DE102023207402B4 - Battery for a motor vehicle - Google Patents

Abstract

Battery (4) for a motor vehicle (2), comprising
- a cell stack (12) with battery cells (14),
- wherein a phase-change material (22), in particular a solid material, is arranged between two adjacent battery cells (14),
characterized by
that in a base plate (26) a reservoir (28) for the phase change material (22),
when this melts, it is arranged.

Description

The invention relates to a battery for a motor vehicle, which has a cell stack with battery cells, according to the preamble of claim 1. The invention further relates to a motor vehicle with such a battery.

An electrically powered vehicle typically has a traction battery (high-voltage battery, HV battery) that supplies energy to an electric motor to propel the vehicle. The term "electrically powered vehicle" refers in particular to an electric vehicle that stores the energy required for propulsion solely in the traction battery (BEV, battery electric vehicle), an electric vehicle with a range extender (REEV, range extended electric vehicle), a hybrid vehicle (HEV, hybrid electric vehicle), a plug-in hybrid vehicle (PHEV, plug-in hybrid electric vehicle), and/or a fuel cell vehicle (FCEV, fuel cell electric vehicle), which temporarily stores the electrical energy generated by a fuel cell in the traction battery.

For example, such a traction battery comprises a cell stack with prismatic battery cells arranged side by side in a stacking direction. The battery cells are temperature-controlled by means of a cooling plate through which a cooling medium flows. For example, the cooling plate is located on the top and/or bottom of the cell stack.

In the event of thermal runaway in one battery cell, there is a possibility that a neighboring battery cell will be damaged due to heat transfer and may also experience thermal runaway (propagation). The thermal energy released during thermal runaway is relatively short, so heat dissipation via the cooling plate is insufficient to prevent propagation.

Furthermore, from the CN 212 967 812 U A battery module is known which comprises a cell stack with battery cells. A layer of phase-change material is inserted between the cell stack and a cooling plate, as well as between the battery cells themselves.

From the DE 10 2009 045 271 A1 A battery with a number of battery cells is known, wherein the battery cells are contained in a first container. The first container is separated from a second container by a separating element. This enables the creation of a pressure difference for gas expansion from the first container into the second container.

In the US 2016 / 0 264 018 A1 relates to a device for the thermal management of a battery with electrical accumulator cells assembled in a rigid housing, wherein the device comprises heat storage means built into the battery with a chamber containing a phase change material and having a volume for heat exchange with the accumulator cells.

In the US 2022 / 0 021 046 A1 A multi-core lithium-ion battery is disclosed. This battery comprises a housing with a base and a plurality of side walls defining one or more cavities and an internal volume, wherein a plurality of cavities are formed within the internal volume of the housing. The battery further comprises a first cover plate, which is substantially flush with the base with respect to the housing, to enclose the internal volume of the housing. A plurality of lithium-ion core elements are arranged within the housing, with one of the lithium-ion core elements being located in one of the cavities. A filler material is arranged in one of the cavities such that it is positioned close to the lithium-ion core element.

From the DE 20 2023 100 851 U1 A thermal device is known. This device comprises several cells of an electric accumulator battery arranged in a housing bounded by a first circumferential wall. The device further comprises means for thermal management of the cells, including a shell having a volume that can contain a liquid heat-absorbing substance capable of phase change between liquid and gas, and which is arranged around the cells in thermal contact with at least a portion of the cells. The device further comprises a connection between the volume and the external environment, the connection being defined as a drain capable of releasing vapor.

In the DE 10 2021 200 906 A1 A battery is described that has a plurality of battery cells and at least one cell connector which connects at least two battery cells in series and/or parallel. The cell connector contains at least one cavity which is filled with at least one working fluid.

The invention is based on the objective of providing a battery in which, in the event of thermal runaway in one of its battery cells, neighboring battery cells are particularly effectively protected. are. Furthermore, a motor vehicle with such a battery should be specified.

With regard to the battery, the problem is solved according to the invention by the features of claim 1. With regard to the motor vehicle, the problem is solved according to the invention by the features of claim 10. Advantageous embodiments and further developments are the subject of the dependent claims. The statements relating to the battery apply mutatis mutandis to the motor vehicle and vice versa.

The battery is preferably a traction battery, i.e., a high-voltage battery for an electrically powered motor vehicle.

The battery comprises a cell stack with, expediently, prismatic battery cells. Thus, the battery includes the battery cells, which are arranged side by side in a longitudinal stack direction, particularly in alignment. A phase-change material is arranged between two adjacent battery cells. Preferably, a layer of the phase-change material is arranged between these battery cells; thus, the phase-change material is formed in a plate-like form and arranged between the battery cells. Expediently, the phase-change material covers more than half, and in particular more than three-quarters, of the battery cell with respect to the longitudinal stack direction. Most preferably, the phase-change material completely covers the respective battery cell with respect to the longitudinal stack direction.

Preferably, phase-change material is arranged between all battery cells in the cell stack. Alternatively, phase-change material is arranged in the cell stack only after every second battery cell, after every third battery cell, after every fourth battery cell, after every fifth battery cell, etc., in the longitudinal direction of the stack.

The phase change material is suitably selected such that it changes its phase from solid to liquid within a predetermined temperature range. This temperature range is determined by the cell chemistry used. The temperature range is chosen such that during normal battery operation, in which no thermal runaway occurs in any of the battery cells, the phase change material remains solid. In the event of a fault, when one of the battery cells experiences thermal runaway, the phase change material melts due to heat transfer from the runaway cell. For example, the temperature range is chosen to be between 60°C and 100°C, between 80°C and 150°C, or between 100°C and 200°C. Paraffin is used as a phase change material, for instance.

The battery also includes a base plate. This is, for example, part of a battery housing. In particular, the base plate forms an underride guard (underbody protection).

The base plate, particularly in the area of the phase change material, contains a reservoir for the phase change material when it melts. This reservoir is fluidically connected to a receiving space between the battery cells, in which the phase change material is located. In the intended battery installation, the reservoir is advantageously positioned below the phase change material or below the receiving space for the phase change material formed between the battery cells.

The reservoir is (under normal operating conditions) suitably free of liquids and solids. In particular, no phase-change material is located in the reservoir (under normal operating conditions).

In summary, during normal battery operation, when the battery cell temperature is below the specified temperature range for the phase change of the phase change material, the phase change material is solid. In the event of a fault, particularly thermal runaway in one of the battery cells between which the phase change material is located during normal operation, heat is transferred from the faulty battery cell to the phase change material, causing it to melt. The now liquid phase change material flows into the reservoir and is thus collected there. If the reservoir is located below the space formed between the battery cells for the phase change material, the molten phase change material flows away automatically due to gravity. As a result, a cavity, in particular a gap, is formed between the adjacent battery cells. Advantageously, this results in thermal decoupling of the faulty, especially the runaway, battery cell from the adjacent battery cell. In summary, damage to the adjacent battery cell and/or propagation of thermal runaway are advantageously prevented. The adjacent battery cells are therefore particularly effectively protected.

Preferably, the reservoir is designed in such a way that all the phase change material can be absorbed when it has melted.

For example, the reservoir is fluidically connected and/or connectable to the battery's surroundings, i.e., to the area on the outer side of the base plate facing away from the battery cells. For this purpose, the reservoir is, for example, through the entire base plate. Alternatively, the reservoir, particularly on its side facing away from the battery cells, is openably sealed. For example, the reservoir is sealed by means of the phase change material, preferably fluid-tight. Furthermore, for example, the reservoir is sealed by means of a closure that melts upon contact with the liquid phase change material, by means of a controllable, particularly temperature-controlled, valve or pressure valve, a rupture disc, or the like. If the phase change material sealing the reservoir or the closure melts, the valve opens, or the rupture disc ruptures, the liquid phase change material is released through the reservoir into the battery's environment. In this variant, the reservoir thus forms an outlet or passage for the liquid phase change material to the outside of the battery.

For example, the phase-change material arranged between adjacent battery cells is contained within a shell, such as a housing or a pouch, which is fluidically connected to the reservoir. This prevents the phase-change material from saturating or wetting other battery components, such as a compression pad, when it melts. The shell is preferably designed so that it does not melt even when exposed to heat from the defective battery cell. For example, the shell may be made of or contain mica.

According to a preferred embodiment, the reservoir is thermally insulated. For example, the reservoir walls are coated, provided with a thermally insulating lining (e.g., made of plastic), or constructed of a thermally insulating material. This prevents heat transfer from the molten phase-change material contained in the reservoir to the battery, particularly to its base plate and/or any cooling plate present in the battery. In this way, solidification, or hardening, of the molten phase-change material is prevented. Consequently, the phase-change material is prevented from resolidifying before it has flowed out of the cavity between the battery cells. The formation of the cavity and the thermal decoupling of the defective battery cell are thus achieved with comparative reliability.

According to an advantageous embodiment of the battery, it comprises a tube or hose. The tube or hose fluidly connects the reservoir for the molten phase-change material to a separate air reservoir. The air reservoir is preferably arranged above the phase-change material, particularly on the side of the phase-change material facing away from the reservoir. Most preferably, the air reservoir is adjacent to the phase-change material, i.e., directly adjacent to it. This fluid-flow connection advantageously prevents the molten phase-change material from being impeded by air present in the reservoir.

Preferably, the air reservoir is arranged inside the battery housing, which is suitably sealed in a fluid-tight manner.

In addition to or as an alternative to using the pipe or hose, it is preferable to arrange such an air reservoir directly above the phase change material, advantageously in a region between the battery cells between which the phase change material is inserted. This advantageously ensures that, in the event of thermal runaway in one of the battery cells adjacent to the air reservoir, the air in the reservoir is heated. This, in turn, increases the air pressure on the melting phase change material, thus accelerating the flow of the molten phase change material into the reservoir.

According to a suitable design, the pipe or hose penetrates the phase change material arranged between the battery cells in a space-saving manner.

The pipe or hose is preferably made of, or encloses, a thermally conductive material such as copper. In this way, even when heat is transferred from the battery cell to a relatively small area of the phase change material, the heat is distributed relatively well via the pipe or hose, so that the entire phase change material melts relatively quickly.

Alternatively or additionally, the phase change material is embedded in an open-pore metal foam. In other words, the phase change material is introduced into the open, fluidically interconnected pores of the metal foam. Put another way, the pore walls of the metal foam are positioned within the phase change material. The metal foam ensures a relatively homogeneous distribution of any heat acting on the phase change material, so that the entire phase change material is comparatively... It melts quickly. Due to the open-pored nature of the metal foam, the flow of the molten phase-change material is not hindered or only slightly impeded.

According to a suitable battery configuration, a compression pad is additionally arranged between the battery cells between which the phase-change material is located. Thus, the compression pad is placed between each battery cell and the phase-change material. For example, only a single compression pad is arranged between the two adjacent battery cells. Alternatively, a compression pad is arranged on both sides of the phase-change material with respect to the longitudinal direction of the stack, so that a compression pad is provided between the phase-change material and each of the two adjacent battery cells.

The compression pad serves in particular to compensate for fluctuations in the amount of mechanical preload of the battery cells.

According to a suitable further development, a cooling plate for temperature control of the battery cells is arranged between the battery cells and the base plate. The cooling plate is thus positioned between the cell stack and the base plate. This cooling plate has a passage, for example a hole, through which the molten phase-change material can flow into the reservoir of the base plate. The passage is preferably thermally insulated, analogous to the reservoir, so that the molten phase-change material does not solidify in the passage and block it.

Alternatively or additionally, a (further) cooling plate for temperature control of the battery cells is arranged on the upper side of the battery cell facing away from the base plate, i.e. on the side which is oriented parallel to the underside facing the base plate.

According to an advantageous embodiment, a channel for a cooling medium is additionally or alternatively arranged in the phase-change material. In other words, the phase-change material is penetrated by the channel, so that the cooling medium flows within the phase-change material. Alternatively, two plates or layers of the phase-change material, spaced apart from each other in the longitudinal direction of the stack, are arranged between the two adjacent battery cells, with the channel for the cooling medium running between the two layers or plates of the phase-change material. Consequently, in both of these variants, direct temperature control of the phase-change material is possible, particularly during normal operation.

Heat transfer through the comparatively large surface area of the battery cells is particularly advantageous here.

According to a suitable embodiment, the extent of the phase change material in the longitudinal direction of the stack, i.e., its thickness, is between 0.5 mm and 2.0 cm, particularly between 2 mm and 5 mm. At such a thickness, a sufficiently large cavity for the thermal decoupling of the battery cells is formed after melting, while minimizing the additional space required.

Another aspect of the invention relates to a motor vehicle with a battery configured in one of the variants described above. In particular, the motor vehicle is an electrically powered motor vehicle. The battery is advantageously a traction battery, i.e., a high-voltage battery, for providing electrical energy for a traction drive, especially for its electric motor.

• 1 schematisch ein elektrisch angetriebenes Kraftfahrzeug, dessen Batterie einen Zellstapel mit Batteriezellen aufweist, wobei jeweils zwischen zwei der Batteriezellen ein Phasenwechselmaterial angeordnet ist,
• 2a,b schematisch und ausschnittsweise die Batterie in einer ersten Variante im Normalzustand bzw. bei einem thermischen Durchgehen einer der Batteriezellen,
• 3a,b schematisch und ausschnittsweise die Batterie in einer zweiten Variante im Normalzustand bzw. bei einem thermischen Durchgehen einer der Batteriezellen,
• 4a,b schematisch und ausschnittsweise die Batterie in einer dritten Variante im Normalzustand bzw. bei einem thermischen Durchgehen einer der Batteriezellen,
• 5a,b schematisch und ausschnittsweise die Batterie in einer vierten Variante im Normalzustand bzw. bei einem thermischen Durchgehen einer der Batteriezellen, und
• 6a,b schematisch und ausschnittsweise die Batterie in einer fünften Variante im Normalzustand bzw. bei einem thermischen Durchgehen einer der Batteriezellen.

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

• 1 schematically an electrically powered motor vehicle whose battery has a cell stack with battery cells, wherein a phase change material is arranged between each two of the battery cells,
• 2a ,b schematically and in part, the battery in a first variant in normal state or in the event of thermal runaway of one of the battery cells,
• 3a ,b schematically and in part, the battery in a second variant in normal state or in the event of thermal runaway of one of the battery cells,
• 4a ,b schematically and in part, the battery in a third variant in normal state or in the event of thermal runaway of one of the battery cells,
• 5a ,b schematically and in part, the battery in a fourth variant in the normal state or in the event of a thermal runaway of one of the battery cells, and
• 6a ,b schematically and in part the battery in a fifth variant in normal state or in the event of thermal runaway of one of the battery cells.

Corresponding parts and sizes are always marked with the same reference symbols in all figures.

In the 1 The figure schematically depicts an electrically powered motor vehicle 2. This vehicle includes a battery 4, which, according to the embodiment shown here, forms the traction battery (high-voltage battery) of the motor vehicle 2. The battery 4 supplies a traction drive with electrical energy. For this purpose, the battery 4 is electrically connected to an inverter 6, which converts the direct current (DC) supplied by the battery 4 into alternating current (AC) for an electric motor 8 of the traction drive.

The battery 4 comprises a battery housing 10, which is expediently sealed to be fluid-tight. The battery housing 10 contains at least one cell stack 12 with a plurality of battery cells 14 arranged one behind the other in the longitudinal direction L of the stack. The battery cells 14 are designed as so-called prismatic battery cells 14. These thus comprise a cuboid cell housing, wherein the two terminals 16, i.e., the two poles, of each battery cell 14 are arranged on opposite, and therefore parallel, narrow sides 18 of the cell housing, preferably on opposite short narrow sides. The short narrow sides 18 are the two sides of the cuboid cell housing with the smallest area. The two base sides 20 of the cell housing, i.e., the two sides of the cuboid cell housing with the largest area, are expediently oriented perpendicular to the longitudinal direction L of the stack. To provide electrical energy, the battery cells 14 are electrically connected in series and/or parallel in a manner not shown in detail.

As in the 1 as in the 2a to 6b As can be seen, a phase change material 22, in particular a layer of phase change material 22 also referred to as a phase change material layer, is introduced between each pair of battery cells 14 that are successive in the longitudinal direction L of the stack, i.e., between adjacent battery cells 14 in the longitudinal direction L of the stack. For example, paraffin is used as the phase change material 22.

In this embodiment, at least one compression pad 24 is arranged between adjacent battery cells 14. According to the embodiment shown here, a compression pad 24 is arranged between the phase-change material 22 and each of the battery cells 14. In other words, the phase-change material 22 is flanked by the compression pads 24 in the stacking longitudinal direction L.

The thickness d of the phase change material 22, in other words the extent of the phase change material in the stack longitudinal direction L of the cell stack 12, is between 0.5 mm and 2.0 cm, in particular between 2 mm and 5 mm.

In the 2a to 6b Battery 4 is each partially divided according to the cutting plane E of the 1 The figure shows only three of the battery cells 14 arranged side by side in the longitudinal stacking direction L. 2a , 3a , 4a , 5a , 6a The images show battery 4 in a normal state, i.e., in normal operation, in which none of the battery cells 14 experience thermal runaway. 2b , 3b , 4b , 5b , 6b Each shows battery 4 in the event of a fault, as if one of the battery cells 14 (in the figures, the middle one is shown as an example, which is represented by lightning and clouds) thermally fails.

As further in the 2a to 6b As can be seen, the battery 4 comprises a base plate 26, which here is exemplified as the base of the battery housing 10 and forms an underride guard for the battery 4 and/or the motor vehicle 2. The battery cells are thus arranged in a vertical direction H above the base plate 26, oriented perpendicular to the base plate 26 and the stacking longitudinal direction L. The base plate 26 includes a reservoir 28 in the area between adjacent battery cells for the phase-change material 22 arranged between these battery cells. As long as the phase-change material is solid, the reservoir 28 is free of liquid and solids.

Reservoir 28 is fluidically connected between the respective battery cells 14 to a space containing the solid phase-change material 22. If the phase-change material 22 located between the battery cells 14 melts, particularly due to thermal runaway in one of the battery cells 14, the now liquid phase-change material 22 flows automatically into reservoir 28 due to gravity acting against the vertical direction H, thus forming a corresponding cavity 30 between the adjacent battery cells 14. Reservoir 28 therefore forms a receiving space for the phase-change material 22 when it melts. The formation of the cavity 30 results in thermal decoupling of the thermally runaway battery cell 14 from adjacent battery cells 14.

Reservoir 28 is, as in the 2a and 2b shown, optionally thermally insulated, especially in contrast to the base plate 26 and/or a cooling plate 34 (see below). For this purpose, the walls of the reservoir 28 are provided with a thermally insulating layer 32. According to variants not shown further, the reservoir 28 is in the design variants of 3a to 6b thermally insulated in an analogous manner.

The variant is optional in the 2a to 6b The phase change material 22 is contained in a housing or bag, collectively enclosed in a shell 36, which is fluidically connected to the reservoir via a hole. The shell 36 is shown in dashed lines as an example of one of the layers of the phase change material 22 in the 3a and 3b hinted at.

According to the variants of battery 4 according to the 3a In sections 4a,b and 6a,b, the battery comprises a (lower) cooling plate 34, which is arranged between the base plate 26 and the battery cells 14. This cooling plate has a cooling channel 38 through which a cooling medium flows to regulate the temperature of the battery cells 14. The lower cooling plate 34 includes perforated openings 40 through which the molten phase-change material 22 can flow from the area between the battery cells 14 into the corresponding reservoir 28 of the base plate 26. In summary, the lower cooling plate 34 is arranged between the base plate 26 and the cell stack 12 with respect to the vertical direction H.

According to the variant of battery 4 according to the 5a ,b the battery 4 comprises an (upper) cooling plate 34. This is arranged on the top side of the battery cells 14, in other words on the long narrow side of the battery cells 14 facing away from the base plate 26. In other words, the upper cooling plate 34 is mounted above the cell stack 12 with respect to the vertical direction H and preferably in contact with it.

According to the embodiments of the variants of battery 4, which are not shown further below, according to the 2a to 6b These have the upper and/or the lower cooling plate 34.

According to the variant of battery 4 according to the 2a and 2b Two layers of phase-change material 22 are arranged between adjacent battery cells 14. A channel 42 for a cooling medium 44 is arranged between these two layers of phase-change material 22 with respect to the longitudinal stacking direction L. In this way, a comparatively effective temperature control of the corresponding battery cells 14 is achieved via their base 20.

According to one variant not shown further, channel 42 is incorporated into the phase change material 22, i.e., arranged within it.

According to the variant of battery 4 according to the 6a and 6b The phase change material 22 is embedded in an open-pored metal foam 46. When the phase change material 22 melts, the cavity 30 is formed by means of the then empty pores of the metal foam 46.

Alternatively or additionally, the variants of battery 4 show the following: 4a to 5b that a tube 48 is inserted into the phase change material 22. In an analogous manner, but not shown further, a hose is used instead of the tube.

The pipe 48 penetrates the phase change material 22, or the phase change material layer, in the vertical direction H. Consequently, the reservoir 28 is fluidically connected to an air reservoir 50 located above the phase change material 22, i.e., to an air-filled space. The pipe 48 opens into the reservoir 28 at one end and into the air reservoir 50 at the other. As in the variant of 5 and 5b As shown, the air reservoir 50 is formed, for example, by means of a recess in the upper cooling plate 34.

Optionally, the tube 48 is made of a thermally conductive material, such as copper.

Based on the tube 48 made of thermally conductive material or on the metal foam 46, a comparatively homogeneous distribution of heat is achieved, which may act on the phase change material 22.

Optionally, in all variants, the reservoir 28 is fluidically connected and/or connectable to the environment of the battery 4, i.e., to the area on the outside of the base plate 26 facing away from the battery cells 14, in a manner not shown further, so that the molten phase change material can flow out to the outside of the battery.

The invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived by a person skilled in the art within the scope of the claims, without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiments and/or in the claims can also be combined in other ways. Binary, without leaving the subject matter of the invention.

Reference symbol list

2

motor vehicle

4

battery

6

inverter

8

electric motor

10

Battery housing

12

Cell stack

14

Battery cell

16

terminal

18

narrow side

20

Base

22

Phase change material

24

Compression pad

26

base plate

28

reservoir

30

cavity

32

thermally insulating layer

34

Cooling plate

36

Covering

38

Cooling channel

40

passage

42

channel

44

Cooling medium

46

metal foam

48

Pipe

50

air reservoir

d

Thickness of the phase change material

H

Upward direction

L

Stacking direction

Claims (10)

Battery (4) for a motor vehicle (2), comprising - a cell stack (12) with battery cells (14), - wherein a phase change material (22), in particular a solid, is arranged between two adjacent battery cells (14), characterized in that a reservoir (28) for the phase change material (22) is arranged in a base plate (26) when it melts. Battery (4) after Claim 1 , characterized in that the reservoir (28) is thermally insulated. Battery (4) after Claim 1 or 2 , characterized by a pipe (48) or a hose, wherein the pipe (48) or the hose connects the reservoir (28) to an air reservoir (50) in a fluid-technical manner. Battery (4) after Claim 3 , characterized in that - the tube (48) or the hose extends through the phase change material (22), and/or - that the tube (48) or the hose is made of thermally conductive material. Battery (4) after one of the Claims 1 until 4 , characterized in that the phase change material (22) is contained in an open-pore metal foam (46). Battery (4) after one of the Claims 1 until 5 , characterized in that a compression pad (24) is arranged between the battery cells (14) between which the phase change material (22) is arranged. Battery (4) after one of the Claims 1 until 6 , characterized in that a cooling plate (34) is arranged between the battery cells (14) and the base plate (26) and/or on the upper side of the battery cells (14) facing away from the base plate (26). Battery (4) after one of the Claims 1 until 7 , characterized in that - a channel (42) for a cooling medium (44) is arranged in the phase change material (22), or - two layers of the phase change material (22) are arranged between the adjacent battery cells (14), wherein the channel (42) for the cooling medium (44) is arranged between the two layers of the phase change material (22). Battery (4) after one of the Claims 1 until 8 , characterized in that the extent of the phase change material (22) in a stack longitudinal direction (L) of the cell stack (12) is between 0.5 mm and 2.0 cm, in particular between 2 mm and 5 mm. motor vehicle (2) with a battery (4) according to one of the Claims 1 until 9 .