Apparatus for isolating electrical connections to a battery cell during venting - Patents.com

Abstract

The document describes a device for disconnecting an electrical connection to a battery cell (1) during venting, in which a cell pole (3) on the gas vent valve side is connected to an electrical contact point (5) via a connecting conductor (2) that forms a fuse with a contact point (4). In order to provide such a device that requires fewer components and has a compact structure, enables reliable electrical and thermal load protection of adjacent cells of the battery cell being vented, and prevents the spread of thermal runaway, a spacer (6) is provided between the contact point (4) and the contact point (5) to electrically insulate the contact point (4) from the contact point (5) and hold the cell pole (3) during venting.

Description

[Technical field]

[0001] The invention relates to a device for isolating an electrical connection to a battery cell during venting, in which the cell pole on the side of the venting valve is connected at its contact point to an electrical contact point via a connecting conductor forming a safety fuse. [Background technology]

[0002] For example, the failure of a battery cell due to an individually damaged cell is regularly accompanied by an uncontrollable escape of hot gases and can on the other hand result in a self-reinforcing heat-generating chain reaction known as "thermal runaway". In such cases, in order to electrically disconnect the corresponding battery cell from the cell combination on the one hand and to protect the surrounding battery cells from the escaped hot gases on the other hand, contact devices have already been conceived for the battery cell ends with two housings located opposite each other with respect to the through-openings, with connecting conductors being provided through the through-openings and via which the cell poles of the battery cells on the gas vent valve side are connected to the electrical contact points. In this case, the cable cross-section of the connecting conductor is selected in such a way that it melts due to the overcurrent occurring in the event of a fault or due to the escaped hot gases and thus the electrical connection is separated. Moreover, in order to protect the adjacent battery cells from thermal damage, a ceramic flame-retardant plate for the battery cell to be protected can be integrated into the housing. As a result, the battery cells integrated into the housing are thermally isolated from the hot gases or, in the worst case, are also protected against possible fires. However, such flame-retardant boards have the disadvantage that, due to their dimensions, they are unable to withstand the effects of the pressure of hot gases and therefore are unable to fulfil their function.

[0003] Furthermore, in this connection, it has been shown that in the case of a cell defect and a pressure rise linked to the cell defect in the corresponding battery cell, not only does hot gas usually escape, but also the electrode windings of the battery cell can escape from the battery cell through the through-openings of the contact device, as the pole cap on the gas vent valve side comes off due to pressure limitation. This subsequently risks a short circuit between the exposed electrode windings and the adjacent cell, which is already electrically isolated on the basis of the fuse. As a result, the heat generation caused by the short circuit leads to the propagation of a "thermal runaway" to the adjacent battery cell. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is therefore to provide a device of the type described at the beginning, which allows reliable electrical and thermal load protection of adjacent cells of a battery cell to be vented with low component requirements and a compact structure, and which prevents the spread of thermal runaway. [Means for solving the problem]

[0005] The invention solves this problem in that between the contacts and the contact points there is provided a spacer which electrically insulates the contacts from the contact points and holds the cell poles in the event of venting. As a result of these features, in the event of venting, on the one hand the electrical connection of the defective battery cell to the contact points can be separated by melting the connecting conductors, and on the other hand the spacer can prevent the pole cap on the side of the venting valve from being removed from the battery cell. As a result, the electrode winding cannot be removed from this battery cell, but is held in the defective battery cell. In this case the spacer forms a stop for the pole cap on the side of the venting valve of the defective battery cell, particularly in the longitudinal direction of the cell, whereby if the pole cap on the side of the venting valve is actually locked by the spacer, an electrical connection to the contact points is avoided due to the electrically insulating effect of the spacer. With regard to thermal stress protection, the device according to the invention can basically be equipped with known flame-retardant plates, but particularly favorable constructional conditions arise if the spacer itself forms the thermal and flame protection.

[0006] To facilitate the evacuation of the hot gases, in this case to ensure the separation of the electrical connection, the spacer together with the connecting conductor can be inserted through a degassing channel extending between the electrical contact and the cell pole on the side of the degassing valve. In this way, the connecting conductor is exposed to the flowing hot gas, which makes it possible to melt the connecting conductor regardless of the current strength occurring. Favorable conditions for a compact design as well as a reliable evacuation of the hot gases arise, for example, if the degassing channel has a height of 2-10 mm, preferably 3-6 mm.

[0007] If the connecting conductor is connected to the cell pole and the electrical contact point on the degassing valve side in a material-engaging manner and if the connecting conductor extends from the contact point to the cell pole against a restoring force, a spatial separation of the detached parts can be ensured when the connecting conductor melts, and thus a continuous electrical connection can be avoided. For example, the connecting conductor can be welded or soldered to the cell pole and the contact point on the degassing side. With regard to the contact point, a material-engaging connection means, for example, that the connecting conductor and the contact point are integrally formed, i.e. are connected to each other on the material.

[0008] Since battery cells are subjected to electrical and therefore mechanical loads in a cyclical manner in normal operation, particularly in connection with battery modules, tensile / compressive load cycles acting on the connecting conductors, in particular in the bundling direction, can lead to fatigue cracks in the connecting conductors over time. Against this background, in order to reduce the mechanical loads on the connecting conductors without compromising the protective function of the spacer, it is proposed that the connecting conductors run in a spiral around the spacer. With this measure, mechanical tolerance compensation can occur in and against the bundling direction, since the spiral configuration allows for a certain stretching or compression of the connecting conductors in and against the bundling direction.

[0009] To allow for simple assembly and a compact construction, the spacer can be integrated into the gap in which the connecting conductor extends from the contact point. In the case of a helical connecting conductor, the spacer extends along the main axis of the helix formed by the helical shape of the connecting conductor and thus passes through the envelope of the helix.

[0010] In this connection, it is recommended that the connecting conductor is formed as a double helix so that the fuse is reliably removed regardless of the amount of hot gas that escapes. With these measures, the ratio of the free surface of the connecting conductor to its mass is increased, which further promotes melting due to the escape of hot gas. If the two conductor tracks of the double helix meet opposite each other at a common connection point to the cell pole of the battery cell on the gas venting valve side, the resulting self-centering of the contacts can facilitate the welding process for the material-engaged connection and electrical connection of the contacts with the cell pole of the battery cell on the gas venting side.

[0011] In order not to induce internal stresses as a result of cell breathing caused by changes in operating parameters, which may damage the device or the battery cell itself despite the reliable spacer function, it is recommended that the spacer is spaced away from the cell pole on the side of the venting valve during normal operation. In this case, the minimum distance between the spacer and the cell pole on the side of the venting valve must be taken into account. As a result, the minimum distance is usually measured towards the cell pole on the side of the venting valve as well as from the end face of the spacer to which this cell pole is closest. That minimum distance can be, for example, in the range of 0.1-5 mm, preferably in the range of 0.5-2 mm, on the one hand to allow sufficient outflow of hot gases and, on the other hand, to prevent misalignment of the cell poles and thus short circuits during venting.

[0012] With regard to the spacer, in spite of its compact structure, in order to protect also the areas directly adjacent to the contact points (where, for example, the adjacent battery cells are) from electrical and thermal stresses and to simplify the assembly process, it is envisaged that the spacer has a flame-retardant base and a holding extension protruding from this flame-retardant base in the direction towards the cell pole on the gas vent valve side. As a result, the spacer uses the flame-retardant base to prevent the hot gas from diffusing, while at the same time ensuring, via the holding extension, that there is sufficient free space between the gas vent valve and the flame-retardant base for this hot gas to be led out. It is thus also possible to prevent the protruding cell pole cap or the outgoing electrode winding from blocking the discharge of the hot gas. For example, the spacer can be a shield with a disk-shaped flame-retardant base and a cylindrically shaped holding extension. As a result of these features, the spacer can thus be formed as an integral part. This part can preferably be formed to be rotationally symmetrical with respect to the longitudinal axis of its holding extension. To allow simple manufacturing conditions, the spacer can be manufactured as an injection-molded part. To obtain a sufficient thermal protection effect, a heat-resistant and flame-retardant synthetic resin material can be used. Furthermore, a guide surface extending from the cylindrical holding extension to the disk-shaped flame-retardant base can be formed by an umbrella- or mushroom-shaped configuration of the spacer. This guide surface further promotes the conduction of hot gases to the discharge channel. If the holding extension is surrounded by a connecting conductor, such a guide surface can also pass a targeted current through the connecting conductor, so that the connecting conductor is reliably melted.

[0013] In this connection, it is recommended that the retention extension comprises an insulating chamber, so as to improve the effect of the spacer as a thermal protection while maintaining simple manufacturing conditions. For example, the retention extension may form a cavity which acts as a thermal insulator and reduces the spread of heat affecting the spacer during degassing. Preferably, this cavity may open towards the flame-retardant base.

[0014] In order to simplify the connection with the adjacent battery cells and to spatially fix the device according to the invention with play with respect to the battery cells, it is provided to form a cell receptacle for the battery cells whose contacts are connected in the bundling direction, the cell receptacle being integrated with the connection conductors in the base body and being delimited by a stop in the bundling direction. For example, the cell receptacle can be delimited by a contact spring base, from which a contact tongue projects in the bundling direction for surrounding the accommodated battery cell on the sheath side. However, as mentioned above, the flame-retardant base of the spacer can be provided between the contact spring base and the cell receptacle. According to a particularly preferred embodiment, the contact spring can be formed in one piece with the connection conductors and the stop barb. In this case, the contact spring can be formed, for example, as a deep-drawn part that has been punched out beforehand from the contact plate. For example, the stop barb can be formed to engage behind or below any undercuts in the base body.

[0015] In this connection, in order to prevent damage to the connection points, it is recommended that the base body forms latch arms for circumferential engagement in the grooves of the adjacent battery cells, which limits the freedom of movement of the battery cells connected to the contact points via the connection conductors in the bundling direction, thereby preventing mechanical damage or even breakage of the connection conductors or the connection points. Furthermore, these measures make it possible to center the cell poles on the degassing valve side relative to the connection conductors, thereby facilitating the welding process, so that the assembly process is further improved.

[0016] The subject matter of the invention is illustrated in the drawings. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is an exploded view of the device according to the invention. [Diagram 2] 1 is a schematic cross-sectional view of the device according to the invention in a normal operating mounting position; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The device according to the invention for disconnecting the electrical connection to a battery cell 1 in the event of venting has a connecting conductor 2 forming a fuse, which connects a cell pole 3 of the battery cell 1 on the side of the venting valve with an electrical contact point 5 in the form of a contact spring base at a connection point 4. Between the contact point 4 and the contact point 5 a spacer 6 is provided which electrically insulates the contact point 4 from the contact point 5 in the event of venting and holds the cell pole 3. Thus, in the event of venting, the device according to the invention allows, on the one hand, for the electrical connection of the defective battery cell 1 to be disconnected by melting of the connecting conductor 2, and, on the other hand, the spacer 6 prevents the pole cap 7 on the side of the venting valve from coming off the battery cell 1. As a result, the electrode winding cannot come off this battery cell, but is held in the defective battery cell 1.

[0019] As can be seen from the embodiment of the device according to the invention shown in figures 1 and 2, the contact points 5 form cell receptacles 8 for adjacent battery cells 9 relative to the bundling direction F, which are integrated with the connecting conductors 2 into a base body 10 and are delimited relative to the bundling direction F by stop hooks 11. In addition, the base body 10 can form latch arms 12 for engaging circumferentially in grooves 13 of the adjacent battery cells 1. As depicted in figure 1, contact tongues 14 can protrude in the bundling direction F from the contact points 5 formed as contact spring bases for surrounding the accommodated battery cells 9 on the sheath side.

[0020] In particular, it can be seen from Fig. 2 that the spacer 6 together with the connecting conductor 2 can be inserted through a venting channel 15 for discharging hot gases, which extends between the electrical contact point 5 and the cell pole 3 on the side of the venting valve. In the illustrated embodiment of the device according to the invention, the connecting conductor 2 as a double helix runs around the spacer 6, the conductor tracks of the connecting conductor 2 joining together at the contact point 4. In this case, the spacer 6 can be integrated into the gap 16 into which the connecting conductor 2 widens from the contact point 5. Preferably, the contact point 4 can be connected in a material-engaging manner with the cell pole 3, for example using a welding process.

[0021] The spacer 6 may have a disc-shaped flame-retardant base 17, preferably with the diameter of the battery cell, and a retaining extension 18 protruding from this flame-retardant base 17 in the direction towards the cell pole 3 on the side of the degassing valve. In this case, the spacer 6 can be easily snapped into the cell receiving part 8 and can be stopped in the binding direction F, for example by the bearing end of the contact point 5. In addition, in order to further facilitate the evacuation of the hot gases into the degassing channel 15, the spacer 6 may form a guide surface 19 extending from the retaining extension 18 to the flame-retardant base 17. The retaining extension 18 may be provided with an insulating chamber 20 for improved thermal protection. For example, the spacer 6 may be formed with a cavity that is open towards the flame-retardant base 17. As can be seen in particular from FIG. 2, the flame-retardant base 17 may be provided between the contact point 5 of the spacer 6 and the cell receiving part 8. As is also evident from FIG. 2, the spacer 6 may be spaced away from the cell pole 3 in order, on the one hand, to allow a sufficient outflow of the hot gases and, on the other hand, to prevent the displacement of the cell poles and thus a short circuit during degassing. This application relates to the invention described in the claims, but also includes the following as other aspects. 1. A device for isolating electrical connections to a battery cell (1) during venting, comprising: In this device, the cell pole (3) on the gas vent valve side is connected to the electrical contact point (5) via the connecting conductor (2) which forms a fuse with the contact (4), A device characterized in that a spacer (6) is provided between the contact (4) and the contact point (5) to electrically insulate the contact (4) from the contact point (5) and hold the cell pole (3) when venting. 2. 2. The device according to claim 1, characterized in that the spacer (6), together with the connecting conductor (2), passes through a degassing channel (15) extending between the electrical contact point (5) and the cell pole (3) on the degassing valve side. 3. 3. The device according to claim 1 or 2, wherein the connecting conductor (2) extends in a spiral shape around the spacer (6). 4. 4. The device according to claim 3, characterized in that the connecting conductor (2) is formed as a double helix. 5. 5. The device according to any one of claims 1 to 4, characterized in that the spacer (6) is incorporated into a gap (16) in which the connecting conductor (2) expands from the contact point (5). 6. 6. The device according to any one of 1 to 5 above, wherein the spacer (6) is spaced apart from the cell electrode (3) on the gas vent valve side during normal operation. 7. 7. The device according to any one of claims 1 to 6, wherein the spacer (6) has a flame-retardant base (17) and a retaining extension portion (18) protruding from the flame-retardant base (17) in a direction toward the cell electrode (3) on the gas vent valve side. 8. 8. The apparatus of claim 7, wherein the retention extension (18) comprises an insulating chamber (20). 9. The device according to any one of 1 to 8 above, characterized in that the contact points (5) form cell receiving portions (8) for adjacent battery cells (9) in the bundling direction (F), the cell receiving portions (8) being incorporated into the connecting conductors (2) and the base body (10) and being separated by stops in the bundling direction (F). 10. 10. The device according to claim 9, wherein the base (10) forms a latch arm (12) for circumferentially engaging in a groove (13) of an adjacent battery cell (1).

Claims

1. A device for isolating an electrical connection to a battery cell (1) during degassing, comprising: In this device, the cell pole (3) on the gas vent valve side is connected to the electrical contact (5) via a connecting conductor (2) which forms a fuse with the contact (4), A device characterized in that a spacer (6) is provided between the contact (4) and the contact point (5) to electrically insulate the contact (4) from the contact point (5) during venting and to hold the cell pole (3) in the longitudinal direction of the cell.

2. 2. The device according to claim 1, characterized in that the spacer (6) together with the connecting conductor (2) passes through a degassing channel (15) extending between the electrical contact point (5) and the cell pole (3) on the degassing valve side.

3. 3. The device according to claim 1, wherein the connecting conductor (2) extends in a spiral shape around the spacer (6).

4. 4. The device according to claim 3, characterized in that the connecting conductor (2) is formed as a double helix.

5. 5. The device according to claim 1, characterized in that the spacers (6) are integrated into the gaps (16) into which the connecting conductors (2) extend from the contact points (5).

6. 6. The device according to claim 1, wherein the spacer (6) is spaced from the cell pole (3) on the side of the vent valve during normal operation.

7. 7. The device according to claim 1, wherein the spacer (6) has a flame-retardant base (17) and a retaining extension (18) protruding from the flame-retardant base (17) in the direction towards the cell pole (3) on the gas vent valve side.

8. The apparatus of claim 7, wherein the retention extension (18) comprises an insulating chamber (20).

9. 9. The device according to claim 1, wherein the contact points (5) form cell receptacles (8) for adjacent battery cells (9) with respect to the bundling direction (F), the cell receptacles (8) being integrated into the connecting conductors (2) and into the base body (10) and being separated by stops with respect to the bundling direction (F).

10. 10. The device according to claim 9, characterized in that the base (10) forms latch arms (12) for circumferentially engaging in grooves (13) of adjacent battery cells (1).

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