DE102020126742A1 - Battery module with lithium metal anode - Google Patents

Abstract

The invention relates to a battery module with a cell module housing and an anode made of lithium metal, in which an active agent cartridge is arranged in the cell module housing, the active agent cartridge being filled with a medium and being designed such that when a predetermined temperature is reached in the battery module, the medium is released and has an inhibiting effect on the reactivity of liquid lithium in the cell module housing. Furthermore, the invention relates to an electric vehicle containing such battery modules.

Description

The invention relates to a battery module with a lithium metal anode.

The range of battery electric vehicles is directly related to the energy density of the batteries used. Battery modules with lithium metal as an anode developed in recent years achieve energy densities of up to 450 Wh/kg and thus a value that is significantly higher than the energy density of the most powerful lithium-ion batteries used for electric vehicles to date, whose energy density typically does not exceed 260 Wh/kg lies.

Since lithium metal has high chemical reactivity and melts at a relatively low temperature of about 180°C, it is necessary to improve the safety of a lithium metal anode type battery by taking additional precautions. Careful design of the battery modules, such as the use of additives in the electrolyte or the use of solid electrolytes, can enable stable operation of such battery modules up to temperatures of 200°C without causing a so-called "thermal runaway" (thermal runaway due to an accelerating exothermic chemical reaction) occurs. However, such operating temperatures at which the lithium becomes liquid can cause other problems. At temperatures above 180°C, molten lithium metal can escape from the cell module housing. In battery modules for electric vehicles, so-called pouch housings are usually used for the cell module housing, which are made of aluminum to reduce weight. Such pouch housings made of flexible aluminum foil can leak or even open completely at the high temperatures in battery operation due to liquid lithium. The liquid and chemically highly reactive lithium metal that escapes can cause serious problems, ranging from corrosion of the metal parts in the entire battery system and external short circuits to more extensive damage to the entire vehicle.

Therefore, it is necessary to prevent leakage of the liquid lithium metal from the battery module and its effects.

From the German Offenlegungsschrift DE 10 2018 007 664 A1 For example, a lithium-ion battery is known in which there is at least one cavity which is formed in the battery housing between the battery modules and is at least partially filled with at least one filling element. This filling element is filled with an inert gas and/or protective gas. The volume of oxygen in the air is thus reduced in this battery, which reduces oxidative corrosion in the battery and thus the risk of short circuits. In the event of a fire, the inert gas and/or protective gas can be released, displacing any oxygen that may be present and thus extinguishing the fire. Since the filling elements with the inert gas and/or protective gas are located between the battery modules, such a safety mechanism, due to the design, cannot limit a problem occurring in a battery module to the individual battery module concerned. It is also not suitable for preventing the liquid lithium metal from escaping from the cell module housing in battery modules with lithium metal anodes.

The object of the present invention is therefore to avoid or at least reduce the problems caused by the escape of liquid lithium metal.

This object is achieved by the battery model according to the invention with a lithium metal anode according to claim 1 and the electric vehicle according to claim 10.

According to a first aspect, the invention provides a battery module with a cell module housing and an anode made of lithium metal, in which an active agent cartridge is arranged in the cell module housing, the active agent cartridge being filled with a medium and being designed such that when a predetermined Temperature in the battery module, the medium is released and has an inhibiting effect on the reactivity of liquid lithium in the cell module housing.

According to a second aspect, the invention relates to an electric vehicle with battery modules according to the invention.

A battery module according to the invention with a lithium metal anode comprises: a cell module housing, the cell pack, which in turn contains the lithium metal anode, among other things, an active agent cartridge arranged in the cell module housing outside of the cell pack, and a medium with which the active agent cartridge is filled. When a predetermined temperature in the battery module is reached or exceeded, the active agent cartridge is triggered and the medium is ejected from the active agent cartridge and released into the cell module housing. In particular, the temperature at which the medium emerges from the active agent cartridge into the cell module housing can be 180° C.—the melting point of lithium.

The medium is chemically composed in such a way that the reactivity of the liquid lithium is reduced. A spill of liquid lithium from the cell module housing is prevented by in-situ solidification. In a first embodiment, most of the medium is released near the anode area of the cell pack. However, it is also possible for the medium to be distributed in other partial areas or in the entire area in the interior of the battery module that is not occupied by the cell stack.

In the embodiment of the battery module with lithium metal anode according to the invention, the damage caused by overheating of the battery module or by opening the cell module housing in some other way can be limited to the affected battery modules by escaping liquid lithium metal. If suitable electronics are used, the voltage drop in the battery remains minimal and the battery continues to function. The then necessary replacement of only one battery module is significantly more cost-effective than replacing all or large parts of the battery assembly, which could be irreparably damaged if the highly reactive, liquid lithium escapes from the affected battery module.

Another advantage is that the entire device, including the active agent cartridge filled with the medium, a temperature sensor and control via a module controller, can be easily and inexpensively integrated into the cell module housing.

Further advantageous refinements of the invention result from the dependent claims and the following description of preferred exemplary embodiments of the present invention.

There are versions in which the released medium comes into contact with the liquid lithium. As a result, a fast chemical replacement reaction takes place between the medium or components of the medium and the liquid lithium. This replacement reaction should be so fast that the liquid lithium is prevented from escaping from the cell module housing. Furthermore, the additional amount of heat generated in the replacement reaction, which typically takes place exothermically, should be limited in order to keep further heating caused by the reaction within acceptable limits.

There are versions in which the reaction product formed in the replacement reaction from the medium and the liquid lithium is in the form of a solid in order to enclose any remaining liquid lithium as completely as possible. The aim is either a rapid in-situ solidification of all material within the battery module or a rapid tight confinement of any remaining liquid lithium and a resulting avoidance of any material escaping, and in particular the leakage of the liquid lithium from the battery module cell module housing.

There are designs in which the reaction product formed during the replacement reaction from the medium and the liquid lithium is electrically insulating in order to prevent an internal short circuit between the anode and the cathode and a resulting further heating of the battery module.

In one embodiment of the invention, the active agent cartridge is attached to the inside of the cover of the battery module. This attachment of the active agent cartridge to the cell module housing above the cell pack means that the contact between the medium and liquid lithium is brought about not only by diffusion but also convectively with the help of gravity and is thus accelerated.

There are designs in which the release of the medium from the active agent cartridge can be triggered by means of a pressure sensor on the basis of the detection of a pressure change in the battery module that exceeds a predetermined value. On the one hand, this can be a characteristic increase in pressure brought about by the overheating and, on the other hand, a rapidly occurring pressure drop to the external pressure caused by the opening of the cell module housing. In the latter case, the medium would also be released if the cell module housing were opened from the outside, for example as a result of an accident.

Furthermore, an embodiment is possible in which a release of the medium is triggered both by reaching a predetermined temperature and by detecting a pressure change in the battery module that exceeds a predetermined value.

There are designs in which active ingredients which are gaseous, liquid or powdery are used as the medium which brings about in situ solidification of the liquid lithium. Depending on the form of the medium, the functioning of the active agent cartridge and thus the release process from the active agent cartridge is adapted to the properties of the active agent used in each case. For example, a gaseous substance can be ejected from the active agent cartridge under high pressure, and a liquid or powder can be sprayed. A corresponding optimization of the release process takes place both with regard to the speed of the release process also on efficient distribution of the active ingredient in the desired area of the battery module.

Although lithium is the least chemically reactive of the alkali metals, it reacts very strongly with many other substances. Accordingly, many different active ingredients are possible. Examples are nitrogen N ₂ , iodine I 2 , ammonia NH ₃ , carbon dioxide CO ₂ , oxygen O ₂ , carbon C, aluminum Al, mercury Hg, ethanol C ₂ H ₅ OH or methanol CH ₃ OH. Lithium is the only alkali metal that forms a nitride (Li ₃ N) in a reaction with nitrogen gas, and accordingly the stoichiometric ratio in the reaction product of lithium and nitrogen is advantageous. In particular, it is advantageous if the active ingredient contains a larger proportion of nitrogen N ₂ , carbon C or aluminum Al, since these substances release a significantly lower amount of heat in the replacement reaction with lithium than many other substances.

In alternative exemplary embodiments, a plurality of active agent cartridges can each be attached to one of the inner sides of the cell module housing. In particular, a more efficient distribution of the medium in terms of filling the cavities of the battery module or the anode area of the battery module with the active agent as quickly and as homogeneously as possible can be achieved.

There are versions in which the active agent cartridge contains the medium, a propellant charge and a folded airbag. When the active agent cartridge is triggered, the airbag is unfolded into the cavity provided in order to achieve efficient distribution of the active agent. In further exemplary embodiments, several airbags can each be attached to one of the inner sides of the cell module housing in order to make the distribution of the active substance even more efficient.

An electric vehicle with a battery with the inventive design of the battery modules with lithium metal anodes combines the advantages of the high energy density of the battery and the associated significantly increased range of the electric vehicle with the same battery weight with the safety standard of previously used battery technologies.

• 1 eine schematische perspektivische Darstellung eines (ersten) Ausführungsbeispiels eines erfindungsgemäßen Batteriemoduls;
• 2 eine Ansicht von oben (Draufsicht) des Batteriemoduls gemäß 1;
• 3 eine Stirnansicht des in 1 und 2 dargestellten Batteriemoduls;
• 4 eine Stirnansicht eines alternativen Ausführungsbeispiels eines Batteriemoduls, bei der die Wirkmittelpatrone mit einer Airbaganordnung gekoppelt ist;
• 5 eine Stirnansicht eines weiteren Ausführungsbeispiels eines Batteriemoduls, bei der sich der Airbag im Deckelbereich oberhalb des Zellpakets entfaltet;
• 6A bis 6D Stirnansichten für vier Ausführungsbeispiele eines Batteriemoduls, bei der sich der Airbag bzw. die Airbags an verschiedenen Innenseiten des Batteriemoduls entfalten;
• 6E eine perspektivische Ansicht des Batteriemoduls gemäß 6D;
• 7 eine schematische Seitenansicht des Elektrofahrzeugs mit einer Batterie, die aus den erfindungsgemäßen Batteriemodulen besteht.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. It shows:

• 1 a schematic perspective view of a (first) embodiment of a battery module according to the invention;
• 2 FIG. 12 is a top view (plan view) of the battery module according to FIG 1 ;
• 3 an end view of the in 1 and 2 battery module shown;
• 4 an end view of an alternative embodiment of a battery module, in which the active agent cartridge is coupled to an airbag assembly;
• 5 a front view of a further embodiment of a battery module, in which the airbag unfolds in the cover area above the cell stack;
• 6A until 6D Front views for four exemplary embodiments of a battery module in which the airbag or airbags unfold on different insides of the battery module;
• 6E a perspective view of the battery module according to FIG 6D ;
• 7 a schematic side view of the electric vehicle with a battery, which consists of the battery modules according to the invention.

In 1 the shape of a first exemplary embodiment of the battery module 1 with a cell module housing 2 is shown schematically. The essentially cuboid cell module housing 2 is suitable for a space-saving arrangement of the battery modules 1 in a battery arrangement 10 (cf. 7 ). The upper part of the cell module housing 2 is formed by a module cover 21 and the lower part of the cell module housing 2 by a module base 22. A cell pack 5 is arranged in the cell module housing 2 in such a way that cavities 11 remain between the module cover 21 and the cell module housing insides on the one hand and the cell pack 5 on the other hand. In the area of the upper cavity 11, an active agent cartridge 3 is arranged, which can accommodate the active agent.

In 2 is the arrangement of the active agent cartridge 3 for the first embodiment 1 shown in the top view of the module cover 21. The active agent cartridge 3 is attached to the inside of the module cover 21 close to a corner of the module cover 21 .

This first embodiment is in the 3 shown in a front view of the battery module 1. The active agent cartridge 3 is filled with a medium 4, which serves as an active agent. The chemical composition of the medium 4 is such that a reduction in the reactivity of the liquid lithium is achieved. When the temperature in the battery module 1 has reached or exceeded the value of 180° C., the medium 4 is released from the active agent cartridge 3 into a receiving space 11 .

The active agent cartridge 3 can, for. B. contain a propellant that is under pressure and is ejected by an exit mechanism that is activated when the temperature is exceeded, thereby distributing the medium 4 . A highly reactive ignition means can also be used, which is ignited when the limit temperature is exceeded and the medium 4 is suddenly discharged in order to wet the liquid lithium. The exit of the medium 4 can also be pressure-induced (pressure increase, pressure drop) or acceleration-dependent (impact on the battery 10) in order to bring the medium 4 to the lithium.

In the first exemplary embodiment, the medium 4 is largely released in an anode area 51 of the cell stack 5 . However, it is also possible for the medium 4 to be distributed throughout the portion of the interior of the battery module 1 not occupied by the cell stack 5 - i.e. throughout the receiving space 11.

The release of the medium 4 brings about a rapid replacement reaction by means of contact between the medium 4 and the liquid lithium. In this case, the reaction must not supply the battery module 1 with any additional large amount of heat, in order to keep any further heating of the battery module 1 that takes place as a result within acceptable limits.

The reaction product formed during the replacement reaction is in the form of a solid in order to enclose the remaining liquid lithium as completely as possible, or the aim is a rapid in-situ solidification of the entire material within the battery module 1. This prevents the reaction product from escaping, and in particular the leakage of the liquid lithium, from the cell module housing 2 prevented.

The reaction product formed in the replacement reaction can be electrically insulating in order to avoid a short circuit.

As an alternative to triggering the direct release of the medium 4 from the active agent cartridge 3 when a predetermined temperature is reached or exceeded, the triggering can be based on the detection of a pressure change in the battery module 1 by means of a pressure sensor (not shown).

Substances that are gaseous, liquid or powdered are suitable as medium 4 for reducing the reactivity of the liquid lithium. Depending on the form of the medium 4, the release process is adapted to the properties of the substance used in each case. For example, a gaseous substance can be ejected from the active agent cartridge 3 under high pressure, or a liquid or a powder as in 3 be sprayed shown.

In alternative exemplary embodiments, a plurality of active agent cartridges 3 can each be attached to one of the insides of the cell module housing 2 . In particular, a more efficient distribution of the medium 4 in terms of filling the cavities 11 of the battery module 1 or the anode area 51 of the battery module 1 with the active agent as quickly and as homogeneously as possible can be achieved.

In the embodiment according to 4 an airbag 31 is used to achieve efficient distribution of the medium 4. When the predetermined temperature is reached or a pressure change is detected by the pressure sensor, the airbag 31 is unfolded into the cavity 11 provided by the ignited propellant. The medium 4 guided into the airbag 31 with the propellant can thus be guided precisely into the desired area of the accommodation space 11 .

For a targeted supply of the medium 4, the airbag 31 can optionally be provided with outlet openings 32, which guide the medium 4 in a targeted manner into the desired effective area. The material of the airbag 31 can also be designed in such a way that it decomposes when it comes into contact with liquid lithium and the medium 4 can thus react locally and in a targeted manner.

In another embodiment according to 5 the airbag 31 is designed in such a way that it occupies a large part of the area of the inside of the module cover 21 in the unfolded state.

An optimal distribution of the active agent along the surface of the cell stack 5 can thus be achieved.

In 6A until 6D are in addition to the embodiment according to 5 three other embodiments shown. In particular, depending on the design of the cell stack 5, it can prove to be advantageous for the airbag 31 to be attached to the inside of a vertically arranged wall of the cell module housing 2. Extensive coverage of the cell stack 5 is made possible by an arrangement of three airbags 31 resembling an inverted “U”. Complete coverage of the entire cell stack 5 is also possible.

In 6E is the embodiment according to 6D shown in a schematic way in perspective.

The main advantage of an embodiment of the battery module 1 according to the invention Lithium metal anode consists in limiting the damage caused by possible overheating of the battery module 1 or by opening the cell module housing 2 caused in some other way to the affected battery module 1. When using suitable electronics, the voltage drop in the battery remains minimal, and the battery therefore still functional. The then necessary replacement of only one battery module 1 is significantly cheaper than replacing the entire battery.

The entire device, including active agent cartridge 3, airbag 31 if necessary, temperature and pressure sensor, and actuation via a module controller can be easily and inexpensively integrated into cell module housing 2.

In 7 an electric vehicle 70 with a battery arrangement 10 consisting of several battery modules 1 according to the invention is shown. Equipping an electric vehicle 70 with a battery arrangement 10, the battery modules 1 of which are designed with lithium metal anodes according to the invention, offers on the one hand the advantages of the high energy density of the battery, ie the associated significantly increased range of the electric vehicle 70 with the same battery weight or reduced battery weight with the same range, and on the other hand, a level of safety in operation of the battery and thus of the electric vehicle that is comparable to that of previously used battery technologies 70.

Other embodiments that serve the purpose of fast-acting efficient in-situ solidification of the liquid lithium will be apparent to those skilled in the art based on the examples given. In this respect, the application examples given are not to be understood as restrictive.

Reference List

1

battery module

2

cell module housing

3

active agent cartridge

4

medium

5

cell pack

10

battery arrangement

11

recording space, cavities

21

module cover

22

module floor

31

air bag

32

exit port

51

anode area

70

electric vehicle

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018007664 A1 [0005]

Claims (10)

Battery module (1) with a cell module housing (2) and an anode made of lithium metal , characterized in that an active agent cartridge (3) is arranged in the cell module housing (2), the active agent cartridge (3) being filled with a medium (4). and is designed such that when a predetermined temperature is reached in the battery module (1), the medium (4) is released and has an inhibiting effect on the reactivity of liquid lithium in the cell module housing (2). Battery module (1) after claim 1 , wherein a chemical replacement reaction takes place between the released medium (4) and the liquid lithium. Battery module (1) after claim 2 , wherein a reaction product formed in the chemical replacement reaction from the medium (4) and the liquid lithium is solid and electrically insulating. Battery module (1) according to one of the preceding claims, wherein the active agent cartridge (3) is attached to the inside of a cover (21) of the battery module (1). Battery module (1) according to one of the preceding claims, wherein the active agent cartridge (3) is triggered by means of a pressure sensor after detection of a pressure change in the battery module (1). Battery module (1) according to one of the preceding claims, wherein the medium (4) contains a gaseous, liquid or powdered active substance. Battery module (1) after claim 6 , wherein the active substance contains nitrogen N ₂ , carbon C or aluminum Al. Battery module (1) according to one of the preceding claims, wherein a plurality of active agent cartridges (3) are each attached to one of the plurality of inner sides of the cell module housing (2). Battery module (1) according to one of the preceding claims, wherein the medium (4), a propellant charge and a folded airbag (31) are accommodated in the active agent cartridge (3) or in at least one of the several active agent cartridges (3). Electric vehicle (70) with a battery arrangement (10) comprising a plurality of battery modules (1).

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