Individual battery cell

Abstract

The invention relates to an individual battery cell (1) comprising a housing (2) which encloses an active material and has an overpressure relief element on one side (3) of the housing (2), wherein at least the region on the side (2) that comprises the overpressure relief element is provided with a thermal insulation layer (7). The individual battery cell according to the invention is characterised in that the thermal insulation layer is in the form of a cured potting compound (7).

Description

[0001] Single battery cell

[0002] 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, according to the type defined in more detail in the preamble of claim 1.

[0003] Individual battery cells with an overpressure relief element, which can be designed as a rupture disc, for example, are generally known from the state of the art. These serve to ensure safety if a neighboring individual battery cell, e.g. a Li-ion cell, experiences thermal propagation. In this context, this is also referred to as thermal propagation. The overpressure relief elements then help to reduce the pressure in this individual battery cell. The bursting element ruptures or a differently designed overpressure relief element opens and allows the gases developing in the individual battery cell to escape. This process is also referred to as "cell venting." These venting gases are typically hot and may be accompanied by flames and / or hot particles or sparks.They may therefore also be critical for neighboring individual battery cells and the surrounding area, which is why DE 10 2021 000 029 A1, cited here purely as an example, describes a multi-layer protective element for a battery. This serves as a kind of filter to retain flames, sparks, and hot particles, thereby minimizing the danger posed by the venting gases.

[0004] DE 102021 005 538 A1 describes a battery with a venting device. An insulating compound is arranged in the area of ​​a cooling plate near the venting devices to protect the cooling plate from the hot gases released in the event of venting. DE 102008 059 971 A1 discloses a battery in which an electronic component is surrounded by a thermal protective layer.

[0005] An electrical energy storage device with a degassing chamber is claimed in DE 10 2022 103 336 A1. The storage cells are fixed in a storage housing via a filling, which can also be in the form of a potting compound. The degassing chamber is formed by a hollow insert in the filling.

[0006] Finally, reference can also be made to DE 102010 038 308 A1, which describes a battery in which the electrode-separator arrangements are at least partially encased in a potting compound.

[0007] In general practice, a design has also become established in which thermal insulation layers are used to protect neighboring individual battery cells from the hot gases of a continuous individual battery cell. In general practice, a layer of layered silicate (mica) is applied to the side containing the overpressure relief element, which is particularly susceptible to thermal influences. To ensure that this layer also tears when the overpressure relief element is activated and is not undermined by the hot gases, it must be perforated in the area of ​​the overpressure relief element. In practice, this is complex and time-consuming, and the perforation weakens the insulation's effect in precisely the area where the insulation is particularly relevant. In addition, the natural material is comparatively expensive because it is complex to mine and, in particular, to process for such applications.

[0008] 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 case of thermally continuous adjacent single battery cells.

[0009] According to the invention, this object is achieved by a single battery cell having the features of claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments emerge from the dependent subclaims. Similar to the prior art, at least that side of the housing of the single battery cell which has the overpressure relief element has a thermal insulation layer to protect this side and, above all, the overpressure relief element from thermal influences in the event of a neighboring cell thermally failing.

[0010] The inventive solution uses a potting compound instead of the expensive and complex-to-process natural material mica, which forms the thermal insulation layer after curing. Such a potting compound can be applied simply and efficiently to the respective side of the housing of the individual battery cell, which is also referred to below as the cell housing. After curing, a protective layer is created which, in the event of thermal runaway of this individual battery cell, causing its overpressure relief element to open, simply tears open in the area of ​​the overpressure relief element without the need for perforations or the like. Because the layer adheres directly to the cell housing after pouring, there is no risk of it being undermined by the escaping hot gases.This makes it extremely easy and efficient to ensure good thermal protection of neighboring cells without making it difficult to blow off venting gases from the affected individual battery cell.

[0011] Various materials are conceivable for the potting compound, which can also be provided with suitable fillers to make this potting compound particularly thermally resilient. For example, a polyurethane-based potting compound can be used. A silicone-based potting compound has proven to be particularly suitable. Such a silicone-based potting compound offers the advantage that the silicone ceramizes or vitrifies its surface upon contact with hot gases, so that the effect of the hot gases even improves the protective effect. The hot, highly flammable venting gases thus do not reach the area of ​​the particularly vulnerable overpressure relief element of neighboring individual battery cells, so that the progression of thermal events throughout the entire battery can be reliably prevented or at least significantly delayed.The material marketed by Wacker under the brand name Elastosil and the designation CM 185 has proven particularly suitable. This is a so-called "silicone rubber."

[0012] According to a highly advantageous embodiment of the housing of the single battery cell according to the invention, the overpressure relief element is arranged in a recess formed in the side of the housing that features the overpressure relief element. The overpressure relief element is thus slightly recessed relative to the surrounding material of the side that features it. This has the crucial advantage that during assembly and application of the potting compound, the potting compound can be filled into the recess, thus ensuring simple and efficient application of the potting compound, also known as potting material, in a liquid state, so that it hardens precisely where needed without contaminating other areas of the single battery cell.

[0013] An alternative to such a recess for receiving the potting material can also be provided, according to an alternative embodiment of the single battery cell according to the invention, for the overpressure relief element to be circumferentially surrounded by a collar. Such a collar can, for example, be formed integrally with the cell housing, depending on the design of the side, or subsequently attached to it, for example, by adhesive bonding. Similar to the alternative recess described above, this collar enables the application of the liquid potting material, which is then held within the collar, where it can harden and form the thermal insulation layer.

[0014] Of course, a recess and a collar can also be combined, so that the recess is additionally surrounded by the collar. This is particularly useful if, due to design constraints, an overpressure relief element with a certain height is to be used, and the recess alone cannot be designed to have a depth greater than the height of the overpressure relief element. The collar could then be used to create the additional height to ensure complete and full coverage of the overpressure relief element with the potting material.

[0015] According to a very advantageous development of the individual battery cell according to the invention, the collar can partially or completely surround part of the side. The collar can therefore be arranged such that the entire side is surrounded by it and thus the entire side having the overpressure relief element is covered with the thermal insulation layer by the cured potting material. Alternatively, only part of the side can be surrounded by the collar, so that, similar to the recess described above, thermal insulation is achieved by the potting material exclusively in the area of ​​the overpressure relief element. Of course, all intermediate sizes are also conceivable here, so that, for example, half of the side, three-quarters of the side or similar is covered with the thermal insulation layer by the potting material.The collar is adjusted in size and shape to the desired size of the insulation layer.

[0016] As already mentioned above, the collar can be placed onto the housing material or, preferably, it can be formed from the material of the housing itself. According to a very advantageous development, the collar can also be formed by a film surrounding the side of the housing containing the overpressure relief element. Such a film could in principle be adhered to the side walls of the housing as a type of adhesive strip, in order to completely surround the upper side of the housing and protrude beyond it as a collar. The use of film bags, as is common with pouch cells, is also conceivable here, for example by welding this film bag all the way around to a lid on the side containing the overpressure relief element, and allowing it to protrude beyond this lid to form the collar for the volume containing the potting material.

[0017] Another very advantageous embodiment of the single 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. In the event that these, or at least one of them, lie within the area surrounded by the collar, then according to an advantageous development, the height of the cell terminal is greater than the height of the collar, so that the applied potting compound surrounds the cell terminal circumferentially, but does not wet its upward-facing surface, so that the cell terminal protrudes through the cured potting compound as a thermal insulation layer. In principle, the structure can be implemented with any type of cell housing.The structure is particularly advantageous in the case of prismatic cell housings if, in particular, one of the end faces, in particular 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 which is provided with the thermal insulation layer.

[0018] Advantageous embodiments and further developments also emerge from the exemplary embodiments which are presented in more detail below with reference to the figures.

[0019] Showing:

[0020] Fig. 1 is a three-dimensional view of a first possible embodiment of a single battery cell according to the invention;

[0021] Fig. 2 shows a second possible embodiment of a single battery cell according to the invention; and

[0022] Fig. 3 shows a third possible embodiment of a single battery cell according to the invention.

[0023] Figure 1 shows an example of a prismatic single battery cell 1 in the form of a lithium-ion cell. It comprises a cell housing, designated 2, on whose upper side 3 two cell terminals 4, 5 connected to the battery poles are arranged. Between these two cell terminals 4, 5 there is a recess, designated 6, in which an overpressure relief element (not visible here) is arranged. This overpressure relief element can, for example, be a bursting disc with a round or, in this case, preferably oval, cross-section. This is connected to the surrounding material of the cell housing 2 or side 3 only via a correspondingly weakened material. A predetermined breaking point is therefore provided circumferentially or largely circumferentially around the circumference of this bursting element.Typically, such battery casings are made of materials that exhibit low elongation at break, low tensile strength, and low tear strength, so that the dimensioning of the predetermined breaking point can determine the internal pressure at which the bursting element ruptures in the cell casing 2. In the event of a thermal event, the bursting element can then relieve pressure in the individual battery cell 1 by expelling the so-called venting gases through the resulting opening.

[0024] To protect this overpressure relief element (not visible here) from hot venting gases from neighboring individual battery cells that have experienced a thermal event, the recess 6 is provided with a potting compound 7, shown here cross-hatched. This potting material 7 is introduced into the recess 6 in a liquid state and then hardens there. It bonds to the material of the cell casing 2 or side 3 and thus reliably protects the area below with the overpressure relief element in the event that the potting material 7 is exposed to hot gases, flames, and / or hot particles.

[0025] A silicone material, such as the silicone material Elastosil CM 185 mentioned above, can be used as potting material 7. This material has ideal properties for reliably rupturing the overpressure relief element beneath the potting material 7 in the event of thermal response, without offering greater resistance to the escaping gases than that of the bursting element. On the other hand, when exposed to hot gases or flames or hot particles, the material tends to undergo a type of vitrification or ceramization of the surface, thus providing very good thermal protection for the elements underneath. In addition to this material, other silicone-based potting compounds or PU potting compounds are also conceivable, possibly with suitable fillers to improve the thermal insulation effect.

[0026] Figure 2 shows the structure already known from Figure 1, in which, instead of the recess 6, a circumferential collar designated 8 is arranged around the entire side 3 of the battery housing 2. The collar 8 is not as high as the cell terminals 4, 5. Pouring the potting material 7, which is again shown cross-hatched here, then ensures that the entire side 3 is provided with the thermal protection layer, but the cell terminals 4, 5 protrude through this protective layer. Of course, the collar 8 could also be designed to surround a smaller area or volume. This can range from exclusively covering the overpressure relief element requiring particular protection to fully covering the side, as shown in Figure 2.Purely by way of example, the illustration in Figure 3 shows a structure in which a part of the side 3 between the two cell terminals 4, 5 is surrounded by the collar 8 and accordingly covered with the potting material 7 as a thermal protection layer.

Claims

Patent claims 1. Single battery cell (1) with a housing (2) enclosing an active material, which has an overpressure relief element on one side (3) of the housing (2), wherein at least the area of ​​this side (3) having the overpressure relief element is provided with a thermal insulation layer (7), characterized in that the thermal insulation layer is in the form of a cured potting compound (7) which adheres to the overpressure relief element of the housing (2) after pouring.

2. Single battery cell (1) according to claim 1, characterized in that the side (3) of the housing (2) having the overpressure relief element has a recess (6) surrounding the overpressure relief element.

3. Single battery cell (1) according to claim 1 or 2, characterized in that the side (3) of the housing (2) having the overpressure relief element has a collar (8) surrounding the overpressure relief element.

4. Single battery cell (1) according to claim 3, characterized in that the collar (8) partially surrounds a part of the side (3) or completely surrounds the side (3).

5. Single battery cell (1) according to claim 3 or 4, characterized in that the collar (8) is formed by the material of the housing (2).

6. Single battery cell (1) according to claim 3 or 4, characterized in that the collar (8) is formed from material glued to the side (3).

7. Single battery cell (1) according to claim 3 or 4, characterized in that the collar (8) is designed as a film surrounding the side (3).

8. Single battery cell (1) according to one of claims 1 to 7, characterized in that the side (3) with the overpressure relief element additionally has the cell terminals (4, 5) connected to the battery poles.

9. Single battery cell (1) according to claim 8, characterized in that in the event that at least one of the cell terminals (4, 5) lies within the area of ​​the side (3) surrounded by the collar (8), this is formed higher than the collar (8).

10. Single battery cell (1) according to one of claims 1 to 9, characterized in that the housing (2) is designed as a prismatic housing.

11. Single battery cell (1) according to one of claims 1 to 10, characterized in that the potting compound is based on polyurethane or - preferably - on the basis of silicone.

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