Accumulator assembly with improved welding technology for a cell connector element

Abstract

Accumulator arrangement (100; 500; 600), with - a first accumulator cell (101) with at least one electrical connection element (104); - a second accumulator cell (101) with at least one electrical connection element (106); - a cell connector element (105) that electrically connects an electrical connection element (104) of the first accumulator cell (101) and an electrical connection element (106) of the second accumulator cell (101) and that is welded to at least one of the electrical connection elements (104, 106) of one of the accumulator cells (101) by means of a plurality of weld points (120; 530; 630), wherein the number and location of the weld points (120; 530; 630) are selected depending on an expected current density such that more weld points (120; 530; 630) are arranged at locations with a higher expected current density and no or fewer weld points are arranged at locations with a lower expected current density, wherein the first and second accumulator cell (101) have an electrode (108) coupled to the electrical connection element (104, 106), which takes charge from the respective accumulator cell (101), wherein the cell connector element (105) has an open area (114) which extends between the electrode (108) of the first accumulator cell (101) and the electrode (108) of the second accumulator cell (101) and which extends over the electrodes (108), wherein the welding points (120; 530; 630) are arranged offset on both sides of the open area (114) and the electrode (108) and in the direction of the respective other accumulator cell (101), wherein the cell connector element (105) has a U-shaped bulge (112) in the area between the electrical connection element (104) of the first accumulator cell (101) and the electrical connection element (106) of the second accumulator cell (101), wherein on each side next to the open area (114) and the electrode (108) a welding point (120; 530; 630) has the form of a partial circle (120; 530; 630) whose free end sections are oriented in the direction away from the respective other accumulator cell (101).

Description

[0001] The present invention relates to an accumulator arrangement with an improved welding technique for attaching a cell connector element to an accumulator cell.

[0002] Electrically powered motor vehicles use battery systems in which a number of battery cells, for example, prism-shaped battery cells, are connected in series to form a module. The modules can be permanently connected in series and / or parallel or their configuration can be changed during operation of the motor vehicle, thus forming a traction battery. The traction battery powers an electric motor to propel the motor vehicle. The fundamentals of electric drives are familiar to those skilled in the art and, for the sake of conciseness, will not be explained further here.

[0003] Cell connector elements are designed to connect the opposite poles of two adjacent cells. The cell connectors are connected to two terminal elements of two accumulator cells, with the terminal elements of each accumulator cell being electrically connected to an electrode. It is known that the cell connector element can be welded to the terminal element, for example, by means of circular welds. It is also known to screw or bind the cell connector elements to the terminal elements.

[0004] Laser welding a cell connector element to a terminal element has the disadvantage of generating a high amount of energy in the form of heat in both the cell connector and the terminal element. This can damage nearby plastic components and, in the worst case, the battery cell itself. Furthermore, laser beam welding requires a minimum size (height and width) for the terminal elements and cell connector elements, thus requiring more installation space. Additionally, laser beam welding necessitates significant investment in system technology, which is only justified if the joining process is considerably faster compared to alternative methods.

[0005] DE 10 2010 020 065 A1 discloses an energy storage module with a plurality of prismatic cells and a cell contacting unit comprising a carrier on which several cell connectors are arranged, via which a respective terminal of first polarity of a storage cell is electrically connected to a respective terminal of second polarity of an adjacent storage cell.

[0006] DE 10 2010 046 529 A1 discloses a frame system for receiving at least one battery cell.

[0007] US patent 2010 / 0167115 A1 discloses a battery system with a battery block comprising a plurality of battery cells arranged next to each other by means of insulating separators.

[0008] DE 10 2008 059 970 A1 discloses a battery in which flexible cell connectors are arranged on a rigid cell connector board.

[0009] DE 10 2011 080 977 A1 discloses a cell connector for electrically connecting terminals of battery cells with a layer of a first material and a second layer of a second material, wherein the two layers are each provided with a small hole and a larger hole and the layers are arranged one above the other in such a way that the small hole of one layer is arranged essentially coaxially to the larger hole of the other layer.

[0010] DE 10 2006 015 566 A1 discloses a pole connector for electrically connecting two electrical poles of individual cells of an electrochemical energy storage device, comprising a bundle of at least two conductor elements, each bridging the gap between the poles to be connected.

[0011] DE 10 2011 075 853 A1 discloses a cell connector with at least two compensation sections which each extend along a connection direction from the first contact area to the second contact area and are separated from each other transversely to the connection direction.

[0012] DE 25 16 530 A1 discloses the attachment of a connector element to a battery by means of a plurality of welding points.

[0013] US 2010 / 0266890 A1 discloses a cell connector having an opening in the area of ​​an electrode of a battery cell, wherein the cell connector is attached to the battery cell by means of welds in the form of arc segments or straight welds.

[0014] US 2014 / 0045039 A1 discloses an accumulator arrangement with a cell connector element that has an opening in the area of ​​the electrode, wherein the weld points are arranged in a spot-like manner around the electrode or have the form of arc segments.

[0015] EP 1 450 422 A1 discloses cell connectors that have an opening in the area of ​​an electrode of a battery cell. Weld points are arranged around the electrode.

[0016] FR 2 915 626 discloses connecting elements for accumulator cells, which are attached to the accumulator cells by means of welds.

[0017] DE 10 2013 213 540 A1 discloses a connecting element for accumulator cells with a curvature located between the contact points. The contact points with the electrode can have round or straight weld seams.

[0018] US 2009 / 0104516A1 discloses connecting elements for accumulator cells which have an opening in the area of ​​the electrode and which are attached to the accumulator cells by means of spot welds.

[0019] The JP 2002-246 003 A describes flat connecting elements for batteries in which welding points are arranged around contact points.

[0020] Further connecting elements are described in US 2005 / 0 287 427 A1 as well as DE 10 2009 058 723 A1 and JP 2007 - 194 036 A.

[0021] The invention aims to create an accumulator arrangement with an improved welded connection.

[0022] The object of the invention is solved by an accumulator arrangement according to claim 1.

[0023] An accumulator assembly comprises a first accumulator cell with at least one electrical connection element, a second accumulator cell with at least one electrical connection element, and a cell connector element that electrically connects an electrical connection element of the first accumulator cell and an electrical connection element of the second accumulator cell and that is welded to at least one of the electrical connection elements of one of the accumulator cells by means of a plurality of weld points. The number and location of the weld points are selected depending on the expected current density such that more weld points are arranged at locations with a higher expected current density and fewer or no weld points are arranged at locations with a lower expected current density. The electrical connection element draws charge from the accumulator cell and / or supplies charge to the accumulator cell.The electrical terminal element to which the cell connector element is connected of the first accumulator cell can have an opposite polarity to the electrical terminal element to which the cell connector element is connected of the second accumulator cell. This allows for a series connection of accumulator cells, as is desirable, for example, in traction batteries. The term "location with a lower expected current density" also implies that no current flows at that location. At locations with a higher expected current density, the expected current density is higher than at locations with a lower expected current density. The weld locations can form one or more weld surfaces.

[0024] To reduce heat input into the battery cell and to shorten the cycle time when attaching the cell connector element, the inventors propose minimizing the length of the weld seam between the cell connector element and the terminal element while maintaining a constant contact resistance. This is achieved by optimizing the geometry of the weld seam and / or weld points with respect to current flow, particularly current density. In the prior art, weld circles are created on the terminal elements, which, as a minimum requirement, have a contact area of ​​approximately 40 mm². 2In contrast, the inventors propose continuous and / or segmented welds or weld points that are significantly smaller in area than the weld circles used in the prior art. For example, the area of ​​the weld and / or weld points can be reduced by about half without increasing the contact resistance between one battery cell and another. Preferably, the area of ​​the weld points where a cell connector element is attached to an electrical connection element is a maximum of approximately 30 mm². 2 , preferably a maximum of 20 mm 2 , preferably a maximum of 15 mm 2 .

[0025] A weld location can be a single weld point. Several weld locations can form a weld seam or weld area. This can occur when the locations are adjacent to each other. The weld locations can form a continuous weld seam or weld area, or an interrupted weld seam or weld area, where each segment of the interrupted weld seam or weld area comprises a plurality of weld locations arranged adjacent to or alongside each other.

[0026] The weld locations can consist of individual weld spots, a discontinuous weld seam, and / or a continuous weld seam. The weld locations can be in the form of a continuous partial circle consisting of a weld seam or a discontinuous partial circle consisting of multiple spaced weld seams or spaced weld spots. A continuous partial circle can consist of multiple adjacent, touching weld locations or a linear weld seam. A discontinuous partial circle can consist of multiple segments where the weld locations touch or form a weld seam. The weld spots or the weld seam can be produced, for example, by laser welding. A partial circle formed by weld locations has a width that corresponds to the width of the weld locations, depending on the welding technology used.

[0027] The first and second accumulator cells each have an electrode coupled to the terminal element, which draws charge from the respective accumulator cell. The electrode can have a circular cross-section. The electrode can extend from the terminal element into the accumulator cell. The continuous graduated circle can be arranged around the electrode. The interrupted graduated circle can be arranged around the electrode. The interrupted straight line can be arranged in an edge region of the terminal element that is directed towards the other accumulator cell.

[0028] The cell connector element has an open area extending between the electrode of the first battery cell and the electrode of the second battery cell, with the open area extending across the electrode. This open area increases the elasticity of the cell connector to accommodate manufacturing tolerances and dimensional changes of the battery cells during operation.

[0029] The aforementioned welding points are arranged on both sides next to the open area and the electrode, offset towards the other accumulator cell.

[0030] The cell connector element has a bulge in the area between the electrical terminal of the first battery cell and the electrical terminal of the second battery cell. This bulge also increases the elasticity of the cell connector to accommodate manufacturing tolerances and dimensional changes of the battery cells during operation.

[0031] The highest line of the curvature can be arranged perpendicular to the open area.

[0032] The invention makes it possible to reduce the weld area by approximately 50%. This also reduces the manufacturing time for the battery assembly according to the invention, which has a significant impact on the investment required for system technology, especially in high-volume production. Furthermore, halving the weld area means that the energy input into the components during welding is also approximately halved. This makes it possible to design the cell connector element and the electrical connection elements to be smaller, thereby reducing installation space and weight. In addition, the thermal stress on the battery cell and nearby plastic components is reduced, which creates greater design freedom in the development of new battery modules.

[0033] The invention will now be described in more detail and without limitation with reference to the attached figures, wherein Fig. Figure 1 shows a perspective view of an accumulator arrangement according to the invention; Fig. 2 shows a schematic section through a connecting element and two electrical connection elements; Fig. 3 shows a second embodiment of the invention, not according to the invention, with two different types of welds; Fig. 4 shows a third embodiment, not according to the invention, with an interrupted straight weld seam; Fig. 5 shows a fourth embodiment, not according to the invention, with several continuous straight welds; Fig. 6 shows a fifth embodiment of the invention in which the welds have the shape of partial circles; Fig. 7 shows a sixth embodiment according to the invention, in which the welds have a form of interrupted partial circles; Fig. Figure 8 shows a seventh embodiment, not according to the invention, in which the welds have the form of continuous straight lines arranged at right angles to each other; Fig. 9 shows an eighth embodiment, not according to the invention, with broken straight lines arranged at right angles to each other; and Fig. Figure 10 shows a top view of an accumulator arrangement.

[0034] It will be on Fig. Reference is made to 10, which shows a first embodiment of the invention. Furthermore, reference is made to Fig. 1 Reference is made to a perspective view of connection elements 104 and a connector element 105, and to Fig. 2 Reference is made to Figure 2, which shows a section through the connector element 105 and the connecting elements 104, 106.

[0035] A plurality of accumulator cells 101 are arranged side by side. Each accumulator cell 101 comprises a first terminal element 104 and a second terminal element 106, into each of which an electrode 108 with a round cross-section extends. The electrode also extends into the interior of the accumulator cell 101 in order to supply charge to and / or withdraw charge from the accumulator cell 101.

[0036] The first terminal element 104 of a first accumulator cell 101 is connected to the second terminal element 106 of a second accumulator cell 101 by means of a cell connector 105. In the first embodiment, the cell connector elements 105 are fastened by means of a plurality of spot welds forming an interrupted partial circle 120.

[0037] The interrupted partial circle is arranged next to electrode 108. The weld points of the interrupted partial circle 120 are located in an area where high current densities are expected. There, the transition from the connection element 104, 106 to the connector element 105 exhibits low electrical resistance. The connector element 105 also has an open area extending from the electrode of one accumulator cell 101 to an electrode 108 of another accumulator cell 101, and this open area is narrower than the electrode. Furthermore, the electrodes 101 are not covered by this open area. The open area 114 accommodates mechanical tolerances and dimensional changes, for example, due to temperature and state of charge.

[0038] Furthermore, the connector element 105 comprises a substantially U-shaped bulge 112, which extends substantially perpendicular to the open area 114. The substantially U-shaped bulge 112 also serves to accommodate mechanical tolerances and dimensional changes due to temperature and state of charge.

[0039] In the first embodiment, the interrupted partial circle 120, which is formed from spot welds, is essentially a semicircle.

[0040] It will be on Fig. Reference is made to Figure 3, which shows a second embodiment, whereby, for the sake of conciseness, only the differences from the first embodiment are mentioned. The connector element 105 is connected to the terminal elements 104, 106 by means of a semicircular arrangement of spot welds 220. The semicircularly arranged spot welds 220 form two partial circles at each electrode, which correspond approximately to a quarter circle. Furthermore, the connector element 105 is attached to the terminal elements 104, 106 by means of a broken straight line 222 of spot welds in order to electrically connect the connector element 105 to the terminal elements 104, 106. Optional individual spot welds 228 serve for the mechanical fixing of the connector element 105 to the terminal elements 104, 106.

[0041] It will be on Fig. Reference is made to Figure 4, which shows a third embodiment 300, in which the connecting element 105 is attached by means of a broken straight line 322 formed by spot welds. The broken line 322 is arranged at the edge region of the connecting element 104, 106, which is directed towards the other connecting element. Each spot weld can have an edge length of approximately 1 mm.

[0042] It will be on Fig. Reference is made to Figure 5, which shows a fourth embodiment in which the connector element 105 is electrically connected to the connecting elements 104, 106 by means of a continuous straight line at weld locations which form a weld seam 422.

[0043] It will be on Fig. 6, Fig. 7, Fig. 8 to Fig. 9 referenced, which show different possibilities for welding locations, whereby Fig. 6 fifth embodiment according to the invention 500 shows, Fig. 7 shows a sixth embodiment 600 according to the invention, Fig. 8 shows a seventh embodiment 700 and Fig. Figure 9 shows an eighth embodiment 800. In the fifth to ninth embodiments, weld spots 530, 630, 740, 840 are produced next to the electrode 108 and the open area, wherein the weld spots 530, 630, 740, 840 are arranged offset from the center point of the electrode 108 in the direction of the respective other connection element 104, 106.

[0044] In the fifth embodiment according to Fig. 6 The weld locations 530 form a semi-circular continuous weld seam 530. The convex end of the semi-circular weld seam 530 is directed towards the respective other connection element 104, 106.

[0045] The sixth embodiment according to Fig. 7 essentially corresponds to the fifth embodiment 500 according to Fig. 6, wherein in the sixth embodiment 600 the welding locations 630 are formed by an interrupted partial circle 630 with a plurality of welding segments or spaced-apart welding points.

[0046] In the seventh embodiment according to Fig. 8. The weld points 740 are formed by two touching perpendicular lines 740. A first line is arranged essentially parallel to the edges of the connecting elements 104, 106 and is directed towards the respective opposite connecting element 104, 106. The second continuous straight weld is oriented perpendicular to the edge of the connecting element 104, 106 and is directed towards the opposite connecting element 104, 106. The connection points of the weld points 740, formed by the two linear welds 740, are directed towards the center and / or open area 114 of the connecting element 105.

[0047] The eighth embodiment of invention 800 according to Fig. 9 essentially corresponds to the seventh embodiment 700 according to Fig. 8, wherein the broken lines are formed by a plurality of spaced segments or spaced welds, each with a plurality of weld points or weld locations.

[0048] The weld locations, weld points, weld seams, and the like can be formed, for example, by laser welding. Laser welding processes are currently preferred because of the comparatively low heat input into the battery cells.

[0049] A broken line, a broken partial circle, a broken semicircle, or the like comprises a plurality of spaced-apart segments. Each segment may have a weld spot or a weld location. However, it is also possible for each segment to have a plurality of weld locations arranged in a row, forming, for example, a (short) continuous weld seam. Each weld location has a length and width. A weld location within the meaning of this invention is therefore two-dimensional. A line, a partial circle, or a segment is formed by a plurality of adjacent weld locations. The expression "adjacent weld locations" does not imply that individual points must be produced in the sense of spot welding.A continuous line, a continuous partial circle, a continuous semicircle or the like can also be produced by a continuous welding process, thereby creating the adjacent weld locations.

[0050] The inventors of the present invention have recognized that a connecting element 105 can be welded to terminal elements 104, 106 of a battery cell 110 by means of comparatively short weld seams and / or by means of a comparatively low number of weld points on a terminal element 104, 106 of a battery cell 110 if the weld locations, weld points, weld seams, or the like are located in an area where a higher current density is expected than in other locations. The reduced number of weld locations, weld points, weld seams, or the like can reduce the thermal stress on the battery cell 101 during manufacturing. Furthermore, the cycle time for the welding process can be reduced, which is highly relevant for high production volumes.

Claims

[1] Accumulator arrangement (100; 500; 600), with - a first accumulator cell (101) with at least one electrical connection element (104); - a second accumulator cell (101) with at least one electrical connection element (106); - a cell connector element (105) that electrically connects an electrical connection element (104) of the first accumulator cell (101) and an electrical connection element (106) of the second accumulator cell (101) and that is welded to at least one of the electrical connection elements (104, 106) of one of the accumulator cells (101) by means of a plurality of weld points (120; 530; 630), wherein the number and location of the weld points (120; 530; 630) are selected depending on an expected current density such that more weld points (120; 530; 630) are arranged at locations with a higher expected current density and no or fewer weld points are arranged at locations with a lower expected current density, wherein the first and second accumulator cell (101) have an electrode (108) coupled to the electrical connection element (104, 106), which takes charge from the respective accumulator cell (101), wherein the cell connector element (105) has an open area (114) which extends between the electrode (108) of the first accumulator cell (101) and the electrode (108) of the second accumulator cell (101) and which extends over the electrodes (108), wherein the welding points (120; 530; 630) are arranged offset on both sides of the open area (114) and the electrode (108) and in the direction of the respective other accumulator cell (101), wherein the cell connector element (105) has a U-shaped bulge (112) in the area between the electrical connection element (104) of the first accumulator cell (101) and the electrical connection element (106) of the second accumulator cell (101), wherein on each side next to the open area (114) and the electrode (108) a welding point (120; 530; 630) has the form of a partial circle (120; 530; 630) whose free end sections are oriented in the direction away from the respective other accumulator cell (101). [2] Accumulator arrangement (100; 500; 600) according to claim 1, wherein the weld locations have at least one of the following shapes: - a continuous partial circle (530) from a weld seam; and / or - an interrupted partial circle (630) consisting of a plurality of spaced welds or spaced weld spots [3] Accumulator arrangement (100; 500; 600) according to claim 1, wherein the highest line of the curvature (112) is arranged perpendicular to the open area (114).

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