Arrangement for creating an electrical short circuit between opposite electrodes of a battery cell

Abstract

Arrangement (10, 27) for producing an electrical short circuit between oppositely polarized electrodes (3, 4) of a battery cell (1), in particular a lithium-ion battery cell, characterized by - at least one short-circuit unit (11) that can be arranged in a cell housing (2) of the battery cell (1), comprising at least one cylinder (16), at least one cylinder base (17) closing the cylinder (16) at one end, and at least one piston (18) movably arranged in the cylinder (16) and having at least one electrically conductive piston section, wherein the piston section is electrically connectable to a first electrode (3, 4) of the battery cell (1), and - at least one restoring means (19) for holding the piston (18) in a separation position spaced apart from the cylinder base (17) at normal pressure prevailing in the cell housing (2) and for exerting a restoring force (F) R) on the piston (18) in the direction of the separation position when the piston (18) is moved towards the cylinder base (17), - wherein at least one electrically conductive cylinder section is arranged on the cylinder (16) and / or on the cylinder base (17), wherein the cylinder section can be electrically connected to a second electrode (3, 4) of the battery cell (1) which is designed with opposite polarity to the first electrode (3, 4), - wherein the piston section and the cylinder section are not electrically connected to each other when the piston (18) is in its separating position, and - wherein the piston (18) can be moved from its separating position towards the cylinder base (17) into a contact position in which the piston section is electrically connected to the cylinder section when the pressure prevailing in the cell housing (2) exceeds a predefinable pressure limit.

Description

State of the art

[0001] Battery cells, particularly (secondary) lithium-ion battery cells, are used in a wide variety of applications today. One well-known example is the mobile use of battery cells in electrically powered vehicles, particularly electric vehicles, plug-in hybrid vehicles, and hybrid vehicles, to supply electrical energy to the vehicles' electric drive systems using the battery cells or batteries formed from them. Furthermore, mobile applications of battery cells are known, among other things, in the consumer sector, for example in laptops, mobile phones, and similar devices. Battery cells are also used in stationary applications, for example in wind turbines. For these applications, which are not exhaustive, very high demands are placed on battery cells in terms of their reliability, performance, and service life.

[0002] A battery cell has a cell housing in which a galvanic cell is arranged, which comprises current-generating electrochemical elements. The cell housing of a battery cell typically comprises a housing body (so-called "can") that accommodates the galvanic cell and a cover (so-called "cap plate") that seals the housing body. The cover is connected to the housing body in a fluid-tight manner.

[0003] Battery cells must be protected against overcharging due to their chemical function, since overcharging of a battery cell is accompanied by overheating of the battery cell, which in turn is associated with gas development within a cell casing of a battery cell, whereby the pressure prevailing in the cell casing of the battery cell can rise to critical levels.

[0004] A battery cell typically has an electronic control unit that includes a protective function to protect the battery cell against overcharging. To ensure adequate protection against overcharging of a battery cell in the event of a malfunction of this electronic control unit, an additive can be added to the electrolyte present in the cell casing of a lithium-ion battery cell, for example. This additive hardens when excessive electrical voltage occurs in the battery cell, thereby blocking the lithium-ion current. As a result, a suitably designed battery cell remains charged but cannot be charged any further. However, conventional electrolyte additives are quite unreliable for relatively large battery cells.Alternatively, a battery cell can be equipped with a means for forming an electrical short circuit according to the published patent application DE 10 2011 002 659 A1, with which, in the event of an overcharge of the battery cell, an electrical short circuit can be deliberately created between the electrodes of the battery cell, as a result of which the battery cell is discharged and can no longer be charged.

[0005] From the document US 2010 / 0 123 358 A1, an electrical bypass for a battery is known, by means of which a defective battery module can be checked so that the battery can continue to be used under slightly reduced conditions. Disclosure of the invention

[0006] The invention relates to an arrangement for producing an electrical short circuit between oppositely polarized electrodes of a battery cell, in particular a lithium-ion battery cell, characterized by - at least one short-circuit unit which can be arranged in a cell housing of the battery cell and which comprises at least one cylinder, at least one cylinder base closing the cylinder at one end, and at least one piston which is movably arranged in the cylinder and has at least one electrically conductive piston section, wherein the piston section can be electrically conductively connected to a first electrode of the battery cell, and - at least one return means for holding the piston in a separation position spaced apart from the cylinder base when the normal pressure prevails in the cell housing and for exerting a return force on the piston in the direction of the separation position when the piston is displaced in the direction of the cylinder base, - wherein at least one electrically conductive cylinder section is arranged on the cylinder and / or on the cylinder base, wherein the cylinder section is electrically conductively connectable to a second electrode of the battery cell having an opposite polarity to the first electrode, - wherein the piston section and the cylinder section are not electrically connected to one another when the piston is in its separated position, and - wherein the piston can be displaced from its separated position in the direction of the cylinder base into a contact position in which the piston section is electrically conductively connected to the cylinder section when the pressure prevailing in the cell housing exceeds a predeterminable pressure limit value.

[0007] By means of the arrangement according to the invention, an electrical short circuit is created between opposing electrodes of a battery cell, in particular a lithium-ion battery cell, when the pressure prevailing in a cell housing of a battery cell equipped with the arrangement according to the invention exceeds a predeterminable pressure limit. The pressure prevailing in the cell housing acts on the side of the piston facing away from the cylinder base and generates a force that opposes the restoring force generated by the restoring means. If a battery cell has not been heated by overcharging, there is no increase in pressure within the cell housing of the battery cell, and a normal pressure typical for normal operation of the battery cell exists in the cell housing.As soon as the force exerted on the piston by the pressure within the cell housing exceeds the restoring force by a predeterminable amount, the piston begins to move from its separation position, in which the piston section is electrically separated from the cylinder section, toward the cylinder base into a contact position, in which the piston section is electrically connected to the cylinder section. As soon as an electrical short circuit is established between the oppositely polarized electrodes of a battery cell by means of the arrangement according to the invention, the battery cell is discharged, so that no further overcharging of the battery cell can occur and no further increase in pressure takes place in the cell housing of the battery cell.This can prevent a bursting membrane that may be present on the cell housing of a battery cell and is arranged at a blow-off opening of the cell housing from bursting, which would disadvantageously result in the release of chemically aggressive gases from the cell housing into the environment of the battery cell.

[0008] The short-circuit unit represents a simple, space-saving assembly that can be manufactured cost-effectively and installed in the battery cell housing during new battery cell production. Existing battery cells can also be easily retrofitted with the short-circuit unit according to the invention without requiring any structural modifications. Due to the space-saving design of the short-circuit unit according to the invention, it can be installed on a battery cell without limiting the design flexibility regarding the battery cell's structural design.

[0009] The piston can have two or more electrically conductive piston sections. The piston can also be completely electrically conductive. An electrically conductive piston section can be designed to protrude at least partially from the rest of the piston. The piston section can be a separately manufactured component connected to the rest of the piston.

[0010] Two or more electrically conductive cylinder sections can be arranged on the cylinder and / or the cylinder base. The cylinder base can also be completely electrically conductive. An electrically conductive cylinder section can be designed to protrude at least partially from the remaining cylinder or cylinder base. The cylinder section can be a separately manufactured component connected to the remaining cylinder or cylinder base.

[0011] The return means can be designed in any suitable manner to hold the piston in a separated position spaced from the cylinder base when the normal pressure prevails in the cell housing and to exert a restoring force on the piston in the direction of the separated position when the piston is displaced towards the cylinder base. Since the return means holds the piston in the separated position when the normal pressure prevails in the cell housing, an uncontrolled electrical short circuit can not occur between the oppositely polarized electrodes of a battery cell. The return means is preferably designed such that during normal operation of a battery cell and the associated pressure fluctuations within the cell housing of the battery cell, there is almost no or no displacement of the piston.

[0012] According to an advantageous embodiment, the return means comprises at least one mechanical return spring acting on the piston. This represents a structurally simple and cost-effective design of the arrangement for securely holding the piston in its released position and exerting a return force on the piston as it is displaced toward the cylinder base.

[0013] Advantageously, the return spring is designed as a tension spring that engages the side of the piston facing away from the cylinder base. One end of the tension spring can engage a bracket of the short-circuit unit, while the other end engages the piston. Alternatively, the return spring can be designed as a compression spring that rests on the piston at one end and the cylinder base at the other.

[0014] Preferably, the return spring is electrically conductive and electrically connected to the piston portion, wherein the piston portion can be electrically connected to the first electrode via the return spring. This allows two functions—namely, returning the piston and connecting the piston to an electrode of the battery cell—to be realized by a single component. This has a favorable effect on the design effort required to manufacture and install the arrangement according to the invention and, in particular, is accompanied by a space-saving design of the arrangement.

[0015] According to a further advantageous embodiment, a chamber is formed in the cylinder between the piston and the cylinder base, which chamber can be connected to the environment of the short-circuit unit in a unidirectional fluid-conducting manner via at least one outlet arranged on the piston, the cylinder, or the cylinder base in such a way that a fluid contained in the chamber can pass from the chamber into the environment of the short-circuit unit via the outlet, and no fluid from the environment of the short-circuit unit can pass into the chamber via the outlet. As a result, a gaseous or liquid fluid present in the chamber can be displaced from its separation position to its contact position and forced out of the chamber upon movement of the piston from its separation position to its contact position.To ensure the necessary pressure difference between the pressure in the chamber and the pressure in the cell housing surrounding the short-circuit unit, the chamber must be connected to the surroundings of the short-circuit unit via the outlet in a fluid-conducting, exclusively unidirectional manner. For this purpose, the outlet can be equipped with a check valve or a flap valve.

[0016] A further advantageous embodiment provides that the return means is formed by a fluid pressure prevailing in a pressure chamber arranged in the cylinder between the piston and the cylinder base, which pressure essentially corresponds to a normal pressure prevailing in the cell housing, wherein the pressure chamber is hermetically sealed from the environment of the short-circuit unit. Upon displacement of the piston from its separation position toward its contact position, a gaseous or liquid fluid present in the pressure chamber is displaced. A closed gas or gel cushion can also be arranged in the pressure chamber, which is displaced and / or destroyed upon such displacement of the piston.

[0017] According to a further advantageous embodiment, the separated position of the piston relative to the cylinder is secured by a locking element, which is designed such that it is destroyed to release the piston when the pressure prevailing in the cell housing exceeds the predeterminable pressure limit. The locking element can be designed, for example, as a thin plate made of aluminum or the like, which engages both the cylinder and the piston in such a way that it is destroyed when the predeterminable pressure limit is exceeded, thus releasing the piston.

[0018] According to a further advantageous embodiment, the release position of the piston relative to the cylinder is secured by means of a securing element, which is designed such that it releases the piston without destroying the securing element when the pressure prevailing in the cell housing exceeds the predeterminable pressure limit. In contrast to the last-mentioned embodiment, this prevents parts of a destroyed securing element from entering the interior of a battery cell and causing detrimental effects there. Furthermore, the securing element according to this embodiment can be reused. When the piston is released, only a plastic or elastic deformation of the securing element occurs.

[0019] The invention further relates to a battery cell, in particular a lithium-ion battery cell, comprising a cell housing containing a galvanic cell and at least two electrodes arranged in the cell housing with opposite polarity, characterized by an arrangement according to one of the aforementioned embodiments or any combination thereof. The advantages mentioned above with reference to the arrangement are correspondingly associated with this battery cell.

[0020] According to an advantageous embodiment, the arrangement has a single short-circuit unit, wherein the piston section is electrically conductively connected to the first electrode via an electrical line running in the cell housing and the cylinder section is electrically conductively connected to the second electrode via a further electrical line running in the cell housing. According to this embodiment, only one short-circuit unit needs to be installed in a battery cell, which contributes to a space-saving design of the arrangement. The embodiment has the further advantage that an electrical resistor can be arranged between the oppositely polarized electrodes so that in the event of an electrical short circuit created via the arrangement, the short-circuit current that occurs can be limited by the electrical resistor. The electrical line can be designed as a cable or busbar.

[0021] According to an alternative embodiment, the arrangement comprises two short-circuit units arranged in the cell housing, wherein at least one cover section of a cover of the cell housing is electrically conductive, wherein the two short-circuit units are electrically connected to one another via the cover section. Furthermore, the two short-circuit units are each connected to one of the oppositely polarized electrodes via electrical lines, wherein the electrical lines can be designed as cables or busbars. The cover of the cell housing can also be completely electrically conductive.

[0022] Advantageously, at least one short-circuit unit is attached to a side of a cell housing cover facing the interior of the cell housing or to a current collector electrically connected to the respective electrode. The selected mounting variant depends on the specific structural design of the battery cell. The current collectors each electrically connect an electrode of the battery cell to a connection terminal arranged on the cell housing, via which the battery cell can be electrically connected to other electrical components.

[0023] The invention is explained below by way of example with reference to the accompanying figures, using exemplary embodiments, wherein the features presented below can represent an aspect of the invention both individually and in various combinations. They show: Fig. 1: a schematic representation of an embodiment of a battery cell according to the invention, Fig. 2: a schematic representation of a further embodiment of a battery cell according to the invention, Fig. 3: a schematic representation of an embodiment of a short-circuit unit of an arrangement according to the invention, and Fig. 4: a schematic representation of a further embodiment of a short-circuit unit of an arrangement according to the invention.

[0024] Fig. 1 shows a schematic representation of an embodiment of a battery cell 1 according to the invention in the form of a lithium-ion battery cell. The battery cell 1 comprises a cell housing 2 containing a galvanic cell (not shown in detail) and at least two electrodes 3 and 4 arranged in the cell housing 2 and designed with opposite polarity. The cell housing 2 has a cover 5. Connection terminals 6 and 7 are arranged on the cell housing 2, which are each electrically connected to an electrode 3 or 4 via a current collector 8 or 9, respectively. The battery cell 1 further comprises an arrangement 10 for establishing an electrical short circuit between the opposite polarity electrodes 3 and 4, which arrangement has a single short-circuit unit 11, which according to the Fig. 3 or Fig. 4 and which is electrically connected to the electrodes 3 and 4 via electrical lines 12 and 13 running in the cell housing 2 and via the current collectors 8 and 9. The short-circuit unit 11 is fastened in a manner not shown in detail to a side of the cover 5 facing the interior 14 of the cell housing 2.

[0025] Fig. Figure 2 shows a schematic representation of a further embodiment of a battery cell 1 according to the invention in the form of a lithium-ion battery cell. In contrast to the Fig. The embodiment shown in Figure 1 has the Fig. The battery cell 1 shown in Figure 2, or its arrangement 27, has two short-circuit units 11 arranged in the cell housing 2. At least one cover section 15 of the cover 5 is electrically conductive, with the two short-circuit units 11 being electrically conductively connected to one another via the cover section 15. The short-circuit units 11 are attached to the current collectors 8 and 9 in a manner not shown in detail.

[0026] Fig. 3 shows a schematic representation of an embodiment of a short-circuit unit 11 of an arrangement 10 or 27 according to the invention for producing an electrical short circuit between the oppositely polarized electrodes 3 and 4 of a battery cell 1. The short-circuit unit 11 can be designed in accordance with the Fig. 1 or Fig. 2 in a cell housing 2 of a battery cell 1.

[0027] The short-circuit unit 11 comprises a cylinder 16, a cylinder base 17 closing the cylinder 16 at one end, and an electrically conductive piston 18 movably arranged in the cylinder 16.

[0028] The short-circuit unit 11 further comprises a return means 19 for holding the piston 18 at normal pressure prevailing in the cell housing 2 in the Fig. 3, arranged at a distance from the cylinder base 17 and for exerting a restoring force F Ron the piston 18 in the direction of the separated position when the piston 18 is displaced in the direction of the cylinder base 17. The return means 19 has a mechanical return spring 20 which acts on the piston 18 and is designed as a tension spring acting on the side 21 of the piston 18 facing away from the cylinder base 17. One end of the return spring 20 is fastened to a holder 22 which can be fixedly attached to the short-circuit unit 11. The return spring 20 is electrically conductive and is electrically conductively connected to the piston 18, wherein the piston 18 can be electrically conductively connected to an electrode 3 or 4 of a battery cell 1 via the return spring 20 and the electrical line 12.

[0029] The cylinder base 17 is designed to be electrically conductive, wherein the cylinder base 17 can be electrically conductively connected via an electrical line 13 to an electrode 3 or 4 of a battery cell 1, which is designed with the opposite polarity to the electrode 3 or 4 to which the piston 18 can be electrically conductively connected.

[0030] The piston 18 and the cylinder base 17 are not electrically connected to one another when the piston 18 is in its shown separated position. The piston 18 can be displaced from its shown separated position towards the cylinder base 17 into a contact position, in which the piston 18 is electrically connected to the cylinder base 17, when the pressure prevailing in the cell housing 2 exceeds a predeterminable pressure limit value, wherein the pressure represents a force F acting on the piston 18. D generated, which corresponds to the restoring force F R is opposite.

[0031] A chamber 23 is formed in the cylinder 16 between the piston 18 and the cylinder base 17, which chamber can be connected in a unidirectional fluid-conducting manner to the environment of the short-circuit unit 11 via an outlet 24 arranged on the cylinder base 17 such that a fluid contained in the chamber 23 can pass from the chamber 23 into the environment of the short-circuit unit 11 via the outlet 24, and no fluid from the environment of the short-circuit unit 11 can pass into the chamber 23 via the outlet 24. For this purpose, the outlet 24 has a check valve (not shown).

[0032] Fig. 4 shows a schematic representation of a further embodiment of a short-circuit unit 11 of an arrangement 10 or 27 according to the invention for producing an electrical short circuit between the oppositely polarized electrodes 3 and 4 of a battery cell 1. The short-circuit unit 11 can be designed in accordance with the Fig. 1 or Fig. 2 in a cell housing 2 of a battery cell 1.

[0033] In contrast to the Fig. 3, the return means 19 is formed by a fluid pressure prevailing in a pressure chamber 25 arranged in the cylinder 16 between the piston 18 and the cylinder base 17, which pressure essentially corresponds to a normal pressure prevailing in the cell housing 2, wherein the pressure chamber 25 is hermetically sealed from the environment of the short-circuit unit 11. The fluid pressure prevailing in the pressure chamber 25 exerts the return force F on the piston 18. R out of.

[0034] The short-circuit unit 11 further comprises a securing element 26 for securing the illustrated separated position of the piston 18 relative to the cylinder base 17. This securing element is designed such that it is destroyed to release the piston 18 if the pressure prevailing in the cell housing 2 exceeds the predeterminable pressure limit. The securing element 26 is designed as a thin plate, for example made of aluminum. However, the plate 26 can also be made of other materials, such as plastic or metal. Furthermore, in a specific embodiment, it can be designed such that it releases the movement of the piston 18 without causing damage when a specified pressure is exceeded.

Claims

[1] Arrangement (10, 27) for producing an electrical short circuit between oppositely polarized electrodes (3, 4) of a battery cell (1), in particular a lithium-ion battery cell, characterized by - at least one short-circuit unit (11) which can be arranged in a cell housing (2) of the battery cell (1), which comprises at least one cylinder (16), at least one cylinder base (17) closing the cylinder (16) at one end, and at least one piston (18) which is movably arranged in the cylinder (16) and has at least one electrically conductive piston section, wherein the piston section can be electrically conductively connected to a first electrode (3, 4) of the battery cell (1), and - at least one restoring means (19) for holding the piston (18) in a separation position spaced apart from the cylinder base (17) at normal pressure prevailing in the cell housing (2) and for exerting a restoring force (F R) on the piston (18) in the direction of the separation position when the piston (18) is displaced in the direction of the cylinder base (17), - wherein at least one electrically conductive cylinder section is arranged on the cylinder (16) and / or on the cylinder base (17), wherein the cylinder section can be electrically connected to a second electrode (3, 4) of the battery cell (1) which is designed with the opposite polarity to the first electrode (3, 4), - wherein the piston section and the cylinder section are not electrically connected to one another when the piston (18) is in its separated position, and - wherein the piston (18) can be displaced from its separated position in the direction of the cylinder base (17) into a contact position in which the piston section is electrically conductively connected to the cylinder section, when the pressure prevailing in the cell housing (2) exceeds a predeterminable pressure limit value. [2] Arrangement (10, 27) according to claim 1, characterized by that the return means (19) has at least one mechanical return spring (20) acting on the piston (18). [3] Arrangement (10, 27) according to claim 2, characterized by that the return spring (20) is designed as a tension spring acting on the side of the piston (18) facing away from the cylinder base (17). [4] Arrangement (10, 27) according to claim 3, characterized by that the return spring (20) is designed to be electrically conductive and is electrically conductively connected to the piston section, wherein the piston section can be electrically conductively connected to the first electrode (3, 4) via the return spring (20). [5] Arrangement (10, 27) according to one of claims 1 to 4, characterized byin that a chamber (23) is formed in the cylinder (16) between the piston (18) and the cylinder base (17), which chamber can be connected in a unidirectional fluid-conducting manner to the environment of the short-circuit unit (11) via at least one outlet (24) arranged on the piston (18), the cylinder (16) or the cylinder base (17) in such a way that a fluid contained in the chamber (23) can pass from the chamber (23) into the environment of the short-circuit unit (11) via the outlet (24) and no fluid from the environment of the short-circuit unit (11) can pass into the chamber (23) via the outlet (24). [6] Arrangement (10, 27) according to claim 1, characterized byin that the return means (19) is formed by a fluid pressure prevailing in a pressure chamber (25) arranged in the cylinder (16) between the piston (18) and the cylinder base (17), which pressure essentially corresponds to a normal pressure prevailing in the cell housing (2), wherein the pressure chamber (25) is hermetically sealed against the environment of the short-circuit unit (11). [7] Arrangement (10, 27) according to one of claims 1 to 6, characterized by that the separated position of the piston (18) relative to the cylinder (16) is secured by means of a securing element (26) which is designed such that it is destroyed to release the piston (18) when the pressure prevailing in the cell housing (2) exceeds the predeterminable pressure limit value. [8] Arrangement (10, 27) according to one of claims 1 to 6, characterized bythat the separated position of the piston (18) relative to the cylinder (16) is secured by means of a securing element (26) which is designed such that it releases the piston (18) without destroying the securing element (26) when the pressure prevailing in the cell housing (2) exceeds the predeterminable pressure limit value. [9] Battery cell (1), in particular a lithium-ion battery cell, comprising a cell housing (2) containing a galvanic cell and at least two electrodes (3, 4) arranged in the cell housing (2) and designed with opposite polarity, characterized by an arrangement (10, 27) according to one of claims 1 to 8. [10] Battery cell (1) according to claim 9, characterized byin that the arrangement (10) has a single short-circuit unit (11), wherein the piston section is electrically conductively connected to the first electrode (3, 4) via an electrical line (12, 13) running in the cell housing (2) and the cylinder section is electrically conductively connected to the second electrode (3, 4) via a further electrical line (12, 13) running in the cell housing (2). [11] Battery cell (1) according to claim 9, characterized by that the arrangement (27) has two short-circuit units (11) arranged in the cell housing (2), wherein at least one cover section of a cover (5) of the cell housing (2) is designed to be electrically conductive, wherein the two short-circuit units (11) are electrically conductively connected to one another via the cover section. [12] Battery cell (1) according to one of claims 9 to 11, characterized bythat at least one short-circuit unit (11) is fastened to a side of a cover (5) of the cell housing (2) facing the interior (14) of the cell housing (2) or to a current collector (8, 9) electrically conductively connected to the respective electrode (3, 4).

Images