Battery cell

Abstract

The invention relates to a battery cell (2) having a housing (4) and a plurality of battery cells (6) accommodated in the housing and at least one degassing structure (16) arranged on a housing side (14, 36, 38) of the housing (4), wherein at least one thermally stable thermal protection barrier (10) is integrated as a partition layer in the housing (4), which divides the housing interior into at least two chambers (12), wherein in each chamber (12) a cell stack (8) composed of battery cells (6) is accommodated, wherein the degassing structure (16) has a number of degassing chambers (22) corresponding to the number of chambers (12) and a gas guide channel (24) which can be coupled to the degassing chambers (22), wherein each chamber (12) has a degassing opening (28) which opens into the associated degassing chamber (22), wherein the gas guide channel (24) has a gas outlet opening (26) which is directed towards the environment, and wherein a valve (30) is respectively provided between the degassing chamber (22) and the gas guide channel (24).

Description

TECHNICAL FIELD

[0001] The invention relates to a battery unit having a housing and a plurality of battery cells accommodated in the housing. Furthermore, the invention relates to a vehicle battery having such a battery unit. BACKGROUND

[0002] Electrically or electrically drivable motor vehicles, such as electric vehicles, hybrid vehicles, plug-in vehicles or fuel cell vehicles, generally comprise an electric motor by means of which one or both vehicle axles can be driven. In order to provide electrical energy, the electric motor is generally connected to a (high-voltage) battery within the vehicle as an electrical energy store.

[0003] Electrochemical cells are understood in particular here and below as so-called secondary batteries of motor vehicles In such (secondary) vehicle batteries, the consumed chemical energy can be recovered by means of a charging process. Such vehicle batteries are designed, for example, as electrochemical accumulators, in particular as lithium-ion accumulators.

[0004] In order to generate or provide a sufficiently high operating voltage, such vehicle batteries generally have at least one battery module (battery cell module) in which a plurality of individual battery cells are modularly connected or interconnected. Alternatively, a so-called Cell2Pack design (moduleless design) is possible, in which the battery cells are directly connected together, in particular in parallel, as a vehicle battery and are not previously combined as a module.

[0005] In order to reduce current heat losses, the connected battery modules or battery cells have as small an internal resistance as possible. However, due to the lower internal resistance, a relatively high short-circuit current occurs in the event of an electrical short circuit. Here, due to the high packing and energy density in vehicle batteries, there is a risk that, for example, due to an internal short circuit or overload of a battery cell, an ever-increasing chain reaction occurs, which is referred to as thermal runaway (thermal propagation).

[0006] Thermal runaway is an exothermic chemical reaction in which, on the one hand, a high thermal energy is released and, on the other hand, gas is additionally formed in the associated battery cell, in particular due to the decomposition of the electrolyte, as a result of which a high internal pressure acts in the battery cell. Due to the internal pressure, the battery cell can deform, burn or even explosively discharge the gas pressure. Such a thermal runaway or such a burning due to a self-ignition of the vehicle battery can also occur, for example, in the event of a vehicle accident or a vehicle crash when the battery system is damaged.

[0007] Therefore, in vehicle batteries, the fire prevention or fire retardation with regard to a self-ignition or thermal runaway is of particular importance for the operational safety and for the protection of the general public. It is necessary here, for example due to legal regulations, to warn the vehicle user or vehicle passenger in good time in the event of a self-ignition of the vehicle battery. It is particularly necessary here to give a certain minimum time, for example five minutes, between the warning and the visible flame or ignition of the vehicle battery, that is to say between the warning and the risk to the vehicle user, in order to enable the vehicle user to evacuate safely and reliably.

[0008] The gas flow (gas volume flow) out of the battery cell has a high volume flow and a high (gas) temperature. The gas flow contains combustible, electrically conductive and heat- generating substances / particles. The risk here is that, when the gas flow reaches high-voltage components, for example module connectors, the heat- generating and electrically conductive particles contained in the gas flow act to create further electrical short circuits, so that the fire continues to spread.

[0009] It is necessary for this purpose to lead the stronger gas flow out of the battery module in such a way that it does not lead to a fire in the battery module and does not form a visible flame. It is possible for this purpose, for example, to use heat-resistant and electrically insulating materials, for example mica or mica powder, in the interior of the vehicle battery or battery module to cover and shield over a large area, so that the gas and particles formed do not come into contact with components at risk of short circuits.

[0010] The introduction of heat-resistant and electrically insulating coverings and shields disadvantageously requires a relatively high structural space requirement, so that the energy density of the vehicle battery is reduced in the same structural space. Furthermore, additional material costs arise due to the additional components and mounting steps necessary during assembly of the vehicle battery.

[0011] A vehicle battery having a battery housing in which at least one battery module having a plurality of battery cells is accommodated is known from DE 10 2018 132 035 A1. A pressure compensation element with a membrane is arranged in a wall of the battery housing, the membrane being designed to be permeable to air and impermeable to water. Furthermore, the vehicle battery has a ventilator by means of which air can be caused to flow out of the housing interior space to the environment.

[0012] DE 10 2014 203 133 A1 discloses a device for temperature regulation and degassing of battery cells. The device has a temperature regulation apparatus for regulating the temperature of the battery cells by means of a temperature regulation means and a gas collection apparatus for collecting harmful gases of the battery cells, and a transfer apparatus which is communicatively connected to the temperature regulation apparatus and the gas collection apparatus for transferring thermal energy between the collected harmful gases and the temperature regulation means, wherein a degassing apparatus is communicatively connected to the transfer apparatus. SUMMARY

[0013] The technical problem addressed by the present application is to provide a particularly suitable battery unit. In particular, a battery unit should be provided which is as compact as possible in terms of structural space, wherein hot gases resulting from a thermal runaway do not lead to combustion and visible flames as far as possible. The technical problem addressed by the present application is also to provide a particularly suitable vehicle battery.

[0014] The technical problem is solved according to the application by a battery unit in terms of the battery unit and by a vehicle battery of an electrically driven or electrically drivable motor vehicle in terms of the vehicle battery. The advantages and design solutions explained in relation to the battery unit can also be transferred to the vehicle battery according to the application and vice versa.

[0015] The battery unit according to the application has a housing and a plurality of battery cells accommodated in the housing and at least one degassing structure arranged on a housing side of the housing for guiding (outwardly) and / or cooling gases (gas flow, gas volume flow) flowing out of the battery cells in the course of a thermal runaway. The battery unit is understood here and below in particular as a combination of battery cells, for example a battery module or a Cell2Pack vehicle battery. The battery unit is designed here in particular as an energy store of an electrically driven or electrically drivable motor vehicle. The battery cells are designed for example as lithium-ion battery cells. The battery cells preferably have a Pouch-Format, the battery cells are designed for example as soft pack cells, so that a particularly compact arrangement of the battery cells inside the housing is achieved.

[0016] According to the application, at least one thermally stable thermal protection barrier is integrated in the housing as a partition wall, which divides the interior space of the housing into at least two chambers or sub-interior spaces. In other words, at least one thermal protection barrier is provided, which extends substantially along the entire length of the housing side of the housing. The housing preferably has a plurality of chambers of identical size, wherein adjacent chambers are each separated from one another by means of a thermal protection barrier. In each chamber, a cell stack (cell pair) composed of battery cells is accommodated. This means that the battery cells are grouped into cell stacks and are arranged distributed in the chambers. In other words, a plurality of battery cells is divided into a plurality of cell stacks, the number of which corresponds to the number of chambers. Here, the battery cells are preferably divided uniformly into the chambers. By means of the thermal protection barrier, the propagation of a thermal runaway in the interior of the housing is prevented or suppressed, since the hot gas flow flowing out of the associated battery cells is shielded with respect to the adjacent cell stacks.

[0017] The thermal protection barrier is designed as a thermal, or rather, thermal, barrier between the chambers. The thermal protection barrier is here made, for example, of silicone, mica or mica powder. The thermal protection barrier is preferably designed to be electrically insulating. The chambers can here be fluidically or pressure-tightly separated by means of the thermal protection barrier. Alternatively, the chambers are open, for example, in the region of the single-cell stacks that are in electrical contact with one another and are thus connected in a flow-technological manner.

[0018] The degassing structure according to the application has a number of degassing chambers corresponding to the number of chambers, which can be coupled to the gas-conducting channel. The gas-conducting channel of the degassing structure has a gas outlet opening towards the environment of the battery cell. Here, each chamber of the housing is coupled to a respectively assigned degassing chamber of the degassing structure. To this end, each chamber has a degassing opening into the respective degassing chamber as a flow- or fluid-technological connection. A valve is respectively arranged between the degassing chamber and the gas-conducting channel. A particularly suitable battery cell is thus formed.

[0019] According to the application, the housing is substantially fluidically and pressure-tightly closed, in addition to the plurality of degassing openings that connect the chambers to the degassing chambers. In other words, the housing has a defined number of openings towards the degassing structure. Here, the degassing structure is structurally provided with a defined number of individual degassing chambers for the battery cells or single-cell stacks, which allow the release of gas from the housing, preferably only from the housing, by means of the valves, and thus substantially prevent the ingress of hot gases at other locations.

[0020] In the event of a thermal runaway of a battery cell, a Brandschutz, or flame protection, of the battery cell of the other single-cell stacks is achieved by means of the thermal protection barrier integrated in the housing The gas flow from the damaged single-cell stack can thus substantially only propagate in the respective chamber and in the assigned degassing chamber. However, substantially the entire gas-conducting channel is available for the cooling gas flow from the perspective of the degassing openings. A diffuser structure for guiding the gas flow is thus achieved, in which the flow cross section increases in the flow direction of the flowing gas. The gas flow is thus slowed down and thus cooled, i.e. the gas temperature is reduced. In addition, the gas flow is further cooled when flowing along the gas-conducting channel.

[0021] The gas-conducting channel preferably has a sufficient (channel) length here such that the gas stream flowing out of the battery cell is cooled to a temperature below the ignition temperature of the gas by the time it reaches the gas outlet opening. In a preferred embodiment, the gas-conducting channel here extends substantially over the entire housing side of the housing. In other words, the gas-conducting channel extends substantially over the entire surface of the housing. The gas outlet opening of the gas-conducting channel is arranged substantially opposite the degassing opening on the housing side. The entire housing surface is thus used for cooling the gas stream, which advantageously reduces the structural space requirement for the degassing structure and thus for the battery cell. A particularly small structural space degassing structure is thus achieved. A particularly compact battery cell with reliable flame- or fire- retardant properties is thus achieved.

[0022] The gas-conducting channel can here be designed straight or curved or meandering, for example, labyrinth-shaped. The length of the gas-conducting channel is increased by a curved or meandering course, thus improving the cooling of the gas stream. The flow diameter of the gas-conducting channel is here, however, preferably always designed with respect to the maximum gas pressure expected, so that the gas stream does not accumulate in the gas-conducting channel. The "maximum gas pressure expected" is understood here, in particular, as the gas pressure expected in the event of a complete thermal runaway of all battery cells. This means that the flow diameter or the size of the flow cross section of the gas-conducting channel is designed for the maximum possible fault case.

[0023] In an advantageous extension, the valve is designed as a check valve, i.e. a one-way valve or a non-return flap. It is thus ensured that the valve only opens in the direction of the gas-conducting channel. It is thus prevented that the gas stream flowing out of the degassing chamber enters an adjacent degassing chamber. This means that the valve is suitable and designed for preventing the reflection of hot gas streams into the housing.

[0024] In a suitable design, the degassing chambers are separated from one another by means of pressure- and / or fluid-tight separating walls. It is thus achieved that the degassing chambers and the chambers are reliably isolated in terms of flow technology.

[0025] An additional or further aspect of the application provides that the gas-conducting channel has at least one batten for achieving mechanical stabilization and gas conduction, which batten extends along the gas-conducting channel or the housing side.

[0026] In a conceivable design, the housing side on which the degassing structure is arranged is designed as a housing cover of the housing. A particularly simple battery cell is thus achieved. The housing cover and the degassing structure can here, in particular, be designed as a prefabricated assembly, which can be mounted on a pot-shaped, bowl-shaped or trough-shaped housing part to form the housing or the battery cell. The assembly of the battery cell is thus simplified.

[0027] In other embodiments, for example, two degassing structures are provided, which are arranged on opposite housing sides of the housing. Here, the degassing structures are, for example, assigned to different chambers. This means that a first degassing structure is used for degassing a first number of chambers, wherein a second degassing structure is used for degassing a second number of chambers. The flow diameter required for the gas-conducting channel is thereby effectively halved. In other words, the two degassing structures or the gas-conducting channel have a reduced structural size compared to a single degassing structure, whereby the structural unit has essentially the same compact structural specification for one or two degassing structures.

[0028] The vehicle battery according to the application is specified, suitable and provided for electrically driven or electrically drivable motor vehicles, for example electric vehicles or hybrid vehicles. The vehicle battery here has a battery unit as described above. The battery unit here is, for example, designed as a battery module, wherein the housing is accordingly a (battery) module housing. BRIEF DESCRIPTION OF DRAWINGS

[0029] Embodiments of the application are explained in more detail below with reference to the drawings. In the drawings, in schematic and simplified views:

[0030] Figure 1 A battery unit with a battery housing and a degassing structure is shown in a perspective view;

[0031] Figure 2 A battery unit is shown in a sectional view;

[0032] Figure 3 A degassing structure is shown in a top view;

[0033] Figure 4 A degassing structure according to the application during degassing is shown in a top view; Figure 3

[0034] Figure 5 An alternative embodiment of a degassing structure is shown in a top view;

[0035] Figure 6 A battery unit of a second embodiment is shown in a perspective view;

[0036] Figure 7 A battery unit of a third embodiment is shown in a perspective view.

[0037] In all the figures, the respective components and dimensions are always provided with the same reference numerals. DETAILED DESCRIPTION

[0038] Figure 1 ​A battery cell 2 designed as a battery module for a not further shown vehicle battery is shown in the figures. The battery cell 2 has a housing 4 and a plurality of battery cells 6 accommodated in the housing. The battery cells 6 are combined or grouped into a plurality of cell stacks 8. In the figures, four battery cells 6 are exemplarily combined into one cell stack 8 each, wherein five adjacent cell stacks 8 are shown. The battery cells 6 and the cell stacks 8 are only exemplarily provided with reference numerals in the figures. The battery cells 6 are designed as lithium-ion cells of pouch format, i.e. as pouch cells, for example. Figure 1 and Figure 2 In the figures, four battery cells 6 are exemplarily combined into one cell stack 8 each, wherein five adjacent cell stacks 8 are shown. The battery cells 6 and the cell stacks 8 are only exemplarily provided with reference numerals in the figures. The battery cells 6 are designed as lithium-ion cells of pouch format, i.e. as pouch cells, for example.

[0039] The cell stacks 8 are isolated from one another in the housing by thermal protection barriers 10 each. The thermal protection barriers 10 are arranged in the housing 4 in the manner of partition walls, such that five chambers 12 for accommodating one cell stack 8 each are formed inside the housing 4, for example. The chambers 12 are only exemplarily provided with reference numerals in the figures.

[0040] The housing 4 has a housing side 14 as a housing side 14 on which a degassing structure 16 is mounted. The degassing structure 16 is specified and adapted and provided for guiding (outwardly leading) and / or cooling a gas stream 20 flowing out of the battery cells 6 in the course of a thermal runaway 18.

[0041] The degassing structure 16 has a number of degassing chambers 22 corresponding to the number of chambers 12, which can be coupled with a gas guiding channel 24 (see Figures 3 to 5 ). Five degassing chambers 22 are shown in Figure 2 , wherein only four degassing chambers 22 are exemplarily shown in the view of Figures 3 to 5 .

[0042] The gas guiding channel 24, which is shown in Figure 3 , for example, has a gas outlet opening 26 towards the environment of the battery cell 2. Each chamber 12 of the housing 4 is coupled here with a corresponding assigned degassing chamber 22 of the degassing structure 16. To this end, each chamber 12 has a degassing opening 28 into the corresponding degassing chamber 22 as a flow or fluid-technical connection. The degassing chambers 22 are separated from one another by a pressure- and / or fluid-tight partition wall 29.

[0043] In the degassing structure 16, a valve 30 is arranged between the degassing chamber 22 and the gas guiding channel 24 each. The valve 30, which is only exemplarily provided with a reference numeral, is designed as a non-return valve, i.e. as a one-way valve or non-return flap.

[0044] Here, the gas guide channel 24 has a sufficient (channel) length such that the gas stream 20 flowing out of the battery cell 6 cools down to a gas temperature below its ignition temperature when reaching the outlet opening 24. The gas guide channel 24 here extends substantially over the entire housing side 14. In other words, the gas guide channel 24 extends substantially over the entire surface of the housing 4. The gas outlet opening 24 is thus arranged opposite the degassing opening 28 on the housing side 14. The gas guide channel 24 has two side walls 32 and a central batten 34 for realizing a mechanical stabilization of the degassing structure 16 and for guiding the gas.

[0045] In the event of a thermal runaway 18, a fire retardation or fire prevention of the battery cell 6 of the further cell stack 8 is realized by the heat protection shield 10 integrated in the housing 4. The gas stream 20 flowing out of the damaged cell 6 flows from the chamber 12 into the associated degassing chamber 22. The pressure in the degassing chamber 22 thereby increases, so that the valve 30 opens and the gas stream 20 can flow out into the gas guide channel 24 (cf. Figure 4 ). Thus, substantially the entire gas guide channel 24 is available for cooling the gas stream 20 from the perspective of the degassing opening 28, wherein the valve 30 prevents a backflow of the gas stream 20. A diffuser structure for guiding the gas stream 20 is thereby realized, wherein the flow cross section increases in the flow direction of the flowing gas. Thereby, the gas stream 20 slows down and is thus cooled, wherein the gas stream 20 is further cooled when flowing along the gas guide channel 24.

[0046] Figure 5 An alternative embodiment of the gas guide channel 24 is shown. In this embodiment, the side walls 32 are designed to be meandering or curved, thus forming a curvilinear or meander-like course of the gas guide channel 24. Thereby, the flow distance of the gas stream 20 within the degassing structure 16 is increased, whereby the cooling of the gas stream 20 can be improved.

[0047] Figure 6 A second embodiment of the battery unit 2 is shown, wherein the degassing structure 16 is arranged on a lateral housing face or housing side 36. In Figure 7 A third embodiment of the battery unit 2 is shown, wherein two degassing structures 16 are arranged on opposite housing sides 36, 38.

[0048] The claimed invention is not limited to the previously described embodiments. Rather, the person skilled in the art can also derive further variants of the invention from the disclosure within the scope of the disclosed claims without departing from the technical teaching of the claimed invention. In particular, the individual features described in connection with the different embodiments can also be combined in other ways within the scope of the disclosed claims without departing from the technical teaching of the claimed invention.

[0049] List of reference signs

[0050] 2 battery cell

[0051] 4 housing

[0052] 6 battery cell

[0053] 8 cell stack

[0054] 10 thermal protection barrier

[0055] 12 chamber

[0056] 14 housing side

[0057] 16 outgassing structure

[0058] 18 thermal runaway

[0059] 20 gas flow

[0060] 22 outgassing chamber

[0061] 24 gas guiding channel

[0062] 26 gas outlet opening

[0063] 28 outgassing opening

[0064] 29 partition wall

[0065] 30 valve

[0066] 32 side wall

[0067] 34 web

[0068] 36, 38 housing side

Claims

1. A battery unit (2) comprising a housing (4) and a plurality of battery cells (6) accommodated in the housing, and at least one degassing structure (16) arranged on a housing side (14, 36, 38) of the housing (4), -in, At least one thermally stable heat protection barrier (10) is integrated into the housing (4) as a barrier layer, said heat protection barrier dividing the housing interior into at least two chambers (12). wherein a cell stack (8) consisting of battery cells (6) is inserted into each chamber (12), wherein the degassing structure (16) comprises a number of degassing chambers (22) corresponding to the number of chambers (12) and a gas-conducting channel (24) which can be coupled to the degassing chambers (22), wherein the degassing chambers (22) are arranged at one end of the housing side and the gas-conducting channel (24) extends from the degassing chambers (22) to the other end of the housing side, wherein each chamber (12) has a degassing opening (28) which opens into the associated degassing chamber (22), - wherein the gas-conducting channel (24) has a gas outlet opening (26) toward the environment, and - wherein a valve (30) is respectively arranged between the degassing chamber (22) and the gas guiding channel (24).

2. The battery cell (2) according to claim 1, It is characterized by: The gas-conducting channel (24) extends substantially over the entire housing side (14, 36, 38) of the housing (4).

3. The battery cell (2) according to claim 1, It is characterized by: The valve (30) is designed as a non-return valve.

4. The battery cell (2) according to claim 1, It is characterized by: The degassing chambers (22) are separated from one another by means of pressure-tight partition walls (29).

5. The battery cell (2) according to claim 1, It is characterized by: At least one strip (34) for mechanical stabilization and gas guidance extends along the gas guidance channel (24).

6. The battery cell (2) according to claim 1, It is characterized by: The housing side (14) on which the degassing structure (16) is arranged is designed as a housing cover of the housing (4).

7. The battery cell (2) according to claim 1, It is characterized by: Two degassing structures (16) are arranged on opposite housing sides (36, 38) of the housing (4).

8. The battery cell (2) according to claim 1, It is characterized by: The battery cell (6) has a soft pack specification.

9. The battery cell (2) according to claim 1, It is characterized by: The battery unit (2) is designed as a battery module for a vehicle battery.

10. A vehicle battery for an electrically driven or electrically drivable motor vehicle, comprising a battery cell (2) according to one of claims 1 to 9.

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