Batterieeinzelzelle

Abstract

The invention relates to a single battery cell (1) with a housing (2) enclosing an active material, which has a pressure relief element (6) on one side (3) of the housing (2), wherein the side (3) having the pressure relief element (6) is formed with a thermal insulating layer in the form of a hardened potting compound (7) that adheres to the housing (2) after being poured on it. The battery cell according to the invention is characterized in that the potting compound (7) is arranged at least in a section which has a larger area than the overpressure relief element (6), and that a flow guide element (8) is embedded in the potting compound (7), a part of which covers the overpressure relief element (6).

Description

[0001] The invention relates to a single battery cell with a housing enclosing an active material, which has an overpressure relief element on one side of the housing.

[0002] Individual battery cells with a pressure relief element, which can be designed as a rupture disc, for example, are known from the prior art. These serve to ensure safety if an adjacent individual battery cell, e.g., a lithium-ion cell, experiences thermal propagation. The pressure relief elements then help to reduce the pressure in the affected individual battery cell. The rupture element tears open, or a differently designed pressure relief element opens, allowing the gases generated in the individual battery cell to escape. This process is also known as "cell venting." These venting gases are typically hot and may be accompanied by flames and / or hot particles or sparks. The particles may be abrasive and / or electrically conductive.They are therefore often critical for neighboring battery cells and surrounding components, which is why DE 10 2021 000 029 A1, cited here purely as an example, describes a multi-layered protective element for a battery. This acts as a kind of filter to retain flames, sparks, and hot particles, thereby minimizing the danger posed by the venting gases.

[0003] In general practice, a design has also become established in which thermal insulation layers are used to protect adjacent battery cells from the hot gases of a continuous battery cell. In practice, a layer of layered silicate (mica) is applied to the side containing the pressure relief element, which is particularly susceptible to thermal influences. To ensure that this layer also ruptures when the pressure relief element is activated and is not undermined by the hot gases, it must be perforated in the area of ​​the pressure relief element. In practice, this is complex and weakens the insulation's effectiveness precisely in the area where it is most critical. Furthermore, the natural material is comparatively expensive because it is complex to extract and, in particular, to process for such applications.

[0004] The applicant's unpublished German application DE 10 2023 128 877 A1 therefore describes a thermal insulation layer made of a potting compound adhering to the housing on one side of the battery housing, primarily to protect the overpressure relief element from thermal influences in the event of a neighboring cell experiencing thermal runaway. A similar structure is also described in the unpublished German application DE 10 2023 128 879 A1.

[0005] Furthermore, reference can be made to DE 20 20210 017 245 U1. This describes a construction in which the potting compound covers a pressure relief element. An elastic mat is arranged between them, which is compressed in the event of degassing to create space for the flowing gases.

[0006] If a thermal runaway occurs in an individual battery cell, the venting gases escape through the cell's pressure relief element. After passing through the venting opening, this hot, abrasive venting gas, enriched with electrically conductive particles, disperses throughout the battery. This occurs according to the existing environmental geometry and pressure conditions. In some areas, however, it would be desirable to direct the venting gases in a defined direction to prevent negative impacts on other battery cells and components.

[0007] The object of the present invention is therefore to provide a single battery cell with an improved housing which is simple, efficient and cost-effective to manufacture and yet offers a high level of protection against thermal influences in the event of thermal runaway for neighboring single battery cells and components.

[0008] According to the invention, this problem is solved by a single battery cell with the features of claim 1. Advantageous embodiments and further developments are described in the dependent claims.

[0009] The battery cell according to the invention comprises a housing enclosing its active material, which has a pressure relief element on one side. Similar to the aforementioned unpublished German application DE 10 2023 128 877 A1, the side with the pressure relief element is formed with a thermal insulating layer in the form of a hardened potting compound that adheres to the housing after being cast.

[0010] According to the invention, the potting compound is arranged in at least one section that has a larger area than the pressure relief element, and a flow guide element is embedded in the potting compound, a portion of which covers the pressure relief element. This design is very simple yet highly efficient. When applying the potting compound to the side of the housing containing the pressure relief element, a flow guide element can simply be inserted into the potting compound. If thermal propagation occurs in the individual battery cell, the pressure relief element ruptures along with the potting compound and the flow guide element. However, because the area of ​​the potting compound is larger than that of the pressure relief element, a portion of the potting compound always remains on the housing and adheres to it.The flow guide element, only a portion of which covers the pressure relief element, adheres to the housing along with the potting compound. The gap or opening through which the venting gases can escape is thus formed on the side of the pressure relief element opposite the area of ​​the adhering potting compound and the flow guide element embedded within it. The geometric arrangement of the flow guide element within the potting compound, relative to the position of the pressure relief element, allows the direction of gas flow to be determined by the design, thereby protecting, for example, electrically or thermally sensitive components from the venting gases. The flow guide element, which reinforces the potting compound on one side of the pressure relief element, can be embedded in the potting compound with virtually no impact on installation space.

[0011] In the battery cell according to the invention, the flow guide element is made of a metallic material. Such a material is particularly thermally stable enough to withstand the venting gas for a sufficiently long time together with the potting compound.

[0012] According to a highly advantageous embodiment of the battery cell according to the invention, the side of the housing containing the pressure relief element can be completely covered with the potting compound. In particular, if the thermal potting compound is designed to provide not only electrical but also thermal insulation, the full-surface potting compound on, for example, the upper side of the battery cell or its housing enables ideal protection.

[0013] Another very advantageous design can also provide for the flow guide element to be elastic or to have an elastic section in the transition area between the housing and the pressure relief element. The composite of the potting compound and the flow guide element can thus be lifted very easily, but remains adhered to the housing on one side to achieve the desired effect. The elastic, or at least partially elastic, flow guide element also serves to reinforce the potting compound, preventing it from completely tearing away around the pressure relief element.

[0014] Preferably, the flow-guiding element can be designed as a grid element. Such an element allows for a particularly good mechanical bond with the potting compound in which it is embedded and is simultaneously sufficiently elastic to optimally achieve the composite action of the potting compound and the flow-guiding element that conducts the flow of the venting gases. At the same time, a grid element is typically very light and thin.

[0015] A further highly advantageous embodiment of the battery cell according to the invention can further provide that the side with the overpressure relief element additionally has the cell terminals connected to the battery poles, wherein the cell terminals project above the potting compound in the vertical direction. The cell terminals thus project above the potting compound in every respect and can therefore be easily accessed, even if the potting compound covers the entire side, and the battery cell can be electrically connected.

[0016] The design can, in principle, be implemented in any type of cell casing. It is particularly advantageous in prismatic cell casings, especially when one of the end faces, particularly one of the larger end faces in the case of a rectangular cross-sectional shape of the individual battery cell, is used as the side that receives the thermal insulation layer.

[0017] Various materials are conceivable for the potting compound, which can also be combined with suitable fillers to make it particularly thermally resistant. For example, a polyurethane-based potting compound can be used. A silicone-based potting compound has proven particularly suitable. Such a silicone-based potting compound offers the advantage that the silicone ceramicizes or vitrifies on its surface upon contact with hot gases, so that the protective effect is even further enhanced by the action of the hot gases. The hot, highly flammable venting gases thus do not reach the area of ​​the particularly vulnerable overpressure relief element of adjacent battery cells, so that the propagation of thermal events throughout the entire battery can be reliably prevented or at least significantly delayed.The material distributed by the company Wacker under the brand name Elastosil and the designation CM185 has proven to be particularly suitable. It is a so-called "silicone rubber".

[0018] Advantageous designs and further developments also result from the exemplary embodiments, which are described in more detail below with reference to the figures.

[0019] This shows: Fig. 1 a three-dimensional view of a first possible embodiment of a single battery cell according to the invention; Fig. 2 a second possible embodiment of a single battery cell according to the invention; Fig. 3 a schematic sectional view through the area of ​​an overpressure relief element of the battery cell; and Fig. 4 a representation analogous to the one in Fig. 3 after the overpressure relief element of the individual battery cell has been activated.

[0020] In the presentation of the Fig. Figure 1 shows an exemplary prismatic single battery cell 1 in the form of a lithium-ion cell. It comprises a cell housing designated 2, on the upper side 3 of which two cell terminals 4, 5 connected to the battery poles are arranged. Between these two cell terminals 4, 5, an overpressure relief element designated 6 is arranged. This overpressure relief element 6 can, for example, be a rupture disc with a round or, preferably, an oval cross-section. This is connected to the surrounding material of the cell housing 2 or the side 3 only via a correspondingly weakened material. Thus, a predetermined breaking point is provided around or for the most part around the circumference of this rupture disc.Typically, such cell housings 2 are made of materials exhibiting low elongation at break, low tensile strength, and low tear strength. By dimensioning the predetermined breaking point, it is possible to determine the internal pressure at which the overpressure relief element 6 ruptures within the cell housing 2. In the event of a thermal event in the individual battery cell 1, the ruptured overpressure relief element 6 then allows the pressure to be reduced by expelling the so-called venting gases through the resulting opening.

[0021] To protect this overpressure relief element 6, which is not directly visible here, from hot venting gases from adjacent battery cells 1 that have experienced a thermal event, the side 3 of the cell housing 2 is provided with a potting compound 7, shown here with cross-hatching. This potting compound 7 is poured onto the side 8 in its liquid state, where it adheres and hardens. It bonds to the material of the cell housing 2, i.e., side 3, and thus reliably protects the underlying area containing the overpressure relief element 6 if the potting compound 7 is exposed to hot gases, flames, abrasive and / or hot particles.

[0022] A silicone material, such as the aforementioned silicone material Elastosil CM185, can be used as the potting compound 7. This material has ideal properties to reliably rupture beneath the potting compound 7 in the event of thermal activation of the overpressure relief element 6, without offering greater resistance to the escaping gases than that of the overpressure relief element 6. Furthermore, when exposed to hot gases, flames, or hot particles, such a material for the potting compound 7 tends to undergo a vitrification or ceramization of the surface, thus providing excellent thermal protection for underlying components. In addition to this material, other silicone-based potting compounds or polyurethane potting compounds, possibly with suitable fillers to improve thermal insulation, are also conceivable.

[0023] Fig. 2 shows the one from Fig. 1. Already known structure, in which only a smaller area of ​​side 3 is coated with the potting compound 7. For the reasons described below, this area coated with the potting material should, however, in any case be larger than the overpressure relief element 6.

[0024] Fig. Figure 3 shows a schematic section through precisely this area of ​​the cell housing 2 with the pressure relief element 6 and the potting material or encapsulation compound 7. A further essential component is visible: a flow guide element 8 in the form of an insert in the encapsulation compound 7. The lowest layer shown is the material of the cell housing 2. The pressure relief element 6 is implemented within this material by incorporating two predetermined breaking points 9. The encapsulation compound 7, again shown with cross-hatching, is visible on the material of the cell housing 2. The aforementioned flow guide element 8 is embedded within the encapsulation compound 7. It is surrounded on all sides by the encapsulation compound 7. It can, for example, be designed as a metallic grid element, so that it is additionally penetrated by the encapsulation compound 7 and forms a mechanically stable and load-bearing bond with it.The material, geometry and design of the flow guide element 8 can be adapted to the specific application if required, e.g. with regard to temperature resistance, elasticity, size or possibly its own predetermined breaking points.

[0025] To achieve the desired functionality, the flow guide element 8 now extends from an area next to the overpressure relief element 6, which is shown here on the left, to approximately the area of ​​the predetermined breaking point 9 to the right of the overpressure relief element 6. Fig. 3. If a thermal event occurs in the individual battery cell 1, the internal pressure rises until the predetermined breaking point 9 of the overpressure relief element 6 gives way. Due to the flow guide element 8 for reinforcing the potting compound 7 above the in Fig. 3. To the right of the overpressure relief element 6, on the side of the predetermined breaking point 9, the structure tears open on the left. This could also be exacerbated by the fact that the predetermined breaking point 9 is not fully formed around the perimeter and is, for example, interrupted on the right.

[0026] Together with the predetermined breaking point 9 (left), the potting compound 7 also tears, as described in the unpublished German application with file number DE 10 2023 128 877 A1 of the applicant. The flow guide element 8 is pushed upwards with the torn potting compound 7. However, it remains attached to the cell housing 2 at its right end together with the potting compound 7. This results in the following: Fig.In the scenario shown in Figure 4, the flow guide element 8 deforms due to its elasticity or an elastic region within the flow guide element 8 above the right-hand predetermined breaking point 9, as shown. The venting gases, indicated here by arrow V, thus flow primarily to the right. In the exemplary design shown here, the area to the left of the dashed line is therefore efficiently protected from the venting gases. The design could, of course, be modified so that the venting gases would be directed to the right, to the rear, or to the front.

Claims

[1] Battery cell (1) with a housing (2) enclosing an active material, which has a pressure relief element (6) on one side (3) of the housing (2), wherein the side (3) having the pressure relief element (6) is formed with a thermal insulating layer in the form of a cured potting compound (7) adhering to the housing (2) after being poured, wherein the potting compound (7) is arranged at least in a section which has a larger area than the pressure relief element (6), and wherein a flow guide element (8) is embedded in the potting compound (7), a portion of which covers the pressure relief element (6), and wherein the flow guide element (8) is made of a metallic material. [2] Battery cell (1) according to claim 1, characterized by , that the side (3) of the housing (2) having the overpressure relief element (6) is completely covered with the potting compound (7). [3] Battery cell (1) according to claim 1 or 2, characterized by , that the flow guide element (8) is elastically designed or has an elastic area in the area of ​​the transition from the housing (2) to the overpressure relief element (6). [4] Battery cell (1) according to claim 1, 2 or 3 characterized by , that the flow guide element (8) is designed as a grid element. [5] Battery cell (1) according to any one of claims 1 to 4, characterized by , that the side (3) with the overpressure relief element (6) additionally has the cell terminals (4, 5) connected to the battery poles, wherein the cell terminals (4, 5) extend above the potting compound (7) in the vertical direction. [6] Battery cell (1) according to any one of claims 1 to 5, characterized by , that the housing (2) is designed as a prismatic housing. [7] Battery cell (1) according to any one of claims 1 to 6, characterized bythat the potting compound (7) is based on polyurethane or - preferably - on silicone.

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