Electrochemical cells and battery modules incorporating such cells

Abstract

Electrochemical cell incorporating a stack of electrodes separated from each other by a porous separator film, comprising a first electrical connection terminal, a second electrical connection terminal of opposite polarity to the first electrical connection terminal, - the first electrical connection terminal incorporating a first tab extending projecting in the plane of the electrochemical cell between a first junction edge with a first face of the electrochemical cell and a first free end edge; - the second electrical connection terminal incorporating a second tab extending projecting in the plane of the electrochemical cell between a second junction edge with a second face of the electrochemical cell opposite the first face and a second free end edge; the first tab has a first surface and the second tab has a second surface lower than the first surface.Figure for abstract: Fig.1.

Description

Title of the invention: Electrochemical cells and battery modules incorporating such cells

[0001] The present invention relates to electrochemical cells, and more particularly to the electrical connection of such cells in a battery module intended to equip a motor vehicle at least partially supplied with propulsion energy by electric battery. The invention also relates to electrical modules comprising such cells.

[0002] An electric battery intended to equip a hybrid or electric vehicle comprises a battery comprising several modules integrating a plurality of electrochemical cells mechanically assembled to each other in one or more rows and electrically connected to each other in series or in parallel.

[0003] The electrical connection between two adjacent electrochemical cells of the same row of a battery module is provided by an electrical connection plate or bar, usually called a "busbar" according to English terminology. This electrical connection bar formed from a conductive material connects the electrical connection terminals (or poles) of two adjacent electrochemical cells.

[0004] Each of the electrical connection terminals is in the form of a flexible metal strip or, more generally, a tab, commonly called a "tab" in English, intended to be folded against the electrical connection bar and welded thereto. Indeed, a common method for electrically connecting two adjacent electrochemical cells in a battery module consists of arranging an electrical connection bar so that it extends between the two electrical connection tabs facing two adjacent electrochemical cells, folding these electrical connection tabs onto the electrical connection bar, and laser welding each electrical connection tab onto the electrical connection bar.

[0005] The electrical connection bar is provided to be sufficiently wide (along a connection direction between the two electrochemical cells) to receive the two electrical connection terminals each separately and without overlapping one on the other. Most often, the electrical connection bar comprises two parts and each of the two parts is welded to one of the two connection tabs, so as to electrically connect the two adjacent electrochemical cells, without overlapping of the two tabs on the electrical connection bar.

[0006] However, such an electrical connecting bar does not provide complete satisfaction, in particular due to its dimensions. A disadvantage inherent in the connecting bar electric is that it increases the size and weight of the battery modules, in addition to its manufacturing cost due to the quantity of material used.

[0007] An object of the present invention is to ensure reliable electrical connections between the connection terminals of the electrochemical cells of a battery module, while reducing the size of the battery modules.

[0008] Another object of the present invention is to propose an electrochemical cell allowing the use of a narrow electrical connection bar for simple and space-saving series mounting of electrochemical cells.

[0009] Another object of the present invention is to improve the overall performance of hybrid or electric vehicles.

[0010] To this end, there is proposed, firstly, an electrochemical cell integrating a stack of electrodes separated from each other by a porous separator film, this electrochemical cell comprising a first electrical connection terminal, a second electrical connection terminal of polarity opposite to the first electrical connection terminal, - the first electrical connection terminal incorporating a first tab extending in projection between a first junction edge with a first face of the electrochemical cell and a first free end edge opposite the first junction edge; - the second electrical connection terminal incorporating a second tab extending in projection between a second junction edge with a second face of the electrochemical cell opposite the first face and a second free end edge opposite the second junction edge; the first tab has a first surface and the second tab has a second surface less than the first surface.

[0011] Various additional features may be provided, alone or in combination: - the second tab comprises, relative to the first tab, at least one first notch; - the first notch is made on a first edge connecting the second free end edge to the second joining edge of the second tab; - the second tab comprises a second notch substantially symmetrical to the first notch relative to a plane substantially perpendicular to the second joining edge. - the electrode stack is arranged in a flexible bag, the cell further comprising an electrolyte in the bag.

[0012] Secondly, a battery module is proposed comprising at least: - a first electrochemical cell as presented above; - a second electrochemical cell as presented above; - an electrical connecting bar electrically connecting in series the first electrochemical cell and the second electrochemical cell, the first tab of the first electrochemical cell being folded onto the electrical connecting bar, the second tab of the second electrochemical cell being folded onto the first tab of the first cell.

[0013] Various additional features may be provided, alone or in combination: - the first tab of the first electrochemical cell is made of a first material comprising a first metal, the electrical connecting bar being made of a second material comprising the first metal; - the first metal is predominant in the first material and in the second material; - the battery module further comprises a first laser welding bead in an area of ​​said first tab not covered by said second tab corresponding to the first notch and / or the second notch, for welding said first tab to the electrical connection bar; - the battery module further comprises a second laser weld bead in an overlapping area between said first tab and said second tab for welding the second tab to the first tab.

[0014] Thirdly, there is provided a method of electrical connection between a first electrochemical cell and a second electrochemical cell in a battery module as presented above, this method comprising the following steps: - folding the first tab of the first electrochemical cell onto an electrical connecting bar and the second tab of the second electrochemical cell onto the first tab of the first electrochemical cell; - applying a first laser welding bead in an area of ​​said first tab not covered by said second tab corresponding to the first notch and / or the second notch, to weld said first tab to the electrical connection bar; - applying a second laser weld bead in an overlap area between said first tab and said second tab to weld the second tab to the first tab.

[0015] Other characteristics and advantages of the invention will appear more clearly and concretely on reading the following description of embodiments, which is given with reference to the appended drawings in which:

[0016] Figure [Fig.l] schematically illustrates an electrochemical cell according to various embodiments;

[0017] Figure [Fig.2] schematically illustrates a part of a battery module according to various embodiments;

[0018] Figure [Fig.3] schematically illustrates an electrical connection between two adjacent electrochemical cells of a battery module according to various embodiments;

[0019] Figure [Fig.4] schematically illustrates steps of a method of electrical connection between two adjacent electrochemical cells of a battery module according to various embodiments.

[0020] Referring to [Fig.l], an electrochemical cell 10 is shown intended to be integrated into a battery module 30. This electrochemical cell 10 comprises a stack of electrodes separated from each other by a porous separator film. The stack of electrodes is arranged (or wrapped) in a flexible pouch comprising an electrolyte. The electrochemical cell 10 may, in fact, be a pouch cell or a flexible packaging cell, commonly called a “Pouch”.

[0021] As shown in [Fig.l], the electrochemical cell 10 comprises a first electrical connection terminal 1 (or pole) and a second electrical connection terminal 2 of opposite polarity to the first electrical connection terminal 1.

[0022] The first electrical connection terminal 1 comprises a first tab 11 extending in projection between a first edge 12 for joining with a first face 14 of the electrochemical cell 10 and a first free end edge 13 opposite the first joining edge 12. The first tab 11 forms, for example, the positive electrical connection terminal of the electrochemical cell 10. The first tab 11 is, in one embodiment, made of aluminum.

[0023] The second electrical connection terminal 2 comprises a second tab 21 extending in projection between a second edge 22 for joining with a second face 24 of the electrochemical cell 10 opposite the first face 14 and a second free end edge 23 opposite the second joining edge 22. The second tab 21 forms, for example, the negative electrical connection terminal of the electrochemical cell 10. The second tab 21 is, in one embodiment, made of copper, nickel or nickel-plated copper.

[0024] More generally, the first electrical connection terminal 1 and the second electrical connection terminal 2 are in the form of flexible tabs 11, 21 protruding from two opposite faces 14, 24 of the parallelepiped shape of the electrochemical cell 10. The first tab 11 and the second tab 21 extend projecting into the plane of the electrochemical cell 10.

[0025] The first tab 11 has a first surface and the second tab 21 has a second surface smaller than the first surface. In other words, the electrochemical cell 10 comprises a first tab 11 and a second tab 21 forming two electrical connection terminals 1, 2 of opposite polarity, the two tabs 11, 21 having different surfaces. It follows that, when they are superimposed, the second tab 21 partially covers the first tab 11. In other words, when the first tab 11 and the second tab 21 are superimposed, they overlap partially, but not completely, so that there is at least one area of ​​the first tab 11 which is not covered by the second tab 21.

[0026] In a non-limiting embodiment, the second tab 21 comprises, relative to the first tab 11, at least one first notch 25 (a cutout or a notch) so that the surface area of ​​the second tab 21 is smaller than the surface area of ​​the first tab 11. In other words, when comparing the second tab 21 to the first tab 11, the second tab 21 differs at least in that it comprises the first notch 25.

[0027] A non-overlapping (or non-overlapping) zone of the first tab 11 and the second tab 21 when they are superimposed comprises at least the first notch 25. Thus, when they are superimposed, the first tab 11 and the second tab do not overlap at least at the level of the first notch 25 provided in the second tab 21.

[0028] The first notch 25 is, in one embodiment, made on a first edge connecting the second free end edge 23 to the second joining edge 22 of the second tab 21. This first notch 25 extends at least partially over this first edge. Starting from the elongated shape of the tabs 11, 21, such a first notch 25 reduces the length of the second tab 21 relative to that of the first tab 11. The notch 25 may be of any suitable shape such as rectangular, square, circular, triangular, oval or polygonal.

[0029] In a non-limiting embodiment illustrated by Figures 1-3, the second tab 21 comprises a first notch 25 and a second notch 26 substantially symmetrical with respect to a plane substantially perpendicular to the second joining edge 22. A symmetry of the second tab 21 with respect to said plane makes it easier to arrange the electrochemical cell 10 in one direction as in the other for its electrical connection with the neighboring electrochemical cell 10.

[0030] Referring to [Fig.2], there is shown a part of a battery module 30 comprising a plurality of electrochemical cells 10 arranged in a row (one next to the other in a connection direction) and whose tabs 11, 21 are electrically connected to each other by means of electrical connection bars 31. In this example, the electrochemical cells 10 of the battery module 30 are connected to each other in series. The polarities of the connection terminals 1, 2 arranged on the displayed side of the battery module 30 are alternated. In other words, the electrochemical cells 10 are juxtaposed head to tail, each pair of contiguous tabs 11, 21 on the same side of the battery module 30 belonging to two adjacent electrochemical cells 10 having opposite polarities. In a battery module 30, several stacked or juxtaposed rows of electrochemical cells 10 can, of course, be envisaged.

[0031] In one embodiment, the battery module 30 comprises housings or, more generally, mechanical assembly means intended to receive the electrochemical cells 10, these means being arranged to assemble the electrochemical cells 10 so that their electrical connection terminals 1, 2 can be electrically connected to each other in a series assembly using the electrical connection bars 31 by laser welding.

[0032] The electrical connection bar 31 comprises an elongated body made of an electrically conductive material (in particular, copper, aluminum or an alloy thereof) which extends between two adjacent electrochemical cells 10. Each electrical connection bar 31 makes it possible to bring the tabs 11, 21 of two successive cells of the battery module 30 into electrical contact. For this, as illustrated in [Fig. 3], a first tab 11 of a first electrochemical cell 10 is folded onto the electrical connection bar 32 and a second tab 21 of a second neighboring electrochemical cell 10 is folded onto the first tab 11 of the first electrochemical cell 10 (step 51 in [Fig. 4]).Due to the difference between the surface area of ​​the first tab 11 and that of the second tab 21, there is a non-overlapping area between the two folded tabs 11, 21 (in other words, an area where the two surfaces do not overlap) corresponding to the first notch 25 and / or the second notch 26. More generally, the second tab 21 partially covers the first tab 11. More generally, since the surface area of ​​a first tab 11 of a first electrochemical cell 10 is greater than the surface area of ​​a second tab 21 of a neighboring second electrochemical cell 10, there is an area of ​​the first tab 11 of the first electrochemical cell 10 not covered by the second tab 21 or which does not overlap the second tab 21 of the neighboring second electrochemical cell.

[0033] A first bead 32 (a point or a line) of laser welding is applied (step 52 in [Fig.4]) in said non-overlapping zone of the first tab 11 to weld this first tab 11 to the electrical connection bar 31.

[0034] The first tab 11 of the first electrochemical cell 10 is made of a first material comprising a first metal. The electrical connection bar 31 is made of a second material comprising the first metal. In other words, the first tab 11 and the electrical connection bar 31 have a metal in common or both contain the same metal in their composition. This common metal advantageously ensures better compatibility between the material of the first tab 11 and the material of the electrical connection bar 31, leading to better structural integrity of the weld. This advantageously results in a reduction in the risks of cracking or weld defects and, consequently, a more robust and reliable first weld bead 32.

[0035] In one embodiment, the common metal is predominant in the material of the first tab 11 and in the material of the electrical connection bar 31. The term "predominant metal in a material" means a compound which represents the largest quantity by weight among the compounds of the material, in other words the compound constituting the main or most abundant component of the material in question. For example, the first tab 11 and the electrical connection bar 31 are based on aluminum or copper with, respectively, a first level of purity and a second level of purity which are different.In this case, the tab 11 and the electrical connection bar 31 have similar melting and thermal expansion properties, promoting the production of a first laser welding bead 32 that is robust, reliable and without risks of welding defects and / or cracking likely to occur when welding elements having different melting and / or thermal expansion properties.

[0036] Advantageously, a predominant common metal in the material of the tab 11 and in the material of the electrical connection bar 31 makes it possible to produce a homogeneous and solid weld capable of withstanding the vibrations of the motor vehicle. This advantageously results in a stable and solid mechanical connection between the first tab 11 and the electrical connection bar 31. The application of the first welding bead 32 with a suitable laser power for welding the first tab 11 to the electrical connection bar 31 makes it possible, compared to welding both the first tab 11, the second tab 21 and the electrical connection bar 31, to assemble them efficiently without the risk of creating a possible mixture of different materials.

[0037] More generally, the application of a first weld bead 32 in the non-overlapping zone of the first tab 11 to fix it to the electrical connection bar 31 provides mechanical stability to the connection between the electrochemical cells and the electrical connection bars 31, in particular in the face of vibrations of the vehicle. Since these are two metal elements, such welding allows, although heard, also an electrical connection between the first tab 11 and the electrical connection bar 31.

[0038] .A second laser welding bead 33 is applied (step 53 in [Fig.4]) to the second tab 21 to weld it to the first tab 11 in an overlapping area between the two tabs 11, 21.

[0039] It should be noted that welding the first tab 11 to the electrical connection bar 31 and the second tab 21 to the first tab 11 does not require as much depth or, equivalently, welding energy as welding both the second tab 21, the first tab 11 and the electrical connection bar 31. An input of too much energy to the weld can, thus, be avoided.

[0040] Advantageously, the embodiments presented above make it possible to avoid an intermetallic mixture likely to occur during welding of both the second tab 21, the first tab 11 and the electrical connection bar 31 and which may compromise the quality of the electrical and mechanical connection between the electrochemical cells 10.

[0041] A first weld bead 32 from the first tab 11 to the electrical connection bar 31 and a second weld bead 33 from the first tab 11 to the first tab 11 make it possible to securely fix the electrochemical cells 10 to the electrical connection bar 31 and to connect them electrically. Furthermore, such a connection involving an overlap of the tabs 11, 21 makes it possible to use an electrical connection bar 31 of smaller width. The need for an electrical connection bar 31 sufficiently wide to receive on each side and without overlapping the tabs 11, 21 is, advantageously, no longer required. This results in a smaller footprint of the battery modules 30 so that an increase in the number of electrochemical cells 10 per battery module can be envisaged to improve the overall power of the vehicle.

[0042] In view of the above, an electrical connection between two adjacent electrochemical cells 10 in a battery module 30 comprises a step 51 of folding the first tab 11 of the first electrochemical cell 10 onto the electrical connection bar 31 and the second tab 21 of the second electrochemical cell 10 onto the first tab 11 of the first electrochemical cell. A first laser welding bead 32 is then applied (step 52) in a non-overlapping area of ​​the first tab 11 between the two tabs 11, 21 (corresponding to the first notch 25 and / or the second notch 26) so as to weld the first tab 11 to the electrical connection bar 31. The first tab 11 and the electrical connection bar 31 both comprise the same metal, preferably predominant, in their composition.A second weld bead 33 is also applied (step 53) in an overlapping area between . the two tabs 11, 21 so as to weld the second tab 21 to the first tab 11.

Claims

Claims

1. Electrochemical cell (10) incorporating a stack of electrodes separated from each other by a porous separator film, this electrochemical cell (10) comprising a first electrical connection terminal (1), a second electrical connection terminal (2) of polarity opposite to the first electrical connection terminal (1), - the first electrical connection terminal (1) incorporating a first tab (11) extending in projection between a first edge (12) for joining with a first face (14) of the electrochemical cell (10) and a first free end edge (13) opposite the first joining edge (12); - the second electrical connection terminal (2) incorporating a second tab (21) extending projecting between a second edge (22) of junction with a second face (24) of the electrochemical cell (10) opposite the first face (14) and a second free end edge (23) opposite the second junction edge (22);this electrochemical cell (10) being characterized in that the first tab (11) has a first surface and the second tab (21) has a second surface smaller than the first surface.;

2. Electrochemical cell (10) according to the preceding claim, characterized in that the second tab (21) comprises, relative to the first tab (11), at least one first notch (25).

3. Electrochemical cell (10) according to the preceding claim, characterized in that the first notch (25) is made on a first edge connecting the second free end edge (23) to the second junction edge (22) of the second tab (21).

4. Electrochemical cell (10) according to claim 2 or 3, characterized in that the second tab (21) comprises a second notch (26) substantially symmetrical to the first notch (25) relative to a plane substantially perpendicular to the second junction edge (22).

5. Electrochemical cell (10) according to any one of the preceding claims, characterized in that the stack of electrodes is arranged in a flexible bag, the cell further comprising an electrolyte in the bag.

6. Battery module (30) comprising at least: - a first electrochemical cell (10) according to any one of the preceding claims; - a second electrochemical cell (10) according to any one of the preceding claims; - an electrical connecting bar (31) electrically connecting in series the first electrochemical cell and the second electrochemical cell (10), the first tab (11) of the first electrochemical cell (10) being folded onto the electrical connecting bar (31), the second tab (21) of the second electrochemical cell (10) being folded onto the first tab (11) of the first cell.

7. Battery module (30) according to the preceding claim, characterized in that the first tab (11) of the first electrochemical cell (10) is made of a first material comprising a first metal, the electrical connection bar (31) being made of a second material comprising the first metal.

8. Battery module (30) according to the preceding claim, characterized in that the first metal is predominant in the first material and in the second material.

9. Battery module (30) according to any one of claims 6 to 8, characterized in that it further comprises a first laser welding bead (32) in an area of ​​said first tab (11) not covered by said second tab (21) corresponding to the first notch (25) of this second tab (21) of the second electrochemical cell (10) according to any one of claims 2 to 5 and / or to the second notch (26) of this second tab (21) of the second electrochemical cell (10) according to claims 4 or 5, for welding said first tab (11) to the electrical connection bar (31).

10. Battery module (30) according to the preceding claim, characterized in that it further comprises a second laser welding bead (33) in an overlapping area between said first tab (11) and said second tab (21) for welding the second tab (21) to the first tab (11).

11. Method of electrical connection between a first electrochemical cell (10) and a second electrochemical cell (10) in a battery module (30) according to claim 9 or 10, comprising the following steps: - folding (51) of the first tab (11) of the first cell (10) electrochemical on an electrical connection bar (31) and the second tab (21) of the second electrochemical cell (10) on the first tab (11) of the first electrochemical cell (10); - application (52) of a first laser welding bead (32) in an area of ​​said first tab (11) not covered by said second tab (21) corresponding to the first notch (25) and / or to the second notch (26), to weld said first tab (H) to the electrical connection bar (31); - applying (53) a second laser welding bead (33) in an overlapping area between said first tab (11) and said second tab (21) to weld the second tab (21) to the first tab (11).

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