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, 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 in projection 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 in projection in the plane of the electrochemical cell between a second junction edge with a second face of the electrochemical cell opposite to the first face and a second free end edge; the first tab has a first surface and the second tab has a second surface inferior to the first surface.Figure for the abridged version: 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 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 a battery having 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 these 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 assembly 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 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 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 to the first face and a second free end edge opposite to the second junction edge; The first tab has a first surface and the second tab has a second surface that is smaller than the first surface.

[0011] Various additional features may be provided, alone or in combination: - the second tab includes, in relation 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 tongue; - the second tab includes a second notch substantially symmetrical to the first notch with respect to a plane substantially perpendicular to the second edge of junction. - 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 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 over the electrical connecting bar, the second tab of the second electrochemical cell being folded over 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 includes a first laser weld 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 connecting bar; - the battery module further includes a second laser weld bead in an overlap area between said first tab and said second tab for welding the second tab to the first tab.

[0014] Thirdly, a method for electrically connecting a first electrochemical cell and a second electrochemical cell in a battery module as described above is proposed, 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; - application of a first laser weld 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 connecting bar; - application of 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 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:

[0016] Figure [Fig.1] schematically illustrates an electrochemical cell according to various embodiments;

[0017] Figure [Fig.2] schematically illustrates 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 an electrical connection process between two adjacent electrochemical cells of a battery module according to various embodiments.

[0020] With reference to [Fig. 1], an electrochemical cell 10 intended for integration into a battery module 30 is shown. This electrochemical cell 10 comprises 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".

[0021] As represented in [Fig.1], 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 junction edge 12 with a first face 14 of the electrochemical cell 10 and a first free end edge 13 opposite the first junction 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 projecting between a second junction edge 22 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. 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 in projection 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 that is 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 partially, but not completely, overlap, so that there is at least one area of ​​the first tab 11 that is not covered by the second tab 21.

[0026] In a non-limiting embodiment, the second tab 21 includes, in relation to the first tab 11, at least one first notch 25 (a cutout or a notch) such that the surface of the second tab 21 is less than the surface 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 includes the first notch 25.

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

[0028] In one embodiment, the first notch 25 is formed on a first edge connecting the second free end edge 23 to the second joining edge 22 of the second tongue 21. This first notch 25 extends at least partially along this first edge. Starting from the elongated shape of the tongues 11, 21, such a first notch 25 reduces the length of the second tongue 21 relative to that of the first tongue 11. The notch 25 can 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 that are substantially symmetrical with respect to a plane substantially perpendicular to the second junction edge 22. The symmetry of the second tab 21 with respect to said plane facilitates the orientation of the electrochemical cell 10 in either direction for its electrical connection with the adjacent electrochemical cell 10.

[0030] Referring to [Fig. 2], a portion of a battery module 30 is shown, comprising a plurality of electrochemical cells 10 arranged in a row (side by side 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 located on the displayed side of the battery module 30 are alternated. In other words, the electrochemical cells 10 are placed end-to-end, each pair of adjacent 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 used.

[0031] In one embodiment, the battery module 30 includes housings or, more generally, mechanical assembly means for receiving 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 arrangement using the electrical connection bars 31 by laser welding.

[0032] The electrical connecting bar 31 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 31 allows the tabs 11, 21 of two successive cells of the battery module 30 to be electrically connected. To this end, as illustrated in [Fig. 3], a first tab 11 of a first electrochemical cell 10 is bent onto the electrical connecting bar 32, and a second tab 21 of a second adjacent electrochemical cell 10 is bent 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-overlap zone between the two folded tabs 11, 21 (in other words, a zone 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, given that 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 a zone 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 the [Fig.4]) in said non-overlap zone of the first tab 11 to weld this first tab 11 to the electrical bonding bar 31.

[0034] The first tab 11 of the first electrochemical cell 10 is made of a first material comprising a first metal. The electrically bonding bar 31 is made of a second material comprising the first metal. In other words, the first tab 11 and the electrically bonding bar 31 share a common metal or both contain the same metal in their composition. This shared metal advantageously ensures better compatibility between the material of the first tab 11 and the material of the electrically bonding bar 31, 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 32.

[0035] In one embodiment, the common metal is predominant in the material of the first tab 11 and in the material of the electrically connecting bar 31. The term "predominant metal in a material" means a compound that 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 electrically connecting bar 31 are made of aluminum or copper, respectively, with different first and second levels of purity.In this case, the tab 11 and the electrical connection bar 31 have similar melting and thermal expansion properties, facilitating the creation of a first robust, reliable laser weld bead 32 without the risk of weld defects and / or cracking that can occur when welding elements with 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 connecting bar 31 makes it possible to produce a homogeneous and strong weld capable of withstanding the vibrations of the motor vehicle. This advantageously results in a stable and strong mechanical connection between the first tab 11 and the electrical connecting bar 31. Applying the first weld bead 32 with suitable laser power to weld the first tab 11 to the electrical connecting bar 31 allows, compared to welding the first tab 11, the second tab 21, and the electrical connecting bar 31 simultaneously, for their efficient assembly without the risk of creating a possible mixture of different materials.

[0037] More generally, applying a first weld bead 32 in the non-overlap zone of the first tab 11 to fix it to the electrical connecting bar 31 provides mechanical stability to the connection between the electrochemical cells and the electrical connecting bars 31, particularly against vehicle vibrations. Since these are two metallic elements, such a weld allows, well understood, also an electrical connection between the first tab 11 and the electrical connection bar 31.

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

[0039] It should be noted that welding the first tab 11 to the electrically connecting bar 31 and the second tab 21 to the first tab 11 does not require as much depth or, equivalently, as much welding energy as welding the second tab 21, the first tab 11, and the electrically connecting bar 31 simultaneously. Excessive energy input to the weld can thus be avoided.

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

[0041] A first weld bead 32 from the first tab 11 to the electrical connecting bar 31 and a second weld bead 33 from the first tab 11 to the first tab 11 allow the electrochemical cells 10 to be securely attached to the electrical connecting bar 31 and electrically connected. Furthermore, such a connection, involving an overlap of the tabs 11, 21, allows the use of a narrower electrical connecting bar 31. Advantageously, the need for an electrical connecting bar 31 wide enough to accommodate tabs 11, 21 on each side without overlap is no longer required. This results in a smaller overall size for the battery modules 30, 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.

[0042] In view of the foregoing, 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 connecting 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 weld 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 connecting bar 31. The first tab 11 and the electrical connecting bar 31 both comprise the same, preferably predominant, metal in their composition.A second weld bead 33 is also applied (step 53) in an overlap area between . the two tabs 11, 21 so as to weld the second tab 21 to the first tab 11.

Claims

1. Demands Battery module (30) comprising at least: - a first electrochemical cell (10) and a second electrochemical cell (10) each integrating a stack of electrodes separated from each other by a porous separating film, a first electrical connection terminal (1), a second electrical connection terminal (2) of opposite polarity to the first electrical connection terminal (1), the first electrical connection terminal (1) incorporating a first tab (11) extending in projection between a first junction edge (12) with a first face (14) of the electrochemical cell (10) and a first free end edge (13) opposite the first junction edge (12); the second electrical connection terminal (2) incorporating a second tab (21) extending in projection between a second junction edge (22) 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); the first tab (11) having a first surface and the second tab (21) having a second surface lower than the first surface, the second tab (21) comprising, with respect to the first tab (11), at least a first notch (25) or a first notch (25) and a second notch (26) substantially symmetric to the first notch (25) with respect to a plane substantially perpendicular to the second edge (22) of joining; - 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 over the electrical connecting bar (31), the second tab (21) of the second electrochemical cell (10) being folded over the first tab (11) of the first electrochemical cell; the battery module (30) being characterized in that it further comprises, -a first laser weld bead (32) in an area of ​​said first tab (11) of the first electrochemical cell (10) not covered by said second tab (21) of the second electrochemical cell (10) corresponding to the first notch (25) of this second tab (21) of the second electrochemical cell (10) or to the second notch (26) of this second tab (21) of the second electrochemical cell (10), to weld said first tab (11) of the first electrochemical cell (10) to the electrical bonding bar (31).

2. 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 connecting bar (31) being made of a second material comprising the first metal.

3. 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.

4. Battery module (30) according to any one of the preceding claims, characterized in that it further comprises a second laser weld bead (33) in an overlap zone between said first tab (11) of the first electrochemical cell (10) and said second tab (21) of the second electrochemical cell (10) for welding the second tab (21) of the second electrochemical cell (10) to the first tab (11) of the first electrochemical cell (10).

5. Battery module (30) according to any one of the preceding claims, 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).

6. Battery module (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.

7. A method for electrically connecting a first electrochemical cell (10) and a second electrochemical cell (10) in a battery module (30) according to any one of the preceding claims, comprising the following steps: - folding (5 1) of the first tab (11) of the first electrochemical cell (1 0) on an electrical bonding bar (3 1) and of the second tab (2 1) of the second electrochemical cell (1 0) on the first tab (11) of the first electrochemical cell (1 0); - application (5 2) of a first laser weld bead (3 2) in an area of ​​said first tab (1 1) of the first electrochemical cell (1 0) not covered by said second tab (2 1) of the second electrochemical cell (1 0) corresponding to the first notch (2 5) of this second tab (21) of the second electrochemical cell (10) or to the second notch (2 6) of this second tab (21) of the second electrochemical cell (10), to weld said first tab (1 1) of the first electrochemical cell (1 0) to the electrical bonding bar (3 1); - application (5 3) of a second laser weld bead ( 33) in an overlap area between said first tab ( 11) of the first electrochemical cell (1 0) and said second tab ( 21) of the second electrochemical cell (1 0) to weld the second tab ( 21) of the second electrochemical cell (1 0) to the first tab ( 11) of the first electrochemical cell (1 0).