Battery system with positive locking connection structure

Abstract

A battery system (6) with a plurality of battery cells (9) which are received in a row arrangement in a support structure (18), wherein the battery cells (9) bear against the support structure (18) at least at the ends of the row arrangement and wherein the support structure (18) is attached to a fastening structure (7), wherein a fastening section (20) of the support structure (18) extending longitudinally to the row arrangement bears against a fastening section (21) of the fastening structure (7) such that a contact area between the fastening sections (20, 21) extends longitudinally to the row arrangement, wherein the fastening sections (20, 21) are secured against relative movement in at least one direction longitudinally to the row arrangement and wherein the fastening sections (20, 21) form a positively interlocking connection structure (23) longitudinally to the row arrangement.

Description

[0001] The invention relates to a battery system with a plurality of battery cells which are accommodated in a series arrangement within a support structure, wherein the support structure is attached to a mounting structure.

[0002] A battery is an electrochemical storage device for electrical energy, in which stored chemical energy is converted into electrical energy through an electrochemical redox reaction during discharge. In the context of the invention, the term "battery" refers to both primary batteries, which are designed for a single discharge and not for recharging, and secondary batteries or accumulators, which are designed and intended for multiple charging and discharging cycles. Charging a secondary battery represents the electrolytic reversal of the electrochemical redox reaction that occurs during discharge, achieved by applying an electrical voltage.

[0003] According to the invention, a battery cell is defined as a battery which, in addition to one or, usually, several battery elements (galvanic cells), also comprises at least one or more battery elements (galvanic cells) surrounding the battery element(s), usually in the form of a foil pouch or a dimensionally stable housing. The battery element(s) of a battery (cell) each has at least two electrodes, a separator arranged between the electrodes for electrical separation of the electrodes, and an electrolyte as an ion conductor.

[0004] Typically, a variety of battery elements, for example in the form of a stacking or winding of electrodes and separators, are combined in a battery cell to achieve a sufficiently high electrical performance. The various components present as a stacking or winding (hereinafter referred to as "layering") within the casing of a battery cell, i.e., in particular the electrodes and separators, are referred to below as "battery layers".

[0005] For particularly high performance requirements, such as those placed on a traction battery of a motor vehicle, a large number of battery cells are combined in so-called battery stacks.

[0006] When designing a battery cell, especially a lithium-ion battery (e.g., LFP lithium iron phosphate or NMC nickel-manganese-cobalt), and especially a component integrating several such battery cells, a relevant volume change (so-called "swelling") of the battery layers must be taken into account, whereby such volume changes can occur both once during the manufacture of the battery, especially due to impregnation of the battery layers with a liquid electrolyte, and regularly during each charging or discharging process as a result of lithiation / delithiation of the electrodes, whereby the extent of these volume changes tends to increase over the operating life of the battery cells.Such a change in volume leads to varying pressures exerted on the battery layers, which can negatively affect the electrochemical performance and / or to a relevant change in the dimensions (volume change) of the battery cell.

[0007] When designing a battery cell or a component integrating one or more battery cells, attempts are typically made to account for the volume changes and swelling that occur during subsequent use. Such usage-dependent volume changes in a battery cell can result in increased stresses on the structure that holds the battery cell. These increased stresses must be compensated for by a correspondingly robust design of the structure that secures the battery cell, which can negatively impact costs and / or the required installation space.

[0008] DE 10 2018 120 230 A1 discloses a battery housing with a receiving space into which an electrical energy storage device can be inserted, with a dimensionally stable side wall enclosing the receiving space laterally and with at least one plastically deformable and energy-absorbing element arranged laterally outside the dimensionally stable side wall.

[0009] The invention is based on the objective of demonstrating a way to advantageously integrate a plurality of battery cells into a structure, taking into account their volume change behavior.

[0010] This problem is solved in a battery system according to claim 1. A motor vehicle with such a battery system is the subject of claim 8. Preferred embodiments of the battery system and the motor vehicle according to the invention are the subject of further claims and will become apparent from the following description of the invention.

[0011] The invention relates to a battery system with a plurality of battery cells arranged in a row within a support structure, wherein the battery cells bear against the support structure at least at the ends of the row arrangement. As a result, volume changes acting along the length of the row arrangement are transmitted by the battery cells to the support structure, which could cause at least slight deformation of the support structure. Such deformations of the support structure, or the forces resulting therefrom, would be transmitted to a mounting structure to which the support structure is attached. According to the invention, this mounting structure consists of a mounting that extends (also) along the length of the row arrangement.Regarding the row arrangement, a mounting section of the support structure extending to a mounting section of the mounting structure is attached such that a contact area between the mounting sections also extends longitudinally to the row arrangement, wherein the mounting sections are secured against relative movement in at least one direction longitudinally to the row arrangement. For this purpose, the mounting sections can be pressed against each other by means of at least one fastening element, in particular a screw connection, preferably by means of several fastening elements. A transmission of forces between the support structure and the mounting structure resulting from volume changes of the battery cells could therefore be based exclusively on the at least one fastening element, so that this or these would have to be designed to be correspondingly robust and thus usually expensive and / or heavy.To avoid this, or at least to keep the load on the at least one fastening element relatively low, the invention further provides that the fastening sections form a positive-locking connection structure that is effective at least also longitudinally to the row arrangement, so that the connection structure, and thus the fastening sections interacting positively with each other via this connection structure, transmit or support forces between the supporting structure and the fastening structure to a considerable extent, forces that result from volume changes of the battery cells. This allows the at least one fastening element for pressing the fastening sections to be relatively weak and therefore cost-effective and lightweight.In principle, it is even possible to do without at least one fastening element and thus, if necessary, to support forces between the supporting structure and the fastening structure resulting from volume changes of the battery cell exclusively via the form-fitting connection structure.

[0012] The battery cells of a battery system according to the invention can each comprise a plurality of electrodes and separators arranged in a layered configuration within a battery cell casing, the layering pattern corresponding to the row arrangement of the battery cells. This ensures that the supporting function of the form-fitting connection structure advantageously acts at least in those directions where the overall volume changes of the battery cells can be greatest.

[0013] According to a preferred embodiment of a battery system according to the invention, the fastening sections can each form a plurality of projections spaced apart along the row arrangement of the battery cells, with the projections of the various fastening sections interlocking to form the connection structure. This represents a simple, cost-effective, and simultaneously highly resilient connection structure. Furthermore, such a configuration of the connection structure allows the fastening sections to interact in different relative positions, at least along the row arrangement, thereby simplifying the assembly of the battery system and compensating for tolerance-related positional and dimensional deviations of the battery system components, in particular the support structure and the fastening structure.

[0014] It is further preferred that the projections be tapered, particularly tapered, so that they have continuously decreasing cross-sectional areas from a base of the projection to a head or the free end of the projection. This ensures that the projections interlock without requiring particularly precise positioning of the fastening sections of the supporting structure and the fastening structure relative to each other. It also eliminates the need for particularly precise manufacturing of the projections to guarantee their interlocking. Consequently, correspondingly tight manufacturing tolerances and the associated high production costs can be avoided.

[0015] To ensure that the connection structure has a sufficient positive locking effect, it is preferable that the projections each have a height (shortest distance between the base and the head of a projection) of at least 0.5 mm or 1 mm. Alternatively, it may be advantageous if the projections each have a height of no more than 3 mm or 5 mm (please specify if applicable), thereby enabling simple and cost-effective manufacturing while maintaining a sufficient positive locking effect.

[0016] The invention also relates to a motor vehicle, in particular a wheel-based and non-rail-bound motor vehicle (preferably a car or a truck), with a battery system according to the invention.

[0017] The majority of the battery cells can, in particular, be a traction battery of the motor vehicle or at least a part of such a traction battery, by means of which at least one electric traction motor of an electric motor vehicle can be supplied with the electrical power required for its operation. An "electric motor vehicle" is defined as a motor vehicle that includes at least one such electric traction motor, by which the motor vehicle can be driven on its own. The motor vehicle may consist exclusively of the at least one electric traction motor ("electric vehicle") or the at least one electric traction motor may be provided in addition to another drive device, in particular an internal combustion engine ("hybrid vehicle").

[0018] The invention is explained in more detail below with reference to an embodiment illustrated in the drawings. The drawings show, in simplified form: Fig. 1: a chassis of a motor vehicle; Fig. 2: a motor vehicle battery system; Fig. 3: the one in the Fig. 2. Section marked III in enlarged view; Fig. 4: a battery cell of the battery system; Fig. 5: a longitudinal section through the battery cell; Fig. 6: A schematic representation of a connection structure of the battery system.

[0019] The Fig. Figure 1 shows a floor assembly 1, which is part of a body for an electric motor vehicle. The floor assembly 1 is known to provide, among other things, mounting points for components of a chassis and a powertrain of the motor vehicle and can be made, at least partially, from formed sheet metal. The section of the floor assembly located between two axles of the motor vehicle is hereinafter referred to as the intermediate floor 2. This intermediate floor 2 is formed, among other things, by longitudinal beams 3, crossbeams 4, and floor panels 5, these components defining a receiving space (not shown) for accommodating a (traction) battery system 6 (see Figure 1). Fig. 2 and Fig. 3) of the motor vehicle. This receiving space and thus the battery system 6 are located below the floor panels 4 of the intermediate floor 2, with a flat body structure serving as underride protection also being arranged below the battery system 6 (not visible).

[0020] Battery system 6 is in the Fig. 2 and Fig. Figure 3 is shown in isolation. This includes a battery system housing comprising a housing frame 7, which serves as a mounting structure for the battery system 6 and forms connecting openings 8 through which the housing frame 7, and thus the battery system 6, is or can be connected to longitudinal beams 3 and transverse beams 4 of the intermediate floor 2. The battery system housing further comprises a housing base (not visible) and a housing cover (not shown). A plurality of battery cells 9 are arranged within the battery system housing and are electrically interconnected to provide, as a traction battery, a sufficient amount of electrical power to propel the vehicle's electric traction motor (not shown).

[0021] The battery cells 9 are designed as so-called prismatic battery cells 9 and therefore have a cuboid-shaped battery cell housing 10, which can be made of a metal (e.g. aluminium), with battery elements included in it (cf. Fig. 4 and Fig. 5) Specifically, the battery elements are stacked in the form of an electrode-separator assembly (ESA) 11. Alternatively, a wound arrangement of the battery elements can also be provided. The ESA 11 comprises, in an alternating arrangement, a plurality of first electrodes 12a, which function as anodes during discharge of the battery cell 9, and a plurality of second electrodes 12b, which function as cathodes during discharge of the battery cell 9. As a result of the alternating arrangement of the electrodes 12, with the exception of the two electrodes 12 located on the outside of the stack or the ESA 11, a first electrode 12a is always arranged between two second electrodes 12b and a second electrode 12b is always arranged between two first electrodes 12a. Adjacent electrodes 12 are spatially separated by a separator 13 and are thus also electrically isolated from one another.Each battery cell consists of a first electrode 12a and a second electrode 12b, as well as a separator 13 arranged between them and impregnated with an electrolyte. The electrolyte allows ions to conduct between adjacent electrodes 12 via the separator 13 located between them.

[0022] Each of the electrodes 12 comprises a planar, foil-shaped substrate 14, which, for example, can be made of copper for the first electrodes 12a, intended as anodes, and of aluminum for the second electrodes 12b, intended as cathodes. In a rectangular section of this substrate, the two large surfaces of each electrode 12, located in the stacking direction of the ESV 11, are coated with an active material 15 to enable the different electrodes 12a and 12b to function as anodes or cathodes during use of the battery cell 9. At least in the area of ​​these rectangular sections of the substrates 14, and thus of the electrodes 12, these substrates and the corresponding rectangular separators 13 are stacked, resulting in the cuboid shape of the ESV 11.

[0023] On one transverse side of the rectangular section of each electrode 12, a region of the substrate 14 is provided in which it is not coated with the respective active material 15. This region of the electrodes 12 serves as a current collector 16, via which the individual electrodes 12 are directly or indirectly electrically connected to a corresponding battery terminal 17 of the battery cell 1. The current collectors 16a of all first electrodes 12a are connected to a first (17a) of the battery terminals 17, and the current collectors 16b of all second electrodes 12b are connected to a second (17b) of the battery terminals 17.

[0024] The battery cells 9 of the battery system 6 are arranged in a total of three groups and in these groups in a row arrangement in a support structure 18 of the battery system 6, wherein the battery cells 9 located at the ends of the row arrangements are each located against a support frame 19 of the support structure 18.

[0025] The battery cells 9 are arranged in series such that the battery cell housings 10 of the battery cells 9 in a group are arranged adjacent to one another with their large surface areas. This type of series arrangement, in combination with the corresponding stacking of the battery layers of the individual battery cells 9, results in volume changes of the battery layers also having a significant effect on the dimensions along the row arrangement of the battery cells 9.Since the battery cells 9 are arranged in rows within the support structure without any significant excess length, changes in volume, or at least increases in volume, result in considerable forces acting longitudinally on the support structure 18 along the rows. This could cause the support structure 18 to deform to a considerable extent. However, this is prevented by a correspondingly robust fastening of the support structure 18 to the mounting structure 7 of the battery system 6. This fastening is achieved by means of plate-shaped mounting sections 20 of the support structure 18, which rest on mounting sections 21 of the mounting structure 7. This creates a horizontally oriented contact area between the adjacent mounting sections 20 and 21. This contact area consequently also extends longitudinally along the rows of the battery cells 9.Thus, the adjacent mounting sections 20, 21 generally allow limited movement of the support structure 18 with the battery cells 9 relative to the mounting structure 7, including longitudinal movement with respect to the row arrangement of the battery cells 9. Furthermore, the installation space provided within the mounting structure 7 or the battery system housing for accommodating the support structure 18 with the battery cells 9 is designed with a defined allowance to accommodate possible form and position tolerances of these components and to enable easy assembly of the battery system 6.

[0026] In the fully assembled state of the battery system 6, movement of the support structure 18 with the battery cells 9 relative to the mounting structure 19 is prevented by a plurality of fastening elements in the form of screws 22, which press the mounting sections 20, 21 against each other or clamp them together. If the adjacent contact surfaces of the respective adjacent mounting sections 20, 21 of the support structure 18 and the mounting structure 7 were smooth, the screw connections 22 would have to generate such a high clamping pressure that relative movements, including those resulting from volume changes of the battery cells 9 that occur during use, would be reliably prevented. The screw connections 22 would then have to be designed to withstand corresponding loads.

[0027] To avoid this disadvantage, the invention provides that the adjacent fastening sections 20, 21 form a positive-locking connection structure 23 at least longitudinally to the row arrangement, as shown in a simplified representation in the Fig.Figure 6 illustrates this. Accordingly, the fastening sections 20, 21 each form an angular profile in the area of ​​their contact surfaces, which has a plurality of tapered projections 24 (with equal angles of inclination of both flanks) spaced apart along the row arrangement of the battery cells 9. The projections 24 of the different fastening sections 20, 21 interlock to form the connecting structure 23. Alternative profile shapes for the projections 24, for example rectangular, wavy, or sawtooth-shaped (with unequal angles of inclination of the two flanks), are also advantageously feasible. Due to this positive-locking connecting structure 23 along the row arrangement of the battery cells 9, only relatively small forces are required to clamp the fastening sections 20, 21 in order to achieve a sufficiently strong connection between the support structure 18 and the fastening structure 7.These relatively small forces can therefore be achieved with relatively small dimensions and / or with a relatively small number of screw connections 22, which has an advantageous effect with regard to the mass of the battery system 6 and the costs associated with its manufacture.

[0028] Furthermore, the design of the connecting structure 23 with a plurality of projections 24 makes it possible to ensure that the support structure 18 and the fastening structure 7 do not need to be positioned in a precisely defined relative arrangement for fastening to one another, but rather that this is possible within a defined tolerance range. This also has an advantage with regard to the manufacturability and assembly of the battery system 6. This also applies to the tapered design of the projections 24, which enables self-positioning of the fastening sections 20, 21 and thus of the support structure 18 relative to the fastening structure 7, as the projections 24 of the two fastening sections 20, 21 can slide against each other until they fully engage. Reference symbol list 1 Floor assembly 2 intermediate floors 3 longitudinal beams 4 crossbeams 5 Base plate 6 battery system 7 Housing frame / mounting structure 8 Connecting opening 9 battery cells 10 battery cell housings 11 Electrode separator composite (ESV) 12 electrode 12a first electrode 12b second electrode 13 Separator 14 Substrat 15 Active material 16 current collectors 16a first current collector 16b second current collector 17 Battery terminal 17a first battery terminal 17b second battery terminal 18 Supporting structure 19 support frames 20 Fastening section of the supporting structure 21 Mounting section of the mounting structure 22 Screw connection 23 Connection structure 24 lead QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 120 230 A1

[0008]

Claims

[1] Battery system (6) comprising a plurality of battery cells (9) arranged in a row in a support structure (18), wherein the battery cells (9) bear against the support structure (18) at least at the ends of the row arrangement and wherein the support structure (18) is attached to a fastening structure (7), wherein a fastening section (20) of the support structure (18) extending longitudinally to the row arrangement abuts a fastening section (21) of the fastening structure (7) such that a contact area between the fastening sections (20, 21) extends longitudinally to the row arrangement, wherein the fastening sections (20, 21) are secured against relative movement in at least one direction longitudinally to the row arrangement and wherein the fastening sections (20, 21) form a positively interlocking connection structure (23) longitudinally to the row arrangement. [2] Battery system (6) according to claim 1, characterized by, that the battery cells (9) each comprise a plurality of electrodes (12) and separators (13) arranged in a layered arrangement within a battery cell housing (10), wherein the course of the layering corresponds to the course of the row arrangement of the battery cells (9). [3] Battery system (6) according to claim 2, characterized by , that the fastening sections (20, 21) are pressed against each other by means of at least one fastening element. [4] Battery system (6) according to claim 3, characterized by , that the fastening element is designed as a screw connection (22). [5] Battery system (6) according to any one of the preceding claims, characterized by, that the fastening sections (20, 21) each form a plurality of projections (24) which are spaced apart along the row arrangement of the battery cells (9), wherein the projections (24) of the fastening sections (20, 21) interlock to form the connecting structure (23). [6] Battery system (6) according to claim 5, characterized by , that the projections (24) are tapered. [7] Battery system (6) according to claim 5 or 6, characterized by , that the projections (24) each have a height of at least 0.5 mm or 1 mm and / or of at most 3 mm or 5 mm. [8] Motor vehicle with a battery system (6) according to any one of the preceding claims.

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