Battery module for a traction battery of a vehicle and traction battery

Abstract

Battery module (1) for a traction battery of a vehicle, comprising - a battery module housing (2), - a battery cell arrangement (3) comprising a plurality of battery cells (3a-3g) accommodated within the battery module housing (2), - a cooling plate (4) which is attached to an upper side of the battery module housing (2) and by means of which the battery module housing (2) is closed, and - an evaporable coolant (6) which is accommodated within the battery module housing (2), wherein the battery module housing (2) is vacuumized so that a negative pressure prevails within the battery module housing (2), characterized in that the cooling plate (4) has a capillary structure (5) which is formed by a plurality of capillary channels (5a-5f) within the cooling plate (4), wherein the cooling of the battery module (1) takes place in the manner of a vapor chamber.

Description

[0001] The present invention relates to a battery module for a traction battery of a vehicle, comprising a battery module housing, a battery cell arrangement having a plurality of battery cells accommodated within the battery module housing, a cooling plate attached to an upper side of the battery module housing and by means of which the battery module housing is closed, and an evaporable coolant accommodated within the battery module housing, wherein the battery module housing is vacuum-sealed such that a negative pressure prevails within the battery module housing. Furthermore, the present invention relates to a traction battery of a vehicle comprising a number n ≥ 1 of battery modules.

[0002] Vehicles that have at least one electric motor as their drive device are equipped with a traction battery, which forms an electrochemical storage device for electrical energy to power the electric motor during operation. Such a traction battery is typically a high-voltage battery with a number of battery modules. Each of these battery modules, in turn, comprises a plurality of battery cells housed in a battery module housing.

[0003] During operation, the battery modules must be cooled appropriately. For example, it is known from the prior art to control the temperature of battery modules using a cooling plate, direct cooling, or air cooling. Each of these cooling options has certain advantages and disadvantages with regard to cooling performance and temperature spread.

[0004] From DE 10 2017 005 593 A1, it is known to heat a coolant of a lithium-ion high-voltage battery during operation and thereby evaporate it. Due to the capillary effect, the coolant is drawn upwards through a porous material to the end region of the battery cells. The vaporous coolant, thus in the gas phase, then flows back through fluid channels, driven by gas pressure, to a cooling device serving as a heat sink, where it condenses.

[0005] From FR 3 085 556 A1, a battery module of the type mentioned above is known, in which a cooling plate, by means of which the battery module housing is closed, has a plurality of cooling fins on its underside.

[0006] DE 10 2012 220 873 A1 discloses a battery module with a plurality of battery cells, wherein a cooling plate is arranged between adjacent battery cells, each of which comprises a heat pipe extending vertically at opposite edges. The heat pipes contain a heat transfer fluid that can change from a liquid to a gas phase under the influence of a heat source, then condenses back into the liquid phase at a heat sink and is transferred back to the heat source by gravity or a capillary system, so that this cycle can be repeated.

[0007] The present invention has for its object to provide a battery module for a traction battery of a vehicle of the type mentioned at the outset as well as a traction battery of the generic type, which enable further improved cooling in a simple manner.

[0008] This object is achieved by a battery module of the type mentioned above having the features of the characterizing part of claim 1. With regard to the traction battery, this object is achieved by a generic traction battery having the features of the characterizing part of claim 6. The subclaims relate to advantageous developments of the invention.

[0009] A battery module according to the invention is characterized in that the cooling plate has a capillary structure formed by a plurality of capillary channels within the cooling plate, wherein the cooling of the battery module occurs in the manner of a vapor chamber. In the present invention, the battery module is thus cooled in the manner of a vapor chamber. During manufacture of the battery module, the battery module housing is first vacuumized so that a negative pressure is generated therein. The evaporable coolant is then introduced into the battery module housing. During operation, the coolant evaporates due to the waste heat from the battery cells. Since a negative pressure prevails within the battery module housing, the evaporation of the coolant advantageously begins even at relatively low operating temperatures, preferably already at operating temperatures of approximately 40°C.The evaporated coolant expands and rises within the battery module housing, being transported to cooler areas of the battery module, particularly the cooling plate. The evaporated coolant condenses on the cooling plate and, due to capillary forces, is drawn into the capillary structure of the cooling plate as soon as the evaporated coolant returns to liquid. The resulting coolant condensate is then released so that it can cool the battery cells of the battery cell array again. This allows for effective cooling of the battery cells of the battery cell array in a simple manner. The capillary structure formed by a plurality of capillary channels within the cooling plate can be manufactured very easily and cost-effectively.It has been shown that it is beneficial for process stability if the cooling plate is mounted on top of the battery module housing, as the warm cell heads of the battery cells can subsequently evaporate the coolant condensate dripping from the cold cooling plate. This, in turn, has a direct positive effect on cooling performance.

[0010] In a preferred embodiment, it is proposed that the battery module housing is vacuum-sealed such that a negative pressure of approximately 0.4 bar prevails within the battery module housing. By vacuum-sealing the battery module housing to this negative pressure, the coolant can evaporate on the warm cell surfaces of the battery cells in a temperature range of approximately -40°C to approximately +60°C and then condense on the cooling plate of the battery module housing. In this way, for example, a gap between the cell surfaces of the battery cells and the battery module housing can be overcome, which was previously achieved using a gap filler. Because no gap filler is required for the battery module presented here, the structural design of the battery module can be considerably simplified. It has also been shown that vacuum-sealing the battery module housing has an additional positive side effect.By generating a negative pressure of approximately 0.4 bar within the battery module housing, the battery cells housed therein automatically achieve the required compression pressure necessary for proper battery cell function. Previously, additional compression pads were used for this purpose, but these can now also be eliminated, allowing the battery module's design to be further simplified.

[0011] In a particularly advantageous embodiment, a coolant sump can be provided within the battery module housing, which forms a reservoir for non-evaporated coolant.

[0012] Preferably, the battery cells can be arranged within the battery module housing in such a way that they are partially immersed in the coolant sump.

[0013] The coolant may preferably be alcohol, in particular methanol, water or a dielectric oil.

[0014] A traction battery according to the invention is characterized in that the battery modules are designed according to one of claims 1 to 5.

[0015] Further features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the accompanying drawings. Fig. 1 is a schematically highly simplified vertical sectional view of a battery module of a traction battery of a vehicle according to a preferred embodiment of the present invention, illustrating the basic structure of the battery module, Fig. 2 shows a further schematically simplified view of the battery module according to Fig. 1, which shows its basic operation during cooling.

[0016] With reference to Fig. 1, a battery module 1 for a traction battery of a vehicle comprises a battery module housing 2, within which a battery cell arrangement 3 with a plurality of battery cells 3a-3g is housed. Furthermore, the battery module 1 has a cooling plate 4, which is arranged on an upper side of the battery module housing 2 and closes the battery module housing 2. During operation, it is necessary to cool the battery module 1 or the battery cells 3a-3g housed therein in a suitable manner.

[0017] The battery module 1 is cooled in the present case in the manner of a vapor chamber. For this purpose, the cooling plate 4 has a capillary structure 5 formed by a plurality of capillary channels 5a-5f within the cooling plate 4. During the manufacture of the battery module 1, the battery module housing 2 is first vacuumized so that a negative pressure is generated therein. Preferably, a negative pressure of approximately 0.4 bar is generated. Subsequently, a coolant 6 is introduced into the battery module housing 2, which can be, for example, alcohol, in particular methanol, water, or a dielectric oil.

[0018] With further reference to Fig. 2, the basic functional principle of cooling the battery module 1 or the battery cells 3a-3g arranged within the battery module housing 2 will be explained in more detail below. Within the battery module housing 2, a coolant sump 7 is provided, which forms a reservoir for the non-evaporated coolant 6. The coolant 6 evaporates due to the waste heat of the battery cells 3a-3g. Since a negative pressure of approximately 0.4 bar prevails within the battery module housing 2, the evaporation of the coolant 6 advantageously begins at a temperature of approximately 40°C. The evaporated coolant 6', which is in Fig.2, symbolized by corresponding arrows, expands, rises within the battery module housing 2, and is transported to colder areas of the battery module 1, in particular to the cooling plate 4. The evaporated coolant 6' then condenses on the cooling plate 4 and, due to the effect of capillary forces, is drawn into the capillary structure 5 of the cooling plate 4 as soon as the evaporated coolant 6' is liquid again. The resulting coolant condensate 6" then drips back onto the battery cells 3a-3g of the battery cell arrangement 3 or into the coolant sump 7.

[0019] An advantage of the solution described here is that the evaporation of the coolant 6 on the cell surfaces of the battery cells 3a-3g eliminates the need for a gap filler between the battery cells 3a-3g and the battery module housing 2, since heat is transported by evaporation and condensation and thus not primarily by heat conduction. By vacuuming the battery module housing 2 to the correct negative pressure, the coolant 6 can evaporate on the warm cell surfaces of the battery cells 3a-3g in a temperature range from approximately -40°C to approximately +60°C and condense on the cooling plate 4 of the battery module housing 2. In this way, a gap between the cell surfaces of the battery cells 3a-3g and the battery module housing 2 can be overcome, which was previously achieved using the gap filler.Since the battery module 1 presented here no longer requires a gap filler, the structural design of the battery module 1 can be considerably simplified.

[0020] To ensure stable cooling, it is advantageous that the cooling plate 4 is mounted on the top side of the battery module housing 2, since the warm cell heads of the battery cells 3a-3g can directly re-evaporate the coolant condensate 6" dripping from the cold cooling plate 4, which in turn has a direct positive effect on the cooling performance. The cell bases of the battery cells 3a-3g can advantageously also be immersed in the wet coolant sump 7 of the non-evaporated coolant 6.

[0021] It has been shown that vacuuming the battery module housing 2 has an additional positive side effect. By generating a negative pressure in the range of approximately 0.4 bar within the battery module housing 2, the battery cells 3a-3g automatically have the required compression pressure necessary for proper functioning of the battery cells 3a-3g. Previously, additional compression pads were used for this purpose, but these can now be omitted, allowing the structural design of the battery module 1 to be further simplified.

[0022] A traction battery of a motor vehicle can be manufactured from a number n ≥ 1 of the battery modules 1 presented here.

Claims

[1] Battery module (1) for a traction battery of a vehicle, comprising - a battery module housing (2), - a battery cell arrangement (3) comprising a plurality of battery cells (3a-3g) accommodated within the battery module housing (2), - a cooling plate (4) which is attached to an upper side of the battery module housing (2) and by means of which the battery module housing (2) is closed, and - an evaporable coolant (6) which is accommodated within the battery module housing (2), wherein the battery module housing (2) is vacuumized so that a negative pressure prevails within the battery module housing (2), characterized by that the cooling plate (4) has a capillary structure (5) which is formed by a plurality of capillary channels (5a-5f) within the cooling plate (4), wherein the cooling of the battery module (1) takes place in the manner of a vapor chamber. [2] Battery module (1) according to claim 1, characterized by that the battery module housing (2) is vacuumed in such a way that a negative pressure of approximately 0.4 bar prevails within the battery module housing (2). [3] Battery module (1) according to one of claims 1 or 2, characterized by that a coolant sump (7) is provided within the battery module housing (2), which forms a reservoir for non-evaporated coolant (6). [4] Battery module (1) according to claim 3, characterized by that the battery cells (3a-3g) are arranged within the battery module housing (2) in such a way that they are partially immersed in the coolant sump (7). [5] Battery module (1) according to one of claims 1 to 4, characterized by that the coolant (6) is alcohol, in particular methanol, water or a dielectric oil. [6] Traction battery of a vehicle, comprising a number n ≥ 1 of battery modules (1), characterized by that the battery modules (1) are designed according to one of claims 1 to 5.

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