Heat-exchange plate for battery pack with structural plate

Abstract

The invention relates to a heat-exchange plate (10) for thermal management of a battery pack (200), comprising first (20) and second (30) plates, at least the first (20) plate comprising at least one channel (40), the first (20) and second (30) plates being contiguous so that the channel (40) partially delimits at least one duct of a circuit for circulating a heat-transfer fluid, characterised in that the first plate (20) is made of a first material, and the second plate (30) is made of a second material which is different from the first material and gives the second plate (30) a structural function.

Description

[0001] Description

[0002] Title of the invention:

[0003] HEAT EXCHANGE PLATE FOR STRUCTURAL PLATE BATTERY PACKS

[0004] The present invention relates to battery thermal regulation and more particularly to heat exchange plates for the thermal management of battery packs, particularly in the automotive field.

[0005] Thermal regulation of batteries and battery packs, particularly in the automotive sector and even more so in electric and hybrid vehicles, is an important point because if the batteries are subjected to temperatures that are too cold, their autonomy can decrease significantly and if they are subjected to temperatures that are too high, there is a risk of thermal runaway which can lead to the destruction of the battery.

[0006] In order to regulate the temperature of the batteries, it is known to add a temperature regulation device to the battery module. These devices generally use heat transfer fluids circulating, for example by means of a pump, in a conduit circuit, said conduit circuit passing in particular under or inside a heat exchange plate in direct contact with the batteries.

[0007] Heat transfer fluids can thus absorb heat emitted by the battery(ies) in order to cool them and evacuate this heat at one or more heat exchangers such as a radiator or a refrigerant. Heat transfer fluids can also, if necessary, provide heat to warm said batteries, for example if they are connected to an electrical resistance or to a Positive Temperature Coefficient (PTC) heater.

[0008] The heat transfer fluids generally used are ambient air or liquids such as water. Since liquids are better conductors of heat than gases, this solution is preferred because it is more efficient.

[0009] Generally, the heat exchange plates in direct contact with the cells are placed under the batteries, said batteries thus resting on said heat exchange plates. The heat exchange plates are generally made of metal and are composed of two metal plates stamped and brazed against each other so as to form one or more circuits of conduits for circulation of the heat transfer fluid between a fluid inlet and an outlet.

[0010] In order to provide mechanical strength for the battery packs, the latter, equipped with the battery cooler, must be connected to a structural element and must be protected from external elements. This so-called "structural" function is currently provided by a set of beams, crosspieces and protections (structural panel positioned under the heat exchange plates). Such a structural assembly provides resistance to crash tests, impacts, but also to the loading of the battery modules on the battery cooler. The elements constituting the structural function are manufactured in a known manner with materials offering very high mechanical properties, such as the elastic limit (Rp0.2) and the breaking limit (Rm).

[0011] However, the manufacture of a structural panel, and the elements necessary for fixing the battery pack to the beams, represent an additional cost for the car manufacturer, and its use makes the vehicle heavier, and consequently increases CO2 emissions.

[0012] One of the aims of the invention is to propose a heat exchange plate which at least partially overcomes the drawbacks of the prior art and to propose a structural heat exchange plate, while respecting the objectives of recyclability and the search for carbon neutrality.

[0013] The present invention therefore relates to a heat exchange plate for thermal management of battery packs, comprising first and second plates, at least the first plate comprising at least one channel (the first plate comprises a relief forming at least one channel when associated with the second plate), the first and second plates being joined together so that said channel partially delimits at least one conduit of a circuit for circulating a heat transfer fluid, and in which the first plate is made of a first material, the second plate is made of a second material different from the first material and giving the second plate a structural function.

[0014] Such a structural heat exchange plate makes it possible to reduce the number of crosspieces and elements (casing, attachment points, reinforcement, beams, etc.) necessary for the assembly of the battery modules and the mechanical resistance of the battery packs.

[0015] Thus, the structural heat exchange plate according to the invention allows for cost savings, weight savings and a reduction in CO2 emissions for car manufacturers.

[0016] According to other optional characteristics of the thermal plate taken alone or in combination: the first material has a lower elastic limit than the second material, making it possible to prevent the brazing step from causing deformations of the thermal plate, and therefore, making it possible to respect the intended dimensions of the thermal plate. the second material has an elastic limit (Rp0.2) greater than 190 MPa, preferably greater than 200 MPa. the second material has a breaking limit (Rm) greater than 220 MPa, preferably greater than 240 MPa. the second material has an elongation (A%) at break greater than 22%. the first and second materials are metallic materials. the first and second materials are aluminum alloys allowing assembly of the first plate and the second plate by a Nocolok® brazing process.the second material comprises predominantly an aluminum alloy of the 6000 series, preferably at least 95%. the first material comprises predominantly an aluminum alloy of the 3000 series, preferably at least 95%. at least one of the faces of at least one of the plates comprises an anti-corrosion layer. the anti-corrosion layer is made of an aluminum alloy of the 1000, 3000+Zn, or 7000 series.

[0017] When the anti-corrosion layer is made of aluminum alloy of the 3000+Zn series, the Zn concentration is between 0.5% and 1.8%. At least one of the faces of the second plate has a magnesium barrier layer. The barrier layer is made of aluminum alloy of the 1000, 3000+Zn series, or

[0018] 7000. at least one of the faces of the second plate comprises a magnesium barrier layer, preferably made of aluminum alloy of the 1000, 3000+Zn, or 7000 series.

[0019] When the barrier layer is made of aluminum alloy of the 3000+Zn series, the Zn concentration is between 0.5% and 1.8%. at least one of the internal faces of at least one of the plates comprises a brazing layer. the brazing layer is made of aluminum alloy of the 4000 series, preferably 4343 or 4045 the second plate (30) has on each of its faces a layer made of aluminum alloy of the 7000 series, preferably 7072 or 3000+Zn, for example 3003+Zn.

[0020] When each of the faces of the second plate (30) has a layer made of aluminum alloy of the 3000+Zn series, the Zn concentration is between 0.5% and 1.8%.

[0021] The invention also relates to a method for manufacturing a heat exchange plate as described above, comprising the following steps: i- production of the first plate using the first material, and production of the second plate using the second material; ii- formation of at least one channel on at least one of the first and second plates, preferably by stamping; iii- sealed assembly of the two plates; and iv- application of at least one artificial aging treatment of the assembled assembly, in order to improve the structural performance, for example by means of a heat treatment.

[0022] According to other optional characteristics of the process taken alone or in combination: step ii) is carried out by means of a stamping process. step iii) is carried out by means of a brazing process, preferably Nocolok® brazing. step iv) comprises a heat treatment of the thermal plate. the heat treatment comprises a step of heating the thermal plate to 225°C for 45 min. a second material is used, mainly comprising an aluminum alloy of the 6000 series. step i) comprises a step of covering at least one of the faces of at least one of the plates with at least one functional layer, of the anti-corrosion, magnesium barrier, and / or brazing type.

[0023] Brief description of the figures

[0024] Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawings among which:

[0025] “[Fig. 1] shows a schematic perspective representation of a heat exchange plate according to the invention,

[0026] “ [Fig. 2] is a detail of Figure 1 illustrating part of a channel of the heat exchange plate,

[0027] “[Fig. 3] shows a schematic representation in exploded perspective of a heat exchange plate according to one embodiment,

[0028] “ [Fig. 4] is a set of figures (4A to 4C) illustrating examples of superposition of layers (anti-corrosion, brazing) around the core of the first plate,

[0029] “ [Fig. 5] is a set of figures (5A to 5C) illustrating examples of superposition of layers (anti-corrosion, barrier) around the core of the second plate,

[0030] “ [Fig. 6] is a diagram illustrating the different stages of an example of a method for manufacturing a thermal plate according to the invention.

[0031] Identical elements in different figures have the same references.

[0032] Detailed Description As illustrated in Figures 1 and 2, the heat exchange plate 10 for the thermal management of battery pack 200, comprises a first plate 20 (“Chanel plate”) and a second plate 30 (“base plate”).

[0033] At least one of the first 20 and second 30 plates comprises channels 40. In the example of FIG. 1, this is the first plate 20, which is then intended to come into contact with the battery pack 200.

[0034] According to an exemplary embodiment, the plates 20 and 30 of the thermal plate 10 have a substantially rectangular shape, with a length of 1700 mm and a width of 1300 mm. Each plate has a thickness of between 0.5 mm and 2 mm.

[0035] The first 20 and second 30 plates are joined together so that the channels 40 delimit a conduit of a circuit for circulating a heat transfer fluid. Preferably, the conduit is U-shaped and extends between a heat transfer fluid inlet and outlet formed respectively by connection pipes.

[0036] The heat exchange plate 10 may also comprise holding elements (not shown) allowing the said exchange plate to be fixed to the battery pack or to the battery. The heat exchange plate 10 may further comprise a seal 50 placed between the first 20 and the second 30 plates in order to ensure sealing between the latter.

[0037] By battery pack 200 we mean a set of cells electrically connected to each other and forming said battery pack 200, or a single large battery.

[0038] According to the invention, the first plate 20 is made of a first material, and the second plate 30 is made of a second material different from the first material and giving the second plate 30 a structural function.

[0039] To achieve this structural function, a second material is used having an elastic limit (Rp0.2) greater than 190 MPa, preferably greater than 200 MPa.

[0040] This elastic limit (Rp0.2) is measured according to the standard ISO:6892-1 process.

[0041] Preferably, the second material also has a breaking strength (Rm) greater than 220 MPa, preferably greater than 240 MPa.

[0042] This breaking limit (Rm) is measured according to the standard ISO:6892-1 process.

[0043] Preferably, the second material also has an elongation (A%) at break greater than 22%.

[0044] This elongation at break (Rm) is measured according to the standard ISO:6892-1 method.

[0045] Regarding the first material, it is chosen from materials having a lower elastic limit than the second material. The value of the elastic limit is chosen so as to release at least part of the stresses caused by the second plate 30 with structural function.

[0046] Preferably, materials are used that are compatible with the current plate forming process, stamping, and with the current heat exchange plate manufacturing process: brazing. Thus, the first and second materials are chosen from metals. Preferably, the first and second materials are chosen to allow assembly of the two plates 20 and 30 by a Nocolok® brazing process.

[0047] According to a preferred embodiment, the second material comprises mainly, preferably at least 95% (for recycling reasons in particular), an aluminum alloy of the 6000 series, the alloying elements of which are magnesium and silicon. Indeed, this alloy offers mechanical properties superior to an aluminum alloy of the 3000 series, conventionally used to manufacture the two plates of a heat exchange plate.

[0048] Due to its high mechanical properties, and in particular its rigidity, type 6000 aluminum gives the thermal plate 1 a structural function. However, since the 6000 series aluminum alloy does not deform during mechanical strength tests, the use of this material for the second plate 30 may, depending on the design of the thermal plate 1, result in a significant increase in local forces, and thus cause non-conformities, or even ruptures, in mechanical strength tests (pressure cycle, vibration, burst strength, etc.). Indeed, it is known, particularly during fatigue tests, that a “harder” material with a low elongation level (A%) at break sees its stress values ​​increase locally, because it deforms less easily and allows less “pulmonary” movement of the part, and is therefore less resistant to fatigue tests.

[0049] Therefore, according to this preferred embodiment, the first material of the first plate 20 is a 3000 series aluminum alloy, making it possible to release at least part of the stresses caused by the second plate 30 with a structural function.

[0050] In some embodiments, additional layers are applied to the plates 20 and 30. These embodiments are illustrated in Figures 4 and 5, and described below.

[0051] Anti-corrosion layers 80 According to one embodiment, illustrated in Figures 4 and 5, each plate 20, 30 is covered on at least one of the two faces, preferably on both faces, by an anti-corrosion layer 80, making it possible to protect the core of the plate 60, 70, made of first and second material.

[0052] Figure 4A illustrates the superposition of the layers forming the first plate 20, when the core 60 made of the first material is covered with a single anti-corrosion layer 80.

[0053] Figure 4B illustrates the superposition of the layers forming the first plate 20, when the core 60 made of the first material is covered with an anti-corrosion layer 80 on both of its faces.

[0054] Figure 5A illustrates the superposition of the layers forming the second plate 30, when the core 70 made of second material is covered with a single anti-corrosion layer 80.

[0055] Figure 5B illustrates the superposition of the layers forming the second plate 30, when the core 70 made of second material is covered with an anti-corrosion layer 80 on its two faces.

[0056] According to an exemplary embodiment, the anti-corrosion layer 80 is made of aluminum alloy of the 1000, 3000+Zn, or 7000 series. This layer behaves as a sacrificial layer to combat internal and / or external corrosion. The advantage of the 3000+Zn series layer is to retain the mechanical properties provided by the core alloy.

[0057] The thickness of the anti-corrosion layer 80 is between 2.5% and 10% of the plate thickness.

[0058] Layer 90 forming magnesium diffusion barrier (second plate)

[0059] When the second material is rich in magnesium, it is important, in order to maintain the structural properties of this material, that the magnesium remains in the core 70 in the second material. However, during the brazing step, necessary for the assembly of the two plates 20 and 30, the magnesium tends to escape and migrate out of the core 70 in the second material.

[0060] Thus, according to one embodiment, illustrated in Figure 5C, the second plate 30 is covered on at least one of its two faces, preferably on both faces, by a barrier layer 90, acting as a diffusion barrier to the magnesium during the brazing process. The magnesium thus remains in the core of the second layer, made of a second material, and thus preserves its structural properties.

[0061] According to an exemplary embodiment, the barrier layer 90 is made, like the anti-corrosion layer 80, from an aluminum alloy of the 1000, 3000+Zn, or 7000 series. The thickness of the barrier layer 90 is between 2.5% and 10% of the plate thickness.

[0062] Solder layers 100 (first plate)

[0063] According to one embodiment, illustrated in FIG. 4C, at least one of the first and second plates 20, 30 is covered on one of its faces, the face positioned opposite the other plate, by a brazing layer 100, making it possible to optimize the brazing process.

[0064] According to an exemplary embodiment, the brazing layer 100 is made of aluminum alloy of the 4000 series, preferably 4343 or 4045.

[0065] The thickness of the brazing layer 100 is between 2.5% and 10% of the plate thickness.

[0066] Figure 4C illustrates the superposition of the layers forming the first plate 20, when the core 60 made of the first material is covered with an anti-corrosion layer 80 on its two faces, and with a brazing layer 100.

[0067] Examples of achievements

[0068] Example 1

[0069] The anti-corrosion layer 80 is a 7000 series aluminum alloy, preferably

[0070] The anti-corrosion layer 80 is applied to the external face of the first plate 20 (not facing the plate 30), and to the external face of the second plate 30 (not facing the plate 20).

[0071] The inner face of the plate 20 is covered with a brazing layer of 4000 series aluminum alloy, preferably 4343 or 4045.

[0072] The core of the first plate is made of 3000 series aluminum alloy.

[0073] The core of the second plate is made of 6000 series aluminum alloy.

[0074] Example 2

[0075] The first plate 20 is consistent with that of example 1, but the second plate 30 is covered on both sides by a layer which is both a barrier and an anti-corrosion layer made from an aluminum alloy of the 1000, 3000+Zn, or 7000 series.

[0076] Example 3

[0077] The second plate 30 comprises a core of 6060 aluminum alloy covered with barrier layers of 1050 aluminum alloy. Example 4

[0078] In some embodiments, the second plate 30 comprises a core of 6000 series aluminum alloy covered with a layer of 7072 aluminum alloy acting as a barrier and anti-corrosion layer.

[0079] Advantageously, the 7072 aluminum alloy layer acts as a barrier layer, in order to prevent the migration of magnesium during the brazing process.

[0080] Advantageously, 7072 aluminum alloy layer acts as a sacrificial layer to meet corrosion requirements.

[0081] Finally, advantageously the combination of a 6000 series aluminum alloy and a 7072 aluminum alloy is preferred because, among other things, it is favorable in terms of recyclability.

[0082] The use of a layer of 3000 + Zn can promote anti-corrosion protection and the maintenance of mechanical properties, particularly for reduced thicknesses.

[0083] Manufacturing process

[0084] The invention also relates to a method for manufacturing a heat exchange plate 1 for thermal management of a battery pack 200 according to the invention. As illustrated in FIG. 6, the method comprises the following steps: i- production of the first 20 plate using the first material, and production of the second 30 plate using the second material; ii- formation of at least one channel 30 on at least one of the first 20 and second 30 plates, for example by means of a stamping method; iii- sealed assembly of the two plates, for example by means of a brazing method, preferably Nocolok® brazing; iv- application of at least one artificial aging treatment of the assembled assembly, in order to improve the structural performance, for example by means of a heat treatment.

[0085] According to one example, the heat treatment (step iv) consists of heating the thermal plate 1 to 225°C for 45 minutes.

[0086] According to a preferred embodiment, a second material is used comprising mainly an aluminum alloy of the 6000 series, preferably at least 95%. Indeed, such an alloy is hardenable by aging, and therefore hardenable by the brazing process (step iv) used to assemble the two plates 20 and 30. The brazing acts as a solution heat treatment. In addition, the mechanical strength of the second plate 30 is improved, increased thanks to the artificial aging treatment (step v). Advantageously, the method comprises, in step i), a covering of the plates 20 and / or 30 with functional layers:

[0087] - covering with an anti-corrosion layer 80, at least one of the faces of at least one of the plates 20 and 30; and / or - covering with a magnesium barrier layer 90, at least one of the faces of the second plate 30; and / or

[0088] - covering with a layer of brazing 100, the internal face (face facing the other plate) of at least one of the plates 20 and 30.

[0089] With such a treatment applied to the thermal plate 1 of example 3 (the second plate 30 comprises a core 70 in 6060 aluminum alloy covered with barrier layers in 1050 aluminum alloy), the following mechanical properties are obtained for a plate 30 having a thickness of 2 mm:

[0090] - RpO,2: 196 MPa

[0091] - Rm: 227 MPa - A50%: 9.8

[0092] List of references

[0093] 10 heat exchange plate for thermal management of a battery pack

[0094] 20 first plate (“Chanel plate”) of the heat exchange plate 10 30 second plate (“base plate”) of the heat exchange plate 10

[0095] 40: heat exchange plate channel 10

[0096] 50: heat exchange plate gasket 10

[0097] 60 core in first material of the first plate 20

[0098] 70 core in second material of the second plate 30 80: anti-corrosion layer

[0099] 90: magnesium diffusion barrier layer

[0100] 100: brazing layer

[0101] 200: battery pack

Claims

Claims: A heat exchange plate (10) for thermal management of a battery pack (200), comprising first (20) and second (30) plates, at least the first (20) plate comprising at least one channel (40), the first (20) and second (30) plates being joined such that said channel (40) partially delimits at least one conduit of a heat transfer fluid circulation circuit, characterized in that said first plate (20) is made of a first material, and said second plate (30) is made of a second material different from the first material and conferring a structural function on said second plate (30). A heat exchange plate (10) according to the preceding claim, wherein the first material has a lower elastic limit than the second material.Heat exchange plate (10) according to any one of the preceding claims, wherein said second material has a yield strength (Rp0.2) greater than 190 MPa, preferably greater than 200 MPa. Heat exchange plate (10) according to any one of the preceding claims, wherein said second material has a tensile strength (Rm) greater than 220 MPa, preferably greater than 240 MPa. Heat exchange plate (10) according to any one of the preceding claims, wherein said second material has an elongation (A%) at break greater than 22%. Heat exchange plate (10) according to any one of the preceding claims, wherein the first and second materials are aluminum alloys allowing the first plate (20) and the second plate (30) to be joined by a Nocolok® brazing process.Heat exchange plate (10) according to any one of the preceding claims, wherein said second material comprises predominantly an aluminum alloy of the 6000 series, preferably at least 95%. . Heat exchange plate (10) according to any one of the preceding claims, wherein said first material comprises predominantly an aluminum alloy of the 3000 series, preferably at least 95%. . Heat exchange plate (10) according to any one of the preceding claims, wherein at least one face of at least one of the plates (20, 30) comprises an anti-corrosion layer (80), preferably made of aluminum alloy of the 1000, 3000+Zn, or 7000 series.

0. Heat exchange plate (10) according to any one of the preceding claims, wherein at least one face of the second plate (30) comprises a magnesium barrier layer (90), preferably made of aluminum alloy of the 1000, 3000, or 7000 series. 1.

1. Heat exchange plate (10) according to any one of the preceding claims, wherein at least one of the inner faces of at least one of the plates (20, 30) has a brazing layer (100) preferably made of aluminum alloy of the 4000 series, more preferably 4343 or 4045.

2. Heat exchange plate (10) according to any one of the preceding claims, wherein the second plate (30) has on each of its faces a layer made of aluminum alloy of the 7000 series, preferably 7072 or an alloy of the 3000+Zn series. 3.A method for manufacturing a heat exchange plate (10) according to any one of the preceding claims, comprising the following steps: i- making the first (20) plate using the first material, and making the second (30) plate using the second material, the second material preferably comprising predominantly an aluminum alloy of the 6000 series; ii- forming at least one channel (30) on at least one of the first (20) and second (30) plates, preferably by stamping; iii- sealing assembly of the two plates, preferably by brazing, even more preferably by Nocolok® brazing; and iv- applying at least one artificial aging treatment to the assembled assembly, in order to improve structural performance, for example by means of a heat treatment. Method according to the preceding claim, wherein step i) comprises a step of coating at least one of the faces of at least one of the plates (20, 30) with at least one functional layer, of the anti-corrosion type (80), magnesium barrier (90), and / or brazing type (100).

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