Connection device for connecting a battery cell of a high-voltage battery to a busbar and battery cell arrangement

Abstract

The invention relates to a connecting device (10) for connecting a battery cell (1) of a high-voltage battery to a busbar (2), wherein the connecting device (10) is made of a metallic material and comprises a base body (15) with a base (12) which can be electrically contacted with the battery cell (1), and a side wall (13) extending in the circumferential direction, wherein a contacting section (14) extending outwards in the circumferential direction is formed on an upper side of the base body (15), which contacting section can be contacted with the busbar (2), wherein the connecting device (10) has a disconnecting mechanism which is designed to irreversibly interrupt a current flow through the connecting device (10) in the event of an overcurrent.

Description

The present invention relates to a connection device for connecting a battery cell of a high-voltage battery to a busbar, wherein the connection device is produced from a metallic material and comprises a base body having a base which is electrically contactable with the battery cell and a side wall extending in the circumferential direction, wherein a contacting section which extends outwards in the circumferential direction and is contactable with the busbar is formed on an upper side of the base body, wherein the connection device has a disconnection mechanism which is configured to irreversibly interrupt a current flow through the connection device in the event of an overcurrent. In addition, the present invention relates to a battery cell arrangement which comprises a battery cell, a busbar and a connection device by means of which the battery cell is electrically connected to the busbar.Electrical contacting of battery cells, in particular round lithium-ion cells, in battery modules is effected in the prior art by busbars / cell connectors and optionally additional bonding wires, which can optionally also have the function of a fuse. An example of this is provided by CN 110036502 B.DE 20 2023 100 128 U1 discloses pot-shaped connecting elements for electrically connecting a battery cell to a busbar. It is also described that the busbar can comprise a connection securing means for interrupting a current flow in the event of an overcurrent.A connection device of the type mentioned at the beginning for connecting a battery cell of a high-voltage battery to a busbar is known, for example, from DE 10 2016 212 909 A1. This connection device has a disconnection mechanism which is designed to irreversibly interrupt a current flow through the connection device in the event of an overcurrent.Further connection devices for connecting a battery cell of a high-voltage battery to a busbar are disclosed in CN 1 08 269 962 A and DE 10 2017 118 416 A1.During operation, in a battery cell arrangement of the generic type, an electric current flows from the busbar through the connection device into the battery cell and from there back again. In the event of a fault, a significantly higher electrical current than usual flows through the connection device, optionally at the level of a short-circuit current. Such an excess current may possibly lead to the connection device being heated above a critical temperature.The invention is based on the object of providing a connection device for connecting a battery cell to a busbar and a battery cell arrangement which, in the event of a fault in the event of an overcurrent occurring, can prevent the connection device from heating beyond a critical temperature with simple means.This object is achieved by a connecting device for connecting a battery cell to a busbar of the type mentioned at the beginning with the features of the characterizing part of claim 1 and by a battery cell arrangement of the generic type with the features of the characterizing part of claim 9.A connection device according to the invention is characterized in that the separating mechanism comprises an interrupted snap ring which is inserted into the base body, wherein the snap ring is produced from a different metallic material than the base body and has a different coefficient of linear expansion, so that the snap ring expands more quickly than the base body in the event of a heat input. In the event of a fault, the snap ring expands more quickly as a result of the heat input which is caused by the excess current, deforms and in the process leads to the base body of the connection device being cut open. As a result of the cross-sectional narrowing which results in this, the current flow can increase to such an extent that the remaining material is melted and the current flow through the connection device is likewise irreversibly interrupted. By irreversibly interrupting the current flow when an overcurrent occurs, further heating of the connection device can be effectively prevented in an advantageous manner. For example, the snap ring may be made of an aluminum alloy.In one embodiment, it is proposed that the separating mechanism has a temperature-sensitive pyroelement which is introduced into the main body of the connection device and is designed to trigger when a critical temperature is exceeded. When the critical temperature caused by the over-current is exceeded, the pyroelement trips. This ensures that the side wall of the base body of the connection device is cut open approximately at the height of the pyroelement, so that the current flow is irreversibly interrupted and further heating of the connection device can be effectively prevented. The pyroelement can already be introduced into the connection device during production and can be formed integrally with the side wall, for example. In an alternative embodiment, it is also possible for the pyroelement to be installed only after the connection of the battery cell to the busbar, in which corresponding contact regions are produced in particular by laser welding, by means of a cohesive, force-fitting or form-fitting connection. This advantageously ensures that during the welding process the thermal energy introduced into the contact regions does not generate any false triggering of the pyroelement.In one embodiment, it is possible for the separating mechanism to comprise an axial slot which is formed in the side wall of the base body. This advantageously supports, for example, the severing of the side wall of the base body initiated when an overflow occurs through the pyroelement. The axial slot can extend in particular over the entire height of the connection device.In one embodiment, there is the possibility that the base body is produced from a copper alloy.In a further embodiment, it can be provided that the separating mechanism comprises material weakenings within the side wall of the base body. These material weakenings, which lead to a reduction in the cross-section in these regions of the side wall due to the reduced material thickness, can be produced, for example, by laser ablation or by deep drawing in a preceding production step. As a result of the cross-sectional narrowing, the current flow in the event of a fault can increase to such an extent that the remaining material is melted and the current flow through the connection device is likewise irreversibly interrupted.A battery cell arrangement according to the invention is distinguished in that the connection device is designed according to one of Claims 1 to 8. The battery cell arrangement has in particular two contact regions between the busbar and the contact section of the connection device and a contact region between the base of the connection device and the battery cell. Preferably, these contact areas are produced by a material-bonded joining method, in particular by laser welding.Further features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings. Figure shows FIG. 1 shows a schematically greatly simplified sectional illustration of a battery cell arrangement having a connection device for connecting a battery cell to a busbar, which is designed according to a first exemplary embodiment of the invention, FIG. 2 shows a plan view of a connection device for connecting a battery cell to a busbar, which is embodied according to a second exemplary embodiment of the invention, FIG. 3 shows a plan view of a connection device for connecting a battery cell to a busbar, which is embodied according to a third exemplary embodiment of the invention, FIG. 4 shows a schematically greatly simplified sectional illustration of a connection device for connecting a battery cell to a busbar, which connection device is designed according to a fourth exemplary embodiment of the invention.A high-voltage battery of an electrically operable vehicle, which may be a battery-electric vehicle or a hybrid-electric vehicle, has a plurality of battery modules, which in turn comprise a plurality of battery cells 1. By means of the high-voltage battery, energy for the operation of at least one electric machine of the electrically operable vehicle can be stored electrochemically.With reference to FIG. 1, a battery cell arrangement 100 is shown therein, which comprises a battery cell 1, which in the present case is a lithium-ion round cell, and a busbar 2.In order to connect the battery cell 1 to the busbar 2 and thereby electrically connect it to the busbar 2, the battery cell arrangement 100 has a connection device 10. The connection device 10 is produced from a metallic material, in particular from a copper alloy, and is therefore designed to be electrically conductive, with the result that it enables an electrical connection of the battery cell 1 to the busbar 2.In the exemplary embodiment shown here, the connection device 10 is designed rotationally symmetrically about its longitudinal axis 11 and has a base body 15 with a base 12 and a side wall 13 extending in the circumferential direction. On an upper side of the base body 15, an annular contacting section 14 extending outward in the circumferential direction is formed. In the exemplary embodiment shown here, the connection device 10 is shaped in such a way that the inner diameter of the base body 15-viewed from the base 12-increases in the direction of the top side. The connection device 10 is thus substantially pot-shaped.In an alternative embodiment, there is also the possibility, for example, that the connection device 10 is shaped such that the inner diameter of the base body 15 is constant. This then results in a cylindrical or sleeve-like basic shape of the base body 15 of the connection device 10.The battery cell arrangement 100 has two contact regions 4 a, 4 bbetween the busbar 2 and the contact section 14 of the connection device 10 and a contact region 4 cbetween the base 12 of the connection device 10 and the battery cell 1. Preferably, these contact areas 4 a, 4 b, 4 care produced by a material-bonded joining method, in particular by laser welding.During operation, an electric current flows out of the busbar 2 through the connection device 10 into the battery cell 1 and from there back again. In the event of a fault, the situation may occur in which a significantly higher electric current flows through the connection device 10 than usual, possibly at the level of a short-circuit current. Such an excess current may possibly lead to heating of the connection device 10 beyond a critical temperature.In order to remedy this problem, it is provided in the first exemplary embodiment illustrated in FIG. 1 that a temperature-sensitive pyroelement 5 is introduced into the connection device 10, which pyroelement forms a separating mechanism of the connection device 10 from a functional point of view in order to interrupt the electrical current flow in the event of an overcurrent occurring in the event of a fault. When the critical temperature caused by the excess current is exceeded, the pyroelement 5 trips. In this case, the side wall 13 of the connection device 10 is cut open at the height of the pyroelement 5, with the result that the electrical current flow is irreversibly interrupted. As a result, further heating of the connection device 10 can be effectively prevented.The pyroelement 5 can already be introduced into the connection device 10 during production. In an alternative embodiment, it is also possible for the pyroelement 5 to be installed by a cohesive, force-fitting or form-fitting connection only after the connection of the battery cell 1 to the busbar 2, in which the contact-making regions 4 a, 4 b, 4 care produced in particular by laser welding. This advantageously ensures that during the welding process the thermal energy introduced into the contact regions 4 a, 4 b, 4 cdoes not generate any false triggering of the pyroelement 5.With reference to FIG. 2, a second exemplary embodiment of the connection device 10 will be explained in more detail below. The basic geometric structure of the connection device 10, which is illustrated in a plan view in FIG. 2, corresponds to that of the first exemplary embodiment. As in the first exemplary embodiment, a temperature-sensitive pyroelement 5, which is not explicitly recognizable in the drawing, is also provided here, which triggers in the event of a fault when a critical temperature, which is caused by the overcurrent, is exceeded. In this exemplary embodiment, the connecting device 10 is additionally provided with an axial slot 6 in the side wall 13, which preferably extends over the entire height of the connecting device 10. However, embodiments are also conceivable in principle in which the axial slot 6 does not extend over the entire height of the connection device 10. By means of the axial slot 6, it is possible to effectively support the severing of the side wall 13 of the base body 15 of the connection device 10 after the triggering of the pyroelement 5.With reference to FIG. 3, a third exemplary embodiment of the connection device 10 is shown there. The basic geometric structure of the connection device 10, which is likewise illustrated in a plan view in FIG. 3, corresponds to that of the first exemplary embodiment. The connecting device 10, which is made of a copper alloy, for example, is additionally provided in this exemplary embodiment with an axial slot 6 in the side wall 13, which preferably extends over the entire height of the connecting device 10. However, embodiments are also conceivable in principle in which the axial slot 6 does not extend over the entire height of the connection device 10. Furthermore, an interrupted snap ring 7 made of metal is inserted into the base body 15 of the connection device 10, which snap ring can be made of an aluminum alloy, for example. This snap ring 7 has a different coefficient of linear expansion than the material (in the present case the copper alloy) from which the connection device 10 is produced. In the event of a fault, the snap ring 7 expands more quickly than the main body 15 due to the heat input caused by the excess current, thereby deforming and ultimately leading to the separation of the side wall 13 of the main body 15 of the connection device 10. In addition, in this third exemplary embodiment, the above-described temperature-sensitive pyroelement 5 can also be provided, which is triggered in the event of a fault and then likewise forms part of the separating mechanism.A fourth exemplary embodiment of the connection device 10 will be explained in more detail below with reference to FIG. 4. The basic geometric structure of the connection device 10 again corresponds to that of the first exemplary embodiment. In this exemplary embodiment, the side wall 13 of the base body 15 of the connection device 10 extending in the circumferential direction has material weakenings 8, which form at least a part of the separating mechanism. These material weakenings 8, which lead to a reduction in the cross-section in these regions of the side wall 13 due to the reduced material thickness, can be produced, for example, by laser ablation or by deep drawing in a preceding production step. As a result of the cross-sectional narrowing, the current flow in the event of a fault can increase to such an extent that the remaining material is melted and the current flow is likewise irreversibly interrupted. In addition, in this fourth exemplary embodiment, a temperature-sensitive pyroelement 5 can also be provided, which is triggered in the event of a fault and then likewise forms part of the separating mechanism.Generally, the release criteria of the disconnect mechanism of the terminal device 10 are defined during the development of the battery cell assembly 100 to not trigger false alarms during operation, for example, due to heating due to charging operations.In principle, it is possible to combine the exemplary embodiments described here-insofar as this is technically expedient-with one another.

Claims

Connection device (10) for connecting a battery cell (1) of a high-voltage battery to a busbar (2), wherein the connection device (10) is produced from a metallic material and comprises a base body (15) having a base (12) which can be electrically contacted with the battery cell (1) and a side wall (13) extending in the circumferential direction, wherein a contacting section (14) which extends outwards in the circumferential direction and can be contacted with the busbar (2) is formed on an upper side of the base body (15), wherein the connection device (10) has a separating mechanism which is configured to irreversibly interrupt a current flow through the connection device (10) in the event of an overcurrent, characterized in that the separating mechanism comprises an interrupted snap ring (7) which is inserted into the base body (15), wherein the snap ring (7) is made of a different metallic material than the base body (15) and has a different coefficient of linear expansion, so that the snap ring (7) expands more quickly than the base body (15) in the event of a heat input.Connection device (10) according to claim 1, characterised in that the separating mechanism has a temperature-sensitive pyroelement (5) which is introduced into the base body (15) of the connection device (10) and is designed to trigger when a critical temperature is exceeded.Connection device (10) according to either of Claims 1 and 2, characterized in that the separating mechanism comprises an axial slot (6) which is formed in the side wall (13) of the base body (15).Connection device (10) according to Claim 3, characterized in that the axial slot (6) extends over the entire height of the connection device (10).Connection device (10) according to one of Claims 1 to 4, characterized in that the snap ring (7) is produced from an aluminium alloy.Connection device (10) according to one of Claims 1 to 5, characterized in that the base body (15) is produced from a copper alloy.Connection device (10) according to one of Claims 1 to 6, characterized in that the separating mechanism comprises weakened material portions (8) within the side wall (13) of the base body (15).Connection device (10) according to claim 7, characterised in that the material weakenings (8) are produced by laser ablation or by deep drawing.Battery cell arrangement (100) comprising a battery cell (1), a busbar (2) and a connection device (10), by means of which the battery cell (1) is electrically connected to the busbar (2), characterized in that the connection device (10) is designed according to one of Claims 1 to 8.

Images