Method for delaying and / or preventing thermal propagation events in a battery and battery system

Abstract

Method (100) for delaying and / or preventing thermal propagation events in a battery (10), in particular a traction battery for a battery-electric vehicle (300), wherein the battery (10) comprises a plurality of battery modules (11, 11a, 11b), wherein each battery module (11, 11a, 11b) comprises a plurality of battery cells (12), wherein a cooling system (13) is further provided for selectively cooling the plurality of battery modules (11, 11a, 11b), wherein it is provided that if a thermal runaway of a battery cell (12) or several battery cells (12) at a time t TR is detected, the cooling of the affected battery module (11a) is stopped at a time immediately or later than the time t TR following time t ST is terminated.

Description

[0001] The present invention relates to a method for delaying and / or preventing thermal propagation events in a battery, in particular a traction battery for a battery-electric vehicle, wherein the battery comprises a plurality of battery modules, each battery module comprising a plurality of battery cells, wherein a cooling system is further provided for selectively cooling the plurality of battery modules.

[0002] Furthermore, the present invention relates to a battery system and a motor vehicle with a battery system.

[0003] Increasing energy density and energy content in battery cells for traction batteries for battery-electric vehicles increases the risk that, in the event of thermal runaway (TR) in one battery cell, other battery cells will also be damaged or even thermally run away. When thermal runaway spreads to neighboring battery cells, this is referred to as thermal propagation (TP). If the thermal propagation event is interrupted in a controlled manner at a specific point, for example, limited to a battery module, thus preventing complete thermal propagation of the entire battery, this is referred to as stop-TP.

[0004] Current traction batteries are typically cooled by soldered battery cooling plates, which also form the battery cover or battery base of the battery housing. In the event of a thermal propagation event in a battery module, there is a risk that the heat from the affected battery module will be transferred to neighboring battery modules via the cooling medium, thereby causing thermal propagation to other battery modules in the system. Such a spread of a thermal propagation event from one battery module to the next poses significant risks to vehicle occupants and persons in the vicinity of the vehicle.

[0005] DE 10 2019 131 386 A1 discloses a temperature control device for a battery system, consisting of at least one battery pack with a cooling device, wherein a pump supplies cooling fluid to the battery pack via temperature control lines. Sensors monitor the condition of the battery pack, and the sensors can be used to control control valves in the temperature control line based on information about the condition of the battery pack.

[0006] DE 10 2021 126 471 A1 discloses a cooling arrangement for cooling a cell arrangement comprising a plurality of cell units of a motor vehicle battery. The cooling arrangement comprises a plurality of cooling units, each of the cooling units being assigned to one of the cell units, and the cooling arrangement comprises a control device configured to separately control a cooling output for each of the cooling units. The control device is configured to control the cooling units differently in a specific first cooling mode than in a specific second cooling mode different from the first, and the cooling arrangement is configured such that, in the event of a fault affecting a first cell unit of the plurality of cell units, a switch is made from the first cooling mode to the second cooling mode.

[0007] DE 10 2019 213 757 B3 discloses a cooling circuit device for a battery device with a plurality of battery modules, comprising a coolant distribution device with a coolant inlet, a plurality of cooling strands with a coolant, which are each connected to the coolant distribution device, wherein the coolant in each cooling strand and the cooling strand is in heat-exchangeable contact with a respective battery module, and wherein the coolant can be introduced into the respective cooling strands through the coolant distribution device.

[0008] The invention is based on the object of providing a method with which thermal propagation events in batteries are delayed and / or prevented.

[0009] To achieve the object underlying the invention, a method is proposed for delaying and / or preventing thermal propagation events in a battery, in particular a traction battery for a battery-electric vehicle, wherein the battery comprises a plurality of battery modules, each battery module comprising a plurality of battery cells, wherein a cooling system is further provided for selectively cooling the plurality of battery modules, wherein it is further provided that if a thermal runaway of a battery cell or several battery cells at a time t TR is detected, the cooling of the affected battery module at a time immediately or later than the time t TR following time t ST is terminated.

[0010] For the purposes of the invention, a battery module is understood to be an essentially detachable unit of interconnected battery cells. Such units can also be configured as battery stacks. Accordingly, the term "battery module" also encompasses battery stacks. The invention is therefore also applicable to "cell-to-pack"-based systems. The individual battery cells are inserted directly into the battery as a cohesive unit (battery stack). The invention can therefore be applied to at least two battery stacks.

[0011] If at a time t TR the thermal runaway of one or more battery cells of a battery module is detected, then according to the invention either immediately or at a certain time interval from the time t TRUpon detection of the thermal runaway of the battery cell or battery cells, the cooling of the affected battery module, i.e. the battery module which comprises the battery cell affected by the thermal runaway, is terminated.

[0012] Stopping cooling of the affected battery module means that heat from the affected battery module is not transferred to neighboring battery modules via the cooling system, thus delaying or even preventing the thermal runaway of the battery cell or cells from spreading to other battery modules. A further effect is that the cooling power no longer required for the affected battery module is distributed among the other battery modules in the battery, thus cooling these additional battery modules more effectively, thereby reducing the tendency for thermal propagation in the other battery modules.

[0013] For the selective cooling of the plurality of battery modules, the cooling system can have a plurality of cooling lines assigned to the battery modules, wherein the cooling lines are preferably connected in parallel. A valve can then be arranged in each of the parallel cooling lines, by means of which the corresponding cooling line can be closed and, if necessary, also opened.

[0014] The detection of thermal runaway of one or more battery cells can be achieved using suitable sensors, such as temperature sensors or gas sensors. However, detection can also be achieved through the design of the valves. For example, as will be explained further below, passive valves can be provided that close when a sufficiently high temperature is reached.

[0015] Furthermore, a control unit can be provided to control or regulate the valves.

[0016] Preferably, it is provided that if in a time before time t TR time t F a fault or an impending thermal runaway of a battery cell or several battery cells is detected, in a time t F following time t SK the cooling performance of the affected battery module is increased.

[0017] The time t SK , at which the cooling capacity of the affected battery module is increased, is before the time t ST at which the cooling of the affected battery module is stopped.

[0018] By increasing the cooling capacity of the affected battery module, if a fault or an impending thermal runaway of one or more battery cells is detected, the cooling of the affected battery module can be maximized, at least temporarily, before an actual thermal runaway of the battery cell or battery cells has occurred, thus creating an additional safety period for vehicle occupants to exit the vehicle.

[0019] An evaluation unit, in particular a computer, can be provided to detect thermal runaway of one or more battery cells and / or to detect whether a fault or the imminent occurrence of thermal runaway of one or more battery cells is present. The evaluation unit is preferably configured to evaluate signals from corresponding suitable sensors, for example, temperature sensors or gas sensors.

[0020] Furthermore, it can be provided that in order to increase the cooling capacity of the battery module concerned at time t SK the cooling of at least one, preferably several, in particular all, further battery modules is reduced, more preferably terminated.

[0021] By reducing or stopping the cooling of the other, unaffected battery modules, a larger portion, or in extreme cases even the entire volume flow, of the coolant is directed past the affected battery module, maximizing its cooling. This can further increase the safety time for evacuating the vehicle.

[0022] Furthermore, it can be provided that in a time period between the times t F and t ST , preferably between times t SK and t ST , more preferably between times t TR and t ST , time t EK a cooling capacity of the affected battery module is increased compared to the battery modules adjacent to it.

[0023] Thus, before at time t ST the cooling of the affected battery module is stopped, between the times t SK , to which the cooling of the affected module is increased, and tST , or between times t TR , at which the thermal runaway of the battery cell is detected, and t ST The cooling capacity of the battery modules adjacent to the affected battery module can be increased. This also pre-cools the battery modules adjacent to the affected battery module. This can prevent or delay the occurring internal thermal propagation from battery cell to battery cell of the affected battery module, and at the same time, the adjacent battery modules can be prepared for a higher thermal load.

[0024] In a particularly preferred embodiment, the method proceeds as follows. If at a time t F a fault or an impending thermal runaway of a battery cell or several battery cells is detected, is recorded in a time t F following time t SKthe cooling capacity of the affected battery module is increased by reducing or stopping the cooling of all other battery modules. If at a later point in time t TR If the thermal runaway of the battery cell is detected, a time t TR following time t EK the cooling of the battery modules immediately adjacent to the affected battery module is resumed so that these adjacent battery modules are cooled in addition to the affected battery module. At a time t EK following time t SK Finally, the cooling of the affected battery module is completely stopped and only the battery modules adjacent to the affected battery module are cooled with the maximum available cooling capacity.

[0025] It can be further advantageously provided that if a fault or an impending thermal runaway of a battery cell or several battery cells is detected in one of the battery modules adjacent to the affected battery module, the method is carried out for the battery module adjacent to the affected battery module.

[0026] If the thermal propagation is not stopped at the first battery module and is transferred to further battery modules, the process can be extended accordingly so that the adjacent modules are cooled according to the process.

[0027] A further solution to the problem underlying the invention consists in a battery system comprising a battery, in particular a traction battery for a motor vehicle, further in particular for a battery-electric vehicle, comprising a plurality of battery modules, each battery module comprising a plurality of battery cells, the battery system further comprising a cooling system for selectively cooling the plurality of battery modules, it being further provided that the battery system is designed to carry out a method as described above.

[0028] All features, configurations, and advantages explained in the above description of the method can be applied analogously to the battery system. Conversely, all features explained below for the battery system can also be applied analogously to the method described above.

[0029] The cooling system of the battery system preferably comprises a plurality of cooling strands assigned to the battery modules, wherein the cooling strands are connected in parallel.

[0030] In particular, it can be provided that a valve is arranged in each cooling line.

[0031] The respective valve can be located near the respective inlet or outlet or in the middle of the cooling line.

[0032] Furthermore, it can be provided that the valves are active valves or passive valves.

[0033] A passive valve can be a valve that is switched and, in particular, closed by thermal activation, in particular by the heat input from the thermal runaway of the cells. Such a valve can be implemented, for example, in the form of a bimetallic sheath of the corresponding cooling strand. Another passive valve can be designed as a wax droplet, which is released by the heat input triggered by the thermal runaway of the respective battery cell and then lodges itself in a constriction of the cooling strand, thereby partially or completely closing this cooling strand.

[0034] A further passive valve can be formed, for example, by a heating wire arranged in a fusible sleeve. Applying current to the heating wire melts the sleeve, and the cooling line is closed.

[0035] An active valve can be a controllable valve. Such actively controllable valves can be designed, for example, as solenoid valves, ball valves, or other conventional valves.

[0036] The battery system may in particular comprise a control unit for controlling or regulating the valves.

[0037] Yet another solution consists in a motor vehicle, in particular a battery-electric vehicle, with a battery system as described above.

[0038] The invention is explained in more detail below with reference to the accompanying figures. They show: Fig. 1 a battery system with a battery comprising battery modules and a cooling system, Fig. 2 the battery system, at a time after a fault or an impending thermal runaway of a battery cell or several battery cells has been detected, Fig. 3 the battery system, at a first time after a thermal runaway of one or more battery cells at a time has been detected, Fig. 4 the battery system, at a second time after a thermal runaway of one or more battery cells at a time has been detected, Fig. 5 another battery system at a time after a thermal runaway of one or more battery cells at a time has been detected, Fig. 6 a first embodiment of a passive valve, Fig. 7a a second embodiment of a passive valve in an open state, Fig. 7b the second embodiment of the passive valve in a closed state, Fig. 8 is a flowchart of a method for delaying and / or preventing thermal propagation events in a battery, and Fig. 9 a motor vehicle with a battery system.

[0039] A method 100 for delaying and / or preventing thermal propagation events in a battery 10 in accordance with the invention will be described below with reference to the Fig. 1 to 5. The battery system 200 comprises a battery 10, which serves as a traction battery for a motor vehicle 300 ( Fig. 9). The battery 10 comprises a plurality of battery modules 11, each battery module 11 comprising a plurality of battery cells 12. The battery system 200 further comprises a cooling system 13 for selectively cooling the battery modules 11. For this purpose, the cooling system 13 provides a plurality of cooling strands 14 which are assigned to the battery modules 11 and through which a coolant flows, and which are connected in parallel. Each of the cooling strands 14 is thus guided past one of the battery modules 11. Within each cooling strand 14, a valve 15 is provided, by means of which the corresponding cooling strand 14 can at least be closed, so that the cooling of the battery module 11 assigned to the corresponding cooling strand 14 can be stopped.

[0040] Fig. Figure 1 shows the case of fault-free operation of the battery 10. In this case, all valves 15 are open, so that all battery modules 11 are cooled evenly. In principle, in this state, to increase vehicle performance and service life, the valves 15 can also be controlled in such a way that temperature inhomogeneities in the battery system 200 are compensated and, for example, particularly aged battery modules 11 are cooled more effectively.

[0041] If at a time t F a fault or an impending thermal runaway of a battery cell 12 or several battery cells 12 is detected, at a time t F following time t SKa cooling capacity of the affected battery module 11a is increased. This is achieved by closing the valves 15 of all other battery modules 11, and thus the entire volume flow of the coolant is guided past the affected battery module 11a. This state is in Fig. 2, in which only the cooling line 14a assigned to the affected cooling module 11a is flowed through by cooling liquid.

[0042] If at a time t SK following time t R a thermal runaway of the battery cell 12 or of the plurality of battery cells 12 of the affected battery module 11a is detected, the cooling of the battery modules 11b adjacent to the affected battery module 11a is stopped at a time t R following time t EKThis is achieved by reopening the valves 15b arranged in the cooling lines 14b of the battery modules 11b adjacent to the affected battery module 11a. As a result, the battery modules 11b adjacent to the affected battery module 11a are thermally preconditioned in order to prevent a potentially impending thermal propagation event from spreading to the adjacent battery modules 11b. This condition is Fig. 3 shown.

[0043] Finally, if the temperature in the affected battery module 11a continues to rise, at a time t EK following time t ST , as in Fig. 4, the cooling of the affected battery module 11a can be completely stopped by closing the corresponding valve 15a in the cooling line 14a assigned to the affected battery module 11a. Thus, only the battery modules 11b adjacent to the affected battery module 11a continue to be cooled. By stopping the cooling of the affected battery module 11a, heat transfer via the coolant from the affected battery module 11a to the other battery modules 11 is prevented. The Fig. The sequence of the method 100 shown in Figures 2 to 4 can be implemented in particular when the valves 15 are actively controllable valves 15.

[0044] A simplified variant of the method 100 is shown in Fig. 5, which is particularly applicable when the valves 15 are passive, non-controllable valves. Starting from the normal state of the Fig. 1 is when a thermal runaway of a battery cell 12 or several battery cells 12 at a time t TR is detected, the cooling of the affected battery module 11b is stopped at a time immediately or later than the time t TR following time t ST finished.

[0045] The passive, non-controllable valves 15 of the simplified method 100 can be configured as shown in the Fig. 6, Fig. 7a and Fig. 7b. In the case of the valve 15 according to Fig. 6 is a bimetallic sheath 16 on both sides of the corresponding cooling strand 14. If the temperature rises sharply due to thermal runaway of the battery cells 12, the bimetallic sheath 16 deforms and compresses the cooling strand 14, as shown by the arrows 17, so that only a greatly reduced flow cross-section 18 remains. In principle, the bimetallic sheath 16 can also be arranged on only one side of the cooling strand 14.

[0046] Another embodiment of a passive, non-adjustable valve 15 is shown in Fig. 7a and Fig. 7b. The valve 15 consists of a heating wire 20 inserted into a fusible sleeve 19 arranged within the cooling line 14. If at time t TR a thermal runaway of a battery cell 12 or several battery cells 12 is detected, the heating wire 20 is energized and the sleeve 19 melts, so that the cooling strand 14 is closed ( Fig. 7b).

[0047] Fig. 8 shows a flowchart of the method 100. In a first method step S1, at a time t TR a thermal runaway of a battery cell 12 or several battery cells 12 is detected. In a second method step S2, the cooling of the affected battery module 11a is stopped at a time immediately or later than the time t TR following time t ST finished.

[0048] Fig. 9 shows a motor vehicle 300 with a battery system 200 as described above. The motor vehicle 300 is designed as a battery-electric vehicle 21. List of reference symbols 100 procedures 200 battery system 300 motor vehicles 10 Battery 11 Battery module 11a Affected battery module 11b Adjacent battery module 12 battery cells 13 Cooling system 14 Cooling line 14a Cooling line 14b Cooling line 15 Valve 15a Valve 15b Valve 16 bimetal sheath 17 Arrow 18 Flow cross-section 19 Fusible sleeve 20 heating wires 21 Battery electric vehicle S1 Process step S2 process step QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 131 386 A1

[0005] DE 10 2021 126 471 A1

[0006] DE 10 2019 213 757 B3

[0007]

Claims

[1] Method (100) for delaying and / or preventing thermal propagation events in a battery (10), in particular a traction battery for a battery-electric vehicle (21), wherein the battery (10) comprises a plurality of battery modules (11, 11a, 11b), wherein each battery module (11, 11a, 11b) comprises a plurality of battery cells (12), wherein a cooling system (13) is further provided for selectively cooling the plurality of battery modules (11, 11a, 11b), characterized by that if a thermal runaway of a battery cell (12) or several battery cells (12) at a time t TR is detected, the cooling of the affected battery module (11a) is stopped at a time immediately or later than the time t TR following time t ST is terminated. [2] Method (100) according to claim 1, characterized by that if in a time before time t TR time t Fa fault or an impending thermal runaway of a battery cell (12) or several battery cells (12) is detected, in a time t F following time t SK a cooling capacity of the affected battery module (11a) is increased. [3] Method (100) according to claim 2, characterized by that in order to increase the cooling capacity of the affected battery module (11a) at time t SK the cooling of at least one, preferably several, in particular all, further battery modules (11, 11b) is reduced, more preferably terminated. [4] Method (100) according to one of the preceding claims, characterized by that in a time interval between times t F and t ST , preferably between times t SK and t ST , preferably between times t TR and t ST , time t EKa cooling capacity of the affected battery module (11a) adjacent battery modules (11b) is increased. [5] Method (100) according to one of the preceding claims, characterized by that, if a fault or an impending thermal runaway of a battery cell (12) or of several battery cells (12) is detected in one of the battery modules (11b) adjacent to the affected battery module (11a), the method is carried out for the battery module (11b) adjacent to the affected battery module (11a). [6] Battery system (200) comprising a battery (10), in particular a traction battery for a motor vehicle (300), further in particular for a battery-electric vehicle (21), comprising a plurality of battery modules (11, 11a, 11b), wherein each battery module (11, 11a, 11b) comprises a plurality of battery cells (12), wherein the battery system further comprises a cooling system (13) for selectively cooling the plurality of battery modules (11, 11a, 11b), characterized by that the battery system is designed to carry out a method (100) according to one of the preceding claims. [7] Battery system (200) according to claim 6, wherein the cooling system (13) has a plurality of cooling strands (14, 14a, 14b) associated with the battery modules (11, 11a, 11b), wherein the cooling strands (14, 14a, 14b) are connected in parallel. [8] Battery system (200) according to claim 7, wherein a valve (15, 15a, 15b) is arranged in each cooling strand (14, 14a, 14b). [9] Battery system (200) according to claim 8, wherein the valves (15, 15a, 15b) are active valves or passive valves. [10] Motor vehicle (300), in particular battery-electric vehicle (21), with a battery system (200) according to one of claims 6 to 9.

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