BATTERY PACK AND MANUFACTURING METHOD FOR A BATTERY PACK

Abstract

Method for manufacturing a battery pack (1; 301), wherein the battery pack comprises: several cells (100; 200), each comprising an outer terminal (137, 147; 237, 247); and a busbar (30; 330) made of a plate-shaped metal, wherein the busbar is arranged on a front surface (137c, 147c; 237c, 247c) of the outer terminal (137, 147; 237, 247c) and welded to it (137c, 147c; 237c, 247c), wherein Each of the cells (100; 200) comprises: a metal cell casing (110); the outer clamp (137, 147; 237, 247) made of plate-shaped metal and arranged on an outside of the cell housing (110); and an insulating part (183) made of a resin having electrical insulating properties and arranged between a front surface (110c) of the cell housing (110) and a rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247) to electrically insulate the cell housing (110) and the outer terminal (137, 147; 237, 247) from each other, the battery pack (1; 301) comprising a welded section (40; 340) in which the outer terminal (137, 147; 237, 247) and the busbar (30; 330) are welded together, the welded section (40; 340) being oriented in a thickness direction (DT) of the outer terminal (137, 147; 237, 247) extends from a front surface (30c; 330c) of the busbar (30; 330) towards the rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247), and the welded section (40; 340), separated by a space (S) in the thickness direction (DT) of the outer clamp (137, 147; 237, 247), is arranged at a distance from the insulating part (183), the procedure comprises the following steps: a cell preparation step (S1; T1) for preparing several of the cells (100; 200), each comprising the outer clamp (137, 147; 237, 247) which includes a separate section (137g, 147g; 237g, 247g) to be arranged through the space (S) between the outer clamp (137, 147; 237, 247) and the insulating part (183) in the thickness direction (DT) at a distance from the insulating part (183); an arrangement step (S3; T3) for arranging the busbar (30; 330) on the front surface (137c, 147c; 237c, 247c) of the outer terminal (137, 147; 237, 247) of each of the prepared cells (100; 200), such that a portion of the busbar (30; 330) becomes an opposing section (30g; 330g) which is arranged in the thickness direction (DT) of the outer terminal (137, 147; 237, 247) opposite the space (S) by placing the separate section (137g, 147g; 237g, 247g) of the outer terminal (137, 147; 237, 247) between it; and a laser welding step (S4; T4) for laser welding the opposite section (30g; 330g) of the busbar (30; 330) to the separate section (137g, 147g; 237g, 247g) of the outer terminal (137, 147; 237, 247), and wherein the laser welding step comprises projecting a laser beam (LB) from one side of the front surface (30c; 330c) of the busbar (30; 330) in the direction of space (S) in the thickness direction (DT) of the outer clamp (137; 237) to melt the opposite section (30g; 330g) of the busbar (30; 330) and the separate section (137g, 147g; 237g, 247g) of the outer clamp (137, 147; 237, 247) and thus to form the welded section (40; 340) in which the separate section (137g, 147g; 237g, 247g) and the opposite section (30g; 330g) are welded together, characterized in that the outer clamp (237, 247) comprises a clamp projection section (237h, 247h) that projects from the front surface (237c, 247c), the busbar (330) includes a concave busbar recess (330f) through which the terminal projection section (237h, 247h) can be fitted, and The assembly step comprises arranging the busbar (330) on the front surface (237c, 247c) of the outer terminal (237, 247) while fitting the terminal projection section (237h, 247h) into the busbar recess (330f).

Description

[0001] The present disclosure relates to a battery pack and a method for manufacturing the battery pack.

[0002] JP 2014-63696A discloses a battery pack comprising multiple cells, each including an outer terminal and a metal, plate-shaped busbar mounted on the front surface of the outer terminal and welded to it. Each cell comprises a metal cell housing, a metal, plate-shaped outer terminal located outside the cell housing, and an insulating element (part of a gasket) positioned between the front surface of the cell housing and the rear surface of the outer terminal to electrically isolate them from each other. The insulating element is made of a resin with electrical insulating properties.

[0003] The battery pack of the JP 2014-63696A includes a welded section where the outer terminal and the busbar are welded together. The welded section extends in the thickness direction of the outer terminal from the front surface of the busbar to the rear surface of the outer terminal. Specifically, the welded section extends from the front surface of the busbar to an intermediate position between the front and rear surfaces of the outer terminal such that it does not penetrate the outer terminal in the thickness direction.

[0004] In JP 2014-63696A, the outer terminal and the busbar are welded together by laser welding. More precisely, while the busbar is positioned on the front surface of the cell's outer terminal, a laser beam is directed onto the front surface of the busbar, i.e., from above the busbar in the thickness direction of the outer terminal, melting a portion of the busbar (i.e., a section that will form a welded section) and a portion of the outer terminal (i.e., a section that will form a welded section) to create the welded section where the portion of the busbar and the portion of the outer terminal are welded together.

[0005] A method for manufacturing a battery pack with the features of the preamble of claim 1 and a battery pack with the features of the preamble of claim 4 are disclosed in JP 2013 - 33 661 A. For a better understanding of the present invention, reference is also made to JP 2017 - 130 387 A.

[0006] The aforementioned laser welding process can impair the electrical insulation properties of the resin insulating component due to the heat generated during the welding process. Specifically, if, for example, a portion of the busbar (the section that will be welded) and a portion of the outer terminal (the section that will also be welded) are melted by laser beam irradiation, heat from the molten metal (i.e., the molten metal of the busbar or the outer terminal) can be transferred to the insulating component in contact with the rear surface of the outer terminal. This leads to a reduction in the insulating component's electrical insulation properties. This, in turn, can compromise the electrical insulation between the cell housing and the outer terminal.

[0007] The present disclosure has been made to solve the above-mentioned problems, and it is an objective to provide a method for manufacturing a battery pack designed to ensure electrical insulation between a cell housing and an external terminal, and the battery pack designed to ensure electrical insulation between a cell housing and an external terminal.

[0008] To achieve the above-mentioned objective, one aspect of the present disclosure provides a method for manufacturing a battery pack having the features listed in claim 1.

[0009] The aforementioned method is designed to manufacture the battery pack, which comprises the multiple cells, each of which includes an outer terminal and a busbar made of metal in the form of a plate, arranged on the front surface of the outer terminal, and welded to the outer terminal. Each cell comprises the metal cell casing, the plate-shaped outer terminal made of metal and arranged on the outside of the cell casing, and the insulating element made of a resin with electrical insulating properties. The insulating element is arranged between the front surface of the cell casing and the rear surface of the outer terminal to electrically isolate the cell casing and the outer terminal from each other.

[0010] Furthermore, the battery pack includes the welded section where the outer terminal and the busbar are welded together. The welded section extends in the thickness direction of the outer terminal from the front surface of the busbar towards the rear surface of the outer terminal. This welded section is also spaced apart by a gap located in the thickness direction of the outer terminal between the welded section and the insulating part. In other words, the gap is located in the thickness direction of the outer terminal between the welded section and the insulating part. Here, the thickness direction of the outer terminal refers to a direction directly from the front surface to the rear surface (or alternatively, from the rear surface to the front surface) of the outer terminal, which is perpendicular to either the front or rear surface.

[0011] In the aforementioned manufacturing process, the battery pack designed as described above is produced by the following steps.

[0012] In the cell preparation step, several cells are first prepared (cells in which the busbars are not yet welded to the outer terminals, i.e., cells in which the welded sections have not yet been formed). More precisely, in the cell preparation step, several cells are prepared such that each cell includes an outer terminal that has a separate section. This section is positioned at a distance from the insulating part, defined by the space between the outer terminal and the insulating part, in the thickness direction of the outer terminal.

[0013] In this assembly step, the busbars are sequentially arranged on the front surfaces of the outer terminals of the prepared cells. However, in this assembly step, the busbars are arranged on the front surfaces of the outer terminals of the cells such that a portion of each busbar becomes the opposite section, located across the space, by positioning the separate section of the outer terminal in the thickness direction between them.

[0014] In the subsequent laser welding step, the opposite section of the busbar and the separate section of the outer clamp are welded together by a laser. In this laser welding step, a laser beam is directed in the thickness direction of the outer clamp from the side (i.e., from a position at a distance from) the front surface of the busbar (i.e., the opposite section) onto the front surface of the busbar in the direction of space, in order to melt the opposite section of the busbar and the separate section of the outer clamp, thereby forming the welded section in which the separate section and the opposite section are welded together.In particular, the welded section is formed such that it extends in the thickness direction of the outer clamp from the front surface of the busbar towards the rear surface of the outer clamp and is furthermore arranged at a distance from the insulating part by the space that is located in the thickness direction of the outer clamp between the welded section and the insulating part, i.e. by the space that is located in the thickness direction of the outer clamp between the welded section and the insulating part.

[0015] According to this laser welding process, it is less likely that the heat generated during laser welding in the outer terminal and the like will be conducted to the resin insulating part. Specifically, in this laser welding process, the space in the thickness direction of the outer terminal is located between the resin section melted by the laser beam (i.e., the resin section melted by the molten opposite section of the busbar or the molten separate section of the outer terminal) and the insulating part. Thus, less heat from the molten resin section is transferred to the insulating part. Consequently, the electrical insulation properties of the insulating part are prevented from deteriorating due to the heat generated during laser welding. This ensures electrical insulation between the cell housing and the outer terminal.

[0016] Specific examples where the heat generated during laser welding degrades the electrical insulation properties of the insulating component include the following cases. For instance, if the heat generated during laser welding is transferred to the insulating component, it can deform in such a way that its thickness decreases at a certain point, or that a hole (or holes) forms in part of the insulating component, leading to a deterioration of its electrical insulation properties. In another case, the heat generated during laser welding can partially char the insulating component, so that the charred section has reduced electrical resistance, i.e., increased electrical conductivity, which also leads to a deterioration of the insulating component's electrical insulation properties.

[0017] Alternatively, the welded section can extend from the front surface of the opposite section of the busbar to the rear surface of the separate section of the outer terminal, that is, penetrate the opposite section of the busbar and the separate section of the outer terminal in the thickness direction. As a further alternative, the welded section can extend from the front surface of the opposite section of the busbar to an intermediate position between the front surface and the rear surface of the separate section of the outer terminal, that is, not penetrate the separate section of the outer terminal in the thickness direction.

[0018] In the manufacturing process described above, the laser welding step performs the laser welding such that the molten metal section, melted by laser beam irradiation, extends from the front surface of the busbar into the space, thus forming the welded section that extends from the front surface of the opposite busbar section to the rear surface of the separate outer terminal section. It should be noted that the molten metal section is a molten portion of the metal forming either the opposite busbar section or the separate outer terminal section.

[0019] Such laser welding, performed to bring the molten metal section into the space, allows at least some of the gas (air bubbles) contained in the molten metal to be released into the space. This process can reduce voids (e.g., micro-cavities formed by air bubbles) that can occur in the welded section, thus increasing its strength. Furthermore, this process can also increase the electrical conductivity of the welded section, thereby reducing the connection resistance between the busbar and the external terminal.

[0020] Furthermore, the space, which, as described above, is designed as an enclosed space, can absorb or collect at least some of the foreign substances, such as spatter generated during welding. Consequently, the amount of foreign substances, such as spatter, that are dispersed to the outside can be reduced, leading to a reduction in the pollution of the external environment.

[0021] The aforementioned manufacturing process of the battery pack can be designed such that the outer terminal includes a terminal recess with an opening in the rear surface of the outer terminal, wherein the terminal recess is designed to be recessed in a direction away from a front surface of the insulating part, the front surface being opposite the rear surface of the outer terminal and the space being a closed space (S) defined by the terminal recess of the outer terminal and the front surface of the insulating part, which closes the opening of the terminal recess.

[0022] In the aforementioned manufacturing process, the outer terminal of the cell used therein comprises a terminal recess that is open at its rear surface and is recessed in a direction away from the front surface of the insulating part. Within the cell used therein, the space is an enclosed space defined by the terminal recess of the outer terminal and the front surface of the insulating part, which closes the opening of the terminal recess. Since the cells designed as described above are prepared in the cell preparation step, and then the aforementioned assembly step and laser welding step are performed, the electrical insulation properties of the insulating part are prevented from deteriorating due to the heat generated during laser welding, thus increasing the electrical insulation between the cell housing and the outer terminal.

[0023] Furthermore, the manufacturing method of the battery pack according to the invention is designed such that the outer terminal comprises a terminal projection section that protrudes from the front surface, the busbar comprises a concave busbar recess through which the terminal projection section can be fitted, and the assembly step comprises arranging the busbar on the front surface of the outer terminal while the terminal projection section is fitted into the busbar recess.

[0024] In the manufacturing process described above, the outer terminal of each cell comprises the terminal projection section that protrudes from the front surface of the outer terminal, i.e., on the side where the busbar is located. Furthermore, the busbar comprises the concave busbar recess through which the terminal projection section of the outer terminal can be fitted.

[0025] In the assembly step, the busbar is further positioned on the front surface of the outer terminal, while the terminal projection section of the outer terminal is fitted into the busbar recess. When, in the assembly step, the busbar is positioned on the front surface of the outer terminal to fit the terminal projection section of the outer terminal into the busbar recess, a portion of the busbar—the aforementioned opposing section, that is, the section facing the space—is formed by positioning the separate section of the outer terminal between it and the busbar in the thickness direction of the outer terminal.

[0026] Since the terminal projection section of the outer terminal is fitted into the busbar recess, a subsequent laser welding step can be carried out, as described above, without causing a spatial displacement of the busbar with respect to the outer terminal.

[0027] If the terminal projection section of the outer terminal is part of the separate section, i.e., part of the front surface of the separate section, and the busbar recess is part of the opposite section, i.e., part of the rear surface of the opposite section, spatial displacement of the opposite section relative to the separate section can be prevented. This allows for proper welding of the opposite section and the separate section in the laser welding step.

[0028] The terminal projection section of the outer terminal can be formed, for example, by subjecting a flat, plate-shaped outer terminal to a press machining process. Simultaneously with the pressing of the flat, plate-shaped outer terminal, the terminal projection section, which protrudes from the front surface of the outer terminal (i.e., on the side where the busbar is located), is formed, as is the aforementioned terminal recess. The terminal recess is a recessed section that opens or has an opening in the rear surface of the outer terminal and is recessed in a direction away from the front surface of the insulating part, that is, in a direction from the side of the rear surface to the side of the front surface of the outer terminal. Thus, this terminal recess can form the aforementioned space.

[0029] The busbar recess can also be formed by pressing the flat, plate-shaped busbar. More precisely, the busbar recess can be formed as a cutout that opens into the rear surface of the busbar, or it can have an opening that is recessed in a direction away from the front surface of the outer clamp, that is, from the side of the rear surface to the side of the front surface of the busbar. When the flat, plate-shaped busbar is pressed simultaneously, the aforementioned busbar recess and the busbar protrusion section that projects from the front surface of the busbar are also formed. In this case, during the laser welding step, the laser beam can be directed so that it strikes this busbar protrusion section.

[0030] Another aspect of the present disclosure provides a battery pack with the features listed in claim 4.

[0031] The battery pack described above comprises the multiple cells, each of which includes the outer terminal and the metal, plate-shaped busbar that is mounted on and welded to the outer terminal. Each cell includes the metal cell casing, the metal, plate-shaped outer terminal located on the outside of the cell casing, and the insulating part made of electrically insulating resin. The insulating part is positioned between the front surface of the cell casing and the rear surface of the outer terminal to provide electrical insulation between the cell casing and the outer terminal.

[0032] Furthermore, the battery pack includes the welded section where the outer terminal and the busbar are welded together. The welded section extends in the thickness direction of the outer terminal from the front surface of the busbar towards the rear surface of the outer terminal. This welded section is also separated from the insulating part by a space located in the thickness direction of the outer terminal. In other words, the space is located in the thickness direction of the outer terminal between the welded section and the insulating part.

[0033] In the battery pack designed as described above, the electrical insulation properties of the insulating component are prevented from deteriorating due to the heat generated during welding between the outer terminal and the busbar. This allows the battery pack to be designed so that the cell casing and the outer terminal are reliably electrically insulated from each other. More specifically, in the welding step (e.g., the laser welding step) for welding the outer terminal and the busbar, it is less likely that, when a portion of the busbar forming the welded section and a portion of the outer terminal forming the welded section are melted, the heat from the molten metal is transferred to the insulating component because the space between the molten metal (i.e., the outer terminal) and the molten metal is less dense.The molten section of metal forming the busbar or outer terminal is located between the insulating part and the insulating part in the thickness direction of the outer terminal. This prevents the electrical insulation properties of the insulating part from deteriorating due to the heat generated during welding. This ensures electrical insulation between the cell housing and the outer terminal.

[0034] The welded section can extend from the front surface of the opposite section of the busbar to the rear surface of the separate section of the outer terminal, that is, penetrate the opposite section of the busbar and the separate section of the outer terminal in the thickness direction. Alternatively, the welded section can extend from the front surface of the opposite section of the busbar to an intermediate position between the front surface and the rear surface of the separate section of the outer terminal, that is, not penetrate the separate section of the outer terminal in the thickness direction.

[0035] In the battery pack described above, the outer terminal comprises the separate section, which is positioned at a distance from the insulating part by the space located in the thickness direction between the outer terminal and the insulating part. The busbar comprises the opposite section, which is positioned opposite the space by the separate section located in the thickness direction of the outer terminal between the busbar and the space. Furthermore, the welded section is designed as a welded section in which the opposite section and the separate section are welded together, extending from the front surface of the opposite section of the busbar to the rear surface of the separate section of the outer terminal. In such a battery pack, the welded section contains fewer voids.Thus, the battery pack can include the welded section, which has high strength and high electrical conductivity, and therefore low connection resistance between the busbar and the outer terminal.

[0036] More precisely, the welded section extending from the front surface of the opposite section of the busbar to the rear surface of the separate section of the outer terminal is produced, for example, by laser welding, such that the molten metal section irradiated by the laser beam—that is, the molten section of metal forming the opposite section of the busbar or the molten section of metal forming the separate section of the outer terminal—extends from the front surface of the busbar into the space. Such laser welding is carried out so that the molten metal reaches the space, thus enabling at least some of the gas (air bubbles) contained in the molten metal to be released into the space.This process can reduce voids that can form in the welded section, thus increasing its strength. Furthermore, this process can increase the electrical conductivity of the welded section, thereby reducing the connection resistance between the busbar and the external terminal.

[0037] Furthermore, if the space is designed as an enclosed space, as described above, it can absorb or collect at least some of the foreign substances, such as spatter generated during welding. Consequently, the amount of foreign substances, such as spatter, that are scattered to the outside can be reduced, leading to a decrease in the pollution of the surrounding environment.

[0038] Furthermore, the aforementioned battery pack can be designed such that the outer terminal includes a terminal recess with an opening in the rear surface of the outer terminal, the terminal recess is set back in a direction away from a front surface of the insulating part, the front surface being opposite the rear surface of the outer terminal, and the space is an enclosed space defined by the terminal recess of the outer terminal and the front surface of the insulating part, which closes the opening of the terminal recess.

[0039] In the battery pack described above, the outer terminal of the cell includes a terminal recess that opens in the rear surface of the outer terminal or has an opening that is recessed in a direction away from the front surface of the insulating part. The cell used therein is designed such that the space is a closed space defined by the terminal recess of the outer terminal and the front surface of the insulating part, which closes the opening of the terminal recess. By using cells designed as described above, the electrical insulation properties of the insulating part are prevented from deteriorating due to the heat generated during welding, thus increasing the electrical insulation between the cell casing and the outer terminal.

[0040] According to the invention, the aforementioned battery pack is designed such that the outer terminal comprises a terminal projection section that protrudes from the front surface, the busbar comprises a concave busbar recess through which the terminal projection section can be fitted, and the outer terminal and the busbar are welded together while the terminal projection section is fitted into the busbar recess.

[0041] In the battery pack described above, the outer terminal of each cell includes the terminal projection section that extends from the front surface of the outer terminal, i.e., on the side where the busbar is located. The busbar also includes the concave busbar recess through which the terminal projection section of the outer terminal fits into the concave busbar recess. In the battery pack described above, the outer terminal and the busbar are welded together while the terminal projection section is fitted into the busbar recess.

[0042] Since the outer clamp and the busbar are welded together while the clamp protrusion section is fitted into the busbar recess, this configuration prevents spatial displacement of the busbar relative to the outer clamp, which can occur when welding the outer clamp to the busbar. Therefore, in the battery pack described above, the busbar is welded to the outer clamp while the busbar is held in a suitable position relative to the outer clamp.

[0043] The terminal projection section of the outer terminal can be formed, for example, by subjecting a flat, plate-shaped outer terminal to a press machining process. Furthermore, simultaneously with the pressing of the flat, plate-shaped outer terminal, the terminal projection section, which protrudes from the front surface of the outer terminal (i.e., on the side where the busbar is located), is formed, as is the aforementioned terminal recess. Thus, this terminal recess can form the aforementioned space. Fig. 1 is a top view of a battery pack in a first and a second example; Fig. 2 is a partial section view of a cell in the first example; Fig. Figure 3 is an enlarged view of section B in Fig. 2; Fig. Figure 4 is an enlarged view of section C in Fig. 2; Fig. 5 is a perspective exploded view of a cover element that includes connections from the first example; Fig. Figure 6 is an enlarged cross-sectional view along line AA in Fig. 1 of a battery pack in the first example; Fig. Figure 7 is a perspective view of an outer clamp in the first example; Fig. Figure 8 is a flowchart showing a process flow of a manufacturing process for the battery pack in the first and second examples; Fig. Figure 9 is an example diagram for an ordering step in the first example; Fig. Figure 10 is an example diagram for a laser welding step in the first example; Fig. 11 is another explanatory diagram for the laser welding step in the first example; Fig. Figure 12 is an enlarged cross-sectional view along line AA in Fig. 1 of a battery pack in the second example; Fig. Figure 13 is an enlarged cross-sectional view of a cell in the second example, which is an enlarged view of section B in Fig. 2 corresponds to; Fig. Figure 14 is an enlarged cross-sectional view of a cell in the second example, which is an enlarged view of section C in Fig. 2 corresponds to; Fig. Figure 15 is an explanatory view for an arrangement step in the second example; Fig. Figure 16 is an explanatory view for a laser welding step in the second example; Fig. Figure 17 is another explanatory view for the laser welding step in the second example; and Fig. Figure 18 is another explanatory view for the arrangement step in the second example. First example

[0044] A first example of this revelation is described in detail below with reference to the accompanying drawings.

[0045] Fig. Figure 1 is a top view of a battery pack 1 in a first example. Fig. 2 is a partial section view of cell 100 in the first example. Fig. Figure 3 is an enlarged view of a line drawn with a dotted line in Fig. 2 shown excerpt B, and Fig. Figure 4 is an enlarged view of a line drawn with a dotted line in Fig. 2 shown excerpt C. Fig. Figure 5 is a perspective exploded view of part of a cover element 115 in the first example, which includes clamps. Fig. Figure 6 is an enlarged cross-sectional view along line AA in Fig. 1 of battery pack 1 in the first example.

[0046] The battery pack 1 in the first example comprises several cells 100, each comprising an outer terminal (i.e., a positive outer terminal 137 and a negative outer terminal 147), and several busbars 30, each made of metal in the form of a flat plate, wherein the busbars 30 are arranged on the front surfaces of the outer terminals (i.e., front surfaces 137c of the positive outer terminals 137 and front surfaces 147c of the negative outer terminals 147) and welded to the outer terminals (i.e., the positive outer terminals 137 and the negative outer terminals 147) (see the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. 6).

[0047] In the battery pack 1 in the first example, the multiple cells 100 form a cell stack 20. The cell stack 20 is assembled such that the cells 100 are in a row in a row direction DL (i.e., a right-left or transverse direction). Fig. 1) arranged and received in a housing cavity 10b of a housing 10 (see Fig. 1) In the cell stack 20 in the first example, the cells 100 are arranged in a row by alternately reversing the orientations of the cells 100 that are adjacent in the row direction DL, such that the positive outer terminal 137 of one cell 100 and the negative outer terminal 147 of an adjacent cell 100 are arranged next to each other in the row direction DL. In the first example, the housing 10 comprises two housing cavities 10b, each containing a cell stack 20 (the multiple cells 100 arranged in a row in the row direction DL).

[0048] In the battery pack 1 in the first example, each of the busbar 30 connects two adjacent outer terminals of the cells 100, which are arranged in series DL, more precisely the positive outer terminal 137 of one cell 100 and the negative outer terminal 147 of an adjacent cell 100 (see the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. 6) More precisely, a busbar 30 is welded to each pair of cells 100 arranged adjacent in the series direction DL such that a section of each busbar 30, arranged on one side in the series direction DL, is welded to an outer terminal (e.g., a positive outer terminal 137) of a cell 100 located on that side, and a section of each busbar 30, arranged on the other side in the series direction DL, is welded to an outer terminal (e.g., a negative outer terminal 147) of an adjacent cell 100 located on the other side. Therefore, the cells 100 forming the cell stack 20 are electrically connected in series.

[0049] Each of the 100 cells in the first example is a lithium-ion secondary battery, which, as in Fig. Figure 2 shows a cell housing body (hereinafter referred to simply as a housing body) 111, which has the shape of a rectangular box with an opening 111d, and an electrode body 150, which is received in the housing body 111. The electrode body 150 is a flat, wound electrode body formed by winding a strip-shaped positive plate 155, a strip-shaped negative plate 156, and overlapping separators 157 into a flat shape. Furthermore, each cell 100 comprises a plate-shaped cell housing cover (hereinafter referred to simply as a housing cover) 113, which closes the opening 111d of the housing body 111. The housing body 111 and the housing cover 113 are welded together as a single cell housing 110.

[0050] The housing cover 113 has the shape of a rectangular plate and has a longitudinal (right-left) orientation at both ends. Fig. 2) Circular through-holes 113h and 113k extend through the housing cover 113. The housing cover 113 also includes a safety valve 113j in its center in the longitudinal direction. The safety valve 113j is integrally formed with the housing cover 113 and forms part of the housing cover 113. A liquid inlet 113n for injecting an electrolyte (not shown) into the cell housing 110 is formed in the housing cover 113 between the safety valve 113j and the through-hole 113k (see Fig. 2) The liquid inlet 113n is closed with an inlet plug 113m.

[0051] Each of the cells 100 further comprises electrode terminal elements (i.e., a positive terminal element 130 and a negative terminal element 140), which are each connected to the electrode body 150 in the housing body 111 and extend outwards through the corresponding through-holes 113h and 113k of the housing cover 113 (see Fig. 2) The positive terminal element 130 is formed from a positive connecting element 135 and the positive outer terminal 137. The positive connecting element 135 is made of metal, is connected to the positive electrode plate 155 of the electrode body 150, and also extends outwards through the through-hole 113h of the housing cover 113.

[0052] The positive outer terminal 137 is manufactured in the form of a rectangular, flat metal plate (see the Fig. 3, Fig. 6 and Fig. 7) The positive outer clamp 137 has a cylindrical through-hole 137b extending through it in its thickness direction DT. The positive outer clamp 137 further comprises a clamping recess 137f located in a rear surface 137d of it 137, i.e., on a bottom side in the Fig. 3 and Fig. 6 and a top side in Fig. 7, opens. The terminal recess 137f comprises an opening which, in a plan view, has the shape of a rectangular plate and is recessed in one direction away from a front surface 183c of an insulating part 183, the front surface 183c being opposite the rear surface 137d of the positive outer terminal 137, i.e. the terminal recess 137f is in the Fig. 3 and Fig. 6 reset upwards. Fig. Figure 7 is a perspective view of the outer terminal (i.e., the positive terminal element 130 and the negative terminal element 140) in the first example.

[0053] The positive outer terminal 137 thus formed is arranged on the housing cover 113 (i.e., on the outside of the cell housing 110) and is electrically connected to the positive connecting element 135 on the outside of the cell housing 110. More precisely, a compressed section 133 of the positive connecting element 135 is in close contact with a front surface 137c of the positive outer terminal 137, thereby enabling an electrical connection with the positive outer terminal 137 (see Fig. 3) In particular, the cylindrical, compressed section 133, which projects outwards or upwards from the through-hole 137b of the positive outer terminal 137, is compressed and deformed into the shape of a circular disk on the outside of the cell housing 110, i.e. pressed, to widen its diameter and thus bring it into close contact with the front surface 137c of the positive outer terminal 137 and thereby enable an electrical connection with the positive outer terminal 137.

[0054] The negative terminal element 140 is formed from the negative connecting element 145 and the negative outer terminal 147. The negative connecting element 145 is made of metal, is connected to the negative electrode plate 156 of the electrode body 150, and extends outwards through the through-hole 113h of the housing cover 113.

[0055] The negative outer terminal 147 is manufactured in the form of a rectangular, flat metal plate (see the Fig. 4, Fig. 6 and Fig. 7) The negative outer clamp 147 has a cylindrical through-hole 147b extending through it in its thickness direction DT. The negative outer clamp 147 further comprises a clamping recess 147f located on its rear surface 147d, i.e., on a bottom side in the Fig. 4 and Fig. 6 and a top side in Fig. 7, opens. The terminal recess 147f comprises a rectangular opening in a plan view and is recessed in one direction away from the front surface 183c of the insulating part 183, with the front surface 183c opposite the rear surface 147d of the negative outer terminal 147, i.e. the terminal recess 147f is in the Fig. 4 and Fig. 6 reset upwards.

[0056] The negative outer terminal 147, designed as described above, is located on the housing cover 113 (i.e., on the outside of the cell housing 110) and is electrically connected to the negative connecting element 145 on the outside of the cell housing 110. More precisely, a compressed section 143 of the negative connecting element 145 is in close contact with a front surface 147c of the negative outer terminal 147, thus enabling an electrical connection with the negative outer terminal 147 (see Fig. 4) In particular, the cylindrical, compressed section 143, which projects outwards or upwards from the through-hole 147b of the negative outer terminal 147, is compressed and deformed on the outside of the cell housing 110 into the shape of a circular disk, i.e. pressed, to widen its diameter and thereby bring it into close contact with the front surface 147c of the negative outer terminal 147 and thereby enable an electrical connection with the negative outer terminal 147.

[0057] Furthermore, each cell 100 comprises a pair of first insulators 180, each made of electrically insulating resin and arranged on the housing cover 113. One of the first insulators 180 comprises an insulating part 183, which is arranged between the front surface 110c of the cell housing 110 (i.e., the front surface 113p of the housing cover 113) and the rear surface 137d of the positive outer terminal 137 to provide electrical insulation between them (see Fig. 3) The further first insulator 180 comprises an insulating part 183 which is arranged between the front surface 110c of the cell housing 110 (i.e. the front surface 113p of the housing cover 113) and the rear surface 147d of the negative outer terminal 147 to provide electrical insulation between them ( Fig. 4) These insulating parts 183 each comprise a through-hole 183b extending through them, in which an insertion part 132 of the positive terminal element 130 or an insertion part 142 of the negative terminal element 140 is inserted.

[0058] Each cell 100 further comprises a pair of secondary insulators 170, each arranged between the negative connecting element 145 of the negative terminal element 140 and the rear surface of the housing cover 113 to provide electrical insulation between them (see the Fig. 2 and Fig. 5) In each cell 100, the further second insulator 170 is also arranged between the positive connecting element 135 of the positive terminal element 130 and the rear surface of the housing cover 113.

[0059] Furthermore, in the first example, the battery pack 1 comprises a welded section 40 to which the outer terminal (i.e., the positive outer terminal 137 or the negative outer terminal 147) and the busbar 30 are welded together (see the Fig. 1 and Fig. 6) More precisely, the battery pack 1 comprises the welded section 40, which is formed by welding a section of the busbar 30, which is connected on one side in the series direction DL, that is, in the right-left direction. Fig. 1 and Fig. 6, is arranged, and the outer terminal (e.g., the positive outer terminal 137) of cell 100 is formed, and the welded section 40 is formed by welding a section of the busbar 30, which is arranged on the far side in the series direction DL, to the outer terminal (e.g., the negative outer terminal 147) of cell 100. These welded sections 40 each extend in the thickness direction DT (i.e., a top-bottom direction in Fig. 6) of the outer terminal (i.e. the positive outer terminal 137 or the negative outer terminal 147) from the front surface 30c of the busbar 30 towards the rear surface 137d or 147d of the outer terminal (i.e. the positive outer terminal 137 or the negative outer terminal 147).

[0060] Meanwhile, in battery pack 1 in the first example, as described above, the outer terminal, that is, the positive outer terminal 137 or the negative outer terminal 147, includes the terminal recess 137f or 147f, which is located in the rear surface 137d or 147d, i.e., downwards into the Fig. 3, Fig. 4 and Fig. 6 opens, and in a direction away from the front surface 183c of the insulating part 183, i.e. upwards into the Fig. 3, Fig. 4 and Fig. 6, is reset. In the battery pack 1 (each cell 100) in the first example, the openings of the terminal recesses 137f and 147f are also closed with the front surfaces 183c of the corresponding insulating parts 183, thereby forming respective spaces S (closed spaces) (see the Fig. 3, Fig. 4 and Fig. 6).

[0061] In battery pack 1 in the first example, as it is in Fig. As shown in Figure 6, each of the aforementioned welded section 40, through the space S, which extends in the thickness direction DT (i.e., in the height direction in Fig. 6) of the outer terminal, i.e., the positive outer terminal 137 and the negative outer terminal 147, is located between the welded section 40 and the insulating part 183, at a distance from the corresponding insulating part 183. In other words, the space S is located in the thickness direction DT of the outer terminal, i.e., the positive outer terminal 137 and the negative outer terminal 147, between the welded section 40 and the insulating part 183. The thickness direction DT of the outer terminal, i.e., the positive outer terminal 137 and the negative outer terminal 147, denotes a direction straight away from the front surfaces 137c and 147c of the outer terminal (i.e., the positive outer terminal 137 and the negative outer terminal 147) in the direction of the rear surfaces 137d and 147d. The thickness direction DT is also a direction perpendicular to the front surfaces 137c and 147c or the rear surfaces 137d and 147d.

[0062] The battery pack 1, configured as described above, is a battery pack comprising the insulating part 183, whereby a deterioration of its electrical insulation properties can be prevented by the heat generated during welding of the outer terminal (i.e., the positive outer terminal 137 or the negative outer terminal 147) and the busbar 30, so that the electrical insulation between the cell housing 110 and the outer terminal (i.e., the positive outer terminal 137 or the negative outer terminal 147) is ensured.

[0063] In particular, in the step of welding the outer terminal (i.e., the positive outer terminal 137 or the negative outer terminal 147) to the busbar 30, that is, in a laser welding step (step S4) described below, when a part of the busbar 30, corresponding to a section that becomes the welded section 40, and a part of the outer terminal (the positive outer terminal 137 or the negative outer terminal 147), corresponding to a section that becomes the welded section 40, are fused together, the space S in the thickness direction DT of the outer terminal (the positive outer terminal 137 or the negative outer terminal 147) is located between the molten metal section 41 (i.e., the molten metal section 41 formed from the molten busbar 30 or the molten outer terminal) and the insulating part 183.Therefore, it is less likely that the heat from the molten metal section 41 will be conducted to the insulating part 183 (see . Fig. 11) This configuration can prevent the electrical insulation properties of the insulating part 183 from deteriorating due to the heat generated during welding, and thus ensure the electrical insulation between the cell housing 110 and the outer terminal (the positive outer terminal 137 or the negative outer terminal 147).

[0064] In the battery pack 1 in the first example, the outer terminal (the positive outer terminal 137 or the negative outer terminal 147) further comprises a section (designated as a separate section 137g or 147g) that extends through the space S, which is oriented in the thickness direction DT, i.e., in the height direction into the Fig. 3, Fig. 4 and Fig. 6, located in between (see the Fig. 3, Fig. 4 and Fig. 6), is arranged at a distance from the insulating part 183. The busbar 30 comprises a section (referred to as an opposing section 30g) which connects to space S via the separate section 137g or 147g, which is oriented in the thickness direction DT of the outer terminal (the positive outer terminal 137 or the negative outer terminal 147) (see the Fig. 6 and Fig. 9) is located in between, opposite each other.

[0065] In the welded section 40, the opposing section 30g and the separate section 137g or 147g are welded together in such a way that the welded section extends from the front surface (the upper surface in the Fig. 6 and Fig. 11) of the opposite section 30g of the busbar 30 to the rear surface (the lower surface in the Fig. 6 and Fig. 11) of the separate section 137g or 147g of the outer terminal (the positive outer terminal 137 or the negative outer terminal 147). Such a battery pack 1 is a battery pack with reduced voids in the welded sections 40. In the battery pack 1, the welded sections 40 therefore have high strength and also high electrical conductivity. Thus, both the connection resistance between the busbar 30 and the positive outer terminal 137 and the connection resistance between the busbar 30 and the negative outer terminal 147 are low.

[0066] In particular, the welded section 40, which extends from the front surface (the upper surface into the Fig. 6 and Fig. 11) of the opposite section 30g of the busbar 30 to the rear surface (the lower surface in the Fig. 6 and Fig. 11) of the separate section 137g or 147g of the outer terminal (the positive outer terminal 137 or the negative outer terminal 147), produced by laser welding as described below, in which the molten metal section 41 (a molten section of the metal forming the opposite section 30g of the busbar 30, or a molten section of the metal forming the separate section 137g or 147g of the outer terminal) melted by irradiation with the laser beam LB extends from the front surface 30c of the busbar 30 (i.e., from the front surface of the opposite section 30g) to the space S (see the Fig. 6 and Fig. 11).

[0067] The laser welding process described above, which causes the molten metal section 41 to reach space S, can release at least some of the gas (air bubbles) contained in the molten metal section 41 into space S. This reduces voids (i.e., micro-cavities that can be formed by air bubbles) that can be created in the welded section 40, thereby increasing the strength of the welded section 40 and, furthermore, its electrical conductivity. Consequently, the connection resistance between the busbar 30 and the positive outer terminal 137, as well as the connection resistance between the busbar 30 and the negative outer terminal 147, can be reduced.

[0068] Furthermore, such a space S, which is formed as an enclosed space as described above, can absorb or collect at least some of the foreign substances generated during laser welding, such as spatter. Consequently, the amount of foreign substances, such as spatter, that are dispersed to the outside can be reduced, leading to a reduction in the contamination of the external environment.

[0069] The manufacturing process of battery pack 1 in the first example is described below. Fig. Figure 8 is a flowchart showing the process flow of the manufacturing process for battery pack 1 in the first example. In step S1 (a cell preparation step), several cells 100 are prepared, but in none of these cells is the busbar 30 already welded to the positive outer terminal 137 and the negative outer terminal 147 (see Figure 8). Fig. 2).

[0070] In particular, in step S1 (the cell preparation step), several cells 100, comprising outer terminals (the positive outer terminals 137 and the negative outer terminals 147), which include the separate sections 137g and 147g, are prepared (see the Fig. 3 and Fig. 4) In each cell 100 in the first example, the spaces S are each designed as a closed space defined by the terminal recess 137f of the positive outer terminal 137 and the front surface 183c of an insulating part 183, which closes the opening of the terminal recess 137f, or by the terminal recess 147f of the negative outer terminal 147 and the front surface 183c of the further insulating part 183, which closes the opening of the terminal recess 147f.

[0071] In step S2 (a cell stack manufacturing step, see Fig. 8), the predetermined number of prepared cells (100) is placed successively in a row in the row direction DL (in the right-left direction). Fig. 1) arranged to produce a cell stack 20. More precisely, in the first example, the cell stack 20 is produced in such a configuration that the cells 100 are arranged in a row by alternately reversing the orientation of the cells 100 that are adjacent in the row direction DL, such that the positive outer terminal 137 of a cell 100 and the outer terminal 147 of a cell 100 adjacent to it in the row direction DL are arranged next to each other (see Fig. 1).

[0072] The cell stack 20 is then housed in the housing cavity 10b of the housing 10. In the first example, a cooling plate is arranged between the cells 100, which are adjacent in the row direction DL. Furthermore, end plates are arranged successively at both ends in the row direction DL of the cell stack 20. The housing 10 comprises two housing cavities 10b. In the first example, two sets of cell stacks 20 (each comprising several cells 100 arranged in a row in the row direction DL) are therefore housed successively in the housing cavities 10b (see Fig. 1).

[0073] Then, in step S3 (an arrangement step, see Fig. 8), as it is in Fig. As shown in Figure 9, for each individual cell stack 20, a busbar 30 is arranged over two adjacent front surfaces of the outer terminals of the cells 100 arranged next to each other in the row direction DL. That is, each busbar 30 is arranged on the front surface 137c of the positive outer terminal 137 of one cell 100 and on the front surface 147c of the negative outer terminal 147 of an adjacent cell 100. More precisely, a portion of the busbar 30 on one side in the row direction DL (a left side in Fig. 9) arranged busbar 30 on the front surface of the outer terminal (i.e., on the front surface 137c of the positive outer terminal 137 in the Fig. (Example 9 shown) of cell 100 on one side of two cells 100 arranged adjacent in the row direction DL, and furthermore a part of the busbar 30 arranged in the row direction DL on the other side (a right side in Fig. 9) on the front surface of the outer terminal (i.e., on the front surface 147c of the negative outer terminal 147 in the Fig. (Example 9 shown) of cell 100 on the next page.

[0074] In step S3 (the arrangement step), however, the busbar 30 is arranged on and above the front surface 137c of the positive outer terminal 137 and the front surface 147c of the negative outer terminal 147 adjacent to it, such that a part of the busbar 30 (i.e., a section arranged at each end in the series direction DL) extends to space S via the separate section 137g or 147g of the outer terminal in the thickness direction DT (in the height direction in Fig. 9) the section 30g opposite the outer terminal (the positive outer terminal 137 or the negative outer terminal 147). Fig. 9 is a cross-sectional view showing two in Fig. 6 cells shown, 100 indicates that two cells 100 along line AA in Fig. 1, to which step S3 (the ordering step) is applied.

[0075] Subsequently, in step S4 (a laser welding step), the opposing sections 30g of the busbar 30 are welded by laser to the corresponding separate sections 137g and 147g of the outer terminals (i.e., the positive outer terminal 137 and the negative outer terminal 147) (see Fig. 10). More precisely, the opposite section 30g of the busbar 30, which is on one side (a left side in Fig. 10) is arranged in the series direction DL, to the separate section of the outer terminal (the separate section 137g of the positive outer terminal 137 in which in Fig. (Example 10 shown) of cell 100 on one side of two cells 100 arranged adjacent in the row direction DL is welded, while the opposite section 30g of the busbar 30, which is on the further side (a right side in Fig. 10) is arranged in the series direction DL, to the separate section of the outer terminal (the separate section 147g of the negative outer terminal 147 in which in Fig. (Example 10 shown) of cell 100 is welded to the other side.

[0076] In this step S4 (the laser welding step), the laser beam LB is directed in the thickness direction DT (downwards inwards). Fig. 10) of the outer terminals (the positive outer terminal 137 and the negative outer terminal 147) from the side (i.e. from a position away from) the front surface 30c of the busbar 30 (of the opposite section 30g), that is, from above the busbar 30 in Fig. 10, in the direction of space S. In other words, the laser beam LB is directed in the thickness direction DT onto the front surface 30c of the busbar 30 (of the opposite section 30g) in the direction of space S. This laser radiation melts the opposite section 30g of the busbar 30 and the separate sections 137g and 147g of the outer terminals (the positive outer terminal 137 and the negative outer terminal 147), thereby forming the welded sections 40, where the opposite section 30 and the separate section 137g or 147g are welded together (see the Fig. 6, Fig. 10 and Fig. 11).

[0077] More precisely, each welded section 40 is designed to extend in the thickness direction DT of the outer terminal (i.e., the positive outer terminal 137 and the negative outer terminal 147) from the front surface 30c of the busbar 30 towards the rear surface of the outer terminal (i.e., the rear surface 137d of the positive outer terminal 137 or the rear surface 147d of the negative outer terminal 147), and further designed to be spaced at a distance from the insulating part 183 through the space S located in the thickness direction DT of the outer terminal, that is, designed such that the space S is located in the thickness direction DT of the outer terminal between the welded section 40 and the insulating part 183 (see the Fig. 6 and Fig. 11). The Fig. 10 and Fig. 11 are cross-sectional views, each showing the states of two in Fig. The 6 cells shown represent 100, i.e., two cells 100 along line AA in Fig. 1, during step S4 (the laser welding step).

[0078] Due to step S4 (the laser welding step) performed as described above, it is less likely that the heat generated in the outer terminals (i.e., the positive outer terminal 137 and the negative outer terminal 147) and the like during laser welding will be conducted to the resin-made insulating part 183. Specifically, in step S4 (the laser welding step), space S is located in the thickness direction DT of the outer terminals (the positive outer terminal 137 and the negative outer terminal 147) between the molten metal section 41 (i.e., the molten metal section 41 formed from the molten opposite section 30g of the busbar 30 or the molten separate section 137g or 147g of the outer terminal) and the insulating part 183, so that it is less likely that the heat from the molten metal section 41 will be conducted to the insulating part 183 (see Fig. 11) Consequently, the electrical insulation properties of the insulating part 183 are prevented from deteriorating due to the heat generated during laser welding, thus ensuring electrical insulation between the cell housing 110 and the outer terminal (i.e., the positive outer terminal 137 and the negative outer terminal 147).

[0079] A concrete example of how the electrical insulation properties of insulating part 183 deteriorate due to the heat generated during laser welding could include a case where the insulating part 183 is deformed by the heat generated during laser welding, thus partially reducing its thickness, or alternatively, where a pore (or holes) is formed in the insulating part 183, leading to a deterioration of its electrical insulation properties. Another conceivable scenario is where, when the insulating part 183 is exposed to the heat generated during laser welding, it becomes partially charred, thus decreasing the electrical resistance of such a charred section, i.e., increasing its electrical conductivity, which also leads to a deterioration of the insulating part 183's electrical insulation properties.

[0080] In step S4 (the laser welding step) in the first example, however, the laser welding is carried out by laser welding to cause the molten metal section 40 (i.e., the molten section of metal forming the opposite section 30g of busbar 30, or the molten section of metal forming the separate sections 137g and 147g of the outer clamp) melted by irradiation with the laser beam LB to extend from the front surface 30c of busbar 30 (i.e., from the front surface of the opposite section 30g) and reach space S, as shown in Fig. Figure 11 shows that the welded section 40 extends from the front surface of the opposite section 30g of the busbar 30 (i.e., the upper surface in the Fig. 6 and Fig. 11) to the rear surface of the separate section 137g or 147g (i.e. the lower surface in the Fig. 6 and Fig. 11) the outer terminal (i.e. the positive outer terminal 137 or the negative outer terminal 147).

[0081] The laser welding, performed as described above so that the molten metal section 41 reaches space S, allows at least some of the gas (air bubbles) contained in the molten metal section 41 to escape into space S. This process can reduce voids that can be created in the welded section 40 and thus increase the strength of the welded section 40. Furthermore, this process can also increase the electrical conductivity of the welded section 40 and thus reduce the connection resistance between the busbar 30 and the positive outer terminal 137 and the connection resistance between the busbar 30 and the negative outer terminal 147.

[0082] In the first example, as described above, each of the spaces S is a closed space defined by the terminal recess 137f of the positive outer terminal 137 and the front surface 183c of the insulating part 183, which closes the opening of the terminal recess 137f, or by the terminal recess 147f of the negative outer terminal 147 and the front surface 183c of the further insulating part 183, which closes the opening of the terminal recess 147f (see Fig. 11) These spaces allow for the capture or collection of at least some of the foreign matter, such as spatter, generated during laser welding. Consequently, in step S4 (the laser welding step), the amount of foreign matter, such as spatter, scattered outwards can be reduced, leading to a reduction in the contamination of the external environment.

[0083] Since the busbar 30 is welded to the outer terminals (the positive outer terminal 137 and the adjacent negative outer terminal 147) of the cells 100 arranged adjacent in series DL as described above, the cells 100 adjacent in series DL are electrically connected in series by the busbar 30. Consequently, several cells 100 forming the cell stack 20 are electrically connected in series. As described above, a battery pack 1 is produced in the first example. Second example

[0084] Battery pack 301 in the second example differs from battery pack 1 in the first example in the shape of the outer terminals (one positive and one negative) of a cell and the shape of a busbar. However, other components or parts are identical to those of battery pack 1 in the first example. Therefore, the following explanation focuses on the differences compared to the first example, and identical or similar configurations are not discussed here.

[0085] A cell 200, which forms a battery pack 301 in the second example, differs from the cell 100 in the first example only in its outer terminals (the positive outer terminal and the negative outer terminal), but other components or parts are identical to or similar to those of cell 100. In particular, a positive outer terminal 237 in the second example comprises a terminal projection section 237h, which is enclosed by a front surface 237c, i.e., on the side on which a busbar 330 is arranged, extending from the top in the Fig. 12 and Fig. 13 corresponds to, protrudes. The positive outer terminal 237 further comprises a terminal recess 237f, which is located on an opposite side (i.e., a bottom side in the Fig. 12 and Fig. 13) of the terminal projection section 237h and opens on a rear surface 237d of the positive outer terminal 237, i.e., the opening on a bottom side in the Fig. 12 and Fig. 13 possesses. The clamping recess 237f is set back from the rear surface 237d towards the front surface 237c of the positive outer clamp 237. This clamping projection section 237h and this clamping recess 237f each have a hemispherical surface.

[0086] Fig. Figure 12 is an enlarged cross-sectional view along line AA in Fig. 1 of battery pack 301 in the second example. Fig. Figure 13 is an enlarged cross-sectional view of cell 200 in the second example, which is an enlarged view of section B in Fig. 2 corresponds. Fig. Figure 14 is an enlarged cross-sectional view of cell 200 in the second example, which is an enlarged view of section C in Fig. 2 corresponds.

[0087] In the second example, the clamp projection section 237h of the positive outer clamp 237 is deformed such that a rectangular, flat, plate-shaped, positive outer clamp (a substrate) is subjected to a pressing operation. When this rectangular, flat, plate-shaped, positive outer clamp (the substrate) is pressed, the clamp projection section 237h protrudes from the front surface 237c, and simultaneously the clamp recess 237f opens in the rear surface 237d, that is, it is recessed from the rear surface 237d towards the front surface 237c.

[0088] In the battery pack 301 (cell 200) in the second example, the opening of the terminal recess 237f is closed with the front surface 183c of the insulating part 183, thereby forming a space S (a closed space) (see the Fig. 12 and Fig. 13) Furthermore, the clamp projection section 237h of the positive outer clamp 237 is a part (a part of the front surface) of a separate section 237g, which is defined by the space S, which extends in the thickness direction DT of the positive outer clamp 237, i.e., in the height direction into the Fig. 12 and Fig. 13, located in between, is arranged at a distance from the insulating part 183.

[0089] The negative outer terminal 247 in the second example has the same shape as the aforementioned positive outer terminal 237. In particular, the negative outer terminal 247 comprises a terminal projection section 247h that is bordered by a front surface 247c, i.e., on the side where the busbar 330 is located, which faces the top in the Fig. 12 and Fig. 14 corresponds, protrudes, and a terminal recess 247f on an opposite side (i.e., on a bottom side in the Fig. 12 and Fig. 14) of the terminal projection section 247h. The terminal projection section 247h and the terminal recess 247f of the negative outer terminal 247 are thus formed by press machining in a similar manner to the positive outer terminal 237.

[0090] In the battery pack 301 (cell 200) in the second example, the opening of the terminal recess 247f is closed with the front surface 183c of the insulating part 183, thereby forming a space S (a closed space) (see the Fig. 12 and Fig. 14). Furthermore, the clamp projection section 247h of the negative outer clamp 247 is a part (a part of a front surface) of a separate section 247g, which is defined by the space S, which extends in the thickness direction DT of the negative outer clamp 247, i.e., in the height direction into the Fig. 12 and Fig. 14, located in between, is arranged at a distance from the insulating part 183.

[0091] Each busbar 330 in the second example includes a concave busbar recess 330f into which the terminal projection section 237h of the positive outer terminal 237 can be fitted, and a concave busbar recess 330 into which the terminal projection section 247h of the negative outer terminal can be fitted (see Fig. 12) The busbar recess 330f has an opening in a rear surface 330d of the busbar 330 and is recessed from the rear surface 330d towards the front surface 330c of the busbar 330. Furthermore, each busbar 330 includes a busbar projection section 330h, which extends upwards from the front surface of the busbar recess 330f. Fig. 12, protrudes. The conductor rail recess 330f and the conductor rail projection section 330h each have a hemispherical surface.

[0092] In the second example, the busbar recess 330f is also formed such that a rectangular, flat, plate-shaped busbar 330 (a substrate) is subjected to a pressing operation. When this rectangular, flat, plate-shaped busbar 330 (the substrate) is pressed, the aforementioned busbar recess 330f and simultaneously the aforementioned busbar projection section 330h are formed. In the second example, the busbar recess 330f and the busbar projection section 330h of the busbar 330 form part of the opposite section 330g. More precisely, the busbar recess 330f becomes a rear section of the opposite section 330g, and the busbar projection section 330h becomes a front section of the opposite section 330g (see the Fig. 12 and Fig. 15). The opposite section 330g is part of the busbar 330, which is opposite space S via the separate section 237g or 247g in the thickness direction DT of the outer terminal (i.e. the positive outer terminal 237 or the negative outer terminal 247).

[0093] Furthermore, in the battery pack 301 in the second example, as shown in Fig. As shown in Figure 12, the outer terminals (i.e., the positive outer terminal 237 and the negative outer terminal 247) and the busbar 330 are welded together, while the terminal projection section 237h of the positive outer terminal 237 and the terminal projection section 247h of the negative outer terminal 247 are fitted into the corresponding busbar recesses 330f of the busbar 330.

[0094] When the busbar 330 is welded to the outer terminals (the positive outer terminal 237 and the negative outer terminal 247), the terminal projection section 237h of the positive outer terminal 237 and the terminal projection section 247h of the negative outer terminal 247 are fitted into the busbar recesses 330f of the busbar 330. This prevents the busbar 330 from causing any spatial displacement with respect to the outer terminals (the positive outer terminal 237 and the negative outer terminal 247). Therefore, in the second example, the battery pack 301 is designed such that the busbar 330 is welded to the outer terminals (the positive outer terminal 237 and the negative outer terminal 247), while the position of the busbar 330 is held appropriately relative to the outer terminals (the positive outer terminal 237 and the negative outer terminal 247).

[0095] The manufacturing process of battery pack 301 in the second example is described below. Fig. Figure 8 is a flowchart showing the process flow of the manufacturing process for battery pack 301 in the second example. In step T1 (a cell preparation step), several cells 200 are prepared first. That is, several cells 200 in which the busbar 330 is not yet welded to the positive outer terminal 237 and the negative outer terminal 247.

[0096] In step T2 (a cell stack manufacturing step, see Fig. 8) The predetermined number of prepared cells 200 are successively placed in a row in the row direction DL (in the right-left direction). Fig. 1) arranged to produce a cell stack 320. In the second example, as in the first example, the cell stack 320 is produced in a configuration in which the cells 200 are aligned in a row by alternately reversing the orientation of the cells 200 adjacent in the row direction DL, such that the positive outer terminal 237 of one cell 200 and the negative outer terminal 247 of a cell 200 adjacent to it in the row direction DL are arranged next to each other (see Fig. 1).

[0097] The cell stack 320 is then housed in the housing cavity 10b of the housing 10 (see Fig. 1) In the second example, as in the first example, a cooling plate is arranged between the cells 200 that are adjacent in the row direction DL. Furthermore, end plates are successively arranged at both ends in the row direction DL of the cell stack 320.

[0098] Then, in step T3 (an arrangement step, see Fig. 8), will be, as it says in Fig. As shown in Figure 15, for each of the cell stacks 320, the respective busbars 330 are arranged over two adjacent front surfaces of the outer terminals of the cells 200 arranged next to each other in the row direction DL. That is, each busbar 330 is arranged on the front surface 237c of the positive outer terminal 237 of one cell 200 and on the front surface 247c of the negative outer terminal 247 of a cell 200 adjacent to that cell. More precisely, a busbar 330 is arranged on one side in the row direction DL (a left side in Fig. 15) the part of the busbar 330 located on the front surface of the outer terminal (i.e., on the front surface 237c of the positive outer terminal 237 in the Fig. (Example 15 shown) of cell 200 on one side of two adjacent cells 200 arranged in the row direction DL and furthermore on the other side in the row direction DL (a right side in Fig. 15) arranged part of the busbar 330 on the front surface of the outer terminal (i.e. on the front surface 247c of the negative outer terminal 247 in the in Fig. (Example 15 shown) of cell 200 of the next page. Fig. 15 is a cross-sectional view showing that two in Fig. 12 cells 200 shown (two cells 200 along line AA in Fig. 1) be subjected to step T3 (the ordering step).

[0099] In the second example, however, the busbar 330 is arranged on and above the front surfaces of the outer terminals (i.e., the front surface 237c of the positive outer terminal 237 and the front surface 247c of the negative outer terminal 247), while the terminal projection sections of the outer terminals (i.e., the terminal projection section 237h of the positive outer terminal 237 and the terminal projection section 247h of the negative outer terminal 247) are fitted into the corresponding busbar recesses 330f of the busbar 330. At this point, the busbar recess 330f and the busbar projection section 330h of the busbar 330 form part of the aforementioned opposite section 330g. In particular, the busbar recess 330f becomes a rear section of the opposite section 330g and the busbar projection section 330h becomes a front section of the opposite section 330g (see Fig. 15).

[0100] Since the terminal projection sections of the outer terminals (i.e., terminal projection section 237h of the positive outer terminal 237 and terminal projection section 247h of the negative outer terminal 247) are fitted into the busbar recesses 330f of the busbar 330, as described above, the busbar recess 330f and the busbar projection section 330h of the busbar 330 can form the opposite section 330g. Therefore, in the following step S4 (the laser welding step), when the laser beam is directed towards the busbar projection sections 330h, the opposite sections 330g of the busbar 330 can be suitably welded to the separate sections 237g and 247g of the outer terminals (i.e., the positive outer terminal 237 and the negative outer terminal 247).

[0101] Since the terminal projection sections of the outer terminals (i.e., terminal projection section 237h of the positive outer terminal 237 and terminal projection section 247h of the negative outer terminal 247) are fitted into the busbar recesses 330f of the busbar 330, it is possible to prevent the busbar 330 from causing any spatial displacement with respect to the outer terminals (i.e., the positive outer terminal 237 and the negative outer terminal 247). In the second example, each of the terminal projection sections of the outer terminals (i.e., terminal projection section 237h of the positive outer terminal 237 and terminal projection section 247h of the negative outer terminal 247) becomes part of the separate section 237g or 247g, and each busbar recess 330f becomes the corresponding opposite section 330g.This configuration can prevent a spatial displacement of the opposite sections 330g with respect to the separate sections 237g and 247g.

[0102] In step T4 (the laser welding step), the opposing sections 330g of the busbar 330 are then welded by laser to the corresponding separate sections 237g and 247g of the outer terminals (i.e., the positive outer terminal 237 and the negative outer terminal 247) (see Fig. 16). In the second example, the laser beam LB is directed in the thickness direction DT (downwards in Fig. 16) of the outer terminals (the positive outer terminal 237 and the negative outer terminal 247) from the side (i.e. from a position away from) the front surface 330c of the busbar 330 (of the opposite section 330g), that is, from above the busbar 330 in Fig. 16 in the direction of the terminal projection sections of the outer terminals (i.e., in the direction of terminal projection section 237h of the positive outer terminal 237 and terminal projection section 247h of the negative outer terminal 247). Consequently, the opposing sections 330g of the busbar 330 and the separate sections 237g and 247g of the outer terminals (of the positive outer terminal 237 and the negative outer terminal 247) are melted, forming all welded sections 340, where each separate section 237g or 247g and the opposing section 330g are welded together (see the Fig. 12 and Fig. 17).

[0103] More precisely, each welded section 340 extends in the thickness direction DT of the outer terminal (i.e., the positive outer terminal 237 and the negative outer terminal 247) from the front surface 330c of the busbar 330 towards the rear surface of the outer terminal (i.e., the rear surface 237d of the positive outer terminal 237 or the rear surface 247d of the negative outer terminal 247) and is arranged by the space S in the thickness direction DT of the outer terminal between it at a distance from the insulating part 183, that is, it is designed such that the space S is located in the thickness direction DT of the outer terminal between the welded section 340 and the insulating part 183 (see the Fig. 12 and Fig. 17). The Fig. 16 and Fig. 17 are cross-sectional views, each showing the states of two in Fig. The 12 cells shown represent 200, i.e., two cells 200 along line AA in Fig. 1, during step T4 (the laser welding step).

[0104] Due to step T4 (the laser welding step) as described above, it is less likely that the heat generated during laser welding in the outer terminals (i.e., the positive outer terminal 237 and the negative outer terminal 247) and the like will be conducted to the resin insulating part 183. Specifically, in step T4 (the laser welding step), space S is located in the thickness direction DT of the outer terminals (i.e., the positive outer terminal 237 and the negative outer terminal 247) between the molten metal section 341 (i.e., the molten metal section 341 generated from the molten opposite section 330g of the busbar 330 or the molten separate sections 237g or 247g of the outer terminal) and the insulating part 183, so that it is less likely that the heat from the molten metal section 341 will be conducted to the insulating part 183 (see Fig. 17). Consequently, the electrical insulation properties of the insulating part 183 are prevented from deteriorating due to the heat generated during laser welding, thus ensuring electrical insulation between the cell housing 110 and the outer terminal (i.e., the positive outer terminal 237 and the negative outer terminal 247).

[0105] In the second example, as in the first example, laser welding is performed to cause the molten metal section 341 (i.e., the molten section of metal forming the opposite section 330g of the busbar 330, or the molten section of metal forming the separate sections 237g and 247g of the outer terminals) melted by irradiation with the laser beam LB to extend from the front surface 330c of the busbar 330 (i.e., from the front surface of the opposite section 330g) and reach space S, as shown in Fig. 17 is shown. Accordingly, the welded section 340 extends from the front surface of the opposite section 330g of the busbar 30 (i.e., from the upper surface into the Fig. 12 and Fig. 17) to the rear surface of the separate section 237g or 247g of the outer clamp (i.e. the positive outer clamp 237 or the negative outer clamp 247).

[0106] The laser welding, performed as described above so that the molten metal section 341 reaches space S, allows at least some of the gas (air bubbles) contained in the molten metal section 341 to escape into space S. This process can reduce voids that may form in the welded section 340 and thus increase the strength of the welded section 340. Furthermore, this process can increase the electrical conductivity of the welded section 340 and thus reduce the connection resistance between the busbar 330 and the positive outer terminal 237, as well as the connection resistance between the busbar 330 and the negative outer terminal 247.

[0107] Additionally, in the second example, as in the first example, each of the spaces S is a closed space defined by the terminal recess 237f of the positive outer terminal 237 and the front surface 183c of the insulating part 183, which closes the opening of the terminal recess 237f, or by the terminal recess 247f of the negative outer terminal 247 and the front surface 183c of the further insulating part 183, which closes the opening of the terminal recess 247f (see Fig. 17) These spaces allow for the capture or collection of at least some of the foreign matter, such as spatter, generated during laser welding. Therefore, in step T4 (the laser welding step), the amount of foreign matter, such as spatter, that is scattered outwards can be reduced, leading to a reduction in the contamination of the external environment.

[0108] Since the busbar 330 is welded to the outer terminals (the positive outer terminal 237 and the negative outer terminal 247) of the cells 200 arranged adjacent in series DL, as described above, the cells 200 adjacent in series DL are electrically connected in series by the busbar 330. Consequently, several cells 200, forming the cell stack 320, are electrically connected in series. As described above, a battery pack 301 is produced in the second example (see Fig. 1).

[0109] In the second example, as described above, in step T3 (the arrangement step) the busbar 330 is arranged on the front surfaces of the outer terminals (i.e., on the front surface 237c of the positive outer terminal 237 and the front surface 247c of the negative outer terminal 247) so that the terminal projection sections of the outer terminals (i.e., the terminal projection section 237h of the positive outer terminal 237 and the terminal projection section 247h of the negative outer terminal 247) fit into the busbar recesses 330f of the busbar 330. Therefore, even if the outer terminals of two cells 200 arranged adjacent in the series direction DL, i.e., the positive outer terminal 237 and the negative outer terminal 247, have different heights, as shown in Fig.As shown in Figure 18, the contact area between the outer terminal (the positive outer terminal 237 or the negative outer terminal 247) and the busbar 330 is largely covered. This configuration can reduce the connection resistance between the busbar 330 and the outer terminal (i.e., the positive outer terminal 237 or the negative outer terminal 247).

[0110] The present revelation is described according to the first and second examples, but is not limited to them. However, the present revelation is not limited to the examples above, but can be embodied in other specific forms without deviating from its core.

[0111] For example, in the first example, each space S is a closed space. Alternatively, space S can be an open space defined by the terminal recess 137f of the positive outer terminal 137 or the terminal recess 147f of the negative outer terminal 147, the opening of which is not closed by the front surface 183c of the insulating parts 183. The same applies to the second example.

[0112] In the first example, the positive outer terminal 137 encompasses the terminal recess 137f, and the negative outer terminal 147 encompasses the terminal recess 147f, and the front surface 183c of the flat, plate-shaped insulating part 183 closes the openings of the terminal recesses 137 and 147, thereby forming the space S. Alternatively, the insulating part can include recesses, and the rear surface of the flat, plate-shaped positive outer terminal and the rear surface of the flat, plate-shaped negative outer terminal close the openings of the recesses of the insulating part, thereby forming a space. Reference symbol list 1,301 battery pack 20,320 cell stacks 30, 330 busbar 30c, 330c Front surface 30g, 330g Opposite section 40, 340 Welded section 41, 341 Melting metal section 100, 200 cells 110 cell casings 110c Front surface 130, 230 Positive terminal element (electrode terminal element) 137, 237 Positive outer terminal (External terminal) 137c, 237c Front surface 137d, 237d Rear surface 137f, 237f Terminal recess 137g, 237g Separate section 237h, 247h Clamping projection section 140, 240 Negative terminal element (electrode terminal element) 147, 247 Negative outer terminal (External terminal) 147c, 247c Front surface 147d, 247d Rear surface 147f, 247f Terminal recess 147g, 247g Separate section 180 Ester Insulator 183 Insulating part 183c Front surface 330f busbar recess DT Thickness direction DL series direction LB laser beam S room S1, T1 Cell preparation step S3, T3 Arrangement step S4, T4 laser welding step

Claims

[1] Method for manufacturing a battery pack (1; 301) wherein the battery pack comprises: several cells (100; 200), each comprising an outer terminal (137, 147; 237, 247); and a busbar (30; 330) made of a plate-shaped metal, wherein the busbar is arranged on a front surface (137c, 147c; 237c, 247c) of the outer terminal (137, 147; 237, 247c) and welded to it (137c, 147c; 237c, 247c), wherein Each of the cells (100; 200) comprises: a metal cell casing (110); the outer clamp (137, 147; 237, 247) made of plate-shaped metal and arranged on an outside of the cell housing (110); and an insulating part (183) made of a resin having electrical insulating properties and arranged between a front surface (110c) of the cell housing (110) and a rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247) to electrically insulate the cell housing (110) and the outer terminal (137, 147; 237, 247) from each other, the battery pack (1; 301) comprising a welded section (40; 340) in which the outer terminal (137, 147; 237, 247) and the busbar (30; 330) are welded together, the welded section (40; 340) being oriented in a thickness direction (DT) of the outer terminal (137, 147; 237, 247) extends from a front surface (30c; 330c) of the busbar (30; 330) towards the rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247), and the welded section (40; 340), separated by a space (S) in the thickness direction (DT) of the outer clamp (137, 147; 237, 247), is arranged at a distance from the insulating part (183), the procedure comprises the following steps: a cell preparation step (S1; T1) for preparing several of the cells (100; 200), each comprising the outer clamp (137, 147; 237, 247) which includes a separate section (137g, 147g; 237g, 247g) to be arranged through the space (S) between the outer clamp (137, 147; 237, 247) and the insulating part (183) in the thickness direction (DT) at a distance from the insulating part (183); an arrangement step (S3; T3) for arranging the busbar (30; 330) on the front surface (137c, 147c; 237c, 247c) of the outer terminal (137, 147; 237, 247) of each of the prepared cells (100; 200), such that a portion of the busbar (30; 330) becomes an opposing section (30g; 330g) which is arranged in the thickness direction (DT) of the outer terminal (137, 147; 237, 247) opposite the space (S) by placing the separate section (137g, 147g; 237g, 247g) of the outer terminal (137, 147; 237, 247) between it; and a laser welding step (S4; T4) for laser welding the opposite section (30g; 330g) of the busbar (30; 330) to the separate section (137g, 147g; 237g, 247g) of the outer terminal (137, 147; 237, 247), and wherein the laser welding step comprises projecting a laser beam (LB) from one side of the front surface (30c; 330c) of the busbar (30; 330) in the direction of space (S) in the thickness direction (DT) of the outer clamp (137; 237) to melt the opposite section (30g; 330g) of the busbar (30; 330) and the separate section (137g, 147g; 237g, 247g) of the outer clamp (137, 147; 237, 247) and thus forming the welded section (40; 340) in which the separate section (137g, 147g; 237g, 247g) and the opposite section (30g; 330g) are welded together, characterized by , that the outer clamp (237, 247) comprises a clamp projection section (237h, 247h) that projects from the front surface (237c, 247c), the busbar (330) includes a concave busbar recess (330f) through which the terminal projection section (237h, 247h) can be fitted, and The assembly step comprises arranging the busbar (330) on the front surface (237c, 247c) of the outer terminal (237, 247) while fitting the terminal projection section (237h, 247h) into the busbar recess (330f). [2] Method for manufacturing a battery pack (1; 301) according to claim 1, wherein the outer clamp (137, 147; 237, 247) comprises a clamping recess (137f, 147f; 237f, 247f) with an opening in the rear surface (137d; 237d) of the outer clamp (137, 147; 237, 247), the terminal recess (147f; 247f) is designed such that it is recessed in a direction away from a front surface (183c) of the insulating parts (183), the front surface (183c) being opposite the rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247), and the space (S) is a closed space (S) defined by the terminal recess (137f, 147f; 237f, 247f) of the outer terminal (137, 147; 237, 247) and the front surface (183c) of the insulating part (183) which closes the opening of the terminal recess (137f, 147f; 237f, 247f). [3] Method for manufacturing a battery pack (1; 301) according to claim 1 or 2, wherein the laser welding step (S4; T4) produces a molten metal section by irradiation with the laser beam (LB) extending from the front surface (30c; 330c) of the busbar (30; 330) to the space (S) to form the welded section (40; 340) extending from a front surface of the opposite section (30g; 330g) of the busbar (30; 330) to a rear surface of the separate section (137g, 147g; 237g, 247g) of the outer terminal (137, 147; 237, 247). [4] Battery pack (1; 301) comprising: several cells (100; 200), each comprising an outer terminal (137, 147; 237, 247); and a busbar (30; 330) made of a plate-shaped metal, wherein the busbar is arranged on a front surface (137c, 147c; 237c, 247c) of the outer terminal (137, 147; 237, 247c) and welded to it (137c, 147c; 237c, 247c), characterized by , that each of the cells comprises (100; 200): a metal cell casing (110); the outer clamp (137, 147; 237, 247) made of plate-shaped metal and arranged on an outside of the cell housing (110); and an insulating part (183) made of a resin having electrical insulating properties and arranged between a front surface (110c) of the cell housing (110) and a rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247) to electrically insulate the cell housing (110) and the outer terminal (137, 147; 237, 247) from each other, the battery pack (1; 301) comprising a welded section (40; 340) in which the outer terminal (137, 147; 237, 247) and the busbar (30; 330) are welded together, the welded section (40; 340) being oriented in a thickness direction (DT) of the outer terminal (137, 147; 237, 247) extends from a front surface (30c; 330c) of the busbar (30; 330) towards the rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247), and the welded section (40; 340), separated by a space (S) in the thickness direction (DT) of the outer clamp (137, 147; 237, 247), is arranged at a distance from the insulating part (183), characterized by , that the outer clamp (237, 247) comprises a clamp projection section (237h, 247h) that projects from the front surface (237c, 247c), the busbar (330) includes a concave busbar recess (330f) through which the terminal projection section (237h, 247h) can be fitted, and the outer terminal (237, 247) and the busbar (330) are welded together, while the terminal projection section (237h, 247h) is fitted into the busbar recess (330f). [5] Battery pack (1; 301) according to claim 4, wherein the outer clamp (137, 147; 237, 247) comprises a clamp recess (137f, 147f; 237f, 247f) with an opening in the rear surface (137d, 147d; 237d, 247d) of the outer clamp (137, 147; 237, 247), the terminal recess (147f; 247f) is recessed in a direction away from a front surface (183c) of the insulating part (183), the front surface (183c) being opposite the rear surface (137d, 147d; 237d, 247d) of the outer terminal (137, 147; 237, 247), and the space (S) is a closed space (S) defined by the terminal recess (137f, 147f; 237f, 247f) of the outer terminal (137, 147; 237, 247) and the front surface (183c) of the insulating part (183) which closes the opening of the terminal recess (137f, 147f; 237f, 247f). [6] Battery pack (1; 301) according to claim 4 or 5, wherein the outer terminal (137, 147; 237, 247) comprises a separate section (137g, 147g; 237g, 247g) which, through the space (S) between the outer terminal (137, 147; 237, 247) and the insulating part (183), is arranged in the thickness direction (DT) at a distance from the insulating part (183), the busbar (30; 330) comprises an opposing section (30g; 330g) opposite the space (S) by placing the separate section (137g, 147g; 237g, 247g) of the outer terminal (137, 147; 237, 247) in the thickness direction (DT) between them, and the welded section (40; 340) to which the separate section (137g, 147g; 237g, 247g) and the opposite section (30g; 330g) are welded together extends from a front surface of the opposite section (30g; 330g) to a rear surface of the separate section (137g, 147g; 237g, 247g).

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