Electric storage device and method for manufacturing the same

Abstract

An electrical storage device (1) comprising an electrical storage element (10) and a busbar (20) is provided with an electrode terminal (200) (electroconductive member) joined to the busbar (20). A joining part (40) of the busbar (20) and the electrode terminal (200) has: a surface melting mark (41) at which the surface of one (busbar (20)) of the busbar (20) and the electrode terminal (200) is melted; an internal melting mark (42) at which a location toward the interior from the surface of said one (busbar (20)) is melted, the internal melting mark (42) being positioned adjacent to the surface melting mark (41); and a first welding mark (43) at which the busbar (20) and the electrode terminal (200) are welded, the first welding mark (43) being positioned adjacent to the internal melting mark (42).

Description

Technical Field

[0001] The present invention relates to a power storage device including a power storage element and a bus bar, and a method for manufacturing the same.

Background Art

[0002] Conventionally, a power storage device including a power storage element and a bus bar, in which the bus bar and a conductive member are joined by welding, is known. Patent Document 1 discloses a welding structure in which a bus bar (first member: aluminum bus bar) and a conductive member (second member: nickel-plated copper terminal) are joined by laser welding.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional configuration, there is a risk of significantly affecting the quality of the power storage device due to a decrease in welding quality or the occurrence of a short circuit.

[0005] An object of the present invention is to provide a power storage device and a method for manufacturing the same that can suppress a decrease in quality.

Means for Solving the Problems

[0006] A power storage device according to an aspect of the present invention is a power storage device including a power storage element and a bus bar, comprising a conductive member joined to the bus bar, wherein a joint portion of the bus bar and the conductive member includes a surface melting mark in which one surface of the bus bar and the conductive member is melted, an internal melting mark that is disposed adjacent to the surface melting mark and is melted from the one surface to the inside, and a first welding mark that is disposed adjacent to the internal melting mark and in which the bus bar and the conductive member are welded.

[0007] The present invention can be realized not only as such a power storage device, but also as a joining structure or method of a bus bar and a conductive member, or a manufacturing method of a power storage device including the joining method.

Effects of the Invention

[0008] According to the power storage device and the like in the present invention, deterioration in quality can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10A

Figure 10B

Modes for Carrying Out the Invention

[0010] In the conventional welding structure as described above, since the bus bar and the conductive member are joined by laser welding, spatter may be generated during laser welding. When spatter is generated, there is a risk that the welding quality may deteriorate due to insufficient strength at the welding location. Spatter may adhere to electrical equipment such as a substrate and cause a short circuit, spatter may adhere to the containers of the energy storage elements and cause a short circuit between the containers of the energy storage elements, or spatter may adhere to the heat seal portion of the exterior body that houses the energy storage elements, resulting in a poor joint in the heat seal portion. Thus, in the conventional configuration, there is a risk of significantly affecting the quality of the energy storage device due to a decrease in welding quality or the occurrence of a short circuit.

[0011] The present invention has been made by the inventors of the present application newly paying attention to the above problems, and an object thereof is to provide an energy storage device capable of suppressing a decrease in quality and a method for manufacturing the same.

[0012] In order to achieve the above object, an energy storage device according to an aspect of the present invention is an energy storage device including an energy storage element and a bus bar, including a conductive member joined to the bus bar, and a joint portion of the bus bar and the conductive member has a surface melting mark where one surface of the bus bar and the conductive member is melted, an internal melting mark disposed adjacent to the surface melting mark and melted from the one surface to the inside, and a first welding mark where the bus bar and the conductive member are welded, disposed adjacent to the internal melting mark.

[0013] According to this, in the power storage device, the joint portion of the bus bar and the conductive member has a surface melting mark where one surface of the bus bar and the conductive member is melted, an internal melting mark that is melted from the one surface to the inside, and a first welding mark where the bus bar and the conductive member are welded. That is, during laser welding, the laser output is reduced to melt one surface of the bus bar and the conductive member to form a surface melting mark, and the laser output is slightly increased to form an internal melting mark that is melted from the one surface to the inside. The laser output is further increased to weld the bus bar and the conductive member to form a first welding mark. In this way, since the welding target portion is preheated by gradually increasing the laser output from in front of the welding target portion to form the surface melting mark and the internal melting mark, the laser output when forming the first welding mark on the welding target portion can be suppressed. If the laser output can be suppressed, the generation of spatter can be suppressed. As a result, it is possible to suppress the influence of spatter on the quality of the power storage device, and thus it is possible to suppress a decrease in the quality of the power storage device.

[0014] The joint portion further has a second welding mark that extends along the first welding mark and is arranged in the extending direction of the first welding mark. The second welding mark may have a welding mark end portion that is far from the surface melting mark and where a molten pool mark is not formed.

[0015] According to this, the joint of the bus bar and the conductive member has a second weld mark along the first weld mark, and the second weld mark has a weld mark end portion where a molten pool mark is not formed at a position far from the surface melting mark. In this way, when forming the second weld mark to increase the joint strength at the joint, by forming the second weld mark along the first weld mark, the heat in the first weld mark can be used for preheating in the second weld mark. In particular, since no molten pool mark is formed at the weld mark end portion far from the surface melting mark of the second weld mark, it can be determined that the second weld mark starts welding from the weld mark end portion. Therefore, by starting welding from the weld mark end portion at the end of the first weld mark, the heat at the end after forming the first weld mark can be used as preheating, and the welding of the second weld mark can be started. Thereby, when forming the second weld mark, the laser output can be suppressed, so that the generation of spatter can be suppressed. Therefore, even when forming the second weld mark, it is possible to suppress the influence of spatter on the quality of the power storage device, and thus suppress the deterioration of the quality of the power storage device.

[0016] The second weld mark may be arranged to extend along the first weld mark from one end to the other end of the first weld mark in the extending direction.

[0017] According to this, since the second weld mark extends along the first weld mark from one end to the other end of the first weld mark, the bus bar and the conductive member can be joined more firmly. Thereby, it is possible to suppress the generation of spatter while improving the joint strength at the joint, and thus suppress the deterioration of the quality of the power storage device.

[0018] The second weld mark may be arranged to extend along the first weld mark from the weld mark end portion to a position farther from the surface melting mark than the boundary position between the surface melting mark and the internal melting mark.

[0019] The joining of the bus bar and the conductive member is performed by the first weld mark, and the surface melting mark and the internal melting mark are parts that do not contribute to the joining of the bus bar and the conductive member (parts that did not require welding). Therefore, it is not necessary to form the second weld mark at positions corresponding to the surface melting mark and the internal melting mark either. The formation position of the second weld mark is set from the end of the weld mark to a position farther from the surface melting mark than the boundary position between the surface melting mark and the internal melting mark. This can suppress the formation of the second weld mark at unnecessary positions, the increase in the welding temperature, and the occurrence of spatter. Therefore, since the influence of spatter on the quality of the power storage device can be suppressed, a decrease in the quality of the power storage device can be suppressed.

[0020] The boundary position between the surface melting mark and the internal melting mark may be a position where at least one of the width and depth of the melting mark changes when reaching the internal melting mark from the surface melting mark.

[0021] By changing at least one of the width and depth of the melting mark in the surface melting mark, it is possible to transition from the surface melting mark to the internal melting mark.

[0022] At least a part of the first weld mark and the second weld mark may be connected.

[0023] According to this, by forming the first weld mark and the second weld mark so that at least a part of them is connected (overlapped), the heat in the first weld mark can be effectively utilized as preheating to form the second weld mark. Thereby, when forming the second weld mark, the laser output can be suppressed, and the occurrence of spatter can be suppressed. Therefore, when forming the second weld mark, since the influence of spatter on the quality of the power storage device can be suppressed, a decrease in the quality of the power storage device can be suppressed.

[0024] A method for manufacturing a power storage device according to an aspect of the present invention is a method for manufacturing a power storage device including a power storage element and a bus bar, and includes a joining step of joining the bus bar and a conductive member. In the joining step, a surface melting mark is formed on one surface of the bus bar and the conductive member, an internal melting mark that is melted from the one surface to the inside is formed adjacent to the surface melting mark, and a first welding mark where the bus bar and the conductive member are welded is formed adjacent to the internal melting mark. According to this, as described above, since sputtering can be suppressed from affecting the quality of the power storage device, a decrease in the quality of the power storage device can be suppressed.

[0025] Hereinafter, a power storage device and a method for manufacturing the same according to an embodiment (including a modified example thereof) of the present invention will be described with reference to the drawings. The embodiments described below are all illustrative of comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, manufacturing processes, order of manufacturing processes, etc. shown in the following embodiments are merely examples and are not intended to limit the present invention. In each figure, dimensions and the like are not strictly illustrated.

[0026] In the following description and drawings, the arrangement direction of a pair (positive electrode side and negative electrode side) of electrode terminals in one power storage element, or the opposing direction of the short side surfaces of the container of the power storage element is defined as the X-axis direction. The arrangement direction of a plurality of power storage elements, the opposing direction of the long side surfaces of the container of the power storage element, or the thickness direction of the container is defined as the Y-axis direction. The arrangement direction of the container body and the lid of the container of the power storage element, the arrangement direction of the container of the power storage element and the electrode terminals, the arrangement direction of the power storage element and the bus bar, or the vertical direction is defined as the Z-axis direction. These X-axis direction, Y-axis direction, and Z-axis direction are directions that intersect (orthogonal in the present embodiment) with each other. Although the Z-axis direction may not be the vertical direction depending on the usage mode, hereinafter, for convenience of explanation, the Z-axis direction will be described as the vertical direction.

[0027] In the following description, the positive X-axis direction indicates the arrow direction of the X-axis, and the negative X-axis direction indicates the direction opposite to the positive X-axis direction. The same applies to the Y-axis direction and the Z-axis direction. Expressions indicating relative directions or postures such as parallel and orthogonal strictly include cases where they are not exactly in that direction or posture. That two directions are orthogonal means not only that the two directions are exactly orthogonal, but also that they are substantially orthogonal, that is, including a difference of, for example, about several percent.

[0028] (Embodiment) [1 General Description of Power Storage Device 1] First, a general description of the power storage device 1 in the present embodiment will be given. FIG. 1 is a perspective view showing the appearance of the power storage device 1 according to the present embodiment. FIG. 1 is a view showing the inside of the exterior body 30 with the exterior body 30 being seen through, and the exterior body 30 (and the two external terminals 31) are shown by dashed lines. FIG. 2 is a perspective view showing the appearance of the power storage element 10 according to the present embodiment. FIG. 3 is a plan view showing the joint portion 40 between the bus bar 20 and the electrode terminal 200 of the power storage element 10 according to the present embodiment. Since all of the plurality of power storage elements 10 shown in FIG. 1 have the same configuration, only one power storage element 10 is shown in FIG. 2. Similarly, in FIG. 3, the joint portion 40 between one bus bar 20 and the electrode terminal 200 of one power storage element 10 is shown.

[0029] The power storage device 1 is a device that can charge electricity from the outside and discharge electricity to the outside. In this embodiment, it has a substantially rectangular parallelepiped shape. The power storage device 1 is a battery module (battery pack) used for power storage applications, power supply applications, etc. Specifically, the power storage device 1 is used as a battery for driving a moving body such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for electric railways, or for engine starting. Examples of the above-mentioned automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and gasoline vehicles. Examples of the above-mentioned railway vehicles for electric railways include trains, monorails, and linear motor cars. The power storage device 1 can also be used as a stationary battery for home use, generator use, etc.

[0030] As shown in FIG. 1, the power storage device 1 includes a plurality of power storage elements 10, a plurality of bus bars 20, and an exterior body 30 that houses these power storage elements 10 and bus bars 20. The power storage device 1 may also include a spacer disposed between the power storage elements 10, an end plate and a side plate that restrain the power storage elements 10, a bus bar frame that positions the bus bars 20, a circuit board for monitoring the charge state and discharge state of the power storage elements 10, electrical devices such as fuses, relays, and connectors, and an exhaust portion for exhausting the gas discharged from the power storage elements 10 to the outside of the exterior body 30, etc., but the illustration of these is omitted and the detailed description is also omitted.

[0031] The exterior body 30 is a container (module case) in a substantially rectangular parallelepiped shape (box shape) that constitutes the exterior body of the power storage device 1. That is, the exterior body 30 is disposed outside the power storage element 10 and the bus bar 20, fixes these power storage element 10 and bus bar 20 at predetermined positions, and protects them from impacts and the like. The exterior body 30 is formed of an insulating member such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene·perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), ABS resin, or a composite material thereof, or a metal with insulating coating. The exterior body 30 thereby avoids the power storage element 10 etc. from coming into contact with external metal members etc. The exterior body 30 may be formed of a conductive member such as metal as long as the electrical insulation of the power storage element 10 etc. is maintained.

[0032] Two external terminals 31 are provided on the exterior body 30. These two external terminals 31 are external connection terminals on the positive electrode side and the negative electrode side for charging the power storage device 1 with electricity from the outside and discharging electricity from the power storage device 1 to the outside, and are formed of a conductive member made of metal such as aluminum, aluminum alloy, copper, copper alloy, iron, steel, stainless steel, etc.

[0033] The energy storage element 10 is a secondary battery (single cell) that can charge and discharge electricity, and more specifically, is a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 has a flat rectangular parallelepiped shape (rectangular), and in this embodiment, six energy storage elements 10 are arranged side by side in the Y-axis direction. The size, shape, and number of energy storage elements 10 to be arranged are not limited, and for example, only one energy storage element 10 may be arranged. The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may be a primary battery in which electricity stored without the user having to charge it can be used instead of a secondary battery. The energy storage element 10 may be a battery using a solid electrolyte. The energy storage element 10 may be a pouch-type energy storage element.

[0034] Specifically, as shown in FIG. 2, the energy storage element 10 includes a container 100, a pair (positive electrode side and negative electrode side) of electrode terminals 200, and a pair (positive electrode side and negative electrode side) of gaskets 300. Inside the container 100, an electrode body, a pair (positive electrode side and negative electrode side) of current collectors, an electrolytic solution (non-aqueous electrolyte), etc. are accommodated, but illustration thereof is omitted. The type of the electrolytic solution is not particularly limited as long as it does not impair the performance of the energy storage element 10, and various types can be selected. A spacer may be arranged on the side of the current collector or the like, or an insulating sheet covering the outer surface of the container 100 may be arranged.

[0035] The container 100 is a rectangular parallelepiped-shaped (angular or box-shaped) case, and includes a container body 110 with an opening formed therein, and a lid body 120 that closes the opening of the container body 110. The container body 110 is a rectangular tubular member with a bottom that constitutes the main body of the container 100, has a pair of long side faces on both sides in the Y-axis direction, a pair of short side faces on both sides in the X-axis direction, and a bottom face on the Z-axis minus direction side. The lid body 120 is a flat and rectangular member that constitutes the lid portion of the container 100, and is disposed in the Z-axis plus direction of the container body 110. In the lid body 120, a gas discharge valve 121 that discharges gas to release the pressure when the pressure inside the container 100 rises, and a liquid injection portion 122 for injecting electrolytic solution into the container 100 are disposed. The material of the container 100 is not particularly limited, but for example, it is preferably a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet.

[0036] The electrode terminal 200 is a terminal (positive electrode terminal and negative electrode terminal) of the power storage element 10 disposed on the lid body 120 of the container 100, and is electrically connected to the positive electrode plate and the negative electrode plate of the electrode body via a current collector. That is, the electrode terminal 200 is a metal member for leading out the electricity stored in the electrode body to the external space of the power storage element 10 and introducing electricity into the internal space of the power storage element 10 to store electricity in the electrode body. The electrode terminal 200 is disposed to project upward (Z-axis plus direction) from the lid body 120. The electrode terminal 200 is formed of a metal (conductive) member such as aluminum, aluminum alloy, copper, or copper alloy.

[0037] The gasket 300 is a flat insulating sealing member disposed between the lid body 120 of the container 100 and the electrode terminal 200, electrically insulating and sealing the space between the lid body 120 and the electrode terminal 200. A gasket is also disposed between the lid body 120 and the current collector to electrically insulate and seal the space between the lid body 120 and the current collector, but detailed description thereof is omitted. These gaskets can be formed of any of the insulating members that can be used for the above-described exterior body 30, such as PP and PE.

[0038] The electrode body is a power storage element (power generation element) formed by laminating a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate is formed by forming a positive electrode active material layer on a positive electrode base material layer which is a current collector foil made of a metal such as aluminum or an aluminum alloy. The negative electrode plate is formed by forming a negative electrode active material layer on a negative electrode base material layer which is a current collector foil made of a metal such as copper or a copper alloy. As the active material used in the positive electrode active material layer and the negative electrode active material layer, any known material can be appropriately used as long as it can occlude and release lithium ions. The electrode body may be any form of electrode body, such as a wound type electrode body formed by winding electrode plates (positive electrode plate and negative electrode plate), a laminated type (stack type) electrode body formed by laminating a plurality of flat electrode plates, or a bellows type electrode body formed by folding the electrode plate into a bellows shape.

[0039] The current collector is a conductive member (positive current collector and negative current collector) electrically connected to the electrode terminal 200 and the electrode body. The positive current collector is formed of aluminum or an aluminum alloy or the like, similar to the positive electrode base material layer of the positive electrode plate, and the negative current collector is formed of copper or a copper alloy or the like, similar to the negative electrode base material layer of the negative electrode plate.

[0040] The bus bar 20 is a conductive flat and rectangular member connected to the power storage element 10. Specifically, the bus bar 20 is disposed above a plurality of power storage elements 10 and connected (joined) to the electrode terminals 200 of the plurality of power storage elements 10 to electrically connect the electrode terminals 200 of the plurality of power storage elements 10 to each other. In the present embodiment, the bus bar 20 connects the positive electrode terminals and the negative electrode terminals of adjacent power storage elements 10 in order to connect the plurality of power storage elements 10 in series. Specifically, both ends of the bus bar 20 are joined to the positive electrode terminal and the negative electrode terminal of the adjacent power storage element 10 by welding to electrically connect the positive electrode terminal and the negative electrode terminal of the adjacent power storage element 10.

[0041] In FIG. 1, the connection portion with the external terminal 31 of the bus bar 20 is shown with omission, but the external terminals 31 on the positive electrode side and the negative electrode side are connected to the bus bar 20 arranged at the end. The bus bar 20 arranged at the end is joined to the external terminal 31 by welding, bolt fastening, etc., thereby electrically connecting the power storage element 10 arranged at the end and the external terminal 31. The bus bar 20 is thick, about 1 to 3 mm in thickness, and is formed of a conductive member made of a metal such as aluminum, aluminum alloy, copper, copper alloy, nickel, or a combination thereof, or a conductive member other than metal. The bus bar 20 may be thin with a thickness of less than 1 mm.

[0042] The shape (outer shape, thickness, etc.) and material of the bus bar 20 are not particularly limited. The connection form of the bus bar 20 is also not particularly limited, and a plurality of power storage elements 10 may be arranged so as to be connected in series or in parallel in any combination.

[0043] As shown in FIG. 3, the bus bar 20 is joined to the electrode terminal 200 of the power storage element 10 by welding, and a joint portion 40 is formed. In the present embodiment, two joint portions 40 extending in the Y-axis direction are formed on both sides in the X-axis direction at the overlapping portion of the bus bar 20 and the electrode terminal 200. Hereinafter, the configuration of this joint portion 40 will be described in detail. Since the two joint portions 40 shown in FIG. 3 have the same configuration, hereinafter, one joint portion 40 will be described in detail.

[0044] [Description of the joint portion 40] FIG. 4 is a plan view showing the configuration of the joint portion 40 according to the present embodiment. FIG. 4 shows an enlarged view of the joint portion 40 shown in FIG. 3, and the length of the first weld mark 43 is omitted for brevity. FIG. 5 is a plan view and a cross-sectional view showing the surface melt mark 41, the internal melt mark 42, and the first weld mark 43 of the joint portion 40 according to the present embodiment. Specifically, FIG. 5(a) is a plan view of the state in which the surface melt mark 41, the internal melt mark 42, and the first weld mark 43 are formed in the process of forming the joint portion 40 as viewed from the +Z axis direction. FIG. 5(b) is a cross-sectional view showing the configuration when the state of FIG. 5(a) is cut along a plane parallel to the YZ plane passing through the line Vb-Vb. FIG. 6 is a photograph showing the cross-section of the surface melt mark 41, the internal melt mark 42, and the first weld mark 43 of the joint portion 40 according to the present embodiment. Specifically, FIG. 6 is a photograph corresponding to FIG. 5(b). FIG. 7 is a plan view and a cross-sectional view showing the configuration of the second weld mark 44 of the joint portion 40 according to the present embodiment. Specifically, FIG. 7(a) is a plan view of the state in which the second weld mark 44 is formed in succession to FIG. 5 in the process of forming the joint portion 40 as viewed from the +Z axis direction. FIG. 7(b) is a cross-sectional view showing the configuration when the state of FIG. 7(a) is cut along a plane parallel to the YZ plane passing through the line VIb-VIb. That is, FIGS. 5 to 7 show the joining method of the bus bar 20 and the electrode terminal 200 in the manufacturing method of the power storage device 1.

[0045] The scale in the X-axis direction with respect to the Y-axis direction in FIGS. 5(a) and 7(a) is an example, and the X-axis direction may be enlarged or reduced with respect to the Y-axis direction. Similarly, for the scale in the Z-axis direction with respect to the Y-axis direction in FIGS. 5(b) and 7(b), the Z-axis direction may be enlarged or reduced with respect to the Y-axis direction. The same applies to the subsequent figures.

[0046] As shown in these figures, the joint portion 40 between the bus bar 20 and the electrode terminal 200 of the power storage element 10 has a surface melt mark 41, an internal melt mark 42, a first weld mark 43, and a second weld mark 44. The electrode terminal 200 of the power storage element 10 is an example of a conductive member joined to the bus bar, and the joint portion 40 is an example of a joint portion of the bus bar and the conductive member.

[0047] The surface melting mark 41 is a melting mark formed by melting one surface of the bus bar 20 and the electrode terminal 200 (conductive member). In the present embodiment, the surface melting mark 41 is a melting mark formed by melting the flat (planar) surface 20a of the bus bar 20. Specifically, as shown in FIGS. 5 and 6, a laser beam L1 with a minute output is irradiated onto the surface 20a of the bus bar 20, melting the surface 20a of the bus bar 20 and forming a surface melting mark 41 extending in the Y-axis direction.

[0048] The output of the laser beam L1 is about 0 to 30% of the maximum output of the laser beam L3 described later. The laser beam L1 is irradiated from the end in the minus Y-axis direction to the end in the plus Y-axis direction of the surface melting mark 41, with the output gradually increased from 0% to 30% of the laser beam L3 (or maintained at a constant value between 0 and 30% of the laser beam L3) as it goes in the plus Y-axis direction.

[0049] Thereby, the surface 20a of the bus bar 20 is melted to form a surface melting mark 41 having a depth in the Z-axis direction of about 0.01 to 0.2 mm, a length in the Y-axis direction of about 0.3 to 0.8 mm, and a width in the X-axis direction of about 0.3 to 0.5 mm. These numerical values are examples and are not limited thereto, and can be appropriately changed according to the spot diameter of the laser beam or the like. If the spot diameter of the laser beam is large, the width of the surface melting mark 41 in the X-axis direction becomes large, and if the spot diameter of the laser beam is small, the width of the surface melting mark 41 in the X-axis direction becomes small. The depth in the Z-axis direction and the length in the Y-axis direction of the surface melting mark 41 are also appropriately changed depending on welding conditions and the like.

[0050] In the present embodiment, when viewed from the Z-axis direction, the surface melting mark 41 has a shape in which the edge in the minus Y-axis direction is curved (in the shape of an arc of an ellipse or an oval) and extends in the plus Y-axis direction. The surface melting mark 41 has a shape that extends linearly in the Y-axis direction when viewed from the X-axis direction in terms of the cross-sectional shape.

[0051] The internal melting mark 42 is disposed adjacent to the surface melting mark 41 and is a melting mark that has melted from one surface of the bus bar 20 and the electrode terminal 200 to the inside. In the present embodiment, the internal melting mark 42 is disposed connected to the surface melting mark 41 in the +Y-axis direction of the surface melting mark 41 and is a melting mark that has melted from the surface 20a of the bus bar 20 to the inside. Specifically, as shown in FIGS. 5 and 6, a laser beam L2 having an output larger than that of the laser beam L1 is irradiated onto the surface 20a of the bus bar 20, causing the inside from the surface 20a of the bus bar 20 to melt, and an internal melting mark 42 extending in the Y-axis direction is formed.

[0052] The output of the laser beam L2 is about 30 to 80% of the maximum output of the laser beam L3. The laser beam L2 is irradiated such that the output gradually increases from the end in the +Y-axis direction of the surface melting mark 41 toward the +Y-axis direction to about 30 to 80% of the output of the laser beam L3 (or the output is maintained at a constant value between 30 to 80% of the output of the laser beam L3). The position where the laser beam L2 starts to be irradiated (the end in the +Y-axis direction of the surface melting mark 41 or the end in the -Y-axis direction of the internal melting mark 42) is also referred to as the boundary position 42a between the surface melting mark 41 and the internal melting mark 42. The boundary position 42a is a position where the output is increased so that the output of the laser beam changes from the laser beam L1 to the laser beam L2, the melting width (width in the X-axis direction) of the melting mark starts to increase, and the melting depth (depth in the Z-axis direction) starts to increase (a keyhole starts to be formed). The boundary position 42a between the surface melting mark 41 and the internal melting mark 42 is a position where at least one of the width and the depth of the melting mark changes when reaching from the surface melting mark 41 to the internal melting mark 42. That is, the surface melting mark 41 in the -Y-axis direction from the boundary position 42a is a melted portion where a keyhole is not formed, and the internal melting mark 42 in the +Y-axis direction from the boundary position 42a is a melted portion where a keyhole is formed.

[0053] As a result, the surface 20a to the inside of the bus bar 20 melts, and an internal melting mark 42 is formed with a depth in the Z-axis direction of about 1 to 2 mm, a length in the Y-axis direction of about 4 to 8 mm, and a width in the X-axis direction of about 1 to 3 mm. The internal melting mark 42 has a depth in the Z-axis direction of about 1 / 4 to 3 / 4 of the thickness of the bus bar 20 in the Z-axis direction, and a length in the Y-axis direction of about 2 to 4 times the depth in the Z-axis direction. These numerical values are merely examples and are not limited thereto, and can be appropriately changed according to the thickness of the bus bar 20 and the like. If the thickness of the bus bar 20 is large, the depth of the internal melting mark 42 in the Z-axis direction becomes deeper, and if the thickness of the bus bar 20 is small, the depth of the internal melting mark 42 in the Z-axis direction becomes shallower. The width in the X-axis direction and the length in the Y-axis direction of the internal melting mark 42 are also appropriately changed according to welding conditions and the like.

[0054] In the present embodiment, when the internal melting mark 42 is viewed from the Z-axis direction, the edge (boundary position 42a) in the minus Y-axis direction is curved (in the shape of an arc of an ellipse or an oval), and has a shape extending in the plus Y-axis direction. When the cross-sectional shape of the internal melting mark 42 is viewed from the X-axis direction, the edge in the minus Y-axis direction is curved so as to be concave in the minus Z-axis direction, and has a shape extending in the plus Y-axis direction.

[0055] The first welding mark 43 is disposed adjacent to the internal melting mark 42, and is a welding mark where the bus bar 20 and the electrode terminal 200 (conductive member) are welded. In the present embodiment, the first welding mark 43 is disposed connected to the internal melting mark 42 in the plus Y-axis direction of the internal melting mark 42, penetrates from the surface 20a of the bus bar 20 to the inside, and melts to the inside of the electrode terminal 200. Specifically, as shown in FIGS. 5 and 6, a laser beam L3 having an output larger than that of the laser beam L2 is irradiated onto the surface 20a of the bus bar 20, and the surface 20a of the bus bar 20 to the inside of the electrode terminal 200 melts, and a first welding mark 43 extending in the Y-axis direction is formed.

[0056] The laser beam L3 is irradiated from the end of the internal melting mark 42 in the +Y-axis direction toward the +Y-axis direction, with its output gradually increased from the output of the laser beam L2 (about 30 to 80% of the maximum output of the laser beam L3), and then maintained at the maximum output of the laser beam L3 for irradiation. The position where the laser beam L3 starts to be irradiated (the end of the internal melting mark 42 in the +Y-axis direction or the end of the first welding mark 43 in the -Y-axis direction) is also referred to as the boundary position 43a between the internal melting mark 42 and the first welding mark 43. The boundary position 43a is the position where the output of the laser beam is increased so that the output changes from the laser beam L2 to the laser beam L3, and the melting depth begins to increase.

[0057] As a result, from the surface 20a of the bus bar 20 to the inside of the electrode terminal 200 is melted, and a first welding mark 43 extending in the Y-axis direction with a depth in the Z-axis direction of about 2 to 4 mm and a width in the X-axis direction of about 1 to 3 mm is formed. These numerical values are examples and are not limited to these values, and can be appropriately changed according to the thickness of the bus bar 20 and the electrode terminal 200, etc. If the thickness of the bus bar 20 and the electrode terminal 200 is large, the depth of the first welding mark 43 in the Z-axis direction becomes deeper, and if the thickness of the bus bar 20 and the electrode terminal 200 is small, the depth of the first welding mark 43 in the Z-axis direction becomes shallower. The width of the first welding mark 43 in the X-axis direction is also appropriately changed according to welding conditions and the like.

[0058] In the present embodiment, when viewed from the Z-axis direction, the first welding mark 43 has a curved shape (an arc shape of an ellipse or an oval) at the edge in the -Y-axis direction (boundary position 43a), extends in the +Y-axis direction, and the edge in the +Y-axis direction also has a curved shape (an arc shape of an ellipse or an oval). When viewed from the X-axis direction, the cross-sectional shape of the first welding mark 43 is a curved shape in which the edge in the -Y-axis direction curves so as to be concave in the -Z-axis direction, extends in the +Y-axis direction, and the edge in the +Y-axis direction also has a curved shape that curves so as to be concave in the -Z-axis direction.

[0059] At the end of the first weld mark 43 in the +Y-axis direction, a first molten pool mark 43b is formed. The first molten pool mark 43b is a mark formed by the molten pool during welding and has an oval or elliptical shape when viewed from the Z-axis direction. In Fig. 5(b), the illustration of the first molten pool mark 43b is omitted.

[0060] The second weld mark 44 is a weld mark that extends and is arranged along the first weld mark 43 in the extending direction (Y-axis direction) of the first weld mark 43. In the present embodiment, the second weld mark 44 is connected to and arranged with the first weld mark 43 in the +X-axis direction of the first weld mark 43, penetrates from the surface 20a of the bus bar 20 to the inside, and is a weld mark melted to the inside of the electrode terminal 200. Specifically, as shown in Fig. 7, the laser beam L4 is irradiated onto the surface 20a of the bus bar 20, melting from the surface 20a of the bus bar 20 to the inside of the electrode terminal 200, and forming a second weld mark 44 extending in the Y-axis direction.

[0061] The laser beam L4 has the same output as the laser beam L3 and is irradiated toward the surface 20a of the bus bar 20 while advancing in the -Y-axis direction from a position slightly shifted in the +X-axis direction from the end of the first weld mark 43 in the +Y-axis direction. Thereby, from the surface 20a of the bus bar 20 to the inside of the electrode terminal 200 is melted, and a second weld mark 44 having a depth, width, and length comparable to those of the first weld mark 43 is formed.

[0062] Thus, the second weld mark 44 extends and is arranged along the first weld mark 43 from one end to the other end of the first weld mark 43 in the extending direction (Y-axis direction) of the first weld mark 43. Specifically, the second weld mark 44 extends and is arranged along the first weld mark 43 from a weld mark end 44a, which is an end far from the surface melting mark 41 (the end on the side opposite to the surface melting mark 41 (Y-axis positive direction)), to a position farther from the surface melting mark 41 than the boundary position 42a between the surface melting mark 41 and the internal melting mark 42 (the position on the side of the internal melting mark 42). The weld mark end 44a is an end on the side where welding is started in the second weld mark 44 and is arranged in the Y-axis positive direction rather than the Y-axis positive direction end of the first weld mark 43. That is, the second weld mark 44 extends and is arranged parallel to the first weld mark 43 from a position in the Y-axis positive direction rather than the Y-axis positive direction end of the first weld mark 43 to the Y-axis negative direction end (boundary position 43a) of the first weld mark 43. Thereby, preheating can be performed at the start time of welding in the second weld mark 44. Since the weld mark end 44a is an end on the side where welding is started, no molten pool mark is formed.

[0063] The second weld mark 44 may be formed with a shift in the Y-axis direction with respect to the first weld mark 43, may be formed long in the Y-axis direction, or may be formed short. The Y-axis positive direction end (weld mark end 44a) of the second weld mark 44 may be at the same position as the Y-axis positive direction end of the first weld mark 43 in the Y-axis direction, or may be arranged in the Y-axis negative direction rather than the Y-axis positive direction end of the first weld mark 43. The Y-axis negative direction end of the second weld mark 44 may be arranged in the Y-axis negative direction or the Y-axis positive direction rather than the Y-axis negative direction end of the first weld mark 43.

[0064] The second weld line 44 is formed by overlapping (connecting) with the first weld line 43. That is, the second weld line 44 extends in the Y-axis direction while overlapping (connecting) with the first weld line 43 in the X-axis direction. In this way, at least a part of the first weld line 43 and the second weld line 44 are connected. In the present embodiment, the first weld line 43 and the second weld line 44 are overlapped (connected) from one end to the other end in the Y-axis direction. The overlapping amount of the first weld line 43 and the second weld line 44 is not particularly limited, but in the X-axis direction, it overlaps by about 1 / 4 to 1 / 2 of the width of the first weld line 43 or the second weld line 44 (for example, about 0.5 to 1 mm).

[0065] More specifically, when viewed from the Z-axis direction, the second weld line 44 has a curved edge (oval or elliptical arc shape) in the positive Y-axis direction, extends in the negative Y-axis direction, and the edge in the negative Y-axis direction also has a curved shape (oval or elliptical arc shape). When the cross-sectional shape of the second weld line 44 is viewed from the X-axis direction, the edge in the positive Y-axis direction is curved so as to be concave in the negative Z-axis direction, extends in the negative Y-axis direction, and the edge in the negative Y-axis direction also has a curved shape that is concave in the negative Z-axis direction.

[0066] A second molten pool mark 44b is formed at the end of the second weld line 44 in the negative Y-axis direction. The second molten pool mark 44b is a mark formed by the molten pool during welding and has an oval or elliptical shape when viewed from the Z-axis direction. In FIG. 7(b), the illustration of the second molten pool mark 44b is omitted.

[0067] In this way, by irradiating the bus bar 20 and the electrode terminal 200 with laser light and changing the output of the laser light from the output of the laser light L1 to the output of the laser light L4, a joint portion 40 where the bus bar 20 and the electrode terminal 200 are laser welded is formed. The welding of the bus bar 20 and the electrode terminal 200 is continuous welding rather than pulsed welding. The laser welding can be performed by controlling the output of the laser light using a known device such as an oscillator.

[0068] [Description of Effects] As described above, according to the power storage device 1 according to the embodiment of the present invention, a joint portion 40 is formed on the bus bar 20 and the electrode terminal 200 (conductive member). The joint portion 40 has a surface melting mark 41 in which the surface 20a of one of the bus bar 20 and the electrode terminal 200 (the bus bar 20) is melted, an internal melting mark 42 that is melted from the surface 20a of the one to the inside, and a first welding mark 43 where the bus bar 20 and the electrode terminal 200 are welded. That is, during laser welding, the laser output is reduced to melt the surface 20a of the one to form the surface melting mark 41, and the laser output is slightly increased to form the internal melting mark 42 that is melted from the surface 20a of the one to the inside. The laser output is further increased to weld the bus bar 20 and the electrode terminal 200 to form the first welding mark 43. In this way, by gradually increasing the laser output from the front of the welding target portion to form the surface melting mark 41 and the internal melting mark 42, the welding target portion is preheated, so that the laser output when forming the first welding mark 43 on the welding target portion can be suppressed. In particular, a material to be welded such as aluminum has a low laser absorption rate in a solid state and a high laser absorption rate in a molten state. Therefore, by melting the surface of the material to be welded by preheating, the laser absorption rate can be increased and the laser output can be kept low. If the laser output can be suppressed, the generation of spatter can be suppressed. In particular, when the thickness of the bus bar 20 is large, it is necessary to increase the laser output to penetrate the bus bar 20 and spatter is likely to occur. However, as described above, by suppressing the laser output, the generation of spatter can be suppressed even when using a bus bar 20 with a large thickness. As a result, it is possible to suppress the influence of spatter on the quality of the power storage device 1, and thus suppress the deterioration of the quality of the power storage device 1.

[0069] The joint portion 40 has a second weld mark 44 along the first weld mark 43. The second weld mark 44 has a weld mark end portion 44a where no molten pool mark is formed at a position far from the surface melt mark 41. Thus, when the second weld mark 44 is also formed to increase the joint strength at the joint portion 40, by forming the second weld mark 44 along the first weld mark 43, the heat in the first weld mark 43 can be used for preheating in the second weld mark 44. In particular, since no molten pool mark is formed at the weld mark end portion 44a far from the surface melt mark 41 of the second weld mark 44, it can be determined that the welding of the second weld mark 44 starts from the weld mark end portion 44a. Therefore, by starting the welding from the weld mark end portion 44a at the end of the first weld mark 43, the heat at the end after forming the first weld mark 43 can be used as preheating, and the welding of the second weld mark 44 can be started. Thereby, when forming the second weld mark 44, the laser output can be suppressed, so that the generation of spatter can be suppressed. Therefore, even when forming the second weld mark 44, it is possible to suppress the spatter from affecting the quality of the power storage device 1, and thus it is possible to suppress the deterioration of the quality of the power storage device 1.

[0070] Since the second weld mark 44 extends along the first weld mark 43 from one end to the other end of the first weld mark 43, the bus bar 20 and the electrode terminal 200 (conductive member) can be joined more firmly. Thereby, it is possible to suppress the generation of spatter while improving the joint strength at the joint portion 40, and thus it is possible to suppress the deterioration of the quality of the power storage device 1.

[0071] The joining of the bus bar 20 and the electrode terminal 200 (conductive member) is performed by the first weld mark 43, and the surface melting mark 41 and the internal melting mark 42 are portions that do not contribute to the joining of the bus bar 20 and the electrode terminal 200 (portions that do not require welding). Therefore, the second weld mark 44 also does not need to be formed at positions corresponding to the surface melting mark 41 and the internal melting mark 42, and the formation position of the second weld mark 44 is set from the weld mark end 44a to a position farther from the surface melting mark 41 than the boundary position 42a between the surface melting mark 41 and the internal melting mark 42. This can suppress the occurrence of sputtering due to an increase in the welding temperature caused by forming the second weld mark 44 at an unnecessary position. Therefore, since the influence of sputtering on the quality of the power storage device 1 can be suppressed, a decrease in the quality of the power storage device 1 can be suppressed. If an increase in the welding temperature can be suppressed, deterioration of the components of the power storage device 1 can be suppressed, and thus a decrease in the quality of the power storage device 1 can be suppressed.

[0072] By changing at least one of the width and depth of the melting mark in the surface melting mark 41, it is possible to transition from the surface melting mark 41 to the internal melting mark 42.

[0073] By forming the first weld mark 43 and the second weld mark 44 such that at least a part of them is connected (overlapped), the heat in the first weld mark 43 can be effectively utilized as preheating to form the second weld mark 44. Thereby, when forming the second weld mark 44, the laser output can be suppressed, and thus the occurrence of sputtering can be suppressed. Therefore, when forming the second weld mark 44, since the influence of sputtering on the quality of the power storage device 1 can be suppressed, a decrease in the quality of the power storage device 1 can be suppressed. By forming the first weld mark 43 and the second weld mark 44 to overlap each other, the joining strength of the bus bar 20 and the electrode terminal 200 can be improved, and space saving can also be achieved.

[0074] In the manufacturing method of the power storage device 1 (the joining method of the bus bar 20 and the electrode terminal 200), the same effects as those of the above-described power storage device 1 are obtained.

[0075] [Description of Modification Example 4] (Modification Example 1) Next, a modification example 1 of the above embodiment will be described. FIG. 8 is a plan view showing the configuration of the joint portion 40a according to the modification example 1 of the present embodiment. FIG. 8 is a figure corresponding to FIG. 4.

[0076] As shown in FIG. 8, the joint portion 40a in this modification example is different from the joint portion 40 in the above embodiment in that the surface melting mark 41, the internal melting mark 42, the first welding mark 43, and the second welding mark 44 are separated. That is, in this modification example, the second welding mark 44 extends and is arranged along the first welding mark 43 in the extending direction (Y-axis direction) of the first welding mark 43, but the first welding mark 43 and the second welding mark 44 are not connected and are arranged in the vicinity. Since other configurations of this modification example are the same as those of the above embodiment, detailed description thereof will be omitted.

[0077] As described above, according to the power storage device according to this modification example, the same effects as those of the above embodiment can be achieved. In particular, in this modification example, although the second welding mark 44 is separated from the first welding mark 43, since it is arranged in the vicinity of the first welding mark 43, the heat at the first welding mark 43 can be utilized as preheating. Thereby, also in this modification example, the generation of spatter can be suppressed, so that the influence of spatter on the quality of the power storage device can be suppressed, and the deterioration of the quality of the power storage device can be suppressed.

[0078] In this modification example, a part of the second welding mark 44 in the Y-axis direction may be connected (overlapped) with the first welding mark 43. The end portion of the second welding mark 44 in the positive Y-axis direction may be connected to the first welding mark 43, or the central portion in the Y-axis direction or the end portion in the negative Y-axis direction may be connected to the first welding mark 43.

[0079] (Modification Example 2) Next, a modification example 2 of the above embodiment will be described. FIG. 9 is a plan view showing the configuration of the joint portion 40b according to the modification example 2 of the present embodiment. FIG. 9 is a figure corresponding to FIG. 4.

[0080] As shown in FIG. 9, the joint portion 40b in this modified example has a surface melting mark 45a, an internal melting mark 45b, and a third welding mark 45c instead of the second welding mark 44 of the joint portion 40 in the above embodiment. Since other configurations of this modified example are the same as those of the above embodiment, detailed description thereof will be omitted.

[0081] The surface melting mark 45a, the internal melting mark 45b, and the third welding mark 45c have the same configuration as the surface melting mark 41, the internal melting mark 42, and the first welding mark 43, and are arranged at positions shifted in the positive X-axis direction from these. That is, the surface melting mark 45a is a melting mark formed by melting the surface 20a of the bus bar 20, and the internal melting mark 45b is arranged adjacent to the surface melting mark 45a and is a melting mark melted from the surface 20a of the bus bar 20 to the inside. The third welding mark 45c is arranged adjacent to the internal melting mark 45b and is a welding mark where the bus bar 20 and the electrode terminal 200 are welded. A third melting pool mark 45d is formed at the end in the positive Y-axis direction of the third welding mark 45c. The third welding mark 45c extends along the first welding mark 43 from one end to the other end of the first welding mark 43 in the extending direction (Y-axis direction) of the first welding mark 43 and is arranged. At least a part of the first welding mark 43 and the third welding mark 45c are connected.

[0082] As described above, according to the power storage device according to this modified example, the same effects as those of the above embodiment can be achieved. In particular, in this modified example, also in the third welding mark 45c, since the welding target portion is preheated by forming the surface melting mark 45a and the internal melting mark 45b, the laser output when forming the third welding mark 45c in the welding target portion can be suppressed. Thereby, also in this modified example, generation of spatter can be suppressed, so that it is possible to suppress the influence of spatter on the quality of the power storage device and suppress a decrease in the quality of the power storage device.

[0083] (Modified Example 3) Next, a modification example 3 of the above embodiment will be described. FIGS. 10A and 10B are plan views showing the configurations of the joints 40c and 40d according to the modification example 3 of the present embodiment. FIGS. 10A and 10B correspond to the bus bar 20 and the electrode terminal 200 in FIG. 3.

[0084] As shown in FIG. 10A, the joint 40c in this modification example has surface melting marks 46a, internal melting marks 46b, first welding marks 46c, and second welding marks 46d instead of the surface melting mark 41, internal melting mark 42, first welding mark 43, and second welding mark 44 of the joint 40 in the above embodiment. Since the other configurations of this modification example are the same as those of the above embodiment, detailed description thereof will be omitted.

[0085] The surface melting marks 46a, internal melting marks 46b, first welding marks 46c, and second welding marks 46d have the same configurations as the surface melting mark 41, internal melting mark 42, first welding mark 43, and second welding mark 44 in the above embodiment. However, different from the above embodiment, they have a curved shape. Specifically, a circular opening 21 is formed in the bus bar 20, and the surface melting marks 46a, internal melting marks 46b, first welding marks 46c, and second welding marks 46d are formed to extend in a curved shape in the Y-axis direction so as to surround the periphery of the opening 21. The opening 21 is a circular through-hole in which a circular convex portion formed on the electrode terminal 200 is disposed.

[0086] Similar to the above embodiment, the second welding mark 46d is extended and disposed along the first welding mark 46c in the extending direction (Y-axis direction) of the first welding mark 46c, and is formed by overlapping the first welding mark 46c. That is, after the first welding mark 46c is formed on the outer side of the periphery of the opening 21, the second welding mark 46d is formed inside the first welding mark 46c.

[0087] As shown in FIG. 10B, the joint portion 40d in this modified example has surface melting marks 47a, internal melting marks 47b, first welding marks 47c, and second welding marks 47d instead of the surface melting marks 41, internal melting marks 42, first welding marks 43, and second welding marks 44 of the joint portion 40 in the above embodiment. Since other configurations of this modified example are the same as those of the above embodiment, detailed description thereof will be omitted.

[0088] The surface melting mark 47a, the internal melting mark 47b, the first welding mark 47c, and the second welding mark 47d have the same configurations as the respective components in the joint portion 40c shown in FIG. 10A. However, different from the joint portion 40c, after the first welding mark 47c is formed, the second welding mark 47d is formed outside the first welding mark 47c.

[0089] As described above, according to the power storage device according to this modified example, the same effects as those of the above embodiment can be achieved. In particular, in the joint portion 40c of this modified example, since the second welding mark 46d is formed inside the first welding mark 46c after the first welding mark 46c is formed, the heat generated when forming the first welding mark 46c can be retained inside the first welding mark 46c. Thereby, the heat generated when forming the first welding mark 46c can be used as preheating when forming the second welding mark 46d. Even in the case where a heat sink is arranged around the first welding mark 46c to dissipate the heat generated when forming the first welding mark 46c, since heat is not dissipated from the inside of the first welding mark 46c, the heat can be used as preheating when forming the second welding mark 46d. Therefore, the generation of spatter can be suppressed, so that the influence of spatter on the quality of the power storage device can be suppressed, and the deterioration of the quality of the power storage device can be suppressed.

[0090] In the joint portion 40d of this modified example, after the first welding mark 47c is formed, the second welding mark 47d is formed outside the first welding mark 47c. Therefore, after forming the inner first welding mark 47c to suppress the warping of the bus bar 20, the outer second welding mark 47d can be formed. Thereby, the joining quality in the joint portion 40d can be improved, so that the deterioration of the quality of the power storage device can be suppressed.

[0091] In this modification example, the opening 21 does not have to be formed in the bus bar 20. In the above-described embodiment and modification examples 1 and 2, the opening 21 may be formed in the bus bar 20.

[0092] (Other modification examples) As described above, the power storage device according to the present embodiment and its modification examples has been described. However, the present invention is not limited to the above-described embodiment and its modification examples. That is, the disclosed embodiment and its modification examples are illustrative in all respects and not restrictive. The scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

[0093] In the above-described embodiment and its modification examples, two joint portions extending linearly or curvedly in the Y-axis direction are formed on both sides in the X-axis direction at the overlapping portion of the bus bar 20 and the electrode terminal 200. However, the joint portions may be formed on both sides in the Y-axis direction at the overlapping portion, or may be formed at other positions. The number of joint portions is not particularly limited, and may be one or three or more. The extending direction of the joint portions is not particularly limited, and may be in the X-axis direction, or may extend in a direction inclined from the X-axis direction or the Y-axis direction.

[0094] In the above-described embodiment and its modification examples, at the joint portion of the bus bar 20 and the electrode terminal 200, the surface melting mark is arranged at the end in the minus Y-axis direction (welding starts from the end in the minus Y-axis direction). However, at the joint portion, the surface melting mark may be arranged at the end in the plus Y-axis direction (welding starts from the end in the plus Y-axis direction), or may be arranged at other positions depending on the formation position and shape (length, extending direction, etc.) of the joint portion.

[0095] In the above-described embodiments and their modifications, at the joint between the bus bar 20 and the electrode terminal 200, it was assumed that the second weld mark extends (parallel to the first weld mark) in the extending direction of the first weld mark. However, the second weld mark may extend in a direction inclined with respect to the extending direction of the first weld mark, or in a direction intersecting the extending direction of the first weld mark, such as a direction orthogonal to the extending direction of the first weld mark. Even in this case, since the heat generated by the formation of the first weld mark can be used as preheating at the start of welding of the second weld mark, the laser output can be suppressed and the generation of spatter can be suppressed.

[0096] In the above-described embodiments and Modifications 1 and 3, the second weld mark may be formed in the same direction as the direction in which the first weld mark is formed. In the above-described embodiment, since the first weld mark 43 is formed in the +Y-axis direction, the second weld mark 44 may also be formed in the +Y-axis direction, and a second molten pool mark 44b may be formed at the +Y-axis end of the second weld mark 44. By utilizing the heat generated when forming the first weld mark 43, the second weld mark 44 can also be formed in this direction. The same applies to Modification 1 and the like.

[0097] In the above-described embodiments and their modifications, all the joints between the bus bar 20 and the electrode terminal 200 have the above-described configuration. However, even if any one of the joints does not have the above-described configuration, it may be acceptable.

[0098] In the above-described embodiments and their modifications, as an example of the "joint portion between the bus bar and the conductive member", the joint portion between the bus bar 20 and the electrode terminal 200 was exemplified, but it is not limited thereto. As an example of the "joint portion between the bus bar and the conductive member", a joint portion between bus bars, or a joint portion between a bus bar and a voltage detection terminal, etc. can also be exemplified. That is, no matter what kind of conductive member is joined to the bus bar, it can be an example of the "joint portion between the bus bar and the conductive member". In this case, instead of irradiating the laser light from the bus bar side, the laser light may be irradiated from the conductive member side to form surface melting marks and internal melting marks on the conductive member. Even when the conductive member is the electrode terminal 200, depending on the shape, the laser light can be irradiated from the electrode terminal 200 side to form surface melting marks and internal melting marks on the electrode terminal 200.

[0099] A form constructed by arbitrarily combining the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0100] The present invention can be realized not only as such a power storage device, but also as a joining structure or joining method of a bus bar and a conductive member (bus bar 20 and electrode terminal 200), or as a manufacturing method of a power storage device including the joining method.

Industrial Applicability

[0101] The present invention can be applied to a power storage device including a power storage element such as a lithium ion secondary battery.

Explanation of Reference Numerals

[0102] 1 Power storage device 10 Power storage element 20 Bus bar 20a Surface 21 Opening 30 Exterior body 31 External terminal 40, 40a, 40b, 40c, 40d Joint portion 41, 45a, 46a, 47a Surface melting mark 42, 45b, 46b, 47b Internal melting mark Boundary positions of 42a and 43a First weld seams of 43, 46c, and 47c First molten pool mark of 43b Second weld seams of 44, 46d, and 47d Weld seam end of 44a Second molten pool mark of 44b Third weld seam of 45c Third molten pool mark of 45d Container 100 Container body 110 Cover 120 Gas discharge valve 121 Liquid injection part 122 Electrode terminal 200 Gasket 300

Claims

1. A power storage device including a power storage element and a bus bar, comprising a conductive member joined to the bus bar, The joint of the bus bar and the conductive member has a surface melting mark where one surface of the bus bar and the conductive member is melted, an internal melting mark disposed adjacent to the surface melting mark and melted from the one surface to the inside, and a first welding mark disposed adjacent to the internal melting mark and where the bus bar and the conductive member are welded. A power storage device.

2. The joint further has a second welding mark extending along the first welding mark and disposed in the extending direction of the first welding mark, The second welding mark has a welding mark end portion that is a far end from the surface melting mark and where a melting pool mark is not formed. The power storage device according to claim 1.

3. The second welding mark extends along the first welding mark and is disposed over the entire length from one end to the other end of the first welding mark in the extending direction. The power storage device according to claim 2.

4. The second welding mark extends along the first welding mark and is disposed from the welding mark end portion to a position farther from the surface melting mark than the boundary position between the surface melting mark and the internal melting mark. The power storage device according to claim 2 or 3.

5. The boundary position between the surface melting mark and the internal melting mark is a position where at least one of the width and depth of the melting mark changes when reaching the internal melting mark from the surface melting mark. The power storage device according to claim 4.

6. At least a part of the first welding mark and the second welding mark are connected. The power storage device according to any one of claims 2 to 5.

7. A method for manufacturing an energy storage device including an energy storage element and a bus bar, including a joining step of joining the bus bar and a conductive member, in the joining step, forming a surface melting mark where one surface of the bus bar and the conductive member is melted, forming an internal melting mark that is disposed adjacent to the surface melting mark and is melted from the one surface to the inside, and forming a first welding mark where the bus bar and the conductive member are welded, which is disposed adjacent to the internal melting mark A method for manufacturing an energy storage device.

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