High voltage battery system

Abstract

The invention relates to a high-voltage battery system having at least one cell assembly consisting of battery cells (Z1 to Zn) and respectively arranged in between heat-insulating layers (3), wherein when a critical temperature limit value (T K ), a thermal runaway (TR1) occurs, in which a high amount of energy can be released, resulting in a heat propagation (TP), in which at least one adjacent battery cell (Z2) can be heated by heat transfer processes, in which the temperature in the adjacent battery cell is exceeded by a temperature limit value (T K ) also occurs in the case of a thermal runaway (TR2). According to the invention, upon detecting at least an imminent thermal event in a battery cell (Z1), the battery management system (BMS) starts reducing the state of charge of an adjacent battery cell (Z2), in particular starts a rapid discharge (ΔE).

Description

Technical Field

[0001] The invention relates to a high-voltage battery system and a method for interrupting or delaying the propagation of heat in a cell assembly of such a high-voltage battery system. Background Art

[0002] In lithium-ion battery cells installed in the vehicle's high-voltage battery system, fault conditions may occur due to internal cell defects, such as local short circuits between the electrodes of the battery cell. Such fault conditions can lead to thermal events and thermal runaway (i.e., Thermal Runaway or thermal runaway). Thermal runaway initially only involves a single cell: the fault condition can cause the stored energy to be converted into heat, whereby further exothermic decomposition reactions can occur, which further enhance the runaway of the cell. If an adjacent battery cell also experiences thermal runaway (thermal runaway of an adjacent cell), this is called thermal propagation.

[0003] This type of high-voltage battery system has a cell assembly consisting of battery cells and a heat barrier layer arranged in between. In the event of a thermal event in one of the battery cells, the heat barrier layer acts to delay the propagation or prevent the propagation. To this end, the heat barrier layer can absorb energy, for example in the form of phase change enthalpy, by phase change or chemical reaction or changes in its material structure, and thus limit the heating of the barrier layer material.

[0004] By using such a thermal barrier layer in a cell composite, the available installation space for the battery cell is reduced, thereby reducing the energy density in the battery system, in particular the volumetric energy density, which is more important for vehicles than the gravimetric energy density due to the limited installation space. In the case of correspondingly high requirements on the barrier layer material (i.e. defined compressibility, low thermal conductivity, aging resistance, temperature stability, etc.), correspondingly large barrier layer material thicknesses and high production and material costs are required during the production of the barrier layer. If the barrier layer is not only to delay the heat propagation, but is also to prevent it, the required barrier layer material thickness increases and correspondingly expensive barrier layer materials are required, so that the use of high-energy battery cells may no longer be possible in terms of cost and energy optimization.

[0005] DE 10 2018 203 164 A1 discloses a safety system and a method for carrying out an emergency discharge function in a battery. Summary of the invention

[0006] The object of the present invention is to provide a high-voltage battery system in which, on the one hand, the cell assembly has a greater energy density than in the prior art and, on the other hand, has an increased delay effect during heat propagation compared to the prior art.

[0007] The technical problem is solved by a high-voltage battery system having at least one cell assembly consisting of a battery cell and a respectively intermediately arranged thermal barrier layer, wherein when a temperature limit value critical for stability in the battery cell is exceeded, a thermal runaway occurs in the battery cell, in which a high amount of energy can be released, so that heat propagation occurs, in which at least one adjacent battery cell can be heated by a heat transfer process, in which adjacent battery cell a thermal runaway also occurs when the temperature limit value is exceeded, wherein the battery management system, when detecting at least an imminent thermal event in the battery cell, initiates a reduction in the state of charge of the adjacent battery cell, in particular initiates a rapid discharge, by reducing the state of charge of the adjacent battery cell the amount of energy that can be released in the adjacent battery cell in the event of thermal runaway can be reduced, whereby further heat propagation to further adjacent battery cells can be prevented or delayed, in particular in combination with the respectively adapted intermediately arranged thermal barrier layers. The technical problem is solved by a method for interrupting or delaying heat transfer in a cell assembly of the high-voltage battery system.

[0008] The present invention relates to a high-voltage battery system having at least one cell assembly, which consists of battery cells and thermal insulation layers arranged in between. In the event of a thermal event in a battery cell, if a critical stability temperature is exceeded, thermal runaway occurs, in which a large amount of energy is released. This leads to heat propagation, in which at least one adjacent battery cell is heated by a heat transfer process, in which thermal runaway also occurs when a critical limit temperature is exceeded. The battery management system begins to reduce the charge state (or load state) of the adjacent battery cell, in particular to start rapid discharge, when at least an impending thermal event or an already occurring thermal event is detected in the battery cell. The amount of energy that can be released in the adjacent battery cell and is related to the charge state can be reduced by rapid discharge, thereby preventing or delaying further heat propagation to other adjacent battery cells.

[0009] The core of the invention is the targeted combination of a heat barrier that delays the spread of heat and targeted rapid discharge of individual battery cells, i.e. a control concept for targeted reduction of the state of charge of one or more neighboring battery cells of a runaway battery cell, with the aim of delaying or completely preventing the spread of heat. The interaction of the heat barrier with emergency or rapid discharge results in an optimal balance between safety requirements and the highest possible energy density in the battery system.

[0010] The invention is based on the fact that the amount of energy released in the thermal runaway of a battery cell is dependent on its state of charge (SOC). That is, at a state of charge of 100%, the maximum amount of energy possible within the operating window is released. At a state of charge of, for example, 70% or 50%, the amount of energy is smaller.

[0011] In the sense of the present invention, a thermal barrier layer that slows down the spread is understood to be a material with a low effective thermal conductivity and a material with energy absorption capacity (e.g. phase change) or other properties that slow down the spread (e.g. expansion). These materials are referred to below as intercell materials and are not further described because their properties are known to those skilled in the art.

[0012] In addition to the inter-cell material, the battery system can also be equipped with an emergency discharge circuit or a fast discharge circuit. This circuit can be combined with the existing HV connector of the battery system or implemented separately. The emergency discharge circuit is connected to each battery cell via a separate switching element. In addition, there is also a resistor or a capacitor (such as a capacitor) in the emergency discharge circuit.

[0013] Furthermore, the individual cells of the battery system are equipped with corresponding sensors (eg voltage, temperature monitoring devices).

[0014] The functional principle within the meaning of the present invention is described below based on a cell composite having battery cells arranged in sequence along the stacking direction, wherein, by way of example, an edge cell thermal runaway. The thermal runaway of the edge cell is detected by a sensor installed therein, either in advance (early detection) or at the time of occurrence. Therefore, the time point and location of the thermal runaway (i.e. the relevant cell) can be detected by the battery management system (BMS). Due to the introduced cell interlayer, a time period is generated until the temperature in the adjacent second cell exceeds the critical temperature limit value and thermal runaway occurs. This time is used for the emergency discharge of the adjacent cell (rapid SOC reduction). Here, electrical energy is extracted from the adjacent cell by closing a separate switching element, and the state of charge is reduced. The electrical energy is either temporarily stored in a capacitor (capacitor) or converted into heat energy by a resistor. The resistor is in turn coupled to a heat sink (e.g. a vehicle structure or a cooling medium), which can conduct / buffer the generated heat. Therefore, in the case of a resistor, the electrical energy extracted from the cell is also converted into heat energy and released, but not on site (in the cell), but spatially separated from it. This results in a propagation delay / prevention effect.

[0015] The process of regulating emergency discharge / SOC rapid discharge is as follows: Similar to the pure delay caused only by the inter-cell material, first (relative to the system without inter-cell material) a larger time window is provided until the thermal runaway of the second cell starts from reaching the critical temperature limit value. By closing the switching element of the second cell, the cell is urgently discharged. Its charge state is discharged from 100% to 95%, 90%, 80%, 70%, 50%, etc., for example, depending on the characteristics of the cell and the precise design of the system. Therefore, when the critical temperature limit value is reached in the second battery and thermal runaway occurs, less energy is released. The temperature curve in the second battery extends more flatly. Less energy is transferred to the next adjacent cell (the third cell). Here, the emergency discharge system can be designed for two situations:

[0016] 1) Heat propagation stops after the second cell: The SOC reduction of the second cell is effective, so that the reduction of the energy released in the thermal runaway of the second cell is sufficient, so that the critical temperature limit value is not reached in the third cell. Therefore, the heat propagation is interrupted and the system can be cooled without further emergency discharge. For safety reasons, the next cell of the module (the third cell) or all other (still intact) cells or the entire system can still be further discharged by the emergency discharge system (if necessary with a lower current).

[0017] 2) The propagation from the second cell to the third cell is delayed but not stopped. Once the second cell thermally runs away, this is detected, the switch element of the second cell is disconnected, and the switch element of the third cell is closed, thereby initiating the emergency discharge of the third cell. If the third cell thermally runs away, then the fourth cell is discharged urgently, and so on. The algorithm continues until either the heat propagation can be interrupted at a certain point, or the last cell in the cell complex thermally runs away. Subsequently, although the entire module / stack or system is still thermally runaway, the propagation is significantly delayed (increasing the rescue time), and if necessary, the jump of heat propagation to adjacent modules / stacks / systems can be prevented.

[0018] The basic principle described can also be used for cells with two or more adjacent cells. Here, in the event of thermal runaway of a damaged cell, the heat is distributed to two or more adjacent cells. Emergency discharges of these adjacent cells are then initiated simultaneously. If necessary, emergency discharges of the next or next cells can then be initiated to further delay the spread of heat.

[0019] The entire concept is designed so that the time delay, the amount of energy to be extracted, the size of the emergency discharge circuit and the capacitance / resistance and its thermal connection to the heat sink are coordinated with each other in terms of cost and energy optimization and thus a higher effective energy density or lower costs can be achieved than if the propagation delay / prevention effect were achieved only by using single inter-cell material.

[0020] The basic principle is explained here with reference to angular cell types (pouch or prismatic), but can also be applied to cylindrical cells. In addition to the edge cells, four directly adjacent cells are produced in cylindrical cells in a quadrilateral packaging and six directly adjacent cells are produced in a hexagonal packaging.

[0021] In order to improve the emergency discharge of the individual cells and to reduce the self-heating of the cells during rapid discharge, more intense cooling of the individual cells, the associated modules or the entire battery system can be provided.

[0022] The main differences with the prior art are then listed in key points: a combination of design measures (materials between cells) and a regulation strategy; a combination of sensors / detection and an emergency discharge algorithm; a combination of individual switching elements (which connect the individual cells to the emergency discharge circuit); a combination of a debalancing method (described later) in order to avoid the cost / weight caused by the emergency discharge circuit and capacitors / resistors.

[0023] In the case of active unbalancing according to the invention, the opposite principle is used here, which is known, for example, from the known active balancing concepts, according to which different charge states between individual cells in a battery system are equalized: instead of the above-mentioned emergency discharge circuit, a balancing concept is applied to the battery cells, which can redistribute the energy quantity between the individual battery cells. Here, similar to the functional principle according to the invention, the time and location of the initial thermal runaway of the first cell are detected again. During the time window provided by the inter-cell material, the charge state of the adjacent cell decreases. In this case, the energy quantity extracted is not temporarily stored in an additional capacitor or converted into heat by a resistor, but is redistributed to other cells. For this purpose, the unbalancing system must be able to transfer the energy quantity inversely to the voltage drop (from a lower charge state, i.e. a lower voltage to a higher charge state, i.e. a higher voltage). This can be done, for example, inductively, i.e. by a transformer operating, for example, in the range of 3 to 6V.

[0024] In the event of debalancing, energy quantities can be transferred from one cell to one or more other cells. During thermal runaway of the first cell, at a state of charge of, for example, 90%, the second cell can thus be discharged to, for example, approximately 70%, while the third and fourth cells are charged to 100%.

[0025] If all cells are fully charged (100%, depending on the operating conditions), it is also possible to discharge individual cells (e.g. from 100% to 70% SOC) and charge the other cells to >100% SOC (e.g. six cells from 100% to 105%). In this case, the end-of-charge voltage of, for example, 4.2 V is deliberately exceeded. Although this means instability (also due to strong delithiation of the cathode) or even damage to the relevant cell, overall safety advantages are obtained if, by reducing the SOC of the second cell to 70%, the heat propagation can be stopped after the second cell. The relevant battery module / system is already in the process of heat propagation and is thus damaged. Once the heat propagation has effectively stopped, the cell with SOC>100% can be discharged slowly through, for example, a small passive balancing resistor and the defective battery system can thus be brought into a safer state.

[0026] In accordance with the functional principle according to the invention, active debalancing can be provided for two different situations:

[0027] 1) Heat propagation stops after the second cell: The SOC reduction of the second cell is effective, so that the reduction of the energy released in the thermal runaway of the second cell is sufficient, so that the temperature in the third cell does not reach the critical temperature limit. Heat propagation is thus interrupted.

[0028] 2) Although the heat propagation from the second cell to the third cell is delayed, it is not stopped. Once the second cell is thermally out of control, this is detected, and the SOC reduction of the third cell is started. Therefore, the transfer between the cells due to active debalancing is performed before the heat propagation from cell to cell. Unlike the first embodiment, however, there is the following disadvantage here, that is, the transferred electric energy will not be released / stored separately in space, but retained in the propagated cell composite. Therefore, after several debalancing processes, a critical limit is reached, from which the transfer of energy between each (remaining) cell is no longer possible. Until this time point is reached, although the heat propagation in the cell composite can be delayed (thereby increasing the rescue time), then, due to the higher SOC of the remaining cells, the heat propagation from cell to cell may occur more strongly and more quickly.

[0029] In summary, according to the present invention, the delay of heat propagation is not achieved by the single cell material alone, but by the combination of the single cell material, the sensor, the battery management system, the emergency discharge circuit and the emergency discharge regulation strategy. As a result, less single cell material needs to be used to achieve the same safety time, thereby achieving higher effective energy density and cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Next, the embodiments of the present invention are described according to the accompanying drawings.

[0031] Figure 1 A highly schematic illustration shows a single-cell assembly of a high-voltage battery system in the normal state;

[0032] Figure 2 , Figure 3a , Figure 3b , Figure 4 Views are shown, respectively, according to which thermal runaway and heat propagation in a single-cell composite are explained;

[0033] Figure 5a , Figure 5b A second embodiment of the present invention is shown; and

[0034] Figure 6a , Figure 6b , Figure 7a , Figure 7b , Figure 8a , Figure 8b Comparative examples not covered by the present invention are respectively shown. DETAILED DESCRIPTION

[0035] Figure 1 A cell assembly of a high-voltage battery system is shown within the scope required for understanding the present invention. The cell assembly has a plurality of battery cells Z1 to Z5 stacked in sequence and a heat barrier layer 3 arranged in between. For the sake of simple illustration, the battery cells Z1 to Z5 and the heat barrier layer 3 arranged in between are shown spaced apart from each other. In a practical embodiment, the battery cells Z1 to Z5 and the heat barrier layer 3 arranged in between are pressed against each other in the stacking direction with a predefined prestress.

[0036] Battery cells Z1 to Z5 Figure 1 In the example, the battery cells Z1 to Z5 and the resistor 9 are electrically connected to each other in a 2p connection (or 2p circuit), wherein two adjacent battery cells are connected to each other in a parallel circuit, and the battery cell pairs are connected in a series circuit by means of HV connectors 5. In addition, the battery management system BMS of the high-voltage battery system has an emergency discharge circuit 7, in which all battery cells Z1 to Z5 and resistors 9 are connected. In the emergency discharge circuit 7, the battery cells Z1 to Z5 and the resistors 9 are arranged in a parallel circuit with each other. It should be emphasized that the present invention is not limited to the connection type shown. Alternatively, for example, a pure series connection (i.e., a 1p connection) or a higher parallelization (i.e., 3p, 4p, ...) can also be selected.

[0037] Each battery cell Z1 to Z5 is assigned a switching element S1 to S5 which can be controlled by a battery management system BMS. In addition, each battery cell 1 has a sensor 13, by which the voltage and / or temperature of the respective battery cell 1 can be monitored. The sensors 13 are each connected to the battery management system BMS via the signal lines 15 shown.

[0038] According to the following Figure 2 and Figure 3a , 3b The following describes a scenario in which a thermal runaway TR occurs in a battery cell Z1 and a heat propagation TP occurs in a cell assembly. Figure 2 , a thermal event occurs due to a cell defect in the battery cell Z1 at the edge of the cell composite. Figure 3b As can be seen from the temperature-time diagram, the temperature T1(t) in the battery cell Z1 on the edge side exceeds the critical temperature limit value T at the time t1. K , so that a thermal runaway TR1 occurs in the damaged battery cell Z1, in which a high amount of energy is released. In the further course, a thermal propagation TP follows, in which the adjacent battery cell Z2 is heated by the heat transfer process. After the propagation duration Δt has elapsed, the temperature T2(t) in the adjacent battery cell Z2 also exceeds the critical limit value T at the time t2. K , so that thermal runaway TR2 also occurs in the adjacent battery cell Z2.

[0039] The core of the invention is that the battery management system BMS initiates a rapid discharge or an emergency discharge when a thermal event in the battery cell Z1 is detected by means of the sensor 13. To perform the emergency discharge, the battery management system BMS generates a switching signal y2 ( Figure 2 ), the switch element S2 assigned to the adjacent battery cell Z2 is closed with the switch signal to start the emergency discharge. During the emergency discharge, electrical energy ΔE is extracted from the adjacent battery cell Z2. The electrical energy ΔE extracted from the adjacent battery cell Z2 is converted into heat energy in the resistor 9.

[0040] exist Figure 3b In the temperature-time diagram of , the temperature curve T2(t) in the adjacent battery cell Z2 which is generated after the emergency discharge is performed is shown with a solid line, while the temperature curve T2'(t) which is generated without the emergency discharge ΔE is shown with a dashed line. Therefore, the maximum temperature reached during the thermal runaway TR2 is reduced by the temperature difference ΔT due to the emergency discharge ΔE performed in advance. This achieves that the temperature curve T3(t) in the further battery cell Z3 adjacent to the battery cell Z2 is kept at the critical limit temperature T K The heat transfer TP is interrupted.

[0041] According to the invention, the fact that the propagation delay effect of the heat barrier 3 between adjacent battery cells Z1 and Z2 is set so that the propagation time Δt ends only after the emergency discharge ΔE of the adjacent battery cell Z2 has ended is of particular relevance. Figure 3bThe lower switching diagram of : As soon as the battery management system BMS detects a thermal event in the edge-side battery cell Z1, the switching element S2 is switched on at time t ein To terminate the emergency discharge, the switching element S2 is closed at time t aus Disconnect again. Figure 3b In the temperature-time diagram, time point t aus A time difference Δa precedes the time t2 at which the thermal runaway TR2 in the adjacent battery cell Z2 begins. Ideally, the time difference Δa should be particularly small (ie close to zero) so that the propagation duration Δt can be as long as possible for the emergency discharge.

[0042] The adaptation according to the invention of the heat barrier layer 13 therefore provides a sufficiently large time window between successive thermal runaways TR of adjacent battery cells Z. This time window ensures that the thermal runaway TR2 in the adjacent battery cell Z2 only begins when the emergency discharge ΔE of the adjacent battery cell Z2 is complete.

[0043] Figure 4 Another embodiment of the present invention is shown. Figure 2 Differently, in Figure 5a In this case, a thermal event with subsequent thermal runaway TR3 does not occur in the edge battery cell Z1, but in the middle battery cell Z3. In this scenario, the same functional principle as in Figure 2 Works as described in 3. Figure 2 Unlike 3, in Figure 4 In , the switch elements S2 and S4 of two adjacent battery cells Z2 and Z4 are controlled and closed by control signals y2 and y4, so that an emergency discharge ΔE is performed in the two adjacent battery cells Z2 and Z4. Figure 4 In the embodiment of , the "middle battery cell" is to be understood as a battery cell that is not an edge cell, that is, a battery cell with two adjacent cells. That is, in the case of n cells (n=1...N), the middle battery cell is cell n=2...N-1.

[0044] Figure 5a and 5b A further exemplary embodiment is shown, in which the same functional principle is also used. In contrast to the previous exemplary embodiment, the energy ΔE extracted from the adjacent battery cell Z2 is not converted into heat energy in the resistor 9. Instead, Figure 5aIn the context of the debalancing performed by the battery management system BMS, the electrical energy ΔE withdrawn during the emergency discharge is redistributed to the other functional battery cells Z3 to Z5. It should be emphasized that the battery cells Z3 to Z5 are only exemplary here. Depending on the available propagation time Δt, the amount of energy to be withdrawn ΔE and the respective state of charge SOC of the individual cells, the battery management system BMS sets the respective optimal connection for the debalancing in order to carry out the emergency discharge and the charge redistribution.

[0045] Figure 6a , Figure 6b , Figure 7a , Figure 7b , Figure 8a , Figure 8b A comparative example not covered by the present invention is shown: Figure 6a This is a cell assembly consisting of battery cells Z1 to Z5, which is designed without an intermediately arranged thermal barrier. In the case of a thermal event in an edge-side battery cell Z1, a thermal runaway TR1 occurs. The high amount of energy released here leads to a thermal propagation TP, in which the adjacent battery cells Z2 to Z5 in each case thermally run away in a cascade. The thermal propagation TP continues until the last battery cell Zn in the cell assembly thermally runs away.

[0046] Basically Figure 7a The same situation is obtained in the case of the battery cell composite, in which the battery cell composite is formed by a battery cell 1 and a heat barrier layer 3 arranged in the middle. The heat barrier layer 3 only has the effect of delaying the propagation. Figure 6b Compared with the temperature-time diagram), according to Figure 7b In the temperature-time diagram, the propagation duration Δt between temporally consecutive thermal runaways TR increases, so that a temporally delayed thermal propagation TP generally occurs.

[0047] Figure 8a , 8b The comparative example shown relates to a cell assembly consisting of a battery cell 1 and a barrier layer 3 arranged in between. Figure 7a Differently, in Figure 8a The thermal barrier 3 is implemented in a space-consuming and material-intensive manner to prevent propagation. Therefore, a thermal runaway TR1 in an edge battery cell Z1 cannot lead to a thermal propagation TP in which adjacent battery cells Z1 to Zn also thermally run away.

[0048] Reference numerals list

[0049] 3. Thermal barrier layer

[0050] 5 High voltage connector

[0051] 7 Emergency discharge circuit

[0052] 9. Resistors

[0053] 13 Sensors

[0054] 15Signal lines

[0055] BMS Battery Management System

[0056] TR Thermal Runaway

[0057] TP Thermal Propagation

[0058] t1 is the time when thermal runaway begins in the battery cell

[0059] t2 is the time when thermal runaway begins in the adjacent battery cell

[0060] Δt propagation duration

[0061] Δa time difference

[0062] T K Critical temperature limit

[0063] ΔT temperature difference

[0064] Z1 to Zn battery cell

[0065] S1 to Sn switching elements

[0066] t ein Closing time of the switching element 11

[0067] t aus Turning off time of the switching element 11

Claims

1. A high-voltage battery system comprising at least one battery cell assembly consisting of battery cells (Z1 to Zn) and a heat barrier layer (3) arranged in between, wherein: When a critical temperature limit value (T) for stability in the battery cell (Z1) is exceeded K ), a thermal runaway (TR1) occurs in a battery cell (Z1), in which a high amount of energy can be released, resulting in a heat propagation (TP), in which at least one adjacent battery cell (Z2) can be heated by a heat transfer process, in which the temperature in the adjacent battery cell is exceeded by a temperature limit value (T K ), characterized in that, when a battery management system (BMS) detects at least an impending thermal event in a battery cell (Z1), it starts to reduce the charge state of an adjacent battery cell (Z2), by reducing the charge state of an adjacent battery cell (Z2), the amount of energy that can be released in the adjacent battery cell (Z2) in the event of thermal runaway (TR2), thereby, in combination with a respectively adapted intermediate thermal barrier layer, further heat propagation (TP) to other adjacent battery cells (Z3 to Zn) can be prevented or delayed, wherein a critical temperature limit value (T K ) occurs at a propagation time (Δt) after the time point (t1) at which a critical temperature limit value (T K ), and the propagation delay effect of the thermal barrier layer (3) is set so that the propagation time (Δt) ends only at the time difference (Δa) after the emergency discharge of the adjacent battery cell (Z2) ends, that is, the thermal runaway (TR2) of the adjacent battery cell (Z2) occurs only after the emergency discharge of the adjacent battery cell (Z2) ends, and the time difference (Δa) is particularly small, so that the propagation duration (Δt) can be used for emergency discharge as long as possible.

2. The high-voltage battery system according to claim 1, characterized in that: The battery management system (BMS) has an emergency discharge circuit (7) in which all battery cells (Z) and capacitors or resistors (9) are connected, and in the emergency discharge circuit (7), a switching element (S1 to S5) that can be controlled by the battery management system (BMS) is assigned to each battery cell (Z), and / or the battery management system (BMS) generates a switching signal (y2) when a thermal event is detected in a battery cell (Z1), and uses the switching signal to close the switching element (S2) assigned to an adjacent battery cell (Z2) to start emergency discharge, in which electrical energy can be extracted from the adjacent battery cell (Z2).

3. The high-voltage battery system according to claim 2, characterized in that: The extracted electrical energy is either redistributed to at least one further battery cell (Z3 to Zn) within the scope of a debalancing operation performed by a battery management system (BMS), or can be temporarily stored in a capacitor or can be converted into heat energy in a resistor (9), and the resistor (9) is coupled to a heat sink in order to dissipate the heat energy.

4. The high-voltage battery system according to claim 1, characterized in that: The energy that can be released in an adjacent battery cell (Z2) in the event of a thermal runaway (TR2) is reduced due to the emergency discharge so that the temperature increase in at least one further battery cell (Z3) adjacent to the adjacent battery cell (Z2) due to heat transfer processes is kept below a critical temperature limit value (T K ) below, so that the continuation of heat propagation (TP) has stopped in the adjacent further battery cell (Z3), and after the emergency discharge of the adjacent battery cell (Z2), an additional emergency discharge of the battery cell (Z3) adjacent to the adjacent battery cell (Z2) is achieved for safety reasons.

5. The high-voltage battery system according to claim 1, characterized in that: In order to detect thermal events, each battery cell (Z) is equipped with a sensor (13), by means of which the voltage and / or temperature of the respective battery cell (1) can be monitored and the sensor (13) is signal-connected to a battery management system (BMS).

6. The high-voltage battery system according to claim 2, characterized in that: In the case of an emergency discharge, the electrical energy quantity of the respective battery cell (Z) can be reduced by 5% to 100%.

7. The high-voltage battery system according to claim 2, characterized in that: The battery management system (BMS) starts an additional emergency discharge process when thermal runaway (TR2) is detected in an adjacent battery cell (Z2). In the additional emergency discharge process, the switch element (S2) assigned to the adjacent battery cell (Z2) is opened, and the switch element (S3) assigned to the adjacent other battery cell (Z3) is closed, so that emergency discharge of the adjacent other battery cell (Z3) can be initiated, and the additional emergency discharge process for the adjacent other battery cells (Z4, Z5) is continued until heat propagation (TP) is interrupted or until the last battery cell in the cell assembly thermally runs away.

8. The high-voltage battery system according to claim 1, characterized in that: Reducing the state of charge of the adjacent battery cell (Z2) is a rapid discharge.

9. The high-voltage battery system according to claim 5, characterized in that: The sensor (13) is a voltage and temperature monitoring device. 10 . A method for interrupting or delaying heat propagation (TP) in a cell assembly of a high-voltage battery system according to claim 1 .

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