Battery Packs Architected to End Undesirable Thermal Events

Abstract

A battery pack configured to terminate an undesirable thermal event. The invention relates to a battery pack (105) comprising at least one electrochemical cell (110), wherein the electrochemical cell (110) has an anode (10) and a cathode (20) and an electrolyte material (15) arranged between the anode and the cathode, wherein the battery pack (105) is configured to trigger an endothermic reaction (240) in an active material (10, 15, 20) as a response to an undesirable thermal event (200). The invention also relates to a vehicle and a method for terminating (250) an undesirable thermal event.

Description

Technical Field

[0001] The invention relates to a battery pack, comprising at least one electrochemical cell, wherein the electrochemical cell has an anode and a cathode and an electrolyte material arranged between the anode and the cathode, wherein the battery pack is designed to trigger an endothermic reaction in an active material as a response to an undesirable thermal event. The invention also relates to a vehicle and a method for ending an undesirable thermal event. Background Art

[0002] It is known from the prior art that a battery module can be composed of a plurality of individual battery cells which can be electrically connected to one another in series and / or in parallel.

[0003] In order to operate the battery cells within a preferred temperature range, it is also known for the battery modules to include a cooling system which is intended in particular to ensure that the battery cells do not exceed a predefined temperature.

[0004] If, however, the battery cells exceed the predetermined safety-critical temperature, this can lead to a loss of control of the battery cells known as “thermal runaway” or also known as “propagation”.

[0005] DE 102017206560A1 describes a battery module having at least one battery cell, wherein the battery module also includes an anti-propagation element thermally connected to the battery cell, the anti-propagation element being constructed so that an endothermic process occurring within the anti-propagation element absorbs heat released by the at least one battery cell when the temperature of the at least one battery cell exceeds a specific value.

[0006] US2013 / 0312947 A1 describes a battery management system with a thermally integrated fire protection device, which includes: a housing; a plurality of individual battery cells in the housing; a plurality of cooling channels in the housing within or between the plurality of individual battery cells; a plurality of sensors, which are connected to the individual battery cells in a manner that complies with production technical conditions, wherein the sensors are adapted to detect thermal runaway, which involves one or more battery cells in the plurality of individual battery cells; and a management system, which is adapted to inject coolant into at least one of the plurality of cooling channels when the thermal runaway is detected by one of the plurality of sensors, so that the thermal runaway is quickly eliminated.

[0007] Furthermore, microchannel cooling (WO 2014 / 190180 A1) and the external release of substances that counteract the exothermicity (DE 102012204033 A1) and the release of cooling liquids (US 2010 / 0136391 A1) have been discussed in the prior art to date.

[0008] Shutdown isolators, passive e-fuses or hydrogels cannot be actively controlled. The effect of microchannel cooling or the release of coolant or other substances that counteract the heat release by absorbing thermal energy occurs externally rather than within the battery pack. Summary of the invention

[0009] The object of the present invention is now to provide a battery pack which effectively terminates or even prevents undesirable thermal events.

[0010] This object is achieved by a battery comprising at least one electrochemical cell, wherein the electrochemical cell has an anode and a cathode and an electrolyte material arranged between the anode and the cathode, characterized in that the battery is designed to trigger an endothermic reaction in the active material as a response to an undesirable thermal event.

[0011] In connection with the present invention, the electrochemically functional materials of the battery are referred to as active materials. The electrochemically functional materials are in particular the anode, the electrolyte material and the cathode.

[0012] In conjunction with the present invention, an undesirable thermal event is described as the exceeding of a predefined safety-critical temperature in at least one battery cell and the resulting runaway in at least one battery cell referred to as “thermal runaway” or “propagation”.

[0013] Unlike the solutions known from the prior art for ending undesirable thermal events, in the case of the present invention, the endothermic reaction is triggered directly in the active material. In other words, the location of the endothermic reaction is the location of the heat generation or heat transfer. This allows heat to be dissipated particularly efficiently. No expensive additional devices outside or inside the battery are required.

[0014] The principles of the present invention can be summarized as follows:

[0015] Electrically or electronically controllable devices in lithium-ion batteries push substances into the active material of the battery in response to a signal, thereby triggering an endothermic chemical reaction that is intended to prevent or delay or mitigate thermal runaway in the battery.

[0016] As already described, in connection with the present invention, the active material is the electrochemical functional material of the battery. According to one embodiment of the invention, the active material also includes the electrode material. The active material is in particular the anode, the electrolyte material and the cathode. The endothermic reaction is not limited to the electrolyte material but also includes the anode and the cathode, which has the advantage that the heat release in the case of undesirable thermal events is reduced by the endothermic reaction in the entire battery.

[0017] On the other hand, when introducing substances into the electrode material, damage to the electrode cannot be completely ruled out. Therefore, according to another preferred embodiment, the active material is only an electrolyte. In this embodiment, the endothermic reaction does not take place in the electrode material, that is, the anode or cathode. This has the advantage that the functionally particularly important electrode is freed from the introduction of substances required for the endothermic reaction.

[0018] An embodiment is also described in which the reactants of the endothermic reaction are already substantially present in the active material and can react as a response to an undesirable thermal event. That is, in this embodiment, it is sufficient to introduce only a single reactant or even only an initiator or catalyst that triggers the endothermic reaction, such as injecting it into the battery. That is, the other reactants required for the reaction are already present in the battery. Preferably, that is, in this embodiment, the reactants of the endothermic reaction are already distributed and / or embedded in the active material. This has the advantage that the amount of reactants that must be introduced into the active material in the case of an undesirable thermal event is limited. Thereby, compared to the embodiment in which all reactants must be introduced into the active material as a response to an undesirable thermal event, it is possible to react faster to an undesirable thermal event as a whole.

[0019] An embodiment is also described in which the reactant of the endothermic reaction is not present in the active material but is introduced, for example injected, into the active material as a response to an undesirable thermal event. If the reactant of the endothermic reaction is introduced into the active material as a response to an undesirable thermal event, the reactant does not have to be already present in the active material of the battery. If the reactant is already present in the active material of the battery, this may lead to a hindrance to the equilibrium conditions of the battery. There is also the risk that the reaction is triggered prematurely by mistake even if there is no undesirable thermal event at all.

[0020] A preferred embodiment is also described wherein at least one reactant for an endothermic reaction is stored in a reservoir, from which reactant is introduced into the active material in response to an undesirable thermal event.

[0021] Since at least one reactant of the endothermic reaction is stored in a reservoir, the reactant is introduced from the reservoir into the active material in the event of a desired thermal event not being met, the reactants can be replenished after consumption and the reactants can be selected individually as required.

[0022] A preferred embodiment is also described in which the introduction of the reactants into the active material of the cell is controlled by means of a control device.

[0023] A preferred embodiment is also described in which the reservoir is mounted on or in the housing of the electrochemical cell.

[0024] Since the reservoir is mounted on or in the housing of the electrochemical cell, at least one reactant for the endothermic reaction can be introduced directly into the active material of the cell.

[0025] A preferred embodiment is also described wherein the endothermic reaction is an oligomerization or polycondensation reaction.

[0026] In connection with the present invention, the reaction in which monomers are combined to form macromolecules is referred to as polycondensation, wherein these monomers carry at least two reactive functional groups. In the case of this reaction, for example simple, low molecular weight reaction byproducts such as water, alcohol, ammonia are separated.

[0027] A preferred embodiment is also described wherein the endothermic reaction is an oligomerization or polycondensation of silicon-based monomers.

[0028] According to a further preferred embodiment, the endothermic reaction is an oligomerization or polycondensation of silicon-based monomers, for example to form silicone resins.

[0029] According to a further preferred embodiment, the endothermic reaction can be carried out in an aprotic medium and is therefore compatible with conditions such as those prevailing in the cells of a battery.

[0030] A preferred condensation reaction is, for example, the reaction of the following monomers:

[0031] RX-SiR”R”’-XR’.

[0032] R, R', R", R'" are selected independently of one another and are preferably organic radicals, further preferably alkyl and / or alkenyl radicals, and in particular -CH3 and / or -C2H5 and / or -C6H5.

[0033] As a result of this reaction, oligomers or polymers with different bonds are obtained, depending on the reaction conditions.

[0034] In this context, "selected independently of one another" means that different groups can be respectively present for R, R', R", and R'"'. Furthermore, for example, a certain group on one monomer can also be selected differently from a group of the same name on another monomer. In other words, heterochain polymers are also conceivable, which are obtained by reacting a first monomer according to one of the above structures with a second (further) monomer according to one of the above structures or, if appropriate, also further (additional) monomers.

[0035] X is preferably an optionally substituted heteroatom, in particular O, S, NR*, PR*. What has been described for the substituents R, R', R", R'" applies to the radical R* as a substituent.

[0036] R, R', R", R'" are preferably organic groups, further preferably alkyl and / or alkenyl groups, and especially -CH3 and / or -C2H5 and / or -C6H5.

[0037] In particular, the polycondensation reaction may have the following form:

[0038] n / 2R'X-SiR2-XR'+n / 2R”(Y)-SiR”’2-(Y)R”--->R’X-SiR2-[(Y-)SiR”’2-(Y-)SiR2-]n-XR’+n R’X-(Y)R”.

[0039] R, R', R", R'" are preferably organic groups, further preferably alkyl and / or alkenyl groups, and especially -CH3 and / or -C2H5 and / or -C6H5.

[0040] X is preferably an optionally substituted heteroatom, in particular O, S, NR*, PR*. What has been described for the substituents R, R', R", R'" applies to the radical R* as a substituent.

[0041] Y is preferably an optionally substituted heteroatom, in particular O, S, NR*, PR*. What has been described for the substituents R, R', R", R'" applies to the radical R* as a substituent.

[0042] A preferred embodiment is also described in which the battery is a lithium-ion battery.

[0043] Lithium-ion battery is a general term for batteries based on lithium compounds in all three phases of the electrochemical cell.

[0044] Compared to other battery types, lithium-ion batteries have a higher specific energy and are also used, in particular, in vehicles with hybrid drives.

[0045] Preferably, the following embodiments can be used as active material, i.e. as anode, cathode or electrolyte. The list is not closed:

[0046] The material of the negative electrode (in discharge: anode; in charge: cathode) is preferably:

[0047] - Graphite and similar carbons, in which lithium intercalation occurs, remain the most important materials

[0048] - Also: Nanocrystalline amorphous silicon (alloyed with lithium)

[0049] -Also: lithium titanate such as Li4Ti5O12 (used in lithium titanate batteries)

[0050] -Tin dioxide (SnO2)

[0051] The following materials are preferably used as electrolytes:

[0052] - a salt such as lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4) or lithium bis(oxalato)borate (LiBOB), dissolved in an anhydrous aprotic solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate or 1,2-dimethoxyethane

[0053] - polymers in lithium-polymer batteries, the polymers consisting of polyvinylidene fluoride (PVDF) or polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP)

[0054] -Lithium phosphate nitride (Li3PO4N)

[0055] The positive electrode (cathode during discharge and anode during charge) is:

[0056] - Lithium cobalt(III) oxide (LiCoO2) and similar layered compounds

[0057] - lithium nickel cobalt manganese oxides, such as LiNi0.33Co0.33Mn0.33O2, which are mixed oxides of the mentioned LiCoO2, of LiNiO2 and LiMnO2; a manganese-free variant is the oxide LiNi1-xCoxO2

[0058] - Lithium nickel cobalt aluminate ("NCA", LiNiCoAlO2), for example LiNi0.85Co0.1Al0.05O2

[0059] - Spinel, such as LiMn2O4

[0060] -Lithium iron phosphate (LiFePO4) in lithium iron phosphate batteries

[0061] The diaphragm is:

[0062] -Polyolefin film

[0063] -Polyolefin membrane with nano-ceramic layer

[0064] -High purity alumina (HPA) diaphragm.

[0065] A preferred embodiment is also described in which the endothermic reaction is triggered by means of a control unit.

[0066] According to another aspect, a method is also described, wherein the method comprises the steps of:

[0067] -Detect unexpected thermal events;

[0068] -Injection of reactants for endothermic reaction.

[0069] According to a further aspect, a motor vehicle is described which comprises a battery pack according to the invention.

[0070] Further preferred embodiments of the invention result from the remaining features mentioned below.

[0071] Unless otherwise indicated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The present invention is then described in an exemplary embodiment with reference to the accompanying drawings.

[0073] Figure 1 A battery including an electrochemical cell according to the present invention is shown;

[0074] Figure 2 An electrochemical cell of a lithium-ion battery is shown;

[0075] Figure 3 Method steps for ending an undesirable thermal event are shown;

[0076] Figure 4 A system including a battery pack having an electrochemical cell according to the present invention is shown; and

[0077] Figure 5 A system including a battery having a plurality of electrochemical cells according to the present invention is shown. DETAILED DESCRIPTION

[0078] Figure 1A battery 105 according to the invention is shown, comprising an electrochemical cell 110. The electrochemical cell 110 has an anode 10 and a cathode 20 and an electrolyte material 15 arranged between the anode and the cathode. The battery 105 is configured to trigger an endothermic reaction in the active materials 10, 15, 20, i.e. in the anode 10 and / or the cathode 20 and / or in the electrolyte material 15 arranged between the anode and the cathode, as a response to an undesirable thermal event.

[0079] For this purpose, at least one reactant of the endothermic reaction 240 is introduced into the active material 10, 15, 20. For this purpose, at least one reactant of the endothermic reaction 240 is stored in a reservoir 40. The reservoir 40 is mounted on or in the housing of the electrochemical cell 110. This ensures that the reservoir is close to the site of action. The at least one reactant is injected by means of a nozzle 50. The injection is controlled by a control unit 30.

[0080] The endothermic reaction is preferably a polycondensation reaction. Due to the negative reaction enthalpy, the heat transferred by the undesirable thermal event is neutralized and thereby the undesirable thermal event ends.

[0081] Figure 2 An electrochemical cell 110 of a lithium-ion battery is shown. The electrochemical cell 110 has an anode 10 and a cathode 20 and an electrolyte material 15 arranged between the anode and the cathode. The anode material 10 is graphite, into which lithium can be embedded. The cathode material 20 is lithium cobalt (III) oxide (LiCoO2). Similar layered compounds can also be used. During discharge, lithium is oxidized at the anode 10 and migrates to the cathode 20 through the electrolyte material 15. During charging, the opposite process occurs. The battery pack 105 is constructed to trigger an endothermic reaction in the active materials 10, 15, 20, i.e. in the anode 10 and / or the cathode 20 and / or in the electrolyte material 15 arranged between the anode and the cathode, as a response to an undesirable thermal event. To this end, the required reactants are injected into the electrolyte material 15, as illustrated by the arrows.

[0082] Figure 3 The method steps for ending an undesirable thermal event are shown. First, an undesirable thermal event 200 occurs. An undesirable thermal event can be, in particular, an exceeding of a predefined safety-critical temperature in at least one battery cell. Such an event is "undesirable" because it can result in a loss of control of the battery cell, which is referred to as "thermal runaway" or "propagation".

[0083] The undesirable thermal event is detected 220 by means of a suitable measuring device. The measuring device or measuring device checks different operating parameters such as voltage, current intensity and / or temperature (U, I and / or T) during the operation of the battery pack. These operating parameters U, I and T are used to detect the presence of a thermal event. In particular, a temperature measuring device can directly detect a thermal event.

[0084] However, the detection 220 of the undesirable thermal event does not necessarily require that the thermal event has occurred. In some cases, it may be possible to infer with sufficient confidence from the ascertained parameters that an undesirable thermal event will occur. For example, irregularities in the current and / or voltage characteristic curves may indicate that an undesirable thermal event will occur. Large spatial or temporal temperature gradients may also indicate that an undesirable thermal event will occur.

[0085] If it has now been detected that the undesirable thermal event has occurred or will occur with sufficient certainty, a reactant is injected 230 into the active material of the cell or cells. An endothermic reaction 240 neutralizes the heat energy generated or already generated due to the thermal event. Thus, the thermal event is prevented 250.

[0086] If the undesirable thermal event has occurred, a reactant is injected 230 into the active material of the cell or cells as a countermeasure. Thus, after the cell temperature has exceeded a safety-critical temperature limit value in at least one battery cell, the cell temperature can be reduced back below the limit value, for example.

[0087] If in another case the undesirable thermal event has not yet occurred, but there is sufficient certainty that it will occur, the reactant is injected 230 into the active material of the cell or cells as a precautionary measure. Thus, for example, a predetermined safety-critical temperature in at least one battery cell can be prevented from being substantially exceeded.

[0088] Figure 4A system according to an embodiment of the present invention is shown. The system comprises a charging device 100, by means of which a battery pack 105 can be charged. The battery pack comprises an electrochemical cell 110. A measuring device is also provided. In particular, the battery pack voltage can be measured by means of a voltage measuring device 111. A current measuring device 112 allows the current current to be measured. A temperature measuring device 113 is also provided to monitor the temperature. The information detected by these measuring devices 111, 112, 113 is transmitted to a control device 120. These measuring devices check the operating parameters U, I and T during the operation of the battery pack. These operating parameters U, I and T can be used to detect the presence of thermal events. In particular, the temperature measuring device 113 can directly detect thermal events. However, irregularities in the current and / or voltage characteristic curves can also be used to infer the presence of thermal events that do not meet expectations. Preferably, all the information in the operating parameters U, I and T is used to detect thermal events that do not meet expectations as early as possible and with sufficient confidence. The vehicle driver may be informed via an output unit, preferably a screen or display 130, that an unexpected thermal event has occurred and may be requested to perform a check of the battery pack, for example to update the reactant inventory.

[0089] Figure 5 A system according to another embodiment of the present invention is shown. The system comprises a charging device 100, by means of which a battery pack 105 can be charged. The battery pack comprises a plurality of electrochemical cells 110a, 110b, 110c. A measuring device is also provided in each of these cells. In this way, the battery pack voltage can be measured by means of a voltage measuring device 111. The information detected by these measuring devices 111, 112, 113 for each of the cells 110a, 110b and 110c is transmitted to a control device 120. These measuring devices check operating parameters U, I and T for each of the cells 110a, 110b, 110c during the operation of the battery pack. These operating parameters U, I and T can be used to detect the presence of a thermal event for each of the cells 110a, 110b, 110c. In particular, the temperature measuring device 113 can directly detect a thermal event. However, irregularities in the current and / or voltage characteristic curves can also be used to infer the presence of an undesirable thermal event. Preferably, all information from the operating parameters U, I and T is used in order to detect undesirable thermal events as early as possible and with sufficient confidence.

[0090] Reference numerals list

[0091] 10 Anode

[0092] 15 Electrolyte Materials

[0093] 20 Cathode

[0094] 30 Electronic Control Unit

[0095] 40 Storage

[0096] 50 Nozzle

[0097] 100 Charging equipment

[0098] 105 Battery Pack

[0099] 110 electrochemical cell (110a, 110b, 110c)

[0100] 111 Voltage measuring equipment

[0101] 112 Current measuring equipment

[0102] 113 Temperature measuring equipment

[0103] 120 Control device / control equipment / control unit

[0104] 130 Screen

[0105] 200 Unexpected thermal event occurred

[0106] 220 Unexpected thermal event detected

[0107] 230 Injection of reactants

[0108] 240 Endothermic reaction

[0109] 250 Prevent unexpected thermal events.

Claims

1. A battery pack (105), comprising at least one electrochemical cell (110, 110a, 110b, 110c), wherein the electrochemical cell (110, 110a, 110b, 110c) has an anode (10) and a cathode (20) and an electrolyte material (15) arranged between the anode and the cathode, characterized in that: The battery pack (105) is configured to: trigger an endothermic reaction (240) in the active material (10, 15, 20) in response to an undesirable thermal event (200), wherein at least one reactant of the endothermic reaction (240) is introduced into the active material (10, 15, 20) in response to the undesirable thermal event (200), wherein the reactant of the endothermic reaction (240) was not previously present in the active material (10, 15, 20) but was introduced into the active material (10, 15, 20) in response to the undesirable thermal event (200).

2. The battery pack (105) according to claim 1, characterized in that: At least one reactant of the endothermic reaction (240) is stored in a reservoir (40), and in response to the undesirable thermal event (200), the reactant is introduced from the reservoir into the active material (10, 15, 20).

3. The battery pack (105) according to claim 2, characterized in that: The reservoir (40) is mounted on the housing of the electrochemical cell (110, 110a, 110b, 110c) or is mounted in the housing of the electrochemical cell (110, 110a, 110b, 110c).

4. The battery pack (105) according to any one of claims 1 to 3, characterized in that: The endothermic reaction (240) is an oligomerization reaction or a polycondensation reaction.

5. The battery pack (105) according to any one of claims 1 to 3, characterized in that: The endothermic reaction (240) has a positive reaction enthalpy large enough to terminate the undesirable thermal event.

6. The battery pack (105) according to any one of claims 1 to 3, characterized in that: The battery pack (105) is a lithium-ion storage battery.

7. The battery pack (105) according to any one of claims 1 to 3, characterized in that: The endothermic reaction (240) is triggered by means of a control unit (120).

8. A method for ending (250) an undesirable thermal event when using a battery pack (105) according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: - detecting (220) thermal events that are not in accordance with expectations; - Injecting (230) reactants for the endothermic reaction (240).

9. A vehicle comprising a battery pack (105) according to any one of claims 1 to 7.

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