Electrical energy store for a motor vehicle

Abstract

The invention relates to an energy storage device (1) for storing electrical energy for a motor vehicle (14), comprising a plurality of stacked storage cells (3), preferably prismatic storage cells (3). A cell intermediate layer (2) is arranged between each two adjacent storage cells (3). The cell intermediate layer has a spacer (4) and a compression element (5), preferably a compression pad, wherein the spacer (4) has a greater thermal conductivity and a lower compressibility than the compression element (5). The compression element (5) is dimensioned and arranged relative to the spacer (4) in such a way that at least one side (6) of the spacer (4) facing one of the two adjacent storage cells (3) is completely covered by the compression element (5). The invention also relates to a motor vehicle (14) comprising such an energy storage device (1).

Description

[0001] Electrical energy storage for a motor vehicle

[0002] Description

[0003] The invention relates to an energy storage device for storing electrical energy for a motor vehicle, comprising several stacked storage cells and cell interlayers, each arranged between two adjacent storage cells. The invention further relates to a motor vehicle comprising such an energy storage device.

[0004] With the increasing demand for alternative drive systems, electric drives are becoming ever more important. The electrical energy storage systems used in vehicles are usually composed of several storage cells (also called battery cells or simply cells). These storage cells are typically integrated into cell modules.

[0005] Optimal integration of memory cells into cell modules is characterized by fulfilling the following requirements: reducing the risk of thermal runaway in one cell leading to thermal runaway in neighboring cells, improving the cell's swelling behavior to improve the lifetime of the memory cells, and improving the mechanical integration of the memory cells in the cell module to protect against mechanical weaknesses and enable tolerance compensation.

[0006] For example, damage mechanisms (e.g., short circuits due to accidents, vibrations, etc.) can cause individual storage cells to heat up so intensely that an unstoppable, highly exothermic reaction is initiated inside the affected cells, leading to further heating and destruction of the storage cell. This process is typically referred to as thermal runaway. If a large amount of heat energy is transferred to neighboring storage cells, the resulting temperature input can also cause adjacent, previously intact, storage cells to heat up so much that they too begin the thermal runaway process. In the worst-case scenario, this can result in a dangerous, chain-reaction-like combustion of the entire energy storage system with a massive release of heat.It is therefore important to design energy storage systems in such a way as to reduce the risk of thermal runaway in one cell causing thermal runaway in neighboring cells, thereby increasing operational reliability. Furthermore, it is known from practical experience that a storage cell develops internal pressure as it ages. This pressure causes the cell to bulge (so-called swelling). This generates a force on the cell assembly within the cell module. If the cells of a cell module are clamped between end plates, for example, the increase in volume leads to a pressure increase on the storage cells, which can negatively affect their lifespan. If the end plates in the cell module are not sufficiently rigid, they will deflect significantly. This causes the cells to shift geometrically within the module and potentially rupture. The counter-pressure on the cells can then decrease, resulting in a suboptimal pressure distribution within the cell module.The extent of cell aging is determined, among other things, by cell structure, cell chemistry, operating parameters, and the amount of external back pressure the cell experiences. Lifespan-optimized swelling can be achieved by generating the optimal back pressure for the specific combination of cell and operating parameters during cell integration.

[0007] Furthermore, optimal integration of the storage cells into cell modules is characterized by mechanical integration of the storage cells within the cell module, which protects mechanical weak points, such as weld seams in prismatic cells or sealing seams in pouch cells, from excessive stress as effectively as possible and allows for tolerance compensation when the cell modules are pressed together to size during production.

[0008] The approaches known from practice for integrating memory cells have the disadvantage that they do not sufficiently meet the aforementioned requirements, in particular they do not offer sufficient optimization of the requirements with regard to operational reliability and service life.

[0009] The invention is therefore based on the objective of providing an improved technology for energy storage devices for storing electrical energy, which also avoids, as far as possible, the disadvantages of previous solutions. In particular, it is an objective of the invention to provide an energy storage device for storing electrical energy that is characterized by improved fulfillment of the aforementioned requirements.

[0010] According to a general aspect of the present disclosure, an energy storage device for storing electrical energy for a motor vehicle is provided. The energy storage device can be a cell module and / or a battery cell stack module, or an energy storage device comprising at least one cell module and / or a battery cell stack module. The energy storage device includes several storage cells arranged in a stack. The storage cells can, for example, be configured as prismatic storage cells and / or pouch cells. An interlayer of cells is arranged between each pair of adjacent storage cells; that is, an interlayer of cells is arranged between each pair of storage cells arranged successively in the stacking direction.

[0011] The interlayer comprises a spacer and a compression element. The compression element can be, for example, a compression pad and / or a gel and / or aerogel. Compared to the compression element, the spacer has a higher thermal conductivity and lower compressibility. Furthermore, the compression element is dimensioned and positioned relative to the spacer such that at least one side of the spacer facing one of the two adjacent memory cells is completely covered by the compression element. In other words, to reduce the thermal coupling between adjacent memory cells, the compression element can be positioned completely behind the spacer to eliminate potential thermal bypasses to the neighboring cell via the spacer.

[0012] Advantageously, the storage cells can be securely fixed by the spacer and held at a desired distance, e.g., within a housing, so that the storage cells remain securely in their intended position even if their volume changes or due to vehicle vibrations. The compression element enables secure compression of the storage cells within the cell assembly and reliable absorption of pressure during cell swelling. Furthermore, the inventive design of the cell interlayer reduces the risk of thermal runaway in one cell causing thermal runaway in adjacent cells, since at least one side of the spacer facing one of the two adjacent storage cells is completely covered by the compression element.This prevents the thermal paths coupling the two memory cells from passing completely through the spacer (which has a higher thermal conductivity than the compression element). Instead, all these thermal paths are interrupted by the compression element, resulting in improved thermal decoupling of the two adjacent memory cells while ensuring secure fixation. For example, in the event of a thermal runaway, this can keep the neighboring cell 20-30 K cooler. It was previously established that at least one side of the spacer facing one of the two adjacent memory cells is completely covered by the compression element.Alternatively, or in addition, the compression element can be dimensioned and arranged relative to the spacer such that no heat path for the thermal coupling of two adjacent storage cells within the cell interlayer exists that runs completely through the spacer. This can be achieved, for example, by ensuring that the spacer does not run continuously from one storage cell to the other, but is completely interrupted by the compression element between the two storage cells. Preferably, all heat paths within the cell interlayer for the thermal coupling of two adjacent storage cells run section by section through the compression element and section by section through the spacer.

[0013] The interlayer may include, in addition to the compression element, other components, such as adhesive and / or protective films, which are preferably arranged between the compression element and the spacer and / or the storage cells. The interlayer preferably does not include a component that extends from one storage cell to another and has a higher thermal conductivity than the compression element.

[0014] The spacer is preferably designed to withstand mechanical stress under normal operating conditions and to maintain a minimum distance between the two battery cells. Normal operating conditions are understood to mean conditions under which the energy storage device is typically operated. Excessive stresses, for example due to an accident, are not included. The spacer can be designed as a single piece or in multiple parts.

[0015] The compression element is compressible as a result of an increase in the volume of at least one storage cell of the energy storage device. The compression element is preferably deformable, for example, compressible, so that it can deform to absorb mechanical loads when the storage cells expand in volume. In the area of ​​the spacer, the compression element can be pre-stressed, for example, already substantially compressed, so that the fixing effect of the spacer is not disrupted by the compression element. Since the compression element has a lower thermal conductivity than the spacer, heat transfer from one storage cell to another can be reduced, provided that the thermal paths coupling the two storage cells each pass at least partially through the compression element.

[0016] According to a preferred embodiment, the spacer rests directly on one of the two adjacent storage cells. On the other of the two adjacent storage cells, the spacer rests indirectly via the compression element. In other words, the spacer rests on one of the two adjacent storage cells, and the compression element rests on the other of the two adjacent storage cells. The compression element can be pre-tensioned in the area of ​​the spacer, e.g., compressed. In this way, the spacer provides secure fixation of the storage cells, while the compression element allows for volume changes in the storage cells. Simultaneously, no heat path coupling the two storage cells passes completely through the spacer, thus providing thermal decoupling of the two adjacent storage cells.Direct contact of the spacer with one of the two adjacent memory cells means that the spacer is essentially in direct contact with the memory cell. However, it is possible that, for example, an adhesive or an electrically insulating protective film may be placed between the memory cell and the spacer.

[0017] According to a further embodiment, the cell interlayer has an additional spacer, wherein the spacer rests directly on one of the two adjacent storage cells and the additional spacer rests directly on the other of the two adjacent storage cells. The compression element is arranged between the spacer and the additional spacer and in a central area between the two adjacent storage cells. In this way, a support element in the form of the spacer and the additional spacer can be arranged on both of the two adjacent storage cells, so that a particularly uniform support effect for both storage cells can be achieved.

[0018] The spacer and the additional spacer can be identical or different. The spacer can also be referred to as the first spacer and the additional spacer as the second spacer. The additional spacer can generally be designed according to any embodiment of the spacer. To avoid repetition, all embodiments of the spacer disclosed in this document shall also be considered disclosed and claimable, preferably claimed, for the additional spacer. According to a further embodiment, a side of the compression element facing the spacer completely covers the spacer. In this way, particularly good thermal decoupling of the memory cells can be achieved.

[0019] In another advantageous embodiment, the spacer is frame-shaped. The spacer forms a cavity into which the storage cells and / or the compression element can expand when the storage cells swell. This embodiment allows the storage cell to expand in a particularly safe manner. Depending on the design of the storage cell, its service life can be optimized by minimizing back pressure on the storage cell while minimizing volume expansion. Similarly, the space into which the storage cell and / or the compression element can expand can improve the service life of suitable storage cells.

[0020] In a further advantageous embodiment, the spacer can extend in a rectangular shape around an outer area of ​​a side surface of the storage cells in a plane that runs essentially parallel to the adjacent storage cells. Typically, the volume of the storage cell is smaller in the outer area of ​​the side surface than in the central area. Therefore, a circumferential arrangement of the spacer along the outer area can provide particularly secure and uniform fixation of the storage cell without unnecessarily restricting its volume expansion.

[0021] The spacer can be made in one piece or in multiple parts, with each part preferably adjoining at least one other part to form a closed, essentially rectangular ring. The outer edges of the spacer can be flush with the outer edges of the memory cells, or at least partially spaced from the outer edge of the memory cells.

[0022] According to a further advantageous embodiment, the spacer can have rectangular and / or triangular sections in a plane running substantially parallel to the adjacent storage cells. Alternatively, or in addition, the spacer can have an irregular height and / or width in a plane substantially parallel to the adjacent storage cells. Likewise, the spacer, for example in the case of a rectangular frame, can have a free space that need not be rectangular, but rather has rectangular and / or triangular recesses. In this way, the support effect of the spacer can be ideally adapted to the type of storage cell or to the individual spatial volume of the storage cell.

[0023] According to a further embodiment, the spacer has sections that extend along an upper and lower edge of a side surface of at least one of the two adjacent memory cells. This enables secure fixing of the memory cells without unnecessarily restricting their volume expansion.

[0024] In a preferred embodiment, the sections can be strip-shaped, triangular, comb-shaped, or rib-shaped. Additionally or alternatively, the sections can have a wave-like or zigzag pattern. Furthermore, the sections can also have a perforated structure. This allows for material savings in the spacer without unduly compromising its support function. Saving spacer material can advantageously result in both weight reduction and a decrease in potential heat conduction between the two adjacent storage cells. The thermal decoupling of the two storage cells can thus be improved.

[0025] In another embodiment, the thermal conductivity of the compression element is in the range of 0.02 W / K to 0.03 W / K. The thermal conductivity of the spacer can be in the range of 0.1 W / K to 0.3 W / K. Furthermore, the thermal conductivity of the compression element can be five times, preferably at least eight times, lower than the thermal conductivity of the spacer. In this way, effective thermal decoupling of the two adjacent storage cells can be achieved.

[0026] According to another embodiment, the spacer is made of a plastic or rubber material, preferably a thermoplastic or polypropylene material and / or a thermally extruded or injection-molded plastic. In this way, reliable support from the spacer can be achieved while maintaining low weight and low thermal conductivity.

[0027] Preferably, the compression element can be a compression pad, preferably comprising a gel and / or aerogel. The gel and / or aerogel can be enclosed by a flexible shell. In this way, a compression element with compression properties adapted to the respective type of memory cell and particularly low thermal conductivity can be created.

[0028] In a further embodiment, the spacer for supporting a weld seam running between a cell can and a cell lid of a storage cell is arranged such that the spacer exerts a supporting force in an area located below an upper edge of the storage cells and adjacent to the weld seam. Preferably, the weld seam is located in the area of ​​the upper edge of the storage cell. The upper edge of the storage cell is preferably the edge that is adjacent to the poles of the storage cell.Additionally or alternatively, the spacer can be used to support a weld between a cell can and a cell lid of a storage cell, such that the spacer exerts a supporting force in an area located above a lower edge of the storage cell and adjacent to the weld, with the weld preferably being located in the area of ​​the lower edge of the storage cell. The cell lid can be located either at the top, e.g., as an upper side surface, or at the bottom, e.g., as a lower side surface, of the storage cell. The cell lid can also be referred to as the cell base.

[0029] The weld seam connecting the cell lid and cell canister can be particularly susceptible to damage, depending on the type of storage cell. This damage can be caused, for example, by changes in the cell volume. Positioning the spacer near the weld seam, but slightly offset towards the center of the storage cell, minimizes the stress on the weld seam from mechanical loads, thus improving the weld seam's stability and, consequently, the energy storage system's safety.

[0030] According to a further embodiment, the energy storage device also comprises two end plates between which the stacked storage cells are arranged. The stiffness of the end plates is set such that they deflect less than 1 millimeter when the cells are at maximum swelling. The end plates can additionally fix the storage cells, thus preventing damage to them. Preferably, the end plates can apply a preload to the storage cells, ensuring particularly secure fixation. In a further advantageous embodiment, the energy storage device can also include a housing in which the stacked storage cells and the two end plates are arranged. Preferably, the housing can be dimensioned such that it exerts a preload on the end plates and thus on the storage cells.In this way, components for pre-tensioning the end plates, and thus weight, can be saved.

[0031] According to a further general aspect of the present disclosure, a motor vehicle, preferably a commercial vehicle, comprising an energy storage device as described above, is provided. In other words, the features described in this document in connection with the energy storage device itself are also disclosed and claimable in connection with the motor vehicle. The motor vehicle can be, for example, a purely electrically powered vehicle. Preferably, the motor vehicle is a commercial vehicle (e.g., a truck or bus). Here, a commercial vehicle can generally be understood to be a vehicle that, by its design and equipment, is specifically designed for the transport of persons, the transport of goods, or the towing of trailers. Overall, this advantageously provides a motor vehicle whose energy storage device exhibits a particularly high level of safety.

[0032] The preferred embodiments and features of the invention described above can be combined in any way desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. These show:

[0033] Figure 1 shows a schematic representation of an energy storage device with a cell interlayer according to one embodiment;

[0034] Figure 2 shows a schematic representation of an energy storage device with a cell interlayer according to a further embodiment;

[0035] Figure 3 shows a schematic representation of a memory cell with spacer and compression element according to a further embodiment;

[0036] Figure 4 is a schematic representation of a memory cell with spacer and compression element according to a further embodiment; Figure 5 is a schematic representation of a memory cell with spacer and compression element according to a further embodiment; and

[0037] Figure 6 shows a schematic representation of a memory cell with spacer and compression element according to a further embodiment;

[0038] Figure 7 shows a schematic representation of a memory cell with spacer and compression element according to a further embodiment;

[0039] Figure 8 shows a schematic representation of a memory cell with spacer and compression element according to a further embodiment;

[0040] Figure 9 shows a schematic representation of various spacers according to further embodiments;

[0041] Figure 10 shows a schematic representation of an energy storage device with multiple storage cells, multiple cell interlayers and two end plates according to a further embodiment; and

[0042] Figure 11 shows a schematic representation of a motor vehicle with an energy storage device according to a further embodiment of the invention.

[0043] The embodiments shown in the figures are at least partially identical, so that similar or identical parts are provided with the same reference numerals and, to avoid repetition, reference is also made to the description of the other embodiments or figures for their explanation.

[0044] When arranging storage cells in energy storage devices, several challenges must generally be considered, some of which may have conflicting requirements. One problem is that a storage cell (battery cell) can sporadically experience thermal runaway. If neighboring storage cells are not thermally decoupled, there is a risk that they, too, can experience thermal runaway due to the heat generated by the first thermal runaway. This (chain-reaction-like) spread of thermal runaway is also known as thermal propagation. Therefore, one goal in the design of energy storage devices is to prevent thermal runaway from propagating. Another difficulty is that storage cells, depending on their aging, also known as state of health (SOH) loss, can experience a decrease in their overall energy capacity.Cells that develop internal pressure (referred to as "state of health") develop swelling. This pressure causes the storage cell to bulge, generating a force on the individual storage cells. The extent of aging is determined, among other things, by the cell's structure, chemistry, and operating parameters. Furthermore, the amount of counter-pressure the storage cell experiences from the outside influences its aging. Some cell designs require initial counter-pressure from day one for optimal, i.e., slow, aging, while others prefer very low or even no counter-pressure. Lifespan-optimized swelling is achieved when the optimal counter-pressure is generated during cell integration for the specific combination of storage cell and operating parameters.

[0045] Another aspect is the optimization of the energy storage device's mechanical robustness. Battery cells are typically integrated into cell modules. Adhesive and a preload force within the cell module / cell assembly are generally used for mechanical fixation. However, the mechanical weak points of storage cells are often not adequately protected by devices known in the prior art. These weak points are, in particular, weld seams in prismatic cells and sealing seams in pouch cells. The aim of the invention is therefore to reinforce these weak points through a localized, stronger compression within the cell assembly. Furthermore, the cell winding within the cell housing should be fixed by a localized force-fit at the beginning of its service life. During production, cell modules are sometimes pressed to size. Simultaneously, the initial counter-pressure must be set according to the cell chemistry (see service life).A certain level of mechanical support must also be achieved (see mechanical robustness).

[0046] The following describes advantageous designs that best meet these different requirements.

[0047] Figure 1 shows a schematic sectional view of an energy storage device 1 according to an embodiment of the invention. The energy storage device 1 comprises several stacked storage cells 3 for storing electrical energy. For clarity, only two storage cells 3 are shown in Figure 1, which are exemplary prismatic storage cells 3. An intermediate cell layer 2 is arranged between two storage cells 3 (battery cells). The intermediate cell layer comprises a spacer 4 and a compression element 5. Both the spacer 4 and the compression element 5 can be formed in one piece or alternatively comprise several sub-elements. Compared to the compression element 5, the spacer 4 has a higher thermal conductivity and lower compressibility.

[0048] The material of the compression element 5 can vary depending on the application. For example, the compression element 5 can be designed as a compression pad, preferably comprising a gel and / or aerogel. The thermal conductivity of the compression element 5 can, for example, be in the range of 0.02 W / K to 0.03 W / K. The spacer 4 can, for example, be made of a plastic or rubber material, such as a thermoplastic or polypropylene material and / or a thermally extruded or injection-molded plastic. The thermal conductivity of the spacer 4 can, for example, be in the range of 0.1 W / K to 0.3 W / K. It is particularly preferred that the thermal conductivity of the compression element 5 is at least five times, and particularly preferably at least eight times, lower than the thermal conductivity of the spacer 4.

[0049] The compression element 5 is dimensioned and arranged relative to the spacer 4 such that at least one side 6 of the spacer 4, facing one of the two adjacent storage cells 3, is completely covered by the compression element 5. The thickness of the compression element 5 and the spacer can be selected as required. Figure 1 shows that the compression element 5 extends to the entire height of the cell interlayer 2 on the left side, thus completely covering one side 6 of the spacer 4. In this way, the thermal connection between the two storage cells 3 is interrupted by the compression element 5, which has a lower thermal conductivity than the spacer, thereby providing good protection against unwanted thermal propagation.Simultaneously, the memory cells 3 are supported by the spacer 4 and held securely in their position. In Figure 1, the compression element 5 is shown in a state where it is uniformly relaxed over its entire height. However, the compression element 5 could also be compressed, for example, in the area of ​​the spacers 5, so that the supporting effect of the spacer 4 acts equally on both memory cells 3.

[0050] In the example shown in Figure 1, the spacer 4 rests directly on one of the two adjacent memory cells 3. On the other of the two adjacent memory cells 3, the spacer 4 rests indirectly via the compression element 5. The spacer can, for example, be frame-shaped and form a free space 8 into which the memory cells 3 and / or the compression element 5 can expand when the memory cells 3 swell.

[0051] Figure 1 shows the memory cells 3 in a non-swollen state. When cells swell, they bulge, particularly in the central region, resulting in a convex, e.g., slightly oval shape. The free space 8 allows the right memory cell 3 to expand directly into it, thus preventing excessive pressure on the cell due to swelling. Conversely, when the left memory cell 3 swells, it presses against the compression element 5. This compresses the compression element 5, for example, on the left side, and it can preferably expand simultaneously to the right into the free space 8, ensuring that the pressure on the left memory cell 3 is also kept within the desired range.

[0052] Several other embodiments of the spacer are presented in the following figures.

[0053] Figure 2 shows another schematic sectional view of an energy storage device 1 with a cell interlayer 2 according to a further embodiment of the invention. The storage cells 3, the compression element 5, and the spacer 4 essentially correspond to those of Figure 1. In Figure 2, only the position of the spacer 4 and the compression element 5 is reversed, so that the spacer 4 rests directly against the left storage cell 3. A side 7 of the compression element 5 facing the spacer 4 can completely cover the spacer 4.

[0054] In addition, the cell interlayer 2 in Figure 2 includes a further spacer 13, which rests directly on the other memory cell 3, here the right memory cell 3. The compression element 5 is arranged between the spacer 4 and the further spacer 13 and in a central area between the two adjacent memory cells 3. By way of example, the left side of the further spacer 13 is also completely covered by the compression element 5. Furthermore, the spacer 4 and the further spacer 13 are each arranged at the same height so that they can support each other. However, another arrangement in which the spacers are different from each other is also possible. In general, the further spacer 13 can be implemented in any embodiment in which the spacer 4 can also be implemented. All statements, e.g.The provisions regarding possible materials and / or geometric designs of the spacer 4 apply equally to the further spacer 13.

[0055] It is understood that all directional indications are merely examples. Any other spatial orientation of the individual components shown would be equally possible, provided that the relative arrangement of the components to each other is maintained in accordance with this disclosure.

[0056] Figure 3 shows a schematic representation of a memory cell 3 with spacer 4 and compression element 5 according to a further embodiment of the invention. The view in Figure 3 is in the stacking direction of the memory cells 3. For clarity, only one memory cell 3 is shown.

[0057] It can be seen that the spacer 4 has four sections extending along an upper and lower edge of a side surface of at least one of the two adjacent memory cells 3. The spacer 4 can comprise several sub-elements, which do not necessarily have to be connected to each other. The compression element 5, for example, can be located flat behind the spacer 4 and, for instance, rest directly on the memory cell 3. Here again, at least one side of the spacer facing one of the two adjacent memory cells 3 is completely covered by the compression element 5. In other words, the compression element can be dimensioned and arranged relative to the spacer such that no heat path for thermal coupling of two adjacent memory cells exists within the cell interlayer that runs completely through the spacer.

[0058] Figure 4 shows another schematic representation of a memory cell 3 with a spacer 4 and a compression element 5 according to a further embodiment of the invention. The spacer 4 extends in a plane that is substantially parallel to the adjacent memory cells 3. The spacer 4 extends in a rectangular shape around an outer area of ​​a side surface of the memory cell 3. The spacer can, for example, be designed as a rubber frame. In the center, the spacer 4 has a space 8 into which the memory cells 3 and / or the compression element 5 can extend. Here again, at least one side of the spacer facing one of the two adjacent memory cells 3 is completely covered by the compression element 5. This also applies to the embodiments shown in the following figures.

[0059] Figure 5 shows another schematic representation of a storage cell 3 with spacer 4 and compression element 5 according to a further embodiment of the invention. This time, the partial elements of the spacer 4 extend along the lateral outer surfaces of the storage cells 3. The resulting shorter overall design of the spacer 4 allows for particularly unimpeded volume expansion of the storage cells 3.

[0060] Figure 6 shows another schematic representation of a memory cell 3 with spacer 4 and compression element 5 according to a further embodiment of the invention, this time in a perspective view.

[0061] The storage cell 3, the compression element 5, and the spacer 4 essentially correspond to those shown in Figure 3. Additionally, Figure 6 shows the cell housing 10 and the cell cover 11, as well as a weld 9 connecting these two components. The cell housing 10 refers to the surrounding shell of the storage cell 3, specifically the four side surfaces, each extending along the vertical direction. The cell cover 11 is the top surface. However, it could also refer to the bottom surface of the storage cell 3. The cell cover 11 can also be called the cell base.

[0062] The weld 9, which connects the cell lid 11 and the cell canister 10, can in many cases be a mechanical weak point of the storage cell 3. In particular, when the storage cell expands and contracts during swelling, the weld 9 can be subjected to mechanical stress. Therefore, the spacer 4, which supports the weld 9 between the cell canister 10 and the cell lid 11, can be arranged such that the spacer 4 exerts a supporting force in an area located below an upper edge of the storage cells 3 and / or above a lower edge of the storage cells 3 and adjacent to the weld 9. Accordingly, the upper part of the spacer 4 is positioned slightly below the weld 9 in Figure 6. During cell swelling, the storage cell 3 therefore bulges primarily below the upper part of the spacer 4, thus reducing the mechanical stress on the weld.Figure 7 shows another schematic representation of a memory cell 3 with spacer 4 and compression element 5 according to a further embodiment of the invention. This time, the view is again in the direction of the stacking of the memory cells. The memory cell 3, the compression element 5, and the spacer 4 again correspond essentially to those of Figure 3. In contrast to Figure 3, the spacer 4 of Figure 7 has triangular sections in a plane running essentially parallel to the adjacent memory cells 3. Other geometric shapes, e.g., curves, are also possible. In this way, the memory cell 3 can be effectively supported precisely at the points where this is ideal for the respective type of memory cell 3. In Figure 7, the triangular sections are arranged by way of example at the upper edge regions of the memory cell 3.Of course, they could just as easily be in other positions and / or in different numbers.

[0063] Figure 8 shows another schematic representation of a memory cell 3 with spacer 4 and compression element 5 according to a further embodiment of the invention. The memory cell 3, the compression element 5, and the spacer 4 again correspond essentially to those of Figure 3. In contrast to Figure 3, the spacer 4 of Figure 8 has rectangular sections of different widths and / or sizes in a plane that runs essentially parallel to the adjacent memory cells 3. The individual sections of the spacer 4 can be formed in one piece or as separate components.

[0064] Figure 9 shows a schematic representation of various spacers 4 according to further embodiments of the invention. The spacers 4 shown in Figure 9 can, for example, replace the upper and / or lower part of the spacer 4 of Figure 3.

[0065] To thermally decouple the storage cells, the total possible heat conduction between adjacent storage cells should be kept as low as possible. As previously described, materials with the lowest possible thermal conductivity can be used for this purpose. Since the spacer 4 has a higher thermal conductivity than the compression element, the thermal decoupling of adjacent storage cells can be further improved by optimizing the design of the spacer 4. In particular, it can be advantageous to reduce the surface area of ​​the spacer 4 relative to the side surface of the storage cells. Figure 9 shows various embodiments of a spacer 4 that allow for a reduced surface area. For example, the spacer 4 can include sections that are strip-shaped, triangular, comb-shaped, or rib-shaped, and / or that have a wave-like or zigzag pattern.It is also possible for the spacer to include sections with a perforated structure, in this case in the form of rectangular recesses. The recesses can be uniform, as shown in Figure 9. Irregular arrangements and various geometric shapes are also possible.

[0066] Figure 10 shows a schematic representation of an energy storage device 1 according to a further embodiment of the invention. The energy storage device 1 has several storage cells 3 and several cell interlayers 2. Furthermore, two rigid end plates 12 are arranged on the two outer surfaces of the energy storage device 1. The rigidity of the end plates 12 is preferably determined such that the end plates 12 deflect by less than 1 millimeter when the storage cells 3 are at maximum cell swelling. The state of maximum cell swelling and the corresponding design of the stiffness of the end plates can be determined and tested, for example, experimentally, e.g., by laboratory tests.

[0067] By means of the end plates 12 designed in this way, the storage cells 3 (cell modules) can be securely fixed geometrically in place around the battery cells. If the end plates were not rigid enough, they could deflect significantly, causing cells to shift geometrically within the module and even rupture. The counter-pressure on the cells could decrease, resulting in a suboptimal pressure distribution within the cell module.

[0068] In contrast, the rigid end plates 12 ensure that the memory cells 3 can be operated in an ideal pressure range throughout their entire lifespan.

[0069] The spacers 4 preferably ensure optimal fixation of the individual memory cells 3 throughout their entire service life, i.e., from the beginning of life (BOL) to the end of life (EOL). In particular, they support (not shown) weld seams throughout the entire service life. During the production of the energy storage module 1, the spacers 4 can compensate for tolerances in the stacking process. Through suitable material selection and optimized geometry, heat paths between memory cells 3 can be optimized, and in particular minimized. This also allows for cell swelling of the memory cells 3. Depending on the memory cell type, free swelling can be permitted at the beginning of the service life. The compression element 5, e.g., the compression pad, supports the memory cells 3 according to the requirements of the respective cell chemistry.Furthermore, the compression element 5 provides thermal decoupling of the individual memory cells 3.

[0070] Figure 11 shows a schematic representation of a motor vehicle 14 with an energy storage device 1 according to a further embodiment of the invention. The energy storage device 1 can, for example, be a traction energy storage device. It is understood that the techniques and features described with reference to Figure 11 can be combined with the techniques and features described with reference to Figures 1 to 10, individually or in any combination. The motor vehicle 14 can be designed as a commercial vehicle (e.g., a semi-trailer truck or a truck with a body), as shown by way of example. However, the motor vehicle 14 can also be a passenger car. Preferably, the motor vehicle 14 is at least partially or purely electrically powered. The energy storage device 1 can be arranged on a longitudinal outer side of the motor vehicle 14 or at another location.

[0071] Although the invention has been described with reference to specific embodiments, it is apparent to a person skilled in the art that various modifications can be made and equivalents can be used as substitutes without departing from the scope of the invention. Consequently, the invention is not intended to be limited to the disclosed embodiments, but rather to encompass all embodiments falling within the scope of the appended claims. In particular, the invention also claims protection for the subject matter and features of the dependent claims independently of the referenced claims.

[0072] Reference symbol list

[0073] 1 Energy storage device

[0074] 2 intercellular layer

[0075] 3 memory cells

[0076] 4 spacers

[0077] 5 compression element

[0078] 6. Memory cell facing the spacer

[0079] 7 Spacers facing the side of the compression element

[0080] 8 Free space of the spacer

[0081] 9 weld seam

[0082] 10 cell doses

[0083] 11 cell lids

[0084] 12 End plate

[0085] 13 Additional spacers

[0086] 14 Motor vehicle

Claims

Patent claims 1. Energy storage device (1) for storing electrical energy for a motor vehicle (14), comprising several stacked storage cells (3), preferably prismatic storage cells (3), wherein a cell interlayer (2) is arranged between two adjacent storage cells (3) and the cell interlayer has a spacer (4) and a compression element (5), preferably a compression pad, wherein the spacer (4) has a higher thermal conductivity and a lower compressibility compared to the compression element (5) and wherein the compression element (5) is dimensioned and arranged relative to the spacer (4) such that at least one side (6) of the spacer (4), which faces one of the two adjacent storage cells (3), is completely covered by the compression element (5).

2. Energy storage device (1) according to claim 1, wherein the spacer (4) rests directly on one of the two adjacent storage cells (3) and indirectly on the other of the two adjacent storage cells (3) via the compression element (5).

3. Energy storage device (1) according to claim 1 or 2, wherein the cell interlayer (2) has a further spacer (13), wherein the spacer (4) rests directly on one of the two adjacent storage cells (3) and the further spacer (13) rests directly on the other of the two adjacent storage cells (3) and the compression element (5) is arranged between the spacer (4) and the further spacer (13) and in a central area between the two adjacent storage cells (3).

4. Energy storage device (1) according to one of the preceding claims, wherein a side (7) of the compression element (5) facing the spacer (4) completely covers the spacer (4).

5. Energy storage device (1) according to one of the preceding claims, wherein the spacer (4) is frame-shaped and forms a free space (8) into which the storage cells (3) and / or the compression element (5) can expand when the storage cells (3) swell.

6. Energy storage device (1) according to one of the preceding claims, wherein the spacer (4) extends in a plane substantially parallel to the adjacent storage cells (3) a) in a rectangular shape circumferentially along an outer surface of a side surface of the storage cells (3); or b) has rectangular and / or triangular sections.

7. Energy storage device (1) according to one of the preceding claims, wherein the spacer (4) has sections extending along an upper and lower edge of a side surface of at least one of the two adjacent storage cells (3).

8. Energy storage device (1) according to claim 7, wherein the sections a) are strip-shaped, triangular, comb-shaped or rib-shaped and / or have a wave-shaped or zigzag-shaped profile; and / or b) have a hole structure.

9. Energy storage device (1) according to one of the preceding claims, wherein a thermal conductivity of the compression element (5) a) is in the range of 0.02 W / K to 0.03 W / K and a thermal conductivity of the spacer (4) is in the range of 0.1 W / K to 0.3 W / K; and / or b) is at least by a factor of five, preferably by at least a factor of eight, smaller than a thermal conductivity of the spacer (4).

10. Energy storage device (1) according to one of the preceding claims, wherein the spacer (4) is made of a plastic or rubber material, preferably of a thermoplastic or polypropylene material and / or a thermally extruded or injection-molded plastic; and / or wherein the compression element (5) is a compression pad, preferably comprising a gel and / or aerogel.

11. Energy storage device (1) according to one of the preceding claims, wherein, for supporting a weld seam (9) between a cell can (10) and a cell lid (11) of a storage cell (3), the spacer (4) is arranged such that the spacer (4) exerts a supporting force in a region which is below an upper edge of the storage cells (3) and / or above a lower edge of the storage cells (3) and adjacent to the weld seam (9).

12. Energy storage device (1) according to one of the preceding claims, further comprising two end plates (12) between which the stacked storage cells (3) are arranged, wherein the stiffness of the end plates (12) is determined such that the end plates (12) bend less than 1 millimeter when in a state of maximum cell swelling.

13. Motor vehicle (14), preferably commercial vehicle, comprising an energy storage device (1) according to one of the preceding claims.

Images