Vehicle with a high-voltage battery

Abstract

A vehicle includes a high-voltage battery which has a housing and at least one battery module arranged in the housing that has multiple battery cells which are electrically connected together via a cell contacting system. Each of the battery cells has a battery cell housing with an emergency degassing opening which opens at a specified cell inner pressure and through which hot or burning gas can be leaked out of the interior of the battery cell housing into the housing of the high-voltage battery in the event of a disruption or damage to individual battery cells. The emergency degassing openings face the cell contacting system and/or a wall of the housing of the high-voltage battery. The cell contacting system and/or the wall of the housing of the high-voltage battery is/are provided with a heat protection layer, at least in the regions in which the emergency degassing openings are arranged.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a vehicle having a high-voltage battery.

High-voltage batteries of electric or hybrid vehicles, such as for example the “BMW i3” vehicle, include a high-voltage battery housing having a plurality of what are known as “cell modules” (hereinafter also referred to as “battery modules”) arranged therein. Each of the cell modules or battery modules consists of a plurality of battery cells arranged consecutively in series and that are electrically connected to one another. The individual battery cells are electrically connected to one another via what is known as a “cell contact system”. Depending on whether the battery cells of a cell module are connected to one another in series or in parallel, like or opposite poles of the battery cells of a cell module are electrically connected to one another via the cell contact system.

The individual battery cells each have a battery cell housing. An emergency ventilation opening is provided in each of the battery cell housings. If, for example in the event of an extremely severe accident, battery cells are damaged and/or a short circuit takes place in or between individual battery cells and the interior of a battery cell heats up to an impermissibly great extent, “emergency ventilation” has to be possible for the affected battery cells. The emergency ventilation takes place through the emergency ventilation (degassing) opening, which may be designed for example as an intended breaking point that opens when a predefined internal cell pressure is exceeded and allows gas to escape from the interior of the battery cell. In extreme cases, such as for example in the case of massive damage to individual battery cells, in highly unfavorable constellations the leaking gas may ignite, wherein a leakage of flames into the surroundings or into the passenger compartment of the vehicle is very reliably avoided by virtue of the battery cells or the cell modules being arranged in a high-voltage battery housing. The high-voltage battery housing of the abovementioned “BMW i3” is a relatively rigid aluminum housing that is closed off “upwardly”, that is to say in the direction toward the passenger compartment, by a screwed-on cover.

The object of the invention is to provide a vehicle having a high-voltage battery that offers even greater safety with regard to possible fire hazards in comparison with vehicles having conventional high-voltage batteries.

This object is achieved by the features of the independent claim. Advantageous refinements and developments of the invention may be derived from the dependent claims.

The starting point of the invention is the observation that, in the event of extreme mechanical damage to individual battery cells and/or short circuits internal to a cell, very hot, burning gas should be able to leak from the interior of individual battery cells into the interior of the high-voltage battery via emergency ventilation openings of the battery cell housings.

The starting point of the invention is a vehicle having a high-voltage battery that has a housing “high-voltage battery housing” and at least one cell module (hereinafter also referred to as “battery module”) arranged in the housing. The cell module or battery module in turn has a plurality of battery cells electrically connected to one another via a cell contact system. The individual battery cells each have a battery cell housing having an emergency ventilation opening that opens starting from a predefined internal cell pressure. There may be provision for the cell contact system to fully or at least partly cover the emergency ventilation openings of the battery cells of the cell module in question. By virtue of the emergency ventilation openings, hot or burning gas is able to escape from the interior of the battery cell housings into the interior of the high-voltage battery housing in the event of a fault with or damage to individual battery cells. The emergency ventilation openings face the cell contact system and/or a wall of the housing.

In one aspect of the invention, the cell contact system and/or the wall of the housing of the high-voltage battery is or are provided with a heat protection layer, in particular with a heat protection coating layer, at least in those regions in which the emergency ventilation openings are arranged. A situation is thereby prevented in which hot or burning gas leaking from one or more battery cells through the emergency ventilation opening or the emergency ventilation openings impinges directly on the wall of the housing of the high-voltage battery. Hot or burning gas thus impinges initially on the heat protection layer that is provided on the cell contact system and/or on the heat protection layer that is provided in the region of the emergency ventilation openings on the inside of the wall of the housing of the high-voltage battery. Even at very high temperatures of the leaking gas (for example temperatures of more than 1000° C.), hot gas is thereby prevented, at least for a predefined duration, from burning through the wall of the housing of the high-voltage battery and leaking from the high-voltage battery housing. This contributes to a further improvement in passenger safety in electrified vehicles. A leakage of flames from the high-voltage battery housing is thus able to be prevented with even greater reliability.

Applying a heat protection layer to the cell contact system and/or the inner wall of the housing of the high-voltage battery in the region of the emergency ventilation openings is inexpensive, easily able to be applied in industry and entails only a very low additional weight.

The invention thus prevents direct impingement on the battery wall. The term “wall” of the housing of the high-voltage battery or the term “battery wall” should be understood extremely broadly. This may in principle be a lower wall, a side wall or an upper wall (for example a cover) of the housing of the high-voltage battery.

According to one development of the invention, the cell contact system is arranged between the emergency ventilation openings of the battery cells and the wall of the housing of the high-voltage battery.

According to one development of the invention, the cell contact system has an electrically conductive conductive element that is electrically connected to electrodes of a plurality of battery cells. The conductive element may be for example a conductive metal sheet (for example steel or aluminum sheet). There may be provision for the conductive element to be carried or held by a holding element. The holding element may be for example a plastic part (for example an injection-molded part). The cell contact system within the meaning of the present invention may be formed by the conductive element and/or by the holding element. The heat protection layer may accordingly be applied to the conductive element and/or to the holding element. In this case, the cell contact system acts in a manner similar to a “baffle plate” when hot or burning gas leaks from one or more battery cells, which prevents hot or burning gas from impinging directly on the material of the wall of the housing of the high-voltage battery.

According to one development of the invention, there may be provision for the heat protection layer to be an intumescent layer. Intumescent materials are known from refractory technology. If an intumescent material is exposed to a flame, the material expands significantly or swells. The volume of the intumescent material thus increases. The material thus foams or inflates and becomes porous, thereby further increasing its insulating effect and its fire-retarding effect.

According to one development of the invention, there may be provision for the heat protection layer provided on the cell contact system and/or on the wall of the housing of the high-voltage battery to be a ceramic layer or a layer that contains ceramic particles.

As already mentioned above, there may be provision for the heat protection layer to be provided only in those regions in which emergency ventilation openings are arranged, on the cell contact system and/or on the wall of the housing of the high-voltage battery. The entire cell contact system or the entire wall of the high-voltage battery housing thus does not necessarily need to be provided with such a heat protection layer. By contrast, a “local reinforcement” of the cell contact system or of the wall of the housing of the high-voltage battery with such a heat protection layer is sufficient.

By way of example, there may be provision for the heat protection layer to have a layer thickness of at least 0.1 mm.

The wall of the housing of the high-voltage battery may consist of aluminum or an aluminum sheet that is provided with a heat protection layer at least or only in the region or in those regions in which the emergency ventilation openings are arranged. By way of example, there may be provision for the emergency ventilation openings to be provided on an upper side of the battery cell housing, with respect to the direction of gravity, and for the heat protection layer to be provided on an inside or a lower side of an upper side (cover) of the housing of the high-voltage battery.

The wall of the high-voltage battery housing does not however necessarily have to consist of metal or aluminum. The wall of the high-voltage battery housing may in principle consist partly or fully of a plastic material that is provided with a heat protection layer at least in those regions in which the emergency ventilation openings of the battery cells are arranged, which heat protection layer prevents hot or burning gas from impinging on the wall in an extreme case.

As already mentioned, there may be provision for the emergency ventilation openings to be closed off in a gastight manner in the correct state of the battery cells and to open or burst open only after a predefined internal cell pressure is exceeded.

As already indicated, there may be provision for the heat protection layer to be provided on that side of the wall or of the cell contact system facing the emergency ventilation openings.

According to one development of the invention, the heat protection layer consists of a material that does not melt and not burn, or not melt and not burn for a predefined duration, at least up to a temperature of 1000° C. or 1100° C. or 1200° C. or 1300° C.

By way of example, there may be provision for the heat protection layer not to be perforated or burned by hot or burning gas that leaks from the battery cells at least for a duration of 0.5 minutes and a temperature of up to 2000° C., in particular up to a temperature of up to 1600° C.

The invention is explained in more detail below in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a first exemplary embodiment according to the invention in which a heat protection coating is provided on the cell contact system.

FIG. 2 is a schematic diagram of a second exemplary embodiment in which a heat protection coating is provided on an inside of a cover of the high-voltage battery housing.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a highly schematic illustration of a battery cell 1 that is part of a cell module (not illustrated) consisting of a plurality of such battery cells. The battery cell 1 has a battery cell housing 2. An emergency ventilation opening 2b is provided in an upper region 2a of the battery cell housing 2. In the correct state of the battery cell 1, the emergency ventilation opening 2b is closed off. The emergency ventilation opening 2b opens or breaks only when a predefined pressure in the interior of the battery cell housing 2 is exceeded. In the event of extreme mechanical damage to the battery cell housing 2 or in the event of a short circuit in the battery cell or between individual battery cells, a considerable pressure rise and the leakage of hot or burning gases through the emergency ventilation opening 2 may take place in the interior of the battery cell housing. Hot or burning gas is indicated by the reference sign 3 in FIGS. 1 and 2.

The battery cell 1 or the cell module, not illustrated in more detail here, is arranged in a housing, not illustrated in more detail here, of a high-voltage battery. Only a cover 4 of the housing of the high-voltage battery is illustrated here. The cover 4 is located in an upper region of the housing of the high-voltage battery with respect to the direction of gravity, which is indicated by an arrow 5.

A cell contact system 6, which is indicated only highly schematically here, is arranged between the cover 4 and the battery cell housing 2. Individual poles (like poles or opposite poles) of individual battery cells of a cell module are electrically connected or interconnected to one another via the cell contact system 6. In each case, the cell contact system has a conductive element, which may be formed for example by a conductive metal sheet, via which the poles of the individual battery cells of the cell module are electrically connected to one another. There may additionally be provision for the cell contact system to have a holding element that holds or carries the conductive element, which holding element may for example consist of a plastic material. In the exemplary embodiment shown in FIG. 1, a heat protection coating 7 is provided on an upper side of the cell contact system 6, for example on the holding element or a cover of the cell contact system. The heat protection coating does not necessarily have to be provided on a side facing away from the battery cell 1 or on a side facing away from the battery cells of the cell module. As an alternative or in addition, the heat protection coating may also be provided on a side of the cell contact system 6 facing the battery cell 1 or the battery cells of the cell module, that is to say on that side of the cell contact system 6 facing the emergency ventilation opening 2b.

The cell contact system 6 and in particular also the heat protection layer 7, at least for a predefined duration, prevent hot or burning gas 3 leaking from the emergency ventilation opening 2 from impinging directly on the inside or lower side of the cover 4 of the housing of the high-voltage battery.

The cell contact system 6 or the heat protection coating provided thereon or the heat protection layer 7 thus acts as a kind of baffle layer, as a result of which the risk of hot or burning gas burning through the wall of the high-voltage battery housing or through the cover 4 is significantly reduced.

In the exemplary embodiment shown in FIG. 2, the heat protection layer 7 is provided on an inside of the wall of the housing of the high-voltage battery, or here specifically on an inside or lower side of the cover 4 of the housing of the high-voltage battery.

Claims

1. A vehicle having a battery, comprising: a housing;a battery module arranged in the housing, the battery module having a plurality of battery cells; anda cell contact system that electrically connects the plurality of battery cells to one another, whereinthe battery cells each have a battery cell housing with an emergency ventilation opening which opens at a predefined internal cell pressure and through which hot or burning gas is able to escape from an interior of the battery cell housing into the housing of the battery in an event of a fault with or damage to individual battery cells,the emergency ventilation openings face the cell contact system,the cell contact system is provided with a single heat protection layer at least in regions in which the emergency ventilation openings are arranged, andthe heat protection layer consists of a heat protection coating.

2. The vehicle according to claim 1, wherein the cell contact system is arranged between the emergency ventilation openings and a wall of the housing of the battery.

3. The vehicle according to claim 1, wherein the cell contact system has an electrically conductive conductive element that is electrically connected to electrodes of a plurality of battery cells and/or a holding element that carries the conductive element, andthe heat protection layer is applied to the conductive element.

4. The vehicle according to claim 1, wherein the heat protection layer is an intumescent layer.

5. The vehicle according to claim 1, wherein the heat protection layer is a ceramic layer or a layer containing ceramic particles.

6. The vehicle according to claim 1, wherein the heat protection layer has a layer thickness of at least 0.1 mm.

7. The vehicle according to claim 1, wherein the emergency ventilation openings are closed off in a gastight manner when an internal pressure of the battery cells is less than the predefined internal cell pressure.

8. The vehicle according to claim 1, wherein the emergency ventilation openings are each formed by an intended breaking point that opens when the predefined internal cell pressure is exceeded.

9. The vehicle according to claim 1, wherein the battery cells are arranged such that the emergency ventilation openings face an upper wall, with respect to a direction of gravity, or a cover of the battery.

10. The vehicle according to claim 1, wherein the heat protection layer does not melt and does not burn up to a temperature of 1300° C.

11. The vehicle according to claim 1, wherein the heat protection layer does not melt and does not burn up to a temperature of 1000° C.

12. The vehicle according to claim 1, wherein the heat protection layer is not perforated and not burned by the hot or burning gas that leaks from the battery cells for a duration of 0.5 minutes at a temperature of up to 2000° C.

13. The vehicle according to claim 1, wherein the heat protection layer is not perforated and not burned by the hot or burning gas that leaks from the battery cells for a duration of 0.5 minutes at a temperature of up to 1600° C.

14. The vehicle according to claim 1, wherein the cell contact system has an electrically conductive conductive element that is electrically connected to electrodes of a plurality of battery cells and/or a holding element that carries the conductive element, andthe heat protection layer is applied to the holding element.