Battery cell tab shape variation to optimize battery cell-to-bus bar electrical connections

Abstract

The present disclosure provides battery cell tab shape variations that optimize battery cell to bus bar electrical connections. Exemplary battery cell tab terminals and bus bar configurations for electrically connecting battery cells within a traction battery pack are provided. An exemplary battery cell may include a tab terminal having a tab end section that is shaped to provide a local thickness increase that is adapted to reduce weld spatter and increase weld quality when welding the tab terminal to a bus bar. The bus bar may include a weld joint backing structure that facilitates positioning and welding the tab terminal to the bus bar.

Description

Technical Field

[0001] The present disclosure generally relates to an electrified vehicle traction battery pack, and more particularly to techniques for electrically connecting battery cells of a traction battery pack. Background Art

[0002] High-voltage traction battery packs typically supply power to an electric motor and other electrical loads of an electrified vehicle. The traction battery pack includes a plurality of battery cells. The battery cells must be reliably connected to each other in order to provide the voltage levels and power levels necessary to achieve vehicle propulsion. Summary of the Invention

[0003] A battery cell according to an exemplary aspect of the present disclosure particularly includes a housing and a tab terminal protruding outward from the housing. The tab terminal includes a tab end segment having a shape that provides a local thickness increase, and the local thickness increase is adapted to reduce welding spatter when the tab terminal is welded to a bus bar.

[0004] In a further non-limiting embodiment of the foregoing battery cell, the shape includes a crimped portion that provides the local thickness increase at the tab end segment.

[0005] In a further non-limiting embodiment of any of the foregoing battery cells, the shape extends along a curved path that provides the local thickness increase at the tab end segment.

[0006] In a further non-limiting embodiment of any of the foregoing battery cells, the curved path establishes a convex shape of the tab end segment.

[0007] In a further non-limiting embodiment of any of the foregoing battery cells, a first bend connects the tab end segment to a tab proximal segment of the tab terminal.

[0008] In a further non-limiting embodiment of any of the foregoing battery cells, a second bend connects a distal tip portion of the tab end segment to a proximal tip portion of the tab end segment.

[0009] In a further non-limiting embodiment of any of the foregoing battery cells, the distal tip portion folds around the second bend toward the proximal tip portion.

[0010] In a further non-limiting embodiment of any of the foregoing battery cells, the second bend establishes a part of the crimped portion of the tab end segment.

[0011] In a further non - limiting embodiment of any of the foregoing battery cells, the second bend positions the distal tip portion of the tab end segment at an angle relative to the proximal tip portion of the tab end segment.

[0012] In a further non - limiting embodiment of any of the foregoing battery cells, the distal tip portion extends towards and is spaced from the tab proximal segment.

[0013] A traction battery pack according to another exemplary aspect of the present disclosure particularly includes: a bus bar including an opening and a weld joint backing structure disposed near the opening; a battery cell including a tab terminal extending into the opening to a position adjacent to the weld joint backing structure; and a weld portion fixing the tab terminal to the weld joint backing structure.

[0014] In a further non - limiting embodiment of the foregoing traction battery pack, the weld joint backing structure includes a bent portion.

[0015] In a further non - limiting embodiment of any of the foregoing traction battery packs, the distal end segment of the tab terminal is received against the angled surface of the bent portion of the weld joint backing structure.

[0016] In a further non - limiting embodiment of any of the foregoing traction battery packs, the distal end segment includes a crimped portion or extends along a curved path to establish a local thickness increase.

[0017] In a further non - limiting embodiment of any of the foregoing traction battery packs, the weld joint backing structure includes a bent portion that is bent relative to the body of the bus bar.

[0018] In a further non - limiting embodiment of any of the foregoing traction battery packs, the distal end segment of the tab terminal is received against the angled surface of the bent portion of the weld joint backing structure.

[0019] In a further non - limiting embodiment of any of the foregoing traction battery packs, the distal end segment includes a crimped portion or extends along a curved path to establish a local thickness increase.

[0020] In a further non - limiting embodiment of any of the foregoing traction battery packs, the tab terminal includes at least two bends.

[0021] In a further non - limiting embodiment of any of the foregoing traction battery packs, the bus bar includes a first metal material and the tab terminal includes a second metal material different from the first metal material.

[0022] According to another exemplary aspect of the present disclosure, a method for establishing an electrical connection between a battery cell and a bus bar particularly includes positioning a tab terminal of the battery cell into an opening of the bus bar and at a position adjacent to a weld joint backing structure of the bus bar; and welding the tab terminal to the weld joint backing structure. The tab terminal includes a shape that provides a local thickness increase within a tab end segment of the tab terminal for reducing welding spatter and increasing welding quality during welding.

[0023] The embodiments, examples, and alternatives (including any of their respective aspects or corresponding respective features) of the foregoing paragraphs, claims, or the following description and drawings may be employed independently or in any combination. Features described in connection with one embodiment apply to all embodiments unless such features are incompatible.

[0024] In view of the following detailed description, various features and advantages of the present disclosure will become apparent to those skilled in the art. The accompanying drawings that are attached to the detailed description may be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 An electrified vehicle is schematically shown.

[0026] Figure 2 is a perspective view of a traction battery pack of the electrified vehicle.

[0027] Figure 3 is Figure 2 a schematic cross-sectional view of the height of the traction battery pack of

[0028] Figure 4 showing battery cells within the traction battery pack.

[0029] Figure 5 showing a selected portion of a bus bar configured to engage tab terminals of a set of battery cells.

[0030] Figure 6 is a cross-sectional view taken along section 6-6 through Figure 5 of

[0031] Figure 7 is a cross-sectional view of another exemplary bus bar configured to engage tab terminals of a set of battery cells.

[0032] Figure 8A and Figure 8B show exemplary tab terminals of a battery cell.

[0033] Figure 9A and Figure 9B show another exemplary tab terminal of a battery cell.

[0034] Figure 10 Shows another exemplary tab terminal of a battery cell.

[0035] Figure 11 Shows another exemplary tab terminal of a battery cell.

[0036] Figure 12 Shows another exemplary tab terminal of a battery cell.

[0037] Figure 13 Shows yet another exemplary tab terminal of a battery cell. Detailed Description

[0038] The present disclosure describes in detail exemplary battery cell tab terminals and bus bar configurations for electrically connecting battery cells within a traction battery pack. Exemplary battery cells can include tab terminals having tab end segments that are shaped to provide a local thickness increase that is adapted to reduce welding spatter and increase welding quality when welding the tab terminals to the bus bars. The bus bars can include weld joint backing structures that facilitate positioning and welding the tab terminals to the bus bars. These features and other features are discussed in more detail in the following paragraphs of this detailed description.

[0039] Figure 1 An electrified vehicle 10 is schematically shown. The electrified vehicle 10 can include any type of electrified powertrain. In an embodiment, the electrified vehicle 10 is a battery electric vehicle (BEV). However, the concepts described herein are not limited to BEVs and can be extended to other electrified vehicles, including but not limited to hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles, etc. Thus, although not specifically shown in the exemplary embodiments, the powertrain of the electrified vehicle 10 can be equipped with an internal combustion engine that can be employed alone or in combination with other power sources to propel the electrified vehicle 10.

[0040] In the illustrated embodiment, the electrified vehicle 10 is depicted as an automobile. However, the electrified vehicle 10 can alternatively be a sport utility vehicle (SUV), van, pickup truck, or any other vehicle configuration. Although specific component relationships are shown in the drawings of the present disclosure, the illustrations are not intended to limit the present disclosure. The placement and orientation of the various components of the electrified vehicle 10 are schematically shown and can vary within the scope of the present disclosure. Additionally, the various drawings attached to the present disclosure are not necessarily drawn to scale, and some features may be enlarged or minimized to emphasize certain details of particular components or systems.

[0041] In the illustrated embodiment, the electrified vehicle 10 is a pure electric vehicle that is propelled only by electricity (such as by one or more electric motors 12) without assistance from an internal combustion engine. The electric motor 12 can operate as an electric motor, a generator, or both. The electric motor 12 receives electrical power and can convert the electrical power into torque for driving one or more wheels 14 of the electrified vehicle 10.

[0042] A voltage bus 16 can electrically couple the electric motor 12 to a traction battery pack 18. The traction battery pack 18 is an exemplary electrified vehicle battery. The traction battery pack 18 can be a high-voltage traction battery pack assembly that includes a plurality of battery cells capable of outputting electrical power to supply the electric motor 12 and / or other electrical loads of the electrified vehicle 10. Other types of energy storage devices and / or output devices can alternatively or additionally be used to power the electrified vehicle 10.

[0043] The traction battery pack 18 can be fixed to the vehicle body bottom 20 of the electrified vehicle 10. However, within the scope of the present disclosure, the traction battery pack 18 can be located elsewhere on the electrified vehicle 10.

[0044] Figure 2 and Figure 3 Additional details associated with the traction battery pack 18 of the electrified vehicle 10 are shown. The traction battery pack 18 can include one or more battery arrays 22 (e.g., battery assemblies or groups of rechargeable battery cells 24) capable of outputting electrical power to supply the electric motor 12 and / or other electrical loads of the electrified vehicle 10. Other types of energy storage devices and / or output devices can alternatively or additionally be used to power the electrified vehicle 10.

[0045] The battery cells 24 can be stacked side by side along a stacking axis to form a group of battery cells 24, sometimes referred to as a "cell stack". In a Figure 3 schematic height depiction, the battery cells 24 are stacked in the direction into the page to construct each battery array 22, and thus the battery arrays 22 can extend in the vehicle lateral direction. However, other configurations can also be possible. The total number of battery arrays 22 and battery cells 24 provided within the traction battery pack 18 is not intended to limit the present disclosure.

[0046] In an embodiment, the battery cells 24 of each battery array 22 are pouch-type lithium-ion cells. However, battery cells having other geometries (cylindrical, prismatic, etc.), other chemistries (nickel-metal hydride, lead-acid, etc.), or both can alternatively be used within the scope of the present disclosure.

[0047] The battery array 22 and various other battery internal components (e.g., bus electrical centers, battery electrical control modules, wiring, connectors, etc.) can be housed within the internal region 26 of the housing assembly 28 (see Figure 3 ). The housing assembly 28 can include a housing cover 30 and a housing tray 32. The housing cover 30 can be fixed (e.g., bolted, welded, adhered, etc.) to the housing tray 32 to provide the internal region 26. The size, shape, and overall configuration of the housing assembly 28 are not intended to limit the present disclosure.

[0048] Figure 4 Shown is one of the battery cells 24 that can be disposed within the traction battery pack 18. Each battery cell 24 can include a housing 36 and a pair of tab terminals 34 that project outwardly from the housing 36. In an embodiment, each battery cell 24 includes two tab terminals 34, with each tab terminal 34 projecting outwardly at each opposite side of the housing 36. One of the tab terminals 34 can provide the positive terminal of the battery cell 24, and the other tab terminal 34 can provide the negative terminal of the battery cell 24. However, other configurations are also envisioned within the scope of the present disclosure.

[0049] The tab terminals 34 of the battery cells 24 of each battery array 22 must be reliably connected to each other in order to provide the voltage levels and power levels required to achieve vehicle propulsion. Sometimes busbars are used for these connections; however, it can be difficult to properly position and align the tab terminals 34 relative to the busbar during the assembly and welding processes. Additionally, busbars are generally thicker than the tab terminals 34, thereby introducing welding complexities that can lead to burn-through and / or welding spatter. Accordingly, the present disclosure specifically relates to variations in tab terminal shapes that can be used to optimize the electrical connection of battery cells to busbars.

[0050] Figure 5 and 6 Shown is a selected portion of a busbar 38 that can be joined to the tab terminals 34 of a set of battery cells 24 for electrically connecting the battery cells 24. For example, the set of battery cells 24 can be a part of one of the battery arrays 22 of the traction battery pack 18. Once electrically coupled, the battery cells 24 can supply power to various components of the electrified vehicle 10.

[0051] The tab terminals 34 and the busbar 38 can be metal components. In an embodiment, the busbar 38 is made of copper or aluminum, and the tab terminals are made of aluminum. However, other materials or combinations of materials are envisioned within the scope of the present disclosure.

[0052] The busbar 38 can include a plurality of openings 40. Each opening 40 can be formed through the body 42 of the busbar 38 and can be sized to receive one of the tab terminals 34. Each tab terminal 34 can extend at least partially into one of the openings 40.

[0053] The bus bar 38 may additionally include a plurality of weld joint backing structures 44, and the tab terminals 34 may butt against the bus bar 38 at the plurality of weld joint backing structures. For example, one weld joint backing structure 44 may be provided at each opening 40 of the bus bar 38 and may be configured to establish the base of the opening 40. In one embodiment, the weld joint backing structure 44 extends from the body 42 in a direction away from the battery cell 24.

[0054] In an embodiment, each weld joint backing structure 44 may include a bent portion 46 formed in the body 42 of the bus bar 38. The bent portion 46 may extend in a direction away from the battery cell 24 from which the tab terminal 34 protrudes and may provide an elongated groove 50 for receiving the tab terminal 34. The bent portion 46 may limit the distance that the tab terminal 34 can be inserted into the elongated groove 50. For example, the inner surface 48 of the bent portion 46 may be used as a stop for limiting the insertion distance of the tab terminal 34. In this way, the bent portion 46 may assist in positioning and placing the tab terminal 34 relative to the bus bar 38. The outer section 35 of the tab terminal 34 (see Figure 5 ) may extend outside of the elongated groove 50 established by the bent portion 46.

[0055] In another embodiment, each weld joint backing structure 44 may include a flared portion 52 as an alternative to the bent portion 46 (see Figure 7 ). Each flared portion 52 may protrude in a direction away from the battery cell 24.

[0056] The tab terminal 34 may be received against the angled surface 54 of the weld joint backing structure 44. Each angled surface 54 may provide a relatively flat surface for creating one or more welds 56 for joining the tab end section 60 to the angled surface 54.

[0057] Each tab terminal 34 may be joined to the angled surface 54 of one of the weld joint backing structures 44 of the bus bar 38 by one or more welds 56. The welds 56 may be linear welds, non-linear welds, or any other weld pattern. Prior to forming the welds 56, the tab terminal 34 may optionally be clamped and / or spot welded to the weld joint backing structure 44 to assist in the joining process.

[0058] The shape of each tab terminal 34 may be specifically designed to optimize the battery cell to bus bar electrical connection. Figure 8A and Figure 8B show a first exemplary tab terminal 34 configuration that may provide an optimized battery cell to bus bar electrical connection (continue to refer to Figures 3 to 6)。Exemplary tab terminal 34 may include a tab proximal section 58 that extends from an internal electrode of the battery cell to a location external to the housing 36 of the battery cell 24. The tab proximal section 58 may be substantially straight along its length.

[0059] The tab terminal 34 may additionally include a first bend 62 that positions the tab end section 60 at an angle relative to the tab proximal section 58. The tab end section 60 may include a proximal tip portion 66 and a distal tip portion 68. The distal tip portion 68 may be folded toward the proximal tip portion 66 about a second bend 70. Once folded, the distal tip portion 68 may be positioned between the proximal tip portion 66 and the tab proximal section 58. The distal tip portion 68 may contact the tab proximal section 58 or may be slightly spaced therefrom.

[0060] The proximal tip portion 66, the distal tip portion 68, and the second bend 70 may together establish a crimp portion 72 of the tab end section 60. The crimp portion 72 provides a local thickness increase TI at the tab end section 60 of the tab terminal 34. Accordingly, during the process of welding the tab end section 60 of the tab terminal 34 to the bus bar 38, the tab terminal 34 is less likely to be welded through and effectively limits welding spatter in the direction toward the battery cell 24.

[0061] Figure 9A and Figure 9B Another exemplary tab terminal 134 is shown that is shaped to optimize the battery cell to bus bar electrical connection. The exemplary tab terminal 134 may include a tab proximal section 158 that may be connected to the housing of the battery cell. The tab proximal section 158 may be substantially straight along its length.

[0062] The tab terminal 134 may additionally include a first bend 162 that positions the tab end section 160 at an angle relative to the tab proximal section 158. The tab end section 160 may include a proximal tip portion 166 and a distal tip portion 168. A second bend 170 may position the distal tip portion 168 at an angle relative to the proximal tip portion 166. The distal tip portion 168 may extend toward the tab proximal section 158 and may contact the tab proximal section 158 or may be slightly spaced therefrom.

[0063] Due to the second bending portion 170, the tab end portion segment 160 can extend along a bending path 174 and thus presents a convex shape. The bending path 174 is formed as a barrier to protect the sensitive components from welding spatter. Accordingly, the tab terminal 134 is configured to stop the momentum of the welding spatter and / or redirect the welding spatter to a benign area of the battery array / traction battery pack 24 during the process of welding the tab end portion segment 160 of the tab terminal 134 to the bus bar.

[0064] Figure 10 Another exemplary tab terminal 234 is shown that is shaped to optimize the electrical connection from the battery cell to the bus bar. The exemplary tab terminal 234 can include a tab proximal segment 258 that can be connected to the housing of the battery cell. The tab proximal segment 258 can be substantially straight along its length.

[0065] The tab terminal 234 can additionally include a first bending portion 262 that positions the tab end portion segment 260 at an angle relative to the tab proximal segment 258 to provide a simple hook shape. The tab end portion segment 260 can be substantially straight to provide a straight interface surface 261.

[0066] Figure 11 Another exemplary tab terminal 334 is shown that is shaped to optimize the electrical connection from the battery cell to the bus bar. The exemplary tab terminal 334 can include a tab proximal segment 358 that can be connected to the housing of the battery cell. The tab proximal segment 358 can be substantially straight along its length.

[0067] The tab terminal 334 can additionally include a first bending portion 362 that positions the tab end portion segment 360 at an angle relative to the tab proximal segment 358. The tab end portion segment 360 can extend along a bending path to provide a curved interface surface 363. Accordingly, the tab terminal 334 provides a curved hook shape.

[0068] Figure 12 Another exemplary tab terminal 434 is shown that is shaped to optimize the electrical connection from the battery cell to the bus bar. The exemplary tab terminal 434 can include a tab proximal segment 458 that can be connected to the housing of the battery cell. The tab proximal segment 458 can be substantially straight along its length and can also include a first bending portion 480.

[0069] The tab terminal 434 may additionally include a second bend 462 that positions the tab end segment 460 at an angle relative to the tab proximal segment 458 to provide an alternative hook shape. The tab end segment 460 may include a proximal tip portion 466 and a distal tip portion 468, with the distal tip portion contacting the proximal tip portion 466 via a third bend 482. The distal tip portion 468 may be substantially straight to provide a straight interface surface 461. The proximal tip portion 466 may also be substantially straight.

[0070] Figure 13 Another exemplary tab terminal 534 is shown that is shaped to optimize the electrical connection from the battery cell to the bus bar. The exemplary tab terminal 534 may include a tab proximal segment 558 that can be connected to the housing of the battery cell. The tab proximal segment 558 may be substantially straight along its length and may also include a first bend 580.

[0071] The tab terminal 534 may additionally include a second bend 562 that positions the tab end segment 560 at an angle relative to the tab proximal segment 558 to provide another alternative hook shape. The tab end segment 560 may include a proximal tip portion 566 and a distal tip portion 568. The distal tip portion 568 may be angled relative to the proximal tip portion 566 via a third bend 582. The distal tip portion 568 may extend along a curved path to provide a curved interface surface 563.

[0072] The above-described exemplary tab terminal shape variations are designed to reduce weld-through and welding spatter issues by providing a local thickness increase at the tab end. Thus, the tab terminal can provide more consistent and accurate tab terminal to bus bar alignment and can also provide reduced welding errors, thereby improving manufacturing efficiency, reducing the need for welding repairs, and improving overall welding quality.

[0073] Although the different non-limiting embodiments are shown as having specific components or steps, the embodiments of the present disclosure are not limited to those specific combinations. Some components or features from any one of the non-limiting embodiments may be used in combination with features or components from any one of the other non-limiting embodiments.

[0074] It should be understood that the same reference numerals identify corresponding or similar elements in several of the figures. It should be understood that although specific component arrangements are disclosed and shown in these exemplary embodiments, other arrangements may also benefit from the teachings of the present disclosure.

[0075] The foregoing description should be construed as illustrative and not in any limiting sense. Those of ordinary skill in the art will understand that certain modifications may occur within the scope of the present disclosure. For these reasons, the appended claims should be studied to determine the true scope and content of the present disclosure.

Claims

1. A battery cell, comprising: a housing; and an ear terminal that protrudes outward from the housing, wherein the ear terminal includes an ear end segment having a shape that provides a local thickness increase, the local thickness increase being adapted to reduce welding spatter when welding the ear terminal to a bus bar.

2. The battery cell according to claim 1, wherein the shape includes a crimping edge that provides the local thickness increase at the ear end segment.

3. The battery cell according to claim 1 or 2, wherein the shape extends along a closed curved path that provides the local thickness increase at the ear end segment, and optionally, wherein the closed curved path establishes a convex shape of the ear end segment.

4. The battery cell according to any one of the preceding claims, wherein a first bend connects the ear end segment to an ear proximal segment of the ear terminal.

5. The battery cell according to claim 4, wherein a second bend connects a distal tip portion of the ear end segment to a proximal tip portion of the ear end segment.

6. The battery cell according to claim 5, wherein the distal tip portion folds around the second bend toward the proximal tip portion, and optionally, wherein the second bend establishes a crimping edge of the ear end segment.

7. The battery cell according to claim 4, wherein the second bend positions the distal tip portion of the ear end segment at an angle relative to the proximal tip portion of the ear end segment, and optionally, wherein the distal tip portion extends toward and is spaced apart from the ear proximal segment.

8. A traction battery pack, comprising: a bus bar that includes a slot and a weld joint backing structure disposed near the slot; the battery cell according to claim 1, wherein the ear terminal extends into the slot to a position adjacent to the weld joint backing structure; and a weld that fixes the ear terminal to the weld joint backing structure.

9. The traction battery pack according to claim 8, wherein the weld joint backing structure includes a crimping portion.

10. The traction battery pack according to claim 9, wherein a distal end segment of the ear terminal is received against an angled surface of the crimping portion, and optionally, wherein the distal end segment includes a crimping edge or extends along a closed curved path to establish a local thickness increase.

11. The traction battery pack according to any one of claims 8 to 10, wherein the weld joint backing structure includes a bent portion that is bent relative to a body of the bus bar.

12. The traction battery pack according to claim 11, wherein a distal end segment of the ear terminal is received against an angled surface of the bent portion, and optionally, wherein the distal end segment includes a crimping edge or extends along a closed curved path to establish a local thickness increase.

13. The traction battery pack according to any one of claims 8 to 12, wherein the tab terminal includes at least two bending portions.

14. The traction battery pack according to any one of claims 8 to 13, wherein the bus bar is made of a first metal material, and the tab terminal is made of a second metal material different from the first metal material.

15. A method for establishing an electrical connection between a battery cell and a bus bar, comprising: positioning the tab terminal of the battery cell to pass through a slot of the bus bar and into a position adjacent to a weld joint backing structure of the bus bar; and welding the tab terminal to the weld joint backing structure, wherein the tab terminal includes a shape that provides a local thickness increase within a tab end portion segment of the tab terminal for reducing welding spatter during welding.

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