Deactivation arrangement and method for electrically deactivating a battery unit

Abstract

The invention relates to a method for electrically deactivating a battery unit (12) with at least one battery cell (14) by discharging the battery unit (12). In this process, the battery unit (12) is discharged by externally applying a specific discharge current (I2) to a negative state of charge, thereby reversing the polarity associated with the battery unit (12), at least until a specific voltage drop (30) of a certain magnitude (U, U2) of the battery unit (12) occurs.

Description

[0001] The invention relates to a method for electrically deactivating a battery unit with at least one battery cell by discharging the battery unit. The invention further relates to a deactivation arrangement.

[0002] For hybrid and electric vehicles, for example, lithium-ion cells or cell modules are used, which can comprise several such battery cells. At the end of their service life or during cyclical disassembly for quality control purposes in ongoing production, the lithium-ion cells must be removed from the battery or cell modules, or the batteries or cell modules must be disassembled, often destructively. This poses a risk of short circuits, arcing, and fires. To conduct safe tests that will not trigger a fire even in the event of cell damage, or to commission and test new processes, systems, equipment, materials, etc., there is a need for safe cells. For this purpose, sometimes extremely expensive and custom-made dummy cells are used.A cost-effective way to provide such a dummy cell would be to electrically deactivate a conventional battery cell. While this can be achieved by electrically discharging the cell, this state is unfortunately not permanent, as cells recover even after deep discharge and become active again. Recycling, especially material recycling, can also be problematic if battery cells remain electrically active, as heat and fire can occur. Transporting damaged or critical cells is extremely expensive because a potential reaction during transport must be anticipated, precautionary measures must be taken, and very elaborate and costly packaging and transport methods are required.If cells or cell modules are to be permanently and safely deactivated, this is only possible, if at all, if they are fitted with an external short-circuit bridge after deep discharge. If cells are separated, especially if the cell poles are removed from already electrically connected and usually welded prismatic cells, maintaining the externally short-circuited state is simply no longer technically feasible, and the risk to the cells through "recovery" increases again. Furthermore, very long deep discharge and preparation times of days to weeks are sometimes necessary. Therefore, it would be desirable to have a method for permanently deactivating cells that is as time-efficient and cost-effective as possible.

[0003] DE 10 2014 207 239 A1 describes a method for disposing of an energy storage device with several electrochemical cells, wherein a balancing control unit of the energy storage device is used for targeted deep discharge of the energy storage device.

[0004] US Patent 5,656,915 A describes a method by which a group of cells can be deep discharged by transferring the energy extracted from the cells to other cells.

[0005] The problems described above still persist.

[0006] Furthermore, WO 2023 / 228 178 A1 describes a method for inducing combustion in a rechargeable lithium-ion battery. This can be achieved by externally heating the battery cell, overcharging it, applying reverse polarity to the cell, creating an external short circuit, or forcing the cell to discharge.

[0007] However, thermal runaway or burning of a battery cell during the electrical deactivation of such a cell is undesirable and should be prevented.

[0008] The object of the present invention is therefore to provide a method and a deactivation arrangement that enable the electrical deactivation of a battery cell or a group of battery cells in the most time-efficient, simple and, above all, most permanent way possible.

[0009] This problem is solved by a method and a deactivation arrangement with 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 figures.

[0010] In a method according to the invention for electrically deactivating a battery unit with at least one battery cell, the battery unit is discharged. In this process, the battery unit is discharged by externally applying a specific discharge current to a negative state of discharge, thereby reversing the polarity associated with the battery unit, at least until a specific voltage drop of a certain magnitude occurs in the battery unit.

[0011] The invention is based on the finding that a battery unit, for example a battery cell or several battery cells connected in series, can be permanently electrically deactivated by discharging it to a negative state of charge and until a specific voltage characteristic of the battery unit is observed. If the battery unit is discharged to such a negative state of charge, i.e., less than 0 percent SOC (state of charge), particularly well below 0 percent SOC, at least until a certain voltage drop occurs, the battery unit can no longer recover and remains permanently electrically deactivated. This is based on the following findings: Due to the discharge process, the initial, for example, positively defined, voltage of the battery unit drops into the negative range.As the battery unit discharges further, its voltage exhibits a characteristic behavior marked by a significant drop in magnitude. For example, the negative voltage of the battery unit rises abruptly again, but remains negative. This abrupt rise corresponds to the described voltage drop in magnitude. This behavior of the voltage curve is due to processes occurring in at least one cell of the battery unit during polarity reversal: In the case of a lithium-ion cell, the solid electrolyte interface (SEI) dissolves, producing gas, and copper is oxidized to copper ions, which pass through the separator. Metallic copper is then deposited on the counter electrode.The deposition of metallic copper forms dendrites, which grow while the discharge current is maintained through the insulating separator. This process creates a lasting internal short circuit within the battery cell, as copper is a very good conductor. As a result, the internal resistance of the battery cell drops significantly, especially compared to the relatively high internal resistance of a cell during deep discharge, to a cell voltage that would be reached without polarity reversal. This significant drop in internal resistance is noticeable as a voltage drop between the voltage of the battery unit and the voltage of at least one battery cell it contains. Other battery cells with different cell chemistries exhibit a completely analogous behavior.Once this voltage drop has occurred, the at least one battery cell, and especially the battery unit, is permanently internally short-circuited and cannot recover. In this way, the battery unit can be permanently deactivated into a safe state. Thus, the battery unit can be completely and sustainably deactivated electrically and energetically. This also makes recycling such a battery unit, especially shredding and material recycling, possible without any problems, and prevents heat generation, fire, or damage to the internal materials of the at least one battery cell in the battery unit, particularly the graphite in the case of a lithium-ion cell. Electrically deactivated battery units or individual cells can also be easily and inexpensively produced as dummy units.These dummy cells can be used like normal cells, and the cell terminals can also be welded for testing purposes, as there is no external short-circuit bridge on the outside of the cell, unlike a normal deeply discharged dummy cell. In particular, this provides a method for permanently disabling prismatic and / or cuboid lithium-ion cells electrically before removing the commonly welded cell terminal connectors by drilling out the cell terminal rivets, which would otherwise make maintaining the short-circuited state impossible. Transport and packaging costs can be reduced by eliminating the reactivity and hazards of lithium-ion cells and the battery units comprising them, especially those cells that are damaged, in a critical condition, or are being transported for disposal or recycling anyway.An external electrical short-circuit bridge is no longer required. The deactivated state cannot be accidentally reversed externally, for example, by removing or cutting the short-circuit bridge. Furthermore, the method enables particularly rapid deactivation of the battery unit, especially compared to the otherwise typical deep discharge of such a cell to a still positive state of charge or to a minimum of 0 percent SOC. In particular, the method makes it possible to deactivate such a battery unit within a few minutes.

[0012] A battery unit can refer to a single battery cell or a group of several battery cells electrically connected, for example, in a series and / or parallel circuit. A battery unit can also be understood as a battery module with multiple battery cells, which may be connected in series and / or parallel. The battery module may, for example, comprise a series connection of several cell groups, where each cell group may contain several battery cells connected in parallel. The at least one battery cell is, for example, a lithium-ion cell. This cell may be a prismatic, pouch, or cylindrical cell.

[0013] As is well known, such a battery unit is assigned a specific polarity. In other words, a battery unit typically has a defined positive terminal and a negative terminal, or more generally, two terminals to which different potentials are assigned, with the higher potential typically being referred to as the positive terminal and the lower potential as the negative terminal.

[0014] The reversal of this polarity, as used in the described procedure, can be achieved, for example, by applying a counter-voltage to the battery unit, that is, an external voltage with inverse polarity. This allows a discharge current to be imposed on the battery unit, i.e., forced upon it, which is opposite to its actual polarity.

[0015] Due to this discharge process, the initial, for example, positively defined, voltage of the battery unit drops into the negative range. Thus, the voltage of the battery unit changes its sign over time during the discharge process. Upon further discharge of the battery unit after this sign change, the voltage then exhibits a characteristic behavior, marked by a significant drop in the magnitude of the voltage, in particular a rapid increase in the negative voltage. The negative voltage of the battery unit, for example, rises abruptly again, but remains (initially) negative. This abrupt increase corresponds to the described drop in the magnitude of the voltage of the battery unit. This behavior of the voltage curve is due to the processes already described above in the at least one battery cell of the battery unit during the polarity reversal.The application of the discharge current can then be terminated. After the discharge current is switched off, the voltage of the battery unit, and in particular of its at least one cell, may show a brief overshoot, and then gradually decreases to 0 V (volts) or nearly 0 V, for example to 10 mV to 20 mV, depending on the waiting time after the discharge current is switched off.

[0016] A negative state of charge (SOC) can be achieved by reverse charging at least one battery cell or the battery unit. The negative SOC value can be defined by the discharge current relative to the nominal capacity assigned to the battery unit. For example, if the battery unit has a nominal capacity of 160 Ah, and 160 Ah are discharged from it at a current of, say, 160 A for one hour, the battery unit will subsequently have a SOC of 0 percent. If further charge is then drawn from the battery unit, for example, 16 Ah, which corresponds to 10 percent of its nominal capacity, it will reach a resulting SOC of -10 percent.

[0017] The term "negative state of charge" does not necessarily refer to a specific state of charge; it can refer to any negative state of charge. A negative state of charge can be associated with a negative voltage value. If the battery initially has a positive voltage, it can, for example, first be discharged until its voltage reaches a certain, still positive, value, such as 1% of its nominal voltage. The battery can then be further discharged by reversing the polarity by applying a counter-voltage until its voltage switches to the negative range, thus indicating a negative state of charge. It can then be discharged further, at least until the characteristic voltage increase occurs. The negative voltage value does not necessarily have to be a minimum value.The minimum negative voltage reached during discharge can vary depending on factors such as cell chemistry, discharge current, and battery capacity. This minimum voltage response is determined by the applied discharge current itself. The applied discharge current can be constant or variable. A discharge rate of 1 / 4 C to approximately 1 / 3 C has proven particularly effective, which, for a typical 160 Ah cell, would correspond to a current of approximately 40 A to 60 A.The voltage curve during discharge exhibits a characteristic pattern: the voltage initially becomes negative, then continues to fall until it reaches a minimum or minimum region, where it remains for a period of time. This is followed by a relatively abrupt rise in the negative voltage, known as the voltage drop. After this abrupt rise, the negative voltage slowly approaches zero, even with a constant current flow. The curve of the negative voltage then becomes relatively flat over time, meaning it is flatter than during the period of the abrupt rise. It is in this flat region that the external current or back EMF can be switched off.Switching off can lead to a voltage overshoot, in which the voltage rises very slightly into the positive range, but then asymptotically approaches zero over time. Depending on the waiting time or the point in time after the deactivation process, a very small and therefore negligible (positive) residual voltage of approximately 20 mV to 30 mV may be present. At this point, the battery unit can already be considered irreversibly deactivated, as the voltage can no longer rise. Once this abrupt rise in the negative voltage has occurred, it is ensured that a recovery of the cell(s) of the battery unit is impossible. Therefore, the battery can simply be discharged until this voltage drop has occurred.This voltage drop can be detected, or a predetermined time period for the discharge can be set so that it can be safely assumed that the voltage drop has occurred.

[0018] To discharge the battery unit at least until a specific voltage drop occurs—more precisely, until the magnitude of the voltage drop is reached—the battery unit's voltage does not necessarily need to be measured. The duration for which the specific discharge current must flow, starting from a given initial state of charge, can be determined in advance for a similarly constructed battery unit. Continuing to discharge the battery unit after the specified voltage drop has occurred has no negative effect. In other words, the discharge current does not necessarily have to be switched off immediately after this specific voltage drop occurs. The discharge current can be maintained for a certain period, e.g., a few minutes, after this voltage drop has occurred.The occurrence of this specific voltage drop ensures that the battery unit is now in an irreversibly damaged state and is now safely electrically deactivated and cannot recover. After switching off the specific, applied discharge current, a predetermined period of time can also be observed, ensuring that after this period the battery unit is safely deactivated and, for example, its residual voltage does not exceed a certain limit, such as 100 mV, and cannot exceed this limit again over time.

[0019] According to a further advantageous embodiment of the invention, the battery unit is discharged to a negative state of charge for a predetermined period and / or until it is detected that the voltage of the battery unit meets a specific criterion, which at least includes the occurrence of a specific voltage drop. In the former case, a predetermined period can be specified for which the battery unit is discharged. The temporal criterion is a criterion relating to the voltage's behavior over time. This period can be defined for a specific initial state of charge of the battery unit, for a specific nominal capacity of the battery unit, and for a specific discharge current or current intensity. In this case, it is therefore not necessary to detect or monitor the voltage of the battery unit during discharge.Nevertheless, this can still be provided as an alternative or additional measure. This advantageously allows for the detection of a specific voltage drop. The voltage of the battery unit can therefore be recorded, particularly repeatedly or continuously, and the voltage profile monitored for the occurrence of this specific voltage drop. As soon as this occurs or is detected, the specific profile criterion can be considered fulfilled. An optional further period of time can then be waited until the application of the discharge current is finally terminated.

[0020] The voltage drop can be characterized by the fact that the magnitude of the voltage changes by more than a predetermined limit within a specific (short) time period. In other words, the occurrence of the voltage drop can be characterized by the magnitude of the time derivative of the voltage exceeding a predetermined limit. Additionally or alternatively, the voltage drop can also be characterized by the magnitude of the voltage falling below a predetermined limit. This, too, can be included in the specific characteristic criterion. Furthermore, the characteristic criterion can include that the magnitude of the voltage decreases when the voltage drop occurs. These criteria allow for the reliable detection of the voltage drop.

[0021] According to a further advantageous embodiment of the invention, in a first discharge phase, the battery unit is discharged to a first positive state of charge without the application of a discharge current. Once the first state of charge is reached, in a second discharge phase, the battery unit is discharged to a second negative state of charge, which can be the aforementioned negative state of charge, by reversing the polarity and externally applying a specific discharge current, in particular by applying an external counter-voltage. The battery unit can, for example, initially be in any positive state of charge. This can also be referred to as the initial state of charge or starting state of charge of the battery unit. The voltage exhibited by the battery unit in this initial state of charge can be defined as positive without limitation of generality.In the first discharge phase, the battery unit can initially be discharged to a lower, but still positive, initial state of charge. This can be defined, for example, by the voltage exhibited by the battery unit at this initial state of charge. At this initial state of charge, the battery unit can be completely or almost completely discharged. To then achieve a negative state of charge, the polarity of the battery unit can be reversed by applying a specific discharge current through an external counter-voltage. In other words, a counter-voltage with the opposite polarity can be applied to the battery unit or its terminals. During the initial discharge phase, however, the discharge can be carried out, for example, through a conventional resistor, a load, or a similar device.In the simplest case, the terminals of the battery unit can be short-circuited via a resistor. Alternatively, the charge drawn from the battery unit can be stored in another storage unit connected to the battery unit during the initial discharge phase, for example, another battery or battery cell, a capacitor, or similar device.

[0022] The fact that the battery unit discharges to the first positive state of charge without imposing a discharge current can be understood to mean that no external current or voltage source is required to generate the discharge current. The battery unit can be connected to a load, electrical resistance, or general current sink, and the discharge current in the first discharge phase then flows spontaneously, i.e., driven by the voltage of the battery unit itself.

[0023] The point at which the external counter-voltage or current source is applied can be defined, for example, by reaching a specific (positive) voltage value of the battery unit. This voltage value can be defined as being greater than 0% of the nominal voltage of the battery unit, for example, within a range between 0% and 5%, e.g., at approximately 1% of the nominal voltage. If the battery unit exhibits this voltage value, the state of charge it assumes at that time can be defined as the initial state of charge. In general, however, the counter-voltage or current source can also be activated at higher cell voltages. For example, one could begin at 100% of the cell voltage, i.e., activate the counter-voltage or current source and set a discharge current of ¼ C, e.g., with the option to release the current upon reaching or exceeding this value.Even when the cell voltage crosses 0 volts, negative voltages are also permitted.

[0024] According to a further advantageous embodiment of the invention, the first positive state of charge is thus reached when the voltage of the battery unit is a certain value greater than 0 percent of the nominal voltage. The battery unit can therefore, for example, be discharged from its initial state of charge to one hundredth of its nominal voltage. No counter-voltage is required for this, so that the first discharge phase can be carried out very energy-efficiently and, optionally, the charge extracted from the battery unit can even be stored elsewhere.

[0025] According to a further advantageous embodiment of the invention, the discharge current during the first discharge phase is limited to a specific first maximum value, which in particular does not exceed a C-rate of approximately 0.7 C, at least without active cooling. The C-rate is related to the nominal capacity of the battery unit. For example, if the battery unit has a nominal capacity of 100 Ah, a C-rate of 1 C corresponds to a current of 100 A. A C-rate of 2 C corresponds to a discharge current of 200 A. In general, the discharge current can be calculated from the C-rate as follows: I=(x⋅K) / h.

[0026] The discharge current in amperes is denoted by I, x is the numerical value of the C-rate, K is the nominal capacity of the battery unit in ampere-hours, and h represents the unit hours.

[0027] Higher discharge currents are also conceivable, but these lead to increased heating of the battery unit. To prevent excessive heat buildup, the battery unit must be actively cooled at higher charging currents. However, this is energy-inefficient. High currents also require a more robust system design with regard to current-carrying capacity, which in turn incurs additional costs. Therefore, it is very advantageous to limit the discharge current during the initial discharge phase. For moderate discharge rates up to a maximum of approximately 0.7C, cooling of the battery unit is not necessary during the initial discharge phase. Thus, it is highly beneficial to limit the maximum discharge current initially, i.e., during the first discharge phase. The upper limit for the discharge current can also be less than 0.7C, for example, 0.25C.

[0028] According to a further advantageous embodiment of the invention, in the second discharge phase, the discharge current is limited to a specific second maximum value, which is particularly lower than the first maximum value. During the second discharge phase, in which the battery unit is subjected to a discharge current with the opposite polarity to its own polarity, the battery cell or battery unit is no longer operating within its normal range. Therefore, it is advantageous to limit the discharge current even more significantly in this second discharge phase to prevent excessive overheating and stress on the at least one battery cell. This reliably prevents thermal runaway of the battery cell during discharge.It is also conceivable that the first maximum value for the discharge current during the first discharge phase is chosen to be as large as the second maximum value for the discharge current in the second discharge phase, and correspondingly significantly smaller than, for example, 0.7 C.

[0029] Furthermore, it is very advantageous, though not necessary, for the discharge current to be constant during the first and / or second discharge phases. This means, for example, a constant current (CC) discharge is performed. This is particularly easy to implement technically and also leads to easily reproducible results, for example, without having to monitor the battery unit's voltage each time.

[0030] According to a further highly advantageous embodiment of the invention, the discharge current in the second discharge phase essentially corresponds to a C-rate of 0.25 C, and in particular, it is essentially constant. The fact that the discharge current in the second discharge phase essentially corresponds to a C-rate of 0.25 C can include a discharge current that is, for example, in the range between 0.1 C and 0.3 C, preferably between 0.2 C and 0.3 C. Discharging with a discharge current corresponding to a C-rate of 0.125 C would also be conceivable. However, this would again extend the duration of the second discharge phase, and the convergence of the battery unit voltage to zero after the discharge current is switched off would also take longer. In other words, at a C-rate of approximately 0.25 C, the reliably deactivated state of the battery unit can be reached particularly quickly.This state could be reached even faster, but without any significant time advantage, at even higher C-rates. However, this is more expensive and complex, as the corresponding components of the deactivation circuit would have to be designed for higher currents, and cooling of the battery unit might also be necessary. Therefore, a discharge current of approximately 0.25 C has proven to be particularly advantageous.

[0031] According to a further advantageous embodiment of the invention, the higher back EMF is limited to a maximum value that depends on the number of battery cells comprised of the battery unit. Preferably, the magnitude of the back EMF is a maximum of 2 V x n, where n represents the number of battery cells or cell groups connected in series by the battery unit. A cell group can, for example, comprise several individual cells connected in parallel. Thus, if the battery unit comprises, for example, five battery cells or cell groups connected in series, the maximum back EMF, or its magnitude, is 10 V. This enables particularly gentle discharge to a negative state of charge without the risk of overheating the cell or causing excessively high discharge currents.If the battery unit is to be discharged with a constant discharge current, the counter-voltage applied to the battery unit can vary over time, but in such a way that its defined maximum amount is not exceeded.

[0032] According to a further advantageous embodiment of the invention, the battery unit comprises several battery cells connected in series and / or parallel. This has the significant advantage that, for example, battery modules comprising several battery cells connected in series and / or parallel do not need to be disassembled for deactivation. Battery modules, as an example of the battery unit, can be deactivated as a whole using the method according to the invention or one of its embodiments. Nevertheless, the described method can also be applied analogously to individual battery cells. In other words, the battery unit can also consist of just a single battery cell.

[0033] Furthermore, the invention relates to a deactivation arrangement for electrically deactivating a battery unit with at least one battery cell, wherein the deactivation arrangement comprises a discharge unit designed to discharge the battery cell. In addition, the discharge unit is designed to discharge the battery cell to a negative state of charge by externally applying a specific discharge current, thereby reversing the polarity associated with the battery unit, at least until a specific voltage drop of a certain magnitude occurs in the battery unit.

[0034] The advantages described for the method according to the invention and its embodiments apply in the same way to the deactivation arrangement according to the invention.

[0035] The discharge unit can include, for example, a resistor, load, energy storage device, or similar component for discharging the battery unit, particularly during the initial discharge phase. To apply the specific reverse-polarized discharge current, the discharge unit can, for example, include a reverse-polarized voltage source. The deactivation arrangement can also include a control unit to manage the discharge process. For instance, the aforementioned components, such as the electrical resistor, load, or additional energy storage device, can be coupled to and decoupled from the battery unit via switching elements, as can the counter-voltage or counter-voltage source. The control of these switching elements can be handled by the control unit.Optionally, the deactivation arrangement can also include a voltage measuring device to measure the voltage of the battery unit, particularly repeatedly or continuously during the discharge process and / or even after the discharge current has been switched off. This voltage measuring device can transmit its measured values ​​to the control unit. Depending on the measured values, the control unit can initiate the application of a specific discharge current with the opposite polarity and switch off the discharge current after the voltage drop occurs.

[0036] In general, the deactivation arrangement can be designed to carry out a method according to the invention or one of its embodiments.

[0037] The invention also includes the control unit for the deactivation arrangement. The control unit can comprise a data processing device or a processor circuit configured to perform an embodiment of the method according to the invention. For this purpose, the processor circuit can comprise at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (Field Programmable Gate Array) and / or at least one DSP (Digital Signal Processor). In particular, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an NPU (Neural Processing Unit) can be used as the microprocessor. Furthermore, the processor circuit can comprise program code configured to perform the embodiment of the method according to the invention when executed by the processor circuit.The program code can be stored in a data memory of the processor device. The processor device can be based, for example, on at least one circuit board and / or on at least one SoC (System on Chip).

[0038] The invention also includes further developments of the deactivation arrangement according to the invention, which have features already described in connection with the further developments of the method according to the invention. For this reason, the corresponding further developments of the deactivation arrangement according to the invention are not described again here.

[0039] The invention also includes combinations of the features of the described embodiments. The invention therefore also includes realizations that each exhibit a combination of the features of several of the described embodiments, provided that the embodiments have not been described as mutually exclusive.

[0040] The following are exemplary embodiments of the invention described. This is illustrated by: Fig. 1 a schematic representation of a deactivation arrangement in a state during the first discharge phase according to an embodiment of the invention; Fig. 2 a schematic representation of the deactivation arrangement in a second state during the second discharge phase according to an embodiment of the invention; and Fig. 3 a graphical representation of the voltage curve and a current curve of the discharge current during the second discharge phase until the complete deactivation of the battery unit according to an embodiment of the invention.

[0041] The exemplary embodiments described below are preferred embodiments of the invention. In these exemplary embodiments, the described components each represent individual features of the invention, which can be considered independently of one another and each further develops the invention independently. Therefore, the disclosure is intended to include combinations of features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0042] In the figures, identical reference symbols denote functionally equivalent elements.

[0043] Fig. Figure 1 shows a schematic representation of a deactivation arrangement 10 in a first state Z1 and during a first discharge phase according to an embodiment of the invention. The deactivation arrangement 10 comprises a battery unit 12, for example, a battery module with several battery cells 14 connected in series. The battery unit 12 comprises two terminals 16, 18 with a polarity illustrated by "plus" and "minus". In this example, and in the first discharge phase, the terminal labeled 16 is the positive terminal and the terminal labeled 18 is the negative terminal of the battery unit 12. In a normal operating state, the battery unit 12 provides a voltage U at its terminals 16, 18 with the illustrated polarity.The positive voltage U of the battery unit during this first discharge phase is also designated U1 to more easily distinguish it from the subsequent negative voltage U2 in the second discharge phase. The deactivation arrangement 10 further comprises a circuit arrangement 20 and a control device 22. The circuit arrangement 20 includes, for example, a controllable or variable resistor 23, which can be electrically connected to the poles 16, 18 of the battery unit 12 via first switching elements S1 and is connected in this illustration. Thus, the battery unit 12 can be discharged via the resistor 23. The battery unit 12 is discharged with the discharge current I1. The discharge can continue until the voltage U of the battery unit 12 reaches a certain value, which corresponds, for example, to one percent of the nominal voltage of the battery unit 12.The deactivation arrangement 10 can also include a voltage measuring device 24 to measure the voltage U of the battery unit 12 during operation. This makes it possible to determine when this specific voltage value of the battery unit 12 is reached. (See figure in...) Fig. Therefore, battery unit 12 has a state of charge (SOC) that is even greater than the first state of charge (SOC1) corresponding to this first voltage value. Once this voltage value, or the corresponding state of charge (SOC1), is reached, a discharge current I2 with reverse polarity is applied to battery unit 12.

[0044] This is in Fig. 2 illustrated. Fig. Figure 2 shows the deactivation arrangement 10 from Fig. 1, where the first switches S1 are now open and the second switches S2 are closed. A counter-voltage source 26 is connected via these to the poles 16, 18 of the battery unit 12 in reverse polarity. The control of switches S1, S2 is carried out by the control unit 22. This can also receive and evaluate the measured values ​​of the voltage measuring device 24 or use them to control switches S1, S2. By applying this discharge current I2 with the inverse polarity, the battery unit 12 can be discharged to a state of charge SOC2 less than 0% SOC. The counter-voltage 26 remains coupled to the battery unit 12, or the discharge current I2 is applied, until the voltage U of the battery unit, which is now also designated U2, exhibits a certain characteristic, in particular until a certain absolute voltage drop 30 (cf. Fig. 3) is evident. After this voltage drop 30 occurs, the discharge current I2 can be deactivated. This is done, for example, by opening the switches S2. In this state, neither the counter-voltage source 26 nor the resistor 23 is connected to the battery unit 12. The battery unit 12 is then irreversibly damaged and cannot recover. After a certain relaxation phase, its voltage drops to approximately 0 V. This is again in Fig. 3 illustrated.

[0045] Fig. Figure 3 shows a graphical representation of the voltage U of battery unit 12 and the discharge current I2 during the second discharge phase and the period after the applied voltage or current is switched off. The Fig. The graphic described in section 3 shows the current, voltage and time profile using a single cell 14 as an example.

[0046] After a short time, approximately 5 to 15 minutes, the negative voltage at the individual cells drops massively by about a factor of 4. This is also known as voltage drop.

[0047] At time t0, for example, the counter-voltage source 26 is switched on, or rather, switches S2 are closed and switches S1 are opened accordingly. Switches S1 may also have already been opened earlier. The battery unit 12 is then initially discharged with a constant discharge current I2, in this example 40 A. In general, the maximum current can be set to approximately 0.25 C. The current limit is preferably determined by the ratio of the current to the nominal capacity of all parallel-connected lithium-ion cells. The polarity of the voltage of the battery unit 12 reverses accordingly and drops into the negative range. After a short time, approximately 5 to 15 minutes, e.g., relative to time t0, the negative voltage across the individual cells 14 drops significantly by about a factor of 4. This is also referred to as the current-voltage drop.A significant voltage drop of the magnitude of voltage U occurs, illustrated by 30. After this voltage drop 30 occurs, the voltage U changes only slowly. At time t1, the counter-voltage source 26 is switched off, or the application of the discharge current I2 is terminated. The voltage U then approaches the value 0 V.

[0048] Overall, the examples demonstrate how the invention can provide electrical and / or energetic deactivation of lithium-ion cells. The lithium-ion cells are electrically discharged, for example, at the point when they are readily electrically conductive, whether as a single cell (e.g., for a battery unit), as a cell module or stack, or as an entire high-voltage battery (e.g., for a battery unit). The discharge goes well below the cells' normal operating range and thus also well below 0 percent state of charge (SOC), until only about one-hundredth of the nominal voltage remains. For a single cell, for example, this would be about 35 mV. No cooling is required for the discharge at moderate power levels up to a maximum of approximately 0.7 C. It is also advantageous if the maximum current is initially limited.Afterwards, one cell or several cells in a series or parallel can be electrically reversed simultaneously, i.e., subjected to a reverse voltage. The magnitude of the reverse voltage can be set to -2 V times the number of series-connected lithium-ion cells using the so-called CC method (Constant Current, direct current).

[0049] The negative voltage triggers electrochemical processes inside the cell that specifically dissolve and / or oxidize copper at the anode into copper ions. These ions pass through the separator and are deposited as metallic copper at the cathode. This deposition process forms dendrites, which, after the aforementioned time, grow through the electrically insulating separator and permanently short-circuit the cell internally, as copper is a very good electrical conductor. The cell cannot recover from this short circuit, and thus any remaining electrochemical energy is dissipated internally over time, ultimately resulting in a voltage of 0 V. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2014 207 239 A1

[0003] US 5,656,915 A

[0004] WO 2023 / 228 178 A1

[0006]

Claims

[1] Method for electrically deactivating a battery unit (12) with at least one battery cell (14), wherein the battery unit (12) is discharged, characterized by , that the battery unit (12) is discharged to a negative state of charge by externally imposing a certain discharge current (I2) while reversing a polarity assigned to the battery unit (12) at least until a certain voltage drop (30) of an amount of a voltage (U, U2) of the battery unit (12) occurs. [2] Method according to claim 1, characterized by , that the battery unit (12) is discharged to the negative state of charge (SOC2) for a predetermined period of time and / or until it is detected that the voltage (U, U2) of the battery unit (12) meets a certain time-course criterion, which at least includes that the certain voltage drop (30) has occurred. [3] Method according to any one of the preceding claims, characterized by, that the battery unit (12) is discharged in a first discharge phase (Z1) to a first state of charge (SOC1) or a first voltage value (U, U1) without imposing the discharge current (I2), and when the first state of charge (SOC2) or the first voltage value is reached, in a second discharge phase (Z2) the battery unit (12) is discharged to the second negative state of charge (SOC2) by reversing its polarity through external imposition of a specific discharge current (I2), in particular by applying an external counter-voltage (26). [4] Method according to any one of the preceding claims, characterized by , that the first state of charge (SOC1) is reached when the voltage (U, U1) of the battery unit (12) is a value in the range between 0% and 5% including e.g., essentially 1% of the nominal voltage of the battery unit (12). [5] Method according to any one of the preceding claims, characterized by, that the discharge current (I2) during the first discharge phase (Z1) is limited to a certain first maximum value, which in particular corresponds to a C-rate of 0.7 C. [6] Method according to any one of the preceding claims, characterized by , that in the second discharge phase (Z2) the discharge current (I2) is limited to a certain second maximum value, which is in particular smaller than the first maximum value. [7] Method according to any one of the preceding claims, characterized by , that the discharge current (I2) in the second discharge phase (Z2) is essentially equivalent to a C-rate of 0.25 C, and in particular is essentially constant. [8] Method according to any one of the preceding claims, characterized by, that the magnitude of the counter-voltage (26) is limited to a maximum amount which is determined depending on the number of battery cells (14) connected in series or cell groups of parallel connected battery cells (14) comprising the battery unit (12). [9] Method according to any one of the preceding claims, characterized by , that the battery unit (12) comprises several battery cells (14) connected in series. [10] Deactivation arrangement (10) for electrically deactivating a battery unit (12) with at least one battery cell (14), wherein the deactivation arrangement (10) comprises a discharge unit (20; 23, 26, 24, S1, S2; 22) designed to discharge the battery unit (12), characterized by, that the discharge unit (20; 23, 26, 24, S1, S2; 22) is designed to discharge the battery unit (12) by externally imposing a certain discharge current (I2) to a negative state of charge (SOC2) at least until a certain voltage drop (30) of an amount of a voltage (U, U2) of the battery unit (12) occurs.

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