Battery module for a motor vehicle

Abstract

The present invention relates to a battery module (10) for a motor vehicle (200). The invention further relates to a high-voltage battery (100) and a motor vehicle (200).

Description

[0001] The present invention relates to a battery module for a motor vehicle. The invention further relates to a high-voltage battery comprising several such battery modules and a motor vehicle.

[0002] It is generally known that hybrid or purely electric vehicles have at least one propulsion-generating electric motor which is supplied with electrical energy by an electrical storage device, in particular a high-voltage battery.

[0003] Such a high-voltage battery typically consists of several battery modules, each of which in turn consists of several battery packs, in particular a large number of individual battery cells.

[0004] The individual battery cells are typically electrically connected to each other via a cell contacting system. In particular, the cell connection elements of the cell contacting system are welded to the cell contacts of the battery cells using a melting process, such as laser welding.

[0005] A disadvantage here is that the cell contacts of the battery cells and cell connection elements of the cell contacting system consist of different electrically conductive materials, in particular different metals with different melting points.

[0006] In other words, the contacting of cell contacts and cell connecting elements known from the prior art is based on an intermetallic connection, i.e., a mixed connection of several different joining partners.

[0007] However, due to the physical properties of battery electrics, the joining partners aluminium-steel, aluminium-copper and copper-steel are very advantageous and therefore in high demand.

[0008] Due to the different material properties, welding such joining partners is very challenging, as a complete mixing of both materials leads to intermetallic phases, brittle zones and cracks in the joint.

[0009] In the case of an aluminum-steel alloy, for example, there is a significant difference in melting temperature (aluminum approx. 660 °C, steel approx. 1400 °C). Furthermore, the raw aluminum material has a thin layer of aluminum oxide with a melting temperature of over 2000 °C, which the laser radiation must first penetrate.

[0010] Depending on which joining partner is located above, different effects result.

[0011] In the case of steel as the joining partner above, the material is not yet completely melted, while the lower joining partner, i.e. the aluminum, is already melting.

[0012] Conversely, aluminum as the joining partner above may already be completely melted, while the joining partner below, i.e. the steel, is still completely solidified.

[0013] Furthermore, such joining partners can react very violently with each other. Even the smallest amounts of aluminum, at temperatures above 1000 °C, can come into contact with hot steel, similar to water droplets in hot oil, leading to explosive splashes.

[0014] In other words, a mixed joint of several different joining partners leads to intermetallic phases, brittle zones and cracks.

[0015] These brittle zones and cracks can in turn lead to a thermal event.

[0016] A thermal event is understood as an uncontrolled reaction that can occur particularly in lithium-ion battery cells. Damage to the battery cells or a short circuit leads, in particular, to a build-up of heat and pressure within the battery module or high-voltage battery. When this reaches a certain level, chemical reactions are triggered, generating even more heat and pressure and causing a rapidly propagating feedback loop, which in turn can lead to catastrophic explosions and fires.

[0017] It is therefore an object of the present invention to at least partially overcome the disadvantages described above in a battery module for a motor vehicle. In particular, it is an object of the present invention to create a safer battery module for a motor vehicle in which thermal events are avoided. It is also an object of the present invention to create a safe high-voltage battery and a safe motor vehicle.

[0018] The foregoing problem is solved by a battery module having the features of claim 1. With regard to the high-voltage battery, the problem is solved by the subject matter of dependent claim 8, and with regard to the motor vehicle by the subject matter of dependent claim 9. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the battery module naturally also apply in connection with the high-voltage battery according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always refers, or can refer, to each other.

[0019] According to the first aspect of the invention, the problem is solved by a battery module for a motor vehicle.

[0020] The battery module according to the invention comprises: - a plurality of battery cells, each battery cell having a first cell contact with a first polarity and a second cell contact with a second polarity, - wherein the first cell contact is made of a first electrically conductive material and the second cell contact is made of a second electrically conductive material, - a cell contacting system with a multitude of cell connection elements for serial and / or parallel electrical contacting and mechanical connection of the multitude of battery cells to each other, - wherein the multitude of cell connection elements are each formed from the second electrically conductive material, - wherein the first cell contact has a coating in certain areas which is formed from the second electrically conductive material.

[0021] The core idea of ​​the invention is therefore that the contacting of the cell contacts and cell connecting elements is not carried out, as in the prior art, by a mixed connection with different joining partners, in particular by an intermetallic connection, but by a homogeneous connection with the same joining partners, in particular by a connection of the same material.

[0022] Such a material-identical connection can consistently prevent intermetallic phases, brittle zones and crack formation.

[0023] This ensures both excellent electrically conductive contact and a mechanically very stable connection between the cell contacts of the battery cells and the cell connection elements of the cell contacting system, thus preventing thermal events.

[0024] According to a preferred embodiment of the invention, a battery module may be provided in such a way that the first electrically conductive material is a high-purity steel, in particular hilumin. Hilumin is produced from high-purity, specially cast steel and is specifically designed for battery applications. Hilumin is produced, in particular, by electrolytic nickel plating of a cold-rolled strip and diffusion annealing, and exhibits low contact resistance and high corrosion resistance. Hilumin is therefore suitable for various applications, especially for different battery types such as alkaline, lithium, NiMH, NiCd, Li-ion, or zinc-air battery cells.

[0025] For electrotechnical reasons, the joining partners aluminum-steel, aluminum-copper, and copper-steel are very advantageous and in high demand. Therefore, according to a preferred further development of the invention, a battery module can be provided with aluminum as the second electrically conductive material. Of course, the second electrically conductive material can also be copper or another metal with very good electrical and mechanical properties, such as tungsten, zinc, nickel, silver, or gold.

[0026] According to a preferred embodiment of the invention, a battery module may be provided in such a way that the coating of the first cell contact with the second electrically conductive material is produced by a cold gas spraying process. In the cold gas spraying process (CGS - Cold Gas Spray), a coating material in powder form is applied to the substrate material, here the second electrically conductive material, at very high speed. Aluminum can particularly preferably be applied as the coating material to high-purity steel, especially hilumin. It is conceivable that the coating of the first cell contact with the second electrically conductive material is produced by an alternative thermal spraying process.

[0027] According to a preferred embodiment of the invention, in a battery module, the cold gas spraying process can be carried out at an operating pressure of at least 10 bar, preferably at least 20 bar, of a cold gas spraying device. This ensures a sufficient impact velocity of the material particles for the coating.

[0028] According to a preferred embodiment of the invention, a battery module can be provided in such a way that the cold gas spraying process takes place at a temperature of at least 50 °C, preferably at least 100 °C, and particularly preferably at least 200 °C. This significantly reduces energy consumption and simultaneously ensures a durable coating of the second electrically conductive material on the first cell contact.

[0029] According to a preferred embodiment of the invention, a battery module can be provided with a coating having a layer thickness of at least 0.5 mm. This ensures that when the cell connection elements are joined to the respective cell contacts of the battery cells, the connection is made only with the coating material of the same type and that the first cell contact made of the first electrically conductive material, in particular the high-purity, specially cast steel, is not melted by the melting process. This prevents, in particular, the formation of intermetallic phases, brittle zones, and cracks.

[0030] According to a second aspect of the invention, a high-voltage battery for a motor vehicle, comprising several such battery modules, is proposed, wherein the battery modules are electrically connected in series and / or in parallel.

[0031] According to a third aspect of the invention, a motor vehicle with such a high-voltage battery is proposed.

[0032] The described high-voltage battery and the motor vehicle offer all the advantages that have already been described for a battery module according to the first aspect of the invention.

[0033] A battery module according to the invention is explained in more detail below with reference to the drawings. The drawings schematically show: Fig. 1 a perspective view of a battery module according to an embodiment of the present invention, Fig. 2 a top view of a battery module according to an embodiment of the present invention and Fig. 3 a motor vehicle with a high-voltage battery according to an embodiment of the present invention.

[0034] Fig. Figure 1 shows a perspective view of a battery module 10 according to the invention of a high-voltage battery 100.

[0035] As in the Fig. As can be clearly seen in Figure 1, the battery module 10 comprises a large number of battery cells 20 arranged side by side.

[0036] In the depicted Fig. 1, Fig. 2 to Fig. 3. The battery cells 20 are designed as cylindrical lithium-ion battery cells 20, in particular as round cells. It is conceivable that the battery cells 20 also have a different geometry and are designed, for example, as cuboid storage cells or so-called "pouch cells". It is conceivable that the battery cells 20 are designed, for example, as alkaline, lithium, NiMH, NiCd or zinc-air battery cells.

[0037] Battery cells 20 with different cell chemistries can also be used.

[0038] The battery module 10 according to the invention can in particular be used in a high-voltage battery 100 to provide, for example, an output or nominal voltage of at least 48 V, 100 V, 200 V, 400 V, 600 V, 800 V or more.

[0039] This allows the high-voltage battery 100 to be used as a traction battery for a motor vehicle 200.

[0040] It is conceivable that the high-voltage battery 100 can also be used in other ways, such as a home or building battery, a buffer or stabilization battery for an energy supply network, for supplying stationary facilities or systems and / or the like.

[0041] Each battery cell 20 has a first cell contact 30 with a first polarity and a second cell contact 40 with a second polarity.

[0042] The first cell contact 30 is formed by a cell jacket 31 of the battery cell 20, which encloses the entire outer surface of the cylindrical battery cell 20 and extends over the edge 32 from the outer surface of the cylindrical battery cell 20 to an upper end face 33 and a lower end face 34. The edge 32 thus defines a transition between the outer surface of the cylindrical battery cell 20 and the end faces 33, 34.

[0043] In other words, the cylindrical battery cell 20 is mostly enclosed by the first cell contact 30 or the cell shell 31 and thus also covers a radially outer ring of the two end faces 33, 34.

[0044] The second cell contact 40 is formed by a cell terminal 41, which protrudes concentrically from the upper front face 33.

[0045] A separator is arranged between the first cell contact 30 and the second cell contact 40.

[0046] In the depicted Fig. 1, Fig. 2 to Fig. In the first cell contact 30, a negative polarity is observed, and a positive polarity is observed. Therefore, the first cell contact 30 can be considered the anode and the second cell contact 40 the cathode.

[0047] However, it is conceivable that in another embodiment, conversely, the first cell contact 30 has a positive polarity and the second cell contact 40 has a negative polarity.

[0048] The first cell contact 30 is made of a first electrically conductive material 35, in particular Hilumin, a nickel-plated high-purity steel, and thus has a low contact resistance and high corrosion resistance.

[0049] The second cell contact 40 is made of a second electrically conductive material 45, in particular aluminum, and thus has very good electrical conductivity.

[0050] The battery module 10 according to the invention further comprises a cell contacting system 50 with a plurality of cell connecting elements 51, 52 for serial and / or parallel electrical contacting and mechanical connection of the plurality of battery cells 20 to each other.

[0051] The multitude of cell connection elements 51, 52 are each made of the second electrically conductive material 45, i.e., aluminium.

[0052] The voltages of a larger number or preferably all battery cells 20 can be accessed via the cell contacting system 50.

[0053] For this purpose, the battery cells 20 can not only be electrically interconnected via the cell contacting system 50, but can also be connected to a control or measuring electronics, a so-called measuring card, via conductor elements not shown in the cell contacting system 50.

[0054] Within the area of ​​such a measurement card, the charge states of the battery cells 20 can, for example, be indirectly recorded. Furthermore, a large number of discharge resistors can be arranged there in order to achieve the charge state of a single battery cell 20 by discharging the remaining individual battery cells 20 with an excessively high charge state.

[0055] In electrical engineering, this process is understood as the "balancing of the battery cells", which is why such resistors are also called "balancing resistors".

[0056] Temperature sensors can also be connected to the measuring card via further conductor elements not shown in the cell contacting system 50 in order to record temperature values ​​for the thermal management of the battery module 10 according to the invention.

[0057] Fig. Figure 2 shows a top view of a battery module 10 according to the invention of a high-voltage battery 100.

[0058] As in the Fig. As can be clearly seen, the first cell contact 30 has a coating 60.

[0059] The coating 60 can, in principle, be applied to any area of ​​the first cell contact 30. Advantageously, the coating 60 is provided as a circular ring in the area of ​​the upper end face 33 of the cell casing 31. This means that the individual battery cells 20 do not need to be aligned in a specific direction for series or parallel connection. The individual battery cells 20 can simply be arranged next to each other, preferably spaced apart.

[0060] The basic idea of ​​the invention is to carry out the contacting, in particular the welding of the cell contacts 30, 40, especially the contacting of the first cell contact 30, i.e. the cell shell 31, and the cell connecting elements 51, 52, not as in the prior art by a mixed connection with different joining partners, in particular by an intermetallic connection, but by a homogeneous connection with the same joining partners, in particular by a material-identical connection.

[0061] Therefore, the cell connecting elements 51, 52 are also made of the same second electrically conductive material 45, i.e., aluminum.

[0062] Such a material-identical bond effectively prevents intermetallic phases, brittle zones, and cracking, as there is no longer a significant difference in melting temperature. Due to the identical melting temperature, explosive reactions are also avoided.

[0063] At the same time, very good electrical contacting and a mechanically very stable connection between the cell contacts 30, 40 of the battery cells 20 and the cell connection elements 51, 52 of the cell contacting system 50 can still be ensured.

[0064] According to the invention, the coating 60 of the first cell contact 30 is formed with the second electrically conductive material 45, i.e. the aluminum, in the area of ​​the cell shoulder of the battery cell 20, i.e. the upper end face 33 of the cell shell 31.

[0065] The coating 60 is produced in particular by a cold gas spraying process. This type of cold gas spraying process allows for the simple production of a very thin yet very dense coating 60.

[0066] Such a cold gas spraying process is understood to be a special coating process in which the coating material of the coating 60, i.e. the aluminium, is applied in powder form at very high speed to the upper end face 33 of the cell shell 31.

[0067] In such a cold gas spraying process, a process gas heated to a few hundred degrees, preferably nitrogen or helium, is accelerated to supersonic speed by expansion in a Laval nozzle, and the powder particles of the coating 60 are then injected into the gas jet.

[0068] The injected spray particles are accelerated to such a high speed that, unlike other thermal spraying processes, they form a very dense and firmly adhering coating 60 upon impact with the upper end face 33 of the cell shell 31, even without prior melting or pre-melting.

[0069] This type of cold gas spraying process avoids an additional sintering process, which is more energy-intensive and involves higher manufacturing costs compared to the cold gas spraying process.

[0070] Furthermore, such a cold gas spraying process allows very thin layers with a layer thickness of only a few micrometers to be produced reliably, which significantly reduces the size of the battery cells 20 and thus the weight of the battery module 10 or the high-voltage battery 100.

[0071] Furthermore, such a cold gas spraying process makes it possible to produce very inexpensive battery cells 20, in particular battery cells costing €0.15.

[0072] Advantageously, such a cold gas spraying process is carried out at an operating pressure of at least 10 bar, particularly preferably at least 20 bar, of a cold gas spraying device. This ensures a sufficient impact velocity of the material particles for the coating 60.

[0073] Advantageously, such a cold gas spraying process is carried out at a temperature of at least 50 °C, preferably at least 100 °C, and particularly preferably at least 200 °C. This allows the energy requirement to be significantly reduced and simultaneously ensures a durable coating 60 of the second electrically conductive material on the upper end face 33 of the cell shell 31.

[0074] Advantageously, the coating 60 has a layer thickness of at least 0.5 mm. This allows the welding process to penetrate even deeper into the coating 60 to ensure a more stable connection without affecting the underlying first electrically conductive material 35, i.e., the hilumin.

[0075] Furthermore, such a layer thickness can equalize the topographical difference between the second cell contact 40, i.e., the cell terminal, and the upper end face 33 of the cell casing 31. If, for example, all upper end faces 33 of the battery cells 20 and all cell terminals are at the same height, the cell contacting system 50 can be designed two-dimensionally in the form of a flat foil mesh. Such a design of the cell contacting system 50 could also represent enormous cost-saving potential.

[0076] As in the Fig. As can be clearly seen, the cell connection elements 51, 52 are connected to the cell contacts 30, 40 of the battery cells 20, in particular welded together with the same material.

[0077] In this process, five battery cells 20 are connected in parallel to form a battery pack by means of the cell connection elements 51, which in turn are connected in series to form a battery module 10 by means of the cell connection elements 52.

[0078] Naturally, the parallel-connected battery pack or the battery module 10 according to the invention can be formed by a number of more or fewer battery cells 20. For example, it is conceivable that eight battery cells 20 are connected in parallel to form a battery pack, which in turn are connected in series to form a battery module 10 by means of the cell connection elements 52.

[0079] It is also conceivable that the respective battery cells 20 are first connected in series to form a battery pack and then subsequently connected in parallel to form a battery module 10.

[0080] In other words, the battery cells 20 are electrically contacted and simultaneously mechanically connected to each other in series and / or parallel by the multitude of cell connection elements 51, 52 of the cell contacting system 50 to form a battery module 10 according to the invention.

[0081] In the depicted Fig. 1, Fig. 2 to Fig. 3 The first cell contact 30 has a negative polarity and the second cell contact 40 has a positive polarity. Thus, the first cell contact 30 can be understood as the anode and the second cell contact 40 as the cathode, so that during operation of the battery module 10 according to the invention, i.e., during a discharge process of the battery cells 20, electrons flow in an external circuit through the cell connection elements 51, 52 from the anode to the cathode.

[0082] Fig. Figure 3 shows a motor vehicle 200 with a high-voltage battery 100 according to an embodiment of the present invention.

[0083] The high-voltage battery 100 comprises several battery modules 10 according to the invention, wherein the battery modules 10 are electrically connected in series and / or parallel.

[0084] The high-voltage battery 100 is characterized, among other things, by its high energy density, thermal stability and extremely low self-discharge.

[0085] The high-voltage battery 100 can, for example, provide an output or nominal voltage of at least 48 V, 100 V, 200 V, 400 V, 600 V, 800 V or more, so that the high-voltage battery 100 can be used in particular as a traction battery for the motor vehicle 200.

[0086] The motor vehicle 200 can be a pure electric vehicle (EV), a hybrid vehicle (HEV) or a plug-in hybrid vehicle (PHEV). Reference symbol list 10 battery modules 20 battery cells 30 first cell contact 31 Cell mantle 32 edge 33 upper forehead 34 lower forehead 35 first electrically conductive material 40 second cell contact 45 second electrically conductive material 50 cell contacting system 51 Cell connection element 52 cell connection element 60 coating 100 high-voltage battery 200 motor vehicles

Claims

[1] Battery module (10) for a motor vehicle (200), comprising the battery module (10): - a plurality of battery cells (20), each battery cell (20) having a first cell contact (30) with a first polarity and a second cell contact (40) with a second polarity, - wherein the first cell contact (30) is formed from a first electrically conductive material (35) and the second cell contact (40) is formed from a second electrically conductive material (45), - a cell contacting system (50) with a plurality of cell connecting elements (51, 52) for serial and / or parallel electrical contacting and mechanical connection of the plurality of battery cells (20) to each other, - wherein the plurality of cell connection elements (51, 52) are each formed from the second electrically conductive material (45), - wherein the first cell contact (30) has a coating (60) in some areas, which is formed from the second electrically conductive material (45). [2] Battery module (10) according to claim 1, characterized by , that the first electrically conductive material (35) is a high-purity steel, in particular a hilumin. [3] Battery module (10) according to at least one of the preceding claims, characterized by , that the second electrically conductive material (45) is aluminium. [4] Battery module (10) according to at least one of the preceding claims, characterized by , that the coating (60) of the first cell contact (30) with the second electrically conductive material (45) is produced by a cold gas spraying process. [5] Battery module (10) according to claim 4, characterized by that the cold gas spraying process takes place at an operating pressure of a cold gas spraying device of at least 10 bar, preferably at least 20 bar. [6] Battery module (10) according to claim 4 or 5, characterized by that the cold gas spraying process takes place at a temperature of at least 50 °C, preferably at least 100 °C, particularly preferably at least 200 °C. [7] Battery module (10) according to at least one of the preceding claims, characterized by that the coating (60) has a layer thickness of at least 0.5 mm. [8] High-voltage battery (100) for a motor vehicle (200), comprising several battery modules (10) according to at least one of the preceding claims, wherein the battery modules (10) are electrically connected in series and / or in parallel. [9] Motor vehicle (200) with a high-voltage battery (100) according to the preceding claim.

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