Battery safety system having a controlled gas release function

Abstract

The invention relates to a battery safety system (10) for controlled, active gas release. The battery safety system (10) for controlled gas release in the case of aging, leakage or an accident has a sorption element (15) for absorbing the chemical compounds that arise during the gas release, and has a sensor or indicator for monitoring the saturation of the sorption element (15). The invention also relates to the use of a sensor or indicator for monitoring the saturation of sorption elements (15) in battery systems (10), and to the use of the battery safety system (10) according to the invention in battery-powered transport means, household appliances or large-scale electrochemical storage plants.

Description

[0001] Description

[0002] Safety battery system with controlled degassing function

[0003] The invention relates to a safety battery system for controlled and active degassing. The safety of batteries during charging, discharging, aging, leakage, thermal stress, mechanical damage, or in the event of an accident plays a major role in many areas, for example, in traffic.

[0004] With the advancement of electromobility, the demands on automotive batteries have become significantly higher. Improvements in cell chemistry have significantly increased cell performance in terms of energy density, power density, safety, and lifetime over the past ten years. One of the greatest challenges is improving cell safety so that, in the event of an undesirable event, no significant damage occurs or there is no danger to passengers or the environment. Various measures are being sought to help prevent a chain reaction and thermal propagation, thus guaranteeing safety and robustness.

[0005] It is well known that thermal burnout can occur in a cell in a battery system. This can trigger a chain reaction and ignite other cells. This can compromise the entire battery system of a vehicle or means of transport, or a static storage system. The resulting gases can cause serious fires. A problem is that the gas escaping from the individual cell casings initially spreads within the battery system, and this spreading gas can transfer thermal energy to other cells.

[0006] Even with slowly progressing gas formation, the pressure in the cell increases, resulting in swelling that can even lead to plastic deformation of a cell. Furthermore, this battery cell can open, causing gases, vapors, or electrolyte to escape from the battery module or battery system, potentially causing various types of damage. DE 102019 214 755 A1 proposes cooling the battery cells using a cooling circuit. A drying device, for example, using silica gel, silica gel, or zeolite, ensures that little or no moisture can penetrate into the battery housing when pressure equalizes from the inside. Moisture penetration into the battery cells is also prevented in the other direction.

[0007] US 2013 / 0059175 A1 discloses a battery with a venting system featuring a downward-facing vent opening leading into a collection area for the resulting degradation substances. The collection area has a recess for removing the degradation substances. However, in the event of a slow leak from the cell, the gases will remain in the system and accumulate in the collection area, thus not reducing the risk of an explosive reaction.

[0008] DE 10 157 272 C2 describes batteries with a non-flammable sorbent for adsorption and absorption, for example, of organic solvents. The sorbent is located in a region that is in contact with the individual battery cells. It can be used as a granulate or powder, or even as a molded part. Agents for increasing mechanical stability, such as nets or nonwovens made of, for example, glass fiber or PTFE fibrids, have also been described.

[0009] DE 102014 211 043 A1 discloses a lithium cell with foil packaging in a hard-shell cell housing and a fluorine absorber. The fluorine absorber is arranged in the foil packaging and / or the hard-shell cell housing, allowing hydrogen fluoride (HF), fluoride ions, and other fluorine-containing decomposition chemicals to be neutralized or bound close to or directly at their point of origin. HF development is thus also contained directly at the point of origin, particularly within the hard-shell cell housing. The foil packaging can be metal-free and stretchable, so that the penetration of HF into the hard-shell cell housing can be delayed without the need for a vent. The hard-shell cell housing can also have a vent, for example, a safety burst membrane.

[0010] DE 102008 025422 A1 describes an energy storage cell with a safety burst membrane and an absorber attached directly to it. This can be an absorbent mass at the electrolyte leakage point, for example, in the form of dried tablets or a powder. When the safety burst membrane bursts, the escaping electrolyte is immediately absorbed by the absorber.

[0011] DE 102011 087 198 A1 also describes a battery cell with a closed degassing system, with an absorption medium and pressure valve or a design with a volume-variable gas intake chamber to compensate for the pressure increase when gas is formed.

[0012] Monitoring of pressure relief in an enclosed, cell-like cavity by means of a sensor, for example when a cover unit is opened due to pressure being exceeded, is described in DE 202019 106 891 U1.

[0013] The invention is based on the task of improving existing battery systems or battery modules, particularly with regard to safety. The escaping gases or the chemically reactive compounds contained therein, such as H2, CH4, C2H2, and so on, or even gaseous electrolyte components, are to be actively collected and then removed. The changes are intended to enable the broad and safe use of the battery systems for a wide variety of applications.

[0014] The invention relates to a safety battery system with a controlled degassing function in conditions of possible malfunction such as: charging, discharging, aging, leakage in the event of thermal and / or electrical and / or mechanical stress or accident, comprising at least one battery cell with a venting membrane, and a sorption element for absorbing the chemical compounds occurring during degassing, characterized in that a sensor (preferably) or an indicator for monitoring the saturation of the sorption element is included.

[0015] The invention also relates to the use of a sensor or indicator for monitoring the saturation of sorption elements in battery systems, in particular also of sorption elements in the safety battery system according to the invention.

[0016] Furthermore, the invention relates to the use of the safety battery system according to the invention in battery-powered means of transport and household appliances, as well as in large-scale electrochemical storage systems. The term "degassing" within the meaning of the invention also encompasses the release of gases, liquids, or liquid vapors. However, during charging, discharging, aging, leakage due to thermal and / or electrical and / or mechanical stress, or accidents, gaseous compounds are most commonly released.

[0017] It also encompasses the possibility that a battery cell may have one or more venting membranes. The venting membranes can be equipped with or without a burst membrane, meaning continuous venting can occur. The position of the venting membrane is arbitrary. To clarify, the venting membranes contain one or more openings covered by a gas-permeable membrane.

[0018] If necessary, the venting membrane is designed to provide a bursting function.

[0019] With the help of the sorption element, hazardous gases or substances (e.g., CO2, H2, CO, CH4, etc., as well as moisture or electrolyte vapors, as well as escaping liquid components) are bound and can no longer spread uncontrollably within the battery system. In the event of a damaging event, sorption elements can significantly reduce or even neutralize the extent of damage if a sorption element permanently absorbs the high-temperature or highly reactive gases or electrolyte components. Subsequent damage, such as gas ignition and propagation in the event of a thermal runaway throughout the entire battery system, which may include numerous battery cells, can thus be prevented or minimized.

[0020] The invention also succeeds in preventing a slow leak from saturating the sorption element and then going undetected. The invention enables detection of the saturation state using the sensor or indicator according to the invention for monitoring the saturation of the sorption element. If saturation goes undetected, the sorption element would otherwise be ineffective, allowing further gas to spread throughout the battery system, or in the event of a serious accident, controlled absorption by the sorption element would no longer be possible.

[0021] To avoid this risk, the prior art requires the sorption element to be replaced at predetermined, regular intervals or saturation, whichever occurs first. Once removed for inspection, sorption elements can often no longer be used. This proactive replacement is rendered obsolete by the invention, and intact sorption elements no longer need to be disposed of. The advantage is that the operating costs of battery systems are significantly reduced, also due to the labor savings. From an ecological perspective, it is also advantageous that intact sorption elements do not have to be disposed of as part of such a proactive replacement.

[0022] With the help of this invention, gases such as CO2, CO, CH4, C2H6, HF or electrolyte salts such as lithium hexafluorophosphate from the electrolyte, vapors of the electrolyte components (such as ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate), acids and other hazardous media are absorbed by the sorption element.

[0023] The material contained in the sorption element is a non-reactive material that can consist of different elements and compositions and can be introduced in various forms. Examples include granules, pellets, powder, a green compact, a compact, film, or membrane. It is important to create contact with the largest possible surface area between the material of the sorption element and the flowing substances. The shape can be rectangular, circular, oval, square, trapezoidal, or polygonal, for example.

[0024] In a preferred embodiment of the invention, the venting membrane is a vent opening.

[0025] In a preferred embodiment of the invention, the sensor is a resistance sensor, an optical sensor, or a weight sensor. This also includes the possibility that, in the case of multiple sensors, these sensors may use different measurement methods. The advantage of these methods is their good and reliable suitability for indicating the saturation of the sorption element. A resistance sensor detects the changed resistance of the sorption element at saturation; an optical sensor detects the change in extinction or light transmittance; and a weight sensor detects the change in the weight of the sorption element. The sensory or indicator function can also be based on other physical principles.

[0026] In a preferred embodiment of the invention, the sensor or indicator according to the invention is connected to a battery management control unit that can determine and output the saturation of the sorption element based on the data acquired by the sensor. Advantageously, this can indicate the need to replace the sorption element if the determined value exceeds a saturation threshold.

[0027] In a preferred embodiment of the invention, the sorption element is a non-hydrophilic sorption element. This means that the material of the sorption element responsible for absorption or adsorption is non-hydrophilic. The advantage is that it is particularly well suited for absorbing those compounds that most frequently escape from battery cells, such as H2, CH4, C2H6, or organic solvents. The invention particularly preferably serves for the controlled adsorption or absorption of gaseous substances. In a further secondary embodiment, the sorption element has a hybrid composition. The components in the material matrix can also absorb moisture.

[0028] In a preferred embodiment, the venting membrane is arranged on the top side of the battery cell. This corresponds to an arrangement such that the degassing direction during operation of the safety battery system when used (for example, in a passenger car).

[0029] In a preferred variant of the safety battery system according to the invention, a protective space is provided on the venting membrane to protect against contaminants (such as splash water) entering the battery cell. A battery tray, for example, forms the protective space. The advantage is that the protection of the battery cells is increased. However, this embodiment also makes it possible to increase the distance between the sorption element and the battery cell interior, thus allowing the escaping compounds to cool before they are bound by the sorption element.

[0030] In this variant, the sorption element is preferably mounted inside the protective chamber at its outlet (viewed in the direction of degassing). Advantageously, the distance between the battery cell interior and the sorption element is maximized, allowing the compounds released during degassing to cool down as much as possible before binding in the sorption element. The advantage is that this protects the sorption element.

[0031] In another preferred embodiment of this aforementioned variant, the protective space is in the form of a channel, and the sorption element fills the channel across its entire cross-section in the direction of vent flow. This is very useful for controlled degassing, as it results in less mixing of the escaping compounds, for example, as gases. It is advantageous to minimize the mixing of the various gases frequently generated in a battery accident to prevent reactions between them.

[0032] In a likewise preferred embodiment of this aforementioned variant with a protective chamber, a mat is provided on the outside of the venting membrane (i.e., between the battery cell housing and the floor opening of the protective chamber), and the sorption element is integrated into the mat. Advantageously, the mat with an integrated sorption element simultaneously creates a seal between the battery cell housing and the protective chamber (e.g., designed as a battery tray). This is also schematically shown in Fig. 4. The sorption element, which is integrated into the mat, is easy to replace. Consequently, the seal is replaced at the same time, which contributes to a long, reliable service life of the battery system.

[0033] Another preferred embodiment of the safety battery system according to the invention comprises at least two sorption elements located at different positions between groups of battery cells. Such an embodiment is shown in Fig. 3. The advantage here is that one sorption element is not required per battery cell, but the absorption of the compounds formed during degassing is still sufficient. Sorption elements are saved. They can be distributed accordingly. It is even advantageous to choose locations where the probability of leakage is highest, for example, due to impact or heat exposure, etc.

[0034] In a preferred embodiment of the invention, the sorption element has a shape selected from cuboid, rectangular, and cylindrical, and the sorption element is located in a mesh-like support. The advantage of this is that the sorption element is held in place, i.e., stationary, without its surface being unnecessarily obscured and deprived of adsorption or absorption. This is because the absorbable amount of compound(s) is greater than if parts of the sorption element were obscured.

[0035] In another preferred embodiment of the invention, the sorption element has a flat shape and is applied to a membrane (as a mesh-like support). Advantageously, a flow-through cross-section can be provided with a uniformly distributed (because equally thick) sorption element such that even under greater pressure from the resulting compounds, i.e., large quantities, the sorption element withstands and does not lose its shape or break, as it is supported by the membrane preferably located behind it (in the direction of flow). In a preferred embodiment of the invention, the material contained in the sorption element is a material selected from: physical adsorbents, such as: zeolites, silica materials, MOF (metal organic framework), activated carbon, COF (covalent organic framework), carbon molecular sieves, materials based on alkali metals / metal oxides, ordered porous carbon, ACF (activated carbon fibers),Graphene, CMS (carbon molecular sieve) and their composites, chemical adsorbents, such as composite adsorbents prepared by impregnation with K2CO3, binary eutectic mixture (KNO3 and UNO3), NaNOs, Al2O3, ZrO2, TiO2, MnO2, ZnO, ionic liquid (IL), and aqueous amine (i.e., tetraethylenepentamine (TEPA), poly(allylamine) (PAA), poly(ethyleneimine) (PEI), ethylenediamine (EDA), diethylenetriamine (DETA), pentaethylenehexamine (PEHA), aminopropyl (AP), monoethanolamine (MEA), lysine, glycine, proline, alanine, arginine, triethylenetetramine (TETA), and 2-amino-2-methyl-1-propanol (AMP), etc.) in a support-adsorbent matrix.

[0036] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0037] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0038] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. They show:

[0039] Figure 1 shows a battery system according to a first embodiment of the invention in a sectional view;

[0040] Figure 2 shows a battery system according to a second embodiment of the invention in a perspective view;

[0041] Figure 3 shows a battery system according to a third embodiment of the invention in a perspective view;

[0042] Figure 4 shows a battery system according to the third embodiment of the invention in a sectional view; Figures 5a-d show two-dimensional views of different shapes of a sorption element according to the invention;

[0043] Figures 6 and 6a show a battery system according to a fourth embodiment of the invention in two different sectional views; and

[0044] Figure 7 shows an arrangement of a further embodiment.

[0045] It is useful to combine the above-mentioned embodiments.

[0046] Fig. 1 serves to illustrate a first embodiment of a battery system 10 with two battery cells 11 that are arranged directly adjacent to one another, with the view each directed towards a pole side of the cell housing 12. The illustration shows that each battery cell 11 has a vent membrane 13, which in this case is directed downwards, so that the gases, vapors, media, etc. can spread into the protective space 14 (underrun protection space) and then reach the sorption element 15 (here as an adsorber unit), where they can be adsorbed. The sorption element 15 can be moved to any position. In the embodiment of Fig. 1, the sorption element 15 is part of the outlet of the protective space 16 (i.e. the main vent) of the battery system. A mat 18 is shown between the cell housing 12 or its venting membranes 13 and the bottom opening 19 on the battery tray 20.

[0047] Fig. 2 shows, in a second exemplary embodiment, a complete module assembled from several groups of battery systems 21. The groups 21 each consist of twelve battery cells 11. In total, there are 192 battery cells installed in the battery tray 20. The ventilation membranes 13 of the battery cells are oriented downwards, as shown in Fig. 1. On the side of the battery system 10 (see arrow), the main ventilation 16 serves as the exit from the protective space. This ventilation vent 16 contains one or more sorption elements 15 in the underrun protection space as a protective space 14. The protective space 14 can be designed in different ways and distributed across several groups. This allows the sorption element 15 to be installed not only at a central location, but also at any location.The sorption element 15 consists of a material matrix that, when the sorbent material contained therein reaches saturation during adsorption or absorption, indicates, for example, a corresponding change in internal resistance. A signal is transmitted via a supply line 22 (between the sorption element and the battery management control unit) to the BMS (battery management control unit), which indicates that the sorption elements 15 are saturated and need to be replaced.

[0048] Material matrix of the sorption element: these are complex material mixtures that depend on the type of cell chemistry (NMC, LFP, etc.), application, construction, etc. It can be assumed that many of the following material combinations (known from the literature) are possible: physical adsorbents, such as: zeolites, silica materials, MOF (metal organic framework), activated carbon, COF (covalent organic framework) or carbon molecular sieves, materials based on alkali metals / metal oxides, ordered porous carbon, ACF (activated carbon fibers), graphene, CMS (carbon molecular sieve) and their composites, etc. chemical adsorbents: composite adsorbents prepared by impregnation with K2CO3, binary eutectic mixture (KNO3 and LiNO3), NaNO3, AI2O3, ZrO2, TiO2, MnO2, ZnO, ionic liquid (IL), and aqueous amine (i.e., Tetraethylenepentamine (TEPA), Poly(allylamine) (PAA), Poly(ethyleneimine) (PEI), Ethylenediamine (EDA), Diethylenetriamine (DETA), Pentaethylenehexamine (PEHA), Aminopropyl (AP), Monoethanolamine (MEA), Lysine, Glycine, Proline, Alanine, Arginine, Triethylenetetramine (TETA) and 2-Amino-2-methyl-1-propanol (AMP) etc.) into the carrier-adsorbent matrix etc.

[0049] The material matrix can be freely combined from different components, which essentially represents an adsorber compound.

[0050] Fig. 3 shows a third embodiment of the invention for the case where a leak occurs at any cell location and the gases, vapors, etc. from the cell spread uncontrollably between the battery cells 11 in the battery system and cannot find their way down into the protective space 14. They are then discharged directly to the outside. This means that there are no floor openings 19 at the bottom of the battery tray 20. Instead, the protective space is designed as a channel 23, as shown in Fig. 4. In this case, the channel bottom 24 represents a barrier and thus ensures that the dangerous gases, vapors, etc. remain there and cannot cause undesirable damage to the vehicle, its occupants, or the environment. In this embodiment, the sorption element 15 is installed at different positions 15.1 between groups of battery cells 21. The size and shape of the sorption elements 15.1 can be selected as desired.They consist of the same materials as in exemplary embodiment 2. Fig. 5 shows different shapes (2D representation) of the sorption element 15, which is filled with a sorption material / sorbent (pellets and / or powder and / or granules, etc.). The sorption element can have a cuboid shape 15a, a rectangular shape 15b, a cylindrical shape 15c, or a membrane shape 15d. In cuboid, rectangular, and cylindrical shapes, the sorption material of the sorption element is contained in a mesh-like carrier 15.5 as a carrier bag (container), which consists of a permeable mesh. Design d) in Fig. 5 is a flat sorption element 15, which is attached (coated) to a membrane as a mesh-like carrier 15.5. We assume that other design shapes are possible.

[0051] Fig. 6 and 6a show a further embodiment in which the sorption element 15 is integrated in the mat 18 in such a way that it is aligned with the venting membranes 13 of the respective cell 11 of the group of battery cells 19.

[0052] Fig. 6 shows the level of the mat, below the groups of battery cells.

[0053] Fig. 6a shows the underside of the battery cell groups with the venting membranes 13, one level above. Fig. 6a schematically visualizes the interface between the battery cell group 21 and its battery cells 11 and the mat 18. In the embodiment shown, the integrated sorption elements 15 have a rectangular basic shape. However, they can alternatively have any other shape, in particular a circular, oval, square, trapezoidal, polygonal, or other basic shape.

[0054] Fig. 7 schematically shows a sensor or indicator 26 which is connected to the sorption element 15 and which can indicate to the battery management system 25 the saturation of the sorption element 15 and signal a necessary replacement.

[0055] List of reference symbols

[0056] 10 Safety battery system

[0057] 11 battery cells

[0058] 12 battery cell housings

[0059] 13 Venting membrane

[0060] 14 Shelter

[0061] 15 sorption element

[0062] 15.1 Sorption element at different positions

[0063] 15.5 Net-like carrier

[0064] 15a Cuboid shape

[0065] 15b Rectangular shape

[0066] 15c cylindrical shape

[0067] 15d membrane shape

[0068] 16 Exit of the shelter (main ventilation)

[0069] 18 Mat

[0070] 19 Bottom opening of the battery tray

[0071] 20 Battery tray (special design of the shelter)

[0072] 21 groups of battery systems

[0073] 22 Supply line between sorption element and battery management control unit

[0074] 23 Shelter designed as a channel

[0075] 24 Channel floor

[0076] 25 Battery management control unit

[0077] 26 Sensor or indicator

Claims

Patent claims Safety battery system (10) with controlled degassing function in case of aging, leakage or accident, comprising • at least one battery cell (11) with a venting membrane (13), • a sorption element (15) for the absorption of chemical compounds occurring during degassing, and • a sensor or indicator (26) for monitoring the saturation of the sorption element (15). Safety battery system (10) according to claim 1, characterized in that the sensor (26) is a resistance sensor, an optical sensor, or a weight sensor. Safety battery system (10) according to one of claims 1 or 2, characterized in that the sorption element (15) is a non-hydrophilic sorption element. Safety battery system (10) according to one of claims 1 to 3, characterized in that the venting membrane (13) is arranged on the top side of the battery cell (11). Safety battery system (10) according to one of claims 1 to 4, characterized in that a protective space (14) is provided on the venting membrane (13) to protect against contaminants entering the battery cell (11).Safety battery system (10) according to claim 5, characterized in that the sorption element (15) is attached within the protective space (14) at its outlet (16). Safety battery system (10) according to one of claims 5 or 6, characterized in that the protective space (14) has the form of a channel (23) and the sorption element (15) fills the channel over its entire cross-section in the direction of the venting flow. A safety battery system (10) according to any one of claims 5 to 7, characterized in that a mat (18) is provided on the outside of the vent membrane (13) of the battery cell between the battery cell (11) and the protective space (14), and that the sorption element (15) is integrated in the mat (18). A safety battery system (10) according to any one of claims 1 to 8, characterized in that at least two sorption elements (15) are included, which are located at different positions (15.1) between groups of battery cells (21). A safety battery system (10) according to any one of claims 1 to 9, characterized in that the sorption element (15) has a shape selected from cuboid, rectangular, and cylindrical, and that the sorption element (15) is located in a support (15.5), for example, a mesh-like support.A safety battery system (10) according to any one of claims 1 to 10, characterized in that the sorption element (15) has a flat shape and is applied to a membrane as a mesh-like support (15.5). A safety battery system (10) according to any one of claims 1 to 11, characterized in that the sensor or indicator (26) is connected to a battery management control unit (25) that can determine and output the saturation of the sorption element (15). Use of a sensor or an indicator (26) for saturation monitoring of sorption elements (15) in a battery system (10). Use of a safety battery system (10) according to any one of claims 1 to 12 in battery-powered means of transport, household appliances, or large-scale electrochemical storage systems.

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