Module cover hood with integrated gas outlet for battery modules

Abstract

The invention relates to a module cover hood (1) with an integrated gas outlet for a battery module (3) consisting of battery cells (4), which has a cover plate (8) with a rupture notch (2) which is a through opening of the cover plate (8) and which is closed by a rupture disk (10) which is configured to open in the event of a load of gas (7) escaping from the battery cells (4) in the event of a thermal fault, so that the escaping gas (7) can be discharged from the battery module (3), and which is manufactured from a high-temperature resistant fiber composite material.

Description

[Technical field]

[0001] The present invention relates to a module cover hood for a battery module, which serves to reliably guide away a hot gas flow doped with electrically conductive particles that is released from a battery cell in the event of a thermal failure of the cell, thereby preventing a short circuit with the formation of an arc between the battery housing mass and a component that guides the current. [Background technology]

[0002] Vehicles with electric drives today use rechargeable battery systems, in particular lithium-ion battery cells, where several battery cells are grouped together and electrically connected to one another to form battery modules, and several battery modules are grouped together and electrically connected to one another to form battery packs.

[0003] For vehicle operation, the battery system must have a very high energy density, which on the other hand entails a high safety risk.

[0004] DE 2018125618 A1 discloses a protection unit for a reliable electrical connection of battery cells to form battery modules and battery stacks for high-voltage batteries for motor vehicles, in which a cell contact-connection system is placed on the cell terminal side of the battery cells, which consists of an electrically insulating frame and electrically conductive cell connections for the desired connection, which are introduced into the frame. Between the cell contact-connection system and the cell terminal side of the battery cells, an electrically insulating intermediate layer is located, which has cutouts for conducting the cell terminals and a row of openings for leading off hot gases. The hot gases flow out of the safety valve of the battery cell in the event of a thermal failure of the battery cell arranged below. The hot gases flowing out of the failed battery cell are led off via the openings of the intermediate layer and the corresponding cutouts of the cell contact-connection system into a receiving chamber of a battery housing, in which the battery module is arranged.

[0005] A strip-shaped electrically insulating protective mat may extend along and above the opening in the intermediate layer, which protects the current-conducting components of the high-voltage battery from hot gases and prevents fire or flames from escaping from the battery housing.

[0006] DE 10 2013 220 778 A1 describes a battery housing for a vehicle battery, for example a lithium-ion traction battery, which is made of a polymer composite material in order to reduce the weight of known housings of this kind, which are manufactured from metal. Furthermore, a battery housing made of a polymer composite material has the advantage that it is electrically insulating. The battery housing has a battery chamber and a cover for placing on the battery chamber. The cover may have at least one opening for filling the battery, two electrode feed-through openings for conducting the battery electrodes and / or a targeted breaking point for degassing the battery.

[0007] Safe operation of these battery systems is only possible up to a relatively low critical temperature value: already at approximately 80°C, oxidation processes between the components of the electrolyte and the components of the electrodes of the battery cells begin, which lead to progressive heating of the cells and ultimately to their destruction up to so-called thermal runaway, which usually results in the opening of the cells leading to rupture or explosion.

[0008] In doing so, highly flammable gases escape from the cell at high pressures, which typically ignite instantly if they come into contact with air, and have extremely high temperatures, which in turn produce conductive particles such as graphitic carbon, metallic particles, and other decomposition products of the cell contents.

[0009] For the operational safety of the battery cells, and in particular for possible vehicle occupants, it is important to avoid energy transfer to adjacent cells and modules in order to prevent, or at least as far as possible, the spread of thermal runaway. In particular, it must be prevented that gases containing conductive particles lead to short circuits between the current-carrying components and the mass of the battery pack, resulting in the formation of arcs that can generate temperatures up to several thousand degrees Celsius. Such high temperatures can no longer be controlled by currently available insulating materials and would inevitably lead to thermal runaway of the entire battery system in the shortest possible time.

[0010] For operational safety and to protect vehicle occupants, a suitable protection concept for the battery pack must ensure that no sparks or flames occur, i.e. are visible, outside the battery pack for several minutes after the first signs of thermal runaway of a battery cell are detected. This period before a flame is visible outside the battery pack should preferably not be less than 5 minutes in order to meet safety standards. Summary of the Invention [Means for solving the problem]

[0011] This is where the invention arises. The invention relates to a module cover hood with integrated gas outflow structure having the features of claim 1.

[0012] The dependent claims refer to advantageous embodiments.

[0013] The module cover hood according to the invention with an integrated gas outlet allows the hot gas flow loaded with conductive particles emerging from the overheated cells of the module to be drawn off quickly and directly from the battery pack without short circuits and arc formation between the current-carrying components and the mass of the battery pack.

[0014] Thus, the occurrence of a visible flame outside the battery pack can be prevented for at least 5 minutes, in particular at least 7 minutes or more, as required by safety regulations.

[0015] Furthermore, the module cover hood according to the invention has the advantage that it has very good three-dimensional formability during production, so that the desired shape can be obtained precisely and without great effort.

[0016] The module cover hood according to the invention allows hot gas loaded with electrically conductive particles to be conducted away from the battery module from its place of generation via the module without the electrically conductive gas forming contacts and thus short circuits between current-carrying components, such as busbars, cell connections, module connections, etc., and the mass of the battery pack. The formation of arcs is thereby avoided. The formation of arcs occurs via an electrically conductive gas phase that is formed during a thermal runaway due to a short circuit between the housing mass and the current-carrying components.

[0017] The module cover hood according to the invention is intended in particular for use with battery systems consisting of prismatic battery cells, such as are widely used today in electric vehicles, but it can of course be easily modified for other battery types, such as pouch cells or cylindrical cells.

[0018] Prismatic cells, battery modules and battery packs consisting of battery modules, and their manufacture are generally known.

[0019] The prismatic cell has a metal housing, usually made of aluminum or stainless steel, with two electrical contacts on the side, between which a safety valve is provided. As soon as the internal pressure of the cell exceeds a defined critical value, the safety valve opens, which allows a directed gas outflow. A variable number of prismatic battery cells, which can be assembled main surface to main surface, form a battery module.

[0020] The module cover according to the invention is placed over the module on the side with the safety valve. The module cover hood has a flat cover plate, the width and length of which correspond to the dimensions of the module.

[0021] If necessary, the cover plate can be adapted to the three-dimensional geometry of the mounting surface on the module, thereby making it possible, for example, to compensate for irregularities in the mounting surface on the module.

[0022] The cover plates of the module cover hood are provided with tear-away notches, which are through-openings provided in the module cover hood.

[0023] Through these rupture notches, gas can be vented from the face of the module equipped with the safety valve, and gas escapes from the cell in case of overheating of the cell and opening of the safety valve.

[0024] The number and positions of the rupture notches of the module cover hood are determined by the number of battery cells of the battery module. Furthermore, it is desirable that the gas flowing out of the safety valve of the battery cell can be quickly discharged through a short discharge path. Therefore, rationally, each safety valve is correspondingly disposed with a rupture notch of the module cover hood, and the rupture notch is located above the safety valve when the module cover hood is placed on the module. It is desirable that the circumferential shape and size of the rupture notch correspond to the dimensions of the safety valve, or preferably are larger than the safety valve.

[0025] The rupture notch is closed by a rupture disk, similar to a safety valve in a battery cell, which only opens under the action of temperature and pressure from hot gases.

[0026] This makes it possible to ensure that the gas discharge takes place directly through the cells that are propagated, while the upper rupture notches of the non-propagated cells remain closed, thereby preventing contamination in these areas with conductive particles from the hot gas and preventing bypass of the hot gas discharged from the module back into the module through the additionally open rupture notches.

[0027] The rupture notch is preferably located as close as possible above the safety valve, so that the outflow path of the gas from the battery cell to the rupture notch can be kept as short as possible. For this purpose, a depression or recess can be provided in the region of the cover plate of the module cover hood, so that this recessed region is located directly above the safety valve.

[0028] The module cover hood is made of a high-temperature resistant material, which allows reliable evacuation of hot gases without the module cover hood itself catching fire or without the module hood cover itself deforming under thermal influences. Ideally, the module cover hood is heat resistant up to at least 1400 °C.

[0029] Additionally, it is desirable for the material for the module cover hood itself to be non-conductive.

[0030] According to the invention, the module cover hood is obtained from a layer structure consisting of layers made of fiber composite material, in which high-temperature resistant fibers are used.

[0031] In particular, mineral fibres such as basalt fibres, glass fibres, silicate fibres and oxide ceramic fibres can be used.

[0032] The fibers may be present in the form of a sheet, such as a woven fabric or scrim, which itself may be made from rovings or yarns comprised of these fibers.

[0033] The extension of the fibres is preferably bidirectional, for example in particular 0° / 90°, but the extension of the fibres may vary as required and may be multidirectional, for example 0° / 90° / 45°.

[0034] The plastics used as the matrix material likewise have high heat resistance. Examples of such plastics are silicone resins, in particular those with a high SiO content, in particular those with an SiO content of 50-90%, particularly preferably 75% or more.

[0035] Silicone resins with an SiO proportion of at least 80% have proven to be particularly suitable.

[0036] As silicone resins, di- and / or tri-functional polysiloxanes may be used, preferably having methyl and / or phenyl substituents.

[0037] One example of a suitable silicone resin is SILRES® MK, sold by Wacker.

[0038] The total thickness of the module cover hood should be as small as possible with respect to the desired space saving, preferably not exceeding 1.5 mm. A thickness of 1 mm or less is advantageous in order to take into account the desired compact, space-saving construction of the battery arrangement.

[0039] The individual layers of the module cover hood may have different fibers and / or different fiber orientations.

[0040] For example, the layer structure may consist of one or two cover layers of a first fiber composite material and, depending on requirements, one or more intermediate layers of a second fiber composite material. The layers of different fiber composite materials may be arranged alternately.

[0041] The thickness of the individual layers should be as thick as necessary, but preferably as thin as possible.

[0042] Fiber composites can likewise be used as materials for the burst disc.

[0043] Examples of suitable fibres are glass fabrics or woven plastic fibres, for example made from aramid, polyphenylene ether (PPE) and polypropylene (PP), and as matrix an epoxy resin, for example based on bisphenol A, is used.

[0044] The module cover hood according to the present invention with integrated gas outlet makes it possible to delay the occurrence of flames and sparks outside the battery module in the event of a thermal runaway for at least 5 minutes, in particular for at least 7.5 minutes and even longer.

[0045] Furthermore, the module cover hood according to the present invention has excellent three-dimensional formability during production, so that a desired shape can be obtained accurately and without great effort.

[0046] The module cover hood may be contoured in three dimensions, allowing the cover plate and / or edges to conform to the surface topography of the mounting surface above the battery.

[0047] The invention is explained in more detail below on the basis of the drawings, which show the design and application of a modular cover hood according to the invention with integrated gas outlet. [Brief description of the drawings]

[0048] [Figure 1] FIG. 2 shows an arrangement for a module cover hood according to the invention with integrated gas outlet arranged on a battery module consisting of rectangular battery cells. [Diagram 2] FIG. 2 is a plan view showing a module cover hood according to the present invention. [Diagram 3] FIG. 3 is a bottom view of the module cover hood shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] FIG. 1 shows an exploded view of a module cover hood 1 according to the invention with a bursting notch 2 for a battery module 3 consisting of a number of rectangular battery cells 4 .

[0050] The module cover hood 1 is placed on the side of the module 3 which is provided with electrical contacts 5. Each battery cell 4 has a safety valve 6 between the electrical contacts 5.

[0051] The module cover hood 1 is provided with a corresponding number of rupture notches 2, and the positions of the rupture notches 2 provided on the module cover hood 1 are selected so that one rupture notch 2 is located above the safety valve 6 when the module cover hood 1 is placed on the battery module 3. That is, in the embodiment shown in FIG. 1, one rupture notch 2 is arranged to correspond to each safety valve 6.

[0052] The shape and size of the module cover hood 1 are adapted to the dimensions and shape of the module 3. The module cover hood 1 has in this embodiment a flat rectangular cover plate 8 with rectangular burst notches 2 arranged one behind the other along the longitudinal axis of the cover plate 8 and corresponding to the position of the safety valves 6.

[0053] In order to be able to hold the module cover hood 1 securely on the module 3, the cover plate 8 is provided along each long side with a downwardly directed edge 9.

[0054] In the assembled state, the cover plate 8 rests on the contact 5 as the highest ridge on this side of the battery module 3, with the edge 9 contacting the side surface.

[0055] According to one configuration, the area of ​​the cover plate 8 which comprises the rupture notch 2 may be lowered in order to keep the distance between the rupture notch 2 and the safety valve 6 as small as possible and to keep the outflow path of the gas as short as possible.

[0056] For this purpose, for example, a central region of the cover plate 8 which is provided with the burst notch 2 may be lowered compared to adjacent regions of the cover plate 8 and may form a groove extending along the longitudinal axis.

[0057] 1 shows a situation of thermal runaway of the frontmost battery cell 4 of a module 3. The hot gas flow 7 emerging from the safety valve 6 is led directly and unhindered out of the area of ​​the battery module 3 through the rupture notch 2 located above it.

[0058] For this purpose, the rupture notch 2 is made large enough so that the hot gas flow 7 emerging from the safety valve 6 located below said rupture notch 2 can be led away from the module 3 quickly and unhindered. In the embodiment shown in FIG. 1, the length and width of the rupture notch 2 are approximately twice the length and width of the safety valve 6.

[0059] It is important that the hot exiting gas stream 7 doped with conductive particles is quickly conducted away from the module 3 to avoid contact with adjacent conductive components and possible short circuits that could lead to the transfer of thermal runaway to adjacent cells.

[0060] A module cover hood 1 according to the invention is shown from above in Fig. 2 and from below in Fig. 3. As shown in Fig. 1, the cover plate of the module cover hood is provided with a row of uniform, successive burst notches 2 in the middle along the longitudinal axis corresponding to the location of the safety valves 6 of the modules 3.

[0061] The rupture notches 2 are closed on the underside of the cover plate 8 by a rupture disc 10. In the embodiment shown in FIG. 1, the rupture disc 10 extends over all the rupture notches 2 in an area manner and completely covers them.

[0062] The rupture disc 10, in this embodiment, is made from a fiberglass composite material with an epoxy resin matrix.

[0063] The rupture disc 10 can be selected to be sufficiently thin so that it opens reliably when loaded with gas, but on the other hand is preferably not flammable.

[0064] In order to illustrate the module cover hood 1 according to the invention with integrated gas outlet, FIG. 1 shows the use of the module cover hood 1 for a battery module 3 consisting of several rectangular battery cells 4, in which a safety valve 6 is provided between the electrical contacts 5.

[0065] However, it is obvious that the module cover hood 1 according to the present invention can also easily be used for different battery cell configurations, for example when the safety valve 6 occupies a position different from between the contacts 5, for example on another side of the battery housing.

[0066] Due to its good three-dimensional formability, the module cover hood 1 according to the present invention can easily adapt to irregularities such as height differences resulting from structures on the mounting surface on the battery cells or modules.

[0067] For example, the module cover hood may be configured to cover or overlay module connections that group adjacent modules together to form a module set. EXAMPLES

[0068] A flame test was carried out using a module cover hood according to the present invention.

[0069] The module cover hood is 420g / m 2 and an upper cover layer and a lower cover layer made of a composite of a basalt woven fabric having a basis weight of 300 g / m 2 The composite consisted of four layers of fiber composite with two intermediate layers of woven silicate fabric having a basis weight of 100 g / m². The matrix material was a silicone resin, SILRES® MK, from Wacker.

[0070] The total thickness of the module cover hood was 1.3 mm. The thicknesses of the basalt fiber composite layers were each 0.35 mm, and the thicknesses of the silicate fiber composite layers were each 0.3 mm.

[0071] The dimensions of the fracture notch were 70 mm x 18 mm with a web spacing of 16 mm.

[0072] Bursting disc: 164g / m 2 A glass fiber composite having a thickness of 0.1 mm was used, which consisted of a glass fabric having a basis weight of 100 g / g and a matrix consisting of an epoxy resin sold by Hexion under the trade name EPIKOTE® Resin 828 and made from bisphenol-A and epichlorohydrin.

[0073] The rupture discs were attached with adhesive DOW Corning RTV 3145.

[0074] Flame tests showed that a rupture disc having a thickness of 0.1 mm opens quickly enough when a flame is applied, and in this case the rupture discs of the adjacent rupture notches are not damaged. [Explanation of symbols]

[0075] 1 Module cover hood 2. Rupture notch 3 Battery Module 4 Battery Cells 5 Electrical Contacts 6. Safety valve 7 Gas Flow 8 Cover Plate 9 Edge 10 Bursting Disc

Claims

1. A module cover hood (1) with an integrated gas outlet for a battery module (3) consisting of battery cells (4), the module cover hood (1) has a cover plate (8), a rupture notch (2) is located in the cover plate (8), the rupture notch (2) is a through opening of the cover plate (8), and the rupture notch (2) is closed by a rupture disc (10), the rupture disc (10) is configured to open when gas (7) flowing out of the battery cells (4) is loaded, so that the gas (7) can be guided out of the battery module (3); A module cover hood (1), wherein the module cover hood (1) is manufactured from a high temperature resistant fiber composite material.

2. 2. The module cover hood (1) according to claim 1, wherein the rupture notch (2) of the cover plate (8) is positioned so as to be above the safety valve (6) of the battery cell (4) when placed on the battery module (3).

3. 3. The module cover hood (1) according to claim 1 or 2, wherein the rupture disk (10) is provided on the underside of the cover plate (8) facing the battery module (3).

4. 4. A module cover hood (1) according to claim 3, wherein the rupture disc (10) extends integrally across all rupture notches (2) provided in the cover plate (8) and closes said rupture notches (2).

5. 2. The module cover hood (1) according to claim 1, wherein the module cover hood (1) is formed to cover a battery module (3) consisting of rectangular battery cells (4).

6. 2. The module cover hood (1) according to claim 1, wherein the fiber material for the fiber composite material is a mineral fiber selected from basalt fiber, glass fiber, silicate fiber or oxide ceramic fiber.

7. 2. The module cover hood (1) according to claim 1, wherein the module cover hood (1) is manufactured from two or more layers of fiber composite material.

8. 8. A modular cover hood (1) according to claim 7, wherein one or more layers of the layer structure are made from different fiber composite materials.

9. 2. The module cover hood (1) according to claim 1, wherein the matrix of the fiber composite material is a silicone resin having an SiO content of 50 to 90%.

10. 2. A modular cover hood (1) according to claim 1, wherein the cover plate (8) and / or the edge (9) are three-dimensionally contoured.

11. 10. Use of a module cover hood (1) according to claim 1 for a battery module (3) consisting of prismatic battery cells (4) for an electric vehicle.

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