Battery cell module, method for manufacturing same, and computer program product

Abstract

The present invention relates to a battery cell module (2) having at least one battery cell stack (4) and at least one housing (6), the battery cell stack (4) being arranged in the housing, wherein the battery cell stack (4) has a plurality of battery cells (8) and a plurality of separating layers (10) which are stacked adjacent to one another in the stacking direction (S), wherein the separating layers (10) are designed to deform in the event of swelling or movement of one or more battery cells (8), and wherein the battery cells (8) and the separating layers (10) are assembled into a battery cell stack (4) such that an irregular layout (AN) is formed for the separating layers (10) in the stacking direction (S). Furthermore, a method for manufacturing such a battery cell module (2) and a computer program product are provided.

Description

Field of the Invention

[0001] The present invention relates to a battery cell module, a method for manufacturing such a battery cell module, and a computer program product comprising a program, wherein it is advantageous to use the program in the method. Background Art

[0002] Battery cell modules are used to store and provide electrical energy and are accordingly also referred to as batteries. Battery cell modules are often used in vehicles with electric drive means to supply them with energy. Corresponding battery cell modules usually have a plurality of individual battery cells (or battery single cells), for example 10, 100 or 1000 battery cells, which are arranged together in a housing. Here, these battery cells are combined into one or more battery cell stacks. The battery cells are furthermore electrically connected to generate the required voltage and the required current, for example 200 V or more, 1 A or more.

[0003] An individual battery cell is designed, for example, as a lithium-ion battery cell, i.e. having an electrochemically active material based on lithium. A battery cell has at least two electrodes and an active material, as well as a battery cell housing surrounding the electrodes and the active material. Different types of battery cells are possible, for example: pouch battery cells, prismatic battery cells and cylindrical battery cells. These types differ mainly in the geometry of the battery cell housing.

[0004] By principle, the battery cells of a battery cell module expand irreversibly over time. This is the result of repeated discharging and charging and storage of the battery cells. One discharge and recharging is also referred to as one "cycle". Over time, the battery cell module undergoes a plurality of cycles, usually hundreds or thousands of cycles, and thus shows signs of aging. One of these aging phenomena is the aforementioned expansion, i.e. the volume of the battery cell increases irreversibly. This in turn leads to corresponding forces, stresses and movements in the battery cell module, since the battery cells often directly abut each other or at least expand and / or move to such an extent after a certain time that they hit the surrounding battery cells or structural elements of the battery cell module. These forces, stresses and movements increase over time and pose a risk of mechanical damage to the individual battery cells and the entire battery cell module. Since the expansion and movement are irreversible, there is interest in preventing the expansion and movement of the battery cells as far as possible, or at least designing them in such a way that the risk of damage is minimized over as long a period as possible. Summary of the Invention

[0005] Against this background, the technical problem to be solved by the present invention is to avoid or at least postpone as much as possible the damage to the battery cell module due to the swelling and / or movement of the battery cells. This increases the service life of the battery cell module, measured, for example, in days or number of cycles. Accordingly, an improved battery cell module is provided. In addition, a method for manufacturing such a battery cell module should be provided. In addition, a computer program product used in such a method should be provided.

[0006] According to the present invention, the above technical problem is solved by a battery cell module having the features according to the present invention, a method having the features according to the present invention, and a computer program product having the features according to the present invention. Advantageous designs, improved designs, and variant designs are the subject of the following description. The description in connection with the battery cell module is suitably applicable to the method and the computer program product, and vice versa.

[0007] The battery cell module has at least one battery cell stack and at least one housing, and the battery cell stack is arranged in the housing. The battery cell stack has a plurality of battery cells and a plurality of separation layers, which are stacked adjacent to each other in the stacking direction. The separation layers are designed to deform (i.e., compress, yield) in the case of swelling or movement of one or more battery cells, and in particular absorb mechanical loads, such as forces and movements. Accordingly, the separation layers are also referred to as compression zones, compression layers, buffer separation layers, buffer pads, or force-absorbing components. The swelling or movement of the battery cells particularly occurs during the aging of the battery cells, for example, due to the repeated discharging and charging of the battery cells during the regular use of the battery cell module or simply during the storage of the battery cells. The swelling and displacement of the battery cells particularly occur in the stacking direction, but not necessarily only in the stacking direction. The expression "swelling or movement" includes both the case of only swelling or only moving and the case of both swelling and moving. Such swelling or change is also referred to as a change in the geometry of the battery cells.

[0008] The battery cells and the separation layers are assembled into a battery cell stack such that an irregular layout is formed for the separation layers in the stacking direction. Each separation layer and each battery cell are arranged in corresponding positions in the battery cell stack in order to form a definite order or a definite pattern of the battery cells and the separation layers. The term "irregular layout" is understood to mean that the separation layers are not regularly distributed along the battery cell stack, but the distances of the separation layers observed in the stacking direction are variable, such that in particular the number of battery cells arranged between two successive separation layers is variable. The terms "pattern" or "sequence" can also be used instead of the term "layout".

[0009] The corresponding separating layer is also referred to as "compression pad" or "cushion pad" (i.e., compression plate or compression pad or pressing plate or pressing pad) and is substantially compressible, especially when the separating layer is made of a compressible material, such as foam. Preferably, the separating layer is made of a solid material with corresponding pores, air gaps or the like to form a foam, for example similar to a sponge. Alternatively, other materials and designs are also suitable as the separating layer, such as the so-called gel pad, which is made of gel. The separating layer occupies a volume in the battery cell stack, and this volume is gradually occupied by the expansion or movement of the battery cells during the service life of the battery cell module. On the contrary, the separating layer is pressed together and compressed. Therefore, the separating layer absorbs mechanical loads to a certain extent without thereby damaging the battery cells, and thus serves as a so-called sacrificial layer. However, due to the principle, the ability of the separating layer to absorb mechanical loads is limited, so that with the continuous aging of the battery cell module, damage will occur sooner or later, especially when the separating layer is compressed to the minimum thickness. Now, the present invention is especially based on the observation that although the separating layer is used, mechanical loads still occur in the battery cell module and cause damage.

[0010] Each battery cell has a battery cell housing, at least two electrodes and at least one active material arranged therein. In particular, it is understood here that a corresponding active material is arranged on each electrode, but for the sake of simplicity, the corresponding active materials of the electrodes are hereinafter summarized as the "active material" or "active materials" of the battery cell in the term. The active material undergoes electrochemical degradation with continuous use and thus expands irreversibly over time, so that the battery cell housing expands and deforms accordingly. Due to the housing of the battery cell module, the structural space for accommodating the battery cells is correspondingly limited and its expansion or movement can also only be limited. In addition, the battery cell, more precisely its battery cell housing, is appropriately provided with a thermal conductive paste, and the thermal conductive paste also appropriately establishes thermal contact with the housing of the battery cell module. However, this thermal conductive paste usually also acts like an adhesive, that is, it presents adhesion and, according to different layouts, fixes the battery cells to each other on the one hand and fixes the battery cells to the housing on the other hand. The expansion or movement of the battery cells usually results in relative movement between the active material of the battery cells and its battery cell housing. When the movement is large enough, local particularly large expansion occurs and thus correspondingly higher surface tension (or called surface stress) of the battery cell housing is generated. When the maximum value of the surface tension is exceeded, the battery cell housing is damaged, such as the tearing of the membrane in a pouch-type battery cell.

[0011] In principle, it can be conceived that separation layers are simply inserted at regular distances along the battery cell stack and that so many separation layers are used here that damage can be excluded within the specified service life of the battery cell module, for example within 10,000 cycles. Although this is particularly simple in terms of production technology, it is not optimal especially when the battery cell module is used in a vehicle with an electric drive, because the more separation layers are used, the greater the structural space required, that is, the fewer battery cells the battery cell module contains for a constant size, resulting in a decrease in the energy density of the battery cell module. Conversely, the battery cell module becomes heavier as its size increases. Accordingly, it is desirable to limit the number of separation layers to a minimum as much as possible and thus save as much structural space as possible.

[0012] It has now been recognized that the swelling or movement of the battery cells of the battery cell stack does not necessarily occur evenly distributed over the battery cell stack, but varies greatly locally and accordingly results in great differences in mechanical loads locally. The term "mechanical load" is preferably understood as "the surface tension of the battery cell housing". On this basis, it is advantageous to arrange the separation layers such that the relative local movement between the battery cell housing and the corresponding active material is minimized and the local forces are equalized here. Accordingly, the separation layers are arranged irregularly distributed in the stacking direction here and thus have an irregular layout. The danger in a regular layout of the separation layers is that multiple battery cells (or even only a small number of battery cells) experience mechanical loads above the average level, while the mechanical loads for the remaining battery cells are small compared to this. The separation layers in the vicinity of this strongly loaded battery cell are quickly consumed, i.e., compressed. Accordingly, the separation layers are arranged here exactly as needed to achieve the most uniform distribution of mechanical loads and at the same time save as much structural space as possible.

[0013] Suitably, the separation layer also has thermal separation properties, that is, only limited thermal conductivity. Here, it is advantageous if the thermal conductivity of the corresponding separation layer is as low as possible, such that the separation layer has a high thermal resistance. The separation layer accordingly reduces the heat transfer from the battery cells on one side of the separation layer to the battery cells on the other side of the separation layer. The reduction of heat transfer depends on the thermal resistance of the separation layer. Suitable materials with low heat conduction capacity are, for example, aerogels, for example with a heat conduction capacity of 0.06 to 0.08 W / (m*K). The thermal separation properties of the separation layer are preferably used as a design parameter in the manufacture of the battery cell stack.

[0014] The number of battery cells in a battery cell stack is suitably 2 to 10 times greater than the number of separating layers in the battery cell stack. However, a design with a quantity ratio outside the above range is also conceivable and suitable in principle. In a suitable design, the battery cell stack has 12 or 24 battery cells and only 5 separating layers. The battery cell module has one or more such battery cell stacks. Generally speaking, a single battery cell stack extends especially from one end of the housing of the battery cell module to the opposite end of the housing. If there are multiple battery cell stacks, these battery cell stacks are preferably arranged adjacent to each other laterally, i.e., in a direction perpendicular to the stacking direction.

[0015] Suitably, the respective separating layer has a thickness that is between 10% and 30% of the thickness of the respective battery cell. Here, the thickness is measured in the stacking direction. In addition, a design with a thickness ratio outside the above range is also conceivable and suitable in principle.

[0016] From the description of the number and thickness of the battery cells and the separating layers, it can be seen that the battery cells generally constitute the main part of the battery cell stack.

[0017] Preferably, the battery cells are each designed as so-called pouch-type battery cells or prismatic battery cells, i.e., the battery cells are pouch-type battery cells or prismatic battery cells. Hereinafter, without limiting generality, the starting point is a battery cell module with pouch-type battery cells, but the solutions and designs described herein are also advantageously similarly applicable to other types of battery cells, especially prismatic battery cells or even cylindrical battery cells, because these battery cells also exhibit problems of swelling or movement. Pouch-type battery cells are generally flat, wherein the thickness of the pouch-type battery cell extends in the stacking direction and is usually the smallest dimension of the pouch-type battery cell. Generally, the thickness of the pouch-type battery cell is smaller than its height and width by one or more orders of magnitude.

[0018] It is suitable that the battery cells are connected to the housing of the battery cell module by a thermal conductive paste. The thermal conductive paste especially establishes thermal contact between the battery cells and the housing of the battery cell module, and also directly establishes thermal contact between the battery cells if necessary. In addition, the thermal conductive paste especially also acts like an adhesive, i.e., it acts as an adhesive and fixes the battery cells to the housing and also fixes the battery cells to each other if necessary. The thermal conductive paste is preferably only arranged on one side of the battery cell stack, for example, the bottom side, while the opposite side of the battery cell stack, i.e., the top side for example, does not have the thermal conductive paste. The separating layers in the battery cell stack are also fixed especially by the thermal conductive paste. Direct contact between the separating layer and the thermal conductive paste is advantageous but not absolutely necessary.

[0019] In the case of pouch-type battery cells, the cell housing is typically a pouch made of a film. For the film, there is a risk of damage when the cell expands or moves, for example, cracks are formed or punctured by adjacent components. For example, fixing the film in a sectional manner, such as by using thermal paste on one side, may cause the film to move relative to the electrodes and the active material within the film, with a corresponding risk of damage. In a basically suitable design, the cell stack is provided with thermal paste on the bottom side and is in thermal contact with the housing of the cell module through the thermal paste. The thermal paste is at the same time an adhesive that fixes the bottom side of the cell stack, while the opposite top side of the cell stack is not fixed. This affects the deformation of the cell stack when the cells expand or move.

[0020] In a particularly preferred design, the layout of the separation layers is such that every two (viewed in the stacking direction) successive separation layers are spaced apart from each other by a distance that increases in the direction towards the center of the cell stack. Similar to the increase in the distance, when the thickness of the cells remains constant, the number of cells between two separation layers increases in the direction towards the center. This irregular layout is based on the knowledge that towards the end direction of the cell stack, i.e., away from the center, the mechanical load on individual cells, especially in the form of compressive force, decreases. In other words: the mechanical load, especially the compressive force, acting on individual cells increases in the direction towards the center of the cell stack. The enhanced positioning of the separation layers towards the center may cause relatively large movement of the cells in the center due to high expansion and movement forces, and thereby increase the surface tension of the corresponding cell housing, which may facilitate possible failures. Therefore, the cell stack has relatively less dense separation layers towards the center, saving structural space.

[0021] However, it is already known that in some cases, the opposite design is advantageous. Whether the distance increases or decreases depends especially on the stiffness present at the end sides of the cell stack, i.e., on the stiffness of the housing itself or the stiffness of the ends of the cell stack.

[0022] Accordingly, in an advantageous variant design, the layout of the separation layers is such that every two successive separation layers are spaced apart from each other by a distance that decreases in the direction towards the center of the cell stack. Now, the distance decreases in the direction towards the center, rather than increasing in the direction towards the center as described above. Particularly advantageously, a soft material is arranged at the ends of the cell stack in the stacking direction, which is either the last layer of the cell stack or a part of the housing that supports the cell stack at the end side. The housing is made of metal, for example, aluminum, and thus has high stiffness. Then, the last layer of the cell stack or the part of the housing in contact with the ends of the cell stack is made of a material with relatively lower stiffness compared thereto, such as polyurethane or aerogel.

[0023] The "stiffness" of a material is generally understood in particular to be its expansion stiffness, shear stiffness, bending stiffness or torsional stiffness, or a combination thereof.

[0024] Particularly preferably, one of the separating layers of the plurality of separating layers of the battery cell stack forms the last layer, preferably at both ends of the battery cell stack (i.e., there are separating layers at both end portions). In a suitable design, the battery cell stack has separating layers on the end sides respectively, and the separating layers are made of a material having a stiffness lower than that of the housing, i.e., lower than the material of which the housing is made. Independently of the stiffness and independently of whether the distance increases or decreases or is irregular in some other way, it is advantageous that separating layers are arranged on the end sides in the battery cell stack.

[0025] Generally, when the housing has a high stiffness, the distance preferably increases, and when the housing has a low stiffness, the distance preferably decreases. Similarly, when there is a high stiffness on the end side of the battery cell stack, the distance preferably increases, and when there is a low stiffness on the end side of the battery cell stack, the distance preferably decreases. A high stiffness is produced, for example, when the housing is made of metal and the battery cell stack is pressed against the housing in the stacking direction, wherein battery cells are arranged as the last layer on the end side of the battery cell stack. A low stiffness is produced, for example, when the housing is made of metal and the battery cell stack is pressed against the housing in the stacking direction, wherein a separating layer is arranged as the last layer on the end side of the battery cell stack, and the separating layer is deformed as designed above.

[0026] In a suitable design, at least two of the plurality of separating layers have different stiffnesses. Which separating layer has which stiffness is basically variable, and various designs are feasible. In a feasible and advantageous design, the stiffness of the separating layer increases or decreases in the direction towards the center of the battery cell stack when observed in the stacking direction. Herein, "increase" and "decrease" are particularly understood to mean that two successive separating layers in the stacking direction respectively have different stiffnesses. However, this does not necessarily apply to all pairs of successive separating layers, because it is also possible that some successive separating layers have the same stiffness. What is important in particular is that at least two separating layers have different stiffnesses. The stiffness can be suitably set, i.e., by changing the thickness and / or the material of the separating layer.

[0027] The distance between two successive separating layers is measured, for example, in terms of the number of battery cells, where all the battery cells have the same thickness. In a suitable design with 12 battery cells and 5 separating layers, one of the separating layers is arranged in the center of the stack of battery cells, and two adjacent separating layers are arranged at a distance of 3 battery cells relative thereto. Then there is an alternation of 1 battery cell and 1 separating layer, such that the stack of battery cells ends with battery cells at the end sides. The layout of the battery cells and separating layers from one end of the stack of battery cells to the other is: 1 battery cell, 1 separating layer, 1 battery cell, 1 separating layer, 4 battery cells, 1 separating layer (center), 4 battery cells, 1 separating layer, 1 battery cell, 1 separating layer, 1 battery cell. For a stack of battery cells with 24 battery cells and 5 separating layers, where the number of battery cells is doubled, the layout is, for example: 3 battery cells, 1 separating layer, 3 battery cells, 1 separating layer, 6 battery cells, 1 separating layer (center), 6 battery cells, 1 separating layer, 3 battery cells, 1 separating layer, 3 battery cells. The above layout is an irregular layout, where the distance between successive separating layers increases towards the center. The layout can be summarized as a layout with 5 separating layers, where the distance of the central separating layer relative to its two adjacent separating layers is two to four times the distance between the two outermost separating layers. In contrast, in a regular layout, the distance between two separating layers is always the same, for example, 3 battery cells in the case of 12 battery cells, where the stack of battery cells is closed at the end sides by a separating layer respectively.

[0028] In particular, with regard to the varying distances of the separating layers and the resulting mechanical loads, especially the equalization of the surface tension of the battery cell housings, it has been shown that the specific layout of the separating layers is advantageously determined by simulation, i.e., by a simulation method, in order to find the best possible layout, which optimally distributes the available separating layers for the given structural space constraints, such that the mechanical loads, especially preferably the surface tension, of the individual battery cells on the stack of battery cells and especially on the surface of the corresponding battery cell housings are minimized and homogenized over as long a service life as possible. The simulation is preferably implemented by a program included in a computer program product and executed on a computer.

[0029] Accordingly, in a preferred design, the layout of the separation layer is the result of a simulation, which is performed especially on a computer. During the simulation, the swelling or movement characteristics of the battery cell stack are simulated and the mechanical loads are determined hereby for each battery cell over a predefined service life, in particular preferably the surface tension of the battery cell housing of the battery cell. The mechanical loads are expediently determined locally and differentially, i.e. especially depending on the position on the respective battery cell housing. Similar to the expression "swelling or movement", the expression "swelling or movement characteristics" is understood as "swelling and / or movement characteristics". The service life is measured, for example, in terms of time or number of cycles. Here, the mechanical load, as described above, is preferably the surface tension of the battery cell housing. Furthermore, during the simulation, the mechanical loads for different layouts of the separation layer are determined and, as a result, the layout is selected for which the mechanical load meets the minimization criterion. The simulation thus simulates different layouts with the aim of finding the layout that results in the lowest mechanical load for the individual battery cells over the predefined service life. The simulation generally has two parts, namely on the one hand the simulation of the dynamic characteristics of the battery cell stack, more precisely the swelling or movement characteristics and the mechanical loads occurring hereby on all individual battery cells, and on the other hand the evaluation of the different layouts and the selection of one of the layouts according to a predefined criterion, here the minimization criterion. The simulation especially includes strength and deformation studies. Here, the so-called finite element method, abbreviated as "FEM", is particularly suitable, such that the simulation is preferably an FEM simulation and the program is accordingly an FEM program that performs the FEM simulation.

[0030] The basic advantage of the simulation is especially that the layout of the separation layer in the battery cell stack that optimally and particularly effectively utilizes the structural space is determined by the simulation. The simulation is especially characterized in that, by optimizing the layout of the separation layer in the battery cell stack, the mechanical loads, in particular the surface tension, are minimized over a predefined service life. This minimization is expressed, for example, in that, over the service life, the mechanical surface tension and the local movement are minimized and the local forces are homogenized. This results in a special layout that is characteristically irregular. The irregular layout of the separation layer is also a directly recognizable design feature of the battery cell module. It is clear here that the specific layout depends on the basic structure of the battery cell module, especially its structural space limitations and the fixation between the individual elements and components, as well as the material characteristic values and material characteristic curves of the relevant materials.

[0031] Preferably, the swelling or movement characteristics of the battery cell stack are determined by a structural model, wherein the respective battery cell consists of at least one expandable solid and a casing that surrounds the solid and is movable relative thereto. The structural model is especially a three-dimensional model of the entire battery cell module and thus also takes into account its casing. The individual battery cells are modeled by at least one expandable solid and a casing that is movable relative thereto.

[0032] An inflatable solid-simulating electrode and an active material that expands during its service life. The housing simulates the battery cell housing. Optionally, individual battery cells are simulated in more detail. In addition to the battery cells, a separator layer is also simulated, and optionally other elements or components of the battery cell module are also simulated when necessary. Suitably, the bonding between the battery cells, the housing, and / or the separator layer, such as the bonding in the form of the thermal paste described above, is also simulated and thus considered as part of the structural model.

[0033] Regarding the structural model, a favorable design for the method of manufacturing a battery cell module is obtained. The method has a first step in which the structural model is created, and the method also has a second step in which the structural model is calibrated and parameterized with material characteristic values and material characteristic curves. In the first step, the structural model of the battery cell module is created through its elements and components, especially the bonding, for use in the simulation. In the second step, the structural model is calibrated and parameterized for the simulation to simulate the dynamic characteristics of the battery cell module, especially the expansion or movement of the battery cells in the battery cell stack. The suitable material characteristic values and material characteristic curves used in the simulation are usually mechanical characteristic values, especially, for example, the elastic modulus or the force / displacement curve of the corresponding element or component.

[0034] Preferably, the expansion or movement characteristics of the battery cell stack are determined through a mechanical battery cell model that describes the expansion characteristics of individual battery cells and is created by measuring real battery cells. It is particularly important here that individual battery cells are considered first in order to find a battery cell model for them, and then this battery cell model is used to simulate the expansion or movement characteristics of the battery cell stack because the battery cell stack is ultimately a combination of individual battery cells plus the separator layer. The complex simulation of the entire battery cell module is thus simplified in that the actual expansion characteristics of individual battery cells are used as the basis, which can be measured with significantly less effort and then also used for different layouts of the separator layer. The cell model is preferably generated through specific tests on individual battery cells by measuring the expansion characteristics of the battery cells, for example, within a predefined service life or over other time periods, and then inferring the expansion characteristics within the service life based on other time periods, for example. The actual measurement of the expansion characteristics is basically especially the calibration of the battery cell model for the simulation.

[0035] In the method of manufacturing a battery cell module, in the third step, the battery cell model determined as described above is implemented into the simulation. The third step is also used, like the first and second steps, to prepare for the actual simulation. The first, second, and third steps are therefore also each called an "initialization step" and together are called the "initialization" of the simulation.

[0036] The simulation of the swelling or movement characteristics is in particular the fourth step in the method of manufacturing a battery cell module, which follows the initialization. In the fourth step, the mechanical loads of the individual battery cells and in particular of the battery cell module are generally simulated at the battery cell module level. The mechanical load is preferably the surface tension of the battery cell housing, alternatively or additionally a force, swelling, movement, etc. The force is, for example, a force acting on the respective battery cell, for example in the stacking direction. The movement is, for example, the movement of the electrode stack (i.e., the electrodes and the active material) in the respective battery cell, in particular at least by solid modeling with respect to the housing cover, as described above.

[0037] In this method, appropriately, there is a fifth step after the fourth step, in which the mechanical loads of the currently simulated layout over the service life are determined based on the simulated swelling or movement characteristics, and in particular, the possible failure of the battery cell housing is preferably predicted. Here, for example, for pouch-type battery cells, the locally resolved series strength of the film is calculated based on the relative movement between the film and the electrode stack of the battery cell and taking into account the material properties of the film (i.e., the material characteristic values and / or the material characteristic curves), where the films are adhesively bonded to each other with a thermal paste if necessary. This can be appropriately transferred to other types of battery cells.

[0038] The method preferably includes an optimization process as part of the simulation, in which different layouts are simulated and compared with each other in order to then select the most suitable layout and assemble a battery cell stack composed of battery cells and separator layers according to this layout. The comparison of different layouts and the selection of one of the layouts are preferably carried out in the sixth step of the method of manufacturing a battery cell. Here, the mechanical loads for different layouts of the separator layer are determined and as a result, the layout whose mechanical load meets the minimization criterion is selected. Basically, two scenarios can be envisaged: either multiple layouts are simulated and compared and then the layout that best meets the minimization criterion is selected (relative minimization criterion), or different layouts are simulated successively until a layout that meets the minimization criterion is found (absolute minimization criterion). However, in any case, multiple layouts are to be simulated. Here, it is not important at first which order the simulated layouts are determined or confirmed. What is important first is only that multiple layouts are simulated and the determined mechanical loads are compared here to find the optimal layout.

[0039] The minimization criterion indicates which characteristic of the mechanical load, in particular preferably the surface tension, is considered favorable. Generally speaking, it is preferred that the mechanical loads on all battery cells are as uniform as possible, while local peaks, i.e., maximum values, are avoided as much as possible.

[0040] In a suitable design, the minimization criterion is that the mechanical load of the layout, especially the maximum value of the surface tension, is minimized. For a given layout, for this purpose, the mechanical load is preferably calculated position-resolvedly for each individual battery cell within a predefined service life, for example at the end of the service life, so that it can be said that a plurality of mechanical loads are calculated. Among them, the maximum value is determined (a parameter that is advantageous for the highest possible value, equivalently, the minimum value is determined; hereinafter, the term "maximum value" is used without limiting generality). This process is repeated for other layouts in order to calculate the maximum value for each layout. Now, these maximum values are compared with each other, and finally, the layout with the lowest maximum value is selected. Preferably, alternatively or additionally, this is done analogously for each individual battery cell, that is, the position-resolved mechanical load, especially the maximum value of the surface tension, is determined for each individual battery cell, and then it is minimized.

[0041] Alternatively or additionally, the minimization criterion suitably is that the dispersion (or called separation degree) of the mechanical load of the layout, especially the surface tension, is minimized. The dispersion is, for example, the difference between the maximum and minimum values of the mechanical load, the difference between the maximum and average values of the mechanical load, or the variance or a similar quantity of the mechanical load. Generally speaking, the dispersion is preferably a measure of the uniformity of the mechanical load. For a given layout, the mechanical load is preferably calculated position-resolvedly for each individual battery cell within a predefined service life, for example at the end of the service life, so that it can be said that a plurality of mechanical loads are calculated. Thereby, the dispersion is determined. This process is repeated for other layouts in order to calculate the dispersion for each layout. Now, these dispersions are compared with each other, and finally, the layout with the lowest dispersion is selected.

[0042] In addition to the above two minimization criteria, other minimization criteria can basically also be conceived and are suitable.

[0043] In addition to the layout of the separation layer, in a suitable design, one or more of the following parameters, that is, the design parameters of the battery cell stack, also change: the number of separation layers, the thickness of the separation layer, the material of the separation layer, the material properties of the separation layer, such as its compressibility, stiffness, or its elastic modulus. Basically, it is advantageous to optimize the battery cell stack through one or more of these parameters while keeping the layout unchanged. The layout and the mentioned parameters are collectively referred to as the design of the separation layer because they show how to design and thus construct the separation layer.

[0044] The fourth, fifth, and sixth steps are especially formed by the aforementioned simulation and are therefore also called "simulation steps", or simply "simulation" for short.

[0045] In addition to the six steps (i.e., initialization and simulation) of the method described so far, the first and most important step is the seventh step, in which the battery cells and the separator layer are assembled into a battery cell stack such that an irregular layout is produced for the separator layer in the stacking direction, i.e., preferably a layout previously selected by means of a corresponding simulation. Thus, in the method for manufacturing a battery cell module, as described above, the battery cells and the separator layer are assembled into a battery cell stack such that an irregular layout is produced for the separator layer in the stacking direction.

[0046] The simulation is suitably carried out by means of a program executed on a computer. Accordingly, a computer program product according to the invention (i.e., a file or data carrier) comprises an executable program which, when installed on a computer, carries out the following steps: First, as described above, simulate the swelling or movement characteristics of the battery cell stack of the battery cell module and, in so doing, determine the mechanical load for each battery cell over a predefined service life, in particular the surface tension of the battery cell housing of the battery cell. Second, determine the mechanical load for different layouts or general designs of the separator layer and, as a result, select the layout or general design for which the mechanical load meets a minimization criterion. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Embodiments of the invention will be further described below with reference to the drawings. There are schematically:

[0048] Figure 1 showing a battery cell module,

[0049] Figure 2 shown in a cross-sectional view Figure 1 of the battery cell module,

[0050] Figure 3 shown in a cross-sectional view Figure 1 of a variant design of the battery cell module,

[0051] Figure 4 showing Figure 1 the battery cells of the battery cell module,

[0052] Figure 5 showing Figure 2 the battery cell module with regularly arranged separator layers,

[0053] Figure 6 showing a flow chart of a method for manufacturing a battery cell module,

[0054] Figure 7 shown in a cross-sectional view Figure 1 of a further variant design of the battery cell module,

[0055] Figure 8 shown in a cross-sectional view Figure 1Further variant designs of the battery cell module,

[0056] Figure 9 are shown in a cross-sectional view Figure 1 Further variant designs of the battery cell module,

[0057] Figure 10 are shown in a cross-sectional view Figure 1 Further variant designs of the battery cell module. Detailed Description

[0058] Figure 1 shows a perspective view of an embodiment for the battery cell module 2. The battery cell module 2 has at least one battery cell stack 4 and at least one housing 6, and the battery cell stack 4 is arranged in the housing. In Figure 1 a part of the housing 6 is removed, so that the battery cell stack 4 can be seen. Figure 2 and Figure 3 show two variants of the battery cell module 2 in cross-sectional views respectively. It can be clearly seen that the battery cell stack 4 has a plurality of battery cells 8 and a plurality of separation layers 10, which are stacked adjacent to each other in the stacking direction S. The separation layers 10 are designed to deform in the case of expansion or movement of one or more battery cells 8, and in particular absorb forces and movements here. Figure 4 shows a single battery cell 8 in a perspective view, and the possible expansion or movement of the battery cell 8 is indicated by an arrow here. The expansion or movement of the battery cell 8 is formed during aging, for example, due to the repeated discharging and charging of the battery cell 8 during the regular use of the battery cell module 2 or only when the battery cell module 2 is stored. The expansion or movement is mostly in the stacking direction S here, but not necessarily only in the stacking direction S.

[0059] From Figure 2 , Figure 3 and Figures 7 to 10 it can be seen that the battery cells 8 and the separation layers 10 are assembled into the battery cell stack 4 such that an irregular layout AN is produced for the separation layers 10 in the stacking direction S. Each separation layer 10 and each battery cell 8 are arranged at corresponding positions in the battery cell stack 4 in order to form a definite sequence or a definite pattern of the battery cells 8 and the separation layers 10. The term "irregular layout" is understood to mean that the separation layers 10 are not regularly distributed along the battery cell stack 4, but the distance A of the separation layers 10 observed in the stacking direction S is variable, such that the number of battery cells 8 arranged between two successive separation layers 10 is variable. For comparison, Figure 5 shows a battery cell module 2 not in accordance with the present invention, having a regular arrangement of the separation layers 10. The term "pattern" or "sequence" can also be used instead of the term "layout".

[0060] The corresponding separating layer 10 is also referred to as a "compression pad" or "cushion pad" and is substantially compressible, here made of a compressible material such as foam for the separating layer 10. Preferably, the separating layer 10 is made of a solid material with corresponding pores, air gaps or the like to form a foam, for example similar to a sponge. Alternatively, other materials and designs are also suitable as the separating layer 10, such as a so-called gel pad, which is made of gel. The separating layer 10 occupies a volume in the battery cell stack 4, which volume is gradually occupied by the expansion or movement of the battery cells 8 during the service life of the battery cell module 2. Here, conversely, the separating layer 10 is pressed together and compressed. Thus, the separating layer 10 absorbs mechanical loads B to a certain extent without thereby damaging the battery cells 8 and thus serves as a so-called sacrificial layer. Due to the principle, the ability of the separating layer 10 to absorb mechanical loads B is limited.

[0061] Each battery cell 8 has a battery cell housing 12, in which two electrodes 14 are arranged, namely a negative electrode and a positive electrode 14 respectively, and an active material 16 is also arranged. Here, only a battery cell 8 with two electrodes 14 is schematically shown, but it is also a feasible design that more than two electrodes 14 with corresponding active materials 16 are stacked or wound in a single battery cell 8. The electrodes 14 and the active material 16 are collectively referred to as an electrode stack. The active material 16 undergoes electrochemical degradation with continuous use and thus expands over time, causing the battery cell housing 12 to expand and deform accordingly, as Figure 4 shown. Due to the housing 6 of the battery cell module 2, the structural space for accommodating the battery cells 8 is correspondingly limited and their expansion or movement can also only be limited. In addition, the battery cells 8 are provided with a thermal paste 18 at least in the illustrated embodiment, and the thermal paste also makes thermal contact with the housing 6. The thermal paste 18 also acts like an adhesive, i.e., it presents as bonding and on the one hand fixes the battery cells 8 to each other and on the other hand fixes the battery cells 8 to the housing 6. The expansion or movement of the battery cells 8 usually results in relative movement between the active material 16 of the battery cells 8 and their battery cell housings 12.

[0062] It has been recognized that the expansion or movement of the battery cells 8 in the battery cell stack 4 is not necessarily evenly distributed over the battery cell stack 4, but varies greatly locally and correspondingly results in large differences in mechanical loads B, especially in the surface tension of the battery cell housing 12. On this basis, the separating layer 10 is thus arranged such that the local relative movement between the battery cell housing 12 and the corresponding active material 16 is minimized and the local forces are homogenized accordingly. Thus, correspondingly, the separating layer 10 is arranged irregularly distributed along the stacking direction S here and thus has an irregular layout AN. In the separating layer 10, as Figure 5A danger in the regular arrangement shown is that one cell 8 experiences a mechanical load B above the average, while the mechanical load B on the other cells 8 is small compared to this. The separation layer 10 near this heavily loaded cell 8 is quickly depleted, i.e., compressed, while the other separation layers 10 are compressed less or not at all. Thus, the separation layers 10 are arranged here exactly as required to achieve the most uniform distribution of the mechanical load B and at the same time save as much structural space as possible.

[0063] On the one hand in Figure 2 and Figure 6 in the design solution, and on the other hand in Figure 3 and Figures 7 to 10 the cell stack 4 has 12 and 24 cells 8 and only 5 separation layers 10 respectively. However, other quantity ratios are also suitable. The cell module 2 has one or more such cell stacks 4. A single cell stack 4 extends here from one end 20 of the housing 6 of the cell module 2 to the opposite end 22 of the housing 6. If there are multiple cell stacks 4, these cell stacks are arranged adjacent to each other, for example, laterally, i.e., in a direction perpendicular to the stacking direction S.

[0064] The corresponding separation layer 10 has a thickness d1, which is between 10% and 30% of the thickness d2 of the corresponding cell 8. Here, the corresponding thicknesses d1, d2 are measured in the stacking direction S. In addition, design principles with thickness ratios outside the above range are also suitable in principle.

[0065] In the embodiment shown here, the cells 8 are each designed as so-called pouch cells. However, the following description can also be advantageously applied similarly to other types of cells 8, such as prismatic cells or cylindrical cells, because they also show problems of expansion or movement. The pouch cell 8 is schematically shown in Figure 4 and is generally flat, where the thickness d2 of the pouch cell 8 extends in the stacking direction and is also the smallest dimension of the pouch cell 8. Usually, the thickness d2 of the pouch cell 8 is smaller than its height and width by one or more orders of magnitude.

[0066] As described above, the cells 8 are connected to the housing 6 here by a thermal paste 18. The thermal paste 18 also fixes the cells 8 to each other on the one hand and fixes the cells 8 to the housing 6 on the other hand. The thermal paste 18 is arranged here only on one side of the cell stack 4, for example, on the bottom side 24, while the opposite side of the cell stack 4, i.e., for example, the top side 26, does not have the thermal paste 18. The separation layer 10 is also fixed in the cell stack 4 by the thermal paste 18 here.

[0067] In the case of the pouch-shaped battery cell 8, the battery cell housing 12 is typically a pouch made of a film. For the film, there is a risk of damage when the battery cell 8 expands or moves, for example, cracks are formed or punctured by adjacent components. The fixing of the film in a sectional manner, for example, by fixing the thermal paste 18 on one side, may cause the movement of the film relative to the electrode 14 and the active material 16 in the film, with a corresponding risk of damage.

[0068] In Figure 2 and Figure 3 In the embodiments of, the layout AN of the separating layer 10 is such that every two successive separating layers 10 along the stacking direction S are spaced apart by a distance A, and this distance increases in the direction towards the center M of the battery cell stack 4. Similar to the increase in the distance A, when the thickness d2 of the battery cell 8 remains unchanged, the number of battery cells 8 between two separating layers 10 increases in the direction towards the center M. This irregular layout AN is based on the knowledge that towards the ends E1, E2 of the battery cell stack 4, that is, away from the center M, the mechanical load B on the individual battery cells 8, in particular the mechanical load in the form of a compressive force acting on the battery cell 8, decreases. Therefore, the battery cell stack 4 has a correspondingly lower density of separating layers 10 in the direction towards the center M, so that structural space is saved. In summary, in particular, the mechanical load B in the form of surface tension is balanced with each other, that is, homogenized, so that each battery cell 8 experiences as much as possible the same mechanical load B, in particular in the form of surface tension.

[0069] However, it is already known here that in some cases, the opposite design is advantageous. Whether the distance A increases or decreases depends here on the stiffness present at the end sides of the battery cell stack 4, that is, on the stiffness of the housing 6 itself or the stiffness of the ends E1, E2 of the battery cell stack 4.

[0070] Accordingly, in Figure 7 and Figure 8 In the variant of, the layout AN of the separating layer 10 is such that every two successive separating layers 10 are spaced apart by a distance A, and this distance decreases in the direction towards the center M of the battery cell stack 4. Now, the distance A decreases in the direction towards the center, instead of increasing in the direction towards the center M as in Figure 2 and Figure 4 and increasing in the direction towards the center M. Advantageously, a soft material is arranged at the ends E1, E2 of the battery cell stack 4 along the stacking direction S, which is either the last layer of the battery cell stack 4 or part of the housing 6 that supports the battery cell stack 4 on the end side. The housing 6 is made of metal, for example, aluminum, and thus has a high stiffness. Then, the last layer of the battery cell stack 4 or the part of the housing 6 in contact with the ends E1, E2 of the battery cell stack 4 is made of a material with a lower stiffness compared thereto, for example, aerogel.

[0071] The "stiffness" of a material is generally understood to refer in particular to its expansion stiffness, shear stiffness, bending stiffness or torsional stiffness, or a combination thereof.

[0072] In Figure 7 and Figure 8 In the embodiments of, the separation layer 10 of the battery cell stack 4 forms the last layer, even at both ends E1, E2 of the battery cell stack 4. These separation layers 10 are made here of a material having a lower stiffness than the housing 6, i.e. than the material of which the housing 6 is made.

[0073] Figure 9 and Figure 10 and respectively show further embodiments in which at least two separation layers (10) have different stiffnesses. In the example shown here, the separation layers 10 each have a stiffness that increases in the direction of the center M of the battery cell stack 4. The separation layers 10 thus have different stiffnesses and increase in the direction of the center M of the battery cell stack 4 when viewed in the stacking direction S. In a further example not shown here, the stiffness decreases in the direction of the center M or the different stiffnesses are distributed differently. For example, the stiffness is set by changing the thickness d1 and / or the material of the separation layer 10.

[0074] The distance A between two successive separation layers 10 is measured, for example, in terms of the number of battery cells 8, where all the battery cells 8 have the same thickness d2. In a design according to Figure 2 with 12 battery cells and 5 separation layers, one of the separation layers 10 is arranged centrally in the battery cell stack 4, and two adjacent separation layers 10 are arranged at a distance A of 3 battery cells 8 therefrom. Then there is an alternation of 1 battery cell 8 and 1 separation layer 10, such that the battery cell stack 4 ends with battery cells 8 at both ends. The layout of the battery cells 8 and the separation layers 10 from one end E1 to the other end E2 of the battery cell stack 4 is: 1 battery cell, 1 separation layer, 1 battery cell, 1 separation layer, 4 battery cells, 1 separation layer (center), 4 battery cells, 1 separation layer, 1 battery cell, 1 separation layer, 1 battery cell. For a battery cell stack 4 with 24 battery cells 8 and 5 separation layers 10, the number of battery cells 8 is doubled, for example as Figure 3 shown: 3 battery cells, 1 separation layer, 3 battery cells, 1 separation layer, 6 battery cells, 1 separation layer (center), 6 battery cells, 1 separation layer, 3 battery cells, 1 separation layer, 3 battery cells. The layout AN can be summarized as a layout AN with 5 separation layers 10, where the distance A of the central separation layer 10 from its two adjacent separation layers 10 is two to four times the distance A between the two outermost separation layers 10. In contrast, in a regular layout, the distance A between two separation layers 10 is always the same, for example as Figure 5In the case of 12 battery cells 8, the distance A is 3 battery cells 8, wherein the battery cell stack 4 is enclosed at the end sides by a separation layer 10 respectively. Contrary to Figure 5 the design of Figure 2 and Figure 3 the battery cell stack 4 is enclosed at the two ends E1, E2 by battery cells 8 instead of the separation layer 10 respectively. However, this design with the separation layer 10 at the end sides is also basically feasible and advantageous.

[0075] In the design according to Figure 7 which also has 12 battery cells and 5 separation layers 10, one of the separation layers 10 is arranged in the middle of the battery cell stack 4. Contrary to Figure 2 and Figure 3 two adjacent separation layers 10 are arranged at a distance A of 2 battery cells 8 relative thereto. Then there are 4 battery cells, followed by another separation layer 10 as the last layer of the battery cell stack 4, so the battery cell stack ends with the separation layer 10 at the end sides respectively. The layout of the battery cells 8 and the separation layers 10 from one end E1 to the other end E2 of the battery cell stack 4 is: 1 separation layer, 4 battery cells, 1 separation layer, 2 battery cells, 1 separation layer (center), 2 battery cells, 1 separation layer, 4 battery cells, 1 separation layer. For Figure 7 the battery cell stack 4 with 24 battery cells 8 and 5 separation layers 10 in Figure 8 the number of battery cells 8 is generally doubled, for example as shown in Figure 8 : 1 separation layer, 9 battery cells, 1 separation layer, 3 battery cells, 1 separation layer (center), 3 battery cells, 1 separation layer, 9 battery cells, 1 separation layer.

[0076] As described above, Figure 9 and Figure 10 respectively show embodiments with separation layers of different stiffnesses, which are represented here by the filling of the separation layer 10, wherein the same filling also represents the same stiffness. Therefore, overall there are two different stiffnesses in Figure 9 and Figure 10 i.e., the two separation layers 10 farthest from the center M have lower stiffness than the other separation layers 10. In Figure 10 these two separation layers 10 with lower stiffness are also arranged at the end sides and are thus the last layers of the battery cell stack 4. In addition to the distribution of different stiffnesses clearly shown here, other distributions are also feasible and suitable.

[0077] In particular, with regard to the varying distance A of the separating layer 10 and the resulting mechanical loads B, in particular the equalization of surface tension, the specific layout AN of the separating layer 10 is advantageously determined by simulation, i.e., by means of a simulation method, in order to find the best possible layout AN, which optimally distributes the available separating layer 10 for the given structural space constraints such that the mechanical loads B on the individual battery cells 8 on the battery cell stack 4 and in particular on the corresponding surfaces of the battery cell housings 12 are equalized over the longest possible service life. This simulation is implemented here by a program contained in a computer program product and executed on a computer not explicitly shown.

[0078] During the simulation, the expansion or movement characteristics of the battery cell stack 4 are simulated and the mechanical loads B are determined here for each battery cell 8 over a predefined service life, here namely the surface tension of the corresponding battery cell housing 12. The service life is measured, for example, in terms of time or number of cycles. Furthermore, during the simulation the mechanical loads B are determined for different layouts AN of the separating layer 10, and as a result the layout AN is selected for which the mechanical load B meets the minimization criterion K. The simulation thus simulates different layouts AN with the aim of finding the layout AN that results in the lowest mechanical load B for the individual battery cells 8 over the specified service life. The simulation generally has two parts, namely on the one hand the simulation of the dynamic characteristics of the battery cell stack 4, more precisely the expansion or movement characteristics and the mechanical loads occurring thereon on all individual battery cells 8, and on the other hand the evaluation of the different layouts AN and the selection of one of the layouts AN according to a predefined criterion, here namely the minimization criterion K. This simulation includes strength and deformation studies here and is thus a finite element analysis (FEM) simulation.

[0079] The best and particularly space-saving layout AN of the separating layer 10 in the battery cell stack 4 is determined by this simulation. This simulation is characterized here in that by optimizing the layout AN of the separating layer 10 in the battery cell stack 4, the mechanical load B, in particular the surface tension of the battery cell housing 12, is minimized over a predefined service life. This minimization is expressed in that, over the service life, the mechanical surface tension and the local movement are minimized and the local forces are equalized. This results, for example Figure 2 and Figure 3 in the special layout AN shown, which is characteristically irregular.

[0080] Here, the simulation is part of the method for manufacturing the battery cell module 2. An embodiment for this method is shown in Figure 6 in the form of a flow chart with seven steps S1 - S7.

[0081] The expansion or movement characteristics of the battery cell stack 4 are determined hereby by means of the structural model 28, wherein the respective battery cell 8 consists of an expandable solid 30 and a casing 32 which surrounds the solid 30 and is movable relative thereto. The structural model 28 hereby is a three-dimensional model of the entire battery cell module 2 and thus also takes into account its housing 6. The individual battery cell 8 is modeled by at least one expandable solid 30 and a casing 32 which is movable relative thereto. As Figure 4 shown, the expandable solid 30 simulates the electrode stack, i.e., the electrodes 14 and the active material 16, which expand during the service life. The casing 32 simulates the battery cell housing 12. Optionally, the individual battery cell 8 is modeled in more detail. In addition to the battery cell 8, the separating layer 10 is also modeled, and optionally other elements or components of the battery cell module 2 are also modeled if necessary. Herein, the bonding between the battery cell 8, the housing 6 and / or the separating layer 10, wherein the bonding in the form of the thermal paste 18 is also modeled and thus taken into account as part of the structural model 28.

[0082] Regarding the structural model 28, the method has a first step S1, in which the structural model 28 is created, and the method also has a second step S2, in which the structural model 28 is calibrated and parameterized with the material characteristic value M1 and the material characteristic curve M2. In the first step S1, the structural model 28 of the battery cell module 2 is created by means of its elements and components for use in the simulation. In the second step S2, the structural model 28 is calibrated and parameterized for the simulation in order to simulate the dynamic characteristics of the battery cell module 2, in particular the expansion or movement of the battery cells 8 in the battery cell stack 4. The material characteristic value M1 and the material characteristic curve M2 used in the simulation are generally mechanical characteristic values, in particular, for example, the elastic modulus or the force / displacement curve of the respective element or the respective component.

[0083] Hereby, the expansion or movement characteristics of the battery cell stack 4 are also determined by means of the mechanical battery cell model 34, which, for example, describes the expansion characteristics of the individual battery cell 8 as shown in Figure 4 and is created by measuring the real battery cell 8. Herein, the individual battery cell 8 is considered first in order to find the battery cell model 34 for it, and then the battery cell model 34 is used to simulate the expansion or movement characteristics of the battery cell stack 4.

[0084] In the Figure 6 shown method, implementing the expansion characteristics into the simulation according to the battery cell model 34, specifically into the structural module 28, is the third step S3, which, like the first and second steps S1, S2, is used to prepare for the actual simulation. The first, second and third steps S1, S2, S3 are therefore also each referred to as an "initialization step" and together as the "initialization" of the simulation.

[0085] The simulation of the expansion or movement characteristics is carried out according to Figure 6In the method, it is the fourth step S4, which comes after initialization. In the fourth step S4, the mechanical loads B of the individual battery cells 8 and the battery cell module 2 are generally simulated at the battery cell module level. Here, for example, surface tension, forces, expansion, movement, etc. are simulated. The forces are, for example, forces acting on the respective battery cells 8, for example in the stacking direction S. The movement is, for example, the movement of the electrode stack (i.e., the electrodes 14 and the active material 16 and the solid 30 in the battery cell model 34) in the respective battery cell 8, which is modeled at least by the solid 30 moving relative to the housing 32.

[0086] In the method according to Figure 6 In this method, after the fourth step S4, there is a fifth step S5, in which the mechanical load B of the currently simulated layout AN over the service life is determined based on the simulated expansion or movement characteristics. Here, for example, for pouch-shaped battery cells 8, the locally resolved series strength of the film is calculated based on the relative movement between the film and the electrode stack of the battery cell 8 and taking into account the material properties of the film (i.e., the material characteristic values M1 and / or the material characteristic curve M1), where the films are optionally additionally bonded to each other with a thermal paste 18.

[0087] As part of the simulation, this method includes an optimization process in which different layouts AN are simulated and compared with each other in order to then select the most suitable layout AN and assemble the battery cell stack 4 composed of the battery cells 8 and the separator layer 10 according to this layout AN. The comparison of the different layouts AN and the selection of one of the layouts AN are carried out here in the sixth step S6 of the method. Here, the mechanical load B is determined for different layouts AN of the separator layer 10, here namely the surface tension of the respective battery cell housing 12, which is Figure 6 represented by the arrow from the sixth step S6 back to the first step S1. As a result, the layout AN for which the mechanical load B meets the minimization criterion K is selected. Basically, two scenarios can be envisaged here: either multiple layouts AN are simulated and compared and then the layout that best meets the minimization criterion K is selected (relative to the minimization criterion K), or different layouts AN are simulated successively until a layout AN that meets the minimization criterion K is found (absolute minimization criterion K). However, in any case, multiple layouts AN are to be simulated. Here, it is not important at first which order the simulated layouts AN are determined or confirmed. The only important thing at first is to simulate multiple layouts AN and compare the determined mechanical loads B here in order to find the best layout AN.

[0088] The minimization criterion K indicates which characteristic of the mechanical load B is considered favorable. Generally speaking, it is preferred to have as uniform a mechanical load B as possible in all battery cells 8, here namely first of all a uniform distribution of the surface tension, while local peaks, i.e., the maximum values of the surface tension, should be avoided as much as possible.

[0089] In one design, the minimization criterion K is that the maximum value of the mechanical load B of the layout AN is minimized. For a given layout AN, for this purpose, the mechanical load B is calculated position-resolved for each individual cell 8 over a predefined service life, for example at the end of the service life, thereby calculating a plurality of mechanical loads B, in this case the surface tension. The maximum value is thus determined. This process is repeated for other layouts AN in order to calculate the maximum value for each layout AN. Now these maximum values are compared with each other, and finally the layout AN with the lowest maximum value is selected.

[0090] Alternatively or additionally, the minimization criterion K is that the spread of the mechanical load B of the layout AN is minimized. The spread is, for example, the difference between the maximum and minimum values of the mechanical load B, the difference between the maximum value and the average value of the mechanical load B, or the variance or a similar quantity of the mechanical load B. For a given layout AN, the mechanical load B is calculated position-resolved for each individual cell 8 over a predefined service life, for example at the end of the service life, thereby calculating a plurality of mechanical loads B. The spread is thus determined. This process is repeated for other layouts AN in order to calculate the spread for each layout AN. Now these spreads are compared with each other, and finally the layout AN with the lowest spread is selected.

[0091] In addition to the above two minimization criteria K, other minimization criteria are basically also conceivable and suitable.

[0092] In addition to the layout of the separating layer 10, in a design not explicitly shown, one or more of the following parameters are also changed: the number of separating layers 10, the thickness d1 of the separating layer 10, the material properties of the separating layer 10, such as its compressibility or its modulus of elasticity. Basically, it is possible to optimize the cell stack 4 by one or more of these parameters while the layout AN remains unchanged.

[0093] The fourth, fifth, and sixth steps S4, S5, S6 are formed by the simulation described above in Figure 6 the embodiment and are therefore also referred to as "simulation steps", or simply as "simulation".

[0094] In addition to the six steps S1–S6 (i.e., initialization and simulation) of the method described so far, the most important step is the seventh step S7, in which the cells 8 and the separating layer 10 are assembled into the cell stack 4 such that an irregular layout AN is produced for the separating layer 10 in the stacking direction S, i.e., the layout AN previously selected by simulation. Thus, in the method for manufacturing the cell module 2, as described above, the cells 8 and the separating layer 10 are assembled into the cell stack 4 such that an irregular layout AN is produced for the separating layer 10 in the stacking direction S.

[0095] List of reference numerals:

[0096] 2 Battery cell module

[0097] 4 Battery cell stack

[0098] 6 Housing

[0099] 8 Battery cell

[0100] 10 Separation layer

[0101] 12 Battery cell housing

[0102] 14 Electrode

[0103] 16 Active material

[0104] 18 Thermal paste

[0105] 20 End (of the housing)

[0106] 22 Opposite end (of the housing)

[0107] 24 Bottom side (of the battery cell stack)

[0108] 26 Top side (of the battery cell stack)

[0109] 28 Structural model

[0110] 30 Solid

[0111] 32 Shell cover

[0112] 34 Mechanical battery cell model

[0113] A Spacing

[0114] AN Irregular layout

[0115] B Mechanical load

[0116] d1 Thickness (of the separation layer)

[0117] d2 Thickness (of the battery cell)

[0118] E1, E2 Ends (of the battery cell stack)

[0119] K Minimization criterion

[0120] M Center (of the battery cell stack)

[0121] M1 Material characteristic value

[0122] M2 Material characteristic curve

[0123] S Stacking direction

[0124] S1 First step

[0125] S2 Second step

[0126] S3 Third step

[0127] S4 Fourth step

[0128] S5 Fifth step

[0129] S6 Sixth step

[0130] S7 Seventh step

Claims

1. A battery cell module (2) having at least one battery cell stack (4) and at least one housing (6), the battery cell stack (4) being arranged in the housing, - wherein, The battery cell stack (4) has a plurality of battery cells (8) and a plurality of separating layers (10), which are stacked adjacent to one another in the stacking direction (S). - wherein the separating layer (10) is designed to deform in the event of expansion or movement of one or more battery cells (8). - wherein the battery cells (8) and the separating layers (10) are assembled into a battery cell stack (4) such that an irregular layout (AN) is formed for the separating layers (10) in the stacking direction (S). - wherein the layout (AN) of the separating layer (10) is the result of a simulation in which - the expansion or movement characteristics of the battery cell stack (4) are simulated and the mechanical loads (B) are determined for each battery cell (8) over a predefined service life. - the mechanical loads (B) for different layouts (AN) of the separating layer (10) are determined and, as a result, the layout (AN) is selected for which the mechanical load (B) meets a minimization criterion (K).

2. The battery cell module (2) according to claim 1, wherein, The battery cells (8) are each configured as pouch cells or prismatic cells.

3. The battery cell module (2) according to claim 1, wherein, The battery cells (8) are connected to the housing (6) by means of a thermal paste (18).

4. The battery cell module (2) according to claim 1 or 3, wherein, The layout (AN) of the separating layer (10) is such that each two successive separating layers (10) are spaced apart by a distance (A) which increases in the direction of the center (M) of the battery cell stack (4).

5. The battery cell module (2) according to claim 1 or 3, wherein, The layout (AN) of the separating layer (10) is such that each two successive separating layers (10) are spaced apart by a distance (A) which decreases in the direction of the center (M) of the battery cell stack (4).

6. The battery cell module (2) according to claim 1 or 3, wherein, The battery cell stack (4) has separating layers (10) at its ends, which are made of a material having a lower stiffness than the housing (6).

7. The battery cell module (2) according to claim 1 or 3, wherein, At least two of the plurality of separating layers (10) have different stiffnesses.

8. The battery cell module (2) according to claim 1 or 3, wherein, The mechanical load (B) is the surface tension of the battery cell housing (12) of the battery cell (8).

9. The battery cell module (2) according to claim 1 or 3, wherein, The expansion or movement characteristics of the battery cell stack (4) are determined by means of a structural model (28) in which the respective battery cell (8) consists of at least one expandable solid (30) and a casing (32) which surrounds the solid (30) and is movable relative thereto.

10. The battery cell module (2) according to claim 1 or 3, wherein, The expansion or movement characteristics of the battery cell stack (4) are determined by means of a mechanical battery cell model (34) which describes the expansion characteristics of an individual battery cell (8) and is created by measuring real battery cells (8).

11. The battery cell module (2) according to claim 1 or 3, wherein, The minimization criterion (K) is - the maximum value of the mechanical load (B) of the layout (AN) is minimal, or - the spread of the mechanical load (B) of the layout (AN) is minimal.

12. A method for manufacturing the battery cell module (2) according to claim 1, - wherein the battery cells (8) and the separating layer (10) are assembled into a battery cell stack (4) such that an irregular layout (AN) is formed for the separating layer (10) in the stacking direction (S).

13. A computer program product comprising an executable program which, when installed on a computer, performs the following steps: - simulating the swelling or movement characteristics of the battery cell stack (4) of the battery cell module (2) according to claim 1 and determining, in this case, the mechanical load (B) for each battery cell (8) over a predefined service life, - determining the mechanical load (B) for different layouts (AN) of the separating layer (10) and, as a result, selecting such a layout (AN) for which the mechanical load (B) meets a minimization criterion (K).

14. The computer program product according to claim 13, wherein, The mechanical load (B) is the surface tension of the battery cell housing (12) of the battery cell (8).

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