Electricity storage device and method for manufacturing the same

Abstract

An embodiment comprises an electricity storage element having a metal external terminal, and a metal busbar layered on the external terminal and welded to the external terminal, and is characterized in that: the busbar is formed with a weld portion welding the busbar with the external terminal; the weld portion extends from the busbar to the external terminal; the external terminal comprises a cladding material including a first metal layer adjacent to the busbar and a second metal layer adjacent to the first metal layer; the weld portion welds the busbar and the first metal layer; and an end of the weld portion does not reach the interface between the first metal layer and the second metal layer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2020-082644, the contents of which are incorporated herein by reference. [Technical Field]

[0002] The present invention relates to an energy storage device including an energy storage element having an external terminal and a bus bar, and to a method for manufacturing the energy storage device. [Background technology]

[0003] Conventionally, a battery pack including a plurality of prismatic secondary batteries each having an external terminal has been known (see, for example, Patent Document 1). This battery pack includes a negative electrode terminal, a positive electrode terminal, external terminals (negative electrode external terminal and positive electrode external terminal), and bus bars connecting the negative electrode external terminals and the positive electrode external terminals. In this battery pack, the external terminals and the bus bars are connected by laser welding. In this battery pack, the negative electrode terminal is made of copper, and the bus bars are made of aluminum. The negative electrode external terminal has a clad region made of a copper portion and an aluminum portion.

[0004] However, if an attempt is made to ensure a sufficient welding width when laser welding the external terminal and the bus bar to ensure the connection strength between them, the penetration depth between the external terminal and the bus bar will be deep. On the other hand, if the welding penetration reaches the interface between different metal layers of the external terminal when welding the external terminal having a clad region to the bus bar, the joint strength at this interface (the joint strength between adjacent metal layers) will decrease. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 065523 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present embodiment aims to provide an energy storage device having an energy storage element whose external terminals are made of clad material and to which a bus bar is connected, in which a decrease in the bonding strength between the metal layers that make up the clad material is suppressed, and a method for manufacturing the same. [Means for solving the problem]

[0007] The power storage device of this embodiment is an energy storage element having a metal external terminal; a metal bus bar laminated on the external terminal and welded to the external terminal, a welded portion for welding the bus bar to the external terminal is formed on the bus bar; the welded portion extends from the bus bar to the external terminal, the external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer together, The end of the weld does not reach the interface between the first metal layer and the second metal layer.

[0008] In the power storage device, The weld may include a first weld and a second weld that overlap one another.

[0009] In addition, in the power storage device, In a cross section of the external terminal and the bus bar in the stacking direction of the external terminal and the bus bar, the dimension of the weld in a direction perpendicular to the stacking direction at the boundary position between the external terminal and the bus bar may be larger than the thickness of the first metal layer.

[0010] In the power storage device, The welded portion may have a corner-free circular or arc shape when viewed from the stacking direction of the external terminal and the bus bar.

[0011] In addition, the power storage device of this embodiment has an energy storage element having a metal external terminal; a bus bar made of a metal including aluminum that is laminated on the external terminal and welded to the external terminal; a welded portion for welding the bus bar to the external terminal is formed on the bus bar; the welded portion extends from the bus bar to the external terminal, the external terminals include a positive external terminal and a negative external terminal, the positive electrode external terminal is made of a metal containing aluminum, the negative electrode external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the first metal layer is formed of a metal including aluminum; the second metal layer is formed of a metal including copper, the welded portion welds the bus bar and the first metal layer together, The end of the weld does not reach the interface between the first metal layer and the second metal layer.

[0012] The method for manufacturing the electricity storage device of this embodiment includes the steps of: the method includes stacking a metal bus bar on a metal external terminal of an energy storage element, and applying heat to the bus bar from the side opposite to the external terminal to weld the bus bar to the external terminal, thereby forming a weld in the bus bar that welds the bus bar to the external terminal; the welded portion extends from the bus bar to the external terminal, the external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer together, The end of the weld does not reach the interface between the first metal layer and the second metal layer.

[0013] In the method for manufacturing the electricity storage device, The welded portion may be formed in a cornerless ring shape or a cornerless arc shape when viewed from the stacking direction of the external terminal and the bus bar. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of the electricity storage device according to this embodiment. [Figure 2] FIG. 2 is a perspective view of an energy storage element in the energy storage device. [Figure 3] FIG. 3 is a side view of the energy storage element. [Figure 4] FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along the line VV in FIG. [Figure 6A] FIG. 6A is a schematic plan view illustrating the connection between the external terminals of the energy storage elements and the bus bars. [Figure 6B] FIG. 6B is a schematic cross-sectional view taken along the line VI-VI in FIG. 6A. [Figure 7A] FIG. 7A is a schematic plan view illustrating connections between external terminals and bus bars of an energy storage element according to a comparative example. [Figure 7B] FIG. 7B is a schematic cross-sectional view taken along the line VII-VII in FIG. 7A. DETAILED DESCRIPTION OF THE INVENTION

[0015] The power storage device of this embodiment is an energy storage element having a metal external terminal; a metal bus bar laminated on the external terminal and welded to the external terminal, a welded portion for welding the bus bar to the external terminal is formed on the bus bar; the welded portion extends from the bus bar to the external terminal, the external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer together, The end of the weld does not reach the interface between the first metal layer and the second metal layer.

[0016] With this configuration, the weld does not reach the interface between the metal layers that make up the clad material, so the bonding strength of each metal layer that makes up the clad material can be ensured.

[0017] In the power storage device, The weld may include a first weld and a second weld that overlap one another.

[0018] According to this configuration, the joining width of the welded portion is ensured to be wide, thereby ensuring the joining strength between the bus bar and the external terminal.

[0019] In addition, in the power storage device, In a cross section of the external terminal and the bus bar in the stacking direction of the external terminal and the bus bar, the dimension in a direction perpendicular to the stacking direction at the boundary position between the external terminal and the bus bar may be larger than the thickness of the first metal layer.

[0020] With this configuration, the dimensions of the weld (the dimensions in the direction perpendicular to the stacking direction) at the boundary between the external terminal and the bus bar are ensured, thereby ensuring the bonding strength between the bus bar and the external terminal, and thereby ensuring the bonding strength between the metal layers of the clad material while also ensuring the bonding strength between the bus bar and the external terminal.

[0021] In the power storage device, The welded portion may have a corner-free circular or arc shape when viewed from the stacking direction of the external terminal and the bus bar.

[0022] According to this configuration, since the welded portion is circular or arc-shaped without any corners, even if a force is applied to the welded portion, the force is unlikely to be concentrated in one part of the welded portion.

[0023] In addition, the power storage device of this embodiment has an energy storage element having a metal external terminal; a bus bar made of a metal including aluminum that is laminated on the external terminal and welded to the external terminal; a welded portion for welding the bus bar to the external terminal is formed on the bus bar; the welded portion extends from the bus bar to the external terminal, the external terminals include a positive external terminal and a negative external terminal, the positive electrode external terminal is made of a metal containing aluminum, the negative electrode external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the first metal layer is formed of a metal including aluminum; the second metal layer is formed of a metal including copper, the welded portion welds the bus bar and the first metal layer together, The end of the weld does not reach the interface between the first metal layer and the second metal layer.

[0024] With this configuration, the weld does not reach the interface between the metal layers that make up the clad material, so the bonding strength of each metal layer that makes up the clad material can be ensured.

[0025] The method for manufacturing the electricity storage device of this embodiment includes the steps of: the method includes stacking a metal bus bar on a metal external terminal of an energy storage element, and applying heat to the bus bar from the side opposite to the external terminal to weld the bus bar to the external terminal, thereby forming a weld in the bus bar that welds the bus bar to the external terminal; the welded portion extends from the bus bar to the external terminal, the external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer together, The end of the weld does not reach the interface between the first metal layer and the second metal layer.

[0026] With this configuration, since the welded portion does not reach the interface between the metal layers that make up the clad material, it is possible to manufacture an energy storage device that ensures the bonding strength of each metal layer that makes up the clad material.

[0027] In the method for manufacturing the electricity storage device, The welded portion may be formed in a cornerless ring shape or a cornerless arc shape when viewed from the stacking direction of the external terminal and the bus bar.

[0028] With this configuration, when welding with a typical welding width, it is possible to form a circular or arc-shaped weld without corners, which makes it difficult for force to be concentrated in one area.

[0029] As described above, according to the energy storage device of this embodiment, it is possible to provide an energy storage device and a manufacturing method thereof, which are provided with energy storage elements whose external terminals are made of clad material and to which bus bars are connected, and which suppress a decrease in the bonding strength between the metal layers that make up the clad material.

[0030] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 to 7B. In this embodiment, a chargeable and dischargeable secondary battery will be described as an example of an energy storage element. Note that the names of the components (elementary components) in this embodiment are those used in this embodiment and may differ from the names of the components (elementary components) in the background art.

[0031] As shown in Fig. 1, the energy storage device 11 includes an energy storage element 1 having a metal external terminal 4, and a metal bus bar 6 stacked on and welded to the external terminal 4. As shown in Fig. 6B, the bus bar 6 of the energy storage device 11 has a welded portion 7 formed at a joining position between the external terminal 4 and the bus bar 6, welding the external terminal 4 and the bus bar 6 together. The energy storage device 11 of this embodiment includes a plurality of energy storage elements 1 (see Fig. 1).

[0032] The plurality of energy storage elements 1 are arranged in a predetermined direction (first direction). The first direction is, for example, a direction perpendicular to the stacking direction of the external terminals 4 and the bus bars 6. Each of the plurality of energy storage elements 1 is a primary battery, a secondary battery, a capacitor, or the like. The energy storage element 1 of this embodiment is a chargeable and dischargeable non-aqueous electrolyte secondary battery. More specifically, the energy storage element 1 is a lithium ion secondary battery that utilizes electron transfer that occurs with the movement of lithium ions. The energy storage element 1 is a so-called prismatic lithium ion secondary battery.

[0033] 2 to 5, the energy storage element 1 includes an electrode assembly 2 including a positive electrode and a negative electrode, a case 3 that houses the electrode assembly 2, and an external terminal 4 that is disposed on the outside of the case 3 and is electrically connected to the electrode assembly 2. In addition to the electrode assembly 2, the case 3, and the external terminal 4, the energy storage element 1 also includes a current collector 5 that electrically connects the electrode assembly 2 and the external terminal 4, etc.

[0034] The electrode assembly 2 includes a winding core 21 and a laminate 22 in which a positive electrode and a negative electrode are laminated and insulated from each other, and the laminate 22 is wound around the winding core 21 (see FIG. 5). Lithium ions move between the positive electrode and the negative electrode in the electrode assembly 2, thereby charging and discharging the energy storage element 1.

[0035] The positive electrode includes, for example, a strip-shaped metal foil and a positive electrode active material layer formed on the metal foil, and the negative electrode includes, for example, a strip-shaped metal foil and a negative electrode active material layer formed on the metal foil.

[0036] In the electrode assembly 2 of this embodiment, the positive electrode and the negative electrode are wound while being insulated by a separator. That is, in the electrode assembly 2 of this embodiment, a laminate of the positive electrode, the negative electrode, and the separator is wound. The separator is an insulating member. The separator is disposed between the positive electrode and the negative electrode. This insulates the positive electrode and the negative electrode from each other in the electrode assembly 2 (more specifically, the laminate). The separator also holds the electrolyte solution in the case 3. This allows lithium ions to move between the positive electrodes and the negative electrodes that are alternately stacked with the separator sandwiched between them during charging and discharging of the energy storage device 1.

[0037] The case 3 has a case body 31 with an opening and a cover plate 32 that closes (blocks) the opening of the case body 31. The case 3 accommodates an electrolyte in an internal space 33 together with the electrode assembly 2, the current collector 5, etc. The case 3 is formed of a metal that is resistant to the electrolyte. The case 3 of this embodiment is formed of a metal material that contains aluminum, such as aluminum or an aluminum alloy. The case 3 may also be formed of a metal material such as stainless steel or nickel, or a composite material in which a resin such as nylon is bonded to aluminum.

[0038] The electrolyte is a non-aqueous electrolyte. The electrolyte is obtained by dissolving an electrolyte salt in an organic solvent. The organic solvent is, for example, a cyclic carbonate ester such as propylene carbonate or ethylene carbonate, or a chain carbonate such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate. The electrolyte salt is, for example, LiClO4, LiBF4, or LiPF6.

[0039] The case 3 is formed by overlapping and joining the peripheral edge of the opening of the case body 31 and the peripheral edge of the cover plate 32 (see FIG. 4). The case 3 has an internal space 33 defined by the case body 31 and the cover plate 32. In this embodiment, the peripheral edge of the opening of the case body 31 and the peripheral edge of the cover plate 32 are joined by welding.

[0040] The case body 31 comprises a plate-shaped closing portion 311 having an inner surface facing the inside of the case 3 and an outer surface facing the outside of the case 3, and a body portion 312 connected to the periphery of the closing portion 311, which is a cylindrical body portion 312 that extends toward the inner surface of the closing portion 311 and surrounds the inner surface (see Figure 2).

[0041] The closing portion 311 is located at the bottom end of the case body 31 when the case body 31 is placed with the opening facing upward (i.e., it forms the bottom wall of the case body 31 when the opening faces upward). The closing portion 311 is rectangular when viewed in the normal direction of the closing portion 311. The four corners of the closing portion 311 are arc-shaped.

[0042] In the following description, as shown in FIG. 2, the long side direction of the blocking portion 311 is defined as the X-axis direction, the short side direction of the blocking portion 311 is defined as the Y-axis direction, and the normal direction of the blocking portion 311 is defined as the Z-axis direction.

[0043] The cover plate 32 is a plate-shaped member that closes the opening of the case body 31. Specifically, the cover plate 32 abuts against the case body 31 so as to close the opening of the case body 31. More specifically, the peripheral edge of the cover plate 32 is overlapped with the peripheral edge of the opening of the case body 31 so that the cover plate 32 closes the opening. The boundary between the overlapping cover plate 32 and the case body 31 is welded. In this way, the case 3 is constructed.

[0044] The cover plate 32 has a gas exhaust valve 321 (see FIG. 3) that can exhaust gas inside the case 3 to the outside. The gas exhaust valve 321 exhausts gas from inside the case 3 to the outside when the internal pressure of the case 3 rises to a predetermined pressure.

[0045] The external terminal 4 is a portion electrically connected to an external terminal of another energy storage element or an external device, etc. The external terminal 4 of this embodiment has an outer surface 40 to which a bus bar, etc. can be welded. The outer surface 40 of this embodiment is flat. The external terminal 4 is in the form of a plate extending along the cover plate 32. Specifically, the flange portion of the external terminal 4 is in the form of a rectangular plate when viewed in the Z-axis direction.

[0046] The external terminals 4 also have a flange that extends along the outside of the case 3, and an axial portion that extends from the flange to penetrate the case 3 and is electrically connected to the electrode body 2 (see FIG. 4). The external terminals 4 also include an external terminal (positive electrode external terminal) 4a that is connected to the positive electrode, and an external terminal (negative electrode external terminal) 4b that is connected to the negative electrode.

[0047] In the external terminal 4a, the flange portion 401a and the shaft portion 402a are integral with each other. The external terminal 4a is made of a metal material containing aluminum, such as aluminum or an aluminum alloy.

[0048] In the external terminal 4b, the flange portion 401b and the shaft portion 402b are separate bodies (separate members) and are connected to each other by crimping the shaft portion 402b.

[0049] The external terminal 4b has a clad material including multiple (two in this embodiment) metal layers stacked in the stacking direction (Z-axis direction) of the bus bar 6 and the external terminal 4. More specifically, in the external terminal 4b, the flange portion 401b is made of a clad material. Adjacent metal layers among these multiple metal layers are made of different types of metal.

[0050] For example, as shown in FIG. 6B , the multiple metal layers included in flange portion 401b (external terminal 4b) include a first metal layer 41 located closest to bus bar 6 in the Z-axis direction (i.e., adjacent to bus bar 6) and a second metal layer 42 adjacent to first metal layer 41. In this embodiment, flange portion 401b is composed of first metal layer 41 and second metal layer 42. In this embodiment, the thickness of first metal layer 41 is, for example, 0.2 to 1.0 mm, and the thickness of second metal layer 42 is, for example, 0.2 to 3.0 mm. The thicknesses of first metal layer 41 and second metal layer 42 are not limited to these ranges.

[0051] The first metal layer 41 is formed of, for example, a metal material containing aluminum, such as aluminum or an aluminum alloy, etc. The second metal layer 42 is formed of, for example, a metal material containing copper, such as copper or a copper alloy, etc.

[0052] The current collector 5 is disposed in the case 3 and is directly or indirectly connected to the electrode assembly 2 so as to be electrically conductive (see FIGS. 4 and 5). The current collector 5 is made of a conductive material.

[0053] The busbar 6 electrically connects different energy storage elements 1 to each other or connects the energy storage elements 1 to external input / output terminals, etc. (see FIG. 1). The busbar 6 of this embodiment is placed on the outer surface 40 of the external terminal 4 and welded to the external terminal 4 (see FIG. 6B). The busbar 6 of this embodiment is made of the same material as the external terminal 4a. Furthermore, the busbar 6 of this embodiment is made of the same material as the first metal layer 41 of the external terminal 4b. Specifically, the busbar 6 is made of a metal material containing aluminum, such as aluminum or an aluminum alloy.

[0054] The welded portion 7 is a portion formed by welding the external terminal 4b (specifically, the flange portion 401b) and the bus bar 6 (see FIGS. 6A and 6B). The welded portion 7 extends from the bus bar 6 to the external terminal 4b, i.e., is formed between the bus bar 6 and the external terminal 4b. In other words, the welded portion 7 is formed continuously from the bus bar 6 to the external terminal 4b. The welded portion 7 of this embodiment is formed by laser welding the external terminal 4b and the bus bar 6. The welded portion 7 of this embodiment also includes welding trajectories 710 and 720, which are marks of the laser irradiation position (specifically, marks caused by the center of the laser irradiation position). The width of the laser irradiated toward the bus bar 6 during laser welding of this embodiment is 1.0 mm or less.

[0055] The manufacturing method of this energy storage device 11 includes a step of forming a welded portion 7 when welding the external terminal 4b and the bus bar 6. Specifically, the manufacturing method of the energy storage device 11 includes stacking a metal bus bar 6 on the metal external terminal 4b of the energy storage element 1, and applying heat to the bus bar 6 from the side opposite to the external terminal 4b to weld the bus bar 6 to the external terminal 4b, thereby forming a welded portion 7 in the bus bar 6 that welds the bus bar 6 to the external terminal 4b at the welding position between the external terminal 4b and the bus bar 6, i.e., forming the welded portion 7 between the external terminal 4b and the bus bar 6. In other words, the welded portion 7 is formed continuously from the bus bar 6 to the external terminal 4b.

[0056] In the Z-axis direction, the end 70 of the welded portion 7 does not reach the interface 43 between the first metal layer 41 and the second metal layer 42. Specifically, the end 70 of the welded portion 7 is located within the first metal layer 41. More specifically, the end 70 of the welded portion 7 is located closer to the busbar 6 than the interface 43 between the first metal layer 41 and the second metal layer 42 (see FIG. 6B ). That is, in the Z-axis direction, this end 70 is located just before the interface 43 between the first metal layer 41 and the second metal layer 42.

[0057] The end 70 of the welded portion 7 is the end on the external terminal 4b side of both ends of the welded portion 7 in the Z-axis direction. That is, when the case body 31 is arranged so that the opening faces upward (that is, when the busbar 6 is arranged above the external terminal 4b), the end 70 of the welded portion 7 becomes the lower end of the welded portion 7.

[0058] The welded portion 7 of this embodiment includes a first welded portion 71 and a second welded portion 72 that partially overlap each other. Specifically, the first welded portion 71 and the second welded portion 72 overlap each other at least at the boundary position (on the outer surface 40 of the external terminal 4b) between the external terminal 4b and the busbar 6. The first welded portion 71 includes a first welding locus 710, and the second welded portion 72 includes a second welding locus 720 (see FIG. 6A).

[0059] The dimension (width W1) of the welded portion 7 at the boundary position between the external terminal 4b and the bus bar 6 in the Z-axis direction (more specifically, the outer surface 40 of the flange portion 401b of the external terminal 4b) in the direction along this boundary, i.e., in a cross section (see FIG. 6B) transverse to the welding loci 710, 720, the dimension W1 of the welded portion 7 in the direction perpendicular to the Z-axis direction at the boundary position between the external terminal 4b and the bus bar 6 is larger than the thickness T1 of the first metal layer 41 (see FIG. 6B). That is, the width W1 of the welded portion 7 at this boundary position is larger than the thickness T1 of the first metal layer 41.

[0060] Furthermore, the shape of the welded portion 7 when viewed from the Z-axis direction is a cornerless ring (for example, an ellipse or a circle). That is, the welded portion 7 is formed in a cornerless ring shape when viewed from the Z-axis direction. In the welded portion 7 of this embodiment, the shape of the first welding locus 710 and the shape of the second welding locus 720 are both cornerless rings (so-called racetrack shapes in the example shown in FIG. 6A). Furthermore, in the welded portion 7 of this embodiment, the welding loci are formed in the shape of multiple concentric circles (for example, double circles).

[0061] First welding locus 710 is spaced apart from second welding locus 720. More specifically, first welding locus 710 and second welding locus 720 are spaced apart within a range where first welding portion 71 and second welding portion 72 overlap each other at the boundary between bus bar 6 and external terminal 4b. First welding locus 710 is also positioned more inward than second welding locus 720.

[0062] 7A and 7B, when the external terminal 4b and the bus bar 6 are welded by laser welding such that a welding locus is formed all around the circumference, the depth of penetration between the external terminal 4b and the bus bar 6 is deep in order to widen the width of the weld 7 at the boundary between the external terminal 4b and the bus bar 6 (top surface 40 of the external terminal 4b) in order to ensure the joint strength between the external terminal 4b and the bus bar 6. Therefore, in the conventional power storage device, the end 70 of the weld 7 reaches the interface 43 between the first metal layer 41 and the second metal layer 42 that constitute the clad material, and it is sometimes impossible to ensure the joint strength between the metal layers 41 and 42.

[0063] In contrast, in the energy storage device 11 of this embodiment, the end 70 of the weld 7 is located just before the interface 43 between the first metal layer 41 and the second metal layer 42 (see FIG. 6B), i.e., the weld 7 does not reach the interface 43 between the first metal layer 41 and the second metal layer 42 that constitute the clad material of the external terminal 4b, thereby ensuring the bonding strength between the metal layers 41, 42 that constitute the clad material.

[0064] When a laser with a small spot diameter (1.0 mm or less) is used to weld the bus bar 6 and the external terminal 4b, if the width of the weld 7 is small, the weld strength between the external terminal 4b and the bus bar 6 cannot be ensured. On the other hand, if the penetration depth of the weld 7 is increased to ensure the weld strength, the end 70 of the weld 7 reaches the interface between the first metal layer 41 and the second metal layer 42 of the external terminal (clad material) 4b, generating a copper-aluminum alloy, thereby reducing the strength of the external terminal 4b (more specifically, the flange 401b made of the clad material). Therefore, as a welding method for welding the external terminal 4b (flange 401b) and the bus bar 6 using a laser with a small spot diameter without reducing the interfacial strength of the clad material, a configuration is adopted in which the end 70 of the weld 7 does not reach the interface 43 between the first metal layer 41 and the second metal layer 42 of the clad material (external terminal 4b), as in the manufacturing method of the energy storage device 11 of this embodiment. Here, the spot diameter of laser welding in this embodiment refers to the width of the laser beam focused at the focal position. That is, the width of the laser beam focused on the upper surface of busbar 6 is the spot diameter.

[0065] Specifically, for example, as in the energy storage device 11 of this embodiment, the first welded portion 71 and the second welded portion 72 are partially overlapped with each other to ensure a wide joint width of the welded portion 7, thereby ensuring the joint strength between the bus bar 6 and the external terminal 4b. That is, compared to when the first welded portion 71 and the second welded portion 72 are welded while being separated from each other (not overlapping each other), the area of ​​the welded portion 7 (size of width W1: see FIG. 6(b)) is ensured by partially overlapping the first welded portion 71 and the second welded portion 72 as in the energy storage device 11 of this embodiment, and sufficient connection strength is obtained at the connection (welded) portion between the bus bar 6 and the external terminal 4b.

[0066] Furthermore, in the energy storage device 11 of this embodiment, the width W1 of the welded portion 7 at the boundary between the external terminal 4b and the busbar 6 is larger than the thickness T1 of the first metal layer 41, and therefore the dimensions of the welded portion 7 are sufficiently secured at this boundary. This ensures a sufficient bonding strength between the busbar 6 and the external terminal 4b. This ensures a sufficient bonding strength between the metal layers 41, 42 that constitute the clad material, while also ensuring a sufficient bonding strength between the busbar 6 and the external terminal 4b.

[0067] Furthermore, when the external terminal 4b (more specifically, the flange 401b) is configured such that the first metal layer 41 is made of aluminum and the second metal layer 42 is made of a copper clad material, as in the energy storage device 11 of the present embodiment, the electrical resistance of the external terminal 4b can be reduced by making the width W1 of the weld 7 at the boundary between the busbar 6 and the external terminal 4b larger than the thickness T1 of the first metal layer 41. That is, by making the width W1 at the boundary between the weld 7 larger than the thickness T1 of the first metal layer 41 while the end 70 of the weld 7 does not reach the interface 43 between the first metal layer 41 and the second metal layer 42, it is possible to reduce the overall electrical resistance of the external terminal 4b by thinning the aluminum layer (first metal layer 41), which has a higher electrical conductivity than copper, while ensuring sufficient welding strength between the external terminal 4b and the busbar 6.

[0068] In the energy storage device 11 of this embodiment, the busbar 6 and the external terminal 4b are cut at a position that crosses the welded portion 7 (welding trajectory 710, 720), and the cross section (cross section along the stacking direction) is etched. Since the corrosion speed differs between the welded portion 7 and other parts, it is possible to check the penetration depth (position in the Z-axis direction of the end portion 70), shape, width W1, etc. of the welded portion 7.

[0069] Furthermore, in the energy storage device 11 of this embodiment, the welded portion 7 is annular and has no corners, so even if a force is applied to the welded portion 7, the force is unlikely to be concentrated in one part of the welded portion 7. In other words, because the welded portion 7 is annular and has no corners, stress concentration at the welded portion 7 can be suppressed.

[0070] In the above-described manufacturing method of the energy storage device 11, the welded portion 7 does not reach the interface between the metal layers 41, 42 that make up the clad material of the external terminal 4b, so that the energy storage device 11 can be manufactured with the bonding strength between the metal layers 41, 42 that make up the clad material ensured.

[0071] Furthermore, in the manufacturing method of electricity storage device 11 of this embodiment, when welding is performed with a general welding width, it is possible to form annular welded portion 7 without corners, which makes it difficult for force to be concentrated in one area.

[0072] In the energy storage device 11 of this embodiment, the energy storage elements 1 are arranged in a direction perpendicular to the stacking direction of the external terminals 4b and the bus bars 6. This means that the stacking locations of the external terminals 4b and the bus bars 6 in each energy storage element 1 are not hidden by other energy storage elements, facilitating welding of the external terminals 4b and the bus bars 6. Furthermore, because the stacking locations of the external terminals 4b and the bus bars 6 are not hidden by other energy storage elements, it is easy to align the bus bars 6 and the external terminals 4b before welding.

[0073] The energy storage device and the method for manufacturing the energy storage device of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, or part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, part of the configuration of one embodiment can be deleted.

[0074] In the above embodiment, the shape of the welded portion 7 when viewed from the Z-axis direction is a shape without corners, but it may be a shape with corners (for example, a polygonal shape with corners, a linear shape, a broken line shape, etc.).

[0075] The shape of the welded portion 7 as viewed from the Z-axis direction is preferably a cornerless shape, and may be a cornerless arc shape. Even in this case, since the shape of the welded portion 7 is cornerless, even if a force is applied to the welded portion 7, the force is less likely to be concentrated in one part of the welded portion 7. Note that if the shape of the welded portion 7 is an arc shape, an arc shape having a length equal to or greater than a semicircle is more preferable in terms of ensuring the joint strength between the external terminal 4b and the bus bar 6 that constitute the clad material.

[0076] Furthermore, the shape of the welded portion 7 when viewed from the Z-axis direction may be a spiral shape without corners, etc. Note that the shape of the welded portion 7 when viewed from the Z-axis direction may be a curved shape, etc.

[0077] Although welded portion 7 includes two welding loci, first welding locus 710 and second welding locus 720, it may include one welding locus or three or more welding loci. When welded portion 7 has multiple welding loci, the multiple welding loci may be spaced apart from each other or may partially overlap each other. Note that when multiple welding loci overlap each other in welded portion 7, the welding output may be limited (adjusted) so that end 70 of welded portion 7 does not reach interface 43 between metal layers 41, 42.

[0078] The dimension (width W1) of the welded portion 7 in the direction along the boundary between the external terminal 4b and the bus bar 6 in the Z-axis direction (outer surface 40 of the external terminal 4) was larger than the thickness T1 of the first metal layer 41, but it may be the same as the thickness T1 of the first metal layer 41 or smaller than the thickness T1 of the first metal layer 41.

[0079] In the above embodiment, the flange (clad material) 401b of the external terminal 4b is composed of two metal layers, but it may be composed of three or more metal layers. Even in this case, the end 70 of the weld 7 is located closer to the busbar 6 than the interface between the first metal layer 41 adjacent to the busbar 6 and the second metal layer 42 adjacent to the first metal layer 41 in the flange (clad material) 401b of the external terminal 4b, thereby realizing a configuration in which the weld 7 does not reach the interface 43 between the metal layers 41, 42 that constitute the clad material.

[0080] Furthermore, in the above embodiment, the power storage device 11 includes a plurality of power storage elements 1, but it may include a single power storage element 1.

[0081] In the above embodiment, the case where the energy storage element is used as a chargeable and dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) has been described, but the type and size (capacity) of the energy storage element are arbitrary. In the above embodiment, a lithium ion secondary battery has been described as an example of the energy storage element, but the present invention is not limited to this. For example, the present invention can also be applied to energy storage elements of various secondary batteries, as well as primary batteries and capacitors such as electric double layer capacitors.

[0082] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims. [Explanation of symbols]

[0083] DESCRIPTION OF SYMBOLS 1...energy storage element, 2...electrode body, 3...case, 4, 4a, 4b...external terminal, 5...current collector, 6...bus bar, 7...welded portion, 11...energy storage device, 21...winding core, 22...laminated body, 31...case body, 32...cover plate, 33...internal space, 40...outer surface (upper surface), 41...first metal layer (metal layer), 42...second metal layer (metal layer), 43...interface, 70...end, 71...first welded portion, 72...second welded portion, 311...blocking portion, 312...body portion, 321...gas release valve, 401a, 401b...flange portion, 402a, 402b...shaft portion, 710...first welding locus, 720...second welding locus, W1...width

Claims

1. an energy storage element having a metal external terminal; a metal bus bar laminated on the external terminal and welded to the external terminal, a welded portion for welding the bus bar to the external terminal is formed on the bus bar; the welded portion extends from the bus bar to the external terminal, the external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer together, an end of the weld does not reach the interface between the first metal layer and the second metal layer; the weld includes a first weld and a second weld that partially overlap one another; the first welded portion and the second welded portion overlap each other at least at a boundary between the external terminal and the bus bar, In a cross section of the external terminal and the bus bar passing through the welded portion, the cross section is along a plane direction including a stacking direction of the external terminal and the bus bar and an orthogonal direction orthogonal to an extending direction of the welded portion at the cross-sectional position as viewed from the stacking direction, a dimension of the welded portion continuing in the orthogonal direction at a boundary position between the external terminal and the bus bar is larger than a thickness of the first metal layer. A power storage device characterized by:

2. The energy storage device according to claim 1 , wherein the welded portion has a circular or arc shape without corners when viewed from a stacking direction of the external terminal and the bus bar.

3. an energy storage element having a metal external terminal; a bus bar made of a metal including aluminum that is laminated on the external terminal and welded to the external terminal; a welded portion for welding the bus bar to the external terminal is formed on the bus bar; the welded portion extends from the bus bar to the external terminal, the external terminals include a positive external terminal and a negative external terminal, the positive electrode external terminal is made of a metal containing aluminum, the negative electrode external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the first metal layer is formed of a metal including aluminum; the second metal layer is formed of a metal including copper, the welded portion welds the bus bar and the first metal layer together, an end of the weld does not reach the interface between the first metal layer and the second metal layer; the weld includes a first weld and a second weld that partially overlap one another; the first welded portion and the second welded portion overlap each other at least at a boundary between the external terminal and the bus bar, In a cross section of the external terminal and the bus bar passing through the welded portion, the cross section is along a plane direction including a stacking direction of the external terminal and the bus bar and an orthogonal direction orthogonal to an extending direction of the welded portion at the cross-sectional position as viewed from the stacking direction, a dimension of the welded portion continuing in the orthogonal direction at a boundary position between the external terminal and the bus bar is larger than a thickness of the first metal layer. A power storage device characterized by:

4. the method includes stacking a metal bus bar on a metal external terminal of an energy storage element, and applying heat to the bus bar from the side opposite to the external terminal to weld the bus bar to the external terminal, thereby forming a welded portion in the bus bar that welds the bus bar to the external terminal; the welded portion extends from the bus bar to the external terminal, the external terminal has a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer together, an end of the weld does not reach the interface between the first metal layer and the second metal layer; the weld includes a first weld and a second weld that partially overlap one another; the first welded portion and the second welded portion overlap each other at least at a boundary between the external terminal and the bus bar, In a cross section of the external terminal and the bus bar passing through the welded portion, the cross section is along a plane direction including a stacking direction of the external terminal and the bus bar and an orthogonal direction orthogonal to an extending direction of the welded portion at the cross-sectional position as viewed from the stacking direction, a dimension of the welded portion continuing in the orthogonal direction at a boundary position between the external terminal and the bus bar is larger than a thickness of the first metal layer. A method for manufacturing an electricity storage device.

5. The method for manufacturing an energy storage device according to claim 4 , wherein the welded portion is formed in a cornerless ring shape or a cornerless arc shape when viewed from a stacking direction of the external terminal and the bus bar.

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