Electrochemical cells and battery modules incorporating such cells

Abstract

An electrochemical cell incorporating a stack of electrodes separated from each other by a porous separating film, this electrochemical cell comprising: - a first edge incorporating a first edge portion intended to be aligned with a first electrical connecting bar for electrically connecting the electrochemical cell to an adjacent electrochemical cell in a battery module; - a first electrical connecting tab of a first polarity extending from said first edge and intended to be connected to the first electrical connecting bar, this first electrical connecting tab having a variable length along the first edge portion, this length being measured perpendicular to the first edge portion. Figure for the abbreviation: Fig. 1

Description

Title of the invention: Electrochemical cells and battery module integrating 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 powered by electric battery propulsion energy. The invention also relates to electrical modules comprising such cells.

[0002] An electric battery intended to equip a hybrid or electric vehicle comprises several modules integrating a plurality of electrochemical cells mechanically assembled to one another 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 in the same row of a battery module is ensured by an electrical connection plate or bar, commonly called a "busbar" according to Anglo-Saxon terminology. This electrical connection bar, made of 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 bent against the electrical connecting bar and welded to it. Indeed, a common method for electrically connecting two adjacent electrochemical cells in a battery module consists of positioning an electrical connecting bar so that it extends between the two electrical connecting tabs opposite two adjacent electrochemical cells, bending the electrical connecting tabs onto the electrical connecting bar, and laser welding each electrical connecting tab to the electrical connecting bar.

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

[0006] However, such an electrical connecting bar does not provide complete satisfaction, particularly due to its dimensions. An inherent drawback of the connecting bar The downside of using electric batteries is that they increase the size and weight of the battery modules, in addition to their manufacturing cost due to the amount 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 connecting bar for a simple and compact series or parallel arrangement 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, it is proposed, firstly, an electrochemical cell integrating a stack of electrodes separated from each other by a porous separating film, this electrochemical cell comprising - a first edge incorporating a first part of edge intended to be opposite a first electrical connecting bar to electrically connect the electrochemical cell to an adjacent electrochemical cell in a battery module; - a first electrical connection tab of a first polarity extending from said first edge and intended to be connected to the first electrical connecting bar, this first electrical connection tab having a variable length along the first part of edge, this length being measured perpendicular to the first part of edge.

[0011] Various additional features may be provided, alone or in combination: - the first electrical connection tab includes a section that is substantially rectangular or triangular in shape; - the electrochemically cell further comprises a second edge opposite the first edge incorporating a second edge part intended to be opposite a second electrical connecting bar to electrically connect the electrochemical cell to an adjacent electrochemical cell; a second electrical connecting tab of a second polarity opposite to the first polarity extending from said second edge and intended to be connected to the second electrical connecting bar, this second tab being substantially symmetrical to the first tab with respect to a median plane of the electrochemical cell; - the electrochemical cell also includes, a second edge opposite the first edge incorporating a second edge part intended to be opposite a second electrical connecting bar to electrically connect the electrochemical cell to an adjacent electrochemical cell; a second electrical connecting tab of a second polarity opposite to the first polarity extending from said second edge and intended to be connected to the second electrical connecting bar, this second tab being substantially symmetrical to the first tab with respect to a central axis of the electrochemical cell; The stack of electrodes is arranged in a flexible bag, the cell also including an electrolyte in the bag.

[0012] Secondly, a battery module is proposed comprising at least: - a first electrochemical cell according to the invention; a second electrochemical cell according to the invention; - an electrical connecting bar for electrically connecting the first electrochemical cell and the second electrochemical cell, the first tab of the first electrochemical cell extending, when connected to the electrical connecting bar, beyond the mid-width of this electrical connecting bar along at least a portion of the first edge part.

[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 includes a first laser weld bead in an area of ​​the first tab of the first electrochemical cell not covered by a tab of the second electrochemical cell to weld the first tab of the first electrochemical cell to the electrical bonding bar.

[0014] Other features and advantages of the invention will become clearer and more concrete upon reading the following description of embodiments, which is made with reference to the accompanying drawings in which:

[0015] Figure [Fig.1] schematically illustrates an electrochemical cell incorporating electrical connection tabs according to a general embodiment;

[0016] Figure [Fig.2] schematically illustrates an electrochemical cell incorporating electrical connection tabs according to a first embodiment;

[0017] Figure [Fig.3] schematically illustrates an electrochemical cell incorporating electrical connection tabs according to a second embodiment;

[0018] Figure [Fig.4] schematically illustrates part of a battery module according to various embodiments;

[0019] Figure [Fig.5] schematically illustrates an electrical connecting bar electrically connecting two adjacent electrochemical cells in a battery module according to a first embodiment;

[0020] Figure [Fig.6] schematically illustrates an electrical connecting bar electrically connecting two adjacent electrochemical cells in a battery module according to a second embodiment.

[0021] With reference to Figures 1-3, an electrochemical cell 10 intended for integration into a battery module 20 is shown. This electrochemical cell 10 incorporates a stack of electrodes separated from each other by a porous separator film. The electrode stack is arranged (or wrapped) in a flexible pouch containing an electrolyte. The electrochemical cell 10 can, in fact, be a pouch cell or a flexible-packaged cell, commonly called a "pouch".

[0022] The electrochemical cell 10 comprises a first edge 1. This first edge 1 refers to an outer area or peripheral region that at least partially delimits the electrode stack. A first portion 2 of the first edge 1 is intended to be opposite a first electrical connecting bar 3 for electrically connecting the electrochemical cell 10 to an adjacent electrochemical cell 10 in the battery module 20.

[0023] Housings or, more generally, mechanical assembly means are most often provided in the battery module 20 to receive the electrochemical cell 10 so that the first edge portion 2 is aligned with a first electrical connecting bar 3. Here, the term "aligned" means that the first edge portion 2 is the portion of the first edge 1 closest to the first electrical connecting bar 3 when the electrochemical cell 10 is arranged in the battery module 20. In one embodiment, the first edge portion 2 has a length substantially equal to or slightly less than the length of the first electrical connecting bar 3.

[0024] The electrochemical cell 10 further comprises a first electrical connection tab 4 of a first polarity. This first tab 4 forms, for example, the positive or negative electrical connection terminal of the electrochemical cell 10. The first electrical connection tab 4 protrudes or extends beyond the first edge 1. The first electrical connection tab 4 is intended to be connected to the first electrical connecting bar 3.

[0025] The first electrical connection tab 4 has a variable or different length (or depth) along the first edge portion 2. “Variable” or “different” indicates that this length is not constant, as highlighted, in particular, in [Fig. 1]. This length is measured perpendicular to the first edge portion 2. In other words, the first tab 4 has a variable extent along the first edge portion 2 in a direction substantially perpendicular to the first edge portion 2.

[0026] The length of the first electrical connection tab 4 along the first edge portion 2 relates to its dimension extending beyond the first edge portion 2. The length of the first tab 4 varies along the first edge portion 2. More generally, the first electrical connection tab 4 is not uniformly long along the first edge portion 2.

[0027] A tab having a variable or different length along the first edge portion 2 means that the distance of the tab measured perpendicularly to the first edge portion 2 varies at different points along this first edge portion 2. In other words, the first electrical connection tab 4 does not have a uniform depth but exhibits variations in length along the first edge portion 2.

[0028] Advantageously, the first electrical connection tab 4 may have a length of zero at certain points along the first edge portion 2, as illustrated in [Fig. 3]. For example, the first electrical connection tab 4 partially runs along the first edge portion 2, with the length of the first electrical connection tab 4 being zero along at least a portion of the first edge portion 2. By having a different length along the first edge portion 2, the contour of the first electrical connection tab 4 varies, creating, for example, a triangular shape, an L-shape, a pointed shape (a tab that is longer in the center and narrows towards the ends, as in the example in [Fig. 5]), a rectangular shape with at least one notch (cutout or notch), or a combination of these shapes.

[0029] In embodiments illustrated by figures 2 and 3, the first electrical connection tab 4 comprises a section of substantially rectangular or triangular shape.

[0030] Advantageously, electrochemical cells 10, each incorporating a first electrical connection tab 4 of variable length along the corresponding first edge portion 2, allow for the arrangement, at the level of an electrical connecting bar 3, of electrical connection tabs 4, 14 of complementary shapes (i.e., whose combination creates a complete and uniform geometric shape, in this case, a rectangle) or partially overlapping shapes. As will be detailed below- Furthermore, such arrangements of the electrical connection tabs 4,14 at the electrical connection bars 3 advantageously allow the use of compact (in particular, narrower) electrical connection bars 3. These arrangements of the electrical connection tabs 4,14 also prevent intermetallic mixing that could occur during simultaneous welding of the two electrical connection tabs 4,14 and the electrical connection bar 3, which could compromise the quality of the electrical and mechanical connection between the electrochemical cells 10.

[0031] The electrochemical cell 10 comprises a second edge 11 opposite the first edge 1, incorporating a second edge portion 12 intended to be aligned with a second electrical connecting bar 3 for electrically connecting the electrochemical cell 10 to an adjacent electrochemical cell. A second electrical connecting tab 14 of a second polarity opposite to the first polarity protrudes from the second edge 11. This second electrical connecting tab 14 is intended to be connected to a second electrical connecting bar 3. The first tab 4 and the second electrical connecting tab 14 extend inward in the plane of the electrochemical cell 10.

[0032] In the embodiment illustrated in [Fig. 1], the first tab 4 has a first surface and the second tab 14 has a second surface different from the first surface. In other words, the electrochemical cell 10 comprises a first tab 4 and a second tab 14 forming two electrical connection terminals of opposite polarity, the two tabs 4, 14 having different surfaces. It follows that, when they are superimposed, one of the two electrical connection tabs 4, 14 partially covers the other. In other words, when the first tab 4 and the second tab 14 are superimposed, they partially overlap, but not completely.

[0033] In another embodiment illustrated by [Fig. 2], the second electrical connection tab 14 is substantially symmetrical to the first tab 4 with respect to a median plane 15 of the electrochemical cell 10. Such an arrangement of the electrical connection tabs 4, 14 can advantageously be considered for a series connection of the electrochemical cells 10.

[0034] In another embodiment illustrated by [Fig. 3], the second electrical connection tab 14 is substantially symmetrical to the first electrical connection tab 4 with respect to a central axis 16 of the electrochemical cell. Such an arrangement of the electrical connection tabs 4, 14 can advantageously be considered for a parallel connection of the electrochemical cells 10.

[0035] Referring to [Fig. 4], a portion of a battery module 20 is shown, comprising a plurality of electrochemical cells 10 arranged in a row (one (alongside each other in a connection direction) and whose electrical connection tabs 4, 14 are electrically connected to each other by means of electrical connecting bars 3. The electrochemical cells 10 are arranged in the battery module 20 so that their electrical connection tabs 4, 14 can be electrically connected to each other in a series or parallel arrangement using the electrical connecting bars 3 by laser welding. In a battery module 20, several stacked or juxtaposed rows of electrochemical cells 10 can, of course, be envisaged.

[0036] The electrical connecting bar 3 comprises an elongated body made of an electrically conductive material (in particular, copper, aluminum, or an alloy thereof) extending between two adjacent electrochemical cells 10. Each electrical connecting bar 3 allows the electrical contact of the electrical connection tabs 4, 14 of two successive electrochemical cells 10 in the battery module 20.

[0037] In one embodiment, at least one of the two electrical connection tabs 4,14 extends, when connected to the electrical connecting bar 3, beyond the mid-width of the electrical connecting bar 3 along at least a portion of the first edge section 2. Thus, a partial overlap or geometric complementarity of two tabs 4,14 can advantageously be achieved at the electrical connecting bar 3. Complementary or partially overlapping tabs 4,14 advantageously allow the use of a compact electrical connecting bar 3 and improve the weld quality of these tabs 4,14 to the electrical connecting bar 3.

[0038] As illustrated in Figures 5-6, the electrical connection tabs 4,14 of two adjacent electrochemical cells 10 in the battery module 20 are folded over the electrical connection bar 3. Advantageously, due to the shape of one or both of the electrical connection tabs 4,14 and their arrangement on the electrical connection bar 3, there is an area of ​​at least one of the two electrical connection tabs 4,14 not covered by the other electrical connection tab 4,14. In other words, there is a non-overlapping area between the two tabs 4,14 folded over the electrical connection bar 3.

[0039] To fix the electrical connection tabs 4,14 to the electrical connection bar 3, a first bead 31 (a point or a line) of laser welding is applied in a non-overlapping area of ​​the two tabs 4,14 so as to weld one of the two tabs 4,14 to the electrical connection bar 3.

[0040] In one embodiment, a tab 4,14 of the first electrochemical cell 10 is made of a first material comprising a first metal. The electrically connecting bar 3 is made of a second material comprising the first metal. In other words, a tab 4, 14 and the electrically connecting bar 3 share a common metal or both contain the same metal in their composition. This common metal advantageously ensures better compatibility between the material of the tab 4, 14 and the material of the electrically connecting bar 3, leading to improved structural integrity of the weld. This advantageously results in a reduction of the risk of cracking or weld defects and, consequently, a more robust and reliable first weld bead 31.

[0041] In one embodiment, the common metal is predominant in the material of the tab 4, 14 and in the material of the electrically connecting bar 3.The term "predominant metal in a material" refers to a compound that represents the largest quantity by weight among the material's compounds; in other words, the compound constituting the main or most abundant component of the material in question. For example, the first tab 4 and the electrical connecting bar 3 are made of aluminum or copper, respectively, with different first and second purity levels. In this case, the tab 4 and the electrical connecting bar 3 exhibit similar melting and thermal expansion properties, facilitating the creation of a robust and reliable first laser weld bead 31, free from the risk of weld defects and / or cracking that can occur when welding elements with different melting and / or thermal expansion properties.

[0042] Advantageously, a predominant common metal in the material of the tab 4, 14 and in the material of the electrical connecting bar 3 makes it possible to achieve a homogeneous and strong weld capable of withstanding the vibrations of the motor vehicle. This advantageously results in a stable and solid mechanical connection between the tab 4, 14 and the electrical connecting bar 3. Applying the first weld bead 31 with suitable laser power to weld the tab 4, 14 to the electrical connecting bar 3 allows, compared to welding the first tab 4, the second tab 14, and the electrical connecting bar 3 simultaneously, for their efficient assembly without the risk of creating a possible mixture of different materials.

[0043] More generally, applying a first weld bead 31 in the non-overlap zone of a tab 4,14 to fix it to the electrical connecting bar 3 provides mechanical stability to the connection between the electrochemical cells and the electrical connecting bars 3, particularly against vehicle vibrations. Since both are metallic elements, such a weld also allows, of course, an electrical connection between the tab 4,14 and the electrical connecting bar 3.

[0044] In the case of a partial overlap between the two tabs 4,14 bent on the electrical connecting bar 3 (see [Fig.5]), a second laser welding bead 32 can be applied in this overlap area to weld the two tabs 4,14.

[0045] It should be noted that each of the first weld bead 31 and the second weld bead 32 does not require as much welding energy as welding both tabs 4, 14 and the electrical connecting bar 3 simultaneously. Excessive energy input to the weld can thus be avoided.

[0046] Advantageously, the embodiments described above prevent intermetallic mixing that could occur during welding of the second tab 14, the first tab 4, and the electrical connecting bar 3, and which could compromise the quality of the electrical and mechanical connection between the electrochemical cells 10. The weld beads 31, 32 securely attach the electrochemical cells 10 to the electrical connecting bar 3 and connect them electrically.

[0047] Furthermore, the need for an electrical connection bar 3 wide enough to receive tabs 4,14 on each side without overlap is advantageously no longer required. This results in a smaller footprint for the battery modules 20, so that an increase in the number of electrochemical cells 10 per battery module can be considered to improve the overall power of the vehicle.

Claims

Demands

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 edge (1) incorporating a first edge portion (2) intended to be opposite a first electrical connecting bar (3) for electrically connecting the electrochemical cell (10) to an adjacent electrochemical cell in a battery module (20); - a first electrical connecting tab (4) of a first polarity extending from said first edge (1) and intended to be connected to the first electrical connecting bar (3), this first electrical connecting tab (4) having a variable length along the first edge portion (2), this length being measured perpendicular to the first edge portion (2).

2. Electrochemical cell according to the preceding claim, characterized in that the first electrical connection tab (4) comprises a section of substantially rectangular or triangular shape.

3. Electrochemical cell according to claim 1 or 2, characterized in that it comprises - a second edge (11) opposite the first edge (1) incorporating a second edge portion (12) intended to be opposite a second electrical connecting bar (3) for electrically connecting the electrochemical cell (10) to an adjacent electrochemical cell; - a second electrical connecting tab (14) of a second polarity opposite to the first polarity extending from said second edge (11) and intended to be connected to the second electrical connecting bar (3), this second tab (14) being substantially symmetrical to the first tab (4) with respect to a median plane (15) of the electrochemical cell (10).

4. Electrochemical cell according to claim 1 or 2, characterized in that it comprises - a second edge (11) opposite the first edge (1) incorporating a second edge portion (12) intended to be opposite a second electrical connecting bar (3) for connection electrically the electrochemical cell (10) to an adjacent electrochemical cell; - a second electrical connection tab (14) of a second polarity opposite to the first polarity extending from said second edge (11) and intended to be connected to the second electrical connection bar (3), this second tab (14) being substantially symmetric to the first tab (4) with respect to a central axis (16) of the electrochemical cell (10).

5. Electrochemical cell 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 (20) 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 (3) for electrically connecting the first electrochemical cell (10) and the second electrochemical cell (10), the first tab (4) of the first electrochemical cell (10) extending, when connected to the electrical connecting bar (3), beyond the mid-width of this electrical connecting bar (3) along at least a portion of the first edge part (2).

7. Battery module according to the preceding claim, characterized in that the first tab (4) of the first electrochemical cell (10) is made of a first material comprising a first metal, the electrical bonding bar (3) being made of a second material comprising the first metal.

8. Battery module 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 according to any one of claims 6 to 8, characterized in that it further comprises a first laser weld bead (31) in an area of ​​the first tab (4) of the first electrochemical cell not covered by a tab of the second electrochemical cell (10) for welding the first tab (4) of the first electrochemical cell (10) to the electrical bonding bar (3).

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