Prismatic battery cell

Abstract

The invention relates to a prismatic battery cell with a cell housing (1) in which an electrode / separator stack (15) is arranged, wherein the cell housing (1) is cuboid in shape and its housing walls are divided into narrow side walls (7), flat side walls (9), and bottom and top walls (3, 5), of which the flat side walls (9) define the boundaries of the electrode / separator stack (15) on both sides in the stacking direction, and wherein, during a charging phase, the volume of the electrode / separator stack (15) increases, particularly in the stacking direction, thereby subjecting the cell housing (1) to mechanical stress. According to the invention, measures are provided to ensure that the cell housing can withstand mechanical stresses resulting from the volume increase of the electrode / separator stack (15) during the charging phase without damage.

Description

[0001] The invention relates to a prismatic battery cell according to the preamble of claim 1, claim 2, claim 4, claim 6, claim 8, and a method according to claim 10.

[0002] In a prismatic battery cell known from the state of the art, specifically with a silicon-based anode, the following problems arise: First, volume changes occur during charging and discharging of a Li-ion cell. These changes can be more significant depending on the type of anode material used in the cell. For a graphite electrode, the expansion is up to 10%. However, for a silicon-based electrode (which has ten times the energy density of graphite), the volume expansion during full lithiation at high temperatures can be as much as 300%. This extreme volume change during charging and discharging leads to high mechanical stress on the anode material and thus significantly shortens the cell's service life.

[0003] A second problem does not concern degradation at the electrode level, but rather degradation at the cell level, since inhomogeneous deformation of the cell is directly linked to the performance degradation of the cell integrated into a complete battery system. Among the degradation factors at the cell level are: uneven electrochemical reaction, temperature, and mechanical stress. In the latter case, the cell casing plays a very important role. The casing must protect the cell from external mechanical stress, i.e., it must provide shock resistance; at the same time, the cell casing must also be sufficiently dimensionally stable against the internal cell pressure that builds up during swelling. Mechanical casing stresses due to swelling can lead to the fracture of casing welds. Therefore, the cell casing must be very strong. If this requirement is not met (i.e.,If the cell casing expands excessively), as can be the case with silicon-based electrodes, a rapid drop in the cell's capacity is to be expected.

[0004] Third, to compensate for cell swelling, or the expansion of the cell casing, compression pads are typically used, which can achieve a compression of approximately 80 to 100%. If greater compression is required, the thickness and weight of such a compression pad increase. This means that the size and weight of the module increase, which in turn affects the cell's energy density, which is actually achieved by using silicon-based anode materials.

[0005] A fourth problem arises from the following: In an ideal scenario, a compression pad would be used after each cell in the battery cell stack. However, due to weight and size constraints, such a compression pad is used after three to five cells. This means that the cells closer to the compression pad receive a high or sufficient compressive force, while the other cells do not experience high compressive stress.

[0006] Fifth, a conventional compression pad can only generate uniform tension up to its maximum compression. After that, it behaves like a rigid block and no longer like a spring. A compression pad of approximately 2 mm can act like a spring up to a maximum compression of 1 mm. After that, it behaves like a rigid block.

[0007] In the current state of the art, the above-mentioned problems, which arise from the strong expansion of silicon (compared to graphite), are solved by reducing the silicon content of the anode to a maximum of 10%, which hinders the potential use of the anode to increase the energy density of Li-ion batteries. In addition, the use of compression pads in the battery module is the conventional approach to exert pressure on the cell and reduce cell swelling.

[0008] Such a reduction in the silicon content in the anode material significantly reduces the cell's energy density, as silicon-based anode materials have a gravimetric capacity of 3572 mAh / g, which is almost ten times higher than that of graphite materials (372 mAh / g), which are commonly used as anode materials. Furthermore, a higher silicon content in the anode would greatly increase the cell's fast-charging capability.

[0009] DE 10 2016 009 394 A1 discloses a motor vehicle battery with at least one cell block and a balancing unit. This has at least one balancing element for at least partially balancing axial compressive forces within the cell block. DE 10 2013 114 317 A1 discloses a battery device with a battery housing for a motor vehicle. At least one deformation element is arranged on the battery housing for at least partially absorbing an unwanted external force acting on the battery housing (to protect the battery cell). US 2017 013 3706 A1 discloses a battery cell stack in which the battery cells are subjected to mechanical tension from both stack ends by a pair of end plates. The two end plates are connected to one another in a force-transmitting manner by means of metal bands.

[0010] The object of the invention is to provide a prismatic battery cell and a method for producing such a battery cell, the cell housing of which, in comparison to the prior art, can withstand mechanical stress due to an increase in volume (swelling) of the electrode / separator stack during the charging phase in a simple manner and without damage.

[0011] The object is achieved by the features of claim 1, 2, 4, 6, 8 or 10. Preferred developments of the invention are disclosed in the subclaims.

[0012] The invention is based on the following fact: The aluminum cell housing can compensate for volume expansion up to the maximum yield strength of the cell housing material. The aluminum cell housing is then permanently plastically deformed. The aluminum cell housing is normally manufactured without welding using an extrusion or deep-drawing process. In this case, good formability of the aluminum is required. Against this background, aluminum with little or no alloying components is normally used as the cell housing material. However, this cell housing material is not capable of building up high compressive strength in the event of cell swelling, since its yield strength is in a low range of approximately 40 to 60 N / mm 2 lies.

[0013] As an alternative to the extrusion or deep-drawing process, it is also possible to manufacture the cell casing by bending and then laser welding aluminum blanks. However, this poses the problem that the weld can crack due to swelling under mechanical stresses on the casing. Furthermore, the use of aluminum is essential due to its good thermal conductivity compared to other metals, such as steel. Furthermore, the swelling of the cell leads to greater mechanical stress in the center of the prismatic cell casing. This means that this area in particular should have a higher compressive strength or yield strength.

[0014] Against this background, the invention relates to the measures described below: First, the housing side walls (hereinafter also referred to as flat side walls) of the aluminum cell housing, which require a higher yield strength than, for example, the base, can have embossed structures. These embossed structures ensure a locally high yield strength due to work hardening. The embossed structures on the contact surfaces of adjacent battery cells can be offset from one another in such a way that the cell housings of the neighboring battery cells fit together in a tight, form-fitting manner, like Lego bricks. If compression pads are used, these can have a negative form of the embossed structure, allowing the embossed structure of the adjacent battery cell to be contour-fitted into the embossed structure negative form of the compression pad.

[0015] Second, the thickness of the cell casing material (i.e., aluminum) can be increased in areas of high swelling. Due to the increased thickness, the cell casing can provide increased dimensional stability or compressive strength. The cell casing can be manufactured from a tailored rolled blank, which can be produced in various thicknesses. The blank can be manufactured into the cell casing either by deep drawing or by bending.

[0016] The third measure proposed is the following: The cell casing can be manufactured in the conventional way from a soft aluminum material with a thickness of, for example, around 0.5-0.8 mm. It is then wrapped with a winding material, for example a winding wire, which allows compressive stress to be introduced into the cell casing from the outside. The compressive stress introduced from the outside of the casing must first be overcome by the mechanical casing stress (i.e. tensile stress) caused by swelling. Only after this compressive stress induced from the outside of the casing has been overcome does the build-up of tensile stress in the cell casing begin. This means that the more compressive stress there is induced from the outside of the casing, the more mechanical casing stress (i.e. tensile stress) caused by swelling the cell casing can absorb without damage.

[0017] In a fourth measure, the still unpopulated cell casing can be placed in a hydraulic chamber before inserting the electrode / separator stack and pressurized with high-pressure fluid from the outside of the casing to apply compressive stress to the cell casing. This leads to permanent plastic deformation of the cell casing material, which compacts. This increases the compressive strength of the cell casing, allowing it to withstand increased internal pressure due to swelling of the electrode / separator stack without plastic deformation occurring.

[0018] According to a fifth aspect of the invention, the aluminum cell housing can be constructed from an inner housing and an outer housing. There is an interference fit between the two housings. This means that, in the undeformed state, the inner dimensions of the outer housing are approximately 0.1 to 0.2 mm smaller than the outer dimensions of the inner housing. The outer housing is heated to approximately 300°C; the inner housing is then inserted into the outer housing. Upon cooling, the outer housing is shrunk onto the inner housing, thereby generating compressive stress in the inner housing. The outer housing undergoes tensile stress. The outer housing is preferably made of high-strength aluminum, such as aluminum with approximately 500 N / mm 2and can have a wall thickness of approximately 0.2 to 0.3 mm. The inner housing can be made of conventional aluminum with a thickness of approximately 0.5 mm. It is important that the corner of the outer housing has a larger radius than the inner housing so that the corner radius does not experience excessive tensile stress.

[0019] According to a sixth aspect of the invention, the cell casing can be covered with a strip or tape made of carbon fiber reinforced plastic (CFRP). This material has extremely high tensile strength and, compared to metals, is significantly more resistant to volume expansion or swelling of the cell casing. The CFRP strip(s) can tightly grip the cell casing and exert compressive stress on it. Furthermore, the applied CFRP strip(s) can always be subjected to a certain minimum tensile stress when wrapped around the cell casing.

[0020] It's worth emphasizing that aluminum is the preferred material for the cell casing in all six of these measures. Additional materials, such as CFRP, help apply compressive stress to the cell casing from the outside.

[0021] In summary, the following main differences exist between the present invention and the prior art: The cell casing aluminum has a higher yield strength than aluminum conventionally used for the cell casing, without changing the starting material in cell casing production. Rather, the aluminum material used according to the invention for cell casing production can be the same as that used in the prior art. However, the invention takes the six measures outlined above to introduce additional compressive stress or compressive strength into the cell casing. Each of the six measures described above can be used individually or in combination. The cell casing according to the invention is particularly necessary if the electrode / separator stack has silicon-based anodes that swell considerably during the charging phase.In this case, it is not possible to compensate for the resulting cell casing expansion using compression pads. The volume of the compression pad would increase proportionally to the swelling, which in turn reduces the volumetric energy density of the battery cell. Therefore, the aluminum cell casing must absorb most of the mechanical casing stresses caused by swelling without causing plastic deformation and cracking in the cell casing.

[0022] In the first step, the cell casing is preformed with embossed structures that locally increase hardness and strength through work hardening. To allow adjacent cells to be placed close together, the embossed structures between neighboring cells can be offset. In this way, a raised portion of the embossed structure of one battery cell takes up space in a recessed portion of the embossed structure of the neighboring battery cell. The compression pad can have a negative embossed structure mold into which the respective embossed structure of the battery cells can be fitted with a form-fitting fit. This results in a high packing density of the stacked battery cells; moreover, the battery cells stacked in the cell stack exhibit greater resistance to swelling.

[0023] The second method uses a tailored rolled blank. Here, the aluminum thickness is not uniform. Areas subject to higher swelling force have a higher thickness. The tailored welded blank is produced using the hot-rolling process and has no welds between a lower and a higher aluminum thickness. There is a small transition zone between two aluminum thicknesses.

[0024] In the third measure, the cell casing has a U-shaped or groove-shaped channel on its surface in which the wires are wound. These wires are wound under tensile load, i.e. the wires are subjected to tensile stress so that a compressive stress is applied to the cell casing from the outside. The start and end points of the wire can be connected to the cell casing, for example by welding. For example, the wire can be wound spirally. It is also possible to wrap wire in a ring shape around the cell casing. To avoid welding the wire ends, each wire can be placed in a U-shaped recess around the cell casing and then the next wire can be placed under the first wire.

[0025] In the fourth step, the aluminum cell casing is pressed from the outside using the hydrostatic force of a high-pressure fluid. This compresses the cell casing material; a cell casing material that is initially soft (i.e. aluminum) is thereby given greater strength. For this purpose, the cell casing is placed in a pressurizable hydraulic chamber. A counterbearing for the hydraulic pressure acting on the outside of the casing can be inserted into the interior of the cell casing. The counterbearing can have a piston that is encased in an elastomer body. The piston exerts pressure on the inside of the cell casing with the elastomer body interposed. In contrast, the high-pressure fluid acts on the outside of the cell casing. The pressure can be up to 10,000 bar, for example. The test can also be carried out at temperatures of up to 100°C.This makes the aluminum's microstructure more uniform, finer, and less porous, increasing its strength by two to three times.

[0026] In the fifth measure, the aluminum housing consists of an inner housing press-fitted into an outer housing, which can be realized as a high-strength aluminum ring. Installation is achieved by heating the outer ring and then inserting the aluminum housing into the outer ring. After cooling, the outer ring exerts compressive stress on the inner housing. This increases the compressive residual stress of the inner ring. This increased compressive stress must first be overcome by internal swelling stress before tensile stress can build up in the inner housing. The higher this compressive residual stress, the higher the swelling stress can be.

[0027] The sixth step involves wrapping a CFRP strip or tape around the cell casing. This concept is similar to wire wrapping; however, here carbon fiber reinforced plastic (CFRP) is wrapped around the casing. The CFRP strip with pre-impregnated matrix material (i.e., epoxy resin) is wound around the cell casing as a prepreg (i.e., with uncured epoxy resin) during the winding process; the CFRP strip can be applied to the outside of the casing with minimal tension. Afterwards, both the casing and the CFRP are placed in an oven at 180°C for 30 minutes. This oven cures the CFRP with the epoxy resin, resulting in maximum strength. It is also possible to use CFRP with epoxy resin, which cures at approximately 60°C, which also corresponds to high-temperature aging. This type of CFRP is referred to as RTM (room temperature molded). In this case, two heat treatments are required.Instead, curing can occur during the battery cell's high-temperature aging process, where the process temperature is approximately the required curing temperature. Instead of CFRP, glass-fiber reinforced plastic (GFRP) can also be used. This has even greater rigidity than CFRP. The basic idea is to increase the strength of the aluminum cell casing without increasing the cell's weight.

[0028] In summary, the invention provides the following advantages: Compression pads are no longer required or can be used with reduced thickness. Silicon-based anodes can be used with a higher silicon content (more than 15%) without compromising the volumetric energy density. The aluminum cell casing according to the invention is stronger than a conventional aluminum cell casing. The use of CFRP or GFRP (glass fiber reinforced plastic) can, in addition to its high strength, also have a flame-retardant effect. The cell casing does not undergo plastic deformation or cracking during the charging cycle. This means a longer cell service life. There is no need to generate additional compressive stresses through bolts and nuts at the module level. The compressive force is only increased in the area where greater swelling occurs.Similarly, the tensile strength or thickness of the aluminum casing is increased only where needed. This means that material and strength are optimized based on the internal swelling stress. This facilitates the design of lighter cells. Various measures can be used in combination. In this case, geometric stiffness (through indentations or stamped shapes) can be added to material stiffness (through custom-rolled blanks) to achieve higher overall stiffness. Increased residual compressive stresses built up by other measures are not relieved because there is no relaxation process at high temperatures in the battery cell. Therefore, these residual compressive stresses will still remain in the cell casing and drastically increase the area of ​​internal stress due to swelling.The cell casing does not have to be made of expensive, high-strength materials such as steel or composites.

[0029] Exemplary embodiments of the invention are described below with reference to the accompanying figures. They show: Fig. 1 to 17 are views illustrating different measures to ensure that the cell casing of the battery cell can withstand swelling without damage.

[0030] In the Fig. 1 shows a lithium-ion battery cell which is realized in a prismatic cell format, namely with a cuboid-shaped cell housing 1 made of aluminum, which has bottom and top walls 3, 5 opposite each other in the vertical direction z of the housing, as well as narrow side walls 7 opposite each other in the longitudinal direction x of the housing. These connect flat side walls 9, which are opposite each other in a depth direction y of the housing. Cell poles 11, 13 are formed in the top wall 5 of the battery cell. An electrode / separator stack 15 (for example Fig. 4), which consists of stacked cathode, separator, and anode sheets. The two flat side walls 9 of the cell housing 1 define the electrode / separator stack 15 on both sides in the stacking direction.

[0031] During a charging phase, the volume of the electrode / separator stack 15 increases, particularly in the stacking direction (i.e., swelling), whereby the cell casing 1 is subjected to mechanical stress from the inside. Conversely, during a discharging phase, the volume of the electrode / separator stack 15 decreases.

[0032] Below, based on the Fig. 2 to 17 different measures are described so that the cell casing 1 can withstand mechanical stress due to the volume increase (swelling) of the electrode / separator stack 15 during the charging phase without damage: According to the Fig. 2 to 4, embossed structures 17 are formed in the flat side walls 9, which are particularly subject to mechanical housing stress. The embossed structures 17 have a regular pattern of elevations 19 and depressions 20, which have been formed into the flat side walls 9 by work hardening the material. The formation of the embossed structures 17 results in an increased yield strength for the material in the flat side walls 9. This increases the elastic range in the stress-strain diagram required to compensate for the mechanical housing stress.

[0033] In the Fig. 3a shows the embossed structure 17 in an enlarged view and in a sectional view. Accordingly, the material hardness (measured in HV) is increased especially in the area of ​​the depression 20 formed by work hardening, as can be seen from the diagram of Fig. 3b.

[0034] According to the Fig. 4, the embossed structures 17 on the contact surfaces of adjacent battery cells in the electrode / separator stack 15 are adapted such that a respective elevation 19 of one embossed structure 17 protrudes positively into the depression 20 of the other embossed structure 17. Alternatively, a compression pad (not shown) can be arranged between the adjacent battery cells, which can absorb mechanical housing stresses in the battery cells due to swelling. The compression pad can have a negative embossed structure shape at the contact surfaces to the adjacent battery cells, into which the embossed structure 17 of the respective battery cell can engage in a positive fit.

[0035] In the embodiment of the Fig. 5 to 7, the wall thickness s of the flat side walls 9, which are particularly subjected to mechanical housing stress during the charging phase, is increased by an allowance compared to the remaining housing walls 3, 5, 9. By increasing the wall thickness s on the flat side walls 9, the compressive strength of the cell housing 1 increases there, which also increases the dimensional stability of the cell housing 1 during the increase in volume of the electrode / separator stack 15.

[0036] In the Fig. 6, the flat side walls 9 as well as the top wall 3 and the bottom wall 5 of the cell housing 1 are shown in a developed view. Accordingly, the flat side walls 9 as well as the top wall 3 and the bottom wall 5 are components of a rolled sheet metal part 21 (i.e., tailored rolled blank), in which the sheet metal sections 9' forming the flat side walls 9 have a greater wall thickness than the sheet metal sections 3' and 5' forming the bottom and top walls. Fig. 7 shows a rolling process, after which the sheet metal part 21 is guided in the production direction F through a roll gap formed by the forming rolls 23, 25. The forming rolls 23, 25 have different diameters, so that the roll gap also has different gap dimensions when viewed in the axial direction, which correspond to the different wall thicknesses in the rolled sheet metal part 21.

[0037] In the further course of the process, a blank is cut from sheet metal part 21 and bent at the transitions between sheet metal sections 3', 5', and 9'. Alternatively, different wall thicknesses in the cell housing 1 can also be produced using an extrusion process, in which the distance between the mandrel and the die is varied. Rolling and forming takes place at 350-400°C. A greater wall thickness directly where the mechanical housing stress is particularly strong leads overall to greater dimensional stability of the cell housing 1.

[0038] In the Fig. 8 to 10, a further embodiment is shown in which, to support the dimensional stability of the cell housing 1, in particular during the charging phase, a winding wire 27, in particular aluminum wire, is wound around the cell housing 1 in a winding process. According to the Fig. 9, the winding wire 27 is wound spirally with a number of turns around the cell casing 1. Alternatively, in the Fig. 10, the winding wire 27 consists of individual wires. These are each wound around the cell casing 1 with only one turn. To secure the position of the winding wire 27 laid on the outside of the cell casing 1, the casing can have grooves into which the winding wire 27 can be inserted.

[0039] During the winding process, the aluminum wire 27, which can have a diameter of between 0.2 and 0.5 mm, is wound onto the cell casing 1 under tensile stress, which leads to compressive stresses in the cell casing 1. At the start of winding, the wire 27 is welded to the cell casing 1 and then wound up using a winding machine. At the end of winding, the free wire end is welded back to the cell casing 1. In order for the wire 27 to remain securely positioned on the cell casing 1, the cell casing 1 can have grooves on the outside in which the wire 27 is laid. A predefined corner radius (for example of 0.5 mm) on the cell casing 1 is required to ensure that the wire 27 is not subjected to excessively high local stresses.

[0040] Alternatively, in the example the Fig. 16 and Fig. 17, the winding material is not a winding wire 27, but rather a tape or band 29 made of carbon fiber-reinforced plastic (hereinafter referred to as CFRP tape). The CFRP tape 29 is provided as a prepreg pre-impregnated with matrix material in preparation for the winding process. After the winding process is completed, the CFRP tape 29 is heated to above the melting temperature of the matrix material, building up its maximum tensile strength. This allows for consolidation, during which the carbon fibers are completely saturated with the molten matrix material.

[0041] CFRP exhibits very high tensile strength and a high modulus of elasticity. Furthermore, CFRP offers flame-retardant properties. The CFRP tape 29 absorbs the internal energy generated by swelling and prevents uncontrolled plastic deformation of the aluminum housing. CFRP is primarily used as a so-called woven CF or NCF (non-crimped fiber) PrePreg. In both PrePregs, carbon fibers (CF) are pre-impregnated with epoxy resin. As already mentioned, the CFRP tape 29 is wound around the cell housing 1. The CFRP tape 29 is wound such that it is subject to minimal tensile stress in its initial state. During the winding process, the CFRP tape 29 is not yet cured. Curing occurs after the winding process, giving the CFRP tape 29 its maximum strength. For this purpose, the prismatic housing 1 wound from CFRP is placed in an oven at 180°C, for example, for 30 minutes.In addition, after curing, the epoxy resin also adheres firmly to the prismatic housing.

[0042] In the Fig. 17 shows a device for producing the CFRP tape 29. Accordingly, the CFRP tape 29 has a multi-layer structure consisting of four stacked individual CFRP layers in which the fibers run in different fiber orientations.

[0043] In the Fig. 11 and Fig. 12, the dimensional stability of the cell casing 1 is increased, especially during the charging phase, as follows: The cell casing 1 is subjected to a material compaction in its still unpopulated state, i.e., before the electrode / separator stack 15 is inserted, in which the material of the cell casing 1 is compacted, increasing its tensile strength. According to the Fig. 11 and Fig. 12, the material is compacted in a device with a hydraulic chamber 31. According to the Fig. 11, the cell housing 1 is inserted into the hydraulic chamber 31 and is pressurized with hydraulic pressure from the outside of the housing by means of a high-pressure fluid. On the inside of the housing, however, the cell housing 1 is completely filled with a counterbearing 33. This consists of a plunger 32 encased in an elastomer body 34. The plunger 32 is pressed against the inside of the cell housing 1 with the elastomer body 34 interposed.

[0044] The hydraulic pressure p H in the hydraulic chamber 31 can be up to 10,000 bar, for example. This compresses the cell housing material, giving it a more homogeneous and dense structure. This increases the tensile strength of the cell housing 1. As can be seen from the Fig. As shown in Figure 11, the cell housing 1 is first secured to the counterbearing 33 inside the housing and then inserted into the hydraulic chamber 31. After the pressure cycle, the cell housing 1 is firmly connected to the counterbearing 33. For removal from the housing interior, the counterbearing cross-section is reduced (e.g., by telescopically inserting components of the counterbearing into one another). The counterbearing 33 with its reduced cross-section can therefore be easily removed from the housing interior during production.

[0045] As an alternative to hydraulic pressurization, it is also possible to generate a similar pressure by inserting the housing into a die and the die then generating a corresponding pressure.

[0046] In the Fig. 13 to 15, a further embodiment is shown to increase the dimensional stability of the cell housing 1, particularly during the charging phase, against swelling. Accordingly, the cell housing 1 is constructed from an outer housing 35 and an inner housing 37. The inner housing 37 is inserted into the outer housing 35 with a press fit, building up a mechanical counter-stress, which, for example, surrounds the flat side walls and the narrow side walls of the inner housing 37 in a ring shape. The mechanical counter-stress counteracts the mechanical housing stress that builds up during the charging phase, as shown in the schematic diagram of the Fig. 15. This means that the counter-stress exerted by the outer casing 35 must first be overcome by mechanical casing stress generated by the internal swelling load before a tensile stress can build up in the inner casing 37. The higher this residual compressive stress, the higher the swelling load can be.

[0047] The inner housing 37 is assembled with the outer housing 35 by shrinking, during which the outer housing 35 is heated. The inner housing 37 is then inserted into the heated outer housing 35. The outer housing 35 is then shrunk onto the inner housing 37 while cooling. The material used for the inner housing 37 can be soft aluminum, while high-strength aluminum is used for the annular outer housing 35. List of reference symbols 1 cell housing 3, 5 Floor / ceiling wall 3', 5' sheet section 7 Narrow side wall 9 Flat side wall 9' sheet metal section 11, 13 cell poles 15 electrode / separator stacks 17 Embossed structure 19 Increase 20 Deepening 21 rolled sheet metal part 23, 25 forming rollers 27 winding wire 29 Tape 31 Hydraulic chamber 33 Counter bearing 35 outer casing 37 inner casing s wall thickness F Production direction P H hydraulic pressure QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2016 009 394 A1

[0009] DE 10 2013 114 317 A1

[0009] US 2017 013 3706 A1

[0009]

Claims

[1] Prismatic battery cell with a cell housing (1) in which an electrode / separator stack (15) is arranged, wherein the cell housing (1) is cuboid-shaped and the housing walls of which are divided into narrow side walls (7), flat side walls (9) and base and cover walls (3, 5), of which the flat side walls (9) delimit the electrode / separator stack (15) on both sides in the stacking direction, and wherein in a charging phase the volume of the electrode / separator stack (15) increases, in particular in the stacking direction, whereby the cell housing (1) is subjected to mechanical housing tension, characterized bythat the process for producing the cell casing (1) comprises a process step in which the yield strength of the cell casing material is increased on the flat side walls (9) which are particularly subjected to the mechanical casing stress during the charging phase compared to the other casing walls, whereby in particular the elastic range in the stress-strain diagram required to compensate for the mechanical casing stress is increased, and that in particular the increased yield strength in the material of the flat side walls (9) is formed by embossed structures (17), and that in particular the embossed structures (17) are formed into the flat side walls (9) by work hardening the material, and / or that in particular the respective embossed structure (17) consists of a regular pattern of elevations (19) and depressions (20),and in particular that the embossed structures (17) on the contact surfaces of adjacent battery cells in the electrode / separator stack (15) are adapted such that a protrusion (19) of one embossed structure (17) protrudes positively into the depression (20) of the other embossed structures (17), and / or that in particular a compression pad arranged between adjacent battery cells has the respective embossed structure (17) in negative form on the contact surfaces to the battery cells. [2] Prismatic battery cell with a cell housing (1) in which an electrode / separator stack (15) is arranged, wherein the cell housing (1) is cuboid-shaped and the housing walls of which are divided into narrow side walls (7), flat side walls (9) and base and cover walls (3, 5), of which the flat side walls (9) delimit the electrode / separator stack (15) on both sides in the stacking direction, and wherein in a charging phase the volume of the electrode / separator stack (15) increases, in particular in the stacking direction, whereby the cell housing (1) is subjected to mechanical housing tension, characterized by in that in the flat side walls (9) which are particularly subjected to mechanical housing tension during the charging phase, the wall thickness (s) is increased by an allowance compared to the other housing walls, whereby in particular the compressive strength of the cell housing (1) at the flat side walls (9) is increased in order to increase the dimensional stability of the cell housing (1). [3] Prismatic battery cell according to claim 2, characterized by that the flat side walls (9) and the narrow side walls (7) of the cell housing (1) form a rolled sheet metal part (21) in development, that is to say a tailored rolled blank, in which the sheet metal sections (9') forming the flat side walls (9) have a greater wall thickness than the sheet metal sections (7') forming the narrow side walls (7), or that the flat and narrow side walls (7, 9) are components of a hollow continuous casting which is cut to length from an endless continuous casting profile. [4] Prismatic battery cell with a cell housing (1) in which an electrode / separator stack (15) is arranged, wherein the cell housing (1) is cuboid-shaped and the housing walls of which are divided into narrow side walls (7), flat side walls (9) and base and cover walls (3, 5), of which the flat side walls (9) delimit the electrode / separator stack (15) on both sides in the stacking direction, and wherein in a charging phase the volume of the electrode / separator stack (15) increases, in particular in the stacking direction, whereby the cell housing (1) is subjected to mechanical housing tension, characterized byin that, to support the cell housing dimensional stability, in particular during the charging phase, a winding material, in particular a winding wire (27), preferably aluminum wire, is wound around the cell housing (1) in a winding process, and / or in that, in particular, the winding material is wound spirally with a number of turns around the cell housing (1), or alternatively, the winding wire (27) consists of individual wires, each of which is laid in only one turn around the cell housing (1). [5] Prismatic battery cell according to claim 4, characterized bythat the winding material is a band or tape (29) made of fiber-reinforced, in particular carbon fiber-reinforced plastic, and that in particular the CFRP tape (29) is provided for the winding process as a prepreg pre-impregnated with matrix material, and that in particular after completion of the winding process the CFRP tape (29) is heated to above the melting temperature of the matrix material, building up its maximum tensile strength, whereby in particular a consolidation takes place in which the fibers are completely impregnated by the molten matrix material. [6] Prismatic battery cell with a cell housing (1) in which an electrode / separator stack (15) is arranged, wherein the cell housing (1) is cuboid-shaped and the housing walls of which are divided into narrow side walls (7), flat side walls (9) and base and cover walls (3, 5), of which the flat side walls (9) delimit the electrode / separator stack (15) on both sides in the stacking direction, and wherein in a charging phase the volume of the electrode / separator stack (15) increases, in particular in the stacking direction, whereby the cell housing (1) is subjected to mechanical housing tension, characterized by that the cell housing (1) is subjected to a material compaction in the still unpopulated state, i.e. before the electrode / separator stack (15) is inserted, in which the material of the cell housing (1) is compacted while increasing its tensile strength. [7] Prismatic battery cell according to claim 6, characterized bythat the material compaction takes place in a device with a hydraulic chamber (31) in which the cell housing (1) can be inserted, wherein the cell housing (1) is pressurized with hydraulic pressure (p H ), while inside the housing a counter bearing (33) rests against the housing walls (3, 7, 9). [8] Prismatic battery cell with a cell housing (1) in which an electrode / separator stack (15) is arranged, wherein the cell housing (1) is cuboid-shaped and the housing walls of which are divided into narrow side walls (7), flat side walls (9) and base and cover walls (3, 5), of which the flat side walls (9) delimit the electrode / separator stack (15) on both sides in the stacking direction, and wherein in a charging phase the volume of the electrode / separator stack (15) increases, in particular in the stacking direction, whereby the cell housing (1) is subjected to mechanical housing tension, characterized byin that, in order to support / increase the cell housing dimensional stability, in particular during the charging phase, the cell housing (1) is constructed from an outer housing (35) and an inner housing (37) which is inserted into the outer housing (35) to build up a mechanical counter-tension which counteracts the mechanical housing tension which builds up during the charging phase. [9] Prismatic battery cell according to claim 8, characterized by that the assembly of the inner housing (37) with the outer housing (35) is carried out by shrinking, in which the outer housing (35) is heated, then the inner housing (37) is inserted into the heated outer housing (35), and then the outer housing (35) is shrunk onto the inner housing (37) while cooling. [10] A method for producing a prismatic battery cell according to any one of the preceding claims.

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