Battery cooling system, battery modules, and aircraft

Abstract

The present invention relates to a battery cooling device, a battery module, and an aircraft, the battery cooling device being used to cool at least one battery cell (1) of an electric aircraft and having a latent heat accumulator (3). Importantly, a multi-layer system is arranged around the battery cell, the multi-layer system comprising at least two layers composed of fire-resistant material and one layer composed of phase change material of the latent heat accumulator (3), the inner layer (2) of the multi-layer system facing the battery cell (1) and the outer layer (4) of the multi-layer system facing the surrounding environment being composed of the fire-resistant material, and an intermediate layer disposed between the inner layer (2) and the outer layer (4) being composed of phase change material of the latent heat accumulator (3), and the fire-resistant material being configured to form at least two layers, the first layer (2.1, 4.1) of the fire-resistant material being configured as a mechanically stable layer, and the second layer (2.2, 4.2) of the fire-resistant material comprising a hydrated material.

Description

Technical Field

[0001] This invention relates to a battery cooling device for cooling at least one battery cell in an electric aircraft. The invention also relates to a battery module and a vertical takeoff and landing (VTOL) aircraft. Background Technology

[0002] Electric or partially electric (hybrid) powered aircraft are typically powered by batteries. These batteries require controlled thermal management to ensure that the battery cells do not reach critical temperatures during operation. Otherwise, in the event of overheating or mechanical damage, the separators inside the battery cells may break down, leading to internal short circuits and the resulting exothermic reaction, known as thermal runaway.

[0003] To address this, it is known from existing technology that so-called phase change materials (PCMs), also known as latent heat storage devices, are used to cool battery cells. For example, such a solution is described in document US 2015 / 0037647A1. Unlike conventional materials, these PCMs have a constant phase change temperature. This means that heat can be supplied to or extracted from the latent heat storage device during its phase change without a change in temperature. By absorbing heat, the PCM in the latent heat storage device undergoes a phase change, for example, from solid to liquid / viscous.

[0004] The disadvantage of this prior-known solution in the prior art is that phase change materials are typically designed for temperature ranges suitable for cooling battery cells during operation, or only designed to protect the battery in significantly higher temperature ranges (typically several hundred degrees Celsius) to provide protection in the event of thermal runaway. Furthermore, phase change materials lack mechanical stability and cannot protect adjacent battery cells from metal fragmentation or flames in the event of thermal runaway, nor can they prevent battery cells from exploding.

[0005] From a safety perspective, this existing solution is also disadvantageous because common phase change materials begin to melt when the battery cell experiences thermal runaway due to high temperatures, and then either evaporate or burn. Due to vapor pressure, the burning droplets of the molten PCM material will be dispersed inside the battery casing, which should be avoided. Summary of the Invention

[0006] The object of the present invention is therefore to eliminate the disadvantages of existing battery cooling devices and, in particular, to improve safety and fire protection.

[0007] The objective is achieved by the battery cooling device provided by the present invention. Advantageous design solutions are given in the additional embodiments. Furthermore, the objective is also achieved by the battery module and aircraft provided by the present invention. Advantageous embodiments of the aircraft are given in the corresponding additional embodiments. To avoid repetition, these solutions are explicitly included in the specification.

[0008] As is known per se, according to the present invention, a battery cooling device for cooling at least one battery cell of an electric aircraft includes a latent heat accumulator. The latent heat accumulator is designed to absorb heat generated by the battery during operation and cool the battery through isothermal changes of state.

[0009] Importantly, a multi-layer system is arranged around the battery cell, comprising at least two layers of fire-resistant material and one layer of phase change material from a latent heat accumulator. Here, the inner layer of the multi-layer system facing the battery cell and the outer layer facing the surrounding environment are made of fire-resistant material. An intermediate layer between the inner and outer layers is made of the phase change material from the latent heat accumulator. The fire-resistant material layers are configured to form at least two layers, wherein the first fire-resistant material layer is configured as a mechanically stable layer, and the second fire-resistant material layer comprises a hydrated material.

[0010] Therefore, the minimum layer sequence of the multilayer system consists of at least five layers: an inner layer of fire-resistant material adjacent to the battery cell, followed by a phase change material layer of the latent heat storage device. The multilayer system is externally enclosed by at least one additional layer of fire-resistant material. The inner and outer fire-resistant layers are also constructed as double layers: the first layer of the inner layer, composed of fire-resistant material, is constructed as a mechanically stable layer, and the second layer of the inner layer, composed of fire-resistant material, is constructed as a hydrating material. Similarly, the first layer of the outer layer, composed of fire-resistant material, is constructed as a mechanically stable layer, and the second layer of the outer layer, composed of fire-resistant material, is also constructed as a hydrating material.

[0011] Within the scope of this specification, the terms "layer," "wound structure," or "layer structure" may be used interchangeably.

[0012] In the event of thermal runaway in a battery cell, the high temperatures generated during this runaway are absorbed by the hydrated material in the second layer, which is composed of fire-resistant material. This material undergoes a phase transition and thus can absorb at least a portion of the energy released as heat while maintaining a constant temperature. Furthermore, the first layer of fire-resistant material, designed to be mechanically stable, prevents the battery cell from bursting. This protects adjacent battery cells from critical temperatures and mechanical damage caused by metal fragments or the like. Therefore, adjacent battery cells will not spontaneously enter the critical temperature range that would also lead to thermal runaway in adjacent cells.

[0013] In a preferred embodiment of the invention, the phase change material of the latent heat accumulator is macroscopically encapsulated within a carrier matrix. This achieves the advantage that the material does not flow.

[0014] The phase change material (PCM) of the latent heat accumulator is preferably constructed as a slotted cylindrical sleeve, which is disposed between two layers of at least two fire-resistant materials on a cylindrical battery cell. The heat absorbed by the PCM in the latent heat accumulator during operation is related to the latent heat and the heat capacity of the latent heat material. This results in a preferably isothermal phase change in the PCM. The discharge process of the battery cell typically occurs during flight operation. The slotted shape of the sleeve composed of PCM ensures that the sleeve can be fitted onto the inner layer of fire-resistant material. Good thermal contact is achieved by surrounding and wrapping with the outer layer of fire-resistant material, preferably a self-adhesive fire-resistant material, through the pressure created. In this way, the heat of the battery cell can be transferred through the inner fire-resistant material into the sleeve made of PCM.

[0015] In a preferred embodiment of the invention, the first layer of the fire-retardant material is constructed of a fibrous material, particularly glass fiber, ceramic fiber, and / or basalt fiber. This provides the advantage of achieving sufficient mechanical stability in the first layer of the fire-retardant material in a simple manner and form.

[0016] The first layer of fire-retardant material is preferably wrapped tightly around the battery casing as a mechanical protective structure, thus eliminating gaps between the battery cells and the mechanically stabilizing fibers. This prevents the battery cells from bursting in the event of thermal runaway.

[0017] The second layer of the fire-retardant material is preferably constructed with a hydrated material, particularly with at least one metal hydrate. The hydrated material acts as a coolant for the minerals, absorbing a large amount of heat when heated above a defined limit temperature. This effect is based on the evaporation of water contained in the hydrated minerals. Through this evaporation, a large amount of heat can be absorbed via a substantially isothermal reaction.

[0018] The latent heat accumulator and at least two layers of self-adhesive fire-resistant material are arranged as follows:

[0019] An inwardly wound structure of fire-retardant material is provided around the battery casing of the battery cell. Here, the first layer of fire-retardant material consists of mechanically stabilizing fibers and adhesive strips, the adhesive strips securing the fibers to the battery casing of the battery cell. The fibers prevent the battery cell from bursting laterally, i.e., on its circumferential surface, under overpressure during thermal runaway (such as overpressure occurring when the CID valve is blocked). For the best possible stability, it is advantageous that the mechanically stabilizing first layer is directly adhered to the peripheral wall of the battery cell.

[0020] The second layer of the fire-retardant material consists of a layer of hydrated minerals, such as water of crystallization. This layer is used to absorb heat released during thermal runaway by causing the water contained within it to evaporate. During the phase transition of the hydrated minerals, the temperature of the material can remain constant. Another effect of the resulting water vapor is that it displaces oxygen from the air, which provides a beneficial fire-resistant effect to adjacent components.

[0021] A latent heat accumulator is installed after the inner winding structure of the fire-retardant material, preferably a latent heat accumulator with a slotted cylindrical sleeve. The slotting allows for compensation of any resulting tolerances. During normal battery operation, the heat generated is introduced into the latent heat accumulator through the fire-retardant material of the first winding structure. No phase change occurs in the fire-retardant material because the required temperature is designed to be high (>100°C), such that a phase change only occurs in the event of thermal runaway. Instead, in the latent heat accumulator, the melting point is preferably designed to occur during discharge in normal battery operation; this melting point is preferably in the range of 30°C to 60°C, and particularly preferably about 43°C. 49℃. To prevent the phase change material (PCM) of the latent heat accumulator from flowing during the PCM phase change, the PCM is embedded in the carrier material in a macroscopically encapsulated form. To ensure good thermal contact between the slotted sleeve made of PCM and the inner winding structure of the fire-resistant material, a second outer layer of the fire-resistant material is wound around the outer side of the sleeve. The tight winding generates a compressive force, which achieves good thermal contact. Another advantage of this arrangement is that the latent heat accumulator is cooled from both sides in the event of thermal runaway and is surrounded from both sides by a water vapor layer, which enhances the fire resistance.

[0022] Since the latent heat accumulator and its carrier matrix may begin to melt and evaporate during thermal runaway despite cooling on both sides, it is preferable to vent the vapors of the evaporated composite material, especially the vapors of the evaporated phase change material, in order to prevent overpressure, which could damage the fire-resistant material of the battery cell.

[0023] In another preferred embodiment of the invention, the battery cell has a safety valve in the form of a vent valve. If the battery cell overheats to the point of ignition, the vent valve can automatically open and allow hot combustion gases to escape from the battery cell in the event of thermal runaway. If the vent valve becomes blocked in the event of thermal runaway, the mechanically stable fiber-like mechanical protective structure of the fire-retardant material described above prevents the battery cell from splitting laterally, but rather splits on the upper or lower side of the battery cell, thereby allowing controlled venting.

[0024] Furthermore, the present invention is achieved through a battery module having a battery cooling device and multiple battery cells. Importantly, the battery cooling device is configured as described above.

[0025] The battery cells are preferably constructed as spherical batteries. This provides the advantage that the battery module is mechanically stable.

[0026] The invention is also realized by an aircraft having the battery module. Preferably, the aircraft is configured as a vertical takeoff and landing electric aircraft.

[0027] This invention is particularly suitable for applications in safety-critical fields, such as manned and unmanned air traffic, especially for the applicant's electric vertical takeoff and landing aircraft and the applicant's battery modules, for example, for application filed on March 5, 2020, entitled "Batteriekühlvorrichtung und Verfahren zur Kühlungeiner Batteriezelle eines elektrisch angetriebenen". ” and “Verfahrenzur Kühlung einer Batterie und Kühlsystem”. Attached Figure Description

[0028] Further preferred features and implementations will be described below with reference to embodiments and accompanying drawings. These embodiments and any dimensions given are merely preferred designs of the invention and are therefore not limiting.

[0029] here:

[0030] Figure 1 A cross-sectional view of a first embodiment of a battery cooling device according to the present invention is shown. Detailed Implementation

[0031] exist Figure 1 The figure shows a cross-sectional view of battery cell 1. Battery cell 1 is a circular battery and is constructed in a cylindrical shape. The longitudinal extension of battery cell 1 is perpendicular to the plane of the figure.

[0032] An inner layer 2 made of fire-resistant material is provided around the battery casing of battery cell 1. The inner layer 2 of fire-resistant material is currently constructed as a two-layer structure.

[0033] Here, the first layer 2.1 of the fire-retardant material is currently composed of mechanically stable fibers. In the present case, the first layer 2.1 of the fire-retardant material contains glass fibers. The first layer 2.1 of the fire-retardant material is constructed to be self-adhesive by means of an adhesive strip that adheres to the battery casing of the battery cell and secures the inner fire-retardant layer to the battery casing of the battery cell 1. The mechanically stable fibers prevent the battery cell 1 from bursting laterally, i.e., on the circumferential surface, in the event of overpressure during thermal runaway (such as overpressure occurring when the CID valve is blocked).

[0034] The second layer 2.2 of the fire-retardant material consists of a layer of hydrated minerals, such as, for example, water of crystallization. The second layer 2.2 of the fire-retardant material is designed to absorb temperatures of several hundred degrees Celsius, approximately 600°C in the current conditions, substantially isothermally, at which point a phase transition occurs. This layer 2.2 is used to absorb heat released during thermal runaway by causing the water contained in the hydrated minerals to evaporate.

[0035] Therefore, in the event of thermal runaway of battery cell 1, the temperature jump can be buffered, thereby protecting adjacent batteries and preventing them from entering the critical temperature range, in which battery cell 1 will also enter a state of thermal runaway.

[0036] A latent heat accumulator 3 is sleeved around the fire-resistant material of the battery cell 1 and the inner layer 2. The latent heat accumulator 3 is made of a slotted cylindrical sleeve-shaped phase change material.

[0037] During normal battery operation, the heat generated is transferred to the latent heat accumulator 3 through the inner layer 2 made of fire-resistant material. Here, the second layer 2.2 of the fire-resistant material does not undergo a phase change because the temperature required for this (>100°C) has not been reached.

[0038] In the latent heat storage device 3, the melting point is designed such that it falls within the temperature range that occurs during normal operation (flight operation) of the battery cell 1. Currently, the temperature range during normal operation is approximately 43°C. 49℃. This temperature range can be selected by choosing the phase change material of the latent heat accumulator 3.

[0039] To prevent the phase change material of the latent heat accumulator 3 from starting to flow during the phase change, it is macroscopically encapsulated and embedded in the carrier matrix.

[0040] An outer layer 4, composed of fire-resistant material, is disposed around a sleeve made of phase change material. To ensure good thermal contact between the slotted sleeve made of phase change material and the inner layer 2 made of fire-resistant material, the outer layer 4 made of fire-resistant material is wound around the outer side of the sleeve made of phase change material. The tight winding generates compressive force, which enables good thermal contact.

[0041] In the present case, similar to the inner layer made of fire-resistant material, the outer layer 4 made of fire-resistant material is also constructed as a two-layer structure. The first layer 4.1 of the fire-resistant material is constructed to have fibrous material and is thus mechanically stable. In the present case, the first layer 4.1 of the fire-resistant material contains glass fiber.

[0042] The second layer 4.2 of the fire-retardant material is constructed as a hydrated material for very high temperatures. In the present case, the second layer 4.2 of the fire-retardant material is composed of metal hydrates, such as water of crystallization. The outer layer 4 of the fire-retardant material is also constructed to be self-adhesive, in that an adhesive strip is provided on the first layer 4.1, which is adhered to a slotted sleeve. As described above, a compressive force is generated by tight winding, which enables good thermal contact between the different layers.

[0043] The advantage of placing a latent heat accumulator made of phase change material between two layers of fire-resistant material and hydrated material is that the latent heat accumulator is cooled from both sides in the event of thermal runaway and is surrounded from both sides by a water vapor layer, which improves the fire resistance.

Claims

1. A battery cooling device for cooling cylindrical battery cells (1) of an electric aircraft, characterized in that, The battery cooling device includes: Latent heat storage device (3). A multi-layer system arranged around the battery cell (1), wherein the multi-layer system includes: The inner layer (2), facing the battery cell (1), is made of fire-resistant material. The outer layer (4), facing the surrounding environment, is made of fire-resistant material, and The intermediate layer is located between the inner layer (2) and the outer layer (4) in a direction perpendicular to the longitudinal extension of the cylindrical battery cell (1), wherein, The fire-resistant material of the inner layer (2) and the outer layer (4) is configured to form at least two layers, wherein the first layer (2.1, 4.1) of the fire-resistant material is configured as a mechanically stable layer to prevent the battery cell (1) from bursting in the event of thermal runaway, and the second layer (2.2, 4.2) of the fire-resistant material is composed of hydrated minerals, and The first layer (2.1) of the fire-retardant material constituting the inner layer (2) is directly disposed on the battery cell (1), and the second layer (2.2) of the fire-retardant material constituting the inner layer (2) is located between the first layer (2.1) and the intermediate layer of the fire-retardant material constituting the inner layer (2) in a direction perpendicular to the longitudinal extension of the cylindrical battery cell (1). The intermediate layer includes a carrier, and a phase change material is embedded in the carrier in a macroscopically encapsulated form to form a latent heat storage device (3), wherein the phase change material has a melting point in the range of 43°C to 49°C. The second layer (2.2, 4.2) of the fireproof material is designed to be suitable for the temperature range in which the battery cell generates heat during thermal runaway, the temperature range being from 100°C to 800°C.

2. The battery cooling device according to claim 1, characterized in that, The latent heat accumulator (3) is constructed of phase change material in the form of a sleeve that is grooved around the fireproof material of the inner layer (2).

3. The battery cooling device according to claim 1, characterized in that, The first layer (2.1, 4.1) of the fireproof material is constructed as a fibrous material.

4. The battery cooling device according to claim 3, characterized in that, The first layer (2.1, 4.1) of the fire-resistant material is constructed to have glass fiber, ceramic fiber and / or aramid fiber.

5. The battery cooling device according to claim 1, characterized in that, The second layer (2.2, 4.2) of the fireproof material is configured to have at least one metal hydrate.

6. The battery cooling device according to claim 1, characterized in that, The second layer (2.2, 4.2) of the fireproof material is designed to be suitable for the temperature range in which the battery cell (1) generates heat during thermal runaway, the temperature range being between 100°C and 600°C.

7. The battery cooling device according to claim 1, characterized in that, The inner layer (2) and / or the outer layer (4) composed of the fire-resistant material are configured to be self-adhesive.

8. The battery cooling device according to claim 7, characterized in that, The mechanically stable first layer (2.1, 4.1) of the fireproof material is configured as a self-adhesive type.

9. The battery cooling device according to claim 1, characterized in that, The outer layer (4) composed of the fireproof material completely surrounds the phase change material of the latent heat accumulator (3).

10. The battery cooling device according to claim 1, characterized in that, The inner layer (2) and the outer layer (4) are configured as a sleeve.

11. The battery cooling device according to claim 10, characterized in that, The inner layer (2) and the outer layer (4) are constructed into a cylindrical sleeve, and the sleeve constructed by the outer layer (4) overlaps with the phase change material of the latent heat accumulator (3) at the openings on both sides of the sleeve.

12. A battery module, comprising a battery cooling device and a plurality of battery cells (1), characterized in that, The battery cooling device is configured according to any one of claims 1 to 11.

13. An aircraft, characterized in that, Includes the battery module according to claim 12.

14. The aircraft according to claim 13, characterized in that, The aircraft is constructed as a vertical takeoff and landing electric aircraft.

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