Method for manufacturing an electrochemical pouch cell

Abstract

The invention relates to a method for manufacturing a pouch cell, which method comprises the following steps: - forming a first cavity (11) and a second cavity (12) in a multilayer film (20), the first cavity and the second cavity having a common edge (13) incorporating a fold line (14) allowing the first cavity (11) to be folded over the second cavity (12) so as to form a pouch capable of receiving a stack of electrodes; - forming a first semi-cylindrical gutter (15) in the edge of the first cavity (11) and a second semi-cylindrical gutter (16) in the edge of the second cavity (12) such that, when the first cavity (11) is folded over the second cavity (12), the second gutter (16) and the first gutter (15) together form a duct (17) capable of receiving a cable extending into the pouch.

Description

Method for manufacturing a sachet electrochemical cell

[0001] The present invention relates to the technical field of pouch electrochemical cells, also known as soft-shell electrochemical cells or "pouch cells" according to Anglo-Saxon terminology. In particular, the present invention relates to a method for manufacturing pouch electrochemical cells and the cells thus obtained.

[0002] According to 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.

[0003] The casing is most often formed by heat-sealing the edges of two multilayer films or strips, each with a thermoplastic layer on its inner face, placed opposite each other. The casing is hermetically sealed so that only a positive and a negative terminal, connected to the corresponding electrodes, protrude.

[0004] To reduce the edges requiring heat sealing and thus improve the envelope's airtightness, it is known that the envelope is pre-formed as a double sheet incorporating two identical cavities on either side of a fold line. When folded over each other, the two cavities together form an envelope designed to receive the stack of electrodes and the electrolyte.

[0005] Real-time monitoring of the condition of a pouch-type cell in a battery module is crucial for various reasons, including the safety, performance, and / or lifespan of that cell. To achieve this, it is common practice to install sensors or probes directly on or near the pouch cells, such as temperature sensors, pressure sensors, electrochemical sensors, or gas and leak detectors.

[0006] However, a drawback of existing solutions is that the measurements taken lack relevance and do not accurately reflect the condition of Pouch-type cells. Furthermore, the specific design of these cells presents unique challenges for monitoring their condition and performance.

[0007] Therefore, there is a need to collect measurements as close as possible to the sachet cells for closer and more precise monitoring.

[0008] An object of the present invention is to propose methods for manufacturing cells in sachets allowing precise and continuous monitoring of the state of these cells, without compromising their integrity.

[0009] To this end, it is proposed, firstly, a method for manufacturing a sachet electrochemical cell comprising the following steps:- formation, in a multilayer film, of a first cavity and a second cavity substantially identical, the first cavity and the second cavity having a common edge incorporating a fold line allowing the first cavity to be folded over the second cavity so as to form a sachet suitable for receiving a stack of electrodes;- formation of a first semi-cylindrical channel in the edge of the first cavity outside of said common edge, this first channel being communicative with the first cavity;- formation of a second semi-cylindrical channel substantially identical to the first channel in the edge of the second cavity outside of said common edge so that, when the first cavity is folded over the second cavity along the folding line, the second channel is substantially opposite the first channel and forms with this first channel a conduit suitable for receiving a predefined cable extending into said bag; - arrangement of said stack of electrodes in the second cavity; - folding of the first cavity over the second cavity; - arrangement of said cable in the conduit formed by the first and second channels previously formed; - fixing of the edge of the first cavity to the edge of the second cavity outside of said common edge, said cable already being arranged in the conduit previously formed.

[0010] Various additional features may be provided, alone or in combination: - the first semi-cylindrical chute has a substantially semi-circular or substantially semi-elliptical cross-section; - the first semi-cylindrical chute is less deep than the first cavity; - the first cavity, the second cavity, the first semi-cylindrical chute and / or the second semi-cylindrical chute are formed by stamping, between a male mold and a female mold, the multilayer film; - the first cavity, the second cavity, the first chute and the second chute are formed simultaneously; - the edge of the first cavity is fixed, outside of said common edge, to the edge of the second cavity by heat sealing.

[0011] Secondly, a sachet electrochemical cell is proposed, which can be obtained by the manufacturing process described above.

[0012] Various additional features may be provided, alone or in combination: - the cable includes a temperature sensor, a pressure sensor, a gas detector, or an electrochemical sensor; - said cable includes a thermocouple cable; - the cable includes a thermoplastic coating at least on its external face intended to be in contact with the first chute and with the second chute.

[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] The figure schematically illustrates the steps of a manufacturing process for a sachet electrochemical cell according to various embodiments;

[0015] The figure schematically illustrates the preforming steps of a multilayer film for the manufacture of a sachet electrochemical cell according to various embodiments;

[0016] The figure schematically illustrates the implementation of a manufacturing step of a sachet electrochemical cell according to various embodiments;

[0017] The figure schematically illustrates a side view of a sachet electrochemical cell according to various embodiments.

[0018] Referring to the attached figures, a process10 for manufacturing a sachet electrochemical cell includes a step1 of forming, in a multilayer film20, a first cavity11 and a second cavity12 substantially identical.

[0019] The first cavity 11 and the second cavity 12 share a common edge 13 incorporating a fold line 14, allowing, as illustrated in Figures 2 and 3, the first cavity 11 to be folded over the second cavity 12 to form a pouch 21 suitable for receiving a stack of electrodes. When folded over each other along the fold line 14, the two cavities 11 and 12 together define or delimit a volume to house the stack of electrodes.

[0020] The first cavity 11 and the second cavity 12 are contiguous along a common edge 13, incorporating a fold line 14 allowing the cavities 11, 12 to be folded over each other. The edges of the two cavities 11, 12 align perfectly when these two cavities 11, 12 are folded over each other. These edges refer to the outer limits of the cavities 11, 12 (where they meet the plane of the multilayer film 20) or to the peripheral area immediately around the opening of the two cavities 11, 12.

[0021] The fold line 14 delimits the two cavities 11, 12, which are substantially symmetrical with respect to this fold line 14. The approximately rectangular profile of the cavities 11, 12 is for illustrative purposes only and is not intended to be limiting.

[0022] In one embodiment, the multilayer film 20 comprises, from the outside to the inside of the bag 21 formed by the two cavities 11, 12, an electrically insulating protective outer layer (for example, made of plastic), a metallic intermediate layer (in particular, made of aluminum or an aluminum-based alloy) and an inner layer made of thermoplastic material (for example, made of polypropylene).

[0023] The process 10 for manufacturing the electrochemical cell further comprises a step 2 of forming a first semi-cylindrical channel 15 in the edge of the first cavity 11 outside the common edge 13. The first semi-cylindrical channel 15 communicates with the first cavity 11. The first semi-cylindrical channel 15 opens into the interior of the first cavity 11.

[0024] A step 3 is also provided for the formation of a second semi-cylindrical chute 16 substantially identical to the first semi-cylindrical chute 15 in the edge of the second cavity 12 outside the common edge 13 so that, when the first cavity 11 is folded over the second cavity 12 along the folding line 14, the second semi-cylindrical chute 16 is substantially opposite the first semi-cylindrical chute 15 and forms with this first semi-cylindrical chute 15 a conduit 17 suitable for receiving a predefined cable extending into the bag 21.

[0025] Advantageously, the two semi-cylindrical channels 15, 16 formed in the edges of the two cavities 11, 12 symmetrically with respect to the folding line 14 together form a conduit 17 designed to receive a cable extending inside the electrochemical cell. The integration of a sensor inside the bagged electrochemical cell is thus possible without compromising its integrity, including its airtightness. This conduit 17 allows the sensor to be integrated inside the bagged electrochemical cell without risk of swelling or an increase in its thickness.

[0026] In one embodiment, the first semi-cylindrical conduit 15 has a substantially semi-circular or substantially semi-elliptical cross-section. Advantageously, this results in a conduit 17 suitable for tightly fitting a cable with a round or flattened cross-section (in particular, a ribbon cable). This results in a reduction of the risk of voids between the edges of the bag 21 and the outer surface of the cable.

[0027] The first semi-cylindrical channel 15 is preferably less deep than the first cavity 11. It follows advantageously that the two channels 15, 16 form a conduit 17 less wide (or less thick) than the bagged electrochemical cell, without impacting the integrity of the latter.

[0028] The first cavity 11, the second cavity 12, the first semi-cylindrical chute 15, and / or the second semi-cylindrical chute 16 are, in one embodiment, formed by stamping the multilayer film 20 between a male and a female mold. Such preforming allows for a high production rate. Here, "stamping" refers to any manufacturing operation performed by deforming the material, whether hot or cold.

[0029] For even faster preforming of the multilayer film20, the first cavity11, the second cavity12, the first semi-cylindrical channel15 and the second semi-cylindrical channel16 can be formed simultaneously (or concomitantly) by stamping.

[0030] Following the preforming of the first cavity 11, the second cavity 12, the first semi-cylindrical channel 15, and / or the second semi-cylindrical channel 16, a stack of electrodes (not shown) is arranged (step 4 of arrangement in the figure) in the second cavity 12. The first cavity 11 is then folded (step 5 of folding, illustrated by arrow 30 in the figure) over the second cavity 12. The two cavities 11 and 12 are folded symmetrically onto each other, that is, folded or brought over each other so that they align symmetrically opposite each other around the folding line 14. This results in a pouch-shaped electrochemical cell in the form of a roughly parallelepiped-shaped envelope of low thickness.

[0031] A cable can be placed (step 6) in the conduit 17 formed by the first semi-cylindrical channel 15 and the second semi-cylindrical channel 16 previously formed. This cable can, of course, be placed in either the first or the second semi-cylindrical channel 15, 16 before the first cavity 11 is folded down onto the second cavity 12. This cable passes through the edge of the electrochemical cell so as to protrude on one side outside the bag 21, and on the other side inside the volume defined by the bag 21 in which the stack of electrodes is placed.

[0032] Various parameters of the bagged electrochemical cell can thus be measured, particularly during each charging or discharging cycle. In one embodiment, the cable includes a temperature sensor, a pressure sensor, a gas detector, or an electrochemical sensor. In another embodiment, the cable includes a thermocouple cable for thermal monitoring of the bagged electrochemical cell.

[0033] The edge of the first cavity 11 is fixed (step 7 in the diagram) to the edge of the second cavity 12 outside the common edge 13, the cable already being positioned (step 6 in the diagram) in the previously formed conduit 17. Advantageously, the prior formation of the conduit 17 using the two semi-cylindrical ducts 15, 16 and the placement of a cable in it, before fixing the edges of the two cavities 11, 12, ensures a reliable seal at the cable entry. By placing the cable in a pre-formed conduit, the fixing of the edges of the two cavities 11, 12 is carried out uniformly around this cable, without risk of gaps or pinching. This results in a reinforced seal, with a homogeneous and airtight closure around the cable, also ensuring its safety. In addition, a pre-formed conduit 17 allows for precise positioning of the cable and prevents any movement during the fixing step 7.

[0034] Heat sealing provides an advantageous and rapid joining of the two facing edges and a watertight closure of the bag 21. In one embodiment, the bag 21 is presented under two heated jaws of a heat sealing device incorporating two recesses (or two channels) substantially identical to the channels 15, 16 forming the conduit 17.

[0035] The bagged electrochemical cell is resealed, notably by heat sealing, so that only the cable arranged in the conduit and, of course, the electrical terminations (not shown) connected to the oppositely polarized electrodes of the stack to form the terminals of the bagged electrochemical cell protrude from the bag. For the introduction of a liquid electrolyte into the bag, a portion of the bag's edge can be heat-sealed after filling.

[0036] In one embodiment, the cable comprises a thermoplastic coating (such as polypropylene or polyethylene) at least on its outer face intended to be in contact with the first semi-cylindrical chute 15 and with the second semi-cylindrical chute 16. This coating allows the cable to pass watertight through the edge of the bag 21.

[0037] The advantageous result is a sachet electrochemical cell whose operation can be monitored precisely and continuously, without compromising its integrity.

Claims

Method (10) of manufacturing a sachet electrochemical cell comprising the following steps:- formation (1), in a multilayer film (20), of a first cavity (11) and a second cavity (12) substantially identical, the first cavity and the second cavity having a common edge (13) incorporating a fold line (14) allowing the first cavity (11) to be folded over the second cavity (12) so as to form a sachet (21) suitable for receiving a stack of electrodes;- formation (2) of a first semi-cylindrical channel (15) in the edge of the first cavity (11) outside said common edge (13), this first channel (15) being communicative with the first cavity (11);- formation (3) of a second semi-cylindrical channel (16) substantially identical to the first channel (15) in the edge of the second cavity (12) outside said edge (13) in common so that, when the first cavity (11) is folded over the second cavity (12) along the folding line (14), the second channel (16) is substantially opposite the first channel (15) and forms with this first channel (15) a conduit (17) suitable for receiving a predefined cable extending in said bag (21);- arrangement (4) of said stack of electrodes in the second cavity (12);- folding (5) of the first cavity (11) over the second cavity (12);- arrangement (6) of said cable in the conduit (17) formed by the first channel (15) and the second channel (16) previously formed;- fixing (7) of the edge of the first cavity (11) to the edge of the second cavity (12) outside said edge (13) in common, said cable being already arranged in the conduit (17) previously formed.; Manufacturing method according to the preceding claim, characterized in that the first semi-cylindrical chute (15) has a substantially semi-circular or substantially semi-elliptical cross-section. Manufacturing method according to claim 1 or 2, characterized in that the first semi-cylindrical chute (15) is less deep than the first cavity (11). A manufacturing method according to any one of the preceding claims, characterized in that the first cavity (11), the second cavity (12), the first semi-cylindrical chute (15) and / or the second semi-cylindrical chute (16) are formed by stamping, between a male mold and a female mold, the multilayer film (20). Manufacturing method according to the preceding claim, characterized in that the first cavity (11), the second cavity (12), the first chute (15) and the second chute (16) are formed simultaneously. A manufacturing method according to any one of the preceding claims, characterized in that the edge of the first cavity (11) is fixed, outside of said edge (13) in common, to the edge of the second cavity (12) by heat sealing. Electrochemical cell in a sachet that can be obtained by the manufacturing process of any one of the preceding claims. Electrochemical cell according to the preceding claim, characterized in that the cable comprises a temperature sensor, a pressure sensor, a gas detector, or an electrochemical sensor. Electrochemical cell according to claim 7 or 8, characterized in that said cable comprises a thermocouple cable. Electrochemical cell according to any one of claims 7 to 9, characterized in that the cable comprises a thermoplastic coating at least on its external face intended to be in contact with the first chute (15) and with the second chute (16).

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