DE102021205748A1 - Battery system and motor vehicle - Google Patents

Abstract

A battery system (1) according to the invention, in particular for a motor vehicle (100), has: a battery module (10), which in turn comprises a number of battery cells (12) and a module housing (16) enclosing them in a box-like manner, a system housing (2), which surrounds the battery module (10), in particular for mechanical protection, a cooling plate (30) which is arranged on the underside of the battery module (10) and is used to dissipate heat from the battery cells (12), and a latent heat storage device (40). This is set up to absorb heat from the battery cells (12) and to temporarily store it, and is arranged on side surfaces running between the bottom and the top of the battery module (10). In addition, the latent heat accumulator (40) has a phase change material (46) which is provided with a filling material (48, 68) with increased thermal conductivity compared to the phase change material (46).

Description

The invention relates to a battery system which is intended in particular for a motor vehicle. The invention also relates to a motor vehicle with such a battery system.

In the course of the progressive electrification of motor vehicles, but also of buildings and the like, energy stores are increasingly being used specifically in the form of rechargeable batteries. In the case of (land-based) motor vehicles in particular, these are used to provide energy for electric motor drives, for example traction motors. When these batteries are in operation, the (secondary) cells usually used in these batteries heat up, in particular due to electrical power loss. On the one hand, although it is advantageous for the cells to be tempered to a specific operating temperature value, the cells must not become too warm, since this can significantly reduce their service life or even destroy them. In addition, if a battery with a large number of cells overheats, so-called "thermal runaway" can occur if one cell overheats severely and transfers the heat to an adjacent one, which then also overheats.

In order to control the energy output, among other things as a function of the temperature inside the battery, such batteries often also have what is known as a battery management system, which includes a controller in which this control and monitoring function is implemented. In particular for use in motor vehicles, such batteries also have cooling systems in order to keep the cells within a predetermined range of their operating temperature value.

In principle, so-called prismatic (i.e. box-like) cells, cylindrical cells (usually in the form of a circular-cylindrical rod) or so-called pouch cells are used as cells. In the case of the latter, the electrodes and electrolytes are stacked flat and in layers one on top of the other and sealed in a fluid-tight manner in a pocket (the so-called “pouch”) that is flexible within certain limits and is usually approximately rectangular. Due to the flat, d. H. particularly the relatively thin design of these pouch cells, they have good surface-to-volume ratios for cooling. However, due to their structure, these pouch cells can also be stacked particularly well, so that heat dissipation from each individual cell in the direction normal to their areal extension is in turn prevented or at least reduced.

Batteries (especially in the field of automotive technology also referred to as traction batteries), in which pouch cells are used, usually have an (“inner”) battery module, within which one or more stacks of pouch cells are arranged, contacted and sealed in a fluid-tight manner . This battery module is usually coupled to a cooling plate, which is arranged to run parallel to the stacking direction of the pouch cells and thus along a narrow side of each pouch cell. This cooling plate is usually arranged on the underside of the battery module and on the opposite upper side the battery management systems and contact points for galvanic contacting of the battery module with an on-board network of the motor vehicle. These contact points are usually designed as so-called busbars (also: "busbars" or "busbars").

A disadvantage of such a cooling plate is that, on the one hand, heat is dissipated only to the underside of the battery module and only a limited amount of heat can be dissipated. Out of WO 2020/044001 A is known, for example, to use a so-called phase change material for cooling a battery. Phase change material is used in so-called latent heat storage systems. These have the advantage that they can absorb (or give off) thermal energy in the (temperature) range of the phase transition without changing their temperature. This is due to the energy required for the phase transition, e.g. the melting of crystals. This "temperature plateau" can be advantageous in the event of comparatively rapid temperature changes within the battery, e.g. to brake or "catch" it.

The object of the invention is to further improve the cooling of a battery.

This object is achieved according to the invention by a battery system having the features of claim 1. This object is also achieved according to the invention by a motor vehicle having the features of claim 12. Further advantageous and partly inventive embodiments and developments of the invention are in the dependent claims and the following Description set forth.

The battery system according to the invention is preferably set up and provided for use in a motor vehicle, in particular a land-based motor vehicle. Alternatively, the battery system can also be set up and provided for use in a building.

The battery system according to the invention has a battery module, which in turn comprises a number of battery cells and a module housing enclosing them in a box-like manner. Furthermore, the battery system has a system housing which surrounds the battery module, in particular for its mechanical protection. In addition, the battery system has a cooling plate, which is arranged on the underside of the battery module and is used to dissipate heat from the battery cells. Furthermore, the battery system has a latent heat accumulator, which is set up to absorb heat from the battery cells and store it temporarily, and which is arranged on side surfaces running between the bottom and the top of the battery module. This latent heat storage device has a phase change material that is provided with a filling material. This filling material has an increased thermal conductivity compared to the phase change material.

"Filling material" is understood here and in the following in particular in the plastics technology sense, in particular to the effect that this filling material is distributed in a base material - here the phase change material - and thus at least partially fills the volume provided for the component formed by the base material.

Due to the (increased) thermally conductive filling material, the heat acting in the latent heat store can advantageously be better introduced into the phase change material. In particular, this heat can be distributed over the volume occupied by the phase change material and thus absorbed by the latter. This is particularly advantageous in that phase change material regularly has a comparatively low thermal conductivity and thus even has a heat-insulating effect, at least within certain limits. In addition, by using the filling material, heat can also be dissipated through the phase change material.

So-called pouch cells are preferably used as battery cells. In particular, these are aligned with their surface extension parallel to the side walls, preferably stacked between two opposite side surfaces. As a result, the latent heat storage device is located at a thermally favorable location in order to be able to dissipate heat from the battery cells.

The system housing is preferably formed from extruded profiles or plates, in particular from aluminum, and has a wall thickness of approximately 0.5 to 20 millimeters, but preferably in the range from 1 to 6, preferably from 2 to 4 millimeters. Alternatively, the system housing is deep-drawn from high-strength sheet steel with a wall thickness of 0.4 to 1.5, preferably 0.6 to 1 millimeter.

In an expedient embodiment, a particulate material, for example a granulate or a powder, and/or a fibrous material is used as the filling material.

In the case of the particulate filling material, for example, grain-like, “flake”-like, needle-like or similar particles are used. In this case, the thermal conductivity is formed by the formation of “conduction paths” between the individual particles, for example between particles in contact.

The degree of filling of the phase change material with the filling material is preferably chosen to be so high that a significant change in the thermal conductivity for the latent heat storage device can be detected.

In an expedient embodiment, a (in particular comparatively flexible) textile or a comparatively rigid lattice structure is used as the fibrous material. For example, woven fabrics, scrims (“wovens” or “nonwovens”) or even a knitted fabric are used as textiles. The fibrous material has the advantage that heat conduction paths are already present due to the structure and that the filling material can be arranged within the latent heat storage device relatively independently of the consistency of the phase change material.

In a further expedient embodiment, a metal, preferably one with high thermal conductivity such as copper and/or aluminum, is used as the filling material.

In a preferred embodiment, the phase change material is such that it uses (or has) a phase transition from solid (in particular from crystalline or at least partially crystalline) to liquid when used as intended (in particular for cooling the battery cells). In other words, the phase change material is in the solid state during operation of the battery cells below a "cooling start value" (i.e. while the latent heat storage device is not yet being used for cooling).

In an alternative embodiment, the phase change material can also use the phase transition from liquid to gaseous. This has the advantage that, in some cases, significantly more thermal energy can be absorbed during evaporation than during melting.

In a further expedient embodiment, the phase change material is present in granular form at least in the initial state—ie before the first melting. For example, the phase change material is in powder form when delivered or installed. This has the advantage that the surface area of the phase change material is enlarged overall and the heat input can thus be improved. It is optionally conceivable within the scope of the invention for the phase change material to be incorporated into granules or microcapsules, which prevents molten material from escaping and thus enables the granulate shape to be retained even after repeated melting. The use (i.e. use in a battery system as part of a latent heat storage device) of a granular phase change material also represents an independent invention, in particular independent of the use of the thermally conductive filling material.

In a preferred embodiment, the phase change material has a phase transition temperature value, in particular a melting point, of approximately 56 degrees Celsius. In this context, "approximately" is understood in particular as a tolerance of plus/minus 5 degrees Celsius. This phase transition temperature value has the advantage that the battery life can be halved every time 60 degrees Celsius is exceeded by 10 degrees Celsius.

In a particularly preferred embodiment, the phase change material is formed by a mixture of individual (phase change) materials with different melting points (i.e. in particular different phase transition temperatures). As a result, the cooling effect made possible by the phase transition can be extended over a comparatively wide temperature range (preferably from around 32 to 58 degrees Celsius). In particular when using granular materials, an at least coarse-grained structure can be retained by using part of the phase change material with a comparatively high phase transition temperature value, which is not exceeded during normal battery operation and thus this material does not melt. For example, individual materials with melting points of 32, 48, 56 and 58 degrees Celsius are used. Particularly in the event that the rest of the phase change material also has a comparatively high viscosity in the molten state, it is possible in this way to prevent molten material from flowing together and thus segregating the different materials. For example, at least the material that changes phase at 58 degrees Celsius serves as a kind of "emergency cooling" to prevent "thermal runaway", but should not change its phase at all during normal operation.

Comparable adjustment of the mixture of the individual phase change materials can also prevent or reduce segregation of particulate filler, since non-melted areas of the phase change material mixture prevent or reduce sinking of the filler particles in the molten material.

In an expedient embodiment, the latent heat accumulator has sandwich-like plates which are formed from profiles connected to one another, preferably aluminum profiles. These aluminum profiles enclose an interior in which the phase change material is introduced. In particular, these aluminum profiles form rectangular plates with an L-shaped angled edge at least on one edge, preferably on two edges, so that two aluminum profiles placed opposite one another are spaced apart by this angled edge on the one hand and enclose the interior space between them on the other. The phase change material is preferably sealed in a fluid-tight manner in a foil bag, which is preferably formed from aluminum foil, and placed between the aluminum profiles. In an optional variant, the aluminum profiles are welded to one another or connected in some other way.

Preferably, the aluminum profiles also have a surface structure on both sides, for example they are corrugated. On the one hand, this increases the heat input surface and, on the other hand, it offers a volume into which the phase change material can "evade" in the event of an increase in volume, which usually occurs during the phase transition during heating (i.e. melting or evaporation).

The sandwich-like plates formed in this way are optionally fastened to the side faces of the battery module, for example screwed or bonded. In particular, these sandwich-like plates are laid flat on the side surfaces of the module housing and optionally using a thermally conductive intermediate layer, for example thermally conductive paste or the like. Alternatively, the sandwich panels themselves form the side walls of the module housing. In this case, the latent heat store is arranged on the side surfaces of the battery module and is specifically integrated into the module housing.

In an alternative variant, the latent heat store is formed in that the phase change material together with the (thermally conductive) filling material in a gap between the side surfaces of the module housing and the System housing is introduced. This intermediate space is preferably tightly sealed in such a way that contact of the phase change material (in particular its liquid phase) with galvanic contact elements—in particular the so-called busbars—of the battery module is prevented. For example, a seal is arranged in the area of the upper side of the system housing and/or the battery module, which prevents the phase change material from escaping from the intermediate space into the environment and/or into an area within the system housing in which the aforementioned galvanic contact elements are arranged. In this embodiment, the battery module is thus embedded at least with its side surfaces in the phase change material and thus in the latent heat store. This advantageously contributes to a particularly good thermal connection.

In a further alternative embodiment, the latent heat accumulator has foil pockets which are formed by a metal foil which is shaped like a pot or box, in particular deep-drawn. This metal foil is covered with a cover layer, enclosing the phase change material and the filling material, and in particular sealed in a fluid-tight manner. These film pockets are attached to the side surfaces of the battery module, specifically to the side walls of the module housing, in a manner comparable to the sandwich-like plates described above. Optionally, the film pockets are attached to a carrier plate--particularly made of aluminum--and attached to the side surfaces by means of this plate (for example screwed or welded).

In a preferred development, the metal foil of the foil pockets described above is provided with a protective layer made of a plastic and a hard material, at least on a surface facing the system housing. This protective layer serves in particular as protection against punctures, in particular both against external influences and against punctures, for example by sharp filler particles, from the inside. For example, polyurethane is used as the plastic and aluminum oxide (also referred to as “corundum”) as the hard material. The polyurethane serves in particular to reinforce the aluminum foil against mechanical impact, the aluminum oxide as protection against abrasion. For this purpose, the polyurethane is optionally applied by means of a (preferably aqueous, alternatively oil-based) solution in which the aluminum oxide is dispersed, for example in the form of particles with a diameter of preferably about 12-15 μm. This mixture is applied, for example, as a "spray coating" and then crosslinked.

The motor vehicle according to the invention, which is preferably land-based, has the battery system described above and therefore also has the same advantages.

Here and in the following, the conjunction “and/or” is to be understood in particular in such a way that the features linked by means of this conjunction can be designed both together and as alternatives to one another.

• 1 in einer schematischen Draufsicht ein Batteriesystem,
• 2 in einer schematischen Detailansicht von einer Seite das Batteriesystem,
• 3 in einer Teilschnittansicht III-III gemäß 2 das Batteriesystem,
• 4 in Ansicht gemäß 2 ein alternatives Ausführungsbeispiel des Batteriesystems,
• 5 in einer Teilschnittansicht III-III gemäß 4 das dortige Batteriesystem,
• 6 in Ansicht gemäß 1 ein weiteres Ausführungsbeispiel des Batteriesystems,
• 7 in einer schematischen Seitenansicht das Batteriesystems gemäß 6, und
• 8 in einer Seitenansicht schematisch ein Kraftfahrzeug.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show in it:

• 1 a schematic plan view of a battery system,
• 2 the battery system in a schematic detailed view from one side,
• 3 in a partial sectional view according to III-III 2 the battery system,
• 4 in view according to 2 an alternative embodiment of the battery system,
• 5 in a partial sectional view according to III-III 4 the battery system there,
• 6 in view according to 1 another embodiment of the battery system,
• 7 in a schematic side view the battery system according to FIG 6 , and
• 8th in a side view schematically a motor vehicle.

Corresponding parts are always provided with the same reference symbols in all figures.

In 1 a battery system 1 is shown schematically in a view from above. This battery system 1 includes a system housing 2 that delimits an interior space 4 . A cover of the system housing 2, by means of which the interior 4 is closed at the top, is in 1 not shown. The system housing 2 also has an intermediate wall 6 by means of which the interior space 4 is divided into two partial spaces 8 . The battery system 1 also has two battery modules 10 , one of which is arranged in one of the compartments 8 .

Each battery module 10 has a large number of battery cells, specifically secondary cells, ie rechargeable cells. These battery cells are designed as pouch cells 12 . The pouch cells 12 are stacked or arranged alternately with pressure equalization layers 14 (also: “compression pad”) in a module housing 16 . Each pouch cell 12 has a positive current collector 18 and a negative current collector 20 on the means a corresponding busbar 22 are connected to a corresponding connection 24 . Two stacks of pouch cells 12 are arranged one above the other in each battery module 10 (see Fig. 2 ).

On an upper (cover) plate 26 of the module housing 16 is a circuit, in particular a circuit board with such arranged, which forms a battery management system (abbreviated: "BMS 28"). For cooling is opposite, i. H. below the two stacks of pouch cells 12, a cooling plate 30 is arranged. Specifically, this cooling plate 30 is arranged below a base plate 32 of the module housing 16 . The battery module 10 is in turn connected to the system housing 2, in particular by inserting an intermediate layer 34 made of thermally conductive material. In particular, the latter is a thermally conductive paste.

In order to now improve the heat dissipation from the pouch cells 12 , the battery system 1 has a latent heat store 40 . This is in accordance with the embodiment 1 and 2 integrated into the side walls 42 of the module housing 16 forming side surfaces, which thus connect the base plate 32 and the plate 26 to one another. this is in 3 shown in more detail.

The latent heat accumulator 40 has a comparatively thin-walled shell—referred to here as a “bag 44”—in which a phase change material 46 is arranged. In the present exemplary embodiment, the phase change material 46 is formed by a mixture of different, wax-based materials, each of which has a different melting point (the so-called phase transition temperature). This results in a comparatively wide temperature range, here from 32 to 58 degrees Celsius, in which several phase transitions take place. A thermally conductive filling material, copper particles 48 here, is distributed in the phase change material 46 . This allows for improved heat input and heat distribution across the entire volume of phase change material 46 .

The bag 44 is between two aluminum L-profile plates - in short: "wall plates 50" - introduced, which are set opposite to each other. The two wall panels 50 have a wall thickness of, for example, 1.5 millimeters here. The wall panels 50 have a corrugated surface. This results in an enlarged heat absorption/heat emission surface. This also gives the bag 44 the opportunity to expand as the phase change material 46 melts and to "evade" into "valleys" of the respective wall panel 50 . Optionally, only elevations are formed on the outside of the wall panels 50 and only valleys are formed on the inside, ie facing the bag 44 . The wall panels 50 are also joined together by welds 52 . On the inside of the latent heat accumulator 40, this, ie specifically the inner wall panels 50, rests on the “first” pressure equalization layer 14.

The two wall panels 50 also have screw holes 54 which are used for connection to the panel 26 and the bottom panel 32 . The overall thickness of the side wall 42 formed by the latent heat store 40 is approximately 5 to 10 millimeters.

In 4 an alternative exemplary embodiment of the latent heat storage device 40 is shown. This is divided here into several “sub-storage devices” 56 . These sub-storage devices 56 are attached to the side walls 42 of the module housing 16 . Optionally, the respective side wall 42 is also designed here as a corrugated plate (cf. 3 ).

The lower reservoirs 56 have an aluminum foil 60 deep-drawn to form a pot or box 58 . This box 58 is filled with the phase change material 46 and the filling material, ie the copper particles 48 . The box 58 is then closed by means of a cover film 62, for example glued. Optionally, this bonding only serves to attach the cover film 62 for transport. An air gap 64 is left in the interior of the box 58 in order to enable a volumetric expansion of the phase change material 46 during the phase change.

The closed box 58 is then attached to the side wall 42, for example by means of welding, in particular ultrasonic welding or the like. In the case of the “only” glued cover film 62, this can also be bonded to the box 58 and the side wall during this welding step.

In order to improve the resistance of the aluminum foil 60 forming the box 58 - since this is not the case in accordance with the exemplary embodiment 1 until 3 is installed in a housing-like structure - this is coated on the outside with a protective layer 66. This is formed by an aqueous solution of a polyurethane into which aluminum oxide particles with a grain size of about 12 to 15 microns are mixed. This solution is spray coated onto the aluminum foil 60, preferably before it is reformed. This protective layer 66 protects against puncture of the aluminum foil 60 - both from the inside and from the outside - and against abrasion.

In 6 and 7 a further exemplary embodiment of the battery system 1 is again shown. The latent heat accumulator 40 does not have its own housing here. Rather, the latent heat accumulator 40 is formed directly in the two partial spaces 8 of the interior 4 . For this purpose, the phase change material 46 is filled into the interior space 4 remaining between the battery module 10 and the system housing 2 . In the present exemplary embodiment, the phase change material 46 is introduced into the intermediate space, for example in the form of granules. In contrast to the exemplary embodiments described above, a comparatively rigid copper mesh or grid 68 is used here as the thermally conductive filling material. This has the advantage that it can be introduced comparatively easily and also already has “heat conducting paths” from the battery module 10 in the direction of the system housing 2 (and also in the direction of the heat conducting plate 30).

To prevent molten phase change material 46 from escaping from the system housing 2 and also to prevent contact with current-carrying elements that are arranged on the upper side of the battery module 10, the side walls 70 of the system housing 2 are connected here to the base plate 32 of the battery module 10 by means of weld seams 72 in a media-tight manner. A seal 74 is arranged on the top, specifically a ring-shaped peripheral sealing frame, by means of which the plate 26 (in the exemplary embodiment shown, optionally also a cover of the system housing 2) is connected in a fluid-tight manner. Specifically, the plate 26 is bolted to the side walls 70 .

In 8th a motor vehicle 100, specifically a wheeled, land-based passenger vehicle, is shown. This motor vehicle 100 is designed as an electric vehicle and thus has an electric motor 102 as the traction motor. To supply energy, the motor vehicle has several of the battery systems 1 described above, which are combined to form a traction battery.

The subject matter of the invention is not limited to the exemplary embodiments described above. Rather, further embodiments of the invention can be derived by the person skilled in the art from the above description. In particular, the individual features of the invention and their design variants described with reference to the various exemplary embodiments can also be combined with one another in other ways.

Reference List

1

battery system

2

system case

4

inner space

6

partition

8th

subspace

10

battery module

12

pouch cell

14

pressure equalization situation

16

module housing

18

current collector

20

current collector

22

power rail

24

connection

26

plate

28

battery management system

30

cooling plate

32

bottom plate

34

liner

40

latent heat storage

42

Side wall

44

bag

46

phase change material

48

copper particles

50

wall plate

52

Weld

54

screw hole

56

sub storage

58

Crate

60

aluminum foil

62

cover sheet

64

air gap

66

protective layer

68

copper grid

70

Side wall

72

Weld

74

poetry

100

motor vehicle

102

electric motor

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2020/044001 A [0006]

Claims (12)

Having a battery system (1), in particular for a motor vehicle (100). - a battery module (10), which in turn comprises a number of battery cells (12) and a box-like enclosing module housing (16), - a system housing (2), which surrounds the battery module (10), in particular for mechanical protection, - a cooling plate (30) which is arranged on the underside of the battery module (10) and is used to dissipate heat from the battery cells (12), and - a latent heat store (40) which is set up to absorb heat from the battery cells (12) and to temporarily store it, and which is arranged on side surfaces running between the bottom and the top of the battery module (10), the latent heat store (40) a phase change material (46) which is provided with a filling material (48, 68) with increased thermal conductivity compared to the phase change material (46). Battery system (1) according to claim 1 , Particles (46) and/or fibrous material (68) being used as filling material. Battery system (1) according to claim 2 , wherein a textile or a lattice structure (68) is used as the fibrous material. Battery system (1) according to one of Claims 1 until 3 , A metal, in particular copper and/or aluminum, being used as the filling material (48, 68). Battery system (1) according to one of Claims 1 until 4 , wherein the phase change material (46) uses a phase transition from solid to liquid in the intended use. Battery system (1) according to one of Claims 1 until 5 , wherein the phase change material (46) is present in granular form at least in the initial state. Battery system (1) according to one of Claims 1 until 6 , wherein the phase change material (46) is formed by a mixture of individual materials with different melting points. Battery system (1) according to one of Claims 1 until 7 , wherein the latent heat accumulator (40) has sandwich-like plates which are formed from interconnected aluminum profiles (50) which enclose an interior space into which the phase change material (46), in particular in a film bag (44) sealed in a fluid-tight manner, is introduced, in particular wherein the plates (50) are attached to the side surfaces of the battery module (10). Battery system (1) according to one of Claims 1 until 7 , wherein the latent heat store (40) is formed in that the phase change material (46) together with the filling material (48, 68) is introduced into an intermediate space between the side surfaces of the module housing (16) and the system housing (2), in particular the intermediate space is sealed in such a fluid-tight manner that contact of the phase change material (46) with galvanic contact elements (24) of the battery module (10) is prevented. Battery system (1) according to one of Claims 1 until 7 , wherein the latent heat accumulator (40) has foil pockets which are formed by a metal foil (60) shaped like a pot or box, which is covered with a cover layer (62) including the phase change material (46) and the filling material (48, 68), wherein the foil pockets are attached to the side surfaces of the battery module (10). Battery system (1) according to claim 10 , wherein the metal foil (60) is provided with a protective layer (66) made of a plastic and in particular also a hard material on at least one surface facing the system housing (2). Motor vehicle (100) with a battery system (1) according to one of Claims 1 until 11 .

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