CN113937399A

CN113937399A - Battery module, motor vehicle having a power cell and method for producing a battery module

Info

Publication number: CN113937399A
Application number: CN202110793927.5A
Authority: CN
Inventors: S·施陶登迈尔
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2020-07-14
Filing date: 2021-07-13
Publication date: 2022-01-14
Also published as: DE102020118542B3

Abstract

The invention relates to a battery module (10) having at least two battery cells (20) which are arranged as a cell stack (11) in a common module housing to form the battery module (10). In the cell stack (11), cell separating elements (31) are arranged between two adjacent battery cells (20) in each case, which are designed to deform as a function of the expansion state of the battery cells (20). For monitoring the expansion state, the battery module (10) further comprises a monitoring device (40) having a pressure sensor (30) for detecting a pressure signal corresponding to the expansion state. For the capacitive detection of the pressure signal, the pressure sensor (30) is designed as a pressure-sensitive membrane with a plurality of layers according to the plate capacitor principle. Furthermore, the individual separating elements (31) form a dielectric for the pressure sensor (30) as one of the layers of the membrane.

Description

Battery module, motor vehicle having a power cell and method for producing a battery module

Technical Field

The invention relates to a battery module having at least two battery cells, which are arranged as a cell stack in a common module housing for forming the battery module. In addition, in the cell group, a cell separating element is arranged between each two adjacent battery cells and/or between the respective battery cell and the module housing. The cell separation member is configured to be deformed according to the expanded state of the battery cells. In order to monitor the expansion state, the battery module further comprises at least one monitoring device having a pressure sensor for detecting or measuring a pressure signal corresponding to the expansion state.

The invention also relates to a motor vehicle having a power cell comprising at least one battery module as described above.

The invention also relates to a method for producing such a battery module. At least two battery cells for forming a battery module are arranged as a cell group in a common module housing. In addition, for the cell group, cell separating elements which can be deformed according to the expansion state of the battery cells are provided between two adjacent battery cells and/or between the respective battery cell and the module housing when the cell group is arranged. In addition, in order to monitor the expansion state of the battery module, the above-described monitoring device is provided with a pressure sensor for detecting a pressure signal corresponding to the expansion state when mounted in the module case.

Background

A battery module in the sense of the present invention is in particular a rechargeable electrochemical energy accumulator or accumulator. It can be used, for example, in a power battery for a motor vehicle, i.e., for example, an electric drive of an electric or hybrid vehicle. A respective battery module or cell module usually comprises a plurality, i.e. two or more, of the above-mentioned battery cells. In the case of large cells, which are known, for example, for use in power batteries, 8 to 16 cells are used, for example, in battery modules. Of course, it is also possible here to use more than 16 battery cells, which is achieved in particular in so-called prismatic cells or so-called soft-pack cells. However, in the case of small round cells or button cells, i.e., battery cells having a cylindrical shape, battery modules having hundreds of battery cells are also known.

Such battery cells generally each comprise a galvanic cell, which is designed as an electrochemical cell and is arranged in a cell housing. The individual housing can be designed, for example, substantially rectangular or square. Alternatively, any other geometry of the monolithic housing may be considered. The galvanic cell usually has two or more electrodes which are led out of the cell housing as cell terminals of the battery cell. These electrodes each form a so-called potential connection of the galvanic cells and interact via the electrolyte. The galvanic cell can be used to supply electrical energy in the form of a direct voltage, depending on the electrochemical properties of the galvanic cell. The dc voltage may be, for example, 1.2 volts to 4.5 volts, depending on the monomer chemistry. The galvanic monomer may be configured as a lithium ion monomer or a lead acid monomer or a nickel metal hydride monomer or a lead colloid monomer, for example. By now electrically connecting a plurality of such battery cells, for example, at least partially in series, to a galvanic cell, the aforementioned battery module can be realized, with which a relatively large direct voltage, for example, in the range from 10 volts to 100 volts, can be provided. The value of the battery module voltage provided here depends in particular on the number of battery cells connected in series.

However, to form a battery module, the battery cells are not only electrically connected to one another, but are usually also physically arranged in a common module housing as a cell stack. In particular, a stack is understood here to mean that the individual cells are arranged flush next to one another on one side. In the installed position of the battery module, therefore, a horizontal stacking direction of the battery cells (perpendicular to the vertical direction of the vehicle) is formed in particular in the cell stack in order to operate as a power cell as intended.

The cells "grow" over their useful life due to electrochemical reactions of the galvanic cells within the respective cells. That is to say, the battery cell deforms, i.e. in particular expands or increases in volume. In addition, the monomer "breathes" during each charge and/or discharge. This means that the battery cell slightly expands and contracts again during each charge and discharge process. These deformation processes are generally referred to as so-called Swelling (Swelling). The expansion, i.e., swelling, of the battery cells generally occurs mainly in the horizontal direction, i.e., in the stacking direction described above. As a result, with the module housing geometry remaining almost unchanged, the forces and/or pressures in the module housing increase as a result of the compression during the service life of the battery cells or during the service life of the battery cells when the battery cells expand. This can accelerate the aging of the battery cell and/or can lead to a cell failure. It is in the event of a fault, i.e. when one of the battery cells malfunctions or breaks down, that spontaneous swelling or expansion and thus a spontaneous pressure increase in the cell module can lead to a breakdown of the individual cells or of the entire battery module. Additionally or alternatively, a malfunction or malfunction of the battery cells can also lead to a negative pressure, i.e. a reduction of the pressure in the module housing. This occurs, for example, when an overpressure valve or "vent" opens in a so-called prismatic cell. The battery cells shrink in particular. In the present application, the above-described expansion or contraction process is summarized for the sake of simplicity as the term "expansion" or "expansion behavior".

In order to avoid such malfunctions and to achieve a pressure equalization in the module housing, in the cell group, in each case a respective cell separation element or a cell separation device is usually mounted between two adjacent battery cells and additionally or alternatively also between the respective battery cell and the module housing, in particular in the stacking direction. Such cell separation elements therefore usually act as a mat or gasket which is built-in between two adjacent battery cells in a cell stack, i.e. in the cell gap. In addition or alternatively, it is also possible to provide a respective cell separation element or separation element at the edge of the cell stack, i.e. in the adjoining space between the respective battery cell and the module housing (module housing gap). Corresponding cell separation elements are usually used to compensate for the mechanical expansion of the battery cells. Another function may be thermal decoupling of the cells. In other words, the cell separation elements deform together with the respective expansion state, i.e. during respiration or deformation of the individual battery cells. A monolithic separation element can therefore be understood as an elastically or plastically deformable spacer. This makes it possible to compensate for deformations of the battery cells in the cell stack and thus to achieve a pressure or force equalization in the module housing.

However, in order to be able to replace individual battery cells or battery modules in advance, i.e. in particular before damage occurs, the aforementioned monitoring devices are used in addition to the cell separation elements. The pressure in the module housing is monitored by measuring and evaluating the corresponding pressure signal by means of one or more pressure sensors or one or more force sensors. This evaluation therefore allows the corresponding expansion state of the battery cell to be inferred.

For this purpose, for example, DE 102012016022 a1 discloses an inverter cell, for example a battery cell, whose electrochemical inverter components are accommodated in a cell housing. For monitoring the converter component, a functional device with a functional element, for example a pressure sensor, is integrated inside the single-piece housing. The functional elements can be mounted, for example, on a flexible film as a circuit board and in particular on the inner wall of the housing of the individual parts. The above-described monitoring device is thus integrated into each cell itself.

Furthermore, DE 102013113909 a1 discloses a battery cell having a cell housing, which has a hole in the housing surface. The sensor module is mounted on the aperture by a sealed package. In order to detect pressure changes in the battery cell, the sensor module comprises a pressure-sensitive membrane between the aperture and the enclosure, which membrane is deformable due to different pressures on opposite sides of the membrane. This deformation can be measured by means of an electronic pressure sensor of the sensor module. Therefore, in order to measure the pressure of the corresponding battery cell, the hole of the case needs to be broken. Thereby, gas may flow out from the inside of the monomer.

Document WO 2019/051519 a1 also discloses a battery comprising a cooling device covering the battery from one or more sides or arranged between the cells, and a plurality of cells. The cooling device includes cooling channels incorporated in a single or multi-layer film. For monitoring the individual cells, a respective sensor element is also arranged, for example printed, on the membrane for each individual cell. The individual sensor elements may be, for example, capacitive pressure sensors.

However, the above-described prior art has the disadvantage that, for pressure monitoring of the battery module, only point-type measurements with a plurality of individual sensors (one sensor element for each cell) are always necessary. This results in high computation costs, in particular in the evaluation of the measurements of the individual sensors. Thus, pressure monitoring is often very costly. Furthermore, a large wiring cost is required for mounting the respective sensors. This technique is therefore particularly too expensive for mass production. In addition, the point-type measurement, i.e., the usually very small surface area of the individual sensors, has the disadvantage that the monomer pressure can be determined only in a small region. It is therefore difficult or impossible to determine irregularities in the expansion behaviour/expansion characteristics, i.e. irregularities in the expansion of one of the monomers. Furthermore, the pressure sensors constructed according to the prior art described above also have the disadvantage that they must always be installed as an additional or separate component in the cell stack or in the battery housing. As a result, the space requirement or the installation space requirement for the cell stack increases and in particular the weight of the battery module increases.

Disclosure of Invention

The object of the invention is to provide a pressure monitoring system for a battery module of this type, in which the installation space requirement can be reduced and costs can be saved compared to the prior art.

This object is achieved by the subject matter of the independent claims. Advantageous developments of the invention are disclosed in the dependent claims, the following description and the drawings.

In conjunction with such a battery module, it is provided that the pressure sensor is designed as a multilayer, pressure-sensitive membrane according to the principle of a plate capacitor for capacitively detecting the pressure signal. The individual separating elements form the dielectric of the pressure sensor as one of the individual layers of the membrane.

This design of the pressure sensor is of course also suitable for the at least one battery module, which is used in motor vehicles of this type to form a power cell. Preferably, the motor vehicle is designed as a motor vehicle, in particular as a passenger car or a truck, or as a passenger bus or a motorcycle.

In conjunction with this type of method for producing a battery module, it is therefore proposed that, for the capacitive detection of a pressure signal, the pressure sensor be provided as a multilayer, pressure-sensitive membrane according to the principle of a plate capacitor. The dielectric for the pressure sensor is provided here by means of a single separating element as one of the layers of the membrane. In the production of the battery module, the cell separating elements and the pressure sensors are therefore arranged in a common arrangement process or arrangement step between at least two adjacent battery cells and/or between the respective battery cell and the module housing in a cell stack.

The individual separating elements are therefore an integral component of the pressure sensor as a whole. This results in the advantage that the individual separating elements can be used for pressure sensing or pressure measurement in addition to their original function of pressure or force equalization in the module housing. The installation space requirement of such a pressure sensor for pressure monitoring can thereby be kept small and the costs for installing and using the pressure sensor are thereby also saved.

The measuring principle of the pressure-sensitive membrane as a pressure sensor is based here on a capacitive pressure measurement, which is carried out in particular by a change in the distance of two capacitor plates, which will be referred to in more detail below. Therefore, the pressure-sensitive film is also referred to below as a capacitor film or a measuring film. The distance change occurs here as a result of swelling, i.e. deformation of the battery cells. That is, the membrane, and thus the capacitor plates of the capacitor, are compressed due to the expansion, which can be measured by the change in capacitance of the capacitor membrane.

As is known, the capacitance C of a plate capacitor is given by the product of the so-called dielectric constant ∈ and the area a of the capacitor plates, divided by the distance d of the capacitor plates. Thus, a change in distance, such as a decrease in distance caused by compression, results in an increase in capacitance C. The capacitance C can be measured here by the pressure signal described above. The pressure signal may be, for example, an electrical signal, such as a current or voltage. By evaluating the pressure signal in a suitable manner, the capacitance or the change in capacitance of the pressure sensor and thus the expansion state or the expansion behavior of the battery cells can then be inferred, whereby the pressure situation in the cell stack or the battery gap is inferred overall. This evaluation will be referred to in more detail later.

As material for the film of the dielectric, i.e. the above-mentioned individual separating elements, any known, elastic or plastic material can be used, which is also suitable for the dielectric. For dielectrics, it is particularly suitable to use weakly conductive or non-conductive materials, i.e. materials with a high electrical resistance, so that little or a negligibly low current flows in the material. Preferably, the conductivity of such materials is less than 20 μ S/cm. Examples of materials for the respective cell separation elements are also non-woven fabrics, silicone (Silikon), flexible foam materials or foams. Typical layer thicknesses may be, for example, 0.5mm to 1.5 mm. Depending on the desired pressure in the housing, it is of course also possible to select other layer thicknesses for the individual separating elements, for example less than 0.5mm (in the micrometer range) or more than 1.5 mm.

Furthermore, the design of the pressure sensor as a membrane also has the advantage that it can be produced particularly advantageously. In general, the layers of the pressure-sensitive film, for example the capacitor plates, can be applied by known printing methods or sputtering methods or evaporation methods or rolling methods. The layer thickness of the capacitor plates is usually only a few micrometers here. As a result, particularly space-saving and therefore advantageous storage is also possible. Therefore, such pressure-sensitive films generally have a thickness of only a few millimeters, preferably a few micrometers (at most a few centimeters), and are soft or unstable in shape. Thus, the film can simply be rolled or rolled up for storage.

Similarly, the above-described and the following embodiments can of course also be realized with more than one cell stack, i.e. with at least two cell stacks, which are again arranged in a stacked manner in the module housing in order to form the battery module. In this case, the pressure sensors can be arranged, for example, between two cell groups and/or between the respective cell group and the module housing. In this case, the cell group itself can therefore be regarded as the above-described battery cell.

The invention also includes embodiments that yield additional advantages. The design possibilities for a battery module of this type are disclosed in particular in the following embodiments. Of course, these modifications of the battery module according to the invention can also be applied or adapted to the method according to the invention and to the modifications of the motor vehicle according to the invention.

The first embodiment relates to the design of the capacitor plate described above. For this purpose, the respective capacitor plates or electrodes of the pressure sensor are formed in two opposite, electrically conductive, further layers of the pressure-sensitive membrane. The capacitor plates in the film are also referred to as electrode layers hereinafter. The membrane is thus constructed in a sandwich structure with a dielectric as core and an electrode as cover layer. Thus, the film comprises at least three layers.

Preferably, the electrodes are embodied or embodied in the membrane in a planar or planar manner. That is, the film layers constituting the capacitor plates preferably extend over the entire film surface. Thus, instead of measuring the cell pressure in a point-like manner, a surface-like measurement can be realized. By enlarging the measurement area of the pressure sensor, the advantage arises that irregularities in the expansion behavior of the battery cell can also be determined. Thus, the monitoring is comprehensive/integrated.

In order to provide electrical conductivity, the electrode layer is preferably composed of a metallized material or a metallic material. The electrode layers can be applied, i.e. evaporated or printed, for example by known sputtering or printing methods, onto the opposite sides of the cell separation element. The individual separating elements can therefore also serve as a carrier material or carrier for the capacitor plates. Alternatively, the electrode layer can also be formed or applied on a carrier material separate from the individual separating elements. At the same time, the carrier material also makes it possible to electrically insulate the pressure sensor from the battery cells.

To this end, in a further embodiment of the invention, it is provided that the battery module comprises at least one insulating element, which is in particular deformable, for electrically insulating the pressure-sensitive membrane from the respective battery cell and/or from the module housing. In this case, the insulating elements are each arranged between the membrane and the adjacent or adjacent battery cell. If a pressure-sensitive film is arranged in the gap between two monomers, two such insulating elements can therefore preferably be provided. Thus, a sandwich structure is again formed, i.e. the respective insulating element as a cover layer and the pressure-sensitive film as a core.

Preferably, each insulating element constitutes a further layer of the pressure sensitive film, and is therefore referred to as an insulating layer. Here, the insulating layer may serve as the above-mentioned carrier for the electrode. Thus, each respective insulating element provides, as it were, a printed circuit board for the pressure sensor. In this case, plastics, such as, for example, the plastics known for the production of flexible printed circuit boards, are particularly suitable as the material. Additionally or alternatively, the respective insulating element can be designed as a coating/encapsulation layer for the respective battery cell. The respective battery cell can therefore be completely surrounded or encapsulated (preferably in addition to the cell connection terminal) by the insulating layer. For example, the insulating element can be an integral component of the monolithic housing, in particular the outer layer of the monolithic housing.

The following embodiments relate in particular to the possibility of geometric construction and/or arrangement of the pressure-sensitive film in the monomer package.

In terms of the geometry of the film, in one embodiment of the invention, it is provided that the pressure-sensitive film completely covers at least one side of the respective battery cell at least over the first width. Therefore, the pressure-sensitive film is preferably configured as a film tape. The length of the film strips corresponds here to the dimension of the side faces of the battery cells in the first width or first width direction. And the height or width of the film strip is less than the dimension of the corresponding side in the second width or second width direction. Preferably, the film strips lie centrally on the respective battery cell with reference to the second width of the side faces.

In a further embodiment of the invention, provision is made in terms of the geometry of the film for the pressure-sensitive film to completely cover at least one side of the respective battery cell. This means that the pressure-sensitive film preferably extends over the entire area over the first width and the second width of the respective side. Preferably, the membrane is flush with each respective side of the battery cell.

Different possibilities are conceivable here for the geometric arrangement of the membranes, i.e. the membrane strips or the flat membranes, in the monomer groups. For example, a pressure sensor in the form of a membrane can be associated with each gap between two adjacent battery cells in the cell stack. Therefore, a plurality of pressure sensors are provided according to the number of battery cells in the cell group. In this case, the pressure-sensitive membranes can be integrated in the individual groups as further stack elements. The pressure sensor is therefore arranged as a mat or a gasket in the cell gap and/or in the module housing gap, as described above for the cell separation element. This has the advantage that a separate pressure monitoring can be carried out for each cell.

In addition or alternatively, however, it is also possible to provide the entire individual block assembly with a pressure sensor. Accordingly, the pressure-sensitive film may be arranged, for example, on one of the top and/or bottom and/or side faces of the cell stack. The terms top, bottom and side relate here in particular to the above-mentioned installation position of the battery module for the intended use, for example as a power cell. This results in the advantage that, in particular, an overall pressure monitoring of the battery module is possible.

But particularly preferred are combinations of the above geometric arrangement possibilities. For this purpose, in a further embodiment of the invention, it is provided that the pressure-sensitive membrane is arranged between the respective battery cells in a meandering manner, i.e. in a serpentine manner, extending in the stacking direction of the cell stack. Thus, the individual battery cells of the battery module are preferably surrounded or surrounded from multiple sides or sides by a meandering membrane. Here, the meandering shape of the membrane, as seen from the cell stack top view, is obtained in particular by the membrane meandering or being led between the battery cells in the stacking direction, i.e. in the stacking direction. It can thus be said that a "continuous pressure sensor" is realized. Preferably, the serpentine shape matches the geometry of the battery cell or cell housing. In particular, so-called soft-pack (or "Beutel" english) cells or prismatic or round cells or battery cells having any other predetermined geometry can therefore be monitored in their entirety by means of the pressure sensor. In the case of round cells, an S-shape, for example, can be produced by the meandering of the membrane along the cell.

This has the advantage that, in particular, a comprehensive pressure monitoring of the monomer set can be achieved. Thus, it is possible to detect the total pressure change of the cell group as well as the local pressure change of the individual battery cells with equal reliability.

Preferably, the measuring membrane comprises only one pressure sensor, which, as described above, is formed in the membrane in a planar manner. This means that the sum of the expansion states of the battery cells can be measured. Therefore, the number of blind spots or blank spots, that is, unmonitored parts in the battery module can be reduced.

By evaluating the generated pressure signal, the state of the respective monomer and thus the aging state of the monomer can thus be inferred qualitatively. As a result, deformations of the battery cells which could lead to damage or malfunction of the respective cell can also be detected as early as possible. This also makes it possible to replace the individual in a preventive or timely manner before a failure occurs.

Instead of the above-described meandering shape, other geometries of the measuring membrane for forming a continuous pressure sensor can of course also be considered. For example, comb-like or grid-like configurations of the measuring membrane are also possible. By "comb-shaped" is meant that the measuring membrane has, for example, in top view, a connecting portion or a shank against which the battery cells respectively rest with the same side in the stacking direction. For the measurement in the cell gap, arms, for example tines of a comb, are also mounted which project perpendicularly with respect to the connecting webs, said arms being arranged in the gap between two adjacent battery cells in each case. Thus, each cell is surrounded on at least three sides or at least three sides by the measuring film. In a grid-like configuration, the second connecting portion can be mounted parallel to the first connecting portion on a vertically projecting arm, in contrast to a comb-like configuration. The respective battery cell is therefore surrounded on four sides, i.e. in particular completely, by the measuring membrane.

In the continuous pressure sensor, the individual separating elements may be realized as continuous individual separating elements, for example. In other words, the individual separating elements can extend over the entire surface of the film and in particular of the capacitor layer. Thus, only exactly one cell separation element is provided for the entire battery module. Alternatively, a plurality of individual separating elements can also be integrated into the membrane as the aforementioned mats or pads. The respective position or location of the respective cell separation element can be selected, for example, as a function of the arrangement of the membranes in the cell group relative to the respective cell gap or the respective module housing gap. In order to electrically insulate the capacitor plates or capacitor layers from one another, in this configuration of the individual separating elements, for example, a further insulating element can be integrated into the film as a further layer or as a further intermediate layer.

Next, the next step involves the above-described evaluation of the pressure signal detected with the pressure sensor. To this end, in a further embodiment of the invention, the monitoring device further comprises a control circuit for operating or controlling the pressure sensor and evaluating the pressure signal detected by the pressure sensor in accordance with a predetermined evaluation criterion for determining the respective expansion state or expansion behavior of the individual battery cells.

The control circuit is preferably electrically connected to the electrodes of the measuring membrane or to the capacitor plates. For the control, the monitoring device can have, for example, a signal generator for applying a measuring signal, for example a sinusoidal or rectangular alternating voltage or a direct voltage (sinusoidal half waves), to the electrodes. For the evaluation, the control circuit furthermore has evaluation logic or an evaluation module. In order to carry out a pressure measurement for monitoring the battery module by means of the monitoring device, known capacitive measurement methods can be used. For example, the time duration from switching on the measurement signal until the saturation of the plate capacitor is reached can be determined in a time measurement, for example by measuring the current intensity by means of a current sensor. Additionally or alternatively to this, an impedance measurement for determining the impedance of the capacitor membrane can also be carried out. Finally, the pressure determination can also be carried out in a resonant frequency measurement. For this purpose, the evaluation electronics can comprise, for example, an inductance which forms a resonant circuit with the capacitor membrane.

In order to evaluate the pressure signal determined during the pressure measurement, the evaluation logic can check, for example, whether the currently determined pressure signal matches a predetermined comparison signal within a predetermined tolerance range, based on the aforementioned evaluation criterion. The comparison signal describes the non-critical or normal state of expansion of the respective cell within the above-mentioned tolerance range. Conversely, outside the tolerance range, a critical expansion state can be determined. Here, "critical" means in particular that the battery module is damaged in terms of service life and may therefore be exposed to malfunctions or damage of the battery module or of the battery cells. Therefore, the critical expansion state is a state that is important for the functionality of the battery cell or the battery module. In contrast, a non-critical or normal expansion state is a state that is not functionally relevant. The comparison signal can be determined, for example, by measurement in a test series or in a laboratory test and is therefore predefined.

In addition or alternatively, the pressure signal can also be evaluated as a function of an evaluation criterion, by first calculating the capacitance or capacitance value of the capacitor membrane from the pressure signal by means of an evaluation logic, as described at the outset. For each capacitance value or predetermined capacitance value range a state value or state information describing the respective expansion state described above may be assigned. The state values may be stored, for example, in a look-up table in a data memory of the control circuit. Preferably, the state values are binary. That is to say, the state values describe either critical expansion piles or non-critical expansion states. Thus, using the calculated capacitance value, a state value, and thus an expansion state, may be determined.

According to a further embodiment of the invention, the aforementioned control circuit is also designed to provide control signals for actuating an information system and/or a driver assistance system assigned to the battery module as a function of the determined or detected state of expansion. Preferably, the control signal is only provided when the expansion state is critical and thus is relevant for the operation of the battery module as described before.

The information system may be, for example, an output or display system in a motor vehicle. For example, the information system may be constructed as a multimedia interface. The information system can thus be actuated by means of the control signal to output and/or display a warning message or warning signal, for example, to the driver of the vehicle. The driver assistance system may be, for example, a brake system and/or a steering system of a motor vehicle. In particular, the autonomous driving function can also be implemented with a driver assistance system. Thus, by controlling with the control signal in the critical inflated state, an automatic emergency stop or emergency parking or guidance or driving of the motor vehicle to a desired destination, for example a garage or a nearby parking space, can also be performed. In addition or alternatively, a battery management system associated with the battery module can also be controlled in order to disconnect or decouple the relevant battery module or the relevant battery cell from the cell assembly or the power battery, for example.

The invention also comprises a combination of features of the described embodiments.

Drawings

Embodiments of the present invention are described below. For this purpose, it is shown that:

fig. 1 is a schematic diagram of a battery module having two battery cells with a pressure sensor in the cell gap for monitoring the expansion state of the battery cells;

fig. 2 shows a schematic view of a battery module according to fig. 1, in which the battery cells are transformed from a normal state into an expanded state;

fig. 3 shows a schematic illustration of an advantageous geometric arrangement of pressure sensors in a battery module, in which more than two battery cells are arranged in a cell stack;

fig. 4 shows a schematic representation of an advantageous geometric design possibility for a pressure sensor in a top view; and

fig. 5 shows a schematic method flow diagram of a method for producing a battery module with pressure monitoring.

The examples set forth below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments are in each case individual features of the invention which can be considered independently of one another and which in each case also improve the invention independently of one another. Thus, the disclosure is intended to include combinations of features of the embodiments other than those shown. Furthermore, the embodiments can also be supplemented by further features of the invention already described.

In the drawings, like reference numbers indicate functionally similar elements, respectively.

Detailed Description

Fig. 1 schematically shows an exploded view of a battery module 10 comprising a plurality of battery cells 20 in a side view. The battery cell 20 is designed here as a galvanic cell or electrochemical cell with a substantially rectangular battery housing 21. In addition, the respective electrodes of the battery cells 20 are led out of the respective cell housings 21 as cell terminals 22. Through these cell terminals, a dc voltage can be provided by means of the individual battery cells 20. In addition, the battery cells 20 can be suitably electrically connected to each other through the connection terminals 22 to form the battery module 10. To form the battery module 10, the battery cells 20 are furthermore arranged as a cell stack 11 in a common module housing, which is not shown in fig. 1. For a better overview, the cell stack 11 in fig. 1 comprises only two battery cells 20. However, as shown in fig. 3, it is of course possible to form the cell group 11 from more than two battery cells 20 (for example, twelve battery cells). The stacking direction R of the battery cells 20 in the cell stack extends here in particular horizontally in relation to the installation position of the battery module 10 in order to operate in accordance with regulations. Thus, the battery cells 20 are arranged or stacked adjacent to each other, rather than being stacked on top of each other.

In order to monitor the battery cells 20, in particular in the cell stack 11, with regard to the respective expansion behavior of the battery cells 20, a monitoring device 40 is integrated in the module housing. The swelling behavior describes the characteristic of each battery cell 20 increasing, i.e. bulging, over time, i.e. during the service life, due to the electrochemical properties of each cell. Furthermore, during the charging and discharging process, respiration of the cell additionally takes place, which is additionally superimposed on the continuous increase of the cell. For this purpose, fig. 2 shows the battery module 10 according to fig. 1, wherein the battery cells 20 are in a swollen state. As can be seen from fig. 2, the increase here generally occurs in an increasing direction W extending parallel to the stacking direction R. As a result of this bulging, a pressure increase or force increase occurs in the module housing of the battery module 10. If the pressure in the module housing reaches a critical limit, damage or failure generally occurs, i.e. the individual battery cells 20 collapse and thus the battery module 10 collapses.

In order to be able to monitor the respective expansion state of the respective battery cell 20 and thus to early warn of imminent malfunction, the monitoring device 40 has a pressure sensor 30 and a control circuit 34, according to fig. 1. In the exemplary embodiment of fig. 1, such a pressure sensor 30 is arranged in each cell gap between two adjacent battery cells 20 in the cell stack 11. In this case, the pressure sensor 30 is always mounted between two adjacent battery cells 20 and extends over the entire side 23 of the respective battery cell 20 facing the gap.

As can be seen from fig. 1 and 2, the pressure sensor 30 is constructed as a multilayer pressure-sensitive film according to the principle of a plate capacitor. As is usual for flat capacitors, the pressure-sensitive film here comprises two electrodes 32, which are oriented parallel to one another and are coupled to one another by an electrically insulating dielectric, as capacitor plates. The dielectric is realized here by a so-called monolithic separation element 31. Such cell separation elements are known as spacers and are used for pressure compensation of the battery cells 20 in order to compensate for deformations caused by expansion of the battery cells 20, thereby achieving pressure or force compensation in the module housing. The individual separating elements 31 are therefore an integral component of the pressure sensor 30. As a result, pressure monitoring and simultaneous pressure compensation can now be carried out by means of the pressure sensor 30.

In order to electrically shield or insulate the electrodes 32 from the respective battery cells, the membrane additionally comprises respective insulating elements 33 in the respective further layers. For this purpose, the material is particularly suitable for use with plastics, for example for flexible circuit boards. Thus, in addition to the insulating function, each respective insulating element 33 may also serve as a carrier element for the respective electrode 32. That is, each respective electrode 32 is machined into the corresponding insulating element 33, or the insulating element 33 is equipped with an electrode 32. For this purpose, known printing methods for printing electronic components (printed electronics), such as the so-called flexographic printing method or the multilayer flexographic printing method, are particularly suitable. It is also contemplated herein to use a sputtered or evaporated electrode 32. Instead of the respective insulating element 33, the aforementioned dielectric 31 can alternatively be used as a carrier element or as a printed circuit board for the electrodes 32.

As can be seen from fig. 1 and 2, the electrodes 32 are preferably embodied in a planar/flat manner in the capacitor film, so that the monitoring device 40 in each cell gap has only one pressure sensor, which can monitor the respective side 23 of two adjacent battery cells 20 completely. Therefore, surface monitoring of the battery cells 20 is performed, not point monitoring. Alternatively, a plurality of electrode pairs 32 may be provided in the gap, so that the monitoring device 40 includes a plurality of pressure sensors for individual monitoring.

By designing the pressure sensor 30 according to the principle of a plate capacitor, the expansion behavior of the battery cell 20 is currently determined, in particular by capacitive measurement methods. The pressure sensor 30 is therefore configured as a capacitive pressure sensor. This capacitive measuring method is based on: the capacitance of a plate capacitor varies indirectly in proportion to the respective distance d of the capacitor plates. Here, a decrease in the distance d of the electrode 32 results in an increase in the capacitance of the pressure sensor 30. As can be seen from fig. 2, this change in the distance d is caused by an expansion, i.e. deformation, of the battery cell 20 in the respective direction of increase W. That is, due to the expansion or swelling of the battery cell 20, the capacitor film is compressed, so that the distance d between the electrodes 32 (as shown in fig. 2) is reduced as compared to the normal state or the non-swelled state (see fig. 1).

In order to be able to determine the change in distance d when the battery cell 20 expands, and thus the resulting change in capacitance of the pressure sensor 30, the pressure sensor 30 additionally has a control circuit 34. The respective pressure signal of the capacitor membrane is detected and evaluated by means of the control circuit 34 to determine the capacitance due to the distance change and thus to the expansion behavior of the respective cell. For this purpose, a measurement signal is first applied to the electrodes 32 of the pressure sensor 30 by means of a signal generator 36 of the control circuit 34. The signal generator 36 is designed here as a voltage source for the pressure sensor 30. Thus, a voltage is provided as the measurement signal. The voltage now has a curved shape or course which simulates a half-sine wave.

By applying a measuring signal to the pressure sensor 30, a current flows between the electrodes 32, the course of which current is related in a known manner to the capacitance of the capacitor membrane. This current curve, i.e. the obtained current signal, can be measured, for example, as the aforementioned pressure signal.

To receive or detect the pressure signal and subsequently evaluate the pressure signal, the control circuit 34 includes evaluation logic 36. The evaluation logic 36 checks here: whether the pressure signal corresponds to a critical expansion state of the respective battery cell 20, according to predetermined evaluation criteria. For this purpose, for example, the pressure signal can be compared with a comparison signal and the evaluation logic 36 can check that: whether the pressure signal matches the comparison signal within a predetermined tolerance. The comparison signal describes the noncritical expansion or normal state of the respective battery cell 20, as it is shown, for example, in fig. 1. In the present example, the comparison signal can thus be, for example, a current signal, the course of which reflects the normal state of the battery cell 20. Conversely, if the pressure signal lies outside a predetermined tolerance range, a critical expansion state, i.e., a bulging state of the battery cell 20, can be assumed, as is shown by way of example in fig. 2.

In order to be able to process this critical expansion state early when it is determined, a control signal is generated by means of the control circuit 34, for example, which controls an information system associated with the battery module 10 to output a warning message. If the battery module 10 is designed, for example, as a component of a power battery for a motor vehicle, the multimedia interface of the motor vehicle can thus, for example, issue a warning message to the driver or passenger of the motor vehicle.

Fig. 3 shows a side perspective view of the battery module 10 according to fig. 1 with a pressure sensor 30. However, in contrast to fig. 1, more than just two battery cells 20 are shown here, and twelve such battery cells 20 are shown here in particular. Fig. 3 is intended to illustrate, in particular, an advantageous geometric design of a pressure sensor 30 designed as a capacitor diaphragm. In contrast to fig. 1 and 2, the capacitor film according to fig. 3 does not completely cover the entire side 23 of the respective battery cell 20. Instead, the capacitor film is constructed as a film tape. Thus, the capacitor film completely covers the respective side 23 of the battery cell 20, against which the film abuts, in the first width B1 or first width direction. While the height of the film strip is much smaller than the dimension of the corresponding side 23 over the second width B2. In the present case, the film strip also rests centrally on the respective battery cell 20 with respect to the second width B2 of the respective side 23.

In addition to the described geometrical dimensions of the capacitor film, the capacitor film is also arranged in a particular geometrical shape inside the cell stack 11. This geometry can be seen with particular reference to fig. 4. Fig. 4 shows a battery module 10 with battery cells 20 arranged as a battery cell stack 11 according to fig. 3 in a top view or a bird's eye view. In the stacking direction L of the cell stack 11, the capacitor membranes run here meandering between the respective battery cells 20. Here, the meandering shape M is achieved in particular by the meandering or running of the membrane between the battery cell 20 and the cell stack 11.

In this case, the pressure sensor 30 is preferably, as described above, realized as a single sensor, which is surface-mounted in the membrane strip. That is, the serpentine capacitor film forms a continuous pressure sensor. The advantage thereby obtained is that the pressure sensor 30 is designed as a single component. Therefore, it is not necessary to install a separate pressure sensor 20 in each intermediate layer or each gap between two adjacent battery cells 20. Thus, pressure measurements may be performed with only one single sensor across the entire battery cell module. This can simplify the processing of the pressure signal. In addition, surface measurement of the pressure is also possible in this way. It is assumed here that a change in size, i.e. a greater geometry of one of the battery cells 20, generally leads to a pressure increase in the entire cell module or battery module 10. Thus, both total pressure changes and local pressure changes can likewise be reliably detected with only one pressure sensor 30.

Finally, fig. 5 also shows a schematic method flow diagram of a method for producing a battery module 10 as described above. For this purpose, in step S1, a module housing is first provided for the common arrangement of two or more battery cells 20 of the battery module, which form a cell stack 11. Furthermore, the previously described battery cells 20 for arrangement in the battery housing as a cell stack 11 are provided in step S2. Finally, the aforementioned pressure sensor 30 is also provided in step S3. The pressure sensor 30 can be provided, for example, as a membrane strip as shown in fig. 3 or 4 or, for example, also as a single membrane element, which can be installed separately in the cell gap and can be controlled by the control circuit. By providing the dielectric 31 of the pressure sensor 30 as a cell separation element as one of the individual layers of the film, thus forming an integral component of the capacitor film, i.e. the pressure sensor 30, it is therefore possible in a common arrangement process or arrangement step, currently in step S4, to arrange the cell separation element and the pressure sensor 30 in each case between every two adjacent battery cells 20 in the cell stack 11, and preferably also between the respective battery cell 20 and the module housing.

Overall, a battery module 10 or cell module with innovative pressure monitoring is thus achieved. The pressure sensor 30, which is designed as a capacitor membrane, offers the possibility of detecting the reaction in the battery module 10 in advance, i.e., preferably before the initial phase, because the pressure monitoring takes place in the cell gap without waiting for a subsequent electrical or thermal parameter to be generated as a result of a pressure increase in the cell module. The interior of the respective cell can thus be observed by means of the pressure sensor 30. Evaluation of the pressure signal yields important information about the increasing behavior and the regular behavior of the respective monomer, which information can indicate a deviation of the monomer (Abdrift) or an early failure. Thus, for example, unplanned shop repairs and anchoring situations can be avoided or reduced. Furthermore, since the measuring film, i.e. the capacitor film, extends over the entire length of the battery module 10 with the above-mentioned meandering shape M and measures the pressure change between two adjacent cell pairs, respectively, irregularities in one or more battery cells 20 of the battery module 10 can be identified, which irregularities lead to pressure changes due to bulging, i.e. the above-mentioned swelling. Thereby only evaluating the sum of the pressure changes of the battery cells. However, this has the advantage that no unmonitored or blind or blank spots are present in the cell module and that, unlike in the case of point sensors or single sensors for point measurement, pressure changes can be detected for all cells. Thus, a qualitative assessment of the state of ageing, i.e. the monomer swelling, can be made particularly simply. Preventive replacement can be achieved in the event of aging which occurs too severely or prematurely.

Here, when the capacitor film is so-called "rolled (der roller kommt)", the capacitor film can be applied particularly thin, for example, with a thickness of a few millimeters and advantageously. In this case, electronic components, for example electrodes or dielectrics, can be applied to the insulating element, for example by printing.

Thus, in general, a pressure sensor or pressure monitoring for the battery module 10 is realized by the present invention.

Claims

1. A battery module (10) having at least two battery cells (20) which are arranged as a cell stack (11) in a common module housing to form the battery module (10), wherein a cell separating element (31) is arranged in each cell stack (11) between two adjacent battery cells (20) and/or between a respective battery cell (11) and the module housing, which cell separating element is designed to be deformed in accordance with an expansion state of the battery cell (20), for monitoring the expansion state, the battery module (10) further comprising at least one monitoring device (40) having a pressure sensor (30) for detecting a pressure signal corresponding to the expansion state,

it is characterized in that the preparation method is characterized in that,

for the capacitive detection of pressure signals, the pressure sensor (30) is designed as a multilayer pressure-sensitive membrane according to the principle of a plate capacitor, the individual separating elements (31) forming a dielectric for the pressure sensor (30) as one of the layers of the membrane.

2. The battery module (10) according to claim 1, characterized in that the capacitor plates (32) of the pressure sensor (30) are designed in two further opposite, electrically conductive layers of the membrane.

3. The battery module (10) according to any one of the preceding claims, characterized in that the battery module (10) comprises at least one insulating element (33) for electrically insulating the pressure-sensitive membrane from the respective battery cell (20).

4. The battery module (10) according to any of the preceding claims, wherein the pressure-sensitive film completely covers at least one side (23) of the respective battery cell (20) at least over the first width (B1).

5. The battery module (10) according to any one of the preceding claims, wherein the pressure-sensitive film completely covers at least one side (23) of the respective battery cell (20).

6. The battery module (10) according to any one of the preceding claims, wherein the pressure-sensitive membrane is arranged between the battery cells (20) extending meandering along the stacking direction (R) of the cell group (11).

7. The battery module (10) according to any one of the preceding claims, wherein the monitoring device (40) further comprises a control circuit (34) for operating the pressure sensor (30) and evaluating the pressure signal detected by the pressure sensor (30) according to a predetermined evaluation criterion in order to determine the expansion state of the respective battery cell (20).

8. The battery module (20) according to claim 7, characterized in that the control circuit (34) is further designed to provide a control signal for driving an information system and/or a driver assistance system assigned to the battery module (20) depending on the determined expansion state.

9. Motor vehicle having a power battery comprising at least one battery module (10) according to any one of the preceding claims.

10. A method for producing a battery module (10) having at least two battery cells (20), wherein the at least two battery cells (20) are arranged as a cell stack (11) in a common module housing for forming the battery module (10), wherein a cell separating element (31) which can be deformed in accordance with the expansion state of the battery cells (20) is provided between two adjacent battery cells (20) and/or between a respective battery cell (20) and the module housing when arranged in the cell stack (11), and wherein at least one monitoring device (40) is provided for monitoring the expansion state of the battery module (10) when arranged in the module housing, said monitoring device having a pressure sensor (30) for detecting a pressure signal corresponding to the expansion state,

it is characterized in that the preparation method is characterized in that,

in order to detect pressure signals capacitively, the pressure sensor (30) is provided as a multilayer pressure-sensitive membrane according to the principle of a plate capacitor, and the cell separation element (31) is provided as a dielectric for the pressure sensor (30) as one of the layers of the membrane, so that the cell separation element (31) and the pressure sensor (30) are each arranged between two adjacent battery cells (20) and/or between the respective battery cell (20) and the module housing in a common arrangement process in a cell stack (11).