JP2015011785A - Power storage device and method of manufacturing power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device in which formation of a blowhole can be suppressed, and to provide a method for manufacturing a power storage device.SOLUTION: A power storage device includes a power storage element 1 including an external terminal 4 having a first connection surface 4a, a bus bar 6 having a second connection surface 8a(6a) superposed on the first connection surface, and a weld zone 9 formed across the external terminal and the bus bar in an area where the first connection surface and second connection surface face each other. A gap where the first and second connection surfaces are formed, while spaced apart from each other, is provided at least around the weld zone in any one of the first and second connection surfaces.

Description

  The present invention relates to a power storage device including a power storage element having an external terminal and a bus bar, and a method for manufacturing the power storage device.

  Generally, as shown in FIG. 13, the power storage device includes a power storage element 1 (battery cell 1) including an external terminal 4 and a bus bar 6 electrically connected to the external terminal 4. In this type of power storage device, there is one in which the external terminal 4 of the power storage element 1 and the bus bar 6 are connected by welding. In this case, the external terminal 4 has a planar first connection surface 4a. On the other hand, the bus bar 6 has a planar second connection surface 6a that is superimposed so as to be in close contact with the first connection surface 4a. The external terminal 4 and the bus bar 6 are welded in a state where the first connection surface 4a and the second connection surface 6a are overlapped with each other. That is, the welded portion 9 in which the external terminal 4 and the bus bar 6 are partially melted is formed in a region where the first connection surface 4a and the second connection surface 6a face each other. Thereby, the electrical storage element 1 and the bus bar 6 are connected so as to be conductive (see, for example, Patent Document 1).

  By the way, as described above, the external terminal 4 and the bus bar 6 are partially welded in a state where the first connection surface 4a of the external terminal 4 and the second connection surface 6a of the bus bar 6 are in close contact with each other. As a result, a hollow blowhole (gas reservoir) B tends to be formed in the vicinity of the boundary between the first connection surface 4 a and the second connection surface 6 a around the welded portion 9. When the blow hole B is generated in the welded portion, the joint width between the external terminal 4 and the bus bar 6 is narrowed, so that the welding strength is reduced as compared with the case where the blow hole B is not generated.

  Further, when the power storage element 1 or the bus bar 6 vibrates or the bus bar 6 is bent due to positional adjustment, stress concentration occurs around the welded portion 9. When the welding strength is reduced due to the formation of the blow hole B, a part of the welded portion 9 may be damaged by the stress concentrated around the welded portion 9. Therefore, in this type of power storage device, there is a possibility that the welded portion 9 may be damaged due to stress concentration, and the connection rigidity between the external terminal 4 and the bus bar 6 may not be ensured.

JP 2012-125829 A

  Then, this invention makes it a subject to provide the electrical storage apparatus which can suppress formation of a blowhole, and the manufacturing method of this electrical storage apparatus in view of this situation.

  A power storage device according to the present invention includes a power storage element including an external terminal having a first connection surface, a bus bar having a second connection surface superimposed on the first connection surface, and the first connection surface and the second connection surface are mutually connected. A welded portion formed between the external terminal and the bus bar in the opposing region, and at least one of the first connecting surface and the second connecting surface has at least a first connecting surface around the welded portion. And a second connecting surface are formed so as to be separated from each other.

  According to such a configuration, the welded portion is formed by allowing the gas generated when the bus bar is welded to the external terminal to escape to the gap portion. That is, in the power storage device according to the present invention, the gas generated during welding is not confined between the first connection surface and the second connection surface, and the formation of blow holes is suppressed. Therefore, it is suppressed that the welding width of a welding part becomes narrow. Therefore, even when an external force is applied to the external terminal or the bus bar and stress is concentrated near the boundary between the first connection surface and the second connection surface in the welded portion, the welded portion is not easily damaged. Therefore, the connection rigidity between the bus bar and the external terminal is ensured.

  In this case, it is preferable that the first connection surface and the second connection surface are provided with alignment portions that are in close contact with each other outside the gap portion.

  According to such a configuration, the first connecting surface and the second connecting surface maintain a constant separation distance because the first connecting surface and the second connecting surface are in close contact with each other. Positioned in the state. Accordingly, the separation distance between the first connection surface and the second connection surface is an appropriate distance, and a gap portion that can smoothly discharge the gas generated during welding is formed between the first connection surface and the second connection surface. The Therefore, in the power storage device according to the present invention, the generation of blow holes is suppressed without being confined near the boundary between the first connection surface and the second connection surface where the gas generated during welding is in close contact.

  Furthermore, in this case, it is preferable that at least one of the first connection surface and the second connection surface has a recess including a welded portion.

  According to this configuration, the first connection surface of the external terminal and the second connection surface of the bus bar are overlapped, so that the raised portion of the recess is in close contact with the first connection surface or the second connection surface facing each other. The opened portion of the recess is closed by the first connection surface or the second connection surface facing each other. The first connection surface and the second connection surface in the region where the recess is blocked are spaced apart. Thus, even if the external terminal and the bus bar are not processed into a complicated shape / structure, only the recess is formed, and the first connection surface and the second connection surface are at an appropriate distance. A separated power storage device is obtained.

  As another aspect of the power storage device according to the present invention, the bus bar may have a thin portion that is thinner than the thickness of the alignment portion in a region where the gap portion is formed.

  According to such a configuration, the power storage device is welded from the thin wall portion to the first connection surface with lower energy than in the case of welding a bus bar having the same thickness as the thickness of the alignment portion.

  Moreover, as another aspect of the power storage device according to the present invention, the distance between the first connection surface and the second connection surface around the welded portion can be 10 μm or more.

  According to such a configuration, the gas generated during welding can surely escape to the gap between the first connection surface and the second connection surface, and the power storage device in which the formation of blow holes is suppressed is obtained.

  In this case, the separation distance between the first connection surface and the second connection surface around the welded portion can be less than 50 μm.

  According to such a configuration, since there is a weld portion in which a large crack is not formed, even in a power storage device in which the first connection surface and the second connection surface are separated, the connection rigidity between the external terminal and the bus bar is high. It is kept.

  The method for manufacturing a power storage device according to the present invention is such that the first connection surface of the external terminal included in the power storage element and the second connection surface of the bus bar are separated from each other in a region facing each other. A bus bar arranging step of arranging the connection surface on the first connection surface of the external terminal, and a region where the first connection surface of the external terminal and the second connection surface of the bus bar are spaced apart from each other, and the external terminal A welding process for forming a welded portion in which the bus bar is partially melted.

  According to this structure, the bus bar arranged on the first connection surface while being separated from the second connection surface in the bus bar arrangement step is welded in the welding step. The gas generated when the bus bar is welded to the external terminal escapes to the gap between the first connection surface and the second connection surface. That is, the gas generated during welding is not confined between the first connection surface and the second connection surface. Therefore, the formation of blowholes is suppressed and the joint width of the welded portion is suppressed from being narrowed. Therefore, even when an external force is applied to the external terminal or the bus bar and the stress is concentrated near the boundary between the first connection surface and the second connection surface in the welded portion, the power storage device having the welded portion that is not easily damaged Manufactured. Furthermore, this power storage device ensures the connection rigidity between the bus bar and the external terminal.

  Here, as one aspect of the method for manufacturing the power storage device according to the present invention, the bus bar arrangement step is such that the first connection surface and the second connection surface are partially separated in a region facing each other. The second connection surface of the bus bar can be brought into close contact with the first connection surface of the external terminal.

  According to this configuration, as the second connection surface of the bus bar comes into close contact with the first connection surface of the external terminal, a partially spaced gap is formed between the first connection surface and the second connection surface. Is done. The first connection surface and the second connection surface are positioned with respect to each other in a state where the separation distance between the first connection surface and the second connection surface in the gap is kept constant. Therefore, the separation distance between the first connection surface and the second connection surface is maintained at an appropriate distance, and the generation of blow holes is reliably suppressed.

  In this case, there is provided a recess forming step of forming a recess in a region which is at least one of the first connection surface of the external terminal and the second connection surface of the bus bar and faces each other after the bus bar arranging step. It is preferable to do.

  According to such a configuration, the recess formed in the recess forming step is a first connection in which the raised portions of the recess face each other by overlapping the first connection surface of the external terminal and the second connection surface of the bus bar. The first connection surface or the second connection surface that is in close contact with the surface or the second connection surface and is open to the recesses is closed. The first connection surface and the second connection surface in the region where the recess is blocked are spaced apart. Thus, even if the external terminal and the bus bar are not processed into a complicated shape and structure, the first connection surface and the second connection surface are separated by an appropriate distance.

  In this case, it is preferable that the recess forming step is a press working step.

  According to such a configuration, the recess is formed with high accuracy in accordance with a region where the external terminal and the bus bar are welded.

  Further, as another aspect of the method for manufacturing the power storage device according to the present invention, the second connection surface in which the thickness of the bus bar in the region on the second connection surface that is separated from the first connection surface by the bus bar arrangement step is in close contact with the first connection surface. A thin portion forming step of forming a thin portion thinner than the thickness of the bus bar in the upper region can be provided.

  According to this structure, the bus bar which can be welded from a thin part to a 1st connection surface with low energy compared with the case where the bus bar of the same thickness as the thickness of a position alignment part is welded in a welding process is formed.

  Further, as another aspect of the method for manufacturing the power storage device according to the present invention, the bus bar placement step includes a second bus bar second step so that the distance between the first connection surface and the second connection surface around the welded portion is 10 μm or more. The connection surface can be overlaid on the first connection surface of the external terminal.

  According to this configuration, gas generated during welding in the welding process can surely escape to the gap between the first connection surface and the second connection surface, and the formation of blow holes is suppressed.

  In this case, in the bus bar arrangement step, the second connection surface of the bus bar is superimposed on the first connection surface of the external terminal so that the distance between the first connection surface and the second connection surface around the welded portion is less than 50 μm. It is preferable to do so.

  According to such a configuration, even if the bus bar is welded to the external terminal by separating the first connection surface and the second connection surface in the welding process, the welded portion is cracked along with the welding between the bus bar and the external terminal. A power storage device that is difficult to occur and maintains the connection rigidity between the external terminal and the bus bar is manufactured.

  As described above, according to the power storage device and the method for manufacturing the power storage device according to the present invention, there is an excellent effect that the formation of blowholes can be suppressed.

FIG. 1 is an overall perspective view of a battery module according to an embodiment of the present invention. FIG. 2 is a plan view of the battery module according to the embodiment. FIG. 3 is an enlarged plan view in which a part of the battery module according to the embodiment is enlarged. 4A is a cross-sectional view taken along line AA in FIG. 3 and is a cross-sectional view showing a state before welding. FIG. 4B is an enlarged view of a main part of part B in FIG. 4A. FIG. 5 is a cross-sectional view taken along line AA of FIG. 3 and shows a state after welding. 6 is a cross-sectional view of a battery module according to another embodiment of the present invention cut at the same position as the line AA shown in FIG. 3, and is a cross-sectional view showing a state after welding. 7 is a cross-sectional view of a battery module according to another embodiment of the present invention cut at the same position as the line AA shown in FIG. 3, and is a cross-sectional view showing a state after welding. FIG. 8 is an enlarged plan view in which a part of a battery module according to still another embodiment of the present invention is enlarged. FIG. 9 is a cross-sectional view taken along the line CC of FIG. 8 and shows a state after welding. FIG. 10 is an enlarged plan view in which a part of a battery module according to still another embodiment of the present invention is enlarged. FIG. 11 is a cross-sectional view taken along line DD of FIG. 10 and is a cross-sectional view showing a state after welding. 12 is a cross-sectional view of a battery module according to still another embodiment of the present invention cut at the same position as the line AA shown in FIG. 3, and is a cross-sectional view showing a state before welding. FIG. 13 is a main part enlarged view for explaining a welded portion formed on the external terminal and the bus bar when the first connection surface of the external terminal and the second connection surface of the bus bar are overlapped and welded. .

  Hereinafter, a battery module which is an embodiment of a power storage device according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the battery module according to the present embodiment includes a plurality of battery cells 1 (power storage elements) and a plurality of bus bars 6. The bus bar 6 is electrically connected to the battery cell 1.

  Each of the plurality of battery cells 1 has the same shape and the same structure. Accordingly, the structure of the single battery cell 1 will be described below.

  The battery cell 1 has an electrode body (not shown) and a case 2 in which the electrode body is accommodated. 3, 4A and 4B, the battery cell 1 is attached to the case 2 while being insulated from the case 2 by the external gasket 3 disposed on the outer surface of the case 2. The external terminal 4 is provided. The battery cell 1 includes a current collector 5 that is electrically connected to the external terminal 4.

  In the battery cell 1 according to this embodiment, a pair of external gaskets 3 are arranged on the outer surface of the case 2, and one external terminal 4 is attached to each of the pair of external gaskets 3. That is, the battery cell 1 has a pair of external gaskets 3 and a pair of external terminals 4.

  As shown in FIG. 4A, the case 2 includes a case main body 2a having an opening, and a lid plate 2b that closes and seals the opening of the case main body 2a.

  As shown in FIG. 2, the case body 2a is formed in a bottomed rectangular tube shape that is flat in the width direction. Accordingly, the cover plate 2b is formed in a rectangular shape corresponding to the opening of the case body 2a.

  A pair of through holes (not shown) are formed in the lid plate 2b. One through hole is formed at one end of the lid plate 2b in the longitudinal direction. And the other through-hole is formed in the other end part in the longitudinal direction of the cover plate 2b.

  Each external gasket 3 is formed of an insulating material such as resin. Each external gasket 3 is formed with a through hole (not shown). And each external gasket 3 is arrange | positioned at the outer surface of the cover board 2b, as shown to FIG. 4A and 4B. This will be described more specifically. One external gasket 3 is arranged so that the position of the through hole of the one external gasket 3 corresponds to the position of the one through hole of the cover plate 2b. The other external gasket 3 is arranged such that the position of the through hole of the other external gasket 3 corresponds to the position of the other through hole of the cover plate 2b. Each external gasket 3 is formed in a rectangular shape in plan view (a rectangular shape having a length in the longitudinal direction of the cover plate 2b).

  Of the pair of external terminals 4, one external terminal 4 is for the positive electrode, and the other external terminal 4 is for the negative electrode. The external terminal 4 for positive electrode (one) is attached to one end portion in the longitudinal direction of the cover plate 2b. The external terminal 4 for the negative electrode (the other) is attached to the other end portion in the longitudinal direction of the lid plate 2b. Each external terminal 4 has a first connection surface 4a to which a bus bar 6 (a second connection surface 6a of the bus bar 6 described later) is connected.

  This will be described more specifically. One external terminal 4 has a plate-like portion 4b placed on the external gasket 3 (one external gasket 3). The plate-like portion 4b is formed of an aluminum-based metal material such as aluminum or an aluminum alloy. In addition, the plate-like portion 4b is formed in a rectangular shape in plan view (a rectangular shape that is long in the longitudinal direction of the lid plate 2b). And the plate-shaped part 4b has the 1st surface to which the bus bar 6 is connected, and the 2nd surface on the opposite side to this 1st surface. Therefore, in one external terminal 4, the first surface of the plate-like portion 4b constitutes the first connection surface 4a.

  One external terminal 4 further has a caulking portion (not numbered) for fixing the plate-like portion 4b to the outer surface of the case 2 (lid plate 2b). The caulking portion extends from the plate-like portion 4b. The caulking portion is made of an aluminum-based metal material such as aluminum or an aluminum alloy. In one of the external terminals 4, the caulking portion is caulked in a state of being inserted into the through hole of the cover plate 2 b, the through hole of the external gasket 3, and the through hole of the current collector 5. It is electrically connected to the body 5.

  The other external terminal 4 has a plate-like portion 4b placed on the external gasket 3 (the other external gasket 3). The plate-like portion 4b is formed of an aluminum-based metal material such as aluminum or an aluminum alloy. In addition, the plate-like portion 4b is formed in a rectangular shape in plan view (a rectangular shape that is long in the longitudinal direction of the lid plate 2b). And the plate-shaped part 4b has the 1st surface to which the bus bar 6 is connected, and the 2nd surface on the opposite side to this 1st surface. Therefore, in the other external terminal 4, the 1st surface of the plate-shaped part 4b comprises the 1st connection surface 4a.

  The other external terminal 4 further includes a caulking portion (not numbered) for fixing the plate-like portion 4b to the outer surface of the case 2 (lid plate 2b). The caulking portion is formed of a copper-based metal material such as copper or a copper alloy. In the other external terminal 4, the caulking portion is caulked while being inserted into the through hole of the plate-like portion 4 b, the through hole of the cover plate 2 b, the through hole of the external gasket 3, and the through hole of the current collector 5. Furthermore, it is electrically connected to the current collector 5.

  The first connection surface 4a is formed in a planar shape. The bus bar 6 (the connection surface 8a) is superimposed on the first connection surface 4a. The first connection surface 4 a of one external terminal 4 and the first connection surface 4 a of the other external terminal 4 are located above the external gasket 3. The first connection surface 4a of one external terminal 4 and the first connection surface 4a of the other external terminal 4 are at the same height level with respect to the outer surface of the cover plate 2b. The first connection surface 4 a becomes an alignment portion that comes into close contact with the bus bar 6 when the plate-like portion 4 b is superimposed on the bus bar 6.

  Here, returning to FIGS. 1 and 2, the arrangement of the plurality of battery cells 1 in the battery module will be described. The plurality of battery cells 1 are arranged in a line. The plurality of battery cells 1 are arranged in the short direction of the cover plate 2b. In the present embodiment, ten battery cells 1 are arranged. In the following description, the short direction of the cover plate 2b is defined as the arrangement direction.

  A pair of adjacent battery cells 1 are arranged such that the polarities of the external terminals 4 adjacent in the arrangement direction are opposite. The external terminals 4 adjacent to each other in the arrangement direction are connected by a bus bar 6. More specifically, in the adjacent battery cell 1, the first connection surface 4 a of the external terminal 4 for the positive electrode of one battery cell 1 and the first connection of the external terminal 4 for the negative electrode of the other battery cell 1. The surface 4 a is close to each other, and these external terminals 4 are connected by a bus bar 6. Thereby, all the battery cells 1 constitute one battery connected in series.

  Of the plurality of battery cells 1 connected in series, one of the external terminals 4 of the battery cell 1 located at one end and one of the external terminals 4 of the battery cell 1 located at the other end are respectively externally connected. A bus bar (not shown) is connected. Another battery module or another device is connected to the bus bar.

  Next, the bus bar 6 will be described with reference to FIGS. In the present embodiment, the bus bars 6 that connect the external terminals 4 have the same shape and the same structure. Accordingly, the structure of the single bus bar 6 will be described below.

  The bus bar 6 is formed in a flat plate shape that is rectangular in plan view. The bus bar 6 is formed of a plate material made of aluminum or an aluminum alloy metal material. The bus bar 6 also has a second connection surface 6a that overlaps the first connection surface 4a. And the bus bar 6 has the welding surface 6b on the opposite side to the 2nd connection surface 6a.

  This will be described more specifically. The bus bar 6 includes a main body portion 7 and a pair of connection portions 8 connected to both ends of the main body portion 7. In the bus bar 6, the main body portion 7 and the pair of connection portions 8 are integrally formed.

  Each connection portion 8 is connected to an external terminal 4 of a different storage element 1. Each connecting portion 8 has a first flat surface 8a that overlaps the first connecting surface 4a and a second flat surface 8f opposite to the second connecting surface 6a. Therefore, the first plane 8 a of each connection portion 8 is included in the second connection surface 6 a of the bus bar 6, and the second plane 8 f of each connection portion 8 is included in the welding surface 6 b of the bus bar 6.

  The second connection surface 6 a has a plurality of first recesses 8 b that include the welded portion 9. Two first recesses 8b are provided along the longitudinal direction of the cover plate 2b. Each first recess 8b is formed by denting the second connection surface 6a toward the welding surface 6b. Each first recess 8b is formed in a cylindrical shape. Each first recess 8b has a gap 8c where the first connection surface 4a and the second connection surface 6a are separated from each other at least around the welded portion 9, and a position where the first connection surface 4a and the second connection surface 6a are in close contact with each other. 8d. The positioning portion 8d is disposed outside the gap portion 8c.

  The gap 8c is a portion that is recessed from the second connection surface 6a toward the welding surface 6b. The cross-sectional shape of the gap portion 8c cut by a plane parallel to the second connection surface 6a is larger than the cross-sectional shape of the welded portion 9 cut by the same surface. The gap 8c is formed flat. The distance between the gap 8c and the alignment portion 8d in the thickness direction of the bus bar 6 is substantially constant. The gap 8c is at a distance of 10 μm or more in the thickness direction of the bus bar 6 from the alignment portion 8d. Further, the gap 8c is at a distance of less than 50 μm in the thickness direction of the bus bar 6 from the alignment portion 8d. The gap portion 8c is preferably at a distance of 20 μm or less in the thickness direction of the bus bar 6 from the alignment portion 8d.

  The alignment portion 8 d is formed in the same plane as the first connection surface 4 a of the external terminal 4. Therefore, the positioning portion 8 d comes into surface contact with the first connection surface 4 a of the external terminal 4. The alignment portion 8d is formed in a planar shape substantially parallel to the gap portion 8c. The positioning portion 8d of the bus bar 6 positions the first connection surface 4a so that the separation distance X1 between the first connection surface 4a and the second connection surface 6a in the gap portion 8c is kept constant.

  The weld surface 6 b has a second recess 8 e that includes the weld 9. The 2nd recessed part 8e is arrange | positioned in the position corresponding to the position of the 1st recessed part 8b on the 2nd connection surface 6a. That is, the second recess 8e is provided on the welding surface 6b on the opposite side of the first recess 8b. The shape of the second recess 8e is the same as that of the first recess 8b.

  In the bus bar 6, the second recessed portion 8 e is formed, so that a thin portion 8 g thinner than the thickness of the alignment portion 8 d is formed in a region where the gap portion 8 c is formed. The thin portion 8g according to the present embodiment is formed by the first recess 8b and the second recess 8e. The depth of the second recess 8e in the thickness direction is set so that the distance from the welding surface 6b of the bus bar 6 to the second connection surface 6a is an appropriate thickness for melting the bus bar 6. In the present embodiment, the distance between the first recess 8b and the second recess 8e in the thickness direction is set to be equal to or less than an appropriate thickness for melting the bus bar 6. The thin portion 8g is formed thin so that the laser output does not become too high. In addition, by forming the thin portion 8g thin, the welding time is shortened and the cost for welding can be kept low.

  As shown in FIG. 5, in the battery module, as described above, the external terminal 4 and the bus bar 6 are connected by welding (in this embodiment, laser welding). And the welding part 9 is formed over the external terminal 4 and the bus bar 6 in the area | region where the 1st connection surface 4a of the external terminal 4 and the 2nd connection surface 6a of the bus bar 6 oppose each other.

  The welded portion 9 is formed in an annular shape in plan view on the weld surface 6b. This will be specifically described. The welded portion 9 is formed in an annular shape in plan view. Therefore, even if an external force acts on the bus bar 6 from various directions, the stress can be prevented from concentrating on the welded portion 9. Therefore, the strength of the welded portion can be increased. The welded portion 9 is formed from the welded surface 6 b of the bus bar 6 to the first connection surface 4 a of the external terminal 4. The cross-sectional area of the welded portion 9 in the thickness direction decreases as it goes from the welding surface 6b to the first connection surface 4a. That is, the cross-sectional shape of the welded portion 9 in the thickness direction is formed in an inverted triangular shape or an inverted trapezoidal shape.

  The power storage device according to this embodiment is as described above. Then, the manufacturing method of a battery module is demonstrated, referring an accompanying drawing.

  First, the some battery cell 1 is arrange | positioned in the same parallel state as the time of completion on conveyance apparatuses, such as a belt conveyor. And the several battery cell 1 of this state is conveyed by the conveying apparatus to the operation area | region (henceforth a welding area) of a welding apparatus. In the present embodiment, the welding apparatus is a laser welding apparatus. When the plurality of battery cells 1 reach the welding area, the automatic bus bar supply device arranged adjacent to the welding device receives the bus bar 6 by a holding body configured to hold the bus bar 6. And the bus bar automatic supply apparatus arrange | positions the bus bar 6 so that it may straddle between a pair of external terminals 4 of the adjacent battery cell 1, as shown in FIG.1 and FIG.2.

  Specifically, as shown in FIG. 5, the second connection surface 6 a (the alignment portion 8 d) of the bus bar 6 is placed on the first connection surface 4 a of the external terminal 4, and the second connection surface 6 a is Close contact is made on one connection surface 4a (bus bar arrangement step). At this time, the first connection surface 4a of the external terminal 4 and the second connection surface 6a of the bus bar 6 are in a state of being partially separated in a region facing each other. The separation distance X1 between the first connection surface 4a and the second connection surface 6a around the welded portion 9 is set to 10 μm or more and less than 50 μm.

  The laser beam L is emitted from the welding head H in a state where the holding body presses the bus bar 6 against the external terminal 4. The welding head H emits a laser beam L to the bottom surface of the second recess 8e. The welding head H moves the laser light L along the edge of the second recess 8 e of the bus bar 6. And the mutually spaced-apart area | region of the 1st connection surface 4a of the external terminal 4 and the 2nd connection surface 6a of the bus bar 6 is partially welded. In this way, a welded portion 9 in which the external terminal 4 and the bus bar 6 are partially melted is formed (welding process).

  Thus, the thin-walled portion 8g of the second connection surface 6a of the bus bar 6 and the first connection surface 4a of the external terminal 4 are welded. By partially welding the mutually separated regions of the first connection surface 4a and the second connection surface 6a, at least the periphery of the welded portion 9 is separated. Therefore, when the bus bar 6 is welded to the external terminal 4, the gas contained in the molten metal escapes to the gap portion 8c, so that the formation of blow holes is suppressed. Therefore, it is suppressed that the welding width of a welding part becomes narrow. Therefore, even if an external force is applied to the external terminal 4 or the bus bar 6, the stress is less likely to concentrate on the welded portion 9 and is not easily damaged. And the connection rigidity of the external terminal 4 and the bus bar 6 is ensured.

  Then, the bus bar 6 is electrically and mechanically connected to the external terminal 4 of the battery cell 1 by the welding device welding the bus bar 6 and the external terminal 4. In this way, a large capacity battery (battery module) is completed.

  The bus bar 6 used in the present embodiment is formed by forming the first recess 8b in the second connection surface 6a that faces the first connection surface 4a before the bus bar arranging step (recess forming step). Manufactured. The first recess 8b is formed by press working. Simultaneously with this recess forming step, a second recess 8e is also formed. Therefore, the thin part 8g thinner than the surrounding thickness is formed in the area | region including the welding part 9 formed after a welding process by this 1st recessed part 8b and the 2nd recessed part 8e (thin part forming process). That is, the thin portion 8g is also formed by pressing.

  As described above, according to the battery module of the present embodiment, the welded portion 9 is formed by letting the gas generated when the bus bar 6 is welded to the external terminal 4 escape to the gap portion 8c. That is, in the battery module according to the present embodiment, the gas generated during welding is not confined between the first connection surface 4a and the second connection surface 6a, and the formation of blow holes is suppressed. Therefore, it is suppressed that the joining width of the welding part 9 becomes narrow. Therefore, even if an external force is applied to the external terminal 4 or the bus bar 6, the welded portion 9 can be easily formed even when stress is concentrated near the boundary between the first connecting surface 4 a and the second connecting surface 6 a in the welded portion 9. Does not break. Therefore, the connection rigidity between the bus bar 6 and the external terminal 4 is ensured.

  Further, a gap 8c (the first recess 8b) is provided in a limited region including the weld 9. Therefore, a decrease in the contact area where the external terminal 4 and the bus bar 6 are in contact with each other can be minimized. Therefore, the electrical resistance at the contact portion between the external terminal 4 and the bus bar 6 does not increase greatly from the electrical resistance when the gap 8c is not provided.

  Further, since the first connection surface (positioning portion) 4a and the positioning portion 8d of the second connection surface 6a are in close contact with each other, the first connection surface 4a and the second connection surface 6a have a separation distance X1. Positioning is performed in a constant state. Accordingly, the separation distance X1 between the first connection surface 4a and the second connection surface 6a is an appropriate distance, and the gap portion 8c that can smoothly discharge the gas generated during welding is formed in the first connection surface 4a and the second connection surface 6a. Formed between. Therefore, in the battery module according to the present embodiment, the generation of blowholes is suppressed without being confined near the boundary between the first connection surface 4a and the second connection surface 6a where the gas generated during welding is in close contact. Become.

  Moreover, the 1st connection surface 4a of the external terminal 4 and the 2nd connection surface 6a of the bus bar 6 are piled up, and the raised part (positioning part 8d) of the 1st recessed part 8b is on the 1st connection surface 4a. The part (gap part 8c) in which the first recess 8b is in close contact is closed by the first connection surface 4a. The first connection surface 4a and the second connection surface 6a in the region where the first recess 8b is blocked are spaced apart. Thus, even if the external terminal 4 and the bus bar 6 are not processed into a complicated shape and structure, the first connection surface 4a and the second connection surface 6a can be obtained only by forming the first recess 8b. The battery modules are separated from each other by an appropriate distance.

  In addition, the battery module is welded from the thin portion 8g to the first connection surface 4a with lower energy than when the bus bar 6 having the same thickness as the thickness of the alignment portion 8d is welded.

  In addition, the gas generated during welding is surely escaped to the gap portion 8c between the first connection surface 4a and the second connection surface 6a, so that a battery module in which the formation of blow holes is suppressed is obtained.

  Moreover, since it has the welding part 9 in which the crack is not formed and the welding part 9 in which the big crack is not formed (even if the crack is formed), it is between the 1st connection surface 4a and the 2nd connection surface 6a. Even if the battery modules are separated from each other, the connection rigidity between the external terminal 4 and the bus bar 6 is maintained.

  Moreover, according to the manufacturing method of the battery module which concerns on this embodiment, the bus bar 6 spaced apart from the 2nd connection surface 6a by the bus bar arrangement | positioning process and arrange | positioned on the 1st connection surface 4a is welded by a welding process. The gas generated when the bus bar 6 is welded to the external terminal 4 escapes to the gap between the first connection surface 4a and the second connection surface 6a. That is, the gas generated at the time of welding is not confined between the first connection surface 4a and the second connection surface 6a. Therefore, the formation of blow holes is suppressed, and the welding width of the welded portion 9 is suppressed from being narrowed. Therefore, even if an external force is applied to the external terminal 4 or the bus bar 6, even when stress is concentrated near the boundary between the first connection surface 4a and the second connection surface 6a in the welded portion 9, the welded portion is not easily damaged. 9 is manufactured. Furthermore, the connection rigidity between the bus bar 6 and the external terminal 4 is ensured in this battery module.

  Further, as the second connection surface 6a of the bus bar 6 comes into close contact with the first connection surface 4a of the external terminal 4, a gap that is partially separated between the first connection surface 4a and the second connection surface 6a. Is formed. The first connection surface 4a and the second connection surface 6a are positioned with respect to each other in a state where the separation distance X1 between the first connection surface 4a and the second connection surface 6a in the gap is kept constant. Therefore, the separation distance X1 between the first connection surface 4a and the second connection surface 6a is maintained at an appropriate distance, and the generation of blow holes is reliably suppressed.

  Moreover, the 1st recessed part 8b formed in the recessed part formation process overlaps the 1st connection surface 4a of the external terminal 4, and the 2nd connection surface 6a of the bus bar 6, and the raised part ( The positioning portion 8d) is brought into close contact with the first connection surface 4a, and the opened portion (gap portion 8c) of the first recess 8b is closed with the first connection surface 4a. The first connection surface 4a and the second connection surface 6a are separated from each other in the region where the first recess 8b is blocked. Thus, even if the external terminal 4 and the bus bar 6 are not processed into a complicated shape and structure, the first connection surface 4a and the second connection surface 6a are separated by an appropriate distance.

  Moreover, the 1st recessed part 8b or the 2nd recessed part 8e is formed with high precision according to the area | region where the external terminal 4 and the bus bar 6 are welded.

  In addition, the bus bar 6 that can be welded from the thin-walled portion 8g to the first connection surface 4a with lower energy than in the case of welding the bus bar 6 having the same thickness as that of the alignment portion 8d in the welding process is formed.

  Further, since the bottom surface of the first recess 8b is formed in a flat shape, the first connection surface 4a and the second connection surface 6a can be welded at any position as long as the first recess 8b is formed. The separation distance X1 around the welded portion 9 is ensured. And since the 1st recessed part 8b is provided in the position on the opposite side to the position in which the 2nd recessed part 8e in the bus bar 6 was provided, the 2nd recessed part 8e is also a mark of the position in which the 1st recessed part 8b was provided. Become.

  Further, gas generated during welding in the welding process can surely escape to the gap portion 8c between the first connection surface 4a and the second connection surface 6a, and the formation of blow holes is suppressed.

  Further, even if the bus bar 6 is welded to the external terminal 4 with the first connection surface 4 a and the second connection surface 6 a being spaced apart in the welding process, the welded portion 9 is accompanied by the welding of the external terminal 4 and the bus bar 6. Thus, a battery module is manufactured in which cracks are unlikely to occur and the connection rigidity between the external terminal 4 and the bus bar 6 is maintained.

  Here, the relationship between the distance X1 between the first connection surface 4a of the external terminal 4 and the second connection surface 6a of the bus bar 6 around the welded portion 9 and the occurrence of blow holes will be described using an example. The materials of the external terminals and bus bars used in this example are both aluminum alloys. Of the thickness of the bus bar, the thickness Xb at the place to be welded is 0.6 mm. The depth D of the gap portion provided in the bus bar is between 6.5 μm and 80 μm (5 points of 6.5 μm, 10 μm, 20 μm, 50 μm, and 80 μm). That is, the thickness X of the area where the bus bar is welded is Xb-D.

  The welding apparatus used for welding the external terminal and the bus bar is a laser welding apparatus. Specifically, the laser welding apparatus is a TruDisk (disc laser) manufactured by Trumpf Co., Ltd. The external terminal and the bus bar were welded by irradiating them with laser light having an output of 4 kW, a wavelength of 1030 nm, and a minimum optical fiber diameter of 200 μm.

  Three measurement samples were prepared at each measurement point of the depth D of each gap. In each measurement sample, observations were made at 12 points in total, 4 points, and the blowhole reduction effect was examined. Specifically, the blowhole formed in the cross section of the welded portion of each measurement sample was observed with an optical microscope, and the pore area per unit area was measured. Then, it was determined that there was an effect of reducing blowholes when the hole area was reduced as compared to the case where no gap was provided.

  As a result, when the depth D of the gap was 6.5 μm, the effect of reducing blowholes was recognized in some of the measurement samples. However, there were some measurement samples in which the effect of reducing blowholes was not recognized. The reason for this is considered that the depth of the gap portion is shallow and a measurement sample in which the gap portion is not completely provided is mixed due to a slight error during manufacture.

  When the depth D of the gap was 10 μm and 20 μm, the effect of reducing blowholes was recognized in all the measurement samples.

  When the depth D of the gap was 50 μm and 80 μm, a blowhole reduction effect was observed. However, a cracked weld was formed on some measurement samples. The cause of this is thought to be stress concentration in the gap and the occurrence of cracks.

  Therefore, if the distance X1 between the first connection surface and the second connection surface around the welded portion is 10 μm or more, it is preferable because the effect of generating blow holes can be obtained more accurately. In addition, the distance X1 between the first connection surface and the second connection surface around the welded portion is preferably less than 50 μm, and more preferably 20 μm or less. If it does in this way, the welded part with a crack will be hard to be formed, and the fall of welding strength will be controlled.

  The power storage device and the manufacturing method according to the present invention are not limited to the above-described embodiments, and it is needless to say that various changes can be made without departing from the gist of the present invention. Moreover, it is needless to say that the configuration, method, and the like according to the following types of modifications may be arbitrarily selected and employed in the configuration, method, and the like according to the above-described embodiment.

  Moreover, in the said embodiment, although the 1st recessed part 8b was provided in the 2nd connection surface 6a of the bus bar 6, it is not limited to this. For example, as shown in FIG. 6, the recess may be a third recess 8 h provided on the first connection surface 4 a of the external terminal 4. In this case, the separation distance of the first connection surface 4a and the second connection surface 6a around the welded portion 9 is the depth of the third recess 8h. Moreover, as shown in FIG. 7, even if a recessed part is the 1st recessed part 8b provided in the 2nd connection surface 6a of the bus bar 6, and the 3rd recessed part 8h provided in the 1st connection surface 4a of the external terminal 4. Good. In this case, the separation distance of the first connection surface 4a and the second connection surface 6a around the welded portion 9 is the sum of the depth of the first recess 8b and the depth of the third recess 8h.

  Further, as shown in FIGS. 8 and 9, even if the first connection surface 4a and the second connection surface 6a are separated from each other by reducing the thickness of the bus bar 6 in the region where the welded portion 9 is included. Good. Moreover, as shown in FIG.10 and FIG.11, the 1st connection surface 4a and the 2nd connection surface 6a are provided by providing the several convex part (positioning part) 8d in the 2nd connection surface 6a of the bus bar 6. As shown in FIG. It may be separated. In FIG.10 and FIG.11, the convex part 8d is provided in four places. Therefore, the convex portion 8d hits the first connection surface 4a of the external terminal 4 at four points. Therefore, the bus bar 6 stands on the first connection surface 4 a of the external terminal 4. Therefore, the separation distance between the first connection surface 4a of the external terminal 4 and the second connection surface 6a of the bus bar 6 is kept constant.

  Moreover, in the said embodiment, the thin part 8g thinner than the circumference | surroundings was provided in the area | region including the welding part 9 by forming the 1st recessed part 8b and the 2nd recessed part 8e in the bus bar 6. However, the present invention is not limited to this. For example, the thin portion may be formed by providing either one of the first recess and the second recess.

  Moreover, in the said embodiment, although the cross-sectional shape in the depth direction of the 1st recessed part 8b and the 2nd recessed part 8e was formed in the rectangular shape by forming a cylindrical hole in the bus bar 6, It is not limited. For example, the first recess and the second recess may have an arc shape or a trapezoidal cross-sectional shape in the thickness direction.

  Moreover, in the said embodiment, although the 1st recessed part 8b was provided in the bus bar 6, and the 1st connection surface 4a and the 2nd connection surface 6a were spaced apart, it is not limited to this. For example, as shown in FIG. 12, the first connection surface 4a and the second connection surface 6a are not provided with a recess, and a shim 8j is sandwiched between the first connection surface 4a and the second connection surface 6a. The first connection surface 4a and the second connection surface 6a may be separated from each other. In this case, the conventional bus bar 6 having no recess and the conventional external terminal 4 having no recess are used as they are.

  Moreover, in the said embodiment, although the separation distance X1 in the circumference | surroundings of the welding part 9 of the 1st connection surface 4a and the 2nd connection surface 6a was 10 micrometers or more and less than 50 micrometers, it is not limited to this. . For example, the separation distance is set by selecting an optimum distance for each shape and material of the bus bar and external terminal to be welded.

  Moreover, in the said embodiment, although applied to the bus bar 6 connected between the external terminals 4 of the adjacent battery cell 1, it is not limited to this. For example, the present invention may be applied to the aforementioned external connection bus bar.

  Moreover, in the said embodiment, although the welding part 9 was formed in planar view annular shape, it is not limited to this. For example, the welded portion may have a planar view line shape, a planar view circular shape, or a planar view rectangular shape.

  Moreover, in the said embodiment, although the external terminal 4 and the bus bar 6 were comprised with the aluminum-type metal material, it is not limited to this. For example, the external terminal 4 and the bus bar 6 may be made of a metal material such as copper, SUS, or steel. That is, the external terminal 4 and the bus bar 6 may be metal materials that are conductive and can be welded to each other.

  In the said embodiment, although the bus bar 6 was welded to the external terminal 4 of the battery cell 1 by laser welding, it is not limited to this. For example, general arc welding or gas welding may be used.

  In the said embodiment, although the battery cell 1 was a square battery, it is not limited to this. For example, the electricity storage element may be a rectangular battery having a rectangular parallelepiped appearance, a round battery having a cylindrical appearance, or the like.

  The present invention is also applicable to various secondary batteries, other primary batteries, and capacitors such as electric double layer capacitors. The type and size (capacity) of the battery are arbitrary.

  DESCRIPTION OF SYMBOLS 1 ... Battery cell (electric storage element), 2 ... Case, 2a ... Case main body, 2b ... Cover plate, 3 ... External gasket, 4 ... External terminal, 4a ... 1st connection surface (positioning part), 4b ... Plate-shaped part 5 ... current collector, 6 ... bus bar, 6a ... second connection surface, 6b ... welding surface, 7 ... main body, 8 ... connection portion, 8a ... first flat surface, 8b ... first recess, 8c ... gap portion, 8d: Alignment part (convex part), 8e: Second concave part, 8f ... Second flat surface, 8g ... Thin wall part, 8h ... Third concave part, 8j ... Shim, 9 ... Welded part, H ... Welding head, L ... Laser Light, X ... separation distance

Claims (13)

A power storage element including an external terminal having a first connection surface;
A bus bar having a second connection surface superimposed on the first connection surface;
In the region where the first connection surface and the second connection surface face each other, a welded portion formed across the external terminal and the bus bar,
At least one of the first connection surface and the second connection surface is provided with a gap portion formed by separating the first connection surface and the second connection surface around at least the welded portion. Power storage device. The power storage device according to claim 1, wherein the first connection surface and the second connection surface are provided with alignment portions that are in close contact with each other outside the gap portion. The power storage device according to claim 2, wherein at least one of the first connection surface and the second connection surface has a recess including the welded portion. The power storage device according to claim 2, wherein the bus bar has a thin portion that is thinner than a thickness of the positioning portion in a region where the gap portion is formed. The power storage device according to any one of claims 1 to 4, wherein a distance between the first connection surface and the second connection surface around the welded portion is 10 µm or more. The power storage device according to claim 5, wherein a separation distance between the first connection surface and the second connection surface around the weld is less than 50 μm. The second connection surface of the bus bar is placed in a state where the first connection surface of the external terminal included in the power storage element and the second connection surface of the bus bar are spaced apart from each other. A bus bar arrangement process to be arranged on one connection surface;
The mutually spaced areas of the first connection surface of the external terminal and the second connection surface of the bus bar are partially welded to form a welded portion in which the external terminal and the bus bar are partially melted. A method for manufacturing a power storage device comprising a welding step. In the bus bar arranging step, the second connection surface of the bus bar is placed on the external terminal so that the first connection surface and the second connection surface are partially separated in a region facing each other. The method for manufacturing the power storage device according to claim 7, wherein the method is in close contact with the first connection surface. A recess forming step of forming a recess in at least one of the first connection surface of the external terminal and the second connection surface of the bus bar and facing each other after the bus bar arranging step; The manufacturing method of the electrical storage apparatus of Claim 8. The method for manufacturing a power storage device according to claim 9, wherein the recess forming step is a press working step. The thickness of the bus bar in the region on the second connection surface that is separated from the first connection surface by the bus bar arrangement step is larger than the thickness of the bus bar in the region on the second connection surface that is in close contact with the first connection surface. The manufacturing method of the electrical storage apparatus of any one of Claims 8 thru | or 10 provided with the thin part formation process which forms a thin thin part. In the bus bar arrangement step, the second connection surface of the bus bar is connected to the first connection of the external terminal so that a separation distance between the first connection surface and the second connection surface around the welded portion is 10 μm or more. The method for manufacturing a power storage device according to claim 7, wherein the power storage device is superposed on a surface. In the bus bar arranging step, the second connection surface of the bus bar is connected to the first connection of the external terminal so that a distance between the first connection surface and the second connection surface around the welded portion is less than 50 μm. The method for manufacturing a power storage device according to claim 12, wherein the power storage device is superposed on a surface.

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