positive electrode general terminal 391 are connected to another device via a cable or the like, so that the energy storage device 1 supplies power to the other device. The energy storage device 1 may be charged with power supplied from the other device instead of or in addition to supplying power to the other device. The negative electrode general terminal 392 and the positive electrode general terminal 391 may each protrude from the inside to the outside of the case 600 and be used as an external terminal.

[0042] As shown in FIG. 2 , the bus bar holder 401 includes a substrate support portion 490 that supports the wiring substrate 500 at the center in the X-axis direction. The wiring substrate 500 supported by the substrate support portion 490 includes a substrate formed of an insulating material and conductive wiring formed on the substrate. Multiple conductive members 590 are connected to the wiring substrate 500, and each of the multiple conductive members 590 is connected to one of the bus bars 300, 381, or 382. A connector 510 is connected to the end of the wiring substrate 500 in the positive direction of the Y-axis. A control device that controls the charging and discharging of the energy storage device 1 is connected to the connector 510, for example. The control device detects the voltages of the multiple energy storage elements 100 via the multiple conductive members 590 and the wiring substrate 500 and controls the charging and discharging of the multiple energy storage elements 100 based on the detection results. That is, in this embodiment, the conductive members 590 are terminals for voltage detection (detection terminals).

[0043] [2. Configuration of Bus Bar 300 and Its Surrounding Area] Next, the configuration of bus bar 300 and its surrounding area will be described using Figures 4 to 6 in addition to Figures 1 to 3 described above. Below, attention is focused on one bus bar 300 that electrically connects two adjacent energy storage elements 100 (first energy storage element 100A and second energy storage element 100B), and the configuration of bus bar 300 and its surrounding area will be described.

[0044] FIG. 4 is an enlarged perspective view showing the bus bar 300 and its surrounding configuration according to the embodiment. FIG. 5 is a plan view (viewed from the positive direction of the Z axis) showing the bus bar 300 and its surrounding configuration according to the embodiment. In FIGS. 4 and 5, the first bonding portion 331, the second bonding portion 332, and the third bonding portion 333 are each schematically represented by annular dotted lines. FIG. 6 is a cross-sectional view showing the bus bar 300 and its surrounding configuration according to the embodiment. FIG. 6 simply illustrates the cross section taken along line VI-VI in FIG. 5. In FIG. 6, the two energy storage elements 100 are simply illustrated as side views rather than cross sections. In FIG. 6, the approximate arrangement ranges of the first bonding portion 331 and the third bonding portion 333 in the X axis direction are indicated by dotted regions.

[0045] 4 to 6 , the bus bar 300 is joined to the first terminal 140A of the first energy storage element 100A and the second terminal 140B of the second energy storage element 100B. Specifically, the bus bar 300 includes a first joint portion 331 and a second joint portion 332 joined to the first terminal 140A, and a third joint portion 333 joined to the second terminal 140B. The first joint portion 331 and the second joint portion 332 are arranged separately in the X-axis direction.

[0046] The bus bar 300 is joined to each of the first terminal 140A and the second terminal 140B by, for example, laser welding. That is, each of the first joint 331, the second joint 332, and the third joint 333 is formed by, for example, laser welding. Each of these joints (the first joint 331, the second joint 332, and the third joint 333; the same applies below) may be formed in an annular shape as shown in FIGS. 4 and 5 , or in an annular shape with a missing portion (e.g., a C-shape or a G-shape). Each of these joints does not have to be formed in an annular shape, but may be formed in a linear shape or a line shape with at least a curved or bent portion (e.g., a V-shape or a U-shape). Each of these joints does not have to be formed in a linear shape, but may be formed in a continuous plane within a predetermined range in a plan view.

[0047] In the present embodiment, more specifically, bus bar 300 includes first terminal connection portion 310 joined to first terminal 140A, second terminal connection portion 320 joined to second terminal 140B, and intermediate connection portion 350 connecting first terminal connection portion 310 and second terminal connection portion 320. That is, first terminal connection portion 310 includes first joint portion 331 and second joint portion 332, and second terminal connection portion 320 includes third joint portion 333.

[0048] In this embodiment, as shown in Figures 4 and 5, the first terminal connection portion 310 includes two plate-shaped portions spaced apart in the X-axis direction. Specifically, as shown in Figures 3 to 5, the first terminal connection portion 310 includes a first bonding plate portion 311 and a second bonding plate portion 312. A first bonding portion 331 is formed in the first bonding plate portion 311, and a second bonding portion 332 is formed in the second bonding plate portion 312. In this embodiment, as shown in Figures 4 and 5, a first opening 319 is formed by a gap between the first bonding plate portion 311 and the second bonding plate portion 312, and the terminal protrusion 141b of the first terminal 140A is disposed in the first opening 319.

[0049] That is, in the present embodiment, first terminal 140A, which is negative terminal 141, has a terminal protrusion 141b formed by the end of the shaft protruding from the upper surface of terminal body 141a (see FIGS. 3, 4, and 6). Therefore, in order to properly join bus bar 300 to the upper surface of terminal body 141a, it is preferable to avoid interference between bus bar 300 and terminal protrusion 141b.

[0050] More specifically, the upper surface of the terminal body 141a and the upper end surface of the terminal protrusion 141b are positioned at different positions in the Z-axis direction. Therefore, for example, it is not easy to shape the first terminal connection portion 310 of the bus bar 300 so that it makes accurate surface contact with both the upper surface of the terminal body 141a and the upper end surface of the terminal protrusion 141b. Furthermore, the material of the shaft forming the terminal protrusion 141b is, for example, a copper alloy, and the material of the terminal body 141a is, for example, an aluminum alloy. Therefore, there is also the problem that it is relatively difficult to join the bus bar 300, which is made of, for example, an aluminum alloy, to the terminal protrusion 141b by welding.

[0051] Therefore, in the present embodiment, the portions of bus bar 300 that are joined to first terminal 140A (first joint portion 331 and second joint portion 332) are arranged to be separated in the X-axis direction. That is, by arranging terminal protrusion 141b of first terminal 140A between first joint portion 331 and second joint portion 332, interference between bus bar 300 and terminal protrusion 141b can be avoided.

[0052] Furthermore, as shown in FIG. 5 , third joint portion 333, which is a portion of busbar 300 that is joined to second terminal 140B, is located at the center of busbar 300 in the X-axis direction. More specifically, the center of third joint portion 333 in the X-axis direction is included in the center of busbar 300 in the X-axis direction. In the present embodiment, the center of busbar 300 in the X-axis direction is, for example, a range that includes the center line of busbar 300 in the X-axis direction (coincident with line VI-VI in FIG. 5 ) and is a range that is one-third of the maximum width of busbar 300 in the X-axis direction. In the present embodiment, second terminal connection portion 320 including third joint portion 333 has a shape that is symmetrical with respect to the center line (line VI-VI) of busbar 300 in the X-axis direction, as shown in FIG. 5 . Therefore, it can also be said that third joint portion 333 is located at the center of second terminal connection portion 320 in the X-axis direction. That is, the first terminal connection portion 310 of the bus bar 300 according to the present embodiment is joined to the first terminal 140A at two joints (a first joint 331 and a second joint 332) that are separated in the X-axis direction. Furthermore, the region between the first joint 331 and the second joint 332 in the X-axis direction and at least a part of the third joint 333 are aligned in the Y-axis direction.

[0053] As described above, the energy storage device 1 according to the present embodiment includes a first energy storage element 100A, a second energy storage element 100B, and a bus bar 300. The first energy storage element 100A and the second energy storage element 100B are arranged side by side in the Y-axis direction. The first energy storage element 100A includes a first terminal 140A arranged in the Z-axis direction intersecting the Y-axis direction. The second energy storage element 100B includes a second terminal 140B arranged in the Z-axis direction. The bus bar 300 includes a first joint portion 331 and a second joint portion 332 joined to the first terminal 140A, and a third joint portion 333 joined to the second terminal 140B. The first joint portion 331 and the second joint portion 332 are arranged separately in the X-axis direction intersecting the Y-axis direction and the Z-axis direction. The third joint portion 333 is arranged in the center of the bus bar 300 in the X-axis direction.

[0054] That is, the bus bar 300 according to this embodiment includes a first joint portion 331 and a second joint portion 332 separated in the X-axis direction as joint portions with the first terminal 140A. Therefore, the bus bar 300 can be joined to the first terminal 140A at at least two locations (the first joint portion 331 and the second joint portion 332) while avoiding a portion of the first terminal 140A that may impede joining to the bus bar 300 (the terminal protrusion 141b in this embodiment). This allows favorable joining between the bus bar 300 and the terminals 140 (the first terminal 140A and the second terminal 140B) of the two energy storage elements 100 (the first energy storage element 100A and the second energy storage element 100B). Therefore, the energy storage device 1 according to this embodiment is an energy storage device with improved reliability.

[0055] Furthermore, the third joint 333, which is the joint portion of the bus bar 300 with the second terminal 140B, is located at the center of the bus bar 300 in the X-axis direction. Therefore, it is possible to reduce the difference between the length of the conductive path connecting the first joint 331 and the third joint 333 and the length of the conductive path connecting the second joint 332 and the third joint 333. This improves the conductivity efficiency between the first energy storage element 100A and the second energy storage element 100B, resulting in efficient discharging and charging of the energy storage device 1. This also contributes to improving the reliability of the energy storage device 1.

[0056] 4 and 5, the bus bar 300 according to this embodiment includes a first opening 319. The first opening 319 is disposed between the first joint portion 331 and the second joint portion 332 in the X-axis direction.

[0057] According to this configuration, bus bar 300 can be joined to first terminal 140A while first opening 319 more reliably prevents interference between terminal protrusion 141b of first terminal 140A and bus bar 300. Specifically, bus bar 300 can be joined to first terminal 140A at two locations (first joint portion 331 and second joint portion 332) that sandwich first opening 319 in the X-axis direction.

[0058] It is not essential that the bus bar 300 include the first opening 319 between the first joint portion 331 and the second joint portion 332. For example, instead of the first opening 319, a recess recessed in the positive direction of the Z axis may be provided. That is, the first terminal connection portion 310 may include a recess recessed in the positive direction of the Z axis, disposed between the first joint portion 331 and the second joint portion 332. Even in this case, the presence of a recess in the first terminal connection portion 310 at a position facing the terminal protrusion 141b in the Z axis direction allows the bus bar 300 to be joined to the first terminal 140A while avoiding interference between the bus bar 300 and the terminal protrusion 141b. However, from the viewpoint of more reliably avoiding interference between the bus bar 300 and the terminal protrusion 141b, it is preferable that the bus bar 300 include the first opening 319 penetrating the bus bar 300 between the first joint portion 331 and the second joint portion 332.

[0059] The size and shape of the first opening 319 in plan view do not need to be the size and shape shown in Figures 4 and 5. The size and shape of the first opening 319 may be any size and shape that includes the terminal protrusion 141b in plan view.

[0060] More specifically, the bus bar 300 includes a first bonding plate portion 311 having a first bonding portion 331 formed therein, and a second bonding plate portion 312 having a second bonding portion 332 formed therein. The second bonding plate portion 312 is disposed so as to be separated from the first bonding plate portion 311 in the X-axis direction. The first opening 319 is a gap between the first bonding plate portion 311 and the second bonding plate portion 312.

[0061] As described above, in this embodiment, the gap (space) between the two plate-like portions (first bonding plate portion 311 and second bonding plate portion 312) is provided in bus bar 300 as first opening 319. Therefore, first opening 319 can be formed more easily than when, for example, a substantially circular through-hole that matches the position, size, and shape of terminal protrusion 141b is formed in bus bar 300. Therefore, bus bar 300 having first opening 319 can be produced efficiently.

[0062] In this embodiment, the positional relationship between the first bonding portion 331, the second bonding portion 332, and the third bonding portion 333 is described, for example, as follows: When viewed from the Z-axis direction, at least a portion of the third bonding portion 333 is aligned in the Y-axis direction with the region between the first bonding portion 331 and the second bonding portion 332. More specifically, in this embodiment, the first opening 319 is provided between the first bonding portion 331 and the second bonding portion 332, and the first opening 319 and at least a portion of the third bonding portion 333 are aligned in the Y-axis direction.

[0063] This configuration makes it easier to make the lengths of the conductive paths connecting the first bonding portion 331 and the second bonding portion 332, which are arranged separated in the X-axis direction across the first opening 319, to the third bonding portion 333 the same. This is advantageous for improving the conductivity efficiency between the first energy storage element 100A and the second energy storage element 100B, for example.

[0064] First bonding plate portion 311 and second bonding plate portion 312 of bus bar 300 are both portions that are bonded to first terminals 140A, and both are part of a first terminal connection portion 310 that bus bar 300 includes. That is, as shown in FIGS. 4 to 6 , bus bar 300 includes first terminal connection portion 310 in which first bonding portion 331 and second bonding portion 332 are formed, second terminal connection portion 320 in which third bonding portion 333 is formed, and intermediate connection portion 350. Intermediate connection portion 350 connects first terminal connection portion 310 and second terminal connection portion 320. First terminal connection portion 310 is disposed on one side of second terminal connection portion 320 in the Y-axis direction (in the negative Y-axis direction in this embodiment). Intermediate connection portion 350 is connected to the end portion of first terminal connection portion 310 on the other side in the Y-axis direction (the positive Y-axis direction in this embodiment), and is also connected to the end portion of second terminal connection portion 320 on the other side in the Y-axis direction (the positive Y-axis direction in this embodiment). In other words, intermediate connection portion 350 connects the end portion of first terminal connection portion 310 on the positive Y-axis direction and the end portion of second terminal connection portion 320 on the positive Y-axis direction.

[0065] As described above, in the bus bar 300 according to the present embodiment, the intermediate connection portion 350 extends from the end portion of the second terminal connection portion 320 in the positive Y-axis direction, crosses the Y-axis direction through a space above the second terminal connection portion 320 (in the positive Z-axis direction), and is connected to the first terminal connection portion 310. In other words, the intermediate connection portion 350 extends from the end portion of the first terminal connection portion 310 in the positive Y-axis direction, crosses the Y-axis direction through a space above the second terminal connection portion 320 (in the positive Z-axis direction), and is connected to the second terminal connection portion 320. This allows the intermediate connection portion 350 to efficiently absorb any misalignment of one of the first energy storage element 100A and the second energy storage element 100B relative to the other.

[0066] More specifically, as shown in FIGS. 4 to 6 , the intermediate connection portion 350 of the bus bar 300 includes a first intermediate portion 351, a second intermediate portion 352, and a third intermediate portion 355. The first intermediate portion 351 is connected to the end of the first terminal connection portion 310 facing the positive direction of the Y axis and extends in the positive direction of the Z axis. The second intermediate portion 352 is connected to the end of the second terminal connection portion 320 facing the positive direction of the Y axis and extends in the positive direction of the Z axis. The first intermediate portion 351 and the second intermediate portion 352 are both flat and parallel to the XZ plane. The third intermediate portion 355 is connected to the end of each of the first intermediate portion 351 and the second intermediate portion 352 facing the positive direction of the Z axis. The third intermediate portion 355 is flat and parallel to the XY plane. As described above, in the bus bar 300 according to this embodiment, the portion formed by the intermediate connection portion 350 and the second terminal connection portion 320 is formed in a rectangular cylindrical shape.

[0067] The shape of the intermediate connection portion 350 is not limited thereto. The shape of the intermediate connection portion 350 is not particularly limited as long as it connects the first terminal connection portion 310 and the second terminal connection portion 320. For example, the intermediate connection portion 350 may be a continuous plate-like portion that connects the first terminal connection portion 310 and the second terminal connection portion 320 and is curved in the Z-axis direction as a whole. The intermediate connection portion 350 may be a plate-like portion that connects the first terminal connection portion 310 and the second terminal connection portion 320 and is curved or bent in only one or three or more places when viewed from the X-axis direction. Furthermore, the intermediate connection portion 350 may be, for example, a flat portion that connects the ends of the first terminal connection portion 310 and the second terminal connection portion 320 that face each other along the Y-axis. In other words, the busbar 300 does not necessarily have to have a three-dimensional shape as shown in FIG. 4 .

[0068] An opening is formed in the intermediate connection portion 350 included in the bus bar 300 according to this embodiment. Specifically, the intermediate connection portion 350 includes a second opening 359 at a position facing the third joint portion 333 in the Z-axis direction. More specifically, the third intermediate portion 355 includes two portions (third intermediate portion 355a and third intermediate portion 355b) separated in the X-axis direction, as shown in FIG. 5 . The second opening 359 is a gap (space) between the third intermediate portion 355a and the third intermediate portion 355b in the intermediate connection portion 350.

[0069] According to this configuration, the work of forming the third joint portion 333 (for example, laser welding) can be performed through the second opening 359. This allows the bus bar 300 and the second terminal 140B to be joined more efficiently.

[0070] The above describes the energy storage device 1 according to the embodiment, focusing on the bus bar 300 and the surrounding configuration. However, the energy storage device 1 may have a bus bar 300 and the surrounding configuration different from those shown in Figures 2 to 6. Therefore, modifications of the energy storage device 1 will be described below, focusing on the differences from the above embodiment.

[0071] 7 is a plan view showing a bus bar 300 and its peripheral configuration according to a modification of the embodiment. As shown in FIG. 7 , the energy storage device 1a according to this modification includes a bus bar 300 joined to the first terminal 140A of the first energy storage element 100A and the second terminal 140B of the second energy storage element 100B. The bus bar 300 includes a first joint 331 and a second joint 332 joined to the first terminal 140A, and a third joint 333a joined to the second terminal 140B. The first joint 331 and the second joint 332 are arranged separately in the X-axis direction. The third joint 333a is arranged in the center of the bus bar 300 in the X-axis direction. These configurations are common to the energy storage device 1 according to the embodiment.

[0072] In this modified example, the third joint portion 333a includes a fourth joint portion 334 and a fifth joint portion 335, and the fourth joint portion 334 and the fifth joint portion 335 are arranged separately in the X-axis direction.

[0073] As described above, in this modification, the second terminal 140B and the bus bar 300 are joined at two locations, the fourth joint 334 and the fifth joint 335, which are spaced apart in the X-axis direction. This allows the length of the conductive path connecting the first joint 331 and the third joint 333a to be approximately the same as the length of the conductive path connecting the second joint 332 and the third joint 333a, and also allows these lengths to be relatively short. This is advantageous for improving the conduction efficiency between the first energy storage element 100A and the second energy storage element 100B, for example. In this modification, of the fourth joint 334 and the fifth joint 335, the fourth joint 334 is closer to the first joint 331 than the fifth joint 335. Of the fourth joint 334 and the fifth joint 335, the fifth joint 335 is closer to the second joint 332 than the fourth joint 334. Therefore, the length of the conductive path connecting the first joint 331 and the third joint 333a is the length of the conductive path connecting the first joint 331 and the fourth joint 334. The length of the conductive path connecting the second joint 332 and the third joint 333a is the length of the conductive path connecting the second joint 332 and the fifth joint 335.

[0074] In this modification, the mechanical connection portions (fourth joint portion 334 and fifth joint portion 335) between the bus bar 300 and the second terminal 140B are arranged separately in the X-axis direction, which allows the bus bar 300 to be more stably fixed to the second terminal 140B. Furthermore, it is easy to increase the area of ​​the third joint portion 333a in a plan view, that is, to increase the joint area between the bus bar 300 and the second terminal connection portion 320.

[0075] The third bonding portion 333a formed in the second terminal connection portion 320 may further include one or more bonding portions bonded to the second terminal 140B, for example, between the fourth bonding portion 334 and the fifth bonding portion 335. In other words, the third bonding portion 333a may include three or more bonding portions that are arranged separately from one another.

[0076] The position, shape and size of each of the multiple joints provided in the third joint 333a may be determined appropriately, for example, depending on the joint area or joint strength between the second terminal connection portion 320 and the second terminal 140B required for the storage device 1a.

[0077] [4. Other Modifications] The energy storage devices 1 and 1a according to the embodiments of the present invention and their modifications have been described above, but the present invention is not limited to the above-described embodiments and modifications. The embodiments and modifications disclosed herein are illustrative in all respects, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0078] In the intermediate connection portion 350 of the busbar 300, the first intermediate portion 351 and the second intermediate portion 352 may each be composed of two portions separated in the X-axis direction, similar to the third intermediate portion 355. For example, consider a case where both the first intermediate portion 351 and the second intermediate portion 352 are composed of two portions separated in the X-axis direction. In this case, for example, the first intermediate portion 351, the second intermediate portion 352, and the first terminal connection portion 310 are formed by two plate-shaped portions extending from both ends in the X-axis direction at the end of the second terminal connection portion 320 in the positive Y-axis direction. In other words, the first bonding plate portion 311 and the second bonding plate portion 312 of the first terminal connection portion 310 may be formed by the tip ends of the two plate-shaped portions extending from the second terminal connection portion 320. This can reduce the amount of metal material used in the busbar 300 or the weight of the busbar 300.

[0079] First terminal connection portions 310 of bus bar 300 do not need to be separated in the X-axis direction. In other words, first terminal connection portions 310 may be a single plate-like portion that is a part of bus bar 300 and is not separated in the X-axis direction. In this case, as described above, first terminal connection portions 310 may have a recess recessed in the positive Z-axis direction or a through-hole penetrating in the thickness direction (Z-axis direction), thereby allowing first terminal connection portions 310 to be joined to first terminals 140A while avoiding interference with terminal protrusions 141b (see FIG. 4 ).

[0080] Bus bar 300 does not need to include second opening 359. For example, consider a case where the distance in the Z-axis direction (see FIG. 6 ) between third intermediate portion 355 of intermediate connection portion 350 and second terminal connection portion 320 is relatively long. In this case, second terminal connection portion 320 may be joined to second terminal 140B by irradiating second terminal connection portion 320 with a laser beam for welding, for example, passing laterally (in the positive or negative X-axis direction) through third intermediate portion 355.

[0081] Terminal protrusion 141b formed on first terminal 140A does not have to be formed by the end of the shaft portion of first terminal 140A. For example, terminal protrusion 141b may be a part of terminal body 141a that protrudes from the upper surface of terminal body 141a.

[0082] The busbar unit 400 may not include the busbar holder 401. For example, the spacer 200 (see FIG. 2) arranged along the long side surface 111 (see FIG. 3) of the energy storage element 100 may have a portion for holding the busbar 300. The busbar unit 400 may not include the wiring board 500. For example, a coated electric wire for voltage detection may be electrically connected to each of the multiple busbars 300. In other words, the voltages of the multiple energy storage elements 100 may be detected via the multiple coated electric wires.

[0083] The energy storage device 1 does not need to include the case 600. For example, a structure including the energy storage elements 100, the spacers 200, the bus bars 300, and the bus bar holders 401 may be housed in some kind of device, a rack, or the like as the energy storage device 1.

[0084] Any combination of the components of the above-described embodiment and its modifications is also included within the scope of the present invention.

[0085] The present invention can be applied to an electricity storage device or the like that includes an electricity storage element such as a lithium ion secondary battery.

[0086] REFERENCE SIGNS LIST 1, 1a Energy storage device 100 Energy storage element 100A First energy storage element 100B Second energy storage element 140 Terminal 140A First terminal 140B Second terminal 141 Negative electrode terminal 141a Terminal body 141b Terminal protrusion 142 Positive electrode terminal 300, 381, 382 Bus bar 310 First terminal connection portion 311 First bonding plate portion 312 Second bonding plate portion 319 First opening 320 Second terminal connection portion 331 First bonding portion 332 Second bonding portion 333, 333a Third bonding portion 334 Fourth bonding portion 335 Fifth bonding portion 350 Intermediate connection portion 351 First intermediate portion 352 Second intermediate portion 355, 355a, 355b Third intermediate portion 359 Second opening

Claims

1. An energy storage device comprising: a first storage element, a second storage element, and a bus bar, wherein the first storage element and the second storage element are arranged side by side in a first direction, the first storage element has a first terminal arranged in a second direction intersecting the first direction, the second storage element has a second terminal arranged in the second direction, the bus bar comprises a first joint and a second joint joined to the first terminal, and a third joint joined to the second terminal, the first joint and the second joint are arranged separately in a third direction intersecting the first direction and the second direction, and the third joint is arranged in a central portion of the bus bar in the third direction.

2. The energy storage device according to claim 1, wherein the bus bar has a first opening, and the first opening is disposed between the first joint portion and the second joint portion in the third direction.

3. The energy storage device according to claim 2, wherein the busbar comprises a first joining plate portion in which the first joining portion is formed, and a second joining plate portion in which the second joining portion is formed and which is arranged separated from the first joining plate portion in the third direction, and the first opening is a gap between the first joining plate portion and the second joining plate portion.

4. The energy storage device according to any one of claims 1 to 3, wherein when viewed from the second direction, at least a portion of the third joint is aligned in the first direction with a region between the first joint and the second joint.

5. The energy storage device according to any one of claims 1 to 3, wherein the bus bar comprises: a first terminal connection portion in which the first joint portion and the second joint portion are formed; a second terminal connection portion in which the third joint portion is formed; and an intermediate connection portion connecting the first terminal connection portion and the second terminal connection portion, wherein the first terminal connection portion is disposed on one side of the second terminal connection portion in the first direction, and the intermediate connection portion is connected to an end portion of the first terminal connection portion on the other side in the first direction, and is connected to an end portion of the second terminal connection portion on the other side in the first direction.

6. The energy storage device according to claim 5, wherein the intermediate connection portion has a second opening at a position facing the third joint portion in the second direction.

7. The energy storage device according to any one of claims 1 to 3, wherein the third joint comprises a fourth joint and a fifth joint, and the fourth joint and the fifth joint are arranged separately in the third direction.

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