Sealing gasket for electrochemical cell in a bag

Abstract

A bagged electrochemical cell comprising: - a casing including at least one negative electrode and one positive electrode separated by an insulating separator and an electrolyte; - a metallic electrical connection tab (2) electrically connected to the negative or positive electrode, said metallic tab protruding from the casing by means of a heat-sealed edge of the casing; - a sealing gasket (4) arranged between the metallic tab and the heat-sealed edge so that the casing is not in direct contact with the metallic tab, this sealing gasket including at least one beveled edge (42, 43). Figure for the abbreviation: Fig. 2

Description

Title of the invention: Sealing gasket for bagged electrochemical cell

[0001] The present invention relates to pouch electrochemical cells, also called pouch cells, flexible envelope cells or "Pouch cells" according to Anglo-Saxon terminology.

[0002] In a manner known from the prior art, a pouch-type electrochemical cell comprises an outer casing or pouch containing an alternating stack of negative and positive electrodes separated from each other by a porous separator film soaked in electrolyte. Two metallic electrical connection tabs, commonly called "tabs," connected to the electrodes of opposite polarities, protrude from the casing to serve as terminals for the electrical connections of the pouch electrochemical cell.

[0003] The casing is made of a flexible multilayer material, most often a combination of aluminum sheets and polymers. The inner face of this casing generally comprises, at least at its closing edges, a layer of thermoplastic polymer material.

[0004] Indeed, once the stack of electrodes fitted with the two metal electrical connection tabs and the electrolyte are placed in the envelope, the latter is closed by heat sealing (also called heat bonding) by pressing its edges between two heated jaws, allowing the two thermoplastic layers opposite each other to melt at the edges, thus thermally sealing the cell in a bag so as to leave only the two metal electrical connection tabs protruding.

[0005] To reinforce the sealing of the bag electrochemical cell, particularly at the edges where the metal tabs protrude from the envelope, a sealing gasket sandwiching each of the two metal tabs is often used.

[0006] This sealing gasket is designed to form a watertight barrier around the metal tab by being placed between the tab and the edges of the envelope on either side of the metal tab. It is made, on the one hand, of a thermoplastic material to ensure cohesion with the inner layer of the envelope during heat sealing, and, on the other hand, is adhesive to guarantee a hermetic bond with the metal tab.

[0007] When applied to a metal strip, the sealing gasket consists of two rectangular strips sandwiching the metal strip and joining against each other (i.e., overlapping) beyond its edges. By extending beyond the edges of the metal strip, the extensions or The "wings" of the sealing strips (i.e., the portions covering the areas immediately adjacent to the metal tab) ensure increased sealing and retention of the metal tab in position.

[0008] However, a drawback of current sealing gaskets is that during heat sealing of the envelope edges, the part of the gasket, particularly the corner portion, located inside the envelope, risks, under the effect of heat: - deforming, possibly creating sharp corners that could compromise the integrity of the surrounding elements; and / or - to release compounds inside the casing, which may come into contact with the stack of electrodes and possibly cause a short circuit and / or alter the chemical properties of the electrolyte.

[0009] One object of the present invention is to overcome the aforementioned disadvantages.

[0010] Another object of the present invention is to prevent any external contamination likely to disrupt the conditions intended in a sachet electrochemical cell.

[0011] For this purpose, an electrochemical cell in a sachet is proposed comprising - an envelope including at least one negative electrode and one positive electrode separated by an insulating separator and an electrolyte; - a metal electrical connection tab electrically connected to the negative or positive electrode, said metal tab protruding from the casing by a heat-sealed edge of the casing, at least one sealing gasket arranged between the metal tab and the heat-sealed edge so that the casing is not in direct contact with the metal tab, cell in which the sealing gasket includes at least one beveled edge.

[0012] Various additional features may be provided, alone or in combination: - the sealing gasket comprises a first part having a first distal edge, said first part being arranged inside the envelope and a second part comprising a second distal edge, said second part being arranged outside the envelope, said sealing gasket comprising lateral edges connecting the first distal edge to the second distal edge; - only the side edges are beveled; - a first lateral edge of said lateral edges includes a first portion which extends in the continuation of the first distal edge, said first portion defining with the first distal edge, a first angle between 115 degrees and 160 degrees, said first angle being measured in the clockwise direction; - the first lateral border includes a second portion which extends in the continuation of the first portion and in the continuation of the second distal border, said second portion defining an angle substantially perpendicular to the second distal border or the first lateral border includes only a first portion which extends in a straight line from the first distal border to the second distal border; - a second lateral edge of said lateral edges includes a third portion which extends in the continuation of the first distal edge, said third portion defining with the first distal edge, a second angle between -115 degrees and -160 degrees, said second angle being measured in the clockwise direction; - the second lateral border includes a fourth portion which extends in the continuation of the third portion and in the continuation of the second distal border, said fourth portion defining an angle substantially perpendicular to the second distal border or the second lateral border includes only a third portion which extends in a straight line from the first distal border to the second distal border; - the sealing gasket defines: a first point of intersection between the first distal edge and the first or third portion, and a second point of intersection between the second distal edge and the first or third portion, or a third point of intersection between the first portion and the second portion or between the third portion and the fourth portion; - the first point of intersection, the second point of intersection and / or the third point of intersection are rounded. - the first portion has a length measured from the first point of intersection, and the second point of intersection or the third point of intersection, said length being measured along a first axis substantially parallel to the first and second distal edges, said length being between 1 millimeter and 4 millimeters; - the first portion has a height measured from the first point of intersection, and the second point of intersection or the third point of intersection, said height being measured along a second axis substantially perpendicular to the first and second distal edges, said height being between 0.5 millimeters and 3 millimeters; - the first point of intersection is arranged at a distance of at least 1 millimeter from the metal tab, said distance being measured along a first axis substantially parallel to the first and second distal edges.

[0013] 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:

[0014] Figure [Fig.1] schematically illustrates a sachet electrochemical cell according to various embodiments;

[0015] Figure [Fig.2] schematically illustrates a sealing gasket enclosing a metal tab according to various embodiments.

[0016] With reference to [Fig.1], an electrochemical cell 10 in a sachet is shown comprising an envelope 1 integrating an electrolyte and at least one negative electrode and one positive electrode separated by an insulating separator (not shown for clarity).

[0017] A metal electrical connection tab 2 is electrically connected to either the negative or positive electrode. This metal tab 2 protrudes from the casing 1 by means of a heat-sealed edge 3. For the sake of simplicity, only one metal tab 2 is shown, but the electrochemical cell 10 naturally includes a second metal electrical connection tab connected to the second electrode. The two metal tabs may protrude from the casing 1 by means of the same heat-sealed edge 3 or by means of different heat-sealed edges.

[0018] A sealing gasket 4 is arranged between the metal tab 2 and the heat-sealed edge 3 so that the casing 1 is not in direct contact with the metal tab 2. The sealing gasket 4 is interposed between the casing 1 and the metal tab 2. Thanks to the sealing gasket 4, the metal tab 2 protrudes in a sealed manner through the heat-sealed edge 3 of the casing 1. In one embodiment, the sealing gasket 4 is made of a thermoplastic material, such as polypropylene.

[0019] The edge 3 of the casing is heat-sealed around the metal tab 2 by means of the sealing gasket 4. This sealing gasket 4 comprises, in one embodiment, a first strip and a second strip sandwiching the metal tab 2 and joining against each other beyond the edges of the metal tab 2 so as to form a first extension of the sealing gasket 4 and a second extension of the sealing gasket 4 on either side of the metal tab 2. More generally, the metal tab 2 is wrapped or sandwiched by the sealing gasket 4, which extends on either side of the metal tab 2 in the form of wings or extensions.

[0020] Referring to [Fig. 2], the sealing gasket 4 comprises at least one beveled edge 42, 43. Advantageously, this results in a reduction of the extent of the sealing gasket material 4, which otherwise could lead to an undesirable release of compounds inside, particularly under the effect of heat. of the electrochemical cell. A beveled edge 42, 43 is less likely to deform under the effect of heat, which helps to further limit the release of undesirable compounds inside the envelope 1. Thus, a beveled configuration of at least one edge 42, 43 of the sealing joint 4 advantageously reduces the risks of release / detachment of substances that could disturb the intended conditions (e.g., the chemical properties of the electrolyte) in the bagged electrochemical cell 10.

[0021] The sealing gasket 4 has an outer contour in the shape of a convex polygon. All interior angles of the outer contour of the sealing gasket 4 have a measure of less than 180 degrees.

[0022] In one embodiment, the sealing gasket 4 comprises two beveled edges 42, 43. These two beveled edges 42, 43 are located on either side of the metal tab 2, at a predetermined distance from it. In one embodiment, the two beveled edges 42, 43 are substantially symmetrical with respect to a plane perpendicular to the heat-sealed edge 3 of the casing 1.

[0023] In one embodiment, the sealing gasket 4 comprises - a first part comprising a first distal edge 40, this first portion being arranged inside envelope 1; and - a second part comprising a second distal edge 41, this second part being arranged outside envelope 1.

[0024] Lateral edges 42-45 connect the first distal edge 40 to the second distal edge 41. In one embodiment, only the lateral edges 42-45 are beveled. Since they are not in contact with the metal tab 2, substances are more likely to detach from the unbeveled lateral edges. When only the lateral edges 42-45 are beveled, this reduces the risk of contamination of the inside of the casing 1 without affecting the performance of the sealing gasket 4.

[0025] In one embodiment, a first lateral edge 42 of the sealing gasket 4 comprises a first portion 42 extending in line with the first distal edge 40. The first portion 42 defines with the first distal edge 40 a first angle 46 between 115 degrees and 160 degrees, this first angle 46 being measured clockwise.

[0026] The first lateral edge 42, 44 comprises a second portion 44 which extends in line with the first portion 42 and with the second distal edge 41. The second portion 44 forms a substantially perpendicular angle with the second distal edge 41. In another embodiment (not shown), the first lateral edge 42, 44 comprises only a first portion 42 which extends straight from the first distal edge 40 to the second distal edge 41.

[0027] A second lateral edge 43, 45 of the sealing gasket 4 includes a third portion 43 which extends in line with the first distal edge 40. The third portion 43 defines with the first distal edge 40 a second angle 47 between -115 degrees and -160 degrees, this second angle 47 being measured in a clockwise direction.

[0028] The second lateral edge 43, 45 comprises a fourth portion 45 which extends in line with the third portion 43 and the distal second edge 41. The fourth portion 45 forms a substantially perpendicular angle with the distal second edge 41. In another embodiment (not shown), the second lateral edge 43, 45 comprises only a third portion 43 which extends straight from the distal first edge 40 to the distal second edge 41.

[0029] Moving away from the metal tab 2, the first lateral edge 42, 44 and / or the second lateral edge 43, 45 move closer to the second distal edge 41. Advantageously, the portion of the sealing gasket 4 that is likely to deform first under the effect of heat, and from which compounds can detach, is cut out.

[0030] In the embodiment illustrated in [Fig. 2], the sealing joint 4 defines: - a first point of intersection between the first distal edge 40 and the first portion 42 or the third portion 43, and - a second point of intersection between the second distal edge 41 and the first portion 42 or the third portion 43, or - a third point of intersection between the first portion 42 and the second portion 44 or between the third portion 43 and the fourth portion 45.

[0031] The first, second, and / or third points of intersection are preferably rounded (i.e., smoothed instead of having sharp angles or angular points). A rounded contour without angular points helps to reduce stresses that may occur at the points of intersection due to heat.

[0032] The first portion 42 (respectively, the third portion 43) has a length 48 measured from the first point of intersection, and the second or third point of intersection. This length, measured along a first axis substantially parallel to the first and second distal edges 40, 41, is between 1 millimeter and 4 millimeters.

[0033] The first (respectively, the third) portion 42 has a height 49, measured from the first point of intersection, and the second or third point of intersection, of between 0.5 millimeters and 3 millimeters. This height 49 is measured along a second axis substantially perpendicular to the first and second distal edges 40, 41. The dimensions of the length 48 and the height 49 advantageously allow the extent of the sealing joint 4 to be reduced to the inside of the envelope 1 without risk to the sealing of the exit of the metallic tab 2 through the heat-sealed edge 3.

[0034] The first point of intersection is positioned at a distance 50 equal to 1 millimeter from the metal tab 2. This distance 50 is measured along a first axis substantially parallel to the first and second distal edges 40, 41. A minimum distance 50 between the beveled edge 42, 43 and the sandwiching of the metal tab 2 by the sealing gasket 4 is thus ensured so as not to affect the sealing of the exit of the metal tab 2 through the heat-sealed edge 3.

Claims

Demands

1. Electrochemical cell (10) in a bag comprising - a casing (1) including at least one negative electrode and one positive electrode separated by an insulating separator and an electrolyte; - a metallic electrical connection tab (2) electrically connected to the negative or positive electrode, said metallic tab (2) protruding from the casing (1) by a heat-sealed edge (3) of the casing (1); - a sealing gasket (4) arranged between the metallic tab (2) and the heat-sealed edge (3) so that the casing (1) is not in direct contact with the metallic tab (2), cell (10) in which, the sealing gasket (4) includes at least one beveled edge (42, 43).

2. Electrochemical cell (10) in a sachet according to the preceding claim, characterized in that the sealing seal (4) comprises a first part having a first distal edge (40), said first part being arranged inside the envelope (1), and a second part comprising a second distal edge (41), said second part being arranged outside the envelope (1), said sealing seal (4) comprising lateral edges (42-45) connecting the first distal edge (40) to the second distal edge (41).

3. Electrochemical cell (10) in a sachet according to the preceding claim, characterized in that only the lateral edges (42-45) are beveled.

4. Electrochemical cell (10) in a sachet according to claim 2 or 3, characterized in that a first lateral edge (42, 44) of said lateral edges (42-45) comprises a first portion (42) which extends in the continuation of the first distal edge (40), said first portion (42) defining with the first distal edge (40) a first angle (46) between 115 degrees and 160 degrees, said first angle being measured in the clockwise direction.

5. Electrochemical cell (10) in a sachet according to the preceding claim, characterized in that the first lateral edge (42, 44) comprises a second portion (44) which extends in the continuation of the first portion (42) and in the continuation of the second distal edge (41), said second portion (44) defining an angle substantially perpendicular with the second distal edge (41) or the first lateral edge (42, 44) comprises only a first portion (42) which extends in a straight line from the first distal edge (40) to the second distal edge (41).

6. Electrochemical cell (10) in a sachet according to any one of claims 2 to 5, characterized in that a second lateral edge (43, 45) of said lateral edges (42-45) comprises a third portion (43) which extends in the continuation of the first distal edge (40), said third portion (43) defining with the first distal edge (40) a second angle (47) between -115 degrees and -160 degrees, said first angle being measured in the clockwise direction.

7. Electrochemical cell (10) in a sachet according to the preceding claim, characterized in that the second lateral edge (43, 45) comprises a fourth portion (45) which extends in the continuation of the third portion (43) and in the continuation of the second distal edge (41), said fourth portion (45) defining a substantially perpendicular angle with the second distal edge (41) or the second lateral edge (43, 45) comprises only a third portion (43) which extends in a straight line from the first distal edge (40) to the second distal edge (41).

8. Bag electrochemical cell (10) according to the preceding claim, characterized in that the sealing joint (4) defines: - a first point of intersection between the first distal edge (40) and the first portion (42) or the third portion (43), and - a second point of intersection between the second distal edge (41) and the first portion (42) or the third portion (43), or - a third point of intersection between the first portion (42) and the second portion (44) or between the third portion (43) and the fourth portion (45).

9. Electrochemical cell (10) in a sachet according to the preceding claim, characterized in that the first point of intersection, the second point of intersection and / or the third point of intersection are rounded.

10. Electrochemical cell (10) in a sachet according to claim 8 or 9, characterized in that the first portion (42) has a length (48) measured from the first point of intersection, and the second point of intersection or the third point of intersection, said length (48) being measured along a first axis substantially parallel to the first and second distal edges, said length (48) being between 1 millimeter and 4 millimeters.

11. Bag electrochemical cell (10) according to any one of claims 8 to 10, characterized in that the first portion (42) has a height (49) measured from the first point of intersection, and the second point of intersection or the third point of intersection, said height (49) being measured along a second axis substantially perpendicular to the first and second distal edges, said height (49) being between 0.5 millimeters and 3 millimeters.

12. Bag electrochemical cell (10) according to any one of claims 8 to 11, characterized in that the first point of intersection is arranged at a distance (50) at least equal to 1 millimeter from the metal tab (2), said distance being measured along a first axis substantially parallel to the first and second distal edges.

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