Load structure element for mechanically connecting battery cells

Abstract

The invention relates to a battery for a battery-electric vehicle, comprising a plurality of battery cells (1) and a load structure element (3), wherein the respective battery cells (1) are combined in a cell composite with a cell composite housing and wherein the battery cells (1) or the cell composite housing each have concave bulges (7) into which the load structure element (3) is inserted or through which the load structure element (3) is passed, wherein the load structure element (3) forms force-fitting, material-fitting or positive-fitting connections with the respective battery cells (1).

Description

The invention relates to a battery for a battery-electric vehicle and to a battery-electric vehicle having such a battery.In the course of battery development, in particular of rechargeable batteries for electric vehicles, the volumetric and gravimetric energy density of the battery is further increased. In this case, novel battery cell concepts such as bipolar concepts are also used.JP6636607 B2 relates to a battery structure of a bipolar battery in this respect, comprising a first cell and a second cell, which are arranged in a stacked orientation. The assembly also includes a conductive plate connecting the anode of the first cell to the cathode of the second cell and arranged therebetween for this purpose.With the development of new cell concepts and the accompanying redesign of the entire vehicle battery, a significant enlargement of the electrodes of the batteries is typically associated. With an increase in electrode dimensions under existing requirements for a tensioning of battery cells, the reaction of cell thickness growth forces and with simultaneous homogeneous force distribution over the electrode surface, an enormous increase in the cross section of cell composite end plates can typically be observed, wherein a cell composite can comprise a multiplicity of battery cells. As a limit, it is also conceivable to equip a cell composite segment with only one cell, so that the cell composite construction can be completely omitted in the case of large-format cells. From conventional mechanics it is known in any case that a bending beam clamped on two sides exhibits a higher deflection with increasing length of the bending beam at the same stretching load. This can be counteracted by increasing the cross section of the bending beams or of the end plates in the case of a cell assembly.This phenomenon occurs in addition not only in the case of bipolar cells, but in the case of all cell forms as soon as the electrode dimensions are increased, that is to say in particular also in the case of pouch and hardcase cells.If, in particular, battery cells are integrated into a rigid cell composite housing, cell composite end plates can be bent as a result of excessively large internal influences (for example strong cell thickness growth) and external influences (for example high dynamic loads in driving or an accident of a battery-electric vehicle with strong impulse action). This in turn can lead to displacements and damage of battery components outside the cell assembly or components within the cell assembly, such as cells, cell connectors, busbars and cables, for example, as a result of which voltage peaks or short circuits can in turn be triggered. Material failure and electrolyte leakage cell opening may be consequences.From the publications US 2013 / 0 122 339 A1, US 2005 / 0 089 751 A1, DE 10 2020 200 005 A1 and DE 10 2014 207 403 A1, batteries with several battery modules are known in each case, wherein the individual battery modules are connected to one another via mechanical bracing elements, such as bolts, rods, screws, which are guided through bores of the individual battery modules.It is an object of the invention to improve a battery in a structural mechanical manner without any thickening or stiffening of the cell composite end plates beyond the load structural element being carried out.The invention results from the features of the independent claims. Advantageous refinements and refinements are the subject matter of the dependent claims.The invention is intended to include all flat battery cells, in addition to frame flat cells, in particular also battery cells in solid state technology and pouch cells, wherein here the casing of the respective outer battery cells of the cell assembly is to be understood as a housing.A first aspect of the invention now relates to a battery for a battery-electric vehicle, having a multiplicity of battery cells and at least one load structure element, wherein the respective battery cells can be combined in a cell assembly with a cell assembly housing and / or in a battery with a battery housing, wherein the battery cells and / or the cell assembly each have concave bulges, into which the load structure element is inserted, wherein the load structure element is connected to the cell assembly end plates and / or the battery housing via a force-fit, material-fit, or force-fit connections.Load cases in the load structural element can be complex and depend on the configuration and the geometric configuration of the load structural element and the mechanical connection to the upper and lower end plates of the cell assembly or the battery. However, the load structural element is typically loaded primarily for tensile stress; it can therefore also be called a tension rod.The load structural element serves in this respect in particular to hold the cell assembly or the battery together mechanically by means of force-fit, cohesive or form-fit connections with the upper and lower end plates of the cell assembly or the battery, in particular with the cell housings. For this purpose, one or more load structural elements can be provided.The load structural element is preferably arranged such that it runs through the cell or the cell assembly itself and / or through the interior of the cell assembly housing, so that in particular the total volume of the battery does not increase as seen from the outside due to the introduction of the load structural element.The load-bearing structural element can have any desired geometric base surface, such as an oval or polygonal base surface. The load structure element can also have variable shapes, such as diameters variances, chamfers, notches, recesses or shoulders. In addition, the load structural element can additionally be guided through a sleeve or a sheathing. The sleeve or sheathing can be independent, or else integrated on housing walls or in the load structural element.The load structural element mechanically offers the advantage that an effective length of a section of the battery claimed as a bending beam is reduced in its effective carrier length. Additional bearing points on a rigid structure realized by the load structure element are hereby created. The wall thicknesses of the cell housings and / or of a cell composite housing which accommodates the cells can be smaller than without the presence of the load-structural element.The battery cells are distinguished in that they can be produced in a stacked, wound or Z-folded manner. In particular, the battery cells are arranged in a bipolar arrangement, i.e. not insulated from one another, and are connected in series. Alternatively, parallel cell composites or isolated cell composites are also possible.The geometry of the protrusions can be based on the geometry of the load structure element or can have any other desired geometric contour. The cross section and dimensions of the protrusions preferably correspond at least to those of the load structure element.The use of one or more load structural elements results in the following advantages: the load structural element or elements can serve as guide elements for a stacked, Z-folded or wound cell. The load-bearing structural element enables simplified positioning of the cells during assembly, and also positive positioning outside the assembly process. By using one or more load structural elements, a more homogeneous force distribution is obtained over the respective cell or the cell composite. The more homogeneous force distribution positively influences a respective battery cell and the cell assembly comprising a multiplicity of battery cells mechanically and extends the service life. When one or more load structural elements are used, a significant saving in weight and material on the housing walls can be achieved. Along with this, an increase in the volumetric and gravimetric energy density can be achieved because of the material saving. By integrating measurement pickups, better and direct monitoring of the battery cells can be made possible. By integrating vent devices within a respective load structure element, vent paths are significantly reduced and the behavior can be improved in the case of a "thermal passage" (also: runaway), in particular in the case of large-format battery cells. By integrating cooling solutions within or on one or more load structure elements, it is also possible to achieve improved cooling capability of the overall system. A battery cell or the entire cell assembly with the plurality of battery cells is thereby positively influenced over the service life, as well as in the high-performance range.According to an advantageous embodiment, the load structure element is a bolt or a screw or in particular an element which can be actively controlled or adjusted in length, for example a hydraulic or pneumatic cylinder or an elastically elongated element, for example a tension spring or an expansion rod.According to a further advantageous embodiment, a section of the load structure element is formed as part of the cell composite housing, of the battery housing or as part of at least one cell housing.According to a further advantageous embodiment, the load structural element has a vent channel with a safety valve. The vent channel with the safety valve can be integrated directly into the load structural element or the safety valve can be inserted into a recess specifically provided for this purpose.According to a further advantageous embodiment, the load structure element has a measurement pickup. In this case, for example, one or more measurement pickups for pressure, position, temperature, tensile stress and moisture detection can be inserted into the load structure element.According to another advantageous embodiment, the load structure element has a cooling channel. The cooling channel can be integrated directly into the load structure element.According to a further advantageous embodiment, the respective concave bulges of the cell or of the cell assembly are formed such that the battery cells or cell assembly parts can be sequentially lined up on the load structure element during the assembly into the battery structure, such that the battery cells are aligned as a guide element by the load structure element.According to a further advantageous embodiment, the respective concave bulges are configured such that the structural element can be accommodated therein without any protruding portions.According to a further advantageous embodiment, the concave bulges of the cells or of the cell composite have at least one of the following: measurement pickup, cooling channel, vent channel with a safety valve, electrical line.The concave bulges of any desired geometric design can be used further by using them as a vent channel. The vent paths can thus be minimized and a distinct improvement in the case of a thermal passage can thus be achieved. Alternatively or additionally, measurement pickups can be inserted into the concave bulges. The available installation space can be used, for example, for measurement pickups for pressure, position, temperature, tensile stress / shear stress measurement or for moisture detection. In addition, the concave bulges can be provided with a cooling. The cooling can be inserted into a recess specifically provided for this purpose. In addition, the concave bulges can be used for current tapping or for current supply. Cells or cell composites can be connected both in parallel, in series and isolated from one another. A more homogeneous current distribution can be achieved by the more free placement of the current tap and the current supplies. The construction is suitable both for classic cell arrangements, but above all for bipolar arrangements. The electrical interconnection can be represented independently or as part of the load structure element.The concave bulges can advantageously be used in the assembly process for a simplified positioning of the cells or of the cell composites. Likewise, temporary and permanent fixing via the recesses both during assembly and during later operation would be conceivable. By integrating measurement pickups within the concave bulges, better and direct monitoring of the battery cells or of the cell assembly can be made possible. As a result of the integration of vent devices within the bulges, vent paths are significantly reduced and the behavior can be improved in the case of a thermal passage of a cell. By integrating cooling solutions within the protrusions, an improved cooling capability of the battery can also be achieved. The battery cells or the cell assembly are thereby positively influenced over the service life, as well as in the high-performance range.A further aspect of the invention relates to a battery-electric vehicle having a battery as described above and below.Advantages and preferred refinements of the proposed battery-electric vehicle result from an analogous and analogous transfer of the explanations given above in connection with the proposed battery.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.The following are shown: FIG. 1 : shows a load structural element during assembly with battery cells according to an exemplary embodiment of the invention. FIG. 2 : Exemplary possible designs of the load structure element. FIG. 3 : Example possible extensions of the use of the load structure element. FIG. 4 : Exemplary protrusions of the battery cells for receiving or passing through the load structure element. FIG. 5 : shows a parallel bipolar junction and a serial bipolar junction according to embodiments of the invention.The representations in the figures are schematic and not to scale.FIG. 1 shows a load structural element 3 in the assembly onto which battery cells 1 for a battery of a battery-electric vehicle are lined up. In the finished battery, a plurality of battery cells 1 will be mechanically connected to the load structural member 3. The connection between the load structural element 3 takes place in a form-fitting manner in certain directions, for which purpose the load structural element 3 has a branching at at least one of its ends, against which the battery cells 1 lined up thereon can be supported. Along a web in the longitudinal axis along which the battery cells 1 are lined up, the battery cells can additionally be screwed, welded, or glued or connected to the load structure element 3 by another method.The load structural element can also connect the upper end plate to the lower end plate, wherein the end plates in this case form either the cell composite frame or the battery housing. The cells are positioned in this case by the load structural element and then pressed through the end plates.FIG. 2 shows six possible shapes of the load structural element 3. where different hatchings adjoin one another, the respective load structural element 3 can be joined together from individual parts during assembly, in order to enable the battery cells 1 to be arranged, for example, as described under FIG. 1.The load structural element can also be part of the battery or the cell composite housing or of the cell or of the cell composite and also any end plates.FIG. 3 shows three further examples of a load structural element 3, which is equipped with additional functions in each case. The first of the three load structural elements 3 is equipped with a vent channel 11. Regular cooling functions of the battery cells 1 can thus be implemented by the cooling medium being conducted through the load structural element into the battery. In the application shown in FIG. 3, however, during a thermal passage of at least one of the battery cells 1, hot gas under pressure can be discharged through the load structural element 3, in order thus to avoid the thermal passage from overlapping further battery cells 1. In the load structural element 3 shown in the middle, a strain gauge is arranged on a flank of the load structural element 3. Thus, lifetime analysis of the battery can be carried out, excess voltages are detected, feedback for a development responsible for the battery about loads during operation of the vehicle is generated, or after an accident the material voltage which has occurred in the load structural element 3 can be tracked in order to be able to make a decision about a change of the battery. In the third, right example of a load structural element 3 in FIG. 3, a device for position monitoring is also shown. Thus, displacements or changes in orientation of the load structure element 3 can be checked in the battery in order to draw conclusions about cell thickness growth and aging.FIG. 4 shows an embodiment of a battery cell 1, which have respective concave bulges 7 in order to guide the load structure element 3 (or a plurality thereof) therein or lying thereon. The battery cell 5 has bulges 7 for the passage of the load structural element, wherein a respective load structural element 3 can be completely recessed therein from the outside.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, knowing the disclosed inventive concept, 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 further explanations in the description.List of reference characters1 Battery cells 3 Load structure element 5 Battery cell 7 Bulges 11 Vent channel 13 Measuring pickup

Claims

Battery for a battery-electric vehicle, having battery cells (1) and a load structural element (3), wherein a plurality of battery cells (1) are combined in a cell assembly and the battery cells (1) or the cell assembly housing each have concave bulges (7) into which the load structural element (3) is inserted, wherein the load structural element (3) forms force-fit, material-fit or form-fit connections with the respective battery cells (1).Battery according to claim 1, wherein the load structural element (3) is a bolt or a screw or an element which can be actively controlled or adjusted in length, for example a hydraulic or pneumatic cylinder or an elastically elongated element, for example a tension spring or an expansion rod.Battery according to one of the preceding claims, wherein a section of the load structural element (3) is formed as part of the cell composite housing or as part of at least one cell (5) and possible end plates.Battery according to one of the preceding claims, wherein the load structural element (3) has a vent channel (11) with a safety valve.Battery according to one of the preceding claims, wherein the load structural element (3) has a measurement pickup (13).Battery according to one of the preceding claims, wherein the load structural element (3) has a cooling duct.Battery according to one of the preceding claims, wherein the respective concave bulges (7) of the battery cells (1) or of the cell composite housing are formed such that the battery cells (1) can be sequentially lined up on the load structure element (3) for the battery cells (1) during the mounting of the battery structure, such that the battery cells (1) can be stacked, wound or Z-folded with the aid of the load structure element (3) as a guide element.Battery according to one of the preceding claims, wherein the respective concave bulges (7) are configured such that the structural element can be accommodated therein without any protruding portions.Battery according to one of the preceding claims, wherein the concave bulges (7) of the battery cells (5) or of the cell composite housing have at least one of the following: measurement pickup (13), cooling channel, vent channel (11) with a safety valve, electrical line.A battery electric vehicle comprising a battery according to any preceding claim.

Images