Method for producing a degassing channel from a battery cell to a degassing opening of a battery module housing

Abstract

Method for producing a degassing channel from a battery cell to a degassing opening of a battery module housing (1). The method comprises providing a sealing sleeve (5) and a sealing plug (6), wherein the sealing sleeve (5) is made of an elastically deformable material, the sealing sleeve (5) having a first end, a second end opposite the first end in an axial direction (Z), and a passage extending from the first end to the second end, wherein a circumferential wall of the sealing sleeve (5) circumferentially delimits the passage of the sealing sleeve (5), wherein the sealing plug (6) has a cover section for closing the passage of the sealing sleeve (5) and a circumferential wall extending from the cover section, wherein the sealing plug (6) is slid into the sealing sleeve (5) along the axial direction (Z) until a clamping position is reached.wherein in the clamping position an outer circumferential surface of the circumferential wall of the sealing plug (6) rests against an inner circumferential surface of the wall of the sealing sleeve (5) and thereby supports the wall of the sealing sleeve (5) radially inwards, wherein the sealing sleeve (5) and the sealing plug (6) are first pre-assembled, then inserted into the degassing opening and then moved into the clamping position by pressing the sealing plug (6) forward.

Description

[0001] In electric or partially electric vehicles, numerous battery cells are connected together to form a high-voltage battery, also known as a traction battery. Such a high-voltage battery typically consists of several hundred, sometimes up to several thousand, battery cells. Malfunctions can cause a battery cell to overheat, causing its electrolyte to transform into a gaseous state, which causes the pressure within the battery cell to rise sharply within a short period of time. To prevent an uncontrolled rupture of a cell casing or shell of the affected battery cell, battery cells are known to be equipped with a safety valve that opens at a predetermined internal cell pressure and allows the evaporated electrolyte and any other decomposition products formed to escape. Such a process is also known as degassing.The safety valve can be formed by an opening in a cell housing which is closed with a rupture disc which bursts at a defined bursting pressure and thus releases the valve opening.

[0002] The battery cells are often arranged in a housing enclosing the battery cells, such as a battery module housing, for protection against external influences and / or for the purpose of direct cooling of the battery cells. In a design with a housing enclosing the battery cells, it is necessary to discharge the gases escaping from a battery cell's safety valve from this housing in a controlled manner, particularly to prevent damage to the other battery cells arranged in the housing from the escaping hot gases. Such a housing typically has one or more vents for this purpose. These vents must, in turn, be reliably sealed against water, dirt, and salt.

[0003] Particularly in the case of directly cooled battery cells, where a dielectric cooling fluid flows through the battery module housing, the venting opening must be reliably sealed against the environment.

[0004] The permanent and secure connection of such a vent opening to the safety valve of the respective battery cell is problematic. Firstly, there is the problem that battery cells, for example prismatic battery cells or pouch cells, are subject to changes in their thickness during charging and discharging, also known as breathing. Furthermore, battery cells can experience aging-related swelling. This means that the battery cells expand with increasing service life. Such changes in the battery cells can lead to a change in the distance between the battery cell and the vent opening. Excessive mechanical influences on the cell housing, such as those that could occur with a rigid connection of the safety valves to the vent opening, should also be avoided.In addition, in directly cooled battery cells, contact of hot gas with the dielectric cooling fluid should be avoided, as should leakage of cooling fluid to the outside and the ingress of foreign substances, such as water, into the cooling fluid. The ingress of foreign substances into the venting path from the safety valve to the venting opening should also be prevented.

[0005] EP 3 739 667 A1 discloses a safety valve for a battery. CN 218849539 U discloses a method in which a safety valve is mounted on a battery using a press plate. CN 202205855 U and DE 10 2021 129 317 A1 disclose further prior art.

[0006] The object of the present invention is to provide a novel method for producing a degassing channel from a battery cell to a degassing opening of a battery module housing.

[0007] This object is achieved by a method having the features of patent claim 1. Advantageous further developments are the subject of the dependent claims.

[0008] The method according to the invention serves to produce a venting channel from a battery cell to a venting opening of a battery module housing. The method according to the invention comprises the following method steps: - Providing a battery module housing, wherein the battery module housing has an interior space for accommodating at least one battery cell, wherein the battery module housing has a housing wall with a degassing opening opening into the interior space, - Providing a sealing sleeve and a closure plug, wherein the sealing sleeve consists of an elastically deformable material, wherein the sealing sleeve has a first end, a second end opposite the first end in an axial direction, and a through-channel extending from the first end to the second end, wherein a circumferential wall of the sealing sleeve circumferentially delimits the through-channel of the sealing sleeve, wherein the closure plug has a cover section for closing the through-channel of the sealing sleeve and has a circumferential wall extending from the cover section, wherein the closure plug can be inserted into the sealing sleeve along the axial direction until a clamping position is reached,wherein in the clamping position an outer peripheral surface of the circumferential wall of the sealing plug rests against an inner peripheral surface of the wall of the sealing sleeve and thereby supports the wall of the sealing sleeve radially inwards, - Pre-assembling the sealing plug in the sealing sleeve to form an assembly unit by inserting the sealing plug along the axial direction into the sealing sleeve in such a way that the sealing plug is held in the sealing sleeve and can be transferred into the clamping position by further moving the sealing plug along the axial direction, - Inserting the assembly unit into the degassing opening along the axial direction, such that the sealing sleeve reaches an end position in which the sealing sleeve passes through the degassing opening in the axial direction and the first end projects into the interior, wherein the sealing sleeve is arranged in front of the sealing plug in the insertion direction, - pressing the sealing plug along the axial direction to transfer the sealing plug into the clamping position to fix the sealing sleeve in the venting opening in the end position, wherein in the clamping position the outer peripheral surface of the circumferential wall of the sealing plug rests against the inner peripheral surface of the wall of the sealing sleeve in the radial direction and thereby presses the wall of the sealing sleeve against the inner peripheral surface of the housing wall to tightly close the venting opening, - Inserting the battery cell into the interior of the battery module housing, wherein the battery cell is inserted into the interior in such a way that the sealing sleeve rests with the first end sealingly against a cell housing of the battery cell, in such a way that a safety valve of the battery cell opens into the through-channel to form a degassing channel from the safety valve to the degassing opening.

[0009] The method according to the invention makes it possible in a simple manner to create a degassing channel between the safety valve of the battery cell and the degassing opening of the battery module housing assigned to this safety valve, wherein due to the sealing contact of the wall of the sealing sleeve, penetration of substances into the interior of the battery module housing is prevented, for example an ingress of water, and in the case of a directly cooled battery module in which a dielectric fluid flows in the interior of the battery module housing, leakage of the dielectric fluid through the degassing opening to the outside is prevented.The surrounding wall and the sealing connection to the cell housing create a degassing channel that is sealed off from the rest of the interior of the battery module housing. This ensures that the gas escaping from the safety valve is reliably guided to the degassing opening of the battery module housing and can escape there, enabling the most unhindered degassing of the battery cell possible. In particular, this also prevents any dielectric cooling fluid flowing in the interior of the battery module housing from coming into contact with the gases, as the gas flows in the through-channel towards the degassing opening, thus sealing this degassing path of the gas from the environment. Furthermore, it also prevents dielectric cooling fluid or any thermal paste injected between the battery cells and the battery module housing from entering the area of ​​the safety valve.The sealing plug seals the passageway from the environment so that no water, dust, or other contaminants can enter the passageway and from there reach the safety valve. The sealing plug also serves to fix the sealing sleeve in the venting opening to ensure a tight seal between the wall of the sealing sleeve and the inner circumferential surface of the housing wall. The sealing plug and the sealing sleeve initially form separate components, making them particularly easy to manufacture. In particular, the sealing sleeve and the sealing plug can each be formed as a single piece and consist of just one material. It is considered particularly advantageous if the sealing sleeve is made of a first plastic and the sealing plug is made of a second plastic, with the plastic of the sealing plug being harder than the plastic of the sealing sleeve.Due to the elastic deformability of the sealing sleeve, manufacturing and / or assembly tolerances can be compensated, ensuring that the venting channel is always reliably sealed against the environment. Changes due to swelling and / or aging, thus changes in the expansion of the battery cell, are also unproblematic due to the elastic deformability of the sealing sleeve. The formation of the assembly unit enables simple and reliable assembly, thus enabling a high level of automation of the assembly process.

[0010] A further advantage of the method according to the invention is that the battery cell can be inserted both after the assembly unit has been inserted and after the sealing plug has been pressed in, and before the assembly unit has been inserted and before the sealing plug has been pressed in.

[0011] In principle, however, it is also conceivable for the battery cell to be inserted after the mounting unit has been inserted and before the sealing plug is pressed in. Accordingly, one and the same mounting unit can be used regardless of the type of battery cell installation in the battery module housing.

[0012] It is considered particularly advantageous if the wall of the sealing sleeve has, at its first end, a circumferential retaining section that projects radially outward relative to the adjacent section of the wall, wherein, in the end position, the retaining section engages behind the housing wall on an inner side facing the battery cell. Such a design has the advantage that the sealing sleeve is held in the battery module housing not only by the force-fitting contact with the inner circumferential surface of the housing wall, but also by a positive connection with the battery module housing formed by the retaining section.

[0013] In a particularly preferred embodiment, the wall of the sealing sleeve has, at its end facing away from the battery cell, a radially outwardly projecting circumferential support section, wherein the support section bears against an outer side of the housing wall facing away from the battery cell, such that further insertion of the sealing sleeve into the venting opening is prevented by the interaction of the support section with the outer side of the housing wall. The support section facilitates the correct insertion of the sealing sleeve or the assembly unit into the housing wall of the battery module housing, since the support section, preferably in the end position of the sealing sleeve, comes into contact with the outer side of the housing wall and thereby prevents further insertion of the sealing sleeve into the venting opening.

[0014] In a particularly preferred embodiment, the outer circumferential surface of the wall of the closure plug and the inner circumferential surface of the wall of the sealing sleeve have corresponding locking structures, wherein the locking structures engage in a first locking position during pre-assembly and thereby hold the closure plug in the sealing sleeve, wherein the closure plug is spaced from the clamping position in the first locking position. The locking prevents accidental detachment of the closure plug from the sealing sleeve, whereby the closure plug and the sealing sleeve form a mechanically particularly stable assembly unit. This is particularly advantageous if the insertion of the assembly unit into the venting opening is to be automated.

[0015] In a particularly preferred embodiment, it is provided that the locking structures engage in a second locking position when pressed further, wherein the second locking position corresponds to the clamping position.

[0016] In a particularly preferred embodiment, it is provided that the insertion of the assembly unit and the subsequent pressing of the sealing plug take place using an assembly punch, wherein the assembly punch has an outer punch that can be moved in the axial direction and an inner punch that is arranged within the movable outer punch and can be moved in the axial direction relative to the outer punch, wherein to insert the assembly unit into the venting opening, the outer punch is moved and acts on the sealing sleeve and, after insertion, the inner punch is moved and acts on the sealing plug to subsequent pressing of the sealing plug into the clamping position. Such a method enables particularly safe, rapid and, in particular, fully automated assembly of the assembly unit in the battery module housing.

[0017] In this context, it is considered particularly advantageous if, when the inner punch is moved to push the closure plug into the clamping position, the support section is held clamped between the outer punch and the housing wall.

[0018] It is considered particularly advantageous if a holding force between the sealing plug and the sealing sleeve in the clamping position is designed such that when a predetermined limit pressure in the through-channel is exceeded, the sealing plug is completely pressed out of the sealing sleeve to release the through-channel for gas flowing out of the safety valve of the battery cell.

[0019] The following figures illustrate the invention in more detail using an exemplary embodiment, without being limited to this embodiment. They show: Fig. 1 a partial area of ​​a battery module in a schematic representation in a sectional view, Fig. 2 an arrangement comprising a battery module housing and a closure system for closing a degassing opening in a first assembly step in a schematic representation in a sectional view, Fig. 3 the order pursuant to Fig. 2 in a second assembly step, Fig. 4 the order pursuant to Fig. 3 in a third assembly step.

[0020] The Fig. Figure 1 shows a portion of a high-voltage battery for an electrically or at least partially electrically powered vehicle, namely a portion of a battery module. The battery module comprises a battery module housing 1, wherein a plurality of battery cells 2 are accommodated in the battery module housing 1. For reasons of clarity, Fig. 1 only shows a battery cell 2 and a lower housing wall of the battery module housing 1. The battery cell 2 comprises a cell housing with a safety valve 3 for degassing the battery cell 2. The battery module housing 1 has a housing wall with a degassing opening opposite the safety valve 3 of the battery cell 2 in an axial direction Z. A closure system 4 is arranged in the degassing opening, wherein the closure system 4 consists of a sealing sleeve 5 and a closure plug 6. The sealing sleeve 5 consists of an elastically deformable material, wherein the sealing sleeve 5 has a first end facing the battery cell 2, which first end extends into the housing interior enclosed by the battery module housing 1 up to the battery cell 2.Furthermore, the sealing sleeve 5 has a second end opposite the first end, which accordingly faces away from the battery cell 2, wherein a through-channel 7 extends from the first end to the second end through the sealing sleeve 5. The through-channel 7 is circumferentially delimited by a circumferential wall of the sealing sleeve 5, wherein the first end and the second end form part of the wall. The sealing sleeve 5 is arranged in the venting opening such that the sealing sleeve 5 penetrates the venting opening in the axial direction Z, which is identical to a vehicle vertical direction Z, and the first end rests against the cell housing of the battery cell 2 such that the safety valve 3 opens into the through-channel 7 and is circumferentially enclosed in a sealing manner by the wall.The sealing sleeve 5 accordingly forms a venting channel from the safety valve 3 to the venting opening, wherein this venting channel is sealed from the environment, in particular from the interior of the battery module housing 1, so that no mass transfer can take place between the interior of the housing and the through-channel 7. In particular, the sealing sleeve 5 prevents any dielectric cooling fluid flowing in the interior of the housing from reaching the area of ​​the through-channel 7 of the sealing sleeve 5 and thus the safety valve 3. In order to prevent foreign substances from penetrating the through-channel 7 from the outside and thus to protect the safety valve 3 from external influences, the through-channel 7 is closed by means of the sealing plug 6, wherein the sealing plug 6 is inserted into the sealing sleeve 5 from the second end of the sealing sleeve 5.The closure plug 6 comprises a closed cover section 8, which closes the through-channel 7 of the sealing sleeve 5. The closure plug 6 has a circumferential wall 9 extending from the cover section 8. In the embodiment shown in FIG. Fig. 1, the closure plug 6 is in a clamped position in which an outer circumferential surface of the circumferential wall 9 of the closure plug 6 bears against an inner circumferential surface of the wall of the sealing sleeve 5 and thereby supports the wall of the sealing sleeve 5 radially inward and presses it against the inner circumferential surface of the housing wall delimiting the venting opening.

[0021] The sealing plug 6 has a locking structure on the outer circumferential surface of the wall with several radially outwardly projecting circumferential projections. The inner circumferential surface of the wall of the sealing sleeve 5 has corresponding circumferential recesses. These locking structures can be engaged with one another in two different locking positions. A first locking position corresponds to a holding position in which the sealing plug 6 is only partially inserted into the sealing sleeve 6. The Fig. 2 and Fig. 3 show the sealing plug 6 in this holding position. The second locking position corresponds to the previously described clamping position. Fig. 1 and Fig. 4 show the sealing plug 6 in the second locking position or in the clamping position.

[0022] The first locking position is used to form an assembly unit that facilitates the installation of the closure system 4 in the venting opening. For this purpose, the closure plug 6 is pushed into the sealing sleeve 5 until the first locking position is reached, whereby the closure plug 6 is held in the sealing sleeve 5. This assembly unit is then pushed into the venting opening along the axial direction Z until the sealing sleeve 5 has reached the desired end position, in which the sealing sleeve 5 penetrates the venting opening in the axial direction Z and the first end protrudes into the interior. Subsequently, by further pressing the closure plug 6 along the axial direction Z, the closure plug 6 is transferred into the clamping position to fix the sealing sleeve 6 in the venting opening.The closure system 4 is designed such that, when the closure plug 6 is in the clamped position, upon exceeding a predetermined limit pressure in the passage 7, the closure plug 6 is completely pushed out of the sealing sleeve 5 to release the passage 7 for gas flowing out of the safety valve 3 of the battery cell 2. In the event of a thermal event or degassing of the battery cell 2, the gas from the safety valve 3 will flow into the passage 7, and as soon as the limit pressure is exceeded, the closure plug 6 is pushed out and then accordingly releases the passage 7, allowing the gas to flow out of the passage 7.

[0023] To stabilize the sealing sleeve 5 in the venting opening, it is provided that the wall of the sealing sleeve 5 has, at its first end, a circumferential holding section 10 projecting radially outward relative to the adjacent section of the wall, wherein the holding section 10 engages behind the housing wall on an inner side facing the battery cell 2. Furthermore, it is provided that the wall of the sealing sleeve 5 has, at its end facing away from the battery cell 2, a circumferential support section 11 projecting radially outward, wherein the support section 11 bears against an outer side of the housing wall facing away from the battery cell 2, so that further insertion of the sealing sleeve 5 into the venting opening is prevented by the interaction of the support section 11 with the outer side of the housing wall.

[0024] The insertion of the assembly unit and the pressing of the sealing plug 6 can be carried out using an assembly stamp 12, as shown schematically in the Fig. 2 to 4. The Fig. 2 to 4 show the states during assembly in chronological order. The assembly punch 12 has an outer punch 13 that can be moved in the axial direction Z and an inner punch 14 that is arranged within the movable outer punch 13 and can be moved in the axial direction Z with respect to the outer punch 13. The initial state is shown in the Fig. 2. Starting from this initial state, the outer punch 13 is moved in the axial direction Z to insert the assembly unit into the degassing opening. The outer punch 13 acts exclusively on the sealing sleeve 5. The state after insertion of the assembly unit is shown in the Fig. 3. In this state, the sealing plug 6 is still in the holding position and not in the clamping position. To transfer the sealing plug 6 from the holding position to the clamping position, the inner punch 14 is then moved so that it acts on the sealing plug 6 to press the sealing plug 6 into the clamping position, as shown in the Fig. 4 is shown. List of reference symbols 1 battery module housing 2 battery cells 3 Safety valve 4 locking system 5 Sealing sleeve 6 sealing plugs 7 Through channel 8 Lid section 9 Wall 10 stopping section 11 Support section 12 assembly stamps 13 outer stamps 14 inner stamps Z axial direction

Claims

[1] Method for producing a degassing channel from a battery cell (2) to a degassing opening of a battery module housing (1), comprising the following method steps: - Providing a battery module housing (1), wherein the battery module housing (1) has an interior space for accommodating at least one battery cell (2), wherein the battery module housing (1) has a housing wall with a degassing opening opening into the interior space, - Providing a sealing sleeve (5) and a closure plug (6), wherein the sealing sleeve (5) consists of an elastically deformable material, wherein the sealing sleeve (5) has a first end, a second end opposite the first end in an axial direction (Z), and a through-channel (7) extending from the first end to the second end, wherein a circumferential wall of the sealing sleeve (5) circumferentially delimits the through-channel (7) of the sealing sleeve (5), wherein the closure plug (6) has a cover section (8) for closing the through-channel (7) of the sealing sleeve (5) and has a circumferential wall extending from the cover section (8), wherein the closure plug (6) can be pushed into the sealing sleeve (5) along the axial direction (Z) until a clamping position is reached,wherein in the clamping position an outer peripheral surface of the circumferential wall of the sealing plug (6) rests against an inner peripheral surface of the wall of the sealing sleeve (5) and thereby supports the wall of the sealing sleeve (5) radially inwards, - Pre-assembling the sealing plug (6) in the sealing sleeve (5) to form an assembly unit by inserting the sealing plug (6) along the axial direction (Z) into the sealing sleeve (5) in such a way that the sealing plug (6) is held in the sealing sleeve (5) and can be transferred into the clamping position by further moving the sealing plug (6) along the axial direction (Z), - Inserting the assembly unit into the degassing opening along the axial direction (Z) such that the sealing sleeve (5) reaches an end position in which the sealing sleeve (5) passes through the degassing opening in the axial direction (Z) and the first end projects into the interior, wherein the sealing sleeve (5) is arranged in front of the sealing plug (6) in the insertion direction, - pressing the sealing plug (6) along the axial direction (Z) to transfer the sealing plug (6) into the clamping position for fixing the sealing sleeve (5) in the degassing opening in the end position, wherein in the clamping position the outer circumferential surface of the circumferential wall of the sealing plug (6) bears against the inner circumferential surface of the wall of the sealing sleeve (5) in the radial direction and thereby presses the wall of the sealing sleeve (5) against the inner circumferential surface of the housing wall to tightly close the degassing opening, - introducing the battery cell (2) into the interior of the battery module housing (1), wherein the battery cell (2) is introduced into the interior in such a way that the sealing sleeve (5) lies with the first end sealingly against a cell housing of the battery cell (2), in such a way that a safety valve (3) of the battery cell (2) opens into the through-channel (7) to form a degassing channel from the safety valve (3) to the degassing opening. [2] Method according to claim 1, wherein the battery cell (2) is introduced into the interior space after the assembly unit has been pushed in and after the sealing plug (6) has been pressed in. [3] Method according to claim 1, wherein the battery cell (2) is introduced into the interior space before the assembly unit is inserted and before the sealing plug (6) is pressed in. [4] Method according to one of claims 1 to 3, wherein the wall of the sealing sleeve (5) has at its first end a circumferential holding section (10) projecting radially outwardly relative to the adjacent section of the wall, wherein the holding section (10) in the end position engages behind the housing wall on an inner side facing the battery cell (2). [5] Method according to one of claims 1 to 4, wherein the wall of the sealing sleeve (5) has, at its end facing away from the battery cell (2), a radially outwardly projecting circumferential support section (11), wherein the support section (11) bears against an outer side of the housing wall facing away from the battery cell (2), so that further insertion of the sealing sleeve (5) into the degassing opening is prevented by the interaction of the support section (11) with the outer side of the housing wall. [6] Method according to one of claims 1 to 5, wherein the outer peripheral surface of the wall of the closure plug (6) and the inner peripheral surface of the wall of the sealing sleeve (5) have locking structures corresponding to one another, wherein the locking structures engage in a first locking position during pre-assembly and thereby the closure plug (6) is held in the sealing sleeve (5), wherein the closure plug (6) is spaced from the clamping position in the first locking position. [7] Method according to claim 6, wherein the locking structures engage in a second locking position upon re-pressing, wherein the second locking position corresponds to the clamping position. [8] Method according to one of claims 1 to 7, wherein the insertion of the assembly unit and the subsequent pressing of the closure plug (6) takes place using an assembly punch (12), wherein the assembly punch (12) has an outer punch (13) which is movable in the axial direction (Z) and an inner punch (14) which is arranged within the movable outer punch (13) and which is movable in the axial direction (Z) with respect to the outer punch (13), wherein in order to insert the assembly unit into the venting opening the outer punch (13) is moved and acts on the sealing sleeve (6) and after the insertion the inner punch (14) is moved and acts on the closure plug (6) to subsequent pressing of the closure plug (6) into the clamping position. [9] Method according to claim 5 and claim 8, wherein during the movement of the inner punch (14) for pressing the closure plug (6) into the clamping position, the support section (11) is held clamped between the outer punch (13) and the housing wall. [10] Method according to one of claims 1 to 9, wherein a holding force between the closure plug (6) and the sealing sleeve (5) in the clamped position is designed such that when a predetermined limit pressure in the through-channel (7) is exceeded, the closure plug (6) is completely pressed out of the sealing sleeve (5) to release the through-channel (7) for gas flowing out of the safety valve (3) of the battery cell (2).

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