Battery cell for a traction battery arrangement of a motor vehicle

Abstract

A battery cell for a traction battery arrangement of a motor vehicle is described, comprising a dimensionally stable housing in which at least one electrochemical element for storing and releasing electrical energy is arranged, wherein the at least one electrochemical element can be electrically contacted by means of a first pole that can be electrically contacted from outside the housing and by means of at least one second pole that can be electrically contacted from outside the housing, wherein the first pole is designed as a first conductor that is led out of the housing in a sealed manner and the at least one second pole is designed as a second conductor that is led out of the housing in a sealed manner, wherein the seal of the first conductor and the second conductor is each produced by an over-molded plastic.

Description

A battery cell for a traction battery arrangement of a motor vehicle is described.Battery cells for a traction battery arrangement of a motor vehicle of the type mentioned at the beginning are known in the prior art.In principle, different designs of battery cells for use in traction batteries of motor vehicles are known. Known shapes are, for example, prismatic cells and pouch cells.Depending on the application, one or more cell stacks or pancakes of active layers are introduced as electrochemical element in corresponding battery cells. The active layers are stacked in a plurality of, usually rectangular, plies of negative and positive electrodes and conductor foils with corresponding plies of separators as in a sandwich.A prismatic cell, which is also called a hardcase cell, is similar in its internal structure to a pouch cell, but the outer housing is a fixed housing (hardcase). Such a housing of a prismatic cell is usually multi-part and has a cover. Electrical contacting takes place at terminals which are generally embedded in the cover.In known hardcase battery cells, a complex construction is necessary for the passage of the electrical contacts outwards according to the prior art in order to be able to ensure tightness and electrical insulation even at higher internal pressures. As a result, much installation space and, as a result, charge density and charge capacity are lost. Many components and joints are also necessary for the terminals. In the case of round cells, the loss of installation space is somewhat less than in the case of cuboids, but contact must be made therefor on a very narrow edge of the cell, which is demanding with regard to the joining parameters and positioning of the contacts.A pouch cell is a design of a battery or of an accumulator in which electrochemically active layers are enclosed by a flexible outer foil, which usually consists of aluminum.Pouch cells are simpler in construction than prismatic cells. The electrical contacts are each guided directly to the outside through the sheathing in the form of a narrow strip / film piece and can optionally equally serve as cell connectors. There is only one component and only one joint, which is sealed by a sealing tape. However, pouch cells have other disadvantages, for example, relating to assembly, cell thickness growth, and handling.DE 10 2017 200 390 A1 describes an electrochemical cell comprising: a housing for receiving an electrochemical element, wherein the housing surrounds an interior space and comprises at least two housing components, wherein one of the at least two housing components is formed as a cover element; at least one connecting conductor for electrically connecting the electrochemical element to a cell terminal and / or an electrical contact element adjoining the cell terminal, wherein the connecting conductor is formed by connecting at least two connecting conductor components, wherein the at least two connecting conductor components are connected to one another in a connecting region of the connecting conductor; a fastening element for fixing the connecting conductor to the cover element, wherein the fastening element is an injection-molded element or a casting element and wherein the connecting region of the connecting conductor is surrounded by the fastening element.The disadvantage of the known prismatic cells is that the electrical contacting from the outside is very complicated in terms of design and therefore cost-intensive and installation space-intensive.The object is therefore to further develop battery cells for a traction battery arrangement of a motor vehicle of the type mentioned at the beginning in such a way that prismatic cells can be provided more favorably and with a higher storage density.The object is achieved by a battery cell for a traction battery arrangement of a motor vehicle according to claim 1.Described is a battery cell for a traction battery arrangement of a motor vehicle, having a dimensionally stable housing in which at least one electrochemical element for storing and delivering electrical energy is arranged, wherein the at least one electrochemical element can be contacted in a current-conducting manner by means of a first pole which can be electrically contacted from outside the housing and by means of at least one second pole which can be electrically contacted from outside the housing, wherein the first pole is designed as a first arrester which is guided in a sealed manner from the housing and the at least one second pole is designed as a second arrester which is guided in a sealed manner from the housing, wherein the seal of the first arrester and the second arrester is in each case produced by an injection-molded plastic.The battery cell corresponds to the basic type of prismatic cell. The dimensionally stable housing can have various geometric shapes, including cylindrical or cuboidal. The housing consists of two or more housing parts, one of which represents a housing cover. The other housing part can be formed by a housing trough. During assembly, the electrochemical element is introduced into the housing trough and the housing is hermetically sealed by means of the cover. Known methods can be used for this purpose. The housing can consist of various materials, in particular metals, for example steel.The structure of the electrochemical element depends on the battery principle used. For traction batteries of automobiles, rechargeable battery types are used. Known electrochemical principles include lithium ion batteries, lithium polymer batteries, lithium ferrous sulfate batteries, and the like. The electrochemical element includes a plurality of active layers sandwiched in a plurality of rectangular sheets of negative and positive electrodes and drain foils with respective sheets of separators. As a rule, the electrochemical element consists of one or more such cell stacks, which are either installed in the housing as a flat packet or wound (flat winding), depending on the housing geometry used.The arresters can be guided either through the housing cover, through other housing parts, or partly through the housing cover and partly through other housing parts.In the variant described first, the electrochemical element can be connected to the housing cover before being introduced into the housing trough, in that the arresters are guided through corresponding openings in the housing cover and are fixed to the housing cover by means of injection-molded plastic. The unit consisting of the housing cover and electrochemical element can then be inserted into the housing trough and the cover can be fastened to produce a hermetic seal.In variants in which the arresters are each led out of different surfaces, other mounting methods are necessary. When the arresters are passed through other housing parts, for example a housing trough, the electrochemical element can first be inserted through the housing trough, the arresters are injection-molded with plastic and the housing cover is then placed on, wherein the two steps can also be carried out in the opposite direction.In many applications, it is recommended to attach the arresters to a common surface in order to be able to carry out the contacting within the traction battery from one side. In particular in the case of accidents, arrangements with arresters provided on opposite sides can, however, also be used.The arresters represent the electrical connection from the electrochemical element to the outside. Usually, two different metal foils are located in a cell, which are responsible for the dissipation of the current. The essential property of the arrester is to conduct away electrons and to remain electrochemically stable in the process.By means of the seal produced by the injection molding process between the arresters and the housing, it is possible to achieve an electrically insulated and mechanically stable lead-through of the arresters outwards which resists the internal pressure which forms during operation of a few bar and also a pressure increase in the event of damage of a plurality of bar without gases or electrolyte emerging from the housing and all connection points. If an overpressure protection device, for example in the form of one or more test disks or one or more rupture membranes, is provided, the seal is designed such that it remains intact until the overpressure protection device is reliably triggered.The battery cell described here makes do without known complicated cover structures with connection terminals. The installation space requirement for the electrical contacting can thus be significantly reduced. Such a battery cell can therefore be of a lower design than a conventionally designed battery cell or a larger electrochemical element can be accommodated in a battery cell of predefined size.In addition, the number of parts required is significantly reduced and the terminals, which are usually expensive to produce and which often have turning or milling parts and require a plurality of joints, can be dispensed with. This results in a cost advantage.The lead-out of the arresters from the housing allows simpler contacting with adjacent cells or busbars and tolerance compensation, which results in simplified assembly. As a joining technique for contacting the arresters from outside the battery cell, laser beam welding is possible, among other things, which can be carried out more reliably because of the thinner form and with lower power. Consequently, a less dimensioned and more favorable plant technology can be used for the battery cell described here.In a first further embodiment, it is provided that the first diverter and / or the second diverter are formed so as to project outwards from the housing.This facilitates the later assembly of a corresponding battery cell within the traction battery arrangement. The arresters can therefore also serve as cell connectors or for connection to busbars.In a further refinement, it is provided that the first arrester and / or the second arrester are designed as a lug.A corresponding lug is configured in a planar manner. This can result in an improved current flow through a broader-area characteristic of the arresters and thus a larger-area contact.In a further refinement, it is provided that the first arrester is formed from a current collector or is attached thereto and / or that the second arrester is formed from a current collector or is attached thereto.If the first conductor and / or the second conductor are formed directly from the current collector, the number of components and joints can be minimized.In some configurations, it may be necessary to provide a separate arrester which is then preferably connected to the respective current collector as an intermediate element, inter alia by welding or laser welding.In a further development, it is provided that the injection-molded plastic is a sealing material, wherein the first diverter and / or the second diverter are surrounded by sealing material at least in a lead-through section, wherein the sealing material connects the first diverter and / or the second diverter to the housing in a medium-tight and pressure-tight manner.In this embodiment, the arresters are surrounded by sealing material in the passage through the cell housing or the housing cover, wherein the sealing material connects the respective arrester to the housing or the housing cover in a medium-tight manner.In a further development, it is provided that the sealing material contains a thermoplastic, thermosetting plastic and / or adhesive.These materials have proven to be sufficiently stable and durable for use in battery cells for traction batteries of motor vehicles and are suitable for injection molding.In a further refinement, it is provided that the sealing material encloses the first diverter and / or the second diverter from an inner side and / or from an outer side.This allows the best operational reliability to be ensured depending on the respective specific application purpose.In a further refinement, it is provided that the first diverter and / or the second diverter are shaped in the leadthrough section.If the arresters are each designed to be bent one or more times, this leads to an increase in the contact and injection-molded surface area, which improves the sealing and contributes to an improvement in the mechanical stability with respect to pressure differences between internal pressure and external pressure.In a further refinement, it is provided that the first arrester and / or second arrester are roughened and / or cleaned and / or chemically activated in the feedthrough section.According to this embodiment, the surface of the arresters can be treated in order to improve the adhesion between arresters and sealing.Activation can be achieved, inter alia, by applying an adhesion promoter and / or using lasers.Cleaning can be effected in the region of the housing and / or of the conductor in which the seal is to be applied by laser or plasma cleaning methods.Roughening can be achieved, inter alia, mechanically or by laser or electron beam structuring.In a further refinement, it is provided that the first arrester and / or second arrester are insulated in the feedthrough section.This makes it possible to prevent short circuits during the assembly of the battery cell.Further advantages, features and details are evident from the following description, in which--possibly with reference to the drawing--at least one exemplary embodiment is described in detail. Identical, similar and / or functionally identical parts are provided with the same reference numerals.They show schematically: FIG. 1 shows a sectional view through a battery cell, FIG. 2 shows a plan view of the battery cell from FIG. 1 FIG. 3 shows two battery cells during production of a traction battery FIGS. 4A, 4B show two battery cells during two alternative production steps of a traction battery, and FIGS. 5A-5H are enlarged sectional views through housing covers with various embodiments of arresters.Identical or identically functioning components are provided with the same reference numerals in the exemplary embodiments explained below for better readability.FIG. 1 shows a sectional illustration through a battery cell 2.The battery cell 2 corresponds to the basic type of prismatic battery cell and has a multipart housing 4 with a housing trough 6 and a housing cover 8. The housing 4 is dimensionally stable and in the present case consists of metal. The housing cover 8 is placed on the housing trough 6 in FIG. 1 to produce a hermetically sealed housing 4. As soon as the housing cover 8 is connected to the housing trough 6, the housing 4 is pressure-tight up to several bar overpressure. In the housing 4 a non-illustrated overpressure protection can be provided, for example using a rupture element which is destroyed in the event of a fixed overpressure and thereby releases a channel to the outside.The housing tray 6 accommodates an electrochemical element 10 consisting of a plurality of cell stacks. The electrochemical element 10 is a lithium-ion element in the present case.For the purpose of current transport, the electrochemical element 10 is connected on the side shown to a first arrester 12 which assumes the function of a current collector. The first diverter 12 is configured in a planar manner as small fins perpendicular to the plane of representation. The first arrester 12 protrudes substantially perpendicularly from the housing cover 8.The first conductor 12 is led through a lead-through section 14 formed in the housing cover 8. To connect the first arrester 12 to the housing end cover 8, the first arrester is encapsulated by injection molding with a seal 16. The seal 16 consists of plastic, in the present case a thermosetting plastic. The seal 16 fills the passage section 14 completely and adheres firmly to the first conductor 12 and to the housing cover 8.To improve the adhesion between first conductor 12 and seal 16, an insulator layer 18 of first conductor 12 is plasma cleaned and roughened. Thus, the adhesive surface of the conductor increases in the area of contact with the seal 24.FIG. 2 shows a plan view of the battery cell 2.In addition to the first arrester 12, a second arrester 20 is led out of the housing cover 8 from a feedthrough section 22. For this purpose, the second conductor 20, like the first conductor 12, is encapsulated by injection molding with a seal 24 made of a thermosetting plastic. The second diverter 20 is designed as a small receptacle.First conductor 12 and second conductor 20 are arranged on a common plane defined by the housing cover 8.FIG. 3 shows two battery cells 2, 2' of a traction battery 26 during assembly.The battery cells 2, 2' are arranged in their final relative position. The first arresters 12, 12' are bent away to the side, wherein the first arrester 12 of the battery cell 2 rests flat on the first arrester 12' of the battery cell 2'. The two first arresters 12, 12' are welded to one another by means of a laser beam 28.Due to the omission of a connection terminal, the battery cells 2, 2' can accommodate an electrochemical element that is larger by an additional height n at the same overall height, whereby the capacity of the traction battery 26 and the storage density can be increased.FIGS. 4A and 4B show an alternative connection to FIG. 2 between the battery cells 2 and 2', in which the respective first arresters 12, 12' are each bent toward the adjacent battery cell 2', 2.In FIG. 4A, the first arrester 12 of the battery cell 2 is already bent over to the right in the direction of the battery cell 2', whereas the first arrester 12' of the battery cell 2' is bent over to the right in the direction of the battery cell 2.If the first conductor 12' of the battery cell 2' is completely bent, it lies flat on the first conductor 12 of the battery cell 2 and, as is shown in FIG. 4B, can be welded to the first conductor 12 of the battery cell 2 by means of the laser beam 28.FIGS. 5A to 5H show different variants of housing feedthroughs in each case in a sectional illustration enlarged relative to FIG. 1.FIG. 5A shows the passage of the first arrester 12 through the housing cover 8 illustrated in FIG. 1 in an enlarged manner.FIG. 5B illustrates a variant in which the first arrester 12 is not directly connected to the electrochemical element, but rather to a current collector 30 connected to the electrochemical element. This variant is compatible with and may be combined with the embodiments shown in Figures 5C to 5H.In FIG. 5C, the first diverter 12 is angled in a Z-shape and is connected flat to the seal 16 on an outer side 32 of the housing cover 8 in order to enlarge the connecting surface for the seal 16 and in order to ensure strain relief.In FIG. 5D, the first diverter 12 is angled three times and is connected in each case in a planar manner to the seal 16 on the outer side 32 and on an inner side 34 of the housing cover 8.In FIG. 5E, the first diverter 12 is angled four times and is connected in each case in a planar manner to the seal 16 on the outer side 32 and on the inner side 34 of the housing cover 8, wherein the first diverter 12 is formed in a U-shaped manner in this connection region.In FIG. 5F, the first diverter 12 is angled in a Z-shape and is connected flat to the seal 16 on the outer side 32 of the housing cover 8. The seal 16 is formed to be thicker on the outer side 32 of the housing cover 8 than on the inner side 34 of the housing cover 8.In FIG. 5G, the first diverter 12 is angled three times and is in each case encapsulated with the seal 16 on the outer side 32 and on the inner side 34 of the housing cover 8, wherein the diverter 12 encloses laterally on the inner side 34 of the seal 16 and is led out so as to project perpendicularly on the outer side 32 of the seal 16.In FIG. 5H, the first diverter 12 is bent or angled four times and is connected in each case in a planar manner to the seal 16 on the outer side 32 and on the inner side 34 of the housing cover 8, wherein the first diverter 12 is formed in a U-shaped manner in this connection region. The passage section 14 is formed on an edge between the housing cover 8 and the housing trough 6. In addition, the seal 16 is made thicker on the inner side 34 of the housing cover 8 than on the outer side 32 of the housing cover 8.Although the invention has been illustrated and explained in more detail by preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention. It is therefore clear that a large number of possible variations exist. It is also clear that embodiments mentioned by way of example represent only examples which are not to be understood in any way as limiting, for example, the scope of protection, the possible applications or the configuration of the invention. Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, wherein the person skilled in the art, having knowledge of the disclosed inventive idea, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without departing from the scope of protection defined by the claims and their legal equivalents, such as a further explanation in the description.List of reference characters2, 2' Battery cell 4 Housing 6 Housing trough 8 Housing cover 10 Electrochemical element 12, 12' First conductor 14 Feedthrough section 16, 16' Seal 18 Insulator layer 20 Second conductor 22 Feedthrough section 24 Seal 26 Traction battery 28 Laser beam 30 Current collector 32 Outer side 34 Inner side n Additional heightReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2017 200 390 A1

[0009]

Claims

Battery cell (2, 2') for a traction battery arrangement of a motor vehicle, having a dimensionally stable housing (4) in which at least one electrochemical element (10) for storing and delivering electrical energy is arranged, wherein the at least one electrochemical element (10) is contactable in a current-conducting manner by means of a first pole (12, 12') electrically contactable from outside the housing (4) and by means of at least one second pole (20) electrically contactable from outside the housing (4), characterized in that the first pole is designed as a first arrester (12, 12') guided in a sealed manner from the housing (4) and the at least one second pole is designed as a second arrester (20) guided in a sealed manner from the housing (4), wherein the sealing of the first arrester (12, 12') and the second arrester (20) is in each case formed by an encapsulated plastic (16, 16', 24).Battery cell (2, 2') according to Claim 1, characterized in that the first arrester (12, 12') and / or the second arrester (20) are formed so as to project outwards from the housing (4).Battery cell (2, 2') according to Claim 1 or 2, characterized in that the first conductor (12, 12') and / or the second conductor (20) are designed as a flag.Battery cell (2, 2') according to one of the preceding claims, characterized in that the first conductor (12, 12') is formed from a current collector or is attached to a current collector (30), and / or the second conductor (20) is formed from a current collector or is attached to it.Battery cell (2, 2') according to one of the preceding claims, characterized in that the plastic material which is encapsulated is a sealing material (16, 16', 24), wherein the first diverter (12, 12') and / or the second diverter (20) are surrounded by sealing material (16, 16', 24) at least in a passage section (14, 22), wherein the sealing material (16, 16', 24) connects the first diverter (12, 12') and / or the second diverter (20) to the housing (4) in a medium-tight and pressure-tight manner.Battery cell (2, 2') according to Claim 5, characterized in that the sealing material (16, 16', 24) contains a thermoplastic, thermosetting plastic and / or adhesive.Battery cell (2, 2') according to one of the preceding claims, characterized in that the sealing material (16, 16', 24) encloses the first diverter (12, 12') and / or the second diverter (20) from an inner side (34) and / or from an outer side (32).Battery cell (2, 2') according to one of the preceding claims, characterized in that the first conductor (12, 12') and / or the second conductor (20) are formed in the passage section (14, 22).Battery cell (2, 2') according to one of the preceding claims, characterized in that the first conductor (12, 12') and / or the second conductor (20) are roughened and / or cleaned and / or chemically activated in the feedthrough section (14, 22).Battery cell (2, 2') according to one of the preceding claims, characterized in that the first conductor (12, 12') and / or the second conductor (20) are insulated in the feedthrough section (14, 22).

Images