DE102021208034A1 - Process for manufacturing an energy cell and energy cell - Google Patents

Abstract

A method for producing an energy cell (6) is specified, the energy cell (6) having a cell stack (12) and at least one conductor (10) which is connected to the cell stack (12), the energy cell (6) having a cell housing (4), which has at least two housing parts (2), namely a first housing part (2) and a second housing part (2), the housing parts (2) being assembled in such a way that they enclose the cell stack (12) and that the conductor (10) protrudes from the cell housing (4), the housing parts (2) being connected to one another by arranging an adhesive (8) between the housing parts (2), for gluing the housing parts (2) to one another, the adhesive (8) is arranged in such a way that it also extends over the arrester (10), so that the arrester (10) is also glued to the housing parts (2). A corresponding energy cell (6) is also specified.

Description

The invention relates to a method for producing an energy cell and a corresponding energy cell.

The energy cell is a pouch cell, for example. In principle, other designs are also conceivable, e.g. a prismatic cell or a round cell. The energy cell is used, for example, in a battery for a vehicle with an electric drive. When the vehicle is being driven, the electric drive is supplied with energy from the battery.

The energy cell has a cell stack and a cell housing into which the cell stack is inserted. The cell stack typically includes multiple anode layers, cathode layers, and separator layers. The anode layers on the one hand and the cathode layers on the other hand are each connected to a conductor. The two conductors lead out of the cell housing and thus each form an electrical connection for the energy cell, one for a positive pole and one for a negative pole. The cell stack, on the other hand, is completely enclosed within the cell housing.

The energy cell is produced, for example, by first producing the cell stack and attaching the conductors to it. Two half-shells of the cell housing are also produced. The cell stack is then inserted into the cell housing so that the two half-shells are arranged around and enclose the cell stack. However, the conductors protrude from the cell housing. The cell housing is then closed in a heat-sealing process (also referred to as "hot sealing"), at least partially and especially in the area of the arresters. A heat-sealed seam is created along the cell housing and across the arresters, which connects the two half-shells to one another. However, the conductors lie between the two half-shells and prevent the half-shells from being directly connected to one another there. Rather, in the area of a respective arrester, this very arrester is connected on both sides to a half-shell.

During the heat-sealing process, the cell housing is not yet completely closed, but an opening remains for filling with an electrolyte. After the heat-sealing process, the cell housing is then filled with electrolyte, which wets the cell stack (so-called "wetting"). Finally, the cell housing is completely closed. This is followed by conditioning, during which gas is produced in the cell housing, which is collected in a gas pocket in the cell housing. After conditioning, the gas pocket is separated and the cell housing is sealed again with a heat sealing process. Finally, aging takes place (also referred to as "aging"), during which the fully assembled energy cell is exposed to an increased temperature for a certain period of time. After aging and a possible final inspection, the energy cell is finished.

In general, it is desirable for the cell housing to be as tight as possible, i.e. to have as good a seal as possible, specifically to prevent electrolyte from escaping from the interior of the energy cell to the outside. With regard to the tightness of the cell housing, the arresters represent a weak point, since the cell housing is necessarily perforated here in order to provide an electrical contact to the outside. The transition that occurs at the edge of the arrester and where the heat-sealed seam transitions from a connection of one half-shell to the arrester on the one hand and the two half-shells to one another on the other hand is particularly problematic.

Against this background, it is an object of the invention to specify an improved manufacturing method for an energy cell. The energy cell produced using the method should have as high a level of tightness as possible. A corresponding energy cell is also to be specified.

The object is achieved according to the invention by a method having the features according to claim 1 and by an energy cell having the features according to claim 10. Advantageous refinements, developments and variants are the subject matter of the dependent claims. The explanations in connection with the method also apply to the energy cell and vice versa. A power cell according to the invention is preferably manufactured according to the method.

A core idea of the present invention is in particular to connect two housing parts of a cell housing of an energy cell with an additional adhesive in order to obtain improved tightness. In other words: two housing parts of a cell housing of an energy cell are connected particularly tightly by means of an adhesive connection. In a preferred embodiment, the two housing parts are two half-shells of an energy cell, which is designed as a pouch cell.

The method is used to produce an energy cell. The power cell is preferably a Li-ion battery cell. The energy cell is used, for example, in a battery for a vehicle with an electric drive. The energy cell has a cell stack and at least one arrester (in particular exactly two arresters), which with connected to the cell stack. The arrester is made in particular from a metal, eg nickel. The energy cell also has a cell housing which has at least two housing parts, namely a first housing part and a second housing part. In a suitable configuration, the housing parts are designed as identical parts. The cell stack preferably has several layers, namely anode layers, cathode layers and separator layers. The anode layers on the one hand and the cathode layers on the other are expediently each connected to their own conductor. For example, a respective conductor is designed in two parts and has two plates for this purpose, between which the anode layers or the cathode layers of the cell stack or a suitable extension thereof are or are clamped. The two conductors lead out of the cell housing and thus each form an electrical connection for the energy cell, one for a positive pole and one for a negative pole. In contrast, the cell stack is in particular completely enclosed within the cell housing.

As part of the method, the housing parts are assembled in such a way that they enclose the cell stack and that the conductor protrudes from the cell housing. This assembly of the housing parts and the enclosing of the cell stack is also referred to as assembly. Furthermore, the housing parts are connected to one another by arranging an adhesive between the housing parts for adhering the housing parts to one another. For this purpose, the adhesive is applied to at least one of the housing parts and preferably to both housing parts. In particular, the adhesive is not applied to the cell stack, so it is not used to fix the cell stack relative to the cell housing, but only to connect the housing parts to one another and to the conductor. In a suitable embodiment, the adhesive is applied in the form of a paste, e.g., from a nozzle or gun. In particular, the adhesive is applied either to just one of the housing parts or to both housing parts. Alternatively or additionally, the adhesive is applied in the form of a stick, e.g. with a circular cross-section, to one of the housing parts or to both housing parts (then two sticks). The adhesive is preferably arranged during assembly or already attached to a housing part during manufacture of the same. The adhesive is preferably applied continuously so that there is an uninterrupted adhesive strip and optimum tightness is achieved.

The adhesive is now arranged in such a way that it also extends over the arrester so that the arrester is also glued to the housing parts. In other words: the adhesive extends along an adhesive path, which generally runs between the housing halves and also specifically runs over the conductor. The adhesive sheet preferably runs over the arrester both on an upper side and on an underside of the arrester, so that it is glued to both housing halves, namely to one housing half on the upper side and to the other housing half on the lower side.

In the present case, it is assumed without loss of generality that the energy cell is a pouch cell whose cell housing has exactly two housing parts, each of which is designed as a half-shell. Alternatively, the energy cell has a different format and is then, for example, a prismatic cell or a round cell. Furthermore, without restricting the generality, it is assumed that the energy cell has precisely two conductors which protrude from the cell housing on opposite sides of the energy cell. Furthermore, without loss of generality, it is assumed that the cell stack is a stack in which multiple layers are stacked one on top of the other as parallel planes in a stacking direction. The layers are, in particular, on the one hand electrode layers, namely anode layers and cathode layers, and on the other hand separator layers, with anode layers and cathode layers alternating in the stacking direction and with a separator layer being arranged between two successive electrode layers in the stacking direction (ie anode, separator, cathode, separator, then repetition of this Sequence). Furthermore, without loss of generality, it is assumed that the cell housing has a total of four sides which lead around the cell stack, namely in the circumferential direction around the stacking direction. Furthermore, the housing parts are either initially completely separate from one another and are only connected to each other on all four sides by means of the adhesive during the manufacture of the energy cell, or are already connected to one another along one or more sides and are then attached to the remaining sides connected to each other, in particular by means of the adhesive. In a suitable embodiment, the two housing parts are connected along one side and are folded like a book to enclose the cell stack along this side and thereby collapsed and then connected to one another on the remaining three sides as part of the method after enclosing the cell stack, in particular by means of the adhesive. The adhesive is preferably arranged at least on those sides on which the two conductors are also arranged. In a suitable development, the adhesive arranged on one or more other sides surrounding the cell stack, for example in a U-shape (ie on three sides) or O-shape (ie on all sides). The above assumptions, individually or in combination, result in preferred configurations, but are not mandatory per se and further suitable configurations also result from the fact that one, several or all of these assumptions are not fulfilled.

The invention is initially based on the observation that a heat-sealing process may not be sufficient to connect the housing parts of an energy cell. The housing parts are made from a multi-layer laminate, for example, particularly in the case of a pouch cell. A respective housing part then has four layers, for example, namely a layer made of polypropylene (PP, PP layer), a layer made of aluminum, a layer made of polyamide (PA, PA layer) and a layer made of polyethylene terephthalate (PET, PET layer ), specifically in that order. Such a laminate is also preferred in the present case, but other materials for the housing parts are also conceivable and suitable. Two housing parts are then connected to one another, for example, by placing their PP layers next to one another and connecting them to one another in a heat-sealing process (i.e. "hot sealing"), e.g. at 175 °C. The PET layers then form an outside of the cell housing and the PP layers an inside of the cell housing.

Hydrogen fluoride (HF) may be produced during manufacture and/or when the energy cell is used as intended. This is basically acidic and destroys the PP layers, so that holes are formed in them, which reduce the tightness of the cell housing. This makes it possible for electrolyte to leak out of the cell housing.

It was also recognized that a heat-sealed seam, which is produced by the heat-sealing process, regularly breaks at an internal pressure of 8 bar in the cell housing. During manufacture and/or when the energy cell is used as intended, gas is regularly produced which cannot escape from the cell housing, so that the internal pressure increases. The energy cell bulges accordingly and typically tears first at the heat seal seam. Oxygen can then enter the cell housing and cause an explosion.

Contact between the aluminum layer and the cell stack, especially its electrode layers, is also problematic, as this can result in a short circuit. If the PP layers are destroyed, e.g. by HF or the internal pressure as described above, or even during the manufacture of the housing parts, e.g. by deep drawing, the aluminum layer may be exposed and can then be electrically connected to the electrode layers unintentionally. As a result, the energy cell in particular heats up.

It was also observed that the tightness of the cell housing is at risk, especially in the arrester area. For example, a strip-shaped heat-sealing bridge (e.g. a plastic band, also known as "tape") is used for the heat-sealing process in the area of the arrester, which runs across the arrester and is slightly wider than it (e.g. by 2% - 10% per side). The heat-sealed seam then runs along the heat-sealed bridge, which in particular ensures that the housing part is connected to the conductor. At the edge of the arrester, where the arrester ends and the housing parts meet again and where the heat-sealing bridge may protrude somewhat, there is a weak point, as already described, at which the heat-sealing seam between the housing parts is particularly weak. A leak is particularly likely here and the tightness is reduced. The connection between the heat seal bridge and the arrester is also regularly adversely affected by welding the arrester, e.g. when connecting several energy cells to one another or when connecting the two plates of the arrester to one another.

To solve the aforementioned problems, it would be conceivable to make the heat-sealed seam wider so that more material from the PP layers is connected to one another. It would also be conceivable to set the sealing properties in the heat-sealing process in such a way that the greatest possible tear resistance results. It is also conceivable to produce the heat-sealing bridge from a material that is as temperature-resistant as possible or to texture it in order to achieve better sealing and thus tightness. Finally, it is also conceivable to reduce the moisture in the cell housing to a minimum in order to reduce the formation of HF as much as possible.

While all of these solutions are fundamentally advantageous, in the present case an adhesive is arranged between the housing parts to improve the tightness in order to glue them together particularly tightly. The use of the adhesive also addresses the aforementioned problems. An important advantage of the invention is then, in particular, that an overall improved tightness of the cell housing is achieved by the adhesive. The arrangement of the adhesive can be integrated particularly easily into conventional methods for producing an energy cell, in particular apart from the arrangement of the adhesive itself initially no additional process steps necessary. In order to bond the housing parts and the conductor to one another, the adhesive is in particular melted and hardened; both can advantageously be integrated into manufacturing processes as described in the introduction, as will be explained further below. With the adhesive, an overall adhesive connection is created which has a particularly high adhesive strength and advantageously also withstands a high internal pressure in the cell housing of preferably up to 8 bar or more. This avoids ingress of oxygen from outside the cell casing and into it and advantageously reduces the likelihood of thermal propagation.

The adhesive is preferably chemically inert, especially to an electrolyte within the power cell and/or to HF. This prevents the housing parts from becoming detached from one another again as a result of chemical reactions within the energy cell. Furthermore, the adhesive is preferably electrically insulating. In a suitable embodiment, the adhesive is acrylic-based, silicone-based, or polyamide-based. The adhesive further suitably has a curing agent (also referred to as a “curing agent”). The curing agent is advantageously a high-speed curing agent (also referred to as “high speed curing agent”) and cures at a curing temperature which is preferably between 40°C and 60°C, in particular 50°C.

In a preferred embodiment, at least the first housing part has a channel in which the adhesive is arranged. The channel is also referred to as a depression, channel, rill or groove and, due to the principle, defines the course of the subsequent adhesive strip. A channel is preferably formed in each of the two housing parts, in particular adhesive is then also arranged in both channels. In the assembled state, the two channels in particular coincide, so that the adhesive is brought together on both housing parts, at least insofar as the channel is not covered by the conductor. A respective channel is open towards the other housing part. The channel is preferably formed during the manufacture, preferably during the deep-drawing, of a housing part, in particular in addition to a trough for accommodating the cell stack. Depending on the design, the channel then runs at least in sections or completely around the trough. A corresponding die is used to form the channel during deep-drawing.

Advantageously, the channel is profiled. The profile is expediently also produced during the production of the housing part and in particular also by means of the stamp for the channel. The profile is preferably formed at the bottom of the channel. The profile is advantageously used for better wetting of the housing part with the adhesive. In an expedient embodiment, the profile is formed by a large number of intersecting lines, which are designed, for example, as elevations and/or depressions.

In an advantageous embodiment, a toothing is formed in the first housing part along the adhesive, e.g. to the side and/or parallel to it, which engages in a preferably complementary toothing of the second housing part, so that both toothings together form a barrier to prevent the adhesive spreads beyond the serrations. For example, one toothing is a groove and the other toothing is a rib. The two toothings are designed, for example, in the manner of a plug-in connection. The toothings are suitably formed during manufacture of the housing parts and in particular together with the channel. Three variants are conceivable for the positioning of the teeth: firstly, on both sides of the adhesive, so that the same is prevented from flowing both inwards and outwards, or only on one side of the adhesive, i.e. secondly, inwards between the adhesive and the cell stack, or thirdly outwards such that the adhesive is positioned between the interlocking and the cell stack.

The toothing described is largely useless in the area of the arrester, as this prevents the two opposite toothings from meshing. Therefore, no toothing is expediently formed in the area of the arrester. However, an embodiment is advantageous in which the two housing parts have an elevation along the adhesive and in that area in which the housing parts bear against the arrester (i.e. in the area of the arrester), which is pressed onto the arrester in order to prevent that the adhesive spreads beyond the respective elevation. The effect achieved is analogous to the effect of the gearing. In principle, the toothing and the elevation are independent of one another, but are preferably combined, particularly preferably such that the toothing is continued as an elevation in the region of the arrester, so that the overall result is a seal that is as uninterrupted as possible against a flow of the adhesive. The elevations of both housing parts are preferably opposite one another, analogous to the toothing.

Advantageously, one, several or all of the method steps mentioned in the introduction for producing an energy cell are also used in the method described here. So will the cell stack is suitably produced first and the conductors are attached to it. Furthermore, two housing parts are suitably manufactured. The cell stack is then suitably inserted into the cell housing (also referred to as “assembling”) so that the two housing parts are arranged around and enclose the cell stack. However, the conductors protrude from the cell housing. The cell housing is then optionally closed in a heat-sealing process, at least partially and especially in the arrester area. A heat-sealed seam, which connects the two housing parts to one another, is suitably produced along the cell housing and across the arresters. However, the conductors lie between the two housing parts and prevent the housing parts from being directly connected to one another there. Rather, in the area of a respective arrester, this arrester is connected on both sides to a respective housing part, suitably by means of a heat-sealed bridge as described above. In the case of the heat-sealing process, the cell housing is suitably not yet completely closed, but an opening remains for filling with an electrolyte. After the heat-sealing process, the cell housing is then appropriately filled with electrolyte, which in particular wets the cell stack. Finally, the cell housing is completely closed, in particular again in a heat-sealing process, in which the heat-sealed seam is then completed. The two heat-sealing processes can also be combined with one another in a single heat-sealing process, which then takes place eg after filling, the cell housing then being partially closed eg with a holding device (eg as described below) during filling. This is suitably followed by conditioning, during which gas is produced in the cell housing and is collected in a gas pocket in the cell housing. After conditioning, the gas pocket is suitably separated and the cell housing is sealed again with a heat-sealing process, with an additional heat-sealed seam being produced in particular. Finally, an aging process is appropriately carried out, during which the already fully assembled energy cell is exposed to an elevated temperature of preferably 50° C. over a specific period of time (eg several days). After aging and an optional final inspection, the energy cell is finished.

The use of the heat-sealing process is particularly advantageous, which then, in combination with the adhesive, leads to a double connection of the housing halves, so to speak, namely on the one hand by means of the adhesive and on the other hand by means of the heat-sealed seam. In a suitable embodiment, after the adhesive has been arranged, the two housing parts are connected to one another in a heat-sealing process, namely along a heat-sealed seam which runs laterally along the adhesive in such a way that it is melted during the heat-sealing process and expediently also at least partially hardened. Preferably, the adhesive is between the heat seal and the cell stack. The heat-sealing process is therefore advantageously used at the same time for melting (and advantageously also for curing) the adhesive and thus at least indirectly for gluing the housing parts by means of the adhesive. This utilizes the fact that a tool, e.g. a roller, is brought up to the housing parts for the respective heat-sealing process in order to heat them up locally and thereby create the heat-sealed seam. The adhesive is now positioned so close to the intended heat seal that the adhesive is also heated by the tool. In this case, it is not absolutely necessary for the tool to cover the adhesive; rather, it is sufficient for it to be sufficiently heated. As a result of the adhesive melting, it optimally fills out the channel or channels in particular, resulting in a particularly high level of tightness.

Before the heat-sealing process, a heat-sealing bridge is expediently arranged between the conductor and the housing parts, as already described, along which the heat-sealing seam then runs. The adhesive is positioned between the heat seal bridge and the cell stack. If necessary, another elevation is positioned between the adhesive and the heat-sealing bridge as a barrier for the adhesive, as already described.

In principle, a heat sealing process is not absolutely necessary to achieve a high degree of tightness, but leads to an improvement in the tightness compared to a design without a heat-sealed seam and enables the adhesive to melt and possibly also cure in a simple manner without an additional process step.

In an advantageous embodiment, the cell housing is clamped a) for filling with an electrolyte, b) for conditioning after filling with electrolyte and/or c) during aging in a holding device which presses the two housing parts and in particular also the arrester together and also at the same time squeezes the glue. The holding device is heated so that the adhesive hardens. For example, the adhesive has a curing temperature, for example 50° C., and the holding device is heated in such a way that the adhesive reaches the curing temperature and cures accordingly. From the above Enumeration makes it clear that curing in different process steps is possible and advantageous, the holding device used in each case is not necessarily the same. Curing in one of the process steps mentioned is sufficient in itself, but a combination is advantageous, so that the adhesive is cured in two or more of the process steps mentioned. All of the configurations are based on the observation that in some, and in particular in the named method steps, the cell housing is heated anyway or is at least possible in a simple manner. The adhesive and in particular its curing agent is expediently selected in such a way that the curing temperature corresponds at most to that temperature which is also achieved in the respective method step.

When filling the cell housing and the cell stack in it with electrolyte, the still partially open cell housing is held with a holding device, namely in particular in the area of the conductors, so that the housing halves, the conductors and the adhesive are pressed together there. The adhesive is now cured in a particularly simple manner by heating the holding device. The same fixture is preferably used to hold the cell casing in post-fill conditioning. Before conditioning, however, the cell housing is expediently completely closed, e.g. by an additional heat-sealing process, through which a heat-sealed seam is then expediently produced, so that a gas pocket is formed between this and the cell stack. Hardening is also possible during the final aging after the gas pocket has been separated, e.g. with a cutting tool, and the then finished energy cell has been resealed, namely by holding the energy cell along the adhesive with a holding device, which is heated accordingly during aging .

Advantageously, the adhesive is also arranged between the cell stack and a gas pocket (e.g. as already described) of the energy cell and is only cured there after the gas pocket has been separated, i.e. in particular not yet in a heat sealing process that may be present, so that gas can penetrate into the gas pocket is possible. The adhesive then has two different sections, namely a first section in the area of one or both conductors and a second section, in particular on that side of the cell housing through which the electrolyte is filled. While the first section is already cured during the heat-sealing process, during filling with an electrolyte and/or during conditioning after filling, the second section remains intentionally gas-permeable to allow gas to pass from the cell stack into the gas pocket during conditioning. Only after conditioning is the adhesive of the second section then cured, preferably by a heat-sealing process in which before/during/after the separation of the gas pocket a heat-sealed seam for the final closure of the cell housing is formed so close to the adhesive that it is cured at the same time , similar to melting and possibly hardening in the area of the arrester. As an alternative or in addition, the adhesive on the second section is cured, in particular during aging, with a heated holding device as described.

Aside from the production of an energy cell described here, the method described is also generally advantageous in the production of packaging for a component, the packaging being produced from a laminate and a connection being made between a plastic and a metal. The plastic is in particular a layer of the laminate, which in particular also has a layer made of metal, e.g. made of aluminum, overall for example like the laminate with four layers described above. In the case of the energy cell, the cell housing is the packaging and the cell stack is the component; the conductor is the metal that is to be connected to the plastic of the cell housing. Another application example is the encapsulation of several energy cells in one housing (this is also referred to as "cell to pack"), since similar requirements arise here. The housing is then the packaging and the energy cells are the component.

An energy cell according to the invention has a cell housing, a cell stack and at least one arrester, with the arrester being connected to the cell stack, with the cell housing having two housing parts, namely a first housing part and a second housing part, with the housing parts being assembled in such a way that they enclosing the cell stack and that the conductor protrudes from the cell housing, the housing parts being connected to one another by an adhesive being arranged between the housing parts for gluing the housing parts to one another, the adhesive being arranged in such a way that it also extends over the conductor so that the arrester is also glued to the housing parts. The power cell is preferably manufactured according to a method as described. The energy cell is characterized in particular by the adhesive described, which glues the housing parts together particularly tightly.

• 1 eine Energiezelle in einer Schnittansicht,
• 2 die Energiezelle aus 1 in einer anderen Schnittansicht,
• 3 eine andere Energiezelle in einer Schnittansicht,
• 4 die Energiezelle aus 3 in einer anderen Schnittansicht,
• 5 die Energiezelle aus 1 in offenem Zustand,
• 6 die Energiezelle aus 1 in einer Draufsicht,
• 7 einen Ausschnitt der 6,
• 8 ausschnittsweise die Energiezelle aus 3, deren Gehäuseteile von Flurwasserstoff angegriffen werden,
• 9 die Energiezelle aus 3, welche sich durch Erzeugung von Gas wölbt und reißt,
• 10 ausschnittsweise die Energiezelle aus 3, deren Gehäuseteile mit dem Zellstapel kurzgeschlossen werden,
• 11 die Energiezelle aus 3 in einer Draufsicht,
• 12 - 16 ausschnittsweise die Energiezelle aus 1 im Detail in einem Bereich, in welchem die Gehäuseteile direkt miteinander verbunden werden,
• 17 - 21 ausschnittsweise die Energiezelle aus 1 im Detail in einem Bereich, in welchem die Gehäuseteile mit einem Ableiter verbunden werden,
• 22 eine Herstellung der Gehäuseteile der Energiezelle aus 1,
• 23 einen Heißsiegelprozess ausgehend von der Darstellung in 6,
• 24 ein Abtrennen einer Gastasche ausgehend von der Darstellung in 23,
• 25 einen weiteren Heißsiegelprozess ausgehend von der Darstellung in 24,
• 26 eine Alterung ausgehend von der Darstellung in 25,
• 27 in einer Schnittansicht die Energiezelle aus 1 in einer Haltevorrichtung.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Daring each show schematically:

• 1 an energy cell in a sectional view,
• 2 the power cell off 1 in another sectional view,
• 3 another energy cell in a sectional view,
• 4 the power cell off 3 in another sectional view,
• 5 the power cell off 1 in open state,
• 6 the power cell off 1 in a top view,
• 7 a section of 6 ,
• 8th detail of the energy cell 3 , whose housing parts are attacked by hydrogen fluoride,
• 9 the power cell off 3 , which bulges and ruptures by generating gas,
• 10 detail of the energy cell 3 , whose housing parts are short-circuited with the cell stack,
• 11 the power cell off 3 in a top view,
• 12 - 16 detail of the energy cell 1 in detail in an area in which the housing parts are connected directly to each other,
• 17 - 21 detail of the energy cell 1 in detail in an area in which the housing parts are connected to an arrester,
• 22 a production of the housing parts of the energy cell 1 ,
• 23 a heat sealing process based on the representation in 6 ,
• 24 a separation of a gas pocket based on the representation in 23 ,
• 25 another heat sealing process based on the representation in 24 ,
• 26 an aging based on the representation in 25 ,
• 27 the energy cell in a sectional view 1 in a holding device.

In the present case, two housing parts 2 of a cell housing 4 of an energy cell 6 are connected with an additional adhesive 8 in order to obtain improved tightness. The energy cell 6 also has at least one and typically two conductors 10 which are also connected to the housing parts 2 by means of the adhesive 8 . 1 shows a corresponding energy cell 6 in a sectional view through the two conductors 10, 2 shows the same energy cell 6 in a different sectional view, which does not intersect the conductor 10, so that these 2 are not recognizable. The cutting planes of 1 and 2 are parallel to each other. In the exemplary embodiment shown, the two housing parts 2 are two half-shells and the energy cell 6 is designed as a pouch cell. For comparison, show the 3 and 4 analogous to the sectional views of 1 and 2 a power cell 6 without glue 8.

The energy cell 6 has a cell stack 12 and at least one arrester 10 (here exactly two arresters 6), which is connected to the cell stack 12. Furthermore, the energy cell 6 has a cell housing 4, which has at least two (exactly two here) housing parts 2, namely a first housing part and a second housing part. The cell stack 12 has a plurality of layers, namely anode layers 14, cathode layers 16 and separator layers 18. The anode layers 14 on the one hand and the cathode layers 16 on the other hand are each connected to their own collector 10. The anode layers 14 and cathode layers 16 are collectively referred to as the electrode layers. The two conductors 10 lead out of the cell housing 4 and thus each form an electrical connection for the energy cell 6, once a positive pole and once a negative pole. In contrast, the cell stack 12 is completely enclosed within the cell housing 4 .

In a method for producing an energy cell 6, for example as in FIG 1 and 2 shown, the housing parts 2 are put together in such a way that they enclose the cell stack 12 and that the conductor 10 protrudes from the cell housing 4 (also referred to as assembly). Furthermore, the housing parts 2 are connected to one another by arranging an adhesive 8 between them for adhering the housing parts 2 to one another. For this purpose, the adhesive 8 is applied to at least one of the housing parts 2 and even to both housing parts 2 here. This is in the 5 and 6 recognizable, which show the energy cell 6 during assembly. while showing 5 the energy cell 6 off 1 still open and in a sectional view perpendicular to the sectional views of 1 and 2 . the 6 then shows the power cell off 1 in a plan view, only one of the housing parts 2 being shown, so that the interior of the energy cell 6 is visible (the plane of the drawing in 6 is perpendicular to the drawing planes of 1 , 2 and 5 , namely). The adhesive 8 is just not on the cell stack 12 applied, so does not serve to fix the cell stack 12 relative to the cell housing 4, but only to connect the housing parts 2 to each other and to the conductor 10. The adhesive 8 is applied, for example, in the form of a paste or in the form of a rod, for example with a circular cross-section one of the housing parts 2 or applied to both housing parts 2. A section of such a rod is in 7 shown, which is a section of the energy cell 6 in the representation of 6 indicates. In the exemplary embodiments shown, the adhesive 8 is applied continuously, resulting in an uninterrupted adhesive strip.

How special in the 2 and 6 As can be seen, the adhesive 8 is arranged in such a way that it also extends over the arrester 10, so that this is also bonded to the housing parts 2. In other words: the adhesive 8 extends along an adhesive path, which generally runs between the housing halves 2 and specifically also leads over the arrester 10 . In the exemplary embodiment shown, the adhesive web runs over the arrester 10 both on its upper side and on its lower side, so that it is glued to both housing halves 2, namely on the upper side to one housing half 2 and also on the lower side to the other housing half 2 is particularly good at 2 recognizable.

In the exemplary embodiments shown, the energy cell 6 is a pouch cell whose cell housing 4 has exactly two housing parts 2, each of which is designed as a half-shell. Furthermore, the energy cell 6 has exactly two conductors 10 which protrude from the cell housing 4 on opposite sides of the energy cell 6 . Further, the cell stack 12 is a stack in which multiple layers are stacked as parallel planes in a stacking direction. Anode layers 14 and cathode layers 16 alternate in the stacking direction, and a separator layer 18 is arranged between two successive electrode layers in the stacking direction. Furthermore, the cell housing 4 has a total of four sides which lead around the cell stack 12, namely in the circumferential direction around the stacking direction. In the present case, the two housing parts 2 are already as in 5 recognizable connected to each other along one side and are then folded like a book to enclose the cell stack 12 and then connected to each other on the remaining three sides by means of the adhesive 8 . Alternatively, the housing parts 2 are connected beforehand on more than one side or are initially completely separate from one another and are only connected to one another on all four sides by means of the adhesive 8 during the manufacture of the energy cell 6 . The adhesive 8 is arranged at least on those sides on which the two conductors 10 are also arranged. In the exemplary embodiments shown, the adhesive 8 is arranged on one or more other sides, surrounding the cell stack 12 here in a U-shape (i.e. on three sides). or alternatively eg O-shaped (ie on all sides). However, the above features are in each case optional and further exemplary embodiments result in the modification or omission of one, several or all of the above features.

In the present case, it was recognized that a heat-sealing process for connecting the housing parts 2 of an energy cell 6 may not be sufficient. The housing parts 2 are in the 1 - 4 made of a multi-layer laminate and each have four layers, namely a layer 20 made of polypropylene (PP, PP layer), a layer 22 made of aluminum, a layer 24 made of polyamide (PA, PA layer) and a layer 26 made of polyethylene terephthalate (PET, PET layer). Two housing parts 2 are connected to one another, for example, by placing their PP layers 20 against one another and connecting them to one another in a heat-sealing process (ie “hot sealing”). The PET layers 26 then form an outside of the cell housing 4, the PP layers 20 an inside.

Hydrogen fluoride (HF) may be produced during manufacture and/or when the energy cell 6 is used as intended. This is basically acidic and destroys the PP layers 20, so that holes 27 are formed in them, as in 8th is illustrated, which is a section of the energy cell 6 from 3 indicates. This makes it possible for electrolyte to escape from the cell housing 6 to the outside.

It was also recognized that a heat-sealed seam 28, which is produced by the heat-sealing process, regularly breaks at an internal pressure of 8 bar in the cell housing 4. During manufacture and/or when the energy cell 6 is used as intended, gas G is regularly produced, which cannot escape from the cell housing 4, so that the internal pressure increases. The energy cell 6 arches accordingly, e.g. as in 9 1, and typically tears first at the heat seal 28, such as shown in the enlarged detail in FIG 9 shows the energy cell 6 of FIG 3 ). Oxygen can then penetrate into the cell housing 4 and lead to an explosion.

Contact of the aluminum layer 22 with the cell stack 12, specifically its electrode layers, is also problematic, since this can result in a short circuit. If the PP layers 20, for example, by HF or the internal pressure as described or even during production If the housing parts 2 are destroyed, for example by deep-drawing, the aluminum layer 22 may be exposed and can then be electrically connected to the electrode layers unintentionally. this is in 10 illustrated, which is part of the energy cell 6 of 3 indicates

It was also observed that the tightness of the cell housing 4 is at risk, especially in the area of the arrester 10 . For example, for the heat sealing process in the area of the arrester 10 as in 11 shown uses a strip-shaped heat-seal bridge 30, which runs transversely across the conductor 10 and is slightly wider than this ( 11 shows the energy cell 6 3 in a plan view analogous to the plan view in 6 ). The heat-sealed seam 28 then runs along the heat-sealed bridge 30. At the edge of the conductor 10, where it ends and the housing parts 2 meet again directly and where the heat-sealed bridge 30 may protrude slightly, there is a weak point 32, as already described, at which the Heat seal seam 28 between the housing parts 2 is particularly weak. A leak is particularly likely here and the tightness is reduced. The connection between the heat seal bridge 30 and the conductor 10 is also regularly adversely affected by the welding of the conductor 10 .

In the present case, to improve the tightness, the adhesive 8 is arranged between the housing parts 2 in order to glue them together particularly tightly and to address the aforementioned problems. The arrangement of the adhesive 8 can be integrated into conventional methods for producing a power cell 6 . In the present case, the adhesive 8 is melted and hardened to bond the housing parts 2 and the arrester 10 to one another. In the present case, the adhesive 8 is chemically inert, specifically with respect to an electrolyte within the energy cell 6 and/or with respect to HF. Furthermore, the adhesive 8 is electrically insulating in the present case. The adhesive 8 is, for example, acrylic-based, silicone-based or polyamide-based. The adhesive 8 here further comprises a curing agent, which here is also a high-speed curing agent and cures at a curing temperature which is between 40°C and 60°C, for example 50°C.

In the embodiment shown here, both housing parts 2 have a channel 34 in which the adhesive 8 is arranged. The respective channel 34 is, for example, in 5 recognizable and in detail in the 12 - 21 shown. As a matter of principle, the channel 34 defines the course of the subsequent adhesive web. the 12 and 17 show the cell housing 4 in the open state 13 and 18 the two housing parts 2 are assembled into the 16 and 21 the housing parts 2 are assembled, ie in the assembled state. As can be seen from the aforementioned figures, the two channels 34 of the housing parts 2 also coincide here, so that the adhesive 8 is brought together on both housing parts 2, at least insofar as the channel 34 is not covered by the conductor 10, as in FIGS 18 - 21 is recognizable. A respective channel 34 is correspondingly open towards the other housing part 2 . In the present case, the channel 34 is formed during the manufacture, here during deep-drawing, of a housing part 2, in the present case in addition to a trough 36 for receiving the cell stack 12. This is shown by way of example in FIG 22 Illustrates which the production of the housing parts 2 of the energy cell 6 from 1 represents. Depending on the configuration, the channel 34 runs at least partially or completely around the trough 36 . A corresponding die 38 is used to form the channel 34 during deep-drawing.

In the present case, the channel 34 is additionally provided with a profile 40 which is also produced here during the production of the respective housing part 2 and here also by means of the stamp 38 . In the present case, the profile 40 is formed at the base of the channel 34 by a large number of intersecting lines (e.g. elevations and/or depressions), as shown by way of example in the enlargement in FIG 22 is shown, this enlargement showing a section of the profile 40 in a plan view into the channel 34 inside.

In the exemplary embodiments shown, toothing 42 is additionally formed in the first housing part 2 along the adhesive 8, here laterally next to it and parallel to it, which engages in a complementary toothing 42 of the second housing part 2, so that both toothings 42 together form a barrier in order to to prevent the adhesive 8 from spreading beyond the serrations 42. A schematic example of the teeth 42 is shown in FIGS 12 - 16 shown. There is a toothing 42 is a groove and the other toothing 42 is a rib and the two teeth 42 are formed in the manner of a plug-in connection. In the present case, the teeth 42 are formed during the manufacture of the housing parts 2 and, for example, together with the channel 34 . For the positioning of the teeth 42 three variants are conceivable: first, as in the 12 - 16 shown on both sides of the adhesive 8, so that it is prevented from flowing both inwards and outwards, or - not explicitly shown - only on one side of the adhesive 8, i.e. secondly, inwards between the adhesive 8 and the cell stack 12 , or thirdly outwards in such a way that the adhesive 8 is positioned between the teeth 42 and the cell stack 12 .

In the area of arrester 10, this prevents the two opposing teeth 42 from meshing. Therefore, no teeth 42 are formed there, but the two housing parts 2 point along the adhesive 8 and in each case in that area in which the housing parts 2 rest on the arrester 10 ( ie in the area of the arrester), an elevation 44 which is pressed against the arrester 10 in order to prevent the adhesive 8 from spreading beyond the respective elevation 44 . This is in the 18 - 21 shown schematically. The effect achieved is analogous to the effect of the toothing 42. In principle, the toothing 42 and the elevation 44 are independent of one another, but are preferably combined, particularly preferably in such a way that the toothing 42 is continued in the region of the diverter 10 as an elevation 44, so that overall, a seal that is as uninterrupted as possible against a flow of the adhesive 8 results.

Optionally, one, several or all of the method steps mentioned in the introduction for producing the energy cell 6 are also used in the method described here. For example, the cell stack 12 is first produced and the conductors 10 are attached to this. Next two housing parts 2 are produced. The cell stack 12 is then inserted into the cell housing 4 (also referred to as “assembling”), so that the two housing parts 2 are arranged around the cell stack 12 and enclose it. However, the arresters 10 protrude from the cell housing 4 . The cell housing 4 is then optionally closed in a heat-sealing process, at least partially and specifically in the area of the conductor 10. This is shown in FIGS 15 and 20 shown as well as in 23 , which the energy cell 6 from 15 and 20 shows in a plan view, wherein the one housing part 2 is not shown for the sake of clarity. In the heat-sealing process, a heat-sealed seam 28 is produced along the cell housing 4 and across the conductors 10, which seam connects the two housing parts 2 to one another. However, the conductors 10 lie between the two housing parts 2 and prevent them from being directly connected to one another there. Rather, in the area of a respective conductor 10, this is connected on both sides to a housing part 2, in this case by means of the heat-sealing bridge 30 already described. During the heat-sealing process, the cell housing 4 is not yet completely closed, but an opening 46 remains for filling with an electrolyte. After the heat-sealing process, the cell housing 4 is then correspondingly filled with electrolyte, which wets the cell stack 12 . Finally, the cell housing 4 as in 23 completely closed as shown, again in a heat sealing process, in which the heat seal seam 28 is then completed as shown. After conditioning, the gas pocket 46 is separated, e.g. as in 24 shown, and then the cell housing 4 is sealed again with a heat-sealing process, with an additional heat-sealed seam 48 being produced, e.g. as in FIG 25 shown. Finally, an aging takes place, e.g. as in 26 shown. During aging, the already fully assembled energy cell 6 is exposed to an increased temperature over a certain period of time. After aging and an optional final check, the energy cell 6 is finished.

In the present case, the heat-sealing process in combination with the adhesive 8 leads to a double connection of the housing halves 2, namely on the one hand by means of the adhesive 8 and on the other hand by means of the heat-sealed seam 28, 48. As can be seen in the figures, after the adhesive 8 has been arranged ( 6 ), the two housing parts 2 are connected to one another in a heat-sealing process ( 15 , 20 , 23 ), namely along a heat-sealed seam 28, which runs laterally along the adhesive 8 in such a way that it is melted during the heat-sealing process and is also at least partially cured here. This is done analogously in 25 for the additional heat-sealed seam 48. In the exemplary embodiment shown, the adhesive 8 lies between the heat-sealed seam 28, 48 and the cell stack 12. The heat-sealing process is therefore also used to melt and harden the adhesive 8 and thus to bond the housing parts 2 by means of the adhesive 8 . Here, use is made of the fact that a tool 50, for example a roller, is brought up to the housing parts 2 for the respective heat-sealing process in order to heat it up locally and thereby produce the heat-sealed seam 28, 48. The adhesive 8 is now arranged so close to the intended heat-sealed seam 28, 48 that the adhesive 8 is also heated by the tool 50.

In the present case, before the heat-sealing process, a heat-sealing bridge 30 is arranged between the conductor 10 and the housing parts 2, as already described, along which the heat-sealing seam 28 then runs. This can be seen, for example, in the 18 , 19 , 23 . The adhesive 8 is positioned between the heat seal bridge 30 and the cell stack 12 . In addition, the elevations 44 are also positioned here between the adhesive 8 and the heat-sealing bridges 30 .

The cell housing is also clamped a) for filling with an electrolyte, b) for conditioning after filling with electrolyte and/or c) during aging in a holding device 52, which presses the two housing parts 2 and also the conductor 10 together and also the Glue 8 compresses. The holding device 52 is heated in the process, so that the adhesive 8 hardens. A corresponding holding device 52 can be seen in the 14 , 15 , 19 , 20 , 24 , 25 , 26 , 27 . It is clear here that curing is possible in different method steps, but the holding device 52 used in each case is not necessarily the same. Curing in one of the method steps mentioned is sufficient in itself, but a combination is used here so that the adhesive 8 is cured in two or more of the method steps mentioned. In this case, use is made of the fact that in some and specifically in the method steps mentioned, heating of the cell housing 4 takes place anyway or is at least possible in a simple manner.

When filling the cell housing 4 and the cell stack 12 therein with electrolyte, the still partially open cell housing 4 is held with a holding device 52, for example in the area of the conductor 10 as in FIG 27 shown, so that there the housing halves 2, the conductor 10 and the adhesive 8 are pressed together. The adhesive 8 is cured by heating the holding device 52. The same holding device 52 is also used here to hold the cell housing 4 during conditioning following filling. Before conditioning, however, the cell housing 4 is completely closed, e.g. by an additional heat-sealing process, in order to create a heat-sealed seam 28 as in FIG 23 to obtain, between which and the cell stack 4 then the gas pocket 46 is formed. Also in the final aging after separation of the gas pocket 46 ( 24 ) E.g. with a cutting tool 53 and renewed sealing of the then finished energy cell 6, curing is still possible, namely by holding the energy cell 6 along the adhesive 8 with a holding device 52, which is correspondingly heated during the aging ( 26 ).

In the exemplary embodiments shown, the adhesive 8 is additionally also arranged between the cell stack 12 and the gas pocket 46 . In addition, in the present case the adhesive 8 is cured there only after the gas pocket 46 has been separated, so that when conditioning starting from 23 gas passage into the gas pocket 46 is possible. The adhesive 8 then has two different sections 54, 56, namely a first section 54 in the area of one or both conductors 10 and a second section 56 on that side of the cell housing 12 via which the electrolyte is filled. While the first section 54 is already cured during the heat-sealing process, during filling with an electrolyte and/or during conditioning after filling, the second section 56 intentionally remains gas-permeable in order to allow gas G to pass from the cell stack 12 into the gas pocket 46 during conditioning enable. Only after the conditioning is the adhesive 7 of the second section 56 cured, for example by the heat sealing process in FIG 25 , in which before/during/after the separation of the gas pocket 46 the additional heat-sealed seam 48 for the final closure of the cell housing 4 is formed so close to the adhesive 8 that it is cured at the same time, analogous to melting and possibly curing in the area of the conductor 10. Alternatively or additionally, the adhesive 8 on the second portion 56 will be degraded upon aging with the heated jig 52 as in FIG 26 shown cured.

Reference List

2

housing part

4

cell case

6

power cell

8th

adhesive

10

arrester

12

cell stack

14

anode layer

16

cathode layer

18

separator layer

20

PP layer

22

layer of aluminum

24

PA layer

26

PET layer

27

holes

28

heat seal seam

30

heat seal bridge

32

weak spot

34

channel

36

trough

38

Rubber stamp

40

profile

42

gearing

44

elevation

46

gas bag

48

additional heat seal seam

50

tool (for heat sealing process)

52

holding device

53

cutting tool

54

first section

56

second part

G

gas

HF

hydrofluoric acid

Claims (10)

Process for manufacturing a power cell (6), - wherein the energy cell (6) has a cell stack (12) and at least one conductor (10) which is connected to the cell stack (12), - wherein the energy cell (6) has a cell housing (4) which has at least two housing parts (2), namely a first housing part (2) and a second housing part (2), - the housing parts (2) being assembled in such a way that they enclose the cell stack (12) and that the conductor (10) protrudes from the cell housing (4), - wherein the housing parts (2) are connected to one another by arranging an adhesive (8) between the housing parts (2) for gluing the housing parts (2) to one another, - The adhesive (8) being arranged in such a way that it also extends over the arrester (10), so that the arrester (10) is also bonded to the housing parts (2). procedure after claim 1 , wherein at least the first housing part (2) has a channel (34) in which the adhesive (8) is arranged. procedure after claim 2 , wherein the channel (34) is provided with a profile (40). Procedure according to one of Claims 1 until 3 , wherein in the first housing part (2) along the adhesive (8) a toothing (42) is formed, which engages in a toothing (42) of the second housing part (2), so that both toothings (42) together form a barrier to to prevent the adhesive (8) from spreading beyond the serrations (42). Procedure according to one of Claims 1 until 4 , wherein the two housing parts (2) have an elevation (44) along the adhesive (8) and in that area in which the housing parts (2) rest on the arrester (10), which is pressed onto the arrester (10). , to prevent the adhesive (8) from spreading beyond the respective elevation (44). Procedure according to one of Claims 1 until 5 , wherein after the adhesive (8) has been arranged, the two housing parts (2) are connected to one another in a heat-sealing process, namely along a heat-sealed seam (28, 48) which runs laterally along the adhesive (8) in such a way that this during of the heat sealing process is melted. procedure after claim 6 , a heat-sealing bridge (30) being arranged between the conductor (10) and the housing parts (2) before the heat-sealing process, along which the heat-sealing seam (28) then runs, the adhesive (8) between the heat-sealing bridge (30) and the cell stack (12) is positioned. Procedure according to one of Claims 1 until 7 , wherein the cell housing (4) is clamped in a holding device (52) for filling with an electrolyte, for conditioning after filling with electrolyte and/or during aging, which device presses the two housing parts (2) together and also releases the adhesive (8 ) together, wherein the holding device (52) is heated so that the adhesive (8) hardens. Procedure according to one of Claims 1 until 8th , wherein the adhesive (8) is also arranged between the cell stack (12) and a gas pocket (46) of the energy cell (6) and is cured there only after the gas pocket (46) has been separated. Energy cell (6), which has a cell housing (4), a cell stack (12) and at least one conductor (10), - wherein the conductor (10) is connected to the cell stack (12), - wherein the cell housing (4) has two housing parts (2), namely a first housing part (2) and a second housing part (2), - wherein the housing parts (2) are assembled in such a way that they enclose the cell stack (12) and that the conductor (10) protrudes from the cell housing (4), - wherein the housing parts (2) are connected to one another by an adhesive (8) being arranged between the housing parts (2) for adhering the housing parts (2) to one another, - The adhesive (8) being arranged in such a way that it also extends over the arrester (10), so that the arrester (10) is also glued to the housing parts (2).

Images