Gas outlet plate for battery module

Abstract

The present invention relates to a gas outlet plate (1) having a gas outlet flap (3) with an adjustable pressure-actuated portion as a safety device for guiding a high-temperature gas flow out of the cell area of ​​a module in the event of thermal runaway of a battery cell (6). The gas outlet plate (1) has a base plate (2) made of a high-temperature resistant material, into which an adjustable gas outlet flap (3) is inserted. The gas outlet flap (3) has a free periphery (4) that defines a flapable area and a bent edge (5) that connects the gas outlet flap (3) to the base plate (2), and opens when a high-temperature gas flow (8) impinges on it. The present invention also relates to the use of the gas outlet plate (1) for manufacturing a battery module and to a battery module equipped with the gas outlet plate (1).

Description

[Technical Field]

[0001] The present invention relates to a gas conduction plate as a safety device for a battery module, which contributes to the reliable conduction of hot gas that is rich in conductive particles and that escapes from a battery cell in the module in the event of a thermal failure of the battery cell, thereby preventing its transfer to adjacent cells and the formation of an arc between the battery housing material and current-conducting components and resulting short circuit.

[0002] Furthermore, the invention relates to a battery module with a gas conduction plate according to the invention and to the use of a gas conduction plate according to the invention for a battery module. [Background technology]

[0003] Vehicles with electric drives use rechargeable battery systems, particularly lithium-ion battery cells. Two or more cells are arranged as closely as possible in parallel in a module within a battery cell or module housing and are electrically connected to each other. Several battery modules are also combined into a battery package and electrically connected to each other.

[0004] For operation in vehicles, battery systems must have a very high energy density, but this also carries a high potential safety risk. Safe operation of battery systems here is only possible up to a relatively low critical temperature. At around 80°C, oxidation processes between the components of the electrolyte and the components of the battery cell's electrodes begin, which leads to cell heating and ultimately cell damage, leading to an uncontrollable temperature rise in the cell, known as thermal runaway.

[0005] The increasing temperature in the cell leads to gas formation, which can cause the cell to explode due to the increased gas pressure, in which case the high pressure causes easily combustible gases to escape from the cell, which usually ignite immediately when they come into contact with air, resulting in extremely high temperatures. Furthermore, the extremely hot gases also produce conductive particles, such as graphitic carbon, metal particles, and other decomposition products from the cell contents.

[0006] In order to be able to reduce the cell pressure that has built up due to gas formation, it is known to provide the battery cell with a vent opening, such as a safety valve or a rupturable diaphragm, that allows the gas to escape in a directed manner around the battery cell.

[0007] However, even in this case, in order to guarantee the operational safety of the battery cells and in particular of any vehicle occupants that may be present, it must be ensured that the transmission of energy to adjacent cells and modules is avoided so that the propagation of thermal runaway is prevented or at least suppressed as much as possible.

[0008] In particular, gases containing conductive particles must be prevented from creating short circuits between current-carrying components and the ground of the battery package, forming arcs that can have temperatures up to several thousand degrees Celsius.

[0009] For operational safety and the protection of vehicle occupants, a suitable protection concept for the battery package must ensure that no sparks or flames occur, i.e., no flames become visible, outside the battery package for a period of several minutes after the first signs of thermal runaway in a battery cell are detected, which is preferably less than five minutes to meet safety standards. Summary of the Invention [Means for solving the problem]

[0010] The invention now relates to a gas outlet plate with adjustable gas outlet flaps having the features of claim 1.

[0011] Each dependent claim relates to a preferred embodiment.

[0012] The invention further relates to a battery cell module comprising a gas outlet plate with an adjustable gas outflow flap according to the invention, a module housing comprising a gas outlet plate with an adjustable gas outflow flap, and the use of a gas outlet plate with an adjustable gas outflow flap according to the invention for a battery module or a module housing.

[0013] The gas discharge plate with adjustable gas discharge flaps according to the present invention is formed from a high-temperature resistant base plate, which has gas discharge flaps that are configured to open when a predetermined gas pressure is applied, allowing gas to be discharged from the interior of the battery module.

[0014] "Adjustable gas outlet flap" means in the sense of the present invention that the gas outlet flap is only activated when a predetermined pressure is applied.

[0015] The battery cell experiencing thermal runaway is also called the propagation battery cell.

[0016] The gas outflow flap is a partially cut-out area of ​​the base plate, where a portion of the periphery of the area is cut out from the base plate, this cut-out portion being referred to herein as the "free periphery", and only the remaining portion of the periphery being bonded to the base plate, this bonded portion being referred to herein as the "bent edge".

[0017] The free periphery may be separated from the base plate consistently throughout the thickness of the base plate, or the separation may be only partial, for example so that a cut in the thickness direction of the base plate does not penetrate completely through the base plate, or the base plate may have perforations along the free periphery.

[0018] The shape of the gas outlet flap can be selected as required: it can be circular, oval or rectangular. The gas outlet flap can be selected to be sufficiently large so that the impinging gas flow is guided reliably and completely.

[0019] In normal operation, the base plate and the gas outflow flap form a substantially flat surface. When the pressure acting on the gas outflow flap exceeds a predetermined value as a result of gas outflow from the battery cell, the gas outflow flap yields to the pressure and flaps along the bent edge, thereby directing the gas flow away from the propagating battery cell.

[0020] The gas conduction plate of the present invention allows the hot gas flow containing conductive particles flowing from overheated cells of the module to be quickly and directly conducted away from the battery module without causing short circuits and arc formation between current-conducting components and the ground of the battery package.

[0021] Thus, transfer to adjacent battery cells and the occurrence of visible flames outside the battery package can be prevented for a period of at least 5 minutes, in particular for a period of at least 7 minutes or more, consistent with safety protocols.

[0022] Regarding the problem addressed, the gas outlet plate with gas outlet flap according to the present invention is manufactured from a high-temperature resistant material, which ensures reliable gas outlet without the plate itself blocking the flame or deforming due to thermal effects.

[0023] The gas outlet plate is preferably formed from a layer structure of high-temperature resistant fiber composite material, with particularly high-temperature resistant fibers being used for each layer.

[0024] The gas conducting plate according to the invention can likewise be used for modules consisting of prismatic cells, cylindrical cells (circular cells) or pouch cells.

[0025] Due to this structure, the gas conducting plate according to the present invention can absorb the mechanical loads that occur during assembly of the battery cells, so that the gas conducting plate can simultaneously be used as a structural element for the module housing.

[0026] For example, a gas guide plate with adjustable gas outflow flaps according to the invention can be incorporated into the module housing depending on the position of the vent openings on the outer edge of the battery cells.

[0027] For example, if the vent openings are located on the top surfaces of the battery cells of the battery cell array, the gas lead-out plate according to the present invention can be formed as a cover of the module housing, and if the vent openings are located on the bottom surfaces of the battery cells, the gas lead-out plate can form the installation surface or bottom surface of the module housing.

[0028] The gas guide plate can be arranged as a component in the region between the region of the battery cell having the vent openings in the module and the wall of the module housing.

[0029] In order to ensure that the gas flow from the propagation cells can be guided out of the danger zone as quickly as possible if necessary, it is desirable that the respective gas outflow flaps are positioned close to the vent openings of the cells, thereby ensuring that the gas outflow flaps can be opened as quickly as possible even under combined temperature and pressure loads. The gas outflow flaps of the non-propagation cells must remain closed to avoid contact between the non-propagation cells and conductive particles in the gas in this area.

[0030] Typically, each battery cell in a module is assigned one gas outlet flap in the gas outlet plate. For very large battery cells with two or more vent openings, two or more gas outlet flaps can be assigned if necessary. Depending on the specific application, it is also possible to provide fewer gas outlet flaps than battery cells.

[0031] For example, according to one embodiment, for a module of battery cells with vent openings on their bottom surfaces, a gas outlet plate can be used as a mounting surface for the battery cells and simultaneously as the bottom plate of the module, and the gas outlet plate for each battery cell can have a gas outlet flap whose peripheral shape can preferably be adapted to the shape of the bottom surface of the battery cell, for example, to a substantially circular shape in the case of circular cells or a substantially rectangular shape in the case of prismatic cells.

[0032] Generally, the area of ​​the gas outflow flap is small compared to the bottom area of ​​the battery cell, but is at least large enough to allow the vent opening and, if necessary, the escaping gas flow to be fully detected.

[0033] An important feature of the present invention is the determination and adjustment of the opening pressure of the gas outlet flap. The opening pressure must be adapted to the operating pressure of the vent opening of the battery cell. In particular, the opening pressure must be selected low enough to ensure that the gas flow is quickly and reliably guided out of the propagation cell.

[0034] If the opening pressure is too high, the flaps will open too late when needed, or even not at all. If the opening pressure is too low, external influences, for example during module manufacture, can cause the gas outlet flaps to open prematurely, or the pressure of the gas escaping from one cell can open adjacent gas outlet flaps when needed, resulting in contamination of adjacent cells with conductive particles from the gas flow.

[0035] Vent openings in commercially available lithium-ion battery cells are typically opened at pressures between 0.4 and 13 bar. The pressure at which opening occurs is controlled by a variety of factors, such as cell size, cell chemistry, state of charge, cell geometry, battery cell vent opening design, and basic cell design.

[0036] In response to these requirements, the invention provides for an appropriate adjustment of the opening pressure of the gas outflow flap, which is controlled in particular based on the length of the bent edge and the thickness of the base plate, as well as the size of the gas-applied surface of the gas outflow flap and the material composition of the base plate.

[0037] In the case of a gas outlet flap with a circular basic contour, the length of the bent edge is the distance between the two end points of the circle segment that forms the flap surface, i.e. the free periphery defines the circle segment that forms the flap surface, as shown below, for example, in FIG. 1.

[0038] In order to determine and adjust the defined opening pressure of a gas outlet plate with a gas outlet flap according to the invention, in particular for designing the geometry of the bent edge, for example the dimensions including the length, a simple test using a bending strip and weights has been developed, where the bending strip is made of the same material and has the same thickness as that used for the gas outlet plate. This test is explained below with reference to FIG. 5 on the example of a gas outlet flap with a circular basic shape.

[0039] With a circular diameter of 43.5 mm, starting from a working pressure of the degassing opening of 0.4 bar, a pressure of 0.04 MPa acts on the circular surface, which corresponds to a force of 59.4 N and thus a weight of 6 kg.

[0040] Starting from this, the determination of the opening pressure can be carried out on a correspondingly manufactured bending strip, for example using a scale such as a spring balance, and the weight can be calculated, in which a bending strip having a set width is bent from the bending edge to the end opposite the free circumference, corresponding to the bending edge and the length of the extent of the flap's flapable area.

[0041] Likewise, the tests for setting and determining the operating pressure for the gas outlet flaps can be used with basic shapes other than circular.

[0042] The gas outlet plate according to the invention is made of a high-temperature resistant material, which allows reliable discharge of hot gases without the gas outlet plate itself blocking the flame or deforming due to thermal influences. Preferably, the gas outlet plate is resistant to temperatures of at least 600°C, preferably higher, up to at least 1400°C, and is electrically non-conductive.

[0043] Preferably, the gas outlet plate is formed from a layer structure consisting of layers of fiber composite material, for which high-temperature-resistant fibers are used, in particular mineral fibers such as basalt fibers, glass fibers, silicate fibers and oxide ceramic fibers.

[0044] The fibers may be present in the form of planar structures such as woven fabrics or nests, which themselves can be made from the fibers herein by roving or spinning.

[0045] In one embodiment, the fiber extension may be bidirectional, for example 0° / 90°, but the fiber extension may vary as desired, for example multi-directional, for example 0° / 90° / 45°, etc.

[0046] The plastics used as the matrix material also have high temperature stability, and examples of such plastics are silicone resins, especially those with a high SiO content of 50 to 90%, particularly preferably 75% or more.

[0047] Silicone resins with an SiO content of at least 80% have proven particularly suitable. According to one embodiment, silicone resin / phenolic resin mixtures, silicone / epoxy mixtures or other suitable resin mixtures can be used to improve or adjust the properties.

[0048] As silicone resins, di- and / or tri-functional polysiloxanes, preferably with methyl and / or phenyl substituents, can be used.

[0049] An example of a suitable silicone resin is a methyl silicone resin sold under the trademark SILRES® MK by Wacker.

[0050] The individual layers of the gas guide plate may have different fibers and / or different fiber orientations.

[0051] For example, the layer structure may consist of one or two cover layers of a first fiber composite material with (optionally) one or more intermediate layers of a second fiber composite material. The layers of different fiber composite materials may be arranged alternately.

[0052] The thickness of each individual layer may be as thick as necessary, but it is desirable to make it as thin as possible.

[0053] The total thickness of the gas guide plates should be as small as possible in consideration of the desired space saving, preferably not exceeding 1.5 mm, and a thickness of 1 mm or less is preferred in consideration of the desired compact and space-saving construction of the battery array.

[0054] Preferably, the thickness should be selected so that the gas guide plate has sufficient mechanical stability to be able to support the battery cells, for example, until the battery array is sealed, for example, by a foam sealant. If necessary, a support sheet can also be used here, as will be explained in more detail below.

[0055] According to one embodiment, a thin film can be attached to the side of the gas outlet plate facing away from the cells, which serves to mechanically stabilize the gas outlet plate and thus prevent premature opening of the gas outlet flaps due to the action of forces during the module manufacturing process.

[0056] For example, depending on the application, the intermediate space between the mated battery cells can be filled with an expanding foam material for stabilization and electrical insulation. The resulting expansion pressure can be great enough to push open the gas escape flap. In one embodiment of the present invention, the film prevents accidental premature opening.

[0057] Furthermore, there is no risk of moisture ingress, as the film seals the separation line along the free periphery between the gas outlet flap and the base plate.

[0058] Suitable films must have low tear resistance and low tear strength to ensure that they can break quickly under compressive load and reliably open the gas outflow flaps when required. Furthermore, it is advantageous for the film to have a low melting point, so that the opening of the gas outflow flaps is thermally assisted by the melting of the film.

[0059] Self-adhesive films are particularly advantageous since they can be applied without great expense.

[0060] An example of a suitable self-adhesive sheet is the electrical adhesive film sold by SynFlex under the product name SynTape®. Particularly suitable for its low thickness, low breaking force, and low elongation at break is SynTape® F / X.50, which has a backing made of aramid paper and an acrylate-based adhesive, a total thickness of 0.05 mm, a breaking force of 35 N / 10 mm, and an elongation at break of 5%. However, it should be understood that films with other thicknesses and breaking force and elongation values ​​can be used depending on the requirements of the specific application.

[0061] The invention will now be explained in more detail using the example of a gas outlet plate for circular cells with reference to the accompanying drawings, which show an embodiment of the use of a gas outlet plate with adjustable gas outflow flaps according to the invention. [Brief explanation of the drawings]

[0062] [Figure 1] 1 shows a plan view of a gas outlet plate according to the invention, in which adjustable gas outlet flaps are arranged in the area of ​​the mounting surface of the battery cells; [Figure 2] 1 shows a plan view of a gas outlet plate with adjustable gas outlet flaps according to the invention; [Figure 3] FIG. 3 is a longitudinal cross-sectional view taken along line A in FIG. 2. [Figure 4] FIG. 3 is a longitudinal cross-sectional view taken along line A in FIG. 2 with circular cells. [Figure 5a] FIG. 1 is a schematic diagram illustrating a bend strip test for determining bend edge length. [Figure 5b] FIG. 1 is a schematic diagram illustrating a bending strip test for determining operating pressure. [Figure 6] 2 is a plan view showing the lower surface of the gas guide plate of FIG. 1 having a cover film. DETAILED DESCRIPTION OF THE INVENTION

[0063] 1 shows a plan view of a gas outlet plate 1 according to the invention, comprising a base plate 2 and an array of adjustable gas outlet flaps 3 for arranging the circular cells. The array here is arranged in a symmetrical hexagonal shape in order to achieve the densest possible packing of the circular cells. It should be understood that in principle any other suitable arrangement is also possible.

[0064] In the embodiment shown, the gas outflow flap 3 has a substantially circular shape with a circular arc-shaped free periphery 4. A connecting line between two end points of the free periphery 4 defines a bent edge 5 of the gas outflow flap 3, along which the gas outflow flap 3 opens as required.

[0065] Each gas outflow flap 3 faces in the same direction, with the bent edges 5 oriented parallel to one another.

[0066] However, the orientation and direction of the bent edge 5 of the gas outflow flap can be selected according to the requirements of a particular application.

[0067] In the figure, each gas outlet flap 3 corresponds to a mounting surface for a circular cell (not shown).

[0068] Figure 2 shows a plan view of a gas outlet plate similar to Figure 1, in which circular cells 6 are shown in the three gas outlet flaps 3 located on the right side of the lower row in Figure 2. The bottom surfaces of these circular cells 6 have a diameter somewhat larger than that of the gas outlet flaps 3, as shown in the illustration of the gas outlet flap 3 with the circular cell 6 in its center, and completely cover the gas outlet flap 3.

[0069] Figures 3 and 4 show longitudinal cross sections taken along line A of the lower row of gas outlet flaps 3 of Figure 2, where Figure 3 shows a cross section without circular cells 6 and Figure 4 shows a cross section with circular cells 6.

[0070] In Figure 3, all gas outlet flaps 3 in the row are closed, and the base plate 2 and gas outlet flaps 3 form a single plane. Figure 4 shows an example of a fault involving a propagation cell 7, in which a hot gas flow 8 escapes through the vent opening at the bottom of the circular cell 7, and the pressure of this gas flow 8 opens the gas outlet flaps 3 located below it. The gas flow 8 here is routed through the open gas outlet flaps 3 from the installation area of ​​the battery cells 7, e.g., from the module housing. Because the gas outlet flaps 3 of the non-propagation cells remain closed, contact between the gas flow 8, especially between conductive particles present in the gas flow 8, and the battery cells or other conductive components does not occur. This reliably prevents thermal runaway from the propagation cell 7 from transferring to other cells 6, particularly the formation of short circuits and arcs.

[0071] 5a and 5b show diagrammatically the determination and regulation of the opening pressure of an adjustable gas outflow flap 3 according to the invention in the example of a gas outflow flap 3 with a circular basic shape.

[0072] The flapable member of the gas outflow flap 3 is a circular segment or part of a circle with a diameter d (43.50 mm in the figure). The free periphery 4, i.e. the area separated or at least partially separated from the base plate 1, defines a circular arc, where the bent edge 5 is the connecting line between the endpoints of the arc, i.e. the chord of the circle.

[0073] In other words, as shown in Figure 5a, the length of the bent edge 5 is obtained from the distance from the end point of the arc defined by the free perimeter 4 to the tangent line that is tangent to the full circle diameter and is located closest to the bent edge (to the right in the drawing). The length of the bent edge is the distance between the two intersection points with the tangent line. The maximum extent of the flapable area is the distance between the bent edge to the tangent line at the full diameter at the free perimeter 4 (to the left in the drawing).

[0074] In Figure 5b, the situation of Figure 5a is transferred to a bending strip test, whereby for a given material composition, the bending edge is bent to a set length, so that the opening pressure can be determined at the gas outflow flap corresponding to Figure 5a.

[0075] Figure 5b shows the various widths for the bent edge in the horizontal direction and the corresponding distance from the tangent to the bent edge in the vertical direction at the free periphery 4. This gives a measure of the residual area, here a measure of the circular area that can be opened by gas pressure.

[0076] FIG. 6 shows a gas outlet plate 1 with an adjustable gas outlet flap 3 having an attached film 9, where the film 9 is attached to the side of the gas outlet plate 1 opposite the side with the battery cells. The film 9 is used in particular to shield and prevent moisture from penetrating to the battery side. Therefore, the film can be designed to be very thin. Furthermore, the film 9 can also support mechanical stability.

[0077] The film 9 should have a low elongation at break and a low resistance to break so as not to prevent the opening of the corresponding gas outflow flap 3 when necessary, i.e. in the event of a battery cell failure. Preferably, when pressure is applied, the film 9 should break as quickly as possible with as little expansion as possible. [Example]

[0078] A gas outlet plate with gas outlet flaps for circular cells according to the invention was manufactured, and the opening load of the gas outlet flaps was adjusted to 6 kg.

[0079] Gas outlet plate: 420g / m 2 and a four-layer fiber composite with upper and lower cover layers consisting of a composite of basalt fabric with an areal weight of 300 g / m 2and two intermediate sheets of woven silicate fabric with an areal weight of 1000. The base material was a silicone resin SILRES® MK from Wacker.

[0080] The total thickness of the gas guide plate was 1.3 mm. The thickness of each of the basalt fiber composite layers was 0.35 mm, and the thickness of each of the silicate fiber composite layers was 0.3 mm.

[0081] The base plate made of fiber composite material was machined with gas outlet flaps in the form of circular segments of a 43.5 cm diameter circle and a 39 mm long circular chord forming a bent edge.

[0082] A bending strip test corresponding to FIG. 5b confirmed that the gas outlet flap formed in this way opens reliably at a load of 6 kg. [Explanation of symbols]

[0083] 1 Gas outlet plate 2 base plates 3 Gas Outlet Flap 4 Free circumference 5 Bent Edge 6 circular cells 7 Propagation circular cell 8 Gas Flow 9 Film

Claims

1. A gas outlet plate (1) with adjustable gas outlet flaps (3) for directing hot gas flows (8) emerging from vent openings of propagation battery cells (7) out of the cell area of ​​a battery module, the gas outlet plate (1) having a base plate (2) into which an array of adjustable gas outlet flaps (3) is inserted; The base plate (2) is made of a high-temperature resistant material having a high-temperature resistance of at least 600°C; The gas outflow flap (3) has a free periphery (4) that defines a flapable area, and a bent edge (5) that connects the gas outflow flap (3) to the base plate (2), the adjustable gas outlet flap (3) is designed to be opened by pressure load when a gas flow (8) impinges on it, allowing the gas flow (8) to be led out of the cell area of ​​the battery module; Gas outlet plate (1).

2. 2. The gas outlet plate (1) with adjustable gas outlet flaps (3) according to claim 1, wherein the basic shape of the gas outlet flaps (3) is circular, oval or rectangular.

3. 3. The gas outlet plate (1) according to claim 1, wherein the gas outlet plate (1) is configured as a mounting area for battery cells with ventilation openings on the bottom side for a battery module.

4. 4. The gas outlet plate (1) according to claim 1, wherein each battery cell (6) is assigned at least one gas outlet flap (3).

5. 5. The gas outlet plate (1) according to claim 1, wherein a film (9) is applied to the gas outlet plate (1) on the side facing away from the battery cell array, the film (9) being designed to break when the gas outlet flap (3) is opened.

6. 6. Use of a gas outlet plate (1) with an adjustable gas outlet flap (3) according to any one of claims 1 to 5 as a safety device for a battery module.

7. 7. The use according to claim 6, wherein the gas outlet plate (1) is a component of the housing wall of the battery module and is arranged on the side of the housing that, in the completed state, faces the vent openings of the battery cells.

8. A battery module comprising a gas outlet plate (1) with an adjustable gas outlet flap (3) according to any one of claims 1 to 5, The battery module includes an array of at least two battery cells (6) having a vent opening, and a housing that houses the battery cells (6); The gas outlet plate (1) having the gas outlet flap (3) is arranged opposite the degassing opening of the battery cell (6). Battery module.

9. 9. The battery module according to claim 8, wherein the gas outlet plate (1) forms a bottom surface, a cover surface or a lid of the battery module.

10. 10. The battery module according to claim 8 or 9, wherein the battery cells (6) are selected from cylindrical cells, prismatic cells or pouch cells.

11. A vent opening is provided at the bottom for the battery cell (6), The gas outlet plate (1) forms a mounting surface for the battery cells (6). The battery module according to any one of claims 8 to 10.

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