BATTERY CELL WITH CLAMPING CONTACT, BATTERY SYSTEM AND MOTOR VEHICLE

Description

[0001] The present invention relates to a battery cell for a battery system for a motor vehicle. Furthermore, the invention relates to a battery system for a motor vehicle having a generic battery cell and a motor vehicle having a generic battery system.

[0002] Cylindrical and prismatic battery cells are known that have a safety device, such as a current interrupt device (CID) or an overcharging safety device (OSD), to protect the battery cell, particularly against thermal runaway. Such safety devices typically have a safety circuit that interrupts an electrical connection between the active material of the battery cell, which is combined, for example, into a cell coil, and an electrical terminal leading out of the battery cell in the event of a critical internal pressure, a critical internal temperature, or a critical gas concentration within the cell. Such safety devices are currently very difficult to implement for battery cells designed as pouch cells.

[0003] From DE 10 2016 110 778 A1, which forms the basis for the preamble of claim 1, a battery cell designed as a pouch cell with a protective device is known, in which an electrical coupling of a first inner conductor of the battery cell to a second inner conductor of the battery cell can be severed depending on an expansion of the battery cell. For this purpose, the second inner conductor is held on a lower cell wall, for example via an adhesive layer, and electrically coupled to a first section of the first inner conductor via a bent section. The first section is held on an upper cell wall of the battery cell, for example via an adhesive layer, and electrically coupled to a second section of the first inner conductor via a predetermined breaking point. The second section is coupled to the second inner conductor via an electrically insulating adhesive layer.When the battery cell expands to a critical extent, the upper cell wall is removed from the lower cell wall to such an extent that the bent section is at least partially plastically deformed and the predetermined breaking point is broken. The electrical coupling between the first section and the second section of the first inner conductor is thus interrupted. In this way, the battery cell can be automatically separated from the rest of the battery system. The bent region is designed to retain some of the plastic deformation upon re-deformation of the battery cell, so that an interruption in the electrical coupling between the first section and the second section of the first inner conductor continues to exist. Documents EP 3 267 512 A1 and EP 3 627 591 A1 disclose further battery cells with an electrical separating device.

[0004] Known pouch-shaped battery cells with a protective device have the disadvantage that a significant deformation of the cell wall is required to interrupt the electrical coupling. This is particularly problematic in battery systems with a compression device that compresses the battery cells to increase performance and extend their service life.

[0005] It is therefore an object of the present invention to eliminate, or at least partially eliminate, the disadvantages described above in a battery cell. In particular, the object of the present invention is to provide a battery cell, a battery system, and a motor vehicle that ensure, in a simple and cost-effective manner, improved interruption of the electrical coupling of a defective battery cell to other battery cells of the battery system.

[0006] The above problem is solved by the patent claims. Accordingly, the problem is solved by a battery cell for a battery system for a motor vehicle having the features of independent claim 1, by a battery system for a motor vehicle having the features of independent claim 8, and by a motor vehicle having the features of independent claim 9.

[0007] Further features and details of the invention emerge from the dependent claims, the description, and the drawings. Features and details described in connection with the battery cell according to the invention naturally also apply in connection with the battery system according to the invention and the motor vehicle according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0008] According to a first aspect of the invention, the object is achieved by a battery cell for a battery system for a motor vehicle. The battery cell has a flexible cell wall, a cell interior formed by the cell wall, active material arranged in the cell interior for storing and releasing electrical energy, an electrode arranged in the cell interior and electrically coupled to the active material, and a conductor protruding from the cell interior and electrically coupled to the electrode in an initial state. In the initial state, a pressure difference between an internal cell pressure in the cell interior and an external cell pressure outside the cell interior is smaller than a predetermined pressure threshold.According to the invention, the electrode and the conductor are pressed against one another in the initial state to establish the electrical coupling between a first wall section and a second wall section of the cell wall, wherein the battery cell has a detachment device for removing the electrical coupling in an interrupted state. The pressure difference in the interrupted state corresponds to the pressure threshold value, wherein the detachment device is designed to follow, with the conductor or the electrode, a movement of the first wall section away from the second wall section from the initial state to the interrupted state such that a gap is formed between the conductor and the electrode in the interrupted state.The detachment device comprises a pressure device, wherein the pressure device in the initial state has a prestress maintained by the pressure difference and is designed to press the arrester away from the electrode or the electrode away from the arrester in the direction of the first wall section.

[0009] The battery system is preferably designed to operate an electric motor and power electronics of the motor vehicle. The battery cell is preferably designed as a pouch cell. The cell wall is made of a flexible material, such as aluminum or the like. The cell wall is preferably foil-like. Furthermore, the cell wall has at least one seam to form an externally sealed cell interior. The seam is preferably designed as a welded seam, adhesive seam, or the like.

[0010] The cell wall is flexible and forms the cell interior. Seams of the cell walls are preferably sealed by welding, gluing, or the like, preferably in such a way that the cell interior is sealed gas-tight. Due to the flexible design of the cell wall, the cell interior can be expanded by increasing the internal cell pressure, for example by cell gas escaping from the active material, in particular as a result of thermal runaway of the active material. The external dimensions of the battery cell, such as a thickness, can be increased in this way. The cell wall preferably comprises aluminum or is formed from aluminum. More preferably, the cell wall has an electrically insulating material, in particular in the form of a continuous layer, in particular on an outward-facing wall side, particularly preferably on both sides.

[0011] The active material is arranged in the cell interior. In the context of the invention, an active material is understood to be a material or a material mixture that ensures the storage and release of electrical energy via the battery cell's conductors. The active material preferably comprises lithium ions. According to the invention, the active material can be arranged in the cell interior in layered form, in particular stacked or folded.

[0012] The electrode is designed to provide the electrical coupling of the active material to the arrester. The arrester is designed to provide the electrical coupling of the electrode to other components of the battery system, such as additional battery cells, in particular within the context of a series connection or series circuit, or a main arrester of the battery system for delivering electrical energy to electrical consumers of the motor vehicle and for introducing electrical energy to charge the battery cells. To provide the electrical coupling, the arrester device has the first arrester section and the second arrester section.

[0013] In the initial state, the internal cell pressure is lower than the external cell pressure. Preferably, the internal cell pressure is lower than atmospheric pressure; more preferably, the internal cell pressure is a vacuum, in particular a fine vacuum or high vacuum. The cell wall is preferably designed and sealed to maintain the vacuum. More preferably, the external cell pressure corresponds to atmospheric pressure. The electrode and the arrester are pressed against one another by the pressure difference between the internal cell pressure and the external cell pressure between the first wall section and the second wall section of the cell wall. This ensures a reliable and vibration-resistant electrical coupling between the electrode and the arrester. Furthermore, the active material of the battery cell is thus electrically coupled to the arrester.

[0014] The detachment device is designed to interrupt the electrical coupling between the electrode and the conductor in the interrupted state. For this purpose, the detachment device is designed to move the conductor or the electrode together with the first wall section from the initial state to the interrupted state. An interrupted state is understood to be a state in which the electrical coupling between the electrode and the conductor is completely interrupted. A further separation as well as a renewed approach of the electrode and conductor without re-establishing the electrical coupling can also be referred to as an interrupted state within the scope of the invention. In the interrupted state, with a non-opened cell wall, the internal cell pressure is preferably greater than in the initial state. Furthermore, a distance between the first wall section and the second wall section is greater in the interrupted state than in the initial state.In this way, a gap is formed between the electrode and the conductor in the interrupted state. According to the invention, the detachment device can be designed as a component without a mechanical energy storage device or as a component with a mechanical energy storage device. The mechanical energy storage device is designed to store energy in the initial state and to release it in the interrupted state. Preferably, the detachment device has a reset lock to prevent a return from the interrupted state to the initial state. This ensures that an independent re-electrical coupling of the battery cell after an independent electrical decoupling is avoided.

[0015] The pressure threshold is preferably determined based on the mechanical, chemical, or electrochemical characteristics of the battery cell and determines the pressure difference at which the electrical coupling of the battery cell from the rest of the battery system should be separated in order to prevent or at least reduce further damage to the battery cell and the battery system. The pressure threshold is preferably below a critical pressure at which the seams of the cell wall threaten to open. This prevents cell gas from escaping through a defective seam, thus preventing the pressure threshold in the cell interior from being reached or from being reached with a significant delay, for example, if the battery cell is already thermally failing.

[0016] According to the invention, the detachment device comprises a pressure device, wherein the pressure device in the initial state has a prestress maintained by the pressure difference and is designed to press the arrester away from the electrode or the electrode away from the arrester in the direction of the first wall section. In the context of the invention, a pressure device is understood to mean a device for storing mechanical energy. The pressure device is designed to provide a pressure force by means of which - in the absence of a sufficient counterforce - the electrode and the arrester can be moved away from one another, for example by pressing against the electrode and / or the arrester. The pressure device is compressed by the pressure difference between the external cell pressure and the internal cell pressure in the initial state.When the pressure difference decreases to such an extent that the pressure threshold is reached, the pressure device is expandable to force the electrode and arrester apart. When using a pressure device, mechanical decoupling from the first wall section is possible, ensuring, for example, a joint movement of the first wall section and the arrester or electrode between the initial state and the interruption state. Once the pressure device has reached a relaxed state, further movement of the first wall section away from the relaxed pressure device could still be possible. This has the advantage that reliable electrical decoupling of the electrode and arrester can be achieved using simple means and in a cost-effective manner.

[0017] The battery cell preferably has a signaling device which is designed to output a signal when the electrode is electrically decoupled from the arrester. The signaling device preferably has a fixed first electrical contact and a second electrical contact which can move along with the first wall section. In the initial state, the first electrical contact and the second electrical contact are preferably separated from one another. In the interrupted state, the first electrical contact preferably contacts the second electrical contact in such a way that an electrical circuit is closed. According to the invention, the signaling device can be arranged inside and / or outside the battery cell. A signaling device arranged outside the battery cell has the advantage that no signal lines have to be led out of the battery cell.In this way, the electrical decoupling of a specific battery cell in a battery system can be detected reliably, easily and cost-effectively.

[0018] A battery cell according to the invention has the advantage over conventional battery cells that the electrical coupling between the electrode and the arrester can be automatically interrupted using simple means and in a cost-effective manner when the ratio between the internal cell pressure and the external cell pressure exceeds a critical limit. The effective coupling of the release device with the pressure difference between the internal cell pressure and the external cell pressure eliminates the need for a measurement of the internal cell pressure and a control device for controlling the actuator device. Thus, the complexity of the battery cell system is significantly reduced, and the operational reliability of the battery cell is significantly improved compared to conventional battery cells.

[0019] According to the invention, it is preferred that the pressure device comprises a compression spring and / or a pressure cylinder and / or a pressure foam, or that the pressure device is realized by an internal stress of the arrester or the electrode. A compression spring is preferably designed as a helical spring. A pressure foam is a porous material which can be compressed while building up a compressive stress. According to the invention, the porous material can be designed with open pores and / or closed pores. In a closed pore design, an inert gas, such as nitrogen, argon or the like, in particular with an inert gas content of at least 95%, is preferably arranged in the pores. A pressure piston is preferably arranged and guided in a translational manner in a pressure cylinder. A pressure medium in the pressure cylinder is preferably non-flammable or non-explosive, such as an inert gas.To provide the residual stress, the respective arrester or electrode comprises an elastic material. The arrester or electrode is preferably designed as a leg spring for this purpose. Such a pressure device can be manufactured and prestressed using simple means and in a cost-effective manner. Furthermore, such a pressure device ensures reliable interruption of the electrical coupling between the electrode and the arrester.

[0020] The detachment device further preferably comprises a holding device, wherein the holding device is designed to hold the arrester or the electrode on the first wall section. By means of the holding device, a movement of the arrester or the electrode can be coupled to the first wall section in such a way that the arrester or the electrode follows the movement of the first wall section as long as the holding device is intact. Accordingly, the holding device is preferably designed such that at least the interrupted state can be achieved. The holding device is preferably designed to ensure holding over the entire freedom of movement of the first wall section when the cell interior expands. This has the advantage that an electrical decoupling of the electrode and arrester is ensured when the cell interior expands using simple means and in a cost-effective manner.

[0021] In a particularly preferred embodiment of the invention, the holding device has an adhesive point and / or soldering point and / or welding point and / or crimping point. The adhesive point preferably has an adhesive that is stable in the operating temperature range of the battery cell and at temperatures during thermal runaway of the battery cell at least long enough to ensure reliable electrical decoupling of the electrode and conductor when the first wall section is moved away. Alternatively, the holding device can have a hook device for hooking the conductor or the electrode. This has the advantage that holding on to the first wall section and thus reliable electrical decoupling of the electrode and conductor is ensured using simple means and in a cost-effective manner.

[0022] Preferably, in the initial state, the electrode and the arrester are pressed against each other by the pressure difference between the internal cell pressure and the external cell pressure between the first wall section and the second wall section. The pressure difference acts against any pressure device such that the pressure device remains compressed and thus prestressed. According to the invention, the cell wall may have a plastically deformable support device. The support device is preferably stress-free or at least substantially stress-free in the initial state and in the interrupted state and is plastically deformable by the movement of the first wall section. This prevents the cell wall from collapsing again when the pressure between the internal cell pressure and the external cell pressure equalizes.This has the advantage that reliable electrical coupling and decoupling of the electrode and arrester is ensured using simple means and in a cost-effective manner.

[0023] According to a preferred embodiment of the invention, the electrode or the conductor has a joint section between two base sections to improve a joint movement with the first wall section. The joint section is designed such that, when the first wall section moves from the initial state to the interrupted state, the adjacent base sections are pivoted relative to one another about a joint axis extending through the joint section. The joint section thus makes it easier to predefine a movement. Furthermore, a joint section has the advantage that the mechanical resistance of the electrode or the conductor can be reduced using simple means and in a cost-effective manner, thus improving the joint movement with the first wall section.

[0024] Particularly preferably, the joint section has a kink and / or a reduced cross-section and / or increased ductility compared to the adjacent base regions. The kink preferably has an angle of more than 120°. The reduced cross-section is preferably between 10% and 30% of the cross-section in one direction. The increased ductility can be achieved, for example, by using a different material or a local heat treatment. This has the advantage of improving the joint movement with the first wall section using simple means and in a cost-effective manner.

[0025] According to a second aspect of the invention, the object is achieved by a battery system for a motor vehicle. The battery system has a system housing. According to the invention, a plurality of battery cells according to the invention are arranged within the system housing. The system housing is preferably formed from a relatively rigid material in order to protect the battery cells from external mechanical influences, such as those resulting from a collision of the motor vehicle. The battery cells are preferably electrically interconnected, for example in a series circuit and / or parallel circuit. The battery cells are preferably combined to form one or more battery cell stacks. Furthermore, the battery system preferably has, for one or more, preferably all, battery cell stacks, a compression device for compressing the battery cells of the respective battery cell stack.The battery system preferably has two or more main conductors for electrically coupling the battery system to the motor vehicle. The battery system is preferably designed to operate an electric motor and power electronics of the motor vehicle.

[0026] The battery system according to the invention provides all of the advantages already described for a battery cell according to the first aspect of the invention. Accordingly, the battery system according to the invention has the advantage over conventional battery systems that the electrical coupling between the electrode and the arrester can be automatically interrupted using simple means and in a cost-effective manner when the ratio between the internal cell pressure and the external cell pressure exceeds a critical limit. The active coupling of the release device with the pressure difference between the internal cell pressure and the external cell pressure eliminates the need for a measurement of the internal cell pressure and a control device for controlling the actuator device. Thus, the complexity of the battery cell system is significantly reduced, and the operational reliability of the battery cell system is significantly improved compared to conventional battery cell systems.

[0027] According to a third aspect of the invention, the object is achieved by a motor vehicle. The motor vehicle has an electric drive system with an electric motor for driving the motor vehicle. According to the invention, the drive system has a battery system according to the invention for supplying the electric motor with electrical energy. The battery system is electrically coupled to the electric motor, preferably via power electronics for operating the electric motor. According to the invention, the motor vehicle can have a plurality of electric motors for driving the motor vehicle, in particular an electric motor for driving a front axle of the motor vehicle and an electric motor for driving a rear axle of the motor vehicle.

[0028] The motor vehicle according to the invention provides all of the advantages already described for a battery cell according to the first aspect of the invention and for a battery system according to the second aspect of the invention. Accordingly, the motor vehicle according to the invention has the advantage over conventional motor vehicles that the electrical coupling between the electrode and the arrester can be automatically interrupted using simple means and in a cost-effective manner when the ratio between internal cell pressure and external cell pressure exceeds a critical limit. The active coupling of the release device with the pressure difference between internal cell pressure and external cell pressure eliminates the need for a measurement of the internal cell pressure and a control device for controlling the actuator device.This further reduces the complexity of the motor vehicle and significantly improves its operational safety compared to conventional motor vehicles.

[0029] A battery cell according to the invention, a battery system according to the invention, and a motor vehicle according to the invention are explained in more detail below with reference to the drawings. They show schematically: Figure 1 shows a sectional view of a battery cell according to a preferred first embodiment of the invention in an initial state, Figure 2 shows a sectional view of the battery cell from Figure 1in an interrupted state, Figure 3 shows a sectional view of a battery cell according to a preferred second embodiment of the invention in an interrupted state, Figure 4 shows a sectional view of a battery cell according to a preferred third embodiment of the invention in an interrupted state, Figure 5 shows a sectional view of a battery system according to a preferred embodiment of the invention, and Figure 6 shows a side view of a preferred embodiment of a motor vehicle according to the invention.

[0030] Elements with the same function and mode of action are listed in the Figures 1 to 6 each provided with the same reference numerals.

[0031] In Fig. 11 shows a schematic sectional view of the battery cell 1 according to a preferred first embodiment of the invention in the initial state A. The battery cell 1 has a cell wall 4, which forms a cell interior 5 and is hermetically sealed to the outside. Active material 6 is arranged in several layers in the cell interior 5 for storing and releasing electrical energy. The active material 6 is electrically coupled to the electrode 7 of the battery cell 1. A conductor 8 of the battery cell 1 leads out of the cell interior 5. The electrode 7 and the conductor 8 are pressed together between a first wall section 4a of the cell wall 4 and a second wall section 4b of the cell wall 4 under the influence of a pressure difference between an internal cell pressure in the cell interior 5 and an external cell pressure outside the cell interior 5, and are thus electrically coupled to one another.A release device 9, designed as a pressure device 11, is arranged in a tensioned state between the discharge device 8 and the second wall section 4b. The pressure device 11 represents a counterforce to the compressive force due to the pressure difference.

[0032] Fig. 2 shows the battery cell 1 according to the Fig. 1illustrated preferred first embodiment of the invention in the interruption state U schematically in a sectional view. In the interruption state U, the pressure difference between the internal cell pressure and the external cell pressure is increased by increasing the internal cell pressure such that the first cell wall section 4a is moved away from the second cell wall section 4b. Due to the lack of pressure force against the first cell wall section 4a and the second cell wall section 4b, the arrester 8 is moved away from the electrode 7 by means of the pressure device 11 having a compression spring 12. In this way, a gap 10 is formed between the electrode 7 and the arrester 8 and the electrical coupling between the electrode 7 and the arrester 8 is canceled.

[0033] In Fig. 3The battery cell 1 according to a preferred second embodiment of the invention is shown schematically in a sectional view in the interrupted state U. The battery cell 1 according to the preferred second embodiment differs from the battery cell 1 according to the preferred first embodiment in the design of the pressure device 11 and the conductor 8. The pressure device 11 has a pressure foam 13 instead of a compression spring 12. The conductor 8 has a joint section 8b designed as a bend 16 between two base sections 8a.

[0034] Fig. 4shows the battery cell 1 according to the preferred third embodiment of the invention in the interrupted state U, schematically in a sectional view. The battery cell 1 according to the preferred third embodiment differs from the battery cell 1 according to the preferred second embodiment in the design of the detachment device 9. The detachment device 9 has a holding device 14 with an adhesive point 15. The conductor 8 is held on the first wall section 4a via the adhesive point 15 and thus moves with it.

[0035] In Fig. 5The battery system 2 according to the preferred embodiment of the invention is depicted schematically in a sectional view. The battery system 2 comprises a plurality of battery cells 1 according to the invention, which are combined into several cell stacks 20 and arranged within a system housing 17 of the battery system 2. The cell stacks 20 are each clamped in the system housing 17 via a clamping device 21.

[0036] Fig. 6 shows the preferred embodiment of the motor vehicle 3 according to the invention schematically in a side view. The motor vehicle 3 has an electric drive system 18 with an electric motor 19 for driving the motor vehicle 3, power electronics 22 for controlling the electric motor 19, and a battery system 2 according to the invention for providing electrical energy to operate the power electronics 22 and the electric motor 19. List of reference symbols

[0037] 1Battery cell 2Battery system 3Motor vehicle 4Cell wall 4aFirst wall section 4bSecond wall section 5Cell interior 6Active material 7Electrode 8Arrester 8aBase section 8bJoint section 9Release device 10Gap 11Pressure device 12Compression spring 13Compression foam 14Holding device 15Adhesive point 16Kink 17System housing 18Drive system 19Electric motor 20Cell stack 21Bracing device 22Power electronics AInitial state UInterruption state

Claims

1. Battery cell (1) for a battery system (2) for a motor vehicle (3), comprising a flexible cell wall (4), a cell interior (5) formed by the cell wall (4), active material (6) arranged in the cell interior (5) for storing and releasing electrical energy, an electrode (7) which is arranged in the cell interior (5) and is electrically coupled to the active material (6), and an arrester (8) which protrudes from the cell interior (5) and is electrically coupled to the electrode (7) in an initial state (A), wherein in the initial state (A), a pressure difference between an internal cell pressure in the cell interior (5) and an external cell pressure outside the cell interior (5) is smaller than a predetermined pressure threshold value, wherein the electrode (7) and the arrester (8) are pressed against one another in the initial state (A) to produce the electrical coupling between a first wall portion (4a) and a second wall portion (4b) of the cell wall (4), wherein the battery cell (1) has a separation device (9) for releasing the electrical coupling in an interruption state (U), wherein the pressure difference in the interruption state (U) corresponds to the pressure threshold value, wherein the separation device (9) is designed to follow with the arrester (8) or the electrode (7), from the initial state (A) to the interruption state (U), a movement of the first wall portion (4a) away from the second wall portion (4b) such that in the interruption state (U), a gap (10) is formed between the arrester (8) and the electrode (7), wherein the separation device (9) has a pressure device (11), characterized in that the pressure device (11) in the initial state (A) has a preload maintained by the pressure difference and is designed to press the arrester (8) away from the electrode (7) or to press the electrode (7) away from the arrester (8) in the direction of the first wall portion (4a).

2. Battery cell (1) according to claim 1, characterized in that the pressure device (11) has a compression spring (12) and / or a pressure cylinder and / or a pressure foam (13) or in that the pressure device (11) is provided by a residual stress of the arrester (8) or the electrode (7).

3. Battery cell (1) according to either of the preceding claims, characterized in that the separation device (9) has a holding device (14), wherein the holding device (14) is designed to hold the arrester (8) or the electrode (7) on the first wall portion (4a).

4. Battery cell (1) according to claim 3, characterized in that the holding device (14) has an adhesive point (15) and / or soldering point and / or welding point and / or crimping point.

5. Battery cell (1) according to any of the preceding claims, characterized in that the electrode (7) and the arrester (8), in the initial state (A), are pressed against each other by the pressure difference between the internal cell pressure and the external cell pressure that is present between the first wall portion (4a) and the second wall portion (4b).

6. Battery cell (1) according to any of the preceding claims, characterized in that the electrode (7) or the arrester (8) has a hinge portion (8b) between two main portions (8a) to improve a common movement with the first wall portion (4a).

7. Battery cell (1) according to claim 6, characterized in that the hinge portion (8b) has a kink (16) and / or a reduction in cross-section and / or an increased ductility compared to the adjacent main portions (8a).

8. Battery system (2) for a motor vehicle (3), comprising a system housing (17), characterized in that a plurality of battery cells (1) according to any of the preceding claims are arranged in the system housing (17).

9. Motor vehicle (3) comprising an electric drive system (18) having an electric motor (19) for driving the motor vehicle (3), characterized in that the drive system (18) has a battery system (2) according to claim 8 for supplying the electric motor (19) with electrical energy.