Battery fire prevention system and method for preventing a battery fire resulting from thermal runaway of a battery cell

Description

[0001] The invention relates to a battery fire prevention system for a motor vehicle battery comprising a plurality of battery cells for preventing a battery fire resulting from thermal runaway of one of the battery cells. Furthermore, the invention also relates to a method for preventing a battery fire resulting from thermal runaway of a battery cell.

[0002] Batteries for electric or hybrid vehicles are usually designed as high-voltage batteries and contain numerous battery cells. Under certain circumstances, for example in the event of an accident, a defect, or a short circuit in a battery cell, a thermal runaway of such a battery cell can occur. This causes the battery cell to heat up considerably and ultimately leads to gas escaping from the battery cell, usually through a releasable gas outlet provided in the cell. This escaping gas stream also contains particles, some of which are electrically conductive. Without further countermeasures, these particles can spread within the battery casing and lead to a reduction in air and creepage distances, particularly in the area of ​​the cell terminals and cell connectors, which promotes arcing, further short circuits, and a battery fire.The heating of the continuous cell itself, as well as the hot escaping gas, also causes other cells, especially those in the immediate vicinity of the continuous battery cell, to become extremely hot and, as a result, can also thermally break down. Without countermeasures, this ultimately leads to thermal propagation throughout all cells in the battery, ultimately resulting in a high-voltage battery fire.

[0003] DE 10 2018 220 992 A1 describes a safety device for an electrochemical energy storage device that has a burst valve and a cooling device. Hot gases escaping through the burst valve are intended to be quickly cooled. For cooling, a cooling plate can be provided, which is also designed as the cooling plate of the battery pack, so that the escaping gas can be guided along the underbody of the vehicle or along the cooling plate of the battery pack.

[0004] DE 10 2021 105848 A1 describes an energy storage system having a battery module with a plurality of secondary battery cells and a housing accommodating a module stack, wherein the housing comprises a first cover arranged to face at least one side surface of the module stack and a second cover facing at least one further side surface of the module stack, wherein a flame channel is formed between the first cover and the module stack and a cooling channel is formed between the second cover and the module stack.

[0005] While targeted gas venting or cooling can reduce the risk of self-ignition of the escaping gas upon its final exit from the vehicle's exhaust port, this does not prevent thermal runaway of further battery cells from the one that initially experienced thermal runaway. In the event of thermal propagation across all cells, so much gas ultimately escapes from the battery that ignition of the gas after it exits a final exit port can no longer be avoided. Especially when numerous battery cells experience thermal runaway, the resulting enormous amounts of hot gas can no longer be cooled efficiently. There is also a risk of the vent becoming blocked by the numerous deposited particles.As thermal propagation progresses, the cells within the battery casing heat up even more, particularly to such an extent that a battery fire in the vehicle can no longer be prevented. A further problem in the event of a thermal runaway is that upon detection of such a fault, the high-voltage electrical system, which is supplied with energy by the battery during normal operation, is usually deactivated, and the battery is immediately disconnected from the rest of the high-voltage electrical system. This also means that active cooling, in which the coolant is actively cooled by a cooling circuit, is no longer available for the battery. Therefore, state-of-the-art technology attempts to prevent thermal propagation or extinguish a battery fire using special extinguishing devices.

[0006] For example, DE 10 2016 200 368 A1 describes a battery system with a battery module and a coolant circulation system with at least one coolant container and a coolant line that is partially routed through the battery module, wherein the coolant line has an emergency opening in the battery module that is closed by an actuating element that is designed as a pressure-sensitive actuating element that opens at a pressure greater than a threshold value and releases the emergency opening. Furthermore, the coolant container has a connection for an extinguishing agent hose or an interface for attaching a connection for an extinguishing agent hose. If an extinguishing agent hose is connected to the connection and extinguishing agent is added, this leads to increased pressure in the coolant circulation system, whereby the emergency opening in the battery module is opened and the coolant can flow into the battery module.

[0007] In most cases, suitable extinguishing measures and extinguishing systems can only fight the fire that has already started, since these measures require the connection of a fire hose, which can only be made available after the fire brigade has arrived.

[0008] The object of the present invention is therefore to provide a fire prevention system and a method which make it possible to prevent a fire resulting from a thermal runaway of a battery cell of a battery, in particular inside the battery as well as outside the battery.

[0009] This object is achieved by a battery fire prevention system and a method having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figure.

[0010] A battery fire prevention system according to the invention for a motor vehicle battery comprising a plurality of battery cells for preventing a battery fire resulting from a thermal runaway of a first battery cell of the battery cells of the battery comprises a cell degassing channel connectable to the battery cells of the battery, into which a gas escaping from a respective one of the battery cells can be introduced and discharged to at least one outlet opening of the cell degassing channel, a gas flow influencing structure as part of the cell degassing channel, which is designed to influence the course of the gas flow flowing through the cell degassing channel, which gas flow is formed by the gas escaping from the first battery cell, and a cooling device for cooling the thermally runaway first battery cell, wherein the cooling device is configured such that a coolant flows through it,at the latest when the first battery cell thermally breaks down.

[0011] The invention is based on the finding that there are several core elements, in particular three core elements, which only become effective in the overall assembly to actually prevent a battery fire, and in particular also a fire outside the battery, and to stop thermal propagation. These core elements include a controlled gas flow, which can be achieved by the cell degassing channel connectable to the battery cells; suitable gas treatment during gas removal, which can be achieved by the gas flow control structure; and defined heat conduction paths that prevent rapid heat spread from one battery cell to another. This can be achieved by the cooling device for cooling at least the thermally continuous cell.Controlled gas removal makes it possible to prevent the gas, including the electrically conductive particles it contains, from spreading uncontrollably within the battery casing and triggering further short circuits in the area of ​​the cell connectors and cell terminals. The gas flow control structure advantageously makes it possible to cool the gas flow during its outflow by influencing its course and, in particular, to filter out particles, as will be explained in more detail later. This prevents self-ignition of this gas flow upon exiting the final outlet opening. This, in turn, influences the likelihood of a fire starting within the battery in two ways. Firstly, a cooled gas flow no longer transfers as much heat back to the battery cells, and secondly, heat buildup, which can occur if the gas escaping from the final outlet opening catches fire, is prevented.Such heat buildup can, in turn, affect heat development in the battery system within the motor vehicle, which can thus advantageously be prevented. These measures are particularly advantageous in combination with the cooling device for cooling the thermally continuous, first battery cell, since only this, in combination with the described gas removal, can ultimately prevent the spread of thermal propagation. By appropriately removing the gas and also cooling the thermally continuous battery cell, and in particular by removing the heat from the thermally continuous battery cell and the surrounding hotspot area, it is possible to prevent neighboring cells or other cells of the battery from heating up to such an extent that they also experience thermal runaway.This in turn affects the efficiency of gas removal because, if only a single cell thermally leaks, only its gas needs to be appropriately treated, e.g. cooled, filtered and removed, in order to prevent spontaneous combustion of this gas when it escapes from the final outlet opening. The effects and measures provided for gas treatment by the gas flow influencing structure are therefore all the more effective if they only act on a small amount of gas. Ultimately, therefore, fire formation after gas leakage can only be effectively prevented if a cooling device is also provided to cool the first thermally leaking battery cell. Conversely, such a cooling device can only work efficiently if, for example, only a few cells, for example only the first thermally leaking battery cell, need to be cooled.Furthermore, even if the first thermally continuous battery cell is cooled, thermal propagation could not be prevented if the gas stream escaping from it were not properly vented. Without proper gas venting, further short circuits would occur due to the particles contained in the gas, which would lead to thermal runaway of additional battery cells despite cooling of the thermally continuous battery cell. The cooling effect would then be distributed across multiple cells and would therefore be significantly less efficient per cell. Therefore, only the synergistic interaction of these components can stop thermal propagation originating from a thermally continuous cell and prevent a battery fire involving all battery cells.

[0012] In the context of the present invention, a system is to be understood in particular as an arrangement or device or piece of equipment. Since, strictly speaking, several individual devices or components interact to prevent fire, this is referred to herein as a system. The battery can, for example, be a high-voltage battery for a motor vehicle, in particular an electric or hybrid vehicle. The battery cells comprised by the battery can optionally also be combined to form battery modules. Thus, a battery can have several battery modules, each with several battery cells. The battery can, for example, be provided for arrangement in an underbody area of ​​the motor vehicle, for example approximately in the area between the front and rear axles of the motor vehicle. The battery cells can, for example, be designed as lithium-ion cells.The cell degassing channel can generally be defined as the structural spatial boundary of a flow channel. The cell degassing channel can, for example, have a channel wall that separates an interior of the cell degassing channel from its surroundings. The fact that the cell degassing channel can be connected to the battery cells of the battery should be understood to mean that the cell degassing channel can be arranged on the battery cells or coupled to them in such a way that the gas escaping from a respective one of these battery cells can be introduced into the interior of the cell degassing channel. The coupling is such that preferably the majority of the gas escaping from a respective battery cell can be introduced into the cell degassing channel. Preferably, all or almost all of the gas flowing out of the battery cell is introduced into the interior of the cell degassing channel.The cell terminals of the battery cells are located in the vicinity of the cell degassing duct. This ensures efficient separation of the escaping gas from these cell terminals. The battery cells can, for example, be arranged in a battery housing. The cell degassing duct can run partially within this battery housing and lead out of it, in particular to a final outlet opening from the vehicle. This can therefore be provided through the outlet opening of the cell degassing duct. Alternatively, another line can be connected to the outlet opening of the cell degassing duct up to the final outlet opening. The gas flow influencing structure is designed to influence the course of the gas flow. This can include redirecting the gas flow in its flow direction or splitting the gas flow into several sub-flows.Both the deflection and the segmentation can achieve a cooling and filtering effect. Therefore, the gas flow control structure is preferably designed to cool the gas flow flowing through the cell degassing channel and / or to filter the particles contained in the gas flow.

[0013] The cooling device is designed to cool at least the thermally continuous battery cell, at the latest when the first battery cell thermally passes, by having a coolant flow through the cooling device. The cooling device can be assigned not only to the individual, first battery cell, but can also be a common cooling device for multiple battery cells. In other words, multiple battery cells or even all battery cells of the battery can be thermally connected to this cooling device, for example, arranged directly on this cooling device or mechanically connected to it via a thermally conductive compound or a thermally conductive element. The cooling device accordingly comprises cooling channels through which the coolant can flow.Thus, the cooling device is not merely designed as a passive cooling device, but advantageously enables convection of a coolant, which is significantly more efficient in terms of heat dissipation. To ensure that coolant flows through the cooling device, a coolant pump is provided that pumps the coolant through a cooling circuit to which the cooling device is connected, for example, via a suitable valve device and controlling such a valve device. The coolant itself does not necessarily have to be cooled.This is in turn based on the realization that, although in the event of a thermal runaway of a cell, active cooling involving a refrigeration circuit and an electric air conditioning compressor is no longer possible, due to the shutdown of the high-voltage system and the associated shutdown of such an air conditioning compressor or other components, the coolant pump in the cooling circuit, which can be supplied from the low-voltage network, can still continue to operate or can be put into the active state.Although the coolant circulating in the cooling circuit to which the cooling device is connected can then no longer be actively cooled, the operation of the coolant pump can ensure that the heat locally dissipated by the thermally continuous battery cell to the cooling device can be transported away from this hotspot area and absorbed by other components of the cooling system or the vehicle, for example, by the coolant itself and other components coupled to the cooling circuit. This can significantly reduce the amount of heat transferred from the thermally continuous cell to neighboring cells, particularly via the cooling device.By activating the flow of coolant through the cooling device, at the latest when the first battery cell thermally breaks down, the invention can circulate the cooling medium, i.e. the coolant, in order to specifically transport and distribute the heat from this hotspot area. The thermal capacity of the cooling system as a whole can thus be used to absorb and dissipate the heat, thereby preventing thermal propagation. According to the invention, the cooling device can thus be operated in an at least semi-active state, in which the coolant is circulated, but the coolant does not necessarily have to be actively cooled. Optionally, however, it is conceivable to additionally activate a fan, for example a radiator fan, in the area of ​​a heat exchanger in order to achieve a certain cooling effect for cooling the heated coolant.Water or a water-glycol mixture, for example, are possible coolants. However, other liquids are also conceivable, as is, in principle, a gaseous coolant. Several options are possible for activating the cooling device accordingly, at the latest when the first battery cell experiences thermal runaway. For example, a detection device can be provided that detects such thermal runaway or the onset of thermal runaway, for example, based on the temperature of the battery cell, on recorded electrical variables of the battery cell, such as voltage or current, or on the pressure in the battery or the battery module with the first battery cell, a gas composition, or similar.It is particularly advantageous if the cooling device activates the cooling function, should this not already be active when the onset of thermal runaway of the first battery cell is detected, i.e., for example, before this first battery cell begins to outgas. This can be easily determined, for example, based on the temperature of the battery cell. This allows for timely activation of the cooling device, or at least a coolant pump, to allow the coolant to flow through the cooling device.

[0014] In a further advantageous embodiment of the invention, the gas flow control structure is designed to filter particles entrained in the gas flow and / or prevent them from reaching the outlet opening. Such a filtering effect can be achieved in a variety of ways. Filtering such particles has the significant advantage of significantly reducing the likelihood of self-ignition of the gas upon exiting the final outlet opening. These particles represent ignition sources, so they should be prevented from exiting the final outlet opening if possible. For particle filtering, appropriate filters can be integrated, for example, into the gas discharge path provided by the cell degassing channel.For example, it is also conceivable to achieve such particle separation and filtration by deflecting the gas discharge path, in particular by deflecting it multiple times, for example, in a zigzag or serpentine pattern. This can be achieved, for example, by designing the gas discharge path itself to be correspondingly winding or curved in its direction of extension. However, it is preferred if corresponding deflection structures are integrated into the interior of the gas discharge channel. For example, baffles can be integrated into these to effect such gas flow deflection.For this purpose, for example, a chamber of the gas discharge channel can contain several parallel and zigzag-shaped or wave-shaped metal sheets, which separate the gas discharge path into several, in particular numerous, parallel partial paths, which vary alternately, in particular in the main direction, with respect to at least one direction perpendicular to the main direction, for example periodically or wave-shaped or zigzag-shaped. It is also conceivable to arrange several perforated metal sheets one behind the other in the main direction, with each perforated metal sheet having numerous small holes. The holes can be reduced in diameter from perforated metal sheet to perforated metal sheet in the main direction. This leads to gradual particle separation.At the same time, these measures not only lead to particle separation, but also to the gas flow being slowed down, which also cools down and, for example, also releases energy to the structures described.

[0015] Accordingly, a further highly advantageous embodiment of the invention is provided if the gas flow influencing structure is designed to reduce the flow velocity of the gas flow, in particular by redirecting the flow direction of the gas flow in the cell degassing channel. This can also be achieved, for example, by the particle filtration measures already described above. For example, the parallel, serpentine or wavy metal sheets are also suitable for achieving such a redirection of the flow direction, in multiple successions, whereby not only particle separation but also correspondingly cooling of the gas flow can be achieved.Such a deflection of the flow direction can also be achieved using the described perforated plates, particularly if the perforated plates are aligned such that the holes are not aligned with each other when viewed in the main flow direction, but are at least slightly or completely offset from each other. A deflection of the gas flow can also be achieved by labyrinthine structures within the cell degassing channel. The described variants can also be combined with each other, for example, by forming further sub-channels within the cell degassing channel, which, for example, have partially or partially gas-permeable channel walls.These then fulfil a similar effect to the perforated plates and enable, for example, the most homogeneous distribution possible of a gas flowing into a chamber over a maximum volume provided by the chamber of the cell degassing channel, as will be explained in more detail later.

[0016] In a further advantageous embodiment of the invention, the cell degassing channel has a wall that separates the interior of the cell degassing channel from the surroundings, wherein the gas flow influencing structure is arranged in the interior of the cell degassing channel. A gas flow influencing structure arranged in the interior of the cell degassing channel allows for significantly more efficient particle separation and gas flow cooling than, for example, if gas deflection were to be achieved through the geometric design and guidance of the cell degassing channel itself. Such gas flow influencing structures integrated into the interior of the cell degassing channel allow for an increase in the collision surface with which the gas collides when flowing through the cell degassing channel, which allows for more efficient cooling and particle separation.

[0017] It is also very advantageous if the cell degassing channel comprises, for example, a gas discharge chamber, which can also be referred to simply as a chamber, and in which a gas distribution structure is arranged as a gas flow influencing structure, which distributes the gas entering the chamber through at least one inlet opening in the chamber within the interior of the chamber before it leaves the chamber again through at least one outlet opening. Such a chamber can, for example, be provided as a space directly below and / or above the battery, for example between a battery base and an underrun protection device of the motor vehicle. This chamber thus extends, for example, in length and width over a large part of the battery, in particular over the entire battery. This makes it possible to provide very large dimensions for such a chamber, at least in two dimensions.The gas escaping from a cell can, for example, be introduced directly into this chamber, either upwards or downwards. A separate inlet opening can be provided in the chamber for each battery cell or battery module. In other words, the chamber can also comprise multiple inlet openings rather than just a single one.

[0018] The gas discharge chamber is configured, for example, such that a gas escaping from the at least one first battery cell, which is introduced into the gas discharge chamber through the at least one inlet opening, can be conducted through the gas discharge chamber to the at least one outlet opening and can be discharged from the at least one outlet opening. The gas discharge chamber has a gas distribution structure arranged in the interior of the gas discharge chamber, which is designed to distribute a gas introduced into the gas discharge chamber via the at least one first inlet opening in the interior of the gas discharge chamber before exiting from the at least one outlet opening.

[0019] According to a further advantageous embodiment of the invention, the gas distribution structure has at least one gas discharge channel arranged in a first region of the interior space, which has at least one partially gas-permeable channel wall which at least partially separates the first region from the second region of the interior space, wherein the at least one first inlet opening opens into the second region of the interior space and wherein the at least one outlet opening opens into an interior of the gas discharge chamber in the first region, wherein the at least one channel wall is designed such that a gas permeability of the channel wall varies depending on a distance from the at least one outlet opening of the chamber, for example increases with increasing distance.

[0020] In a further advantageous embodiment of the invention, the gas distribution structure has a plurality of gas discharge channels comprising the at least one gas discharge channel, wherein the gas discharge channels are arranged at a distance from one another, wherein an outlet opening of a plurality of outlet openings of the gas discharge chamber opens into each gas discharge channel, and wherein a respective gas discharge channel has two opposite gas-permeable channel walls.

[0021] It is also conceivable that the described gas flow control structures are also designed to allow a coolant to flow through them, and that such a coolant flows through them, at least at the latest when gas escapes from the first battery cell. This can provide additional gas cooling.

[0022] Furthermore, the invention also relates to a battery arrangement with a battery fire prevention system according to the invention or one of its embodiments.

[0023] It is preferred that the battery arrangement comprises the battery with the plurality of battery cells. Furthermore, each of the battery cells can have a releasable vent opening coupled to the cell vent channel.

[0024] According to an advantageous embodiment of the invention, the battery arrangement thus comprises the battery with the plurality of battery cells, wherein each of the battery cells has a releasable vent opening which is sealed to an associated, at least releasable inlet opening of the cell degassing channel by means of a seal which is designed to at least partially prevent gas escaping from the vent opening from penetrating into the environment of the cell degassing channel. Such a sealed coupling between the battery cell and the cell degassing channel can advantageously minimize the risk of gas penetrating into the environment through the space between the battery cell and the cell degassing channel. The cell poles of the battery cells are located in the environment. This allows the gas to be kept away from these cell poles and the cell connectors connected to them in a particularly efficient manner.The cell degassing channel can, for example, have, as part of its channel wall, a channel wall facing the battery cell arrangement, in which releasable channel openings are provided, which are coupled to the associated degassing openings of the battery cells or are connected to them via the seal. These at least releasable openings in the channel wall can be provided as permanent openings or as openings that are only opened when degassing occurs, and which can also be designed, for example, as bursting membranes. The seals can be designed, for example, as high-temperature seals. However, the sealing connection can also be designed as a metallic collar or ring or similar.

[0025] In a further very advantageous embodiment of the invention, the cooling device is connected to at least one side of each of the battery cells and / or arranged via electrical insulation on cell connectors by means of which the battery cells are electrically connected. The battery cells can be arranged in a specific arrangement relative to one another. If the battery cells are provided in the form of prismatic battery cells, for example, they can be arranged in the form of a cell stack with several battery cells arranged next to one another in the stacking direction.If the cells are designed as round cells, for example, they can be arranged on a carrier which also serves as the cooling device, in particular with one of their end faces facing the carrier, wherein the battery cells can also be arranged in a matrix-like arrangement on the carrier, or else with rows offset from one another, so that each round cell is surrounded by six further round cells as nearest neighbors, provided it is not an edge cell. The cells can, for example, have a first side, which in the case of round cells can represent an end face on which the cell poles or at least one of the cell poles is arranged. The first side of the battery cell therefore refers to a side on which at least one cell pole of the battery cell is arranged. The cooling device is therefore preferably connected to a side of the battery cell which is different from the first side.Additionally or alternatively, the cooling device can also be connected via electrical insulation to the cell terminals themselves or to the cell connectors that electrically contact the cell terminals. The cooling device can therefore also have multiple cooling units, for example, one connected to a side of the battery cells different from the first, and one that cools the cell connectors or cell terminals. The cells can also be configured as pouch cells, with the cooling system connected to a suitable side of these pouch cells. This allows for numerous different configurations that can be used to cool the battery cells.

[0026] It is also particularly advantageous if a thermal insulation element is arranged between each two adjacent battery cells of the plurality of battery cells. Such a thermal insulation element can be provided, for example, by a ceramic plate or mica plate, an insulating potting compound, or the like. The thermal insulation element is preferably also electrically insulating. This can slow the heat propagation from the affected thermally conductive first cell to other adjacent cells. At the same time, the additional cooling and the described gas removal can ensure that so little heat is transferred to adjacent cells that thermal runaway of these adjacent cells can be prevented.

[0027] Furthermore, the invention also relates to a motor vehicle with a battery arrangement according to the invention or one of its embodiments.

[0028] The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

[0029] Furthermore, the invention also relates to a method for preventing a battery fire resulting from a thermal runaway of a first battery cell of a plurality of battery cells of a battery, wherein a gas escaping from the first battery cell is introduced into a cell degassing channel connected to the battery cells of the battery and is discharged to at least one outlet opening of the cell degassing channel, the gas flow formed by the gas escaping from the first battery cell is influenced in its course by a gas flow influencing structure as part of the cell degassing channel, and the thermally runaway first battery cell is cooled by a cooling device through which a coolant flows.

[0030] The advantages mentioned for the battery fire prevention system according to the invention and its embodiments as well as for the battery arrangement according to the invention and its embodiments apply equally to the method according to the invention.

[0031] The invention also includes further developments of the method according to the invention that have features already described in connection with the further developments of the fire prevention system according to the invention and the battery arrangement according to the invention. For this reason, the corresponding further developments of the method according to the invention are not described again here.

[0032] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0033] Exemplary embodiments of the invention are described below. The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0034] The single figure shows a schematic representation of the main components of a fire prevention system 10 according to the invention. The fire prevention system 10 serves to prevent a fire in a battery 12 comprising a plurality of battery cells 14, which fire results from the thermal runaway of a first battery cell 14a of the plurality of battery cells 14. Such a battery 12 is illustrated, for example, in the middle illustration in the figure. A respective battery cell 14 can also have a releasable cell venting opening 16, which opens when there is excess pressure within the respective battery cell 14 in order to enable controlled outgassing of the respective battery cell 14, such as the thermally runaway battery cell 14a in this example. This battery 12 can be designed, for example, as a high-voltage battery for a motor vehicle, in particular an electric or hybrid vehicle. In the left illustration in the figureTwo such battery cells 14 are shown again by way of example. They are arranged on a carrier 18, which is also designed as a cooling base and through which a coolant 20 can flow. In order to allow the coolant 20 to flow through this carrier 18, which simultaneously represents a cooling device 18, a coolant pump 22 is used. The cooling circuit is designated 23 in the present case. The coolant 20 is circulated through this by pumps and the cooling device 18 is connected to this cooling circuit 23. All battery cells 14 can be arranged on a common carrier 18 designed as a cooling device 18, or separate cooling devices 18 can be provided for specific cell groups, each with a plurality of battery cells 14.

[0035] Basically, there are several thermal coupling paths 24a, 24b, 24c between two adjacent battery cells 14, as shown on the left in the figure. Firstly, the cell poles 14b of a respective battery cell 14 are coupled or electrically connected to those of an adjacent battery cell 14 via electrically conductive cell connectors 26. A first heat transfer path 24a is provided via this cell connector 26. If a thermal event in a battery cell 14 generates a large amount of heat in such a battery cell 14, this heat is transferred very quickly to the adjacent battery cell 14 via such a cell connector 26 without any further countermeasures.The cooling device 18, which can be provided, for example, in the form of a metallic plate provided with flow channels, also thermally couples adjacent cells 14 very well when the coolant 20 is not flowing through this plate 18. This also provides a highly thermally conductive heat transfer path 24c, at least in the inactive state of the cooling device 18. A further heat transfer path 24b is provided between the mutually facing cell surfaces between the battery cells 14.

[0036] If a thermal event occurs in a conventional battery cell without countermeasures, the battery cell will heat up significantly during thermal runaway, and gas will eventually escape from the battery cell. If the electrically conductive particles contained in this gas stream, in particular, reach the battery cell terminals, they can cause additional short circuits, which in turn can trigger thermal runaway in other battery cells. Heat can also be transferred to other cells via the described thermal pathways between the cells. If these cells also heat up significantly, they too will experience thermal runaway.

[0037] The invention and its embodiments now advantageously make it possible to prevent an entire battery fire resulting from thermal runaway of a battery cell 14a by means of the battery fire prevention system 10. As already mentioned, this comprises several main components. These are, firstly, the aforementioned cooling device 18, a cell degassing channel 28 connectable to the battery cells 14 for the targeted gas discharge of the gas flow 30 escaping from the thermally runaway cell 14a, and a gas flow influencing structure 32 as part of the cell degassing channel 28. The fire-preventing effect of the fire prevention system 10 can be achieved solely through the combination of these main components. The combination is illustrated in the figure by the addition symbols 32.This is based on the realization that efficient gas removal is only possible if not all battery cells 14 of the battery 12 experience thermal runaway. Targeted gas removal is, in turn, necessary to prevent further short circuits in other still intact cells 14 in order to avoid thermal propagation. It must also be possible to provide the best possible thermal decoupling between the cells 14, which is made possible by the cooling device 18. This, too, is only possible if not too many battery cells 14 experience thermal runaway, since otherwise efficient cooling can no longer be provided. Accordingly, suitable gas removal must be ensured, since otherwise the particles 34 contained in the gas stream 30 can cause short circuits and arcs within the battery 12, which promotes thermal propagation despite cooling.The gas flow control structure 31 also ensures sufficient particle separation and gas cooling of the gas flow 30, so that the ultimately exiting gas flow 30' contains significantly fewer particles 34 or no particles 34 at all and is significantly cooler than the gas flow 30 exiting the respective cell 14a. This also prevents the occurrence of a fire outside the battery 12, particularly when exiting a final outlet opening. The functionality of these main components will now be described in more detail below.

[0038] According to the invention, a coolant 20 flows through the cooling device 18, as shown on the left in the figure, at the latest when a battery cell 14a experiences thermal runaway. This flow is achieved by the pump 22 as described. Furthermore, this flow through the cooling device 18 is illustrated by the arrows 20'. This does not necessarily have to be accompanied by active cooling of the coolant 20. The cooling device 18 can thus function as an inactive cooling device. This is based on the knowledge that in the event of a detected defect in the battery 12, such as the thermal runaway of a battery cell 14a, the battery 12 is disconnected from the rest of the high-voltage vehicle electrical system, thus shutting down the high-voltage vehicle electrical system. This means that various components that are usually used to cool the coolant 20, such as the operation of an electric air conditioning compressor in a refrigerant circuit, can no longer be used.By means of the pump 22, which can be supplied by a low-voltage electrical system of the motor vehicle, the coolant 20 can be circulated within the cooling circuit 23 according to the invention and thus efficiently transports away the heat generated in the affected cell 14a. Heat transfer via the thermal path designated 24c can thus be enormously reduced. Although not shown here, such a cooling device 18 can alternatively or additionally be connected to the cell poles 14b or the cell connectors 26, for example, via electrical insulation. This also reduces heat transfer via the thermal path designated 24a in the same way.In principle, however, cooling on one of the sides of the cells 14 is also sufficient, since, for example, the underside cooling 18 shown here can dissipate sufficient heat so that ultimately hardly any heat can be transferred via the upper thermal path 24a. The same applies to the path 24b between the cells 14. In order to further reduce heat transfer via this middle thermal path 24b, it is also preferred that a thermal insulation element 38 is arranged in the space 36 between the cells. This can further reduce heat transfer between the cells 14 in this area. This makes it possible to create defined heat conduction paths, namely in the direction of the cooling structure 18, while at the same time the paths between the cells 14 are eliminated or reduced.

[0039] Furthermore, the gas 30 escaping from the affected cell 14a can be introduced into a cell degassing channel 28, as already mentioned, as illustrated in the middle representation in the figure. This allows controlled gas flow to be achieved and the escaping gas 30 to be kept separate from the cell poles 14b. This prevents arcing and further short circuits. For this purpose, the cell degassing channel 28 can be connected or attached to the respective degassing openings 16 of the cells 14, which are designed, for example, as bursting membrane openings, with a seal. For this purpose, the cell degassing channel 28 can, for example, have inlet openings 28a corresponding to the respective degassing openings 16 of the cells 14. In the figure, the middle representation shows the battery 12 in a plan view of the degassing openings 16 and the inlet openings 28a located above them in the z-direction.These inlet openings 28a can also be designed, for example, as permanent openings or as bursting membranes.

[0040] However, the temperature of this escaping, hot gas 30 can, without countermeasures, also have a retroactive effect on the temperature of the battery cells 14. Therefore, it is advantageous that the gas flow influencing structure 31 is additionally provided as part of the cell degassing channel 28. This allows for additional promotion of gas cooling and particle separation. Such a gas flow influencing structure 31 can take on various forms. In principle, it is preferred that it be integrated into an interior 40 of the cell degassing channel 28. The cell degassing channel 28 can, for example, also comprise a chamber 42 as a section, in the interior 40 of which this gas flow influencing structure 31 is integrated. In order to separate this interior 40 from an environment 44, the cell degassing channel 28 or the chamber 42 has a corresponding wall 28b, 42a.The wall 42a of the chamber 42 is part of the wall 28b of the entire cell degassing channel 28. The gas 30 can be conducted through this chamber 42 to an outlet opening 46 of the chamber 42 or of the cell degassing channel 28. This outlet opening can correspond to a final outlet opening from the motor vehicle in which the battery fire prevention system is used, or another line for gas removal can be connected to this outlet opening 46 to a final outlet opening. Such a chamber 42 can, in principle, also be arranged directly above or below the battery 12, so that, for example, the described inlet openings 28 open directly into this chamber 42. The gas flow influencing structure 31 advantageously enables gas cooling of the gas flow 30 and particle separation of the particles 34.In this example, the structure 31 comprises numerous structural elements 31a, which can be designed, for example, as zigzag-shaped or undulating sheets, which thus provide, in their interstices, numerous partial paths 48 that also run in a wavy or zigzag shape in the x-direction. This zigzag-shaped or undulating structure deflects the gas flow 30 in a respective partial path 48 several times in and against the y-direction. This separates particles 34 and slows the gas flow. In addition, thermal energy is transferred to the structural elements 31a. These can also be designed, for example, so that a coolant can flow through them and flow through them during gas removal in order to provide additional gas cooling.

[0041] The gas flow influencing structure 31 can also take on numerous other forms, not shown here. For example, it can be provided as one or more perforated plates arranged one behind the other in the x-direction. The perforated plates are preferably aligned with the x-direction, which corresponds to a main flow direction or at least a local main flow direction, and each have a plurality of holes. These holes can have diameters in the range between one millimeter and ten millimeters. This can provide a filtering effect for filtering and separating the particles 34. By arranging the holes of the respective perforated plates offset from one another, multiple deflection and division of the gas flow 30 can also be achieved, which leads to promoted particle separation and deceleration of the gas flow.

[0042] Overall, the examples demonstrate how a safety concept for an NTP (No Thermal Propagation) high-voltage battery system can be implemented, which can prevent a high-voltage battery fire in the event of a thermal runaway. In particular, a safety concept can be implemented that, when integrated into a high-voltage battery system, can lead to NTP behavior. In other words, this safety concept can stop thermal propagation and prevent a fire in the battery as well as outside the battery. The safety concept preferably includes three main components that work together as a whole.These include, as a first component, defined heat conduction paths, in particular by utilizing the thermal capacity of the cooling system, by thermally connecting the electrical cell connections and cells to cooling media, and by thermally insulating the cells. The second component is controlled gas flow, in particular through a dedicated gas channel, which is preferably connected to the bursting membrane openings of the cells with a seal. The third component is particle filtration and gas cooling, in particular through a special filter system with sufficiently large cooling capacity. Consequently, if a cell experiences thermal runaway, no propagation occurs within the high-voltage battery system, and no fire results inside or outside the high-voltage battery system.

Claims

1. Battery fire prevention system (10) for a battery (12) of a motor vehicle comprising a plurality of battery cells (14, 14a) for preventing a battery fire resulting from a thermal runaway of a first battery cell (14a) of the battery cells (14, 14a) of the battery (12), wherein the battery fire prevention system (10) has: - a cell degassing channel (28) which can be connected to the battery cells (14, 14a) of the battery (12) and into which a gas (30) exiting one of the battery cells (14, 14a) can be introduced and discharged to at least one outlet opening (46) of the cell degassing channel (28); and - a gas flow influencing structure (31) as part of the cell degassing channel (28), which structure is designed to influence the course of the gas flow (30) which flows through the cell degassing channel (28) and which is formed by the gas (30) exiting the first battery cell (14a); characterized in that - the battery fire prevention system (10) has a coolant pump (22) for circulating a coolant (20) within a cooling circuit (23), a cooling device (18) for cooling the first battery cells (14a) undergoing thermal runaway, and the cooling circuit (23) to which the cooling device (18) is connected or can be connected and through which the coolant (20) can be circulated by pumping by the coolant pump (22) in order to cool the first battery cell (14a) undergoing thermal runaway, - wherein the cooling device (18) is configured such that the coolant (20) flows through it, at the latest when the first battery cell (14a) undergoes thermal runaway.

2. Battery fire prevention system (10) according to claim 1, characterized in that the gas flow influencing structure (31) is designed to filter particles (34) carried in the gas flow (30) and / or to prevent them from reaching the outlet opening (46).

3. Battery fire prevention system (10) according to any one of the preceding claims, characterized in that the gas flow influencing structure (31) is designed to reduce a flow velocity of the gas flow (30), in particular by redirecting a flow direction of the gas flow (30) flowing in the cell degassing channel (28).

4. Battery fire prevention system (10) according to any one of the preceding claims, characterized in that the cell degassing channel (28) has a wall (28b, 42a) which separates an interior (40) of the cell degassing channel (28) from an environment (44), wherein the gas flow influencing structure (31) is arranged in the interior (40) of the cell degassing channel (28).

5. Battery arrangement having a battery fire prevention system (10) according to any one of the preceding claims.

6. Battery arrangement according to claim 5, characterized in that the battery arrangement comprises the battery (12) with the plurality of battery cells (14, 14a), wherein a respective one of the battery cells (14, 14a) has an exposable degassing opening (16) which is connected to an associated, at least exposable inlet opening (28a) of the cell degassing channel (28) in a sealed manner by a seal which is designed to at least partially prevent a gas exiting the degassing opening (16) from emerging into an environment (44) of the cell degassing channel (28).

7. Battery arrangement according to any one of claims 5 or 6, characterized in that the cooling device (18) is connected to at least one side of a respective one of the battery cells (14, 14a) and / or is arranged, via an electrical insulation, on cell connectors (26) by means of which the battery cells (14, 14a) are electrically connected.

8. Battery arrangement according to any one of claims 5 to 7, characterized in that a thermal insulation element (38) is arranged between each two adjacent battery cells (14, 14a) of the plurality of battery cells (14, 14a).

9. Motor vehicle with a battery arrangement according to any one of claims 5 to 8.

10. Method for preventing a battery fire resulting from a thermal runaway of a first battery cell (14a) of a plurality of battery cells (14, 14a) of a battery (12), - wherein a gas (30) exiting the first battery cell (14a) is introduced into a cell degassing channel (28) connected to the battery cells (14, 14a) of the battery (12) and is discharged to at least one outlet opening (46) of the cell degassing channel (28); and - the course of the gas flow (30) which is formed by the gas exiting the first battery cells (14a) is influenced by a gas flow influencing structure (31) as part of the cell degassing channel (28); characterized in that - a coolant pump (22) circulates coolant (20) within a cooling circuit (23) to which a cooling device (18) for cooling the first battery cells (14a) undergoing thermal runaway is connected and through which the coolant (20) is circulated by pumping by the coolant pump (22) in order to cool the first battery cell (14a) undergoing thermal runaway, - wherein at least the first battery cell (14a) undergoing thermal runaway is cooled by the cooling device (18) through which the coolant (20) flows.